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Old 24th August 2008, 09:40 AM   #1
sarrisk is offline sarrisk  Greece
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Default 807 monoblocks

PSE 807 monoblocks is my latest project . I decided to build this pair of monoblocks in the summer of 2002.

Click the image to open in full size.

It was my decision to use the less known 807 tube, a tetrode whose features and sounds i was well aware of, from a specific diy project (with one tube per channel ) made by Christos Spathopoulos.

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The whole construction is hard wired with the only exception of small board for the power supply capacitors. All the most critical path of amplifier have been wired using silver-teflon cables (especially the high voltage paths).

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The use of a NOS pair of RCA 807s tubes has improved a lot the clearness instead of the Westing House 807s i used before. The driving section uses the 12ΑΤ7 and the pre amp is the PV10A conrad-johnson.

find out more here : http://sarris.info/main/en/pset807

costas
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Old 25th August 2008, 05:10 PM   #2
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Nice looking amplifier! I have always had a nice warm corner in my heart reserved for the 807, as of now I have 16 NOS and growing over time... at least as they remain somewhat "undiscovered" and cheap. Out of curiosity what kind of power are you getting out of it?

Cheers

James
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Old 25th August 2008, 07:21 PM   #3
kmaier is offline kmaier  United States
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Odd, never thought of the 807 as undiscovered... my Dad used them in his power amplifier back in the 1950's. I would agree that the Westinghouse versions weren't that great... usually made in Canada and the plate cap had a spline pattern on it.

One thing to look for on NOS versions... the internal structure on the earlier ones had ceramic supports top and bottom... later manufacturing changes deleted these, so even with NOS versions there are some better than others.

In short, the 807 is a nice tube, but they suffer from fragile screens and can have a short life if the screens are pushed a bit too hard. Nice work on the amp.... I also use AutoCad for schematic and chassis layout.

Regards, KM
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Old 25th August 2008, 08:23 PM   #4
sarrisk is offline sarrisk  Greece
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thanks !
this amp works in a tetrode connection (about -15.5 Volts in Grid ) and according to my estimations it has about 16 -18 watt output power.
These babies sounds really pretty ! (clear voices and excellent mid - freq tone ! ) I combine them within a pair of a BL horn speakers and i enjoy every minute of listening !

costas
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Old 25th August 2008, 10:56 PM   #5
sarrisk is offline sarrisk  Greece
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Quote:
Originally posted by kmaier
In short, the 807 is a nice tube, but they suffer from fragile screens and can have a short life if the screens are pushed a bit too hard. Nice work on the amp.... I also use AutoCad for schematic and chassis layout.

Regards, KM
i agree. that was a problem with Westinghouse and some pairs of CVC (Chelmer valve). Now i m using two pairs of NOS RCA 807 and i have no problems.


costas
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Old 25th August 2008, 11:11 PM   #6
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I guess undiscovered wasn't really the correct word choice, you are right about that. Though they sound just as good or better the 6L6 types and 6550 types seem to steal all the lime-light. There isn't an abundance of DIYer's or pro companies that use them in their designs. Thankfully due to this, and the fact that they where made by the boat load, the price has been kept low. I am afraid though that as 6L6's reach up to $100 plus a pair or more the 807's will slowly start to rise in price as well.

Cheers

James
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Old 26th August 2008, 12:05 AM   #7
sarrisk is offline sarrisk  Greece
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Quote:
Originally posted by JPeitzman
I guess undiscovered wasn't really the correct word choice, you are right about that. Though they sound just as good or better the 6L6 types and 6550 types seem to steal all the lime-light. There isn't an abundance of DIYer's or pro companies that use them in their designs. Thankfully due to this, and the fact that they where made by the boat load, the price has been kept low. I am afraid though that as 6L6's reach up to $100 plus a pair or more the 807's will slowly start to rise in price as well.

Cheers

James

Thats right ! and i have to quote that : As i m listening tubes during last two decades i noticed that manufactures chose classic audio tubes ( EL34, 6550, KT88 etc) for their designs. Don't forget that 807 is a classic power output tube designed for transmitters...
It is difficult to make a design using this tube as an AF output. ( these designs suffer from noise produced by heaters, or from a careless design in power supply... ). Using of chocks or interstage transformers solve these problems but increases cost ( e.g WAVAC) and make the whole construction more complicated.
I think that this is the reason that remain "undiscovered.."

regards
costas

P.S. perhaps they produce the most smoothly and sweet mid - freq i ever heard !
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Old 26th August 2008, 12:49 AM   #8
Jeb-D. is offline Jeb-D.  United States
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Quote:
this amp works in a tetrode connection (about -15.5 Volts in Grid ) and according to my estimations it has about 16 -18 watt output power.
I'ts a breath of fresh air to see that somebody isn't afraid to wire the 807 in tetrode.

There are too many weakling, triode-wired, 807 amps floating around.

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Old 26th August 2008, 01:54 AM   #9
fredex is offline fredex  New Zealand
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sarrisk
Nice looking amp congratulations. Ceramic top caps are cool too, I have some 807s with ceramic bases, Westinghouse I think.
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Old 26th August 2008, 10:22 AM   #10
oshifis is online now oshifis  Hungary
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Quote:
Originally posted by Jeb-D.
There are too many weakling, triode-wired, 807 amps floating around.

Here is one of them:

807 Tube Triode Connected
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