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211 SE power amp
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Author:  mwhouston [ 30 Sep 2013, 18:04 ]
Post subject:  Re: 211 SE power amp

Geek wrote:
Suncalc wrote:
mwhouston wrote:
The big one is 600V-0-600 @ 400mA
Hmmm....

This presents a little issue. You see, when you said a 1200v transformer, I assumed 1200-0-1200 and designed an amplifier that requires a B+ of 1350V. Obviously this transformer won't fit the bill.


If you use a FWB, you can draw up to ~180mA, I think it goes....

I may have mentioned a few times that I am trying to use up existing parts in most builds of late and going forward. To that end I would like to use this power tranni. It was always my intention to use SS rectification. The design I was going to build used banks of diodes in series to handle the back EMF and banks of caps in series with a restive ladder to handle to 1200V. The resistive ladder ensured the 1200V was spread over all caps evenly.

With the SS rec. section we should get little voltage drop. I realise with tube rec. I would get 50 to 100V voltage loss especially if we had to use two rec. tubes to handle the HT.

When I have been use to 2.5W and 6W amps I'm sure this amp will be a big step-up in power. I'm currently using my tube and chip amp (Number. 9) with its 80W pc. Funny most of the time I don't play any louder? I'm trying to locate the OPTs. I had some wound but they are useless because the dills forgot to air gap them. But I feel I ordered some Edcors to replace them. I just need to find them. Sorry to through a spanner in the works.

Author:  wolfdog428 [ 30 Sep 2013, 18:42 ]
Post subject:  Re: 211 SE power amp

The power transformer can be used for the amp. I would use a bridge. The CT of the transformer can be un used or used for lower B+. I use 1100V 400ma CT Edcor power transformers for my PP 813 Amps. I run them with a tube bridge rect using damper tubes and the center tap is used to supply the lower voltages never had a prolbem. I have also used this on a 211 PP Amp I built a few years back. just be aware you will get over 1600 volts if you use the transformer with a bridge rect. Edcor only Hi pot test the transformers to 1000 volts. I run my output transformers at 1100 volts on my 813 PP amps and have never had a prolbem with Edcors! That being said I have had outpot transformers fail in the 813 amps that cost $600 and they were custome made. I will not name names.

Author:  Suncalc [ 30 Sep 2013, 19:47 ]
Post subject:  Re: 211 SE power amp

mwhouston wrote:
I may have mentioned a few times that I am trying to use up existing parts in most builds of late and going forward. To that end I would like to use this power tranni.
Very well. Then tomorrow I will post the load line derivations and the schematic.

It is an SE design, 20W peak output into the power transformer (most probable 18W to 19W at the speaker), Ds=0.3%/W. Each tube is biased to -76V. The static operating point is 1259V@59mA, peak plate dissipation 74.3W.

Something to remember when you are doing your layout, each power tube (between plate dissipation and filament load) will be dissipating almost 100W. You're going to want a clear area around each tube of about 4" radius minimum to ensure adequate convection cooling. The tubes should probably not be closer than about 5" to each other.

I will also post some tidbits about working with voltages in this range.

Author:  mwhouston [ 30 Sep 2013, 20:39 ]
Post subject:  Re: 211 SE power amp

Suncalc wrote:
mwhouston wrote:
I may have mentioned a few times that I am trying to use up existing parts in most builds of late and going forward. To that end I would like to use this power tranni.
Very well. Then tomorrow I will post the load line derivations and the schematic.

It is an SE design, 20W peak output into the power transformer (most probable 18W to 19W at the speaker), Ds=0.3%/W. Each tube is biased to -76V. The static operating point is 1259V@59mA, peak plate dissipation 74.3W.

Something to remember when you are doing your layout, each power tube (between plate dissipation and filament load) will be dissipating almost 100W. You're going to want a clear area around each tube of about 4" radius minimum to ensure adequate convection cooling. The tubes should probably not be closer than about 5" to each other.

I will also post some tidbits about working with voltages in this range.

Suncalc: Your theoretical distortion figure is very low. 0.3% and is better than my 4SU preamps at 0.6%!! Golly!! I have just discovered I have 10H 200mA Hammond chokes. I would assume I can use this in the amp. I have two but I would like to hold one over for another amp.

I'm going to have another attempt at locating the OPTs. Thanks so far.

Author:  RossD [ 01 Oct 2013, 14:04 ]
Post subject:  Re: 211 SE power amp

Those 211 tubes mean business with those high voltages!

While looking at craigslist, I found a Amperex 6960a for sale for a couple hundred bucks. Intrigued, I looked at the data sheet:
12.6 volt filament with 33 amps current!!!!
Max ratings for Class B:
DC Plate Voltage: 7.2k V,
DC Plate Current: 2.2A,
Plate Input: 14kW,
Plate Dissipation: 6kW.
:hot: :hot: :hot: :hot:

Reading farther into the data sheet, it states it's water cooled! Down right makes your 211 tube looks like a pussycat!

Your project looks like a good one. I know you'll keep us informed. Good Luck!

Author:  mwhouston [ 01 Oct 2013, 17:39 ]
Post subject:  Re: 211 SE power amp

RossD wrote:
Those 211 tubes mean business with those high voltages!

While looking at craigslist, I found a Amperex 6960a for sale for a couple hundred bucks. Intrigued, I looked at the data sheet:
12.6 volt filament with 33 amps current!!!!
Max ratings for Class B:
DC Plate Voltage: 7.2k V,
DC Plate Current: 2.2A,
Plate Input: 14kW,
Plate Dissipation: 6kW.
:hot: :hot: :hot: :hot:

Reading farther into the data sheet, it states it's water cooled! Down right makes your 211 tube looks like a pussycat!

Your project looks like a good one. I know you'll keep us informed. Good Luck!

Well I hope my pussy will roar and not just meow.

Author:  mwhouston [ 04 Oct 2013, 02:17 ]
Post subject:  Re: 211 SE power amp

It appears I do not have (or cannot find) the OPTs for the 211 amp. Suncalc make some suggestions for OPTs and I'm thinking Edcors (model please) and an equivalent Hammonds. Also a company called Dyne here will wind most trannies. If I can get the specs early that will help. Whether they come from Edcor or Dyne it will take me six weeks to get them.

Author:  Geek [ 04 Oct 2013, 03:43 ]
Post subject:  Re: 211 SE power amp

What impedance does it need?

I had the Edcor EM0774 designed for the 845... it's 9K to 8R and can handle the SE bias. It's built on their largest core. Would save you the design fee if you could use it.

Brian rated it 40Hz-20KHz, but I measured it taking 22Hz just fine at 22W.

Cheers!

Author:  mwhouston [ 04 Oct 2013, 05:32 ]
Post subject:  Re: 211 SE power amp

Geek wrote:
What impedance does it need?

I had the Edcor EM0774 designed for the 845... it's 9K to 8R and can handle the SE bias. It's built on their largest core. Would save you the design fee if you could use it.

Brian rated it 40Hz-20KHz, but I measured it taking 22Hz just fine at 22W.

Cheers!

Happy with the Edcor. It's up to Matt to provide some specs. If he thinks it's in spec and the price is reasonable I'm OK with that. Shipping it here will be expensive but it would be expensive from Edcor anyhow. Let's see what Matt comes back with. Do you know what the idle current rating is? Is it new or used?

Author:  Suncalc [ 04 Oct 2013, 07:56 ]
Post subject:  Re: 211 SE power amp

Sorry for the delay. I'll get the whole thing posted tonight (on my side of the world ;) ).

Currently I'm thinking Edcor CXSE25-8-10k. The operating point is only at 59mA so current and core saturation is no problem. I'm not worried about the voltage because the dielectric breakdown on the wire that Edcor uses is well above 3000v. Even if their HiPot standard is not that high I think the outputs will be fine.

More later.

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