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Old 4th February 2013, 06:44 AM   #2451
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Quote:
Originally Posted by amandarae View Post
Anyone have inputs to this? Thanks!

Abe
Microphonics were discussed in this thread very well, FAIR.
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Old 4th February 2013, 09:24 AM   #2452
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I haven't had microphonics problems with 26. But I will say that some pick up hum more than others. You need a few of them to select the quietest ones.
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Old 4th February 2013, 09:46 AM   #2453
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Hi all

cool work and progess! Just for the overkill or lap of luxury:

What about a mono version of this pre - seperate amplifier and seperate power suplly chassis?

BR, Joao
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Old 4th February 2013, 01:53 PM   #2454
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I've never found separating power supplies or monobloks made much impact on a properly designed amp/preamp. On the other hand, if I had to separate anything I'd have one PSU for the line stage with a posh rectifier like an AZ1 mesh, and one for the amp. That can be good and that's what I do. I'm not the only person to have said this is preferable to independent L and R supplies.
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Old 4th February 2013, 04:27 PM   #2455
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Quote:
Originally Posted by Wavebourn View Post
Microphonics were discussed in this thread very well, FAIR.
Thank you! I always wonder how loud someone pressurizes their listening room in order to affect the tubes with "microphonics" from airborne waves to become a considerable nuisance. Surely, we do not tap the preamp chassis as we listen to music.

I am doing it in my build, but I just cannot comprehend the point of doing it really to be honest. I had experience with 76( in fact one time I had 40 pieces on hand of 76 tubes to choose from) tubes and it is always the tube, not the construction of the chassis that matters if microphonic noise is a concern. You can lift the chassis up, use mass loading, decoupling, etc. and it would not matter. Replace the tube, problem solved!

Thanks again!
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Old 4th February 2013, 08:56 PM   #2456
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It is not about tapping the amp. It is about feedback that adds colorations. I found that epithets of guitarists about sound of tubes correlates well with how their microphonic effect sounds.
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Old 5th February 2013, 03:50 AM   #2457
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Quote:
Originally Posted by Wavebourn View Post
It is not about tapping the amp. It is about feedback that adds colorations. I found that epithets of guitarists about sound of tubes correlates well with how their microphonic effect sounds.
Thank you! Thanks for explaining it to me.

Abe
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Old 5th February 2013, 09:25 AM   #2458
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Quote:
Originally Posted by andyjevans View Post
I've never found separating power supplies or monobloks made much impact on a properly designed amp/preamp. On the other hand, if I had to separate anything I'd have one PSU for the line stage with a posh rectifier like an AZ1 mesh, and one for the amp. That can be good and that's what I do. I'm not the only person to have said this is preferable to independent L and R supplies.
Good answer, yes indeed. Experimented in the past with power supplies for the stages with the same phasing (preamp with inbuild phono & line). Compared to the dual mono version it sounded musically closer...

The other hand, building amps (especially power amps) with transformered interstage coupling it becomes physically heavy and seperate chassis brings relief.

BR, Joao
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Old 6th February 2013, 04:22 PM   #2459
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I have a couple of questions:

-About AZ1 hybrid graetz recitfiers, why the first cap is with so small value 0,1-3.3uF when AZ1 datasheets max. value is 60uF? I ask because if I use small 1st cap simulating with psud2 I will need a lot of caps?

-About #26 lineamp is necessary grid stopper & grid leak resistor, I ask because after the OPTs I want to use TVC at the output, I think is not necessary, right?
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Old 6th February 2013, 05:10 PM   #2460
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Quote:
Originally Posted by merlin el mago View Post
-About #26 lineamp is necessary grid stopper & grid leak resistor, I ask because after the OPTs I want to use TVC at the output, I think is not necessary, right?
I haven't found that positioning TVC after OPT have significant effect. I have just tweaking my preamp with AVC, made by Tribute. I have tried at both position, the conventional position as volume control and the position which you mentioned before (I have tried this position inspired based on Thomas Mayer's idea). I found no difference impact (at least in my system). Maybe it's a matter of taste . One thing for sure the AVC made much improvement in my system. It's like night and day as I replaced my carbon potentiometer with it.

About the resistor I dont think that grid stopper is necessary but with your configuration I think you can't avoid grid leak resistor. As it called as "grid leak", it will protect your grid tube when 'sheet' happened (voltage leaking ).
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