Help with Transformer selection please for p/amp

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laverda

laverda

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Joined 2004
#1
Hi all

Having been a recent convert to Mr Pass's BOZ...I would like to build a class A power amp, but I would like some guidance re:- transformers. The reason being I have a few knocking about from past projects...

1 off 700va 2 x 35-0-35 CT
2 off 300va 2 x 0-35
1 off 350va 2 x 35-0-35 CT (screened potted)

bearing in mind one of the biggest outlays when building a P/Amp is the TX. Could I use any of the above on a 'project' of put them back on the shelf and start from scratch....

TIA
 
#5
Thank you Mr Pass (wasn't expecting your input, feel honoured)

Yes picobumps, I feel monos are the way to go, in one chassis or two smaller?? Mmm, I suppose the 'two smaller' would be more practical. (maybe)

F5T....I see no fet's are available from the store, is there a preferred alternative please. I know there are loads of 'marched pairs' on ebay but would like some guidance here.

Soft start and rectifiers I have, PSU caps,..I wonder if T nets (4 poles) would be any good, I have a box of these 10000uf 63v but space might be the limiting factor here as would need 60000uf? per amp.

Time for some homework

again thanks all
 
#8
F5T layout

Zen Mod said:
it'll handle 80W of heat per side

how you're gonna organize outputs in two groups , that's another issue
Click to expand...




So, Im looking to do something like this (now a 5U chassis not a 4U) Caps are 22000uf 63v. I may relocate the rectifier to tease a bit more room but I hope this will be OK..?

I have the TX's, caps, rectifiers and a soft start. (which i'll mount on the rear panel) I'm slowly getting my head round the circuit and how to implement the build...There's a little light engineering to be done with some copper (I have a 3mm sheet) for the bars. Thinking about 'snubbers' any advise here would be great.

Just got to source the BOM order the chassis and boards from the shop and were good to go...

then I'll be asking questions and scrolling through the build threads...
 
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#11
2 picoDumbs said:
This is your thread you can do whatever you like here.
Is your drawing drawn to scale?
You should be able to run the 400mm 5U heatsinks to 120W per side maybe a little higher.
Basically bias till they feel bloody hot with your hand on the sinks.
Click to expand...

Yes, the drawing is to scale..I'm thinking along the lines of mono blocks now (as suggested) would 3U 400 handle the 50W per side?. I must learn the calc for this...

I have drawn a section through the 400 5U with components on board and half of the internal space is empty. Now I know this is a trade off as we need to dissipate (dump) the unwanted heat but I'm just wondering...sinks are convection cooling, (free air cooling) a small fan would assist enabling a smaller surface area to be used in sinking.

Na, ignore all the fan stuff life's to short.

Yes, monoblocks are the way to go and she'll only be half pissed off with two smaller boxes rather than one big monolith parked in the middle of the lounge.

TIA
 
#12
Yeah that should be fine with regards to dissipation, but is 120mm enough height for you?
What is height of mounted transformer?
What is height of mounted caps?
Check UMS holes will fit on 120mm heatsink. Most important if you are using diyaudio store pcbs.

If there is a problem with any of those issues go to 4U.
 
#14
Thanks for the input Gents,

After due consideration (she had no say in the end) I'll will be going with the 5U 400, though still waiting for HIFI200 to provide details...been waiting over a week now...errr

F5T boards and jfets have been shipped from the shop..I now need to source the MOSFETS (help)

TIA
 
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