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Old 13th January 2013, 07:50 PM   #281
coils is offline coils  United States
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Im going to try that. Forgot to say that I have a BA3 in progress.
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Old 14th January 2013, 02:06 AM   #282
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My B- bias was 4.35 volts, and the B+ bias was 4.15 volts, putting in a 20k r219 equalized the B-and B+, and dropped the bias voltage to each device to around .400V. So I am going to let it set for two hours, and check the temps. I think it will be fine. Cant wait to hear it.
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Old 14th January 2013, 11:53 AM   #283
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Default Two channels ba1 working

Yesterday evening finished the second channel powerstage of ba 1.

A very little hum (in spite of more than 369.000uf in the powersupply).

1000va transformers

input signals are taken from gridpin of second tubesocket of Beard p100mkII.

One thing is for sure this is a complete different sounding amp than the Beard p100 that I have been used to for the last years.

I wil keep comparison reports for later.

The amount off subjective available power (3x 0.6 Amp) does certainly not disapoint! Especially not after everything I read here about needed power.
But it needs more for my old b w 801 s with only 86 db sensitivity

As it is hardwired I left space to put two extra mosfets in.

In two more weeks or so i will finish another two channels and make this a balanced amp. Which will give me 8x0.6amps


AND HERE IS A QUESTION since heatsinks are probably larger than in the original it is not running very hot. So can someone advise me whats the best and simpel way to raise bias a little.
And what will be the maximum current per device and by which itīs lifespan wonīt be significantly shorted. (providing I stick to the 5 seconds putting hand on heatsink test)

All in all adding mosfets, making it balanced, raising bias, and later on doubling the efficiency as Nelson spoke about will make this also for my low sensitivity speaks a VERY NICE amp.
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Old 14th January 2013, 03:48 PM   #284
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Burning Amplifier BA-1

So my heatsinks are to small, i knew i was playing with fire using 6 pairs! Still 65 c even with lower bias. ZM, putting the amp on end did help to cool it, but I am going back to the drawing board. I have an under biased f5 c. That will go in this chassis.

Alettagla, you can parallel another source resistor, maybe 10R.
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Old 14th January 2013, 04:19 PM   #285
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Thank you coils was hoping for another solution since it took me quit some trouble matching al the source resistors.

When I know what is the maximum bias per mosfet withoud shortening its lifespan to much just changing source resistors should even for me be a simple calculation.

Anyway in your case why not lower bias even more Im right now lisstening with a total of 1,8 amp bias and its stil playing very nice. Allthough itīs running out off breath with more serious listening levels but when you have about 6db more sensitive speaks al might be well.
And then when Nelson tells us the secret of how efficiency can be doubled ..... All mightbe fine

At least you have heard some single ended class A
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Old 14th January 2013, 04:43 PM   #286
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Quote:
Originally Posted by coils View Post
Burning Amplifier BA-1

So my heatsinks are to small, i knew i was playing with fire using 6 pairs! Still 65 c even with lower bias. ZM, putting the amp on end did help to cool it, but I am going back to the drawing board. I have an under biased f5 c. That will go in this chassis.

Alettagla, you can parallel another source resistor, maybe 10R.
I hope that you had some proper clearance between heatsink bottom end and surface

say that 50mm is sufficient ; fact that you're not seeing that on commercial amps is simple - who would ship and sell amps with 50mm tall legs

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Old 14th January 2013, 04:48 PM   #287
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Quote:
Originally Posted by coils View Post
So my heatsinks are to smal....
two of your heatsinks would normally be used for a standard F5 stereo amp
or might do a balanced stereo
but you have 2 channels of BA-1 on one heatsink
I suspect to make a balanced stereo amp
well, two heatsinks ought to work for a stereo amp, or one balanced mono amp

btw, if yours is a copy of Nelson original layout with 6 pairs, I suppose it was still meant to be mounted on two heatsink
meaning, a normal stereo chassis with two heatsinks would do one mono amp
but not very convenient for balanced, which I guess is one reason for the 3-pair option
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Old 14th January 2013, 08:20 PM   #288
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ZM, I agree on the clearance.

two of your heatsinks would normally be used for a standard F5 stereo amp
but you have 2 channels of BA-1 on one heatsink
I suspect to make a balanced stereo amp
well, two heatsinks ought to work for a stereo amp, or one balanced mono amp

This amp is not balanced, just 6 pairs deep, I'm the irrational one spoken of elsewhere. This chassis is now home to an f5 c. The BA is getting a bigger chassis. *
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Old 16th January 2013, 12:54 PM   #289
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Default adding an aleph current source

Hereīs a question,

I have two powerstages/bufferstages of ba 1 working. Two are being soldered together to make it a balanced version. Even then Iīm affraid I wonīt have enough power.

Well then I have been reading the zen 2 paper and here is my (novice) question.

Could I add pair of resistors,a cap and in this way add an Aleph current source. (details have to be worked out)

What are proīs and conīs of using Cheff de Gaars UGS module as frontend.
(I have boards and 2sj109BL in the drawer)And how wil it compared to bba3

(by the way wouldnīt a set up with the aleph current source and UGS module bring me close to the more commercial passlabs models...?)


Your advice is most welcom
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Old 11th February 2013, 12:41 PM   #290
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Default making my BA/1 more efficient

Hmm I have been patiently waiting for a response to the above question but since were no replies I started experimenting.

I tried to add an Aleph current source as it is implemented and explained in one of the ZEN papers.
(or at least what I understood from it)
That means from the output with a capacitor and resistor back to the base of the ztx450 biasing transistor. This resulted in a very unpleasant screaming occilation which, despite of several attemts I couldnīt stop.

Never mind we learn best from our mistakes. But right now Im stuck.

Nelson Pass explained to us in the beginning of this thread that in a later version he would explain to us a (novelty) way of how to double the efficiency of the BA1

Could someone please explain why adding an aleph current source doesnīt work or what I might have done wrong?

Or could perhaps Nelson himself already reveal how to double the efficiency of this amp?

Any ideas are most welcom
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