I've got four WM5's that I plan to upgrade someday (probably upgrade two,
sell the others) and have sort of wondered what I would use as a preamp.
I've just come into a Heath SP-2 stereo preamp, and from some Google
research, it looks like this might be a good choice to upgrade and use with
the monoblocks. I will probably use all of this to drive some old Maggies I
still have. Anyway, what's the general feeling about this old preamp?

I also found a Heath WA-PL mono preamp and a PT-1 tuner. I'm not interested
in having these as part of the eventual tube system, so I'll need to get rid
of them. Are either one of these worth enough to try to sell or auction?

- Magnusfarce

Magnusfarce wrote:

I've got four WM5's that I plan to upgrade someday (probably upgrade two,
sell the others) and have sort of wondered what I would use as a preamp.
I've just come into a Heath SP-2 stereo preamp, and from some Google
research, it looks like this might be a good choice to upgrade and use with
the monoblocks. I will probably use all of this to drive some old Maggies I
still have. Anyway, what's the general feeling about this old preamp?

I also found a Heath WA-PL mono preamp and a PT-1 tuner. I'm not interested
in having these as part of the eventual tube system, so I'll need to get rid
of them. Are either one of these worth enough to try to sell or auction?

- Magnusfarce

The WM5's are worthy of a more modern preamp. A solid state unit would likely be
more neutral.. and allow the full spectrum of sound to get to the WM5's,
excluding noise, hum, distortion, etc. The RIAA networks would be more accurate
too. If you want to go tube, get something higher quality, and more modern.

The other old gear... well, it depends how much you value your time. Search
Ebay's completed auctions and you will find the prices similar models go for.

SS front end? uh uh... much, much better with tubes up front.

Your SP-2 will make a great preamp... be advised you should replace
all the caps with poly and mica. If it were me I'd likley replace
all the resistors too... most will be close to the old 10% tolerance,
but 2% resistors are really cheap and you'll be in there sodering
anyhow. Rebuilding the PEC modules might be a challenge, use
sheilded wire to keep the hum down.

Also.. take a good look at those 1m audio pots... the old volume and
tone pots im my heathkit aa-151 were all over 1.5m! Replacements can
be *really* expensive, but rest assured the $3 alphas from mouser are
at least as good as what are in it now.

I'd be tempted to get rid of the mag-phono level control, as you'll
likely have it full-open all the time anyhow, and bump down the other
signal trim-pots from 500K to 100K at least (to reduce noise). I
added a pair of 50K pots in my heathkit to trim down the CD player.
You might want to keep one of the AUX inputs high-impedance (500K) if
you plan to use a tube tuner, otherwise 33K will be enough for CD
or tape players.

You could try a tone-bypass circuit, but matching the bleed-to-ground
with your tone stack is a bit trial and error. I got close with my
amp, but chose not to bother when my ears couldn't honestly tell any
difference using it or not. I'm a big believer in trusting your
ears.

Finally, you might want to try running the pentode in triode-mode,
you'll loose a bit of gain, but the sound will be great.

Lots of soldering... but that's why we're here eh?!

Have fun!
EC

Max Holubitsky wrote in :



Magnusfarce wrote:

I've got four WM5's that I plan to upgrade someday (probably upgrade
two, sell the others) and have sort of wondered what I would use as a
preamp. I've just come into a Heath SP-2 stereo preamp, and from some
Google research, it looks like this might be a good choice to upgrade
and use with the monoblocks. I will probably use all of this to
drive some old Maggies I still have. Anyway, what's the general
feeling about this old preamp?

I also found a Heath WA-PL mono preamp and a PT-1 tuner. I'm not
interested in having these as part of the eventual tube system, so
I'll need to get rid of them. Are either one of these worth enough
to try to sell or auction?

- Magnusfarce

The WM5's are worthy of a more modern preamp. A solid state unit would
likely be more neutral.. and allow the full spectrum of sound to get
to the WM5's, excluding noise, hum, distortion, etc. The RIAA networks
would be more accurate too. If you want to go tube, get something
higher quality, and more modern.

The other old gear... well, it depends how much you value your time.
Search Ebay's completed auctions and you will find the prices similar
models go for.

Hey,

You think so? I would think a good SS preamp would sound far better than an
old tube unit where the parts values have drifted... especially when there
is no overall NFB, the RIAA network is approximate at best, and there's tone
controls to mess up the overall frequency response. Not even to mention the
pots that may not have matched sections, and are likely worn out. Even if
the SP-2 was brand new, and in perfect condition, I seriously doubt it could
compete performance wise with a decent SS preamp which could be purchaced
for less than the cost of new tubes, and capacitors for the old Heathkit.

The WM-5's are a different matter altogether... to me nothing beats the
sound of a 6L6 based amplifier, with good output iron.

For CD listening only, a passive "preamp" with a high quality pot or
attenuator would probably be a more neutral device.

One thing which I am also curious about, is what model of maggies will this
system be used with? I have a pair of MGIIb's, and they are very
insensitive... 25W would be hard pressed to get them going. The WM5's might
be better suited to more sensitive speakers.

Max

EC wrote:

SS front end? uh uh... much, much better with tubes up front.

Your SP-2 will make a great preamp... be advised you should replace
all the caps with poly and mica. If it were me I'd likley replace
all the resistors too... most will be close to the old 10% tolerance,
but 2% resistors are really cheap and you'll be in there sodering
anyhow. Rebuilding the PEC modules might be a challenge, use
sheilded wire to keep the hum down.

Also.. take a good look at those 1m audio pots... the old volume and
tone pots im my heathkit aa-151 were all over 1.5m! Replacements can
be *really* expensive, but rest assured the $3 alphas from mouser are
at least as good as what are in it now.

I'd be tempted to get rid of the mag-phono level control, as you'll
likely have it full-open all the time anyhow, and bump down the other
signal trim-pots from 500K to 100K at least (to reduce noise). I
added a pair of 50K pots in my heathkit to trim down the CD player.
You might want to keep one of the AUX inputs high-impedance (500K) if
you plan to use a tube tuner, otherwise 33K will be enough for CD
or tape players.

You could try a tone-bypass circuit, but matching the bleed-to-ground
with your tone stack is a bit trial and error. I got close with my
amp, but chose not to bother when my ears couldn't honestly tell any
difference using it or not. I'm a big believer in trusting your
ears.

Finally, you might want to try running the pentode in triode-mode,
you'll loose a bit of gain, but the sound will be great.

Lots of soldering... but that's why we're here eh?!

Have fun!
EC

Max Holubitsky wrote in :



Magnusfarce wrote:

I've got four WM5's that I plan to upgrade someday (probably upgrade
two, sell the others) and have sort of wondered what I would use as a
preamp. I've just come into a Heath SP-2 stereo preamp, and from some
Google research, it looks like this might be a good choice to upgrade
and use with the monoblocks. I will probably use all of this to
drive some old Maggies I still have. Anyway, what's the general
feeling about this old preamp?

I also found a Heath WA-PL mono preamp and a PT-1 tuner. I'm not
interested in having these as part of the eventual tube system, so
I'll need to get rid of them. Are either one of these worth enough
to try to sell or auction?

- Magnusfarce

The WM5's are worthy of a more modern preamp. A solid state unit would
likely be more neutral.. and allow the full spectrum of sound to get
to the WM5's, excluding noise, hum, distortion, etc. The RIAA networks
would be more accurate too. If you want to go tube, get something
higher quality, and more modern.

The other old gear... well, it depends how much you value your time.
Search Ebay's completed auctions and you will find the prices similar
models go for.

I'd agree.. most CD players kick out enough V that a simple passive
volume / tone-stack might be best.

I know you'll get a lot of opinion for whether the "tube sound" comes
most from the pre-amp or power-amp, but I lean towards the pre- side
of things. The power tubes do look WAY MORE COOL in the dark though!

I IS ironic that I'm throwing away most of what my SS CD player puts
out so I can use the tube pre-amp in my Heathkit.. so it goes.

I think the SP-2 has separate pots for input signal, maybe some
dual-gang pots once things have been amplified up a bit (where a bit
of un-matchedness won't matter as much).

EC wrote:

I'd agree.. most CD players kick out enough V that a simple passive
volume / tone-stack might be best.

I know you'll get a lot of opinion for whether the "tube sound" comes
most from the pre-amp or power-amp, but I lean towards the pre- side
of things. The power tubes do look WAY MORE COOL in the dark though!

I IS ironic that I'm throwing away most of what my SS CD player puts
out so I can use the tube pre-amp in my Heathkit.. so it goes.

I think the SP-2 has separate pots for input signal, maybe some
dual-gang pots once things have been amplified up a bit (where a bit
of un-matchedness won't matter as much).

Hey,

In my experience, the tube power amplifier makes a bigger difference,
because of a number of reasons, which I will attempt to describe.

1. The amplifier/speaker interface is quite different, because an output
transformer is used, rather than a typical solid state power amplifier,
which is directly coupled to the speaker, and has a very low output
impedance. This can result in noticible frequency response anomalies while
using a tube amp, which may or may not be desierable.

2. The tube power amplifier, if of a good design, tends towards a "soft
clipping" behaviour, which is very different from most transistor
amplifiers.

3. The tube power amplifier, will likely have very low small signal
distortion, and not have high order distortion products like a solid state
amplifier does - actually this is quite related to point 2 if you think in
terms of Fourier analysis.

Now, the tube vs solid state preamplifiers, are a different matter. My
attempt to describe those differences, is as follows.

1. Tube preamplifiers, especially vintage ones, do not always use negative
feedback, and can have higher THD than a comparable solid state amplifier
by several orders of magnitude. This distortion may appear to improve the
sound quality, in psychoacoustic ways which I do not have the
qualifications to understand or describe.

2.High output impedance of some tube preamplifiers, in combination with
shielded interconnects may result in rolled off high frequencies.

3. Tubes are more noisy for phono preamps, must be carefully selected, and
may have problems with hum pickup and/or microphonics. Generally the S/N
ratio of a tube phono preamp will not be great unless it is very very
carefully designed.

4. Any vintage preamp with a tone control setup will be very hard to set
in the "flat" position without actually wiring a bypass, or, using
measuring equipment. If one looks at the specs for a vintage preamp, quite
often they are nowhere near as good as the specs for a contemporary (for
the era) power amplifier. I'm not sure why this is - maybe it was a
marketing thing, at the time.

5. RIAA networks in newer preamps are a lot more accurate than the old
standard single 12AX7 phono preamp.

6. The "soft clipping" advantage of tubes is lost in a preamp, because a
preamp is not usually driven into overload.

Of course, these are just my interpretation of the facts, so I am posting
them as opinions rather than facts, and of course am always open to
discussion.

Max

"Max Holubitsky" wrote in message
...
:
:
: EC wrote:
:
: I'd agree.. most CD players kick out enough V that a simple passive
: volume / tone-stack might be best.
:
: I know you'll get a lot of opinion for whether the "tube sound" comes
: most from the pre-amp or power-amp, but I lean towards the pre- side
: of things. The power tubes do look WAY MORE COOL in the dark though!
:
: I IS ironic that I'm throwing away most of what my SS CD player puts
: out so I can use the tube pre-amp in my Heathkit.. so it goes.
:
: I think the SP-2 has separate pots for input signal, maybe some
: dual-gang pots once things have been amplified up a bit (where a bit
: of un-matchedness won't matter as much).
:
: Hey,
:
: In my experience, the tube power amplifier makes a bigger difference,
: because of a number of reasons, which I will attempt to describe.
:
: 1. The amplifier/speaker interface is quite different, because an output
: transformer is used, rather than a typical solid state power amplifier,
: which is directly coupled to the speaker, and has a very low output
: impedance. This can result in noticible frequency response anomalies while
: using a tube amp, which may or may not be desierable.
:
: 2. The tube power amplifier, if of a good design, tends towards a "soft
: clipping" behaviour, which is very different from most transistor
: amplifiers.
:
: 3. The tube power amplifier, will likely have very low small signal
: distortion, and not have high order distortion products like a solid state
: amplifier does - actually this is quite related to point 2 if you think in
: terms of Fourier analysis.
:
: Now, the tube vs solid state preamplifiers, are a different matter. My
: attempt to describe those differences, is as follows.
:
: 1. Tube preamplifiers, especially vintage ones, do not always use negative
: feedback, and can have higher THD than a comparable solid state amplifier
: by several orders of magnitude. This distortion may appear to improve the
: sound quality, in psychoacoustic ways which I do not have the
: qualifications to understand or describe.
:
: 2.High output impedance of some tube preamplifiers, in combination with
: shielded interconnects may result in rolled off high frequencies.
:
: 3. Tubes are more noisy for phono preamps, must be carefully selected, and
: may have problems with hum pickup and/or microphonics. Generally the S/N
: ratio of a tube phono preamp will not be great unless it is very very
: carefully designed.
:
: 4. Any vintage preamp with a tone control setup will be very hard to set
: in the "flat" position without actually wiring a bypass, or, using
: measuring equipment. If one looks at the specs for a vintage preamp, quite
: often they are nowhere near as good as the specs for a contemporary (for
: the era) power amplifier. I'm not sure why this is - maybe it was a
: marketing thing, at the time.
:
: 5. RIAA networks in newer preamps are a lot more accurate than the old
: standard single 12AX7 phono preamp.
:
: 6. The "soft clipping" advantage of tubes is lost in a preamp, because a
: preamp is not usually driven into overload.
:
: Of course, these are just my interpretation of the facts, so I am posting
: them as opinions rather than facts, and of course am always open to
: discussion.
:
: Max

I think you've put it quite nicely, there. Here for some cognitive angle
on things to add:
First, there is no standard perception of something as complex as a
(reproduced) acoustical musical signal. As an example, in Helmholt'z
book "On the sensations of tone" he describes experiments with a
concert first violinist who could easily differentiate between a
17th upper partial (the more ad-lib translation of his term for harmonic)
being there or not !
Yet, i've had the occasion with some older folks, when confronted
with a pop-recording, couldn't for the life of them separate out the
base-drum sound from the baseguitar ( and, no, the sound system
wasn't *that* bad

Perception is an active and adaptable, both short-term and through
continuous exposing to stimuli function, not at all a static data-
processing hardware & software setup. Those that like to think in
terms of evolution would add, it's very reasonable to assume
that the way our most dominant senses are put to use are for
survival. And that means picking out the unusual with uncanny
precision at times, largely ignoring things at other occasions
on a -here and now- basis.

Rudy
:

Thanks to everyone for the comments so far. While I'm looking forward to
doing the upgrade work on the W5's, I'm not nearly as excited about doing so
for the preamp, so unless there is a clear consensus that this preamp is the
ideal match to the power amps, then I'm probably going to let it slide.
I've had thees amps for five years and haven't gotten close to working on
them yet, so adding the preamp to the pile doesn't help.

I should mention that I have not done anything with tubes ever before, and
as such am not necessarily a true believer in their superiority. However,
this seems like a great way to perhaps enter that world and begin to see
what its about. I was relieved to read that it's not silly to plan to use
this system to play CD's because I got rid of almost all my LP's years ago.
However, my CD collection is quite large and I have many classical and
audiophile disks.

My main system is not much but not entirely bad, either. I use the HK
HD7600II CD player that had some nice things said about it a long time ago.
This drives a Sumo Athena preamp and an Adcom GFA 555II, which powers my
Mirage M3's. I biamp through a Sampson Delilah crossover to my handbuilt
Leach DBA monoblock, driven by homemade JBL B380 (?) subwoofer. That Leach
amp is the one featured in Audio in the early 80's and is a real monster.
Not only is it immensely powerful (two half-kv isolation tranformers to
power the rails), but when I completed it several years ago, I A-B'd it
against the Adcom and couldn't really hear any difference. Anyway, that's
what I listen to. I went through all this so that any further advice would
be aimed more accurately at my experience level and interests.

BTW, the Maggies I spoke of are an old pair of II's. I know the Heathkits
can't dump a lot of current, but I figured this little system would be used
for relatively tame music listening. You know, more Mozart than Metallica.
Thanks again for the help. Anyone interested in buying an SP-2?

- Magnusfarce






"Max Holubitsky" wrote in message
...
Hey,

You think so? I would think a good SS preamp would sound far better than
an
old tube unit where the parts values have drifted... especially when there
is no overall NFB, the RIAA network is approximate at best, and there's
tone
controls to mess up the overall frequency response. Not even to mention
the
pots that may not have matched sections, and are likely worn out. Even if
the SP-2 was brand new, and in perfect condition, I seriously doubt it
could
compete performance wise with a decent SS preamp which could be purchaced
for less than the cost of new tubes, and capacitors for the old Heathkit.

The WM-5's are a different matter altogether... to me nothing beats the
sound of a 6L6 based amplifier, with good output iron.

For CD listening only, a passive "preamp" with a high quality pot or
attenuator would probably be a more neutral device.

One thing which I am also curious about, is what model of maggies will
this
system be used with? I have a pair of MGIIb's, and they are very
insensitive... 25W would be hard pressed to get them going. The WM5's
might
be better suited to more sensitive speakers.

Max

EC wrote:

SS front end? uh uh... much, much better with tubes up front.

Your SP-2 will make a great preamp... be advised you should replace
all the caps with poly and mica. If it were me I'd likley replace
all the resistors too... most will be close to the old 10% tolerance,
but 2% resistors are really cheap and you'll be in there sodering
anyhow. Rebuilding the PEC modules might be a challenge, use
sheilded wire to keep the hum down.

Also.. take a good look at those 1m audio pots... the old volume and
tone pots im my heathkit aa-151 were all over 1.5m! Replacements can
be *really* expensive, but rest assured the $3 alphas from mouser are
at least as good as what are in it now.

I'd be tempted to get rid of the mag-phono level control, as you'll
likely have it full-open all the time anyhow, and bump down the other
signal trim-pots from 500K to 100K at least (to reduce noise). I
added a pair of 50K pots in my heathkit to trim down the CD player.
You might want to keep one of the AUX inputs high-impedance (500K) if
you plan to use a tube tuner, otherwise 33K will be enough for CD
or tape players.

You could try a tone-bypass circuit, but matching the bleed-to-ground
with your tone stack is a bit trial and error. I got close with my
amp, but chose not to bother when my ears couldn't honestly tell any
difference using it or not. I'm a big believer in trusting your
ears.

Finally, you might want to try running the pentode in triode-mode,
you'll loose a bit of gain, but the sound will be great.

Lots of soldering... but that's why we're here eh?!

Have fun!
EC

Max Holubitsky wrote in :



Magnusfarce wrote:

I've got four WM5's that I plan to upgrade someday (probably upgrade
two, sell the others) and have sort of wondered what I would use as a
preamp. I've just come into a Heath SP-2 stereo preamp, and from some
Google research, it looks like this might be a good choice to upgrade
and use with the monoblocks. I will probably use all of this to
drive some old Maggies I still have. Anyway, what's the general
feeling about this old preamp?

I also found a Heath WA-PL mono preamp and a PT-1 tuner. I'm not
interested in having these as part of the eventual tube system, so
I'll need to get rid of them. Are either one of these worth enough
to try to sell or auction?

- Magnusfarce

The WM5's are worthy of a more modern preamp. A solid state unit would
likely be more neutral.. and allow the full spectrum of sound to get
to the WM5's, excluding noise, hum, distortion, etc. The RIAA networks
would be more accurate too. If you want to go tube, get something
higher quality, and more modern.

The other old gear... well, it depends how much you value your time.
Search Ebay's completed auctions and you will find the prices similar
models go for.

I think you've put it quite nicely, there. Here for some cognitive angle
on things to add:
First, there is no standard perception of something as complex as a
(reproduced) acoustical musical signal. As an example, in Helmholt'z
book "On the sensations of tone" he describes experiments with a
concert first violinist who could easily differentiate between a
17th upper partial (the more ad-lib translation of his term for harmonic)
being there or not !
Yet, i've had the occasion with some older folks, when confronted
with a pop-recording, couldn't for the life of them separate out the
base-drum sound from the baseguitar ( and, no, the sound system
wasn't *that* bad

Perception is an active and adaptable, both short-term and through
continuous exposing to stimuli function, not at all a static data-
processing hardware & software setup. Those that like to think in
terms of evolution would add, it's very reasonable to assume
that the way our most dominant senses are put to use are for
survival. And that means picking out the unusual with uncanny
precision at times, largely ignoring things at other occasions
on a -here and now- basis.

Rudy
:

Hello Rudy,

This is a very interesting topic - you have approached the same subject as
myself, but from a completely different perspective. My background is electrical
engineering, and although it's possible to try to quantify the bennifits of tube
amplification by technical means alone (as I have tried to), in the end it
becomes a rather weak argument.

The technical argument I gave in my previous posting is largely justification
for the fact that I prefer the sound of a stereo system with tube power
amplifiers, but consider tube preamplifiers a nuisance, because they comprimise
reliablility, are expensive, and I don't find that they improve the sound of my
hi-fi system. I find a decent solid state pre-amp more neutral than a tube
pre-amp.

My own interpretation of the issue, is the reason why I like the sound of tube
amplifiers has more to do with the speaker/output transformer/output tube
combination and interaction, than any other part of the amplification system.

Max

Thanks to everyone for the comments so far. While I'm looking forward to
doing the upgrade work on the W5's, I'm not nearly as excited about doing so
for the preamp, so unless there is a clear consensus that this preamp is the
ideal match to the power amps, then I'm probably going to let it slide.
I've had thees amps for five years and haven't gotten close to working on
them yet, so adding the preamp to the pile doesn't help.

Tube equipment is fairly easy to work on, and it's a lot of fun - especially
power amplifiers. Even if you don't end up falling in love with them, it's a fun
project, and you won't lose money on classics like the WM5s. Try to get ahold of
some original heathkit manuals before proceeding to make life easier, if you're
not used to working on tube equipment. Antique electronics supply is a good
source for parts, and my personal favourite 6L6s these days are either the Tesla
6L6GC, or the Chinese 6L6GC STR - you can get these at any guitar store. Buy
matched pairs, don't mess around with single 6L6's, and if one goes bad, always
change the pair. I wouldn't change just one spark plug, and I wouldn't change
just one output tube. The single ones left over from when one of a pair is bad
make good emergency replacments, to tide you over until you get another matched
pair.

I should mention that I have not done anything with tubes ever before, and
as such am not necessarily a true believer in their superiority. However,
this seems like a great way to perhaps enter that world and begin to see
what its about. I was relieved to read that it's not silly to plan to use
this system to play CD's because I got rid of almost all my LP's years ago.
However, my CD collection is quite large and I have many classical and
audiophile disks.


I listen to CDs though a tube system all the time. Don't approach it with the
attitude that you have to become a believer, approach it as a hobbiest trying
out something new. Even if you don't like it more than your current setup, you
will be shocked at how good 50 year old amplifiers can sound.


My main system is not much but not entirely bad, either. I use the HK
HD7600II CD player that had some nice things said about it a long time ago.
This drives a Sumo Athena preamp and an Adcom GFA 555II, which powers my
Mirage M3's. I biamp through a Sampson Delilah crossover to my handbuilt
Leach DBA monoblock, driven by homemade JBL B380 (?) subwoofer. That Leach
amp is the one featured in Audio in the early 80's and is a real monster.
Not only is it immensely powerful (two half-kv isolation tranformers to
power the rails), but when I completed it several years ago, I A-B'd it
against the Adcom and couldn't really hear any difference. Anyway, that's
what I listen to. I went through all this so that any further advice would
be aimed more accurately at my experience level and interests.


This sounds like a cool system!


BTW, the Maggies I spoke of are an old pair of II's. I know the Heathkits
can't dump a lot of current, but I figured this little system would be used
for relatively tame music listening. You know, more Mozart than Metallica.
Thanks again for the help. Anyone interested in buying an SP-2?

Just for kicks, install the WM5s in your good system once you fix them up... try
them with SUMO preamp, H-K CD player, and the Mirage speakers. MG-IIs are okay,
but having some real tweeters wouldn't hurt anything at all, and I think you
will see the WM5s shine on this system, as the Mirage's will be more sensitive
than the Maggies by far. Try it with a wide variety of music, different times of
day, and when you're in different moods. The same system that sounds horrible on
a saturday afternoon while you're trying to blast the 1812 overature may sound
just amazing at night, when you're playing something more tame. Just a hunch,
but it may be the Adcom which ends up in the basement, driving the MG-IIs.

P.S. don't mess around with the old tubes... replace all of them, and keep the
old ones as emergency spares and for if you ever sell the amps. I replace all of
the tubes in my amplifiers once every 18 months of hard use... even if they're
not bad. It keeps failures down, and performance up - Mind you, I am the type of
person who will go out of my way to make sure to change my car's oil at 3000
mile intervals.

P.P.S. Replace all capacitors... the cheap yellow antique electronic supply one
will do fine to get you off the ground. I'd replace all the electrolytics with
new axial lead caps the closest value you you can find, but on the high side.
Make sure that the replacement capacitors are secured mechanically if need be,
and insulate the leads with insulation stripped off of bell wire, to minimize
the potential for future problems. The value of electrolytics is not critical,
as the old caps often had a -20 +100 % tolerance. Make sure all the replacement
caps have a high enough voltage rating.

"Max Holubitsky" wrote in message
...
:
: Hello Rudy,
:
: This is a very interesting topic - you have approached the same subject as
: myself, but from a completely different perspective. My background is
electrical
: engineering, and although it's possible to try to quantify the bennifits
of tube
: amplification by technical means alone (as I have tried to), in the end it
: becomes a rather weak argument.
:
: The technical argument I gave in my previous posting is largely
justification
: for the fact that I prefer the sound of a stereo system with tube power
: amplifiers, but consider tube preamplifiers a nuisance, because they
comprimise
: reliablility, are expensive, and I don't find that they improve the sound
of my
: hi-fi system. I find a decent solid state pre-amp more neutral than a tube
: pre-amp.
:
: My own interpretation of the issue, is the reason why I like the sound of
tube
: amplifiers has more to do with the speaker/output transformer/output tube
: combination and interaction, than any other part of the amplification
system.
:
: Max
:
That's cool. The 'best' system at any moment is the one that's available
that you can afford, had the time to research and bring together
that you changed today that gloweth so lovely in the dark
that gives you satisfaction and
maybe now and
then
some magic .

But then, there's always the 'danger' of having a listen at a friends place
refining the cognitive abilities
ok, modding your setup again
don't you love it ?
:-)
Rudy

I'm currently using a SS preamp (preamp part of Sansui AU7900) with a
tube power amp(either 6V6 PP,or ST-70.),and I like the combo.It sounds
better to me than my modified PAS-3.
I'd agree that theres something different with tube power amps.
I think the difference is that most SS amps act as a voltage source
(high voltage swing),whereas tube amps (intristicaly) act like a
current source,because of the OPT."Normal" (ie,voicecoil-ring
magnet-type.)speakers are more current driven devices..(Just my
theory.) Quads,Maggies,etc may be different.I know most Maggies are a
fairly nice resistive load.Pretty easy on an amp.I have driven (ohh,I
forget, MGII's??) with the 10Wpc 6V6 PP amp mentioned above,and it
worked pretty nicely,sounded pretty good too. (I'm a sucker for
Maggies!) The Sansui above worked great,plenty of power(A conservative
IMHO,80Wpc rating.)to rock the house. (But GOT forgive me,it's SS!)

I think your tube preamp would be worth a little work to get it
operating nicely again.You can probably sell/trade it for something
else later if you don't like it.
I'm sure there are plenty of good SS preamps aswell.
(*ducking lightning,and B+*)



Max Holubitsky wrote in message ...
EC wrote:

I'd agree.. most CD players kick out enough V that a simple passive
volume / tone-stack might be best.

I know you'll get a lot of opinion for whether the "tube sound" comes
most from the pre-amp or power-amp, but I lean towards the pre- side
of things. The power tubes do look WAY MORE COOL in the dark though!

I IS ironic that I'm throwing away most of what my SS CD player puts
out so I can use the tube pre-amp in my Heathkit.. so it goes.

I think the SP-2 has separate pots for input signal, maybe some
dual-gang pots once things have been amplified up a bit (where a bit
of un-matchedness won't matter as much).

Hey,

In my experience, the tube power amplifier makes a bigger difference,
because of a number of reasons, which I will attempt to describe.

1. The amplifier/speaker interface is quite different, because an output
transformer is used, rather than a typical solid state power amplifier,
which is directly coupled to the speaker, and has a very low output
impedance. This can result in noticible frequency response anomalies while
using a tube amp, which may or may not be desierable.

2. The tube power amplifier, if of a good design, tends towards a "soft
clipping" behaviour, which is very different from most transistor
amplifiers.

3. The tube power amplifier, will likely have very low small signal
distortion, and not have high order distortion products like a solid state
amplifier does - actually this is quite related to point 2 if you think in
terms of Fourier analysis.

Now, the tube vs solid state preamplifiers, are a different matter. My
attempt to describe those differences, is as follows.

1. Tube preamplifiers, especially vintage ones, do not always use negative
feedback, and can have higher THD than a comparable solid state amplifier
by several orders of magnitude. This distortion may appear to improve the
sound quality, in psychoacoustic ways which I do not have the
qualifications to understand or describe.

2.High output impedance of some tube preamplifiers, in combination with
shielded interconnects may result in rolled off high frequencies.

3. Tubes are more noisy for phono preamps, must be carefully selected, and
may have problems with hum pickup and/or microphonics. Generally the S/N
ratio of a tube phono preamp will not be great unless it is very very
carefully designed.

4. Any vintage preamp with a tone control setup will be very hard to set
in the "flat" position without actually wiring a bypass, or, using
measuring equipment. If one looks at the specs for a vintage preamp, quite
often they are nowhere near as good as the specs for a contemporary (for
the era) power amplifier. I'm not sure why this is - maybe it was a
marketing thing, at the time.

5. RIAA networks in newer preamps are a lot more accurate than the old
standard single 12AX7 phono preamp.

6. The "soft clipping" advantage of tubes is lost in a preamp, because a
preamp is not usually driven into overload.

Of course, these are just my interpretation of the facts, so I am posting
them as opinions rather than facts, and of course am always open to
discussion.

Max

Thanks for the kind and helpful words, expecially about my little system.
It pales compared to some of the stuff I see and hear about, but I like it
and think it represents very good sound for the money.

I pretty much think I'll pass on the Heath preamp and probably go with
something passive when the time comes. Would the front end of an old NAD
3020 be any good? I know the power amp section is still considered pretty
good for a lower end, lower power amp. Is the preamp section worth
considering?

Anyway, I am looking forward to working on the W5's. I've been handy with a
soldering iron for about three and a half decades now, so I don't expect any
major problems. The Leach amp was great fun to build. If I get into tubes,
I guess I'll have to learn to respect the B+ a little more than I do the +/-
5vdc I use for my little digital projects.

Your ideas about parts replacement will come in handy. When I first got the
amps I got busy and obtained an original manual, and also started lurking
around this group and Google watching for ideas on resistors, caps, and
especially tubes. Years ago I was fairly up to speed on most of the very
high end Wonder Cap-type stuff, but I don't really want to go that far with
these amps. Do you know if there's some sort of cookbook list for
recommended replacement parts for a mid-level upgrade for these units? I'd
like to get past a lot of the guesswork (and arguments) and start acquiring
parts soon. Somewhere quite a while back I saw an upgrade kit offered for
$80, but I've no idea what was in it. Aside from tubes, I don't see the
caps and resistors being terribly expensive. In any case, any specific
recommendations you have for component upgrades would be appreciated.

- Magnusfarce


P.S. Know of any good articles, etc., on general upgrading of old tube
amps?



"Max Holubitsky" wrote in message
...
Thanks to everyone for the comments so far. While I'm looking forward
to
doing the upgrade work on the W5's, I'm not nearly as excited about
doing so
for the preamp, so unless there is a clear consensus that this preamp is
the
ideal match to the power amps, then I'm probably going to let it slide.
I've had thees amps for five years and haven't gotten close to working
on
them yet, so adding the preamp to the pile doesn't help.

Tube equipment is fairly easy to work on, and it's a lot of fun -
especially
power amplifiers. Even if you don't end up falling in love with them, it's
a fun
project, and you won't lose money on classics like the WM5s. Try to get
ahold of
some original heathkit manuals before proceeding to make life easier, if
you're
not used to working on tube equipment. Antique electronics supply is a
good
source for parts, and my personal favourite 6L6s these days are either the
Tesla
6L6GC, or the Chinese 6L6GC STR - you can get these at any guitar store.
Buy
matched pairs, don't mess around with single 6L6's, and if one goes bad,
always
change the pair. I wouldn't change just one spark plug, and I wouldn't
change
just one output tube. The single ones left over from when one of a pair is
bad
make good emergency replacments, to tide you over until you get another
matched
pair.

I should mention that I have not done anything with tubes ever before,
and
as such am not necessarily a true believer in their superiority.
However,
this seems like a great way to perhaps enter that world and begin to see
what its about. I was relieved to read that it's not silly to plan to
use
this system to play CD's because I got rid of almost all my LP's years
ago.
However, my CD collection is quite large and I have many classical and
audiophile disks.


I listen to CDs though a tube system all the time. Don't approach it with
the
attitude that you have to become a believer, approach it as a hobbiest
trying
out something new. Even if you don't like it more than your current setup,
you
will be shocked at how good 50 year old amplifiers can sound.


My main system is not much but not entirely bad, either. I use the HK
HD7600II CD player that had some nice things said about it a long time
ago.
This drives a Sumo Athena preamp and an Adcom GFA 555II, which powers my
Mirage M3's. I biamp through a Sampson Delilah crossover to my
handbuilt
Leach DBA monoblock, driven by homemade JBL B380 (?) subwoofer. That
Leach
amp is the one featured in Audio in the early 80's and is a real
monster.
Not only is it immensely powerful (two half-kv isolation tranformers to
power the rails), but when I completed it several years ago, I A-B'd it
against the Adcom and couldn't really hear any difference. Anyway,
that's
what I listen to. I went through all this so that any further advice
would
be aimed more accurately at my experience level and interests.


This sounds like a cool system!


BTW, the Maggies I spoke of are an old pair of II's. I know the
Heathkits
can't dump a lot of current, but I figured this little system would be
used
for relatively tame music listening. You know, more Mozart than
Metallica.
Thanks again for the help. Anyone interested in buying an SP-2?

Just for kicks, install the WM5s in your good system once you fix them
up... try
them with SUMO preamp, H-K CD player, and the Mirage speakers. MG-IIs are
okay,
but having some real tweeters wouldn't hurt anything at all, and I think
you
will see the WM5s shine on this system, as the Mirage's will be more
sensitive
than the Maggies by far. Try it with a wide variety of music, different
times of
day, and when you're in different moods. The same system that sounds
horrible on
a saturday afternoon while you're trying to blast the 1812 overature may
sound
just amazing at night, when you're playing something more tame. Just a
hunch,
but it may be the Adcom which ends up in the basement, driving the MG-IIs.

P.S. don't mess around with the old tubes... replace all of them, and keep
the
old ones as emergency spares and for if you ever sell the amps. I replace
all of
the tubes in my amplifiers once every 18 months of hard use... even if
they're
not bad. It keeps failures down, and performance up - Mind you, I am the
type of
person who will go out of my way to make sure to change my car's oil at
3000
mile intervals.

P.P.S. Replace all capacitors... the cheap yellow antique electronic
supply one
will do fine to get you off the ground. I'd replace all the electrolytics
with
new axial lead caps the closest value you you can find, but on the high
side.
Make sure that the replacement capacitors are secured mechanically if need
be,
and insulate the leads with insulation stripped off of bell wire, to
minimize
the potential for future problems. The value of electrolytics is not
critical,
as the old caps often had a -20 +100 % tolerance. Make sure all the
replacement
caps have a high enough voltage rating.

P.S. Know of any good articles, etc., on general upgrading of old tube
amps?

1) Tu-be or not Tube (book)
2) FisherDoc RestoPaks

Thanks for the kind and helpful words, expecially about my little system.
It pales compared to some of the stuff I see and hear about, but I like it
and think it represents very good sound for the money.

I've listened to some pretty "high end" stuff, and come to the conclusion that
once a certain level of performance is reached, personal preferance dominates
everything, and a lot of what is out there is grossly overpriced. I once demoed
some $3000 Totem tower speakers, and the woofers kept bottoming out on every
loud bass passage.... the salesman assured me people waited for 3 hours to hear
these speakers at some hi-fi show, and that it's normal for speakers to do that,
and implied I'm an idiot for thinking otherwise. Needless to say I walked out
and never came back. This wasn't me pushing the speakers either, it was the
saleman's demo CD, playing at the level he selected.


I pretty much think I'll pass on the Heath preamp and probably go with
something passive when the time comes. Would the front end of an old NAD
3020 be any good? I know the power amp section is still considered pretty
good for a lower end, lower power amp. Is the preamp section worth
considering?

No direct experience with this unit... but try the SUMO, then try the NAD, and
see if the difference bothers you. If the NAD sounds significantly worse, you've
got your answer.

Anyway, I am looking forward to working on the W5's. I've been handy with a
soldering iron for about three and a half decades now, so I don't expect any
major problems. The Leach amp was great fun to build. If I get into tubes,
I guess I'll have to learn to respect the B+ a little more than I do the +/-
5vdc I use for my little digital projects.

Digital is fun too, but tube stuff is so much more friendly to work on.... mind
you, I never was one for programming.

Your ideas about parts replacement will come in handy. When I first got the
amps I got busy and obtained an original manual, and also started lurking
around this group and Google watching for ideas on resistors, caps, and
especially tubes. Years ago I was fairly up to speed on most of the very
high end Wonder Cap-type stuff, but I don't really want to go that far with
these amps. Do you know if there's some sort of cookbook list for
recommended replacement parts for a mid-level upgrade for these units? I'd
like to get past a lot of the guesswork (and arguments) and start acquiring
parts soon. Somewhere quite a while back I saw an upgrade kit offered for
$80, but I've no idea what was in it. Aside from tubes, I don't see the
caps and resistors being terribly expensive. In any case, any specific
recommendations you have for component upgrades would be appreciated.

My opinion on components, which is just as a hobbiest, is use plastic film
capacitors and metal film resistors, of the cheapest variety you can find which
will do the trick. I like 1% resistors, because if you can have 1% for $0.01,
then why not. For power resistors, the generic ceramic rectangular ones will do
the trick nicely.

For electrolytics, if you want to do a **quality** job - go Sprague or Mallory
for the high voltage ones. If you just want to get the job done, use the
generic brand. Generic low voltage electrolytics are all you need.

My procedure for working on vintage gear, such as your Heathkits, is to replace
all the paper and electrolytic capacitors, but only the resistors which actually
measure off tolerence. An exception to this in your amplifier *might* be the
anode and cathode resistors on the phase splitter section of the first 12AU7 -
these should be matched as closely as you can possibly do it, and 1% resistors
would be nice here. I wouldn't be suprised if you could get away with not
replacing any resistors at all. I only replace paper and electrolytic
capacitors, and leave ceramic and mica and oil ones alone.

Above chassis mounted electolytic capacitors can stay in place, for cosmetics,
but what I do is solder a termnial strip to the lugs of the original capacitor,
and use it to mount the new axial lead capacitors underneath. This is an easy
process, and will save you time, and preserve the look of the amp. If the
terminal strip's mounting hole dosen't seem to fit well, what I do is drill it
bigger, then crip the lugs of the electolytic can so they fit in the hole...
then solder it with lots of extra solder, and it will hold nicely.

Once you have re-capped the amps, and put fresh tubes in, you'll have a starting
point, and the amps will at least meet design spec and not start smoking. If you
decide you like the amplifiers, you can later "upgrade" to expensive capacitors,
and see if you like them or not. I can't hear the difference between a plastic
film capacitor, and a paper capacitor, or a paper in oil capacitor - but there
are others who apparently can, so your milage may vary.

Just one additional bit of advice... if you want to fast track the whole
project... write a list of everything you need to buy, go to
www.tubesandmore.com, and order all the parts and tubes, plus a package of
terminal strips, just in case. I've been ordering from them since I got a
catalogue from a magazine ad in '93 and have always had good service. This will
get you everything you need in one shot, and bring it to your door in a week or
two. It's very nice to eliminate the annoying parts search phase from a project,
and will turn this project from weeks of delay and procrastination, into a half
hour on the computer, a 2 week wait, and a couple weekend afternoons of light
work.

I am very interested to hear the results of this project - namely what the WM5's
+ SUMO + HK + Mirage sounds like - try it with, and without the subwoofer, too.

"Magnusfarce" wrote in message hlink.net...



I should mention that I have not done anything with tubes ever before, and
as such am not necessarily a true believer in their superiority.


Oh My,re-cap those W5's and get them in good working order! You'll see
what all the fuss is about.



However,
this seems like a great way to perhaps enter that world and begin to see
what its about. I was relieved to read that it's not silly to plan to use
this system to play CD's because I got rid of almost all my LP's years ago.
However, my CD collection is quite large and I have many classical and
audiophile disks.

Repairing those amps would be a great way to get into tubes! Curiosity
bit me,and I rebuilt the old 6V6 amp and got hooked.But,I gotta warn
ya,It can become an obsession/addiction!
Why would playing CD's be silly? I mostly play MP3's,and the
occasional CD,since the radio isn't worth listening to anymore.

THE top authority on tube amps & restoration is Vacuum Tube Valley
magazine (www.vacuumtube.com). All back issues are available,
including issues covering vintage amp restoration, tube & capacitor
listening tests (I find that Illinois Capacitors come closest to the
vintage units' sound when restoring vintage amps), tube history, and
vintage equipment history and reviews. The Heath SP-2 preamp was one
of the recommended Mid-Priced Vintage units. I restored one, and it is
excellent. I have an original Assembly/Operation manual if you need
one (eMail me at if interested). Look for my article
on the vintage Hi-Fi of Sargent-Rayment Co of Oakland CA (1927-1961)
in the upcoming VTV issue #20...(sound of my own horn blowing ;-)
....).
Roger in VT



"Magnusfarce" wrote in message hlink.net...
Thanks for the kind and helpful words, expecially about my little system.
It pales compared to some of the stuff I see and hear about, but I like it
and think it represents very good sound for the money.

I pretty much think I'll pass on the Heath preamp and probably go with
something passive when the time comes. Would the front end of an old NAD
3020 be any good? I know the power amp section is still considered pretty
good for a lower end, lower power amp. Is the preamp section worth
considering?

Anyway, I am looking forward to working on the W5's. I've been handy with a
soldering iron for about three and a half decades now, so I don't expect any
major problems. The Leach amp was great fun to build. If I get into tubes,
I guess I'll have to learn to respect the B+ a little more than I do the +/-
5vdc I use for my little digital projects.

Your ideas about parts replacement will come in handy. When I first got the
amps I got busy and obtained an original manual, and also started lurking
around this group and Google watching for ideas on resistors, caps, and
especially tubes. Years ago I was fairly up to speed on most of the very
high end Wonder Cap-type stuff, but I don't really want to go that far with
these amps. Do you know if there's some sort of cookbook list for
recommended replacement parts for a mid-level upgrade for these units? I'd
like to get past a lot of the guesswork (and arguments) and start acquiring
parts soon. Somewhere quite a while back I saw an upgrade kit offered for
$80, but I've no idea what was in it. Aside from tubes, I don't see the
caps and resistors being terribly expensive. In any case, any specific
recommendations you have for component upgrades would be appreciated.

- Magnusfarce


P.S. Know of any good articles, etc., on general upgrading of old tube
amps?



"Max Holubitsky" wrote in message
...
Thanks to everyone for the comments so far. While I'm looking forward
to
doing the upgrade work on the W5's, I'm not nearly as excited about
doing so
for the preamp, so unless there is a clear consensus that this preamp is
the
ideal match to the power amps, then I'm probably going to let it slide.
I've had thees amps for five years and haven't gotten close to working
on
them yet, so adding the preamp to the pile doesn't help.

Tube equipment is fairly easy to work on, and it's a lot of fun -
especially
power amplifiers. Even if you don't end up falling in love with them, it's
a fun
project, and you won't lose money on classics like the WM5s. Try to get
ahold of
some original heathkit manuals before proceeding to make life easier, if
you're
not used to working on tube equipment. Antique electronics supply is a
good
source for parts, and my personal favourite 6L6s these days are either the
Tesla
6L6GC, or the Chinese 6L6GC STR - you can get these at any guitar store.
Buy
matched pairs, don't mess around with single 6L6's, and if one goes bad,
always
change the pair. I wouldn't change just one spark plug, and I wouldn't
change
just one output tube. The single ones left over from when one of a pair is
bad
make good emergency replacments, to tide you over until you get another
matched
pair.

I should mention that I have not done anything with tubes ever before,
and
as such am not necessarily a true believer in their superiority.
However,
this seems like a great way to perhaps enter that world and begin to see
what its about. I was relieved to read that it's not silly to plan to
use
this system to play CD's because I got rid of almost all my LP's years
ago.
However, my CD collection is quite large and I have many classical and
audiophile disks.


I listen to CDs though a tube system all the time. Don't approach it with
the
attitude that you have to become a believer, approach it as a hobbiest
trying
out something new. Even if you don't like it more than your current setup,
you
will be shocked at how good 50 year old amplifiers can sound.


My main system is not much but not entirely bad, either. I use the HK
HD7600II CD player that had some nice things said about it a long time
ago.
This drives a Sumo Athena preamp and an Adcom GFA 555II, which powers my
Mirage M3's. I biamp through a Sampson Delilah crossover to my
handbuilt
Leach DBA monoblock, driven by homemade JBL B380 (?) subwoofer. That
Leach
amp is the one featured in Audio in the early 80's and is a real
monster.
Not only is it immensely powerful (two half-kv isolation tranformers to
power the rails), but when I completed it several years ago, I A-B'd it
against the Adcom and couldn't really hear any difference. Anyway,
that's
what I listen to. I went through all this so that any further advice
would
be aimed more accurately at my experience level and interests.


This sounds like a cool system!


BTW, the Maggies I spoke of are an old pair of II's. I know the
Heathkits
can't dump a lot of current, but I figured this little system would be
used
for relatively tame music listening. You know, more Mozart than
Metallica.
Thanks again for the help. Anyone interested in buying an SP-2?

Just for kicks, install the WM5s in your good system once you fix them
up... try
them with SUMO preamp, H-K CD player, and the Mirage speakers. MG-IIs are
okay,
but having some real tweeters wouldn't hurt anything at all, and I think
you
will see the WM5s shine on this system, as the Mirage's will be more
sensitive
than the Maggies by far. Try it with a wide variety of music, different
times of
day, and when you're in different moods. The same system that sounds
horrible on
a saturday afternoon while you're trying to blast the 1812 overature may
sound
just amazing at night, when you're playing something more tame. Just a
hunch,
but it may be the Adcom which ends up in the basement, driving the MG-IIs.

P.S. don't mess around with the old tubes... replace all of them, and keep
the
old ones as emergency spares and for if you ever sell the amps. I replace
all of
the tubes in my amplifiers once every 18 months of hard use... even if
they're
not bad. It keeps failures down, and performance up - Mind you, I am the
type of
person who will go out of my way to make sure to change my car's oil at
3000
mile intervals.

P.P.S. Replace all capacitors... the cheap yellow antique electronic
supply one
will do fine to get you off the ground. I'd replace all the electrolytics
with
new axial lead caps the closest value you you can find, but on the high
side.
Make sure that the replacement capacitors are secured mechanically if need
be,
and insulate the leads with insulation stripped off of bell wire, to
minimize
the potential for future problems. The value of electrolytics is not
critical,
as the old caps often had a -20 +100 % tolerance. Make sure all the
replacement
caps have a high enough voltage rating.

Somewhere I have the Manual for the W5M, but there's nothing significant about
it. I do have a copy of the W5M skez, the SP2 skez ( I picked up a mint SP2 for
$100 shipping included). I also have the manual for the W1 P mono preamp I have
4 of these. 2 of them are getting a rewire to become Audio Research SP3 or SP6.
My W5M's will become W5M's with some parts upgrade, and I have a pair of UA2's
which are supposed to have some really great IRON and sound incredible, We
shall see.
DagW00d
"Tigers Older brother DAG"