Why do all of the Fx-Amps have one shared PSU ?

I am currently in the build process of a F5Tv2 in one enclosure. I eitherbuild it now with one transformer (has two 25v windings) and one PSU feeding both channels or I need to buy another transformer.

I started to wonder...used the search engine, butcould not really find a chapter which explains why Mr. Pass suggests this setup where you use one bipolar PSU for both channels. I guess with very limited additional effort (VA of the x-former could stay the same, just more windings, additional rectifiers), all the Fx could as well have a dual-mono-setup.

But I guess he had good reasons not to go this route and instead suggesting one PSU for both channels. So, does this have a posoitive impact on sound (stiffer PSU) or simply Dual-Mono-Psu would not make a big difference ? Anyone has experience on this with the F5 and can give advise ?
 

woody

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2002-01-15 12:57 am
Tyrone Ga. U.S.A.
You might also think about this approach used in the A40. Some of the advantages of duel mono but only one transformer.
 

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I know...i was just looking for an excuse to save some $$$...

whatever

you'll save few bucks only if you stop thinking about "what if .... "

I solved that dilemma long ago - when I'm making power amp for my self , it's dual mono

if i don't have enough greenies for everything , I just prolong it , to collect everything
 

Mark Johnson

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2011-05-27 3:27 pm
Silicon Valley
Unfortunately the US hobbyist's first choice of transformer vendors, Antek, sells very VERY few transformers with four equal secondary windings. So the Pass A40 power supply design, which requires four secondaries (two for 88 VCT number 1, and two more for 88 VCT numner 2), is not feasible.

Antek-sourced hobbyists choose either two transformers to get four windings, or one doublesize transformer with two windings shared between stereo channels, or monoblock construction.
 

wdecho

Member
2014-10-28 11:45 am
I noticed the same thing with the F6 power supply. Commonly done on tube amp PS's. One thing to consider with Anek PS is that you can use smaller transformers 150VA or 200VA and stack them on top of each other. The same with the PS and then have 2 mono's essentially in one case. Most cases are tall enough where this can be done.
 
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Mark Johnson

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2011-05-27 3:27 pm
Silicon Valley
The schematic in post#9 gives armchair analysts a delightful opportunity to guess (or to calculate), what value of the ratio ((C3+C4)/C7) gives the best sounding amplifier?

What's the best construction/assembly method, that makes it relatively easy and painless to try out different ((C3+C4)/C7) ratios in the final amplifier, for critical listening tests?

What type of source material reveals these sonic differences, most obviously? Female vocals? Sheffield Drum record? Chamber music? At what volume levels?

What type of loudspeakers reveal these sonic differences, most obviously?
 
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vdi_nenna

Member
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2000-10-10 7:27 pm
PA, USA
I have build an F6 with jfet and dual-mono and F6 with mosfets with single power supply (PS). You can totally hear that they are from the same family, twins really. I don't sense any less power in the single PS. The character might be different, but not by much. It's subtle differences. Whether you like one or the other starts to become a matter of taste.

With that said, the more separation between channels, the better.
If I can't make mono-blocks, dual-mono is my choice.
 
There are a few custom places around that will wind a transformer to your specs. My a40 amp uses a transformer that was custom wound by Victoria Magnetics (now out of business). I've also used a place in Canada (no import tax to the US due to NAFTA) by the name of SumR - Richard Sumner Technology.

One of his 24 + 24 1000VA in my BA3 power amp. Beautiful transformers and strong as a beast. Highly recommended!

Russellc