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Old 8th September 2005, 03:33 PM   #1
diyAudio Member
Join Date: Sep 2005
Default What kind of amp?

What kind of tube amp is this? I know that it is a 2x50w class a push/pull double tretrode 6R3S-1/GU-19-1 but not how it`s connected.
Here`s the schematics
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File Type: jpg audesschem2 small.jpg (99.7 KB, 891 views)
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Old 9th September 2005, 12:00 AM   #2
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Join Date: Oct 2004
Location: Adelaide South Oz
Pentode Amplifier (V1) driving a common cathode triode amplifier with direct coupled comcertina (cathodyne) phase splitter (V2) and push pull output tubes (tetrode connected).
The OUT2 and OUT1 connections are the feeds to the push and pull sides of the output transformer.
The NFB (Negative Feed Back) connection comes from the secondary of the output transformer (with other side of secondary going to earth)

The Output Tubes are new to me. The first tube is a bit of a mystery - all those shields on pin 2 and 7 (check EF86??), the common cathode/concertina splitter dual triode may be a 6SN7 (correct pin numbers).

It would seem to have a lot of gain so probably ran a lot of feedback to get a low output impedance (good damping factor).

Just my thoughts - from a quick look.

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Old 9th September 2005, 01:27 AM   #3
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Join Date: May 2005
Location: Pretoria, South Africa
The first tube is an EF86, the second an ECC85 or ECC88 (probably the latter). The power tubes I cannot find right now but I have seen them somewhere. I think they are some of these high power sweepers found in tv sets. Impressive for high power amplifiers but their transconductance can be a bit varying.

Unasked advice: Don't put this circuit high up on your list of future projects - one could do better with the twin triode as a Schmitt phase inverter directly coupled to the EF86, and tetrodes or pentodes in the power stage for high fidelity is not a good idea. Sorry.
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Old 9th September 2005, 08:54 AM   #4
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The first tube is a EF86 the 2nd a 6H6N? russian double tetrode, The output tubes are these below:
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File Type: pdf 6p3c data sheet.pdf (30.8 KB, 89 views)
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Old 9th September 2005, 09:40 AM   #5
argo is offline argo  Estonia
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Join Date: Feb 2001
Location: Estonia
It's an old Soviet time amplifier more know by the name of "Briboy" Audes also used to build them. During the years there has been numerous modifications made by several Russian hobbyist to make it sound better. While the output iron, output and driver tubes are good, the first modification would be to change the input gain tube and all the old capacitors.

Do you own this amp or intend to build from scratch?

Click the image to open in full size.
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Old 9th September 2005, 10:39 AM   #6
gianis is offline gianis  Greece
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Location: athens
Default 6P3C

This is the pic of the output tube , its double beam tetrode for audio use..6P3C-1 (Russian)
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File Type: jpg tube.jpg (34.1 KB, 672 views)
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Old 9th September 2005, 10:45 AM   #7
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I got my hands on one in 1996/97 but after a output tube imploded i forgot about it until now, i didn`t know how it was build or how to read the schematic but i`m modifying it right now with Mundorf capacitors to see if it`got any pontential at all.
So far so good
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Old 10th September 2005, 09:25 AM   #8
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Can anyone tell me how i can check the bias and were?
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Old 3rd October 2005, 06:37 PM   #9
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How do i change the NFB? is it only replacing the 6.8k resistor?
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Old 2nd November 2006, 10:10 AM   #10
Ansius is offline Ansius  Latvia
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Join Date: Mar 2006
Location: Latvia - Ogre
:d seams an old therd but:
first of all, get rid of thse 6Р3С (latin 6r3s) they are really unstable (u can't leave the amp un and not wach it - tubes tend to overheat and then melt, as well revire heating in paralel to be more stable). Aftre few week I will get one amp, and now I'm looking for altrenate schematic.
tbes are 6Ж32П (EF86), 6Н6П (I don't know analog, close mach would be 6AH4-GT, ECC88 could do but you have to redo the shematic then)
in attachmetnt is russian "Прибои" (latin "Priboi") inside picture. I'll poste wholl schematic as well. they had two versions 50W and 75W (only diference is in Plate supplay voltages).
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