| Author |
Message |
Phil J.
Guest
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 Posted:
Fri Dec 31, 2004 10:50 pm Post subject:
Amp Advice |
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Hello all,
Overwhelmed with excitement over the low price I bought an old tube
amp from an antique store. Pictures of said amp are posted here:
http://www.yorku.ca/jaekl/files/amp/
As you can see it needs some work. Possibly three tubes need to be
inserted and a plug needs to be connected to the power input. I
thought the brand was Hammond and was planning to contact them, but
that is the brand of the the transformer, not the amp. I cannot find
a brand name on the amp, which makes me think an amateur enthusiast
might have originally put this together.
I'm quite the overzealous novice and I'd really like to get it to
work, but I don't know what tubes I need or how I can connect an input
or speaker (assuming this is an amp and not a preamp).
Any advice would greatly be appreciated. I can add pictures of the
inside of the box if necessary.
Thanks!
Phil
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Chris Hornbeck
Guest
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| Posted:
Fri Dec 31, 2004 11:16 pm Post subject:
Re: Amp Advice |
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On 31 Dec 2004 09:50:38 -0800, jaekl@yorku.ca (Phil J.) wrote:
| Quote: | Overwhelmed with excitement over the low price I bought an old tube
amp from an antique store. Pictures of said amp are posted here:
http://www.yorku.ca/jaekl/files/amp/
As you can see it needs some work. Possibly three tubes need to be
inserted and a plug needs to be connected to the power input. I
thought the brand was Hammond and was planning to contact them, but
that is the brand of the the transformer, not the amp. I cannot find
a brand name on the amp, which makes me think an amateur enthusiast
might have originally put this together.
|
Looks like a ham modulator. That's *not* a power cord. Do not
put an AC plug on it.
Are those tubes 1625's? One is gassy.
Good fortune,
Chris Hornbeck
"They'd meet at the Tout Va Bien."
-JLG, _Bande a part_, 1964 |
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John Stewart
Guest
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| Posted:
Sat Jan 01, 2005 12:28 am Post subject:
Re: Amp Advice |
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"Phil J." wrote:
| Quote: | Hello all,
Overwhelmed with excitement over the low price I bought an old tube
amp from an antique store. Pictures of said amp are posted here:
http://www.yorku.ca/jaekl/files/amp/
As you can see it needs some work. Possibly three tubes need to be
inserted and a plug needs to be connected to the power input. I
thought the brand was Hammond and was planning to contact them, but
that is the brand of the the transformer, not the amp. I cannot find
a brand name on the amp, which makes me think an amateur enthusiast
might have originally put this together.
I'm quite the overzealous novice and I'd really like to get it to
work, but I don't know what tubes I need or how I can connect an input
or speaker (assuming this is an amp and not a preamp).
Any advice would greatly be appreciated. I can add pictures of the
inside of the box if necessary.
Thanks!
Phil
|
The transformer appears to be one of the Hammond 1700 Series.
It could be either an output transformer or a modulation transformer.
Probably an output since on checking my old catalogues it appears Hammond
did not put a modulation transformer in the 1700 package.
What is the number stamped on the nameplate?
If it is a 5 digit number it may be a special.
Looks like you will need a power supply to run this beast.
The circuit may be a Williamson since many were built with a separate
power supply.
The tubes are probably 807's which were common in Williamson amps.
The unfilled sockets appear to be meant for loctal tubes.
If the circuit is a Williamson the tubes would be double triodes such as
the 7F7 & 7N7.
The connector on the end is a very old mike connector.
The chassis is one of the old Hammond zinc plated steel variety, NLA.
A clear photo of the underside so we could see the wiring would help a
lot.
Some of your photos are out of focus.
If that transformer is what I think & not cooked it would be the starting
point for a fine amp.
Cheers, John Stewart |
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Fred Gilham
Guest
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| Posted:
Sun Jan 02, 2005 5:33 am Post subject:
Re: Amp Advice |
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Well, it's not a Williamson. There's a pic of the underside called
"circuitry" (not circuitry.jpg) which gives a pretty good look at the
transformer hookup. Unfortunately it doesn't show the markings by the
output side of the amp, which would probably tell what the output
impedance is. Anyway the plate wires (from the caps on the tubes) are
hooked to the transformer, and it looks like the screens might be
hooked to the plate connections through resistors. But you can't
actually see where the wires coming off the plate connections to the
transformer go.
The brown zipcord coming out of the amp is apparently supposed to be
hooked to a speaker. It is most definitely NOT a power input! The
orange wire hooked to pin 1 of the transformer along with one side of
the zip cord is for negative feedback.
The two 1/4 in. plugs on either side might be for measuring the bias
current of the output tubes but it's hard to tell. They do seem to be
connected directly to what could be the cathode pin on the tube
sockets.
The octal plug on the side by the transformer is for power. The amp
will need a supply of probably something in the neighborhood of 500 V
and another of 300V, and a 6.3V or 12.6V filament power supply. So
the amp is missing the entire power component, which probably came on
a seperate chassis.
--
Fred Gilham gilham@csl.sri.com
99% of lawyers give the rest a bad name. -- Steve Wright |
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John Stewart
Guest
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| Posted:
Sun Jan 02, 2005 5:41 am Post subject:
Re: Amp Advice |
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Fred Gilham wrote:
| Quote: | Well, it's not a Williamson. There's a pic of the underside called
"circuitry" (not circuitry.jpg) which gives a pretty good look at the
transformer hookup.
|
I was unable to open the 'circuitry' file. Not sure in what format but
all I get is a huge mess of strange characters. If possible, could you
convert it to a GIF or JPG so I could have a look?
Thanx, JLS
| Quote: | Unfortunately it doesn't show the markings by the
output side of the amp, which would probably tell what the output
impedance is. Anyway the plate wires (from the caps on the tubes) are
hooked to the transformer, and it looks like the screens might be
hooked to the plate connections through resistors. But you can't
actually see where the wires coming off the plate connections to the
transformer go.
The brown zipcord coming out of the amp is apparently supposed to be
hooked to a speaker. It is most definitely NOT a power input! The
orange wire hooked to pin 1 of the transformer along with one side of
the zip cord is for negative feedback.
The two 1/4 in. plugs on either side might be for measuring the bias
current of the output tubes but it's hard to tell. They do seem to be
connected directly to what could be the cathode pin on the tube
sockets.
The octal plug on the side by the transformer is for power. The amp
will need a supply of probably something in the neighborhood of 500 V
and another of 300V, and a 6.3V or 12.6V filament power supply. So
the amp is missing the entire power component, which probably came on
a seperate chassis.
--
Fred Gilham gilham@csl.sri.com
99% of lawyers give the rest a bad name. -- Steve Wright |
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BFoelsch
Guest
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| Posted:
Sun Jan 02, 2005 6:12 am Post subject:
Re: Amp Advice |
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|
"John Stewart" <jh.stewart@sympatico.ca> wrote in message
news:41D5A874.A22D6666@sympatico.ca...
| Quote: | "Phil J." wrote:
Hello all,
Overwhelmed with excitement over the low price I bought an old tube
amp from an antique store. Pictures of said amp are posted here:
http://www.yorku.ca/jaekl/files/amp/
As you can see it needs some work. Possibly three tubes need to be
inserted and a plug needs to be connected to the power input. I
thought the brand was Hammond and was planning to contact them, but
that is the brand of the the transformer, not the amp. I cannot find
a brand name on the amp, which makes me think an amateur enthusiast
might have originally put this together.
I'm quite the overzealous novice and I'd really like to get it to
work, but I don't know what tubes I need or how I can connect an input
or speaker (assuming this is an amp and not a preamp).
Any advice would greatly be appreciated. I can add pictures of the
inside of the box if necessary.
Thanks!
Phil
The transformer appears to be one of the Hammond 1700 Series.
It could be either an output transformer or a modulation transformer.
Probably an output since on checking my old catalogues it appears Hammond
did not put a modulation transformer in the 1700 package.
What is the number stamped on the nameplate?
If it is a 5 digit number it may be a special.
Looks like you will need a power supply to run this beast.
The circuit may be a Williamson since many were built with a separate
power supply.
The tubes are probably 807's which were common in Williamson amps.
The unfilled sockets appear to be meant for loctal tubes.
If the circuit is a Williamson the tubes would be double triodes such as
the 7F7 & 7N7.
The connector on the end is a very old mike connector.
The chassis is one of the old Hammond zinc plated steel variety, NLA.
A clear photo of the underside so we could see the wiring would help a
lot.
Some of your photos are out of focus.
If that transformer is what I think & not cooked it would be the starting
point for a fine amp.
Cheers, John Stewart
|
I would bet my boots that this is the "American Williamson," sans power
supply, as shown on page 509 of Oliver Read, "The Recording and Reproduction
of Sound." Everything I can see agrees, right down to the loctal sockets for
the 7N7s.
As you said, if the transformer is good, a beginner could do a lot worse
than restoring this amp. I am well aware that it is susceptible to
improvement, particularly in the LF stability department, but even with its
warts, it is a whole lot better than some of the esoteric designs running
around today.
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John Stewart
Guest
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| Posted:
Sun Jan 02, 2005 7:00 am Post subject:
Re: Amp Advice |
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|
BFoelsch wrote:
| Quote: |
The transformer appears to be one of the Hammond 1700 Series.
It could be either an output transformer or a modulation transformer.
Probably an output since on checking my old catalogues it appears Hammond
did not put a modulation transformer in the 1700 package.
What is the number stamped on the nameplate?
If it is a 5 digit number it may be a special.
Looks like you will need a power supply to run this beast.
The circuit may be a Williamson since many were built with a separate
power supply.
The tubes are probably 807's which were common in Williamson amps.
The unfilled sockets appear to be meant for loctal tubes.
If the circuit is a Williamson the tubes would be double triodes such as
the 7F7 & 7N7.
The connector on the end is a very old mike connector.
The chassis is one of the old Hammond zinc plated steel variety, NLA.
A clear photo of the underside so we could see the wiring would help a
lot.
Some of your photos are out of focus.
If that transformer is what I think & not cooked it would be the starting
point for a fine amp.
Cheers, John Stewart
I would bet my boots that this is the "American Williamson," sans power
supply, as shown on page 509 of Oliver Read, "The Recording and Reproduction
of Sound." Everything I can see agrees, right down to the loctal sockets for
the 7N7s.
As you said, if the transformer is good, a beginner could do a lot worse
than restoring this amp. I am well aware that it is susceptible to
improvement, particularly in the LF stability department, but even with its
warts, it is a whole lot better than some of the esoteric designs running
around today.
|
Thankyou very much for the underside view. I have had a quick look & what I see
still makes me think it is a Williamson. The early cues were the amp without
power supply & the suspected tube line up. It is a bit cluttered as seen here so
if it were me I would remove the transformer for testing & if OK start with a
fresh chassis. The transformer underside is stamped 10000 ohms & that would be
correct for the triode version of the Williamson. I have two similar
transformers from that era here & both have that 5-terminal secondary. I will
pull the data out tomorrow morning to figure out what speaker impedance the
builder has hooked up for. Interestingly, Hammond still uses that 5-lead out on
the secondaries of their better class output transformers.
There is a better than even chance that many of the under chassis parts are aged
& defective. It is not a commercial build so may include some bad solder joints.
Still, appears to be an interesting & valuable find.
Cheers to all, John Stewart |
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John Stewart
Guest
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| Posted:
Sun Jan 02, 2005 7:11 am Post subject:
Re: Amp Advice |
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Depending on the physical dimensions the output transformer could be a Hammond 1770
or 1772. The 1770 is the larger of the two. Both those & many others are listed in
the Hammond section of my 1960 Electrosonic Catalogue.
Cheers, John Stewart |
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Brian McAllister
Guest
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| Posted:
Sun Jan 02, 2005 8:25 am Post subject:
Re: Amp Advice |
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On Sat, 01 Jan 2005 19:41:56 -0500, John Stewart
<jh.stewart@sympatico.ca> wrote:
| Quote: |
I was unable to open the 'circuitry' file. Not sure in what format but
all I get is a huge mess of strange characters. If possible, could you
convert it to a GIF or JPG so I could have a look?
Thanx, JLS
|
Save it and re-name it to circuitry.jpg or any .jpg file, and it will
open.
Brian McAllister
Sarasota, Florida
email bkm at oldtech dot net and@hope.thespambots.die |
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Brian McAllister
Guest
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| Posted:
Sun Jan 02, 2005 8:25 am Post subject:
Re: Amp Advice |
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On Sat, 01 Jan 2005 21:00:20 -0500, John Stewart
<jh.stewart@sympatico.ca> wrote:
| Quote: | Thankyou very much for the underside view. I have had a quick look & what I see
still makes me think it is a Williamson.
|
I agree. The output balancing pot and cathode metering jacks are
another dead giveaway.
Brian McAllister
Sarasota, Florida
email bkm at oldtech dot net and@hope.thespambots.die |
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Brian McAllister
Guest
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| Posted:
Sun Jan 02, 2005 8:25 am Post subject:
Re: Amp Advice |
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On Sat, 1 Jan 2005 20:12:37 -0500, "BFoelsch"
<BFoelsch@comcast.ditch.this.net> wrote:
| Quote: | As you said, if the transformer is good, a beginner could do a lot worse
than restoring this amp. I am well aware that it is susceptible to
improvement, particularly in the LF stability department, but even with its
warts, it is a whole lot better than some of the esoteric designs running
around today.
|
There is also much literature available that would allow an amateur to
to make improvements that were suggested
Brian McAllister
Sarasota, Florida
email bkm at oldtech dot net and@hope.thespambots.die |
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Guest
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| Posted:
Mon Jan 03, 2005 6:29 am Post subject:
Re: Amp Advice |
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Most scratchbuilt tube hobby specials from that era were Williamsons,
probably 10:1. Many oldtimers at hamfests and antique radio meets still
call any old tube audio amp a Williamson. The Williamson was the most
cost effective, gave decent sound and was close to idiotproof. Most
were cathode biased as before solid state rectifiers bias voltage was a
pain in the ass.
Their failing by modern standards, is lack of power. The true
Williamson uses the 6L6, KT88 or 807/1625 interchangeably (different
sockets...) and is roughly a 20 to 25 watt amp. If it is ultralinear it
may give 35-40 or so but then, it's not a true Williamson. I think it's
a Hafler-Keroes. |
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John Stewart
Guest
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| Posted:
Mon Jan 03, 2005 4:00 pm Post subject:
Re: Amp Advice |
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calcerise@hotmail.com wrote:
| Quote: | Most scratchbuilt tube hobby specials from that era were Williamsons,
probably 10:1. Many oldtimers at hamfests and antique radio meets still
call any old tube audio amp a Williamson. The Williamson was the most
cost effective, gave decent sound and was close to idiotproof. Most
were cathode biased as before solid state rectifiers bias voltage was a
pain in the ass.
Their failing by modern standards, is lack of power. The true
Williamson uses the 6L6, KT88 or 807/1625 interchangeably (different
sockets...) and is roughly a 20 to 25 watt amp. If it is ultralinear it
may give 35-40 or so but then, it's not a true Williamson. I think it's
a Hafler-Keroes.
|
Actually, when referring to the 'Williamson' we are really talking about a
particular configuration of tubes within the amplifier strip. That would be
an input triode followed by a triode phase splitter (concertina), then a PP
triode driver & on into the PP triode output. Seems to me Williamson used
KT66's in his original. He specified an OT somewhat better in respect to
leakage inductance & primary inductance than was common at the time. That
way, more NFB could be used before the onset of instability. At the time
all that resulted in quite an improvement in sound fidelity.
The original Williamson used separate tubes at each position. It didn't
take long for some to realize that double triodes such as the 6SL7
(input/phase splitter) & 6SN7 (driver) could be used to advantage. Many
were built with 807's as the output since these were available at very low
cost on the surplus market. When UL transformers became available many
Williamsons were modified in order to double the available power. But the
tube configuration was still a Williamson.
Another common configuration would be the Mullard 5-20. It used a low noise
pentode such as the EF86 or Z729 front end. That was followed by a cathode
coupled phase splitter, usually a double high mu triode. Far as I know,
most used some kind of beam tube as the output connected UL style, although
you could use them as triodes just as well.
The third common configuration would be that used by Dynaco. With the
introduction of high G power tubes such as the EL34, KT88 & 6550 it was
possible to build an amp with enough gain after NFB with one less stage
than the Willianson. The front end often was a 6AN8 pentode section
followed by the included medium mu triode as the phase splitter. This then
ran into any of the listed power tubes in PP, most often in the UL
connexion. One less stage of gain & phase shift resulted in considerably
improved stability with NFB.
Some think that Hafler & Keroes invented the UL connexion. I've seen
reference to that hookup in some 1930's papers. Not sure where that is now.
If I find that I will post it sometime.
There were a number of other configurations such as the McIntosh,
Circlotron & some OTL's, but not too common with the home builder for
various reasons. One I like very much is Norman Crowhursts Twin Coupled
Amp. In respect to bang-for-a-buck, it does better than most tube amps.
Cheers, John Stewart
BTW, I'm one of those oldtimers, but I've never been to a hamfest or
antique radio meet. But I was there when these amps were popular & built
more than my share. Still doing that & you can read me in Glass Audio &
AudioXpress. JLS |
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