[Peter Wieck]

In my travels, I snagged a bunch of 7199s, all testing very nicely on
my Hickok. As all here know, they are a heavily used driver tube for
everyone from Scott to Eico to Dynaco and others back in the day. Given
that I have amps two-of-three of the above using them, they will not go
to waste in any case. But:

Any reason why I should not use the 7199 as a driver for my proposed
first home-brew PP amp?

My stock of output tubes includes EL84/6BQ5, 6CA7/EL34 and 6550/KT88. I
would prefer to work from stock this time around. I have a good supply
of octal, 7-pin miniature and 9-pin miniature ceramic sockets, as well
as similar shielded 7 & 9 pin sockets

The transformers are from a Fisher 500B, and are good.

I am looking for maybe 15-25 watts, not to drive anything into
oblivion. I have looked at a couple of circuits using a single 12AX7
driver per channel, as well as all sorts of versions, modifications and
improvements to Vintage designs. Put simply, I would not mind emulating
a vintage design as a start and then jump off from there.

I have a couple of very good surviving parts suppliers nearby, as well
as the usual suspects (Newark, Mouser, Fair Radio, AES and the rest of
the Internet sources).

Suggestions gladly solicited.

[Jon Yaeger]

in article , Peter Wieck
at wrote on 11/8/06 2:27 PM:

In my travels, I snagged a bunch of 7199s, all testing very nicely on
my Hickok. As all here know, they are a heavily used driver tube for
everyone from Scott to Eico to Dynaco and others back in the day. Given
that I have amps two-of-three of the above using them, they will not go
to waste in any case. But:

Any reason why I should not use the 7199 as a driver for my proposed
first home-brew PP amp?

My stock of output tubes includes EL84/6BQ5, 6CA7/EL34 and 6550/KT88. I
would prefer to work from stock this time around. I have a good supply
of octal, 7-pin miniature and 9-pin miniature ceramic sockets, as well
as similar shielded 7 & 9 pin sockets

The transformers are from a Fisher 500B, and are good.

I am looking for maybe 15-25 watts, not to drive anything into
oblivion. I have looked at a couple of circuits using a single 12AX7
driver per channel, as well as all sorts of versions, modifications and
improvements to Vintage designs. Put simply, I would not mind emulating
a vintage design as a start and then jump off from there.

I have a couple of very good surviving parts suppliers nearby, as well
as the usual suspects (Newark, Mouser, Fair Radio, AES and the rest of
the Internet sources).

Suggestions gladly solicited.



Peter,

One fairly common complaint of vintage 7199s is that they can be noisy. Do
you have a way to test that before you get too far down the road?

My personal preference would be to use a 6SN7 or 6FQ7 driver arrangement,
because those tubes are a lot easier to get than (replacement) 7199s, and
they are very linear triodes.

Check out the driver arrangement for, say, the Eico HF87 amplifier. It's
simple and it sounds quite good with the Eico iron. Or the Acrosound series
of schematics published widely on the web.

Jon

[Peter Wieck]

Jon Yaeger wrote:
One fairly common complaint of vintage 7199s is that they can be noisy. Do
you have a way to test that before you get too far down the road?

Agreed, and yes, I do. First, I have perhaps 16 of them (spares) from
NIB to "well-seasoned". And I also have a range of amps for testing as
well as a scope. I am not wedded to them, mind. Most of these are
labeled as Sylvanias, so if they are truly from the Sylvania plant and
not late-in-the-game re-labels, they will be very good tubes. In fact,
were they not Sylvanias and also cheap enough, I would have let them be
as I do have plenty anyway.

My personal preference would be to use a 6SN7 or 6FQ7 driver arrangement,
because those tubes are a lot easier to get than (replacement) 7199s, and
they are very linear triodes.

I have a bunch of 6SN7s as well, even some red-base Tung-Sols, even
though I have never been a Big Believer in such things (right, after
the bit on Sylvania tubes above). I am making bread-boards from pieces
of plexiglas using drilled -through 12ga. copper-wire posts for
clipping, snubbing or soldering. This will allow me to (quickly) change
sockets and try different drivers as well as allowing for a very neat
final assembly. The ultimately, the tube sockets will get a more
thermally stable substrate or go directly on the chassis, but the
passive components could be easily managed on plex & solder-post
boards. Wire management, shielding and general safety are driving
considerations in the physical design.

Check out the driver arrangement for, say, the Eico HF87 amplifier. It's
simple and it sounds quite good with the Eico iron. Or the Acrosound series
of schematics published widely on the web.

I have looked at those, some of the Scotts, some of the revisions of
the Dynaco designs and so forth. The Eico designs have been suggested
to me two others (you now make three), and there is a very elegant and
simple design I saw in a Chinese amp using a 12AX7 that I keep going
back to for its simplicity. And one individual in particular is
constantly harping on Williamson/Acrosound designs. Since I have seen
his products using them (and they are VERY good), I am inclined to
listen to him also.


Peter Wieck
Wyncote, PA

[John Byrns]

In article . com,
"Peter Wieck" wrote:

In my travels, I snagged a bunch of 7199s, all testing very nicely on
my Hickok. As all here know, they are a heavily used driver tube for
everyone from Scott to Eico to Dynaco and others back in the day. Given
that I have amps two-of-three of the above using them, they will not go
to waste in any case. But:

Scott only used the 7199 for a brief period of time before thinking
better of it and reverting back to the previously used 6U8 type tube.

Any reason why I should not use the 7199 as a driver for my proposed
first home-brew PP amp?

My stock of output tubes includes EL84/6BQ5, 6CA7/EL34 and 6550/KT88. I
would prefer to work from stock this time around. I have a good supply
of octal, 7-pin miniature and 9-pin miniature ceramic sockets, as well
as similar shielded 7 & 9 pin sockets

I would vote for the EL84s in the Mullard "low load" configuration.

The transformers are from a Fisher 500B, and are good.

I don't know the specifications for the 500B OPTs, but since they were
designed for the 7591 they are probably right on for the EL84 in the
Mullard "low load" configuration.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[Peter Wieck]

John Byrns wrote:

I don't know the specifications for the 500B OPTs, but since they were
designed for the 7591 they are probably right on for the EL84 in the
Mullard "low load" configuration.

That more-or-less feeds into my initial wish to use the EL84/6BQ5 in
the first place. And, as it happens, I have two Mullard matched-pairs
that I might install after all final testing and troubleshooting is
done. I am a bit of a dandelion seed in these intitial stages chasing
after each breeze, but once I settle on a starting point, I hope better
than just another weed results.

Thanks.

Peter Wieck
Wyncote, PA

[Sander deWaal]

"Peter Wieck" said:


I am looking for maybe 15-25 watts, not to drive anything into
oblivion.

KT88 in triode will fit the bill quite nice:

http://img508.imageshack.us/img508/1751/wkschemod0.jpg

It was reviewed very well in several listening sessions with the Dutch
DIY-ers from the forums www.zelfbouwaudio.nl and
www.circuitsonline.net , and with several individuals who borrowed the
amp from me.


You probably don't read Dutch, there's an explanation on why I
delivberately put the phase splitter out of balance.

http://zelfbouwaudio.nl/forum/viewtopic.php?t=2323

You'll have to excuse me, I have amps to build ;-)

--
"Due knot trussed yore spell chequer two fined awl miss steaks."

[Peter Wieck]

Sander, thank you.

I will investigate further when we get back from our New England jaunt.


Peter Wieck
Wyncote, PA

[Jon Yaeger]

in article , Bret Ludwig
at wrote on 11/10/06 8:02 AM:


Peter Wieck wrote:
Jon Yaeger wrote:
One fairly common complaint of vintage 7199s is that they can be noisy. Do
you have a way to test that before you get too far down the road?

Agreed, and yes, I do. First, I have perhaps 16 of them (spares) from
NIB to "well-seasoned". And I also have a range of amps for testing as
well as a scope. I am not wedded to them, mind. Most of these are
labeled as Sylvanias, so if they are truly from the Sylvania plant and
not late-in-the-game re-labels, they will be very good tubes. In fact,
were they not Sylvanias and also cheap enough, I would have let them be
as I do have plenty anyway.


You would be well ahead to eBay them or perhaps make a Christmas gift
of them to a Black church (or any other if such exists) with a
Hammond/Leslie. They are just a gross little tube AFAIAC.

The Marantz 8B and 5 are worth careful study as are the GEC designs
from the later app notes (Radford used these designs) and the early
all triode VTLs. Really all triode designs are more easy to get right
and sound very good. Pentode designs are harder to get really right.

If you absolutely insist on the stinky pentode-triode circuit get the
Van Alstine paper from the library and copy the input network which is
a vast improvement to that of the original ST70.


To my ears Van Alstine's low-frequency-filtering input circuit made a
modified Dynaco ST-70 sound worse.

The advantage of the combo triode/pentode driver tube chiefly fell to the
manufacturer, IMHO, in terms of lower parts count.

Personally, I'd look for a more symmetrical circuit, with triode phase
splitter and drivers. A few more parts, but capable of more pleasing
performance.

Jon