[Kenneth Warren]

Can I please have an up-to-date response for this perhaps frequently
asked question.

In terms of overall performance, what is the best value 12-20W hi-fi
stereo preamp/amp kit presently on the market?

I am not concerned about the configuration, and will leave that to
the experts.

I am presently using a NAD 3020 (solid state) and like it's warm
tones. I would like to move further in this direction, hence the tube
amp.

BTW I can build to moderate skill levels.

Thank you for your reply.

Ken Warren

[Peter Wieck]

Kenneth Warren wrote:

In terms of overall performance, what is the best value 12-20W hi-fi
stereo preamp/amp kit presently on the market?

http://www.turneraudio.com.au/

Is a good place to start. I would suggest that rather than getting a
full-blown "kit" and all the limitations that imposes these days that
you research what is out there in the DIY world and make a choice from
there. As you are looking in a very moderate power-range, it is
possible that you could build a simple amp from scratch at a much lower
cost than a kit.

Just a thought.

My next suggestion would be to look after any of several vintage units
on the market that are amenable to after-market modifications, or might
be suitable from the git-go. Such include, but are not limited to
Dynaco, Eico, Scott, Fisher, Sherwood, Harmon Kardon and any of
half-a-dozen non-US brands. Again, the bang-for-buck ratio can be quite
substantial as you are already willing to investigate those
modifications.

I left Marantz & McIntosh out of the list above as those are mostly
collectors' items and disproportionately costly.

Peter Wieck
Wyncote, PA

[Ian Iveson]

Kenneth Warren wrote

Can I please have an up-to-date response for this perhaps frequently
asked question.

In terms of overall performance, what is the best value 12-20W hi-fi
stereo preamp/amp kit presently on the market?

I am not concerned about the configuration, and will leave that to
the experts.

I am presently using a NAD 3020 (solid state) and like it's warm
tones. I would like to move further in this direction, hence the
tube
amp.

BTW I can build to moderate skill levels.

Depends where you are, considering carriage costs.

You will find few ppl who have experience or detailed knowledge of
many kits, so the question is unlikely to elicit the kind of response
you want.

You must consider configuration, because it effects the outcome. You
have to choose. An expert can't know which compromises you prefer.

Low-budget valve amps mean cheap transformers. Not worth having in my
view.

In the UK, World Audio Design, attached to "Hi-Fi World" magazine,
seems to be quite well respected and well documented. I think the
transformers are too small, but they could be substituted if there is
enough space on the chassis and if it can support extra weight. WAD
seems flexible in offering part kits.

An advantage of a good kit should be that the fine tuning of any
feedback compensation and suppression of parasitics has been done for
the particular transformer supplied. So if you substitute transformers
this may have to be re-done.

cheers, Ian

[Andre Jute]

Kenneth Warren wrote:

Can I please have an up-to-date response for this perhaps frequently
asked question.

In terms of overall performance, what is the best value 12-20W hi-fi
stereo preamp/amp kit presently on the market?

I am not concerned about the configuration, and will leave that to
the experts.

I am presently using a NAD 3020 (solid state) and like it's warm
tones. I would like to move further in this direction, hence the tube
amp.

BTW I can build to moderate skill levels.

Thank you for your reply.

Ken Warren

I've built quite a few tube amp kits but mainly at the higher end of
the market.

However, besides your budget, it is useful to know which speakers you
have, what their sensitivity is, and what sort of music you like
playing. Some tube topologies, single-ended for instance, is economical
only with highly sensitive speakers.

SEX
The outstanding low cost kit is the SEX, which stands for Single Ended
Experimenter's Kit. I believe it is still sold in modified form. Back
then for four hundred bucks you got two monoblocks in the form of laser
cut plates and all components; you had to bring the wire and make the
wooden box; for another thirty bucks you got four little ali drivers
with enough sensitivity to build suitable speakers -- I had a lot of
fun with those drivers in speakers made with carpet tubes and playing
Gregorian chant with truly gothic bass. Super playing into regular
(sensitive) speaks as well, a sound right out of its class. About 2W
Class A from PSE 6DN7.Very developable, as the name tells you. See my
review in Glass Audio about seven or eight years ago. The maker is Dan
Schmalle of Electronic Tonalities of Poulsbo, WA; he also publishes
VALVE magazine and you can find his enthusiasts at the Audio Asylum.

ARION ADONIS
The best of the reasonably priced European kits I built was the Arion
Adonis, PP 5881 running in Class A for enough power to drive normal
bookcase speaker. Everything about this amp was properly executed
because the motivating force behind Arion was a Scot of truly driven
cheapness (I know; he once sent me back to my drawing board for
"wasting" a single milliamp in a design I made for him...) who expected
exceptional value for every penny. You got a polished stainless chassis
and transformers designed by the excellent Simon Shilton, and the very
best parts within the price bracket. The Adonis was later sold by
someone else, who may still be in business and selling it or its
successor. I can't remember if I reviewed this one for Glass Audio or
another magazine, but I liked it so much that I still have and play it
occasionally many years later; I never fail to be surprised at the
clarity and beauty of sound from an amp that cost only a few hundred
pounds.

STEIN PRE
Another kit that is very reasonably priced for what its excellent
quality, though probably outside your budget for just a pre-amp, is the
Stein Audio pre with the 6DJ8. This is an introduction the very finest
in design and component selection (glass capacitors!) backed by Holger
Stein's experience, with a very seductive liquid sound that does well
driving silicon amps, cutting their acid to bearable proportions.

VELLEMAN K4000
This is PPP EL34 for 18W in Class A and near enough 1000W in Class B,
an amp with oomph that really rocks. It's schizo of course, very sweet
in Class A, a monster with full bass range in Class B. Pricey but good
value for excellent professional design and good parts, backed by the
Velleman completion guarantee (if it fails to work when you've soldered
it, you return it to them and they fix your foulups). I built this for
a review and still have it a decade later; the model number may now be
different. Velleman gear is of the sturdiest: I have test gear I built
from their kits fifteen years ago, including my everyday DMM and my
handheld scope, that just work and keep working; Velleman is
trustworthy.

TRIODE SUPPLY JAPAN VPD-3000 "MIYABE"
This was then and is today absolutely the best kit you can buy. It cost
1600 dollars back about eight years and was a bargain then. 300B PSE
for about 16W, so I used it on my ESL63, so you can use it with any
speakers except the most grotesquely insensitive. Another amp sold by a
maniac who doesn't take "no" for an answer or any excuse at all when it
comes to getting just the quality he wants. I priced up the parts and
they came to twice the purchase price -- and a good bit besides. I
still have this one too, and it is one of the amps I play most
frequently. My review was in Glass Audio.

****

Having mentioned some kitmakers I can recommend, let me give you a tip.
A kit is an entertainment and an education in the building, a matter of
pride once you have it up and working. But it won't save you money. The
cheap way to get a tube amp is to buy Chinese. That solves your biggest
problem in DIY, suitable casework, at a single stroke, and gives you a
framework on which you try your own improvements. Buying Chinese is a
twist on the good advice usually given here to buy an old amp and
rebuild it; the cost of that advice is usually excessive -- I'm looking
at the invoices for parts to rebuild a mostly good pair of Quad II as I
write to you, and wondering if I shouldn't just have sold them on "as
seen".

If you're in the States, Dan Schmalle may be cheaper than the Chinese
route. If you're in Europe, see if Arion is still offering kits (they
are in Belfast). In Germany, besides Holger Stein (Stein Audio), you
might try Allen Wright, who markets a modular PP kit with very flexible
casework that you buy bit by bit as you need it; Allen knows what he's
talking about (he's the guru of constant current loads). If you're in
the Far East, shop the Triode Supply Japan catalogue; they make less
expensive models than the flagship Miyabe.

HTH. Good luck.

Andre Jute
Visit Jute on Amps at http://members.lycos.co.uk/fiultra/
"wonderfully well written and reasoned information
for the tube audio constructor"
John Broskie TubeCAD & GlassWare
"an unbelievably comprehensive web site
containing vital gems of wisdom"
Stuart Perry Hi-Fi News & Record Review

[Peter Wieck]

Andre Jute wrote:

Having mentioned some kitmakers I can recommend, let me give you a tip.
A kit is an entertainment and an education in the building, a matter of
pride once you have it up and working. But it won't save you money. The
cheap way to get a tube amp is to buy Chinese. That solves your biggest
problem in DIY, suitable casework, at a single stroke, and gives you a
framework on which you try your own improvements. Buying Chinese is a
twist on the good advice usually given here to buy an old amp and
rebuild it; the cost of that advice is usually excessive -- I'm looking
at the invoices for parts to rebuild a mostly good pair of Quad II as I
write to you, and wondering if I shouldn't just have sold them on "as
seen".

This is where Andre is at a disadvantage. Here in the US, not only are
vintage amps thick on the ground (at usually quite inexpensive prices),
but many of the aftermarket suppliers are also a $4.50 priority-mail
shipping box away over the cost of their parts. Avoid eBay unless you
are in a hurry, get out, get around and you will find all sorts of
stuff to trip over. I have done any number of kits over the last 46
years since I built my very first one (which did work, to this day I
perceive that as a near-miracle). Put simply, I learned far more from
trouble-shooting failed equipment than from any kit ever. Just in
researching for making my one 'scratch-built' amp, I have learned more
of what choices are out there than from much trouble-shooting. Kinda
like the difference between reading lines from a set-piece, editing a
set of bad directions for clarity and content and designing,
specifying, building, trouble-shooting and then describing from scratch
so the next person can do it without issue.

New kits are good insasmuch as they get you there with a minimum of
fuss-over-assembly. But as they more-or-less must be idiot-proof by
design and execution (the set-piece, if you will), they do not offer
much scope for experimentation beyond specifically designed-in options.
Some of the vintage equipment has 40+ years of failure analysis,
evolution and experimentation behind it. Picking the Dynaco ST-70 out
of thin air (BE QUIET, BRET!), there are mods to that start with a
single 10-ohm, 10 watt ceramic resistor and finish with a complete
rebuild using only the tube sockets (and not all of them), the
sheet-metal and the iron (The Turner Audio Rebuild). Figure you should
be able to find a suitable, good quality vintage amp, do the mods and
even replace the tubes in it with "new" for less than $500 if you are
patient, $300 if you are both patient and lucky.

With Chinese Junque, you get what you pay for. If the Iron is good,
there may be hope for it with modifications. But I have not seen a
Chinese amp at *retail* that delivers as well as the same $$ spent on
either a DIY, or an upgraded vintage amp. I spent a few moments between
calls today at a shop owned by a friend who has half-a-dozen Chinese
amps lined up for his customers to test (where I found the McIntosh
tuner). All I can say about them is 'eh'. He says that they sell like
hot-cakes.... De gustibus and so forth. On the other hand, some of the
kits do look intriguing, their greatest value would be in the building
thereof, not necessarily the finished results.

Lastly: Note that in DIY, expect that you are paying yourself
$0.25/hour or less and the rest is the pleasure of doing it. This may
be enough of a motive in itself.

Peter Wieck
Wyncote, PA

[John Jensen]

My suggestion is to go to triodeelectronics.com. You can build a classic
Dynaco Mk II (or is it III?) 60 W amplifier clone from all that Ned Carlson
has to offer. A lot more expensive than the original $69.95-$79.95 of the
original (but so is everything). If he can get a Dynaco PAS-3 (or 3X) cheap
(not easy), it can be used as is or upgraded with what Triode Electronics
has available.

John

"Peter Wieck" wrote in message
ups.com...

Kenneth Warren wrote:

In terms of overall performance, what is the best value 12-20W hi-fi
stereo preamp/amp kit presently on the market?

http://www.turneraudio.com.au/

Is a good place to start. I would suggest that rather than getting a
full-blown "kit" and all the limitations that imposes these days that
you research what is out there in the DIY world and make a choice from
there. As you are looking in a very moderate power-range, it is
possible that you could build a simple amp from scratch at a much lower
cost than a kit.

Just a thought.

My next suggestion would be to look after any of several vintage units
on the market that are amenable to after-market modifications, or might
be suitable from the git-go. Such include, but are not limited to
Dynaco, Eico, Scott, Fisher, Sherwood, Harmon Kardon and any of
half-a-dozen non-US brands. Again, the bang-for-buck ratio can be quite
substantial as you are already willing to investigate those
modifications.

I left Marantz & McIntosh out of the list above as those are mostly
collectors' items and disproportionately costly.

Peter Wieck
Wyncote, PA

[Tom A.]

Having mentioned some kitmakers I can recommend, let me give you a tip.
A kit is an entertainment and an education in the building, a matter of
pride once you have it up and working. But it won't save you money. The
cheap way to get a tube amp is to buy Chinese. That solves your biggest
problem in DIY, suitable casework, at a single stroke, and gives you a
framework on which you try your own improvements. Buying Chinese is a
twist on the good advice usually given here to buy an old amp and
rebuild it; the cost of that advice is usually excessive -- I'm looking
at the invoices for parts to rebuild a mostly good pair of Quad II as I
write to you, and wondering if I shouldn't just have sold them on "as
seen".

I know that Chinese amps are often ridiculised in this group. I can
imagine that often it's with a reason. Now I had a very good experience
just last week when I was on a business trip in Hong Kong: I heard the
very well built Melody SP3 tube amp driving expensive Zu Definition
speakers. There was absolutely nothing wrong with that sound. It must
be said that the Zu's are enormously efficient, but with the SP3
delivering 38 watts it should be nicely useable with many loudspeakers.
You can read a review about the SP3 on www.6moons.com . The price: in
Hong Kong it was the equivalent an incredible ... wait for it ... 550
EUR. Considering the quality of sound I experienced and the very high
standards of finish, this is a bargain. The price in the west is still
not bad for what you get, but it's not such a bargain anymore.
I was sorely tempted to carry one back to Europe... but I had a
problem: I first had to take trip to Singapore, on an economy flight,
hence that would give extra shipping costs, and I would need to pass
customs twice. Perhaps, when I get to do another trip to only Hong
Kong...

cheers,

Tom, who's meanwhile gathering parts to build an Aikido pre-amp (see
www.tubecad.com)

[Peter Wieck]

Tom A. wrote:
The price: in
Hong Kong it was the equivalent an incredible ... wait for it ... 550
EUR.

At present conversion values, that comes in at US$705.65 exclusive of
shipping and various taxes. Even at that price and in the US, that is
high for such an amp *IF* it is compared to readily available vintage
amp upgrade/conversions (including the (in)famous VanAlstine ST-70).
And in terms of what is available to the DIY, that is very high. But
well-under exotic US-made *new* tube designs, of course.

I have no argument that Chinese Junque can look mighty nice, bending
sheet-metal and powder-coating is not rocket science by any means. But
I tremble to see the fractured-english manuals and wonder whether as
much care goes into the assembly as the translation. One would think
that a manual would be written with _GREAT_ care as improper set-up
could be spectacularly nasty. "Consumer-buyer is noted to be that maker
may not warn of changes cannot guarantee accurate in future terms
beware." is NOT comforting sentence, but one that I see on a schematic
for an Antique Audio monoblock amp (made in China, of course).

In this case, the phrase "time will tell" applies. How many Chinese
amps sold today will still be singing in 40 years?

Peter Wieck
Wyncote, PA

[Peter Wieck]

Bret Ludwig wrote:

Stuff....

You are very much like your Australian peer, Mr. Allison. Warped,
prejudiced, angry and mostly absurd. But occasionally some truth
escapes despite yourself.

Peter Wieck
Wyncote, PA

[Tom A.]

At present conversion values, that comes in at US$705.65 exclusive of
shipping and various taxes. Even at that price and in the US, that is
high for such an amp *IF* it is compared to readily available vintage
amp upgrade/conversions (including the (in)famous VanAlstine ST-70).
And in terms of what is available to the DIY, that is very high. But
well-under exotic US-made *new* tube designs, of course.

It is true that the conversion to dollars is less atractive currently
than the coversion to euro.

I have no argument that Chinese Junque can look mighty nice, bending
sheet-metal and powder-coating is not rocket science by any means. But
I tremble to see the fractured-english manuals and wonder whether as
much care goes into the assembly as the translation. One would think
that a manual would be written with _GREAT_ care as improper set-up
could be spectacularly nasty. "Consumer-buyer is noted to be that maker
may not warn of changes cannot guarantee accurate in future terms
beware." is NOT comforting sentence, but one that I see on a schematic
for an Antique Audio monoblock amp (made in China, of course).

I can only tell you that the SP3/Zu combination DID sound excellent. It
is true that when connected to the 100db efficient Zu with active
woofers, the amp didn't have to do any effort. I would like to hear it
with 90db-ish speakers.
It is also really well made. And I have yet to find a less than
positive review anywhere on the net or in magazines. It seems that
Melody is also one of the more serious Chinese brands, considering
their other, more upmarket products.

Building yourself will of course give the most satisfaction and you
will know exactly what quality of OPTs go in there etc, but for those
wjo don't want or can't take the DIY route this little amp is a nice,
affordable gateway to the world of tubes.

In this case, the phrase "time will tell" applies. How many Chinese
amps sold today will still be singing in 40 years?

I have no idea. But I also think that you're wrong in systematically
declaring Chinese hifi brands as junk. After all, Quad products are now
made in china too. If anything, we should be grateful that these
brands lower the treshold.

best regards,

Tom

[Peter Wieck]

Tom A. wrote:
.. After all, Quad products are now
made in china too. If anything, we should be grateful that these
brands lower the treshold.

As are Zenith, Philco, Packard-Bell, Crosley, Sony, Marantz, KLH,
Sherwood, Scott, and a whole bunch of others. Infinity, Advent & AR,
even Thorens, Dual, Philips & Grundig in part.

Lowering the threshold....

Possible in some cases. More likely a race for the bottom.

Peter Wieck
Wyncote, PA

[Andy Evans]

Scratchbuildiong is the most educational and yet the least frustrating.


I'm totally with Bret here - if you have the courage, build from
scratch. It's what you'll end up doing so you may want to cut out the
intermediate step of rebuilding a Dynaco or Leak amp (interesting and
instructive as it is - I think we've all been there). Before doing
anything, buy "Valve Amplifiers" by Morgan Jones off Amazon (e.g.) and
read it and use it as a reference all the way through your build.

You want to make some basic decisions. These are the ones I recommend.

a) Chassis. Think BIG, then BIGGER. If you are seriously going to carry
on building you may like to start with two chassis - one power supply
and one circuit. Your absolute minimum chassis size is a 2U 19"
rackmount case - get a solid one, if possible with one side predrilled
full of holes. You can use two of these - power supply and circuit.
Your power supply should be approximately 300vDC for the HT at a
minimum of 200mA. Feel free to chuck in as many chokes as you like -
you can use 100mA ones and split the power supply into two channels.
Use one set of chokes for the output and another for the input - four
chokes of 100ma is nice. Forget electrolytics - buy ordinary motor run
polypropylene caps, sizes 40uf are fine. Start with solid state
rectification, but leave room for valve rectifiers which you may want
to add later. For umbilical use 8 pin Neutrik Speakons or Amphenol
sockets.

b) Single ended or push pull. I'd suggest push pull - possibilities of
many many circuits to copy and higher output. Can be as good as
anything if you use DHTs (directly heated triodes). I'd go a step
further and suggest balanced all the way through, with three stages. In
Morgan's book you'll find some constant current sinks to build which
you put under each of the first two stages (page 134). If you have a
single ended input, normal phono plugs, ground the second grid of the
first valve (again in the book).

c) Get some decent output transformers. start with Hammond or something
simple, but leave plenty of space to try something else. I'd suggest 5k
to 6.6K in push-pull.

d) Valves to use. If you want to aim for very good, use all octal
sockets - don't even consider the smaller nine pins. If you want to aim
for the best use all UX4. Plan your chassis layout for twelve UX4
sockets - big holes here. Get the right hole saw to put in your drill
to drill out these holes, and imagine that each valve is 50mm across,
so allow at least that plus another 15mm - 20mm space in between
valves. This is why I'm talking big chassis. You are now ready for your
super amp. The valves you can use go from 76 which is normal 6.3v
heaters to fancy stuff like 26, a DHT, which will blow your mind away,
but need special DC supplies. Get some cheap bench power supplies and
use 26s - you'll just love them. They take 1amp on the heaters so any
bench power supply that does 0-30 at 1amp is OK. Run the heaters in
series in push pull. Or stay simple - one huge toroid at 6v will power
a whole lot of valves. For output you can start with 807 in triode,
using UX5 socket - same cutout as UX4 so you can swap later for a 2a3
or 300b.

e) use a three stage circuit - plenty about. Go to www.audioasylum.com
and hang out there and ask for suitable circuits, or work one out from
Morgan's book. Look for circuits for a 6SN7 and substitute two 76 for
one 6SN7.

This may all be too advanced, but if you take the plunge and build big,
you will eventually make your super amp using the same chassis and
componants you started off with - nothing wasted, nothing to throw away.

[Andre Jute]

First Bret Ludwig wrote:
Scratchbuildiong is the most educational and yet the least frustrating.

Andy Evans wrote:
I'm totally with Bret here - if you have the courage, build from
scratch.

This is true, in very limited circumstances. Ludwig is a technician who
has long since forgotten how much time he spent learning the necessary
electronics. Andy is, if I recollect correctly, a psychologist, as I
am; he is such a longtime hobbyist that he too has forgotten when he
learned his electronics and how hard it was. I am now in the same boat:
it is no problem for me to design just the amp I want at any time, and
to knock it up with chasses and parts I have, and to develop and tune
it just so. But I think that, if I hadn't started with kits, I would
have given up in frustration, trying to learn the basics of electronics
and the ins and outs of components and construction all at the same
time. A stepwise approach makes more sense; that is why so many people
learned on secondhand gear and I now recommend starting with a kit or a
cheap, developable Chinese amp.

My own recipe for a starter kit is at the bottom. Meanwhile a few notes
on the rest of Andy's post:

It's what you'll end up doing so you may want to cut out the
intermediate step of rebuilding a Dynaco or Leak amp (interesting and
instructive as it is - I think we've all been there). Before doing
anything, buy "Valve Amplifiers" by Morgan Jones off Amazon (e.g.) and
read it and use it as a reference all the way through your build.

You need two copies of each of Jones and the RDH so you can keep one in
your lavatory or beside your bath or on your bedside table, wherever
you do most of your reading.
http://members.lycos.co.uk/fiultra/J...Bookshelf.html

The kernel of Andy's advice is mad, magnificently mad but mad none the
less. Since I'm an economist as well as a psychologist, you'll forgive
me if I point out the obvious, which is that Mad Andy Evans wants you
to build with tubes that are no longer made, in limited supply, already
very expensive, likely to become more expensive. Nobody can accuse me
of speaking up for anything less than excellence, or of being cheap but
advising newbies to build with obsolete DHTs is one fast way to drive
them screaming from the hobby.

Still, big chasses and octals is good advice. Here is an amp for all of
a third of a watt...
http://members.lycos.co.uk/fiultra/K...0T68MZ417A.jpg

You want to make some basic decisions. These are the ones I recommend.

a) Chassis. Think BIG, then BIGGER. If you are seriously going to carry
on building you may like to start with two chassis - one power supply
and one circuit. Your absolute minimum chassis size is a 2U 19"
rackmount case - get a solid one, if possible with one side predrilled
full of holes. You can use two of these - power supply and circuit.
Your power supply should be approximately 300vDC for the HT at a
minimum of 200mA. Feel free to chuck in as many chokes as you like -
you can use 100mA ones and split the power supply into two channels.
Use one set of chokes for the output and another for the input - four
chokes of 100ma is nice. Forget electrolytics - buy ordinary motor run
polypropylene caps, sizes 40uf are fine. Start with solid state
rectification, but leave room for valve rectifiers which you may want
to add later. For umbilical use 8 pin Neutrik Speakons or Amphenol
sockets.

b) Single ended or push pull. I'd suggest push pull - possibilities of
many many circuits to copy and higher output. Can be as good as
anything if you use DHTs (directly heated triodes). I'd go a step
further and suggest balanced all the way through, with three stages. In
Morgan's book you'll find some constant current sinks to build which
you put under each of the first two stages (page 134). If you have a
single ended input, normal phono plugs, ground the second grid of the
first valve (again in the book).

c) Get some decent output transformers. start with Hammond or something
simple, but leave plenty of space to try something else. I'd suggest 5k
to 6.6K in push-pull.

d) Valves to use. If you want to aim for very good, use all octal
sockets - don't even consider the smaller nine pins. If you want to aim
for the best use all UX4. Plan your chassis layout for twelve UX4
sockets - big holes here. Get the right hole saw to put in your drill
to drill out these holes, and imagine that each valve is 50mm across,
so allow at least that plus another 15mm - 20mm space in between
valves. This is why I'm talking big chassis. You are now ready for your
super amp. The valves you can use go from 76 which is normal 6.3v
heaters to fancy stuff like 26, a DHT, which will blow your mind away,
but need special DC supplies. Get some cheap bench power supplies and
use 26s - you'll just love them. They take 1amp on the heaters so any
bench power supply that does 0-30 at 1amp is OK. Run the heaters in
series in push pull. Or stay simple - one huge toroid at 6v will power
a whole lot of valves. For output you can start with 807 in triode,
using UX5 socket - same cutout as UX4 so you can swap later for a 2a3
or 300b.

e) use a three stage circuit - plenty about. Go to www.audioasylum.com
and hang out there and ask for suitable circuits, or work one out from
Morgan's book. Look for circuits for a 6SN7 and substitute two 76 for
one 6SN7.

This may all be too advanced, but if you take the plunge and build big,
you will eventually make your super amp using the same chassis and
componants you started off with - nothing wasted, nothing to throw away.

Okay, here we go with a sensible, flexible setup for a starter kit for
a beginning DIYer.

First, decide on SE or PP. I suggest PP for the flexibility and
slightly lower cost. (SE can be cheap too--
http://members.lycos.co.uk/fiultra/Jute-EL34-SEntry.jpg
--but unless you have a lot of money it can be very limiting.)

Next buy two Hammond 17x10x4 inch ali boxes and six or so 17x10 covers
and about a dozen each of 6x4 and 4x4 ali plates (they're covers for
smaller boxes you won't buy). Buy some slotted 3/4 in angle ali. Brace
the two flimsy Hammond boxes with the ali on all edges. Bolt ali angle
strips across the width four inches apart. The less than an inch open
at end will be to lead cables in while you do development work. Don't
be tempted to buy steel cases; they'll just skin your knuckles and
blunt your tools and discourage you before you even start work. These
two boxes are in any event just covers for electronics. It is easier to
build on the big flat coverplate stiffened by ply, and then just to
bolt on the box as safety cover. But for the time being you will build
on the little plates section by section and bolt them onto the
framework. One box is your power supply, the other the amplifier.

Decide to use only octal tubes. The 6SN7 is greatest signal tube and
small power tube too that God ever made, and the 6SL7 the sweetest. The
EL34 is the greatest power tube God ever made, and that includes the
300B. The 6SN7 is in production in Russia and China, and so is the
EL34; the 5SL7 is in plentiful cheap supply and equivalents are also
available. These are just samples: there are many more octal tubes
worth your attention for one reason or another, like the KT88/6550 for
more power, for instance. All the really desirable tube rectifiers are
octal.

A stereo PP amp needs a minimum of four octal sockets on the chassis (I
will publish such a design in the next few weeks) but all you'll drive
with it will be a pair of headphones or some small multimedia speakers.
A realistic stereo PP amp needs at least input/gain, phase splitter and
power tube sockets, which adds up to a minimum of six sockets for
single-ended inputs. For balanced inputs, or at least long-tail pairs,
which open the way to balanced input, and differential gain stages, you
need two sections or one whole envelope per stage, so now you need
eight sockets for the signal section. You might want a buffer or an
extra gain stage for some reason, so add two more sockets for a grand
total of ten. Unused sockets can just sit there. You fit these sockets
two to a 4x4 ali plate (you clamp them all and drill them all five
plates at once) or even six to a 6x4 ali plate -- it depends on what
circuitry you want to attach to the socket pins and standoffs or
component strips you also bolt to the same plate. Each stage or group
of stages is built complete on the plate so that it has only wires
leaving for signal in and out, power and earth (to a star ground near
the mains input). The complete plate is bolted onto the angle ali over
the open end of your cover box. Input and output and control circuitry
also goes onto these or separate plates; you don't drill the main box
for the RCA, five-way connectors, mains input, switches and volume pot
until you have a humfree arrangement.

The power supply needs four sockets in case you ever want to build a
rectifier bridge. You won't. The Graetz bridge with one fullwave
rectifier and two diodes that I show in many of my circuits--
http://members.lycos.co.uk/fiultra/T...trafi-crct.jpg
--works indistinguishably from a full tube rectifier bridge, but the
other sockets will be handy if you ever want to build a tube regulator,
or for separate power takeoffs or for plugging in relays. You can buy
plugs to fit octal sockets and they're well rated and cheap, an easy
solution to a perennial problem. Some come with a big cover for
building silicon electronics inside and I have used them for building
constant current sinks.

Next you need very, very flexible transformers. In the States UBT sells
a universal transformer roughly equivalent to the old Tango 808 but of
course vastly cheaper. In Europe it isn't really worth going for
anything less than cut C-core Lundahl transformers, which are a couple
of magnitudes up the scale from the UBT; Lundahls may seem a little
pricey at first but they are the best-sounding transformers in the
world, the top models are the most flexible, and in that light they are
a stunning bargain. Buy the Lundahls with multiple windings on the
secondaries which can be connected to reflect a vast range of primary
impedances and connected to virtually any speaker impedance. Or, if you
know you will stick with the stunning EL34 and its relatives, in the
States you can buy Plitron transformers designed by Menno van der Veen;
the same design is sold by Åmplimo in Europe. A pair of Lundahls or
Plitron/Amplimo vanderVeens will last your lifetime. Menno has
published some really good amp designs to use with these transformers;
Plitron sells his book with these designs--
http://members.lycos.co.uk/fiultra/J...S%20T%26T.html
--and also a PCB to speed your work if you're in too much of a hurry to
hardwire.

A Lundahl LL1651 power transformer is beefy, well-made, silent, and
with four 3.1A filament supplies and a 250-0-250V supply of 430mA is
very flexible. The Lundahl mains and output transformers all fit the
same bolt footprint and their bases are tapped, so you just drill three
4x4 plates all at once.

A choke is a really good piece of iron to have. The Lundahl LL1638 is
very flexible since it is wound with two coils which can be used in
series for 10H/200mA or in parallel for 2.5H/400mA; it can also be
split across the positive and negative rails to give you a quieter
amp--
http://members.lycos.co.uk/fiultra/K...dre%20Jute.htm
http://members.lycos.co.uk/fiultra/K...hn%20Byrns.htm
Two chokes gives you the opportunity to investigate the attractions of
choke input power filters, which changes the sound appreciably. The
choke, or a pair, sits on a 6x4 plate together with holes for bolting
down the associated caps.

Now you're ready to design and build an amp. I suggest it be PP Class
A1 trioded EL34. That's simple to design and build, and will give you a
decent output. If it isn't enough power for your speakers, you can
rewire for class A/B and get 24 clean watts. If you need more than 20W,
you should build better speakers--
http://members.lycos.co.uk/fiultra/K...Impresario.jpg
http://members.lycos.co.uk/fiultra/K...20T91HWAF3.jpg
You will eventually get there anyway when your amp will be so much
better than your current speakers that the speakers will become the
bottleneck in your system. There's a lot of design information he
http://members.lycos.co.uk/fiultra/T...mp%20INDEX.htm
You might also want a root around in my general hi-fi design site:
http://members.lycos.co.uk/fiultra/JUTE%20ON%20AMPS.htm

Good luck.

Andre Jute
Visit Andre Jute at http://members.lycos.co.uk/fiultra/
"wonderfully well written and reasoned information
for the tube audio constructor"
John Broskie TubeCAD & GlassWare
"an unbelievably comprehensive web site
containing vital gems of wisdom"
Stuart Perry Hi-Fi News & Record Review

[Peter Wieck]

Andre Jute wrote:

Lots-O-Stuff. Mostly on-target.

Andre....

Be careful. That little dickens McCoy is poking its egotistical nose
(and my goodness, but it is a long one) out from its cage. Try to keep
the madness at bay.

A couple of things to keep in mind however before advising anyone to
leap full into tube-based scratch-building.

A. Tube based systems, while not complex, can be rather dangerous.
Between the lethal voltages in use, the potential for spectacular and
expensive - and very simple - mistakes and the many thousands of
choices, options and approaches available, some hands-on experience
with well-established systems is advisable.

B. Such well-established systems with many options and many years of
research, failure-analysis and proven modifications surrounding them
can be excellent learning experiences in both theory and practice.
Furthermore and despite Bret's opinions, it can be done quite
inexpensively.

C. Working outside of a straightforward "kit" mode, but within such
parameters as noted will not only help the autodidact but will
establish connections between theory and practice such that the
book-learning will be connected to reality.

D. There is nothing like a few early successes right out of the gate to
give one the confidence to go forward. This as compared to smelling and
watching a set of output transformers giving up their magic smoke
because an improper connection was made. Or some similar disaster.

Peter Wieck
Wyncote, PA