Thinking about having a 211 SET amp built, anyone know of good schematics? - diyAudio
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Old 5th January 2008, 03:54 AM   #1
Glowbug is offline Glowbug  United States
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Default Thinking about having a 211 SET amp built, anyone know of good schematics?

I'm thinking about going to 211 monos in SET, but I don't know of any good schematics to start with...something preferably tube rectified would be nice, not too sure if DC heaters are used on 211's but I've had good luck with them on the SV811's...

Can anyone point me in the right direction?

Thanks
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Old 3rd August 2011, 12:23 PM   #2
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Bump for the zombie thread!

Same question really. A friend is passing a non-working but otherwise complete 211 amp to me. The amp was working, but died. It seems a fantastic opportunity to build a new circuit using the existing valves & iron.

So can someone point me towards a really good circuit?

Tia,

Fran
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Old 3rd August 2011, 03:59 PM   #3
MikeR is offline MikeR  United States
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Can't speak to how good it is but, I recall recently looking this one over.

Electra-Print.com 211 A2 Amplifer
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Old 3rd August 2011, 04:06 PM   #4
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I am going to do something similar to what George Tubelab did:

Let's show go on: Building Monster SE!
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Old 3rd August 2011, 10:36 PM   #5
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Thanks guys, good food for thought there. Apparently the amp sounded great but was a bit unreliable. I'm supposed to get it this weekend so I'll draw up the schematic and post it here.

Any other suggestions - I would only need around 5w or so, so I don't need to wring 30 or 40 watts out the amp....

Fran
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Old 4th August 2011, 03:44 AM   #6
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The question kinda comes off like can you suggest any cars I can buy/build with a V8 engine?



More info about the chassis, iron, supply voltages and current, and output iron sets a few limits - that and what type of application and performance you want...

The drive circuit is very important with a 211... so start by thinking about what you will use in that hole?

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Old 4th August 2011, 11:33 PM   #7
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Quote:
Originally Posted by bear View Post
The question kinda comes off like can you suggest any cars I can buy/build with a V8 engine?



More info about the chassis, iron, supply voltages and current, and output iron sets a few limits - that and what type of application and performance you want...

The drive circuit is very important with a 211... so start by thinking about what you will use in that hole?

_-_-bear

Thanks Bear - you are of course correct - when I get my hands on the amp this weekend I will have more info. I didn't know about the importance of the driver circuit either - good to know.


Fran
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Old 4th August 2011, 11:56 PM   #8
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Hello

Here is one if you like it.
Goliath 211 single ended versterker (deel 3)
I'm in process to collect the parts for a GM70. I know at the beginning how confused I was which way to go....
At first you have decided about the parts U want to use, also 2 stage, 3 stage, inter stage transformer or with out etc.
After start to collect the parts. That way you can avoid to spend money on parts later they hold dust on the shelf etc.
The parts for these toys are not cheap!

Greetings gabor
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Old 7th August 2011, 07:13 PM   #9
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Well, I picked up the amp today. Substantial piece of kit alright. The amp is not working, some of the heaters aren't working, and there is a good bit of burning around the restifiers used for the heaters.It looks like the bridges are undersized or underheatsinked for what they were asked to do - you can see them in one of the pics below with the heatsink removed. The driver circuit is on a PCB and all the passives there look OK (except those heater rectifiers).

The driver circuit uses 2 x 12ax7, 3 x 12at7 and a 5681 I think. Those 211 valves are frickin' huge!!! All the main bits of hardware appear OK, so at least it won't (hopefully) cost much to fix. I also got a spare pair of 211s as well.

I took a few pics, but haven't even started to trace a circuit yet......


Fran
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Old 8th August 2011, 11:14 PM   #10
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I meant to say earlier that the amp is a Gamma Acoustics Rhythm amp. Theres so little out there about these amps - 1 or 2 mentions and thats it!

Anyway I did some more looking tonight and sorted some issues and found more. First off, the bridges for the heaters were cooked. There was 1 bridge for each 211 and then 1 for all the 12''7 valves. The 5687 runs off AC heaters. So I replaced all those and at least now all the heaters were working. So then I decided to check the B+. I get 1050V at the plates of the 211s (which seems correct). But I had only a couple of volts going to the PCB you see in the pic above which holds all the input and drivers. So anyway long story short, the 1050V B+ is filtered down using a massive 50K 50W resistor and it had gone open circuit. You can see a the big resistor in the middle pic above (theres 2 similar sized ones together in the pic).

What the hell could cause a 50W resistor like that to go open??!? Its a worry!!!

Also, I've carefully (visually) checked all the components on the PCB and other than the rectifiers, there's no sign at all of anything overheated.

So I'm guessing that the input/driver circuits are looking for about 300V or so. That would mean that if a 50K resistor provided a drop of ~700V, the resistor is throwing off ~11W or so.


Any comments? To quote pink floyd "is there anybody out there?"


Fran
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