New A-75

[Alain Dupont]

Hi to all,

I've decided to build a A75 Class A amplifier
from the article of Norm and Nelson.

And I need some advises:

1)- Replacing the finals by IRF 630 and IRF 9630
The IRF 230 and IRF 9230 reach 10 cad$ each...
That's too much for 48 devices + many others for matching.

2)- Doubling the power supply's with 2*500VA

3)- More final pairs perhaps 16 (12 origin)

4)- Are there PC Boards already available ?

5)- To be able to drive my Martin Logan
Aerius i .

I will be gracefull of any comment or advise
Regards.

[BobEllis]

for output FETs try IRFP240/9240 - under $2 US each. I bought 50 of each (fairchilds from mouser). I got four sets of 12 matched within .040 Volts VGS. The whole lot came in within .1 V. You shouldn't need too many extras to get matched sets.

Boards are available from audioexpress, although there are some errors and omissions on them. Search for A75 articles you should find most or contact me.

Not sure why you would want to add more output transistors - there is plenty of current capability already.

Dual mono/ monoblocks would be fine - I am using a single 1000VA transformer.

My pair of A-75s are waiting delivery of my cases, but the front end works well and sounds nice as a line stage. I just built an X-BOSOZ, but haven't had an opportunity to listen to it yet.

Others prefer the sound of the Alephs over the A-75. Haven't heard either yet, so I cannot comment except to note that you'll have a little less heat to get rid of with the A75 for the same outut power.

[fcel]

Don't know if this help .... I seem to recall Peter Daniel has some pre drive board with components already installed that he's putting up for sale. Check with him to see if it's still for sale.

[Peter Daniel]

Originally posted by Alain Dupont
Hi to all,

I've decided to build a A75 Class A amplifier
from the article of Norm and Nelson.

And I need some advises:

1)- Replacing the finals by IRF 630 and IRF 9630
The IRF 230 and IRF 9230 reach 10 cad$ each...
That's too much for 48 devices + many others for matching.

2)- Doubling the power supply's with 2*500VA

3)- More final pairs perhaps 16 (12 origin)

4)- Are there PC Boards already available ?

5)- To be able to drive my Martin Logan
Aerius i .

I will be gracefull of any comment or advise
Regards.

I have assembled and tested complete front end boards, matched sets of output devices in TO3 cases (230 &9130), transformers with aditional windings for front end PS, PS for front end circuit based on Mark Levinson 27.5 amps, heatsinks, rectifiers and capacitors, plus any additional parts you might need

[Stefano]

Are you thinking to sell'em?

[Stefano]

I'm interested too to, this is my mail: lindirizzo@virgilio.it

[Peter Daniel]

Here's the link to parts I'm selling: http://www.diyaudio.com/forums/showt...081#post244081

[Alain Dupont]

I have 2*750Va transfos +
30 Nichicon 5,600mF/63V capacitors.
on their way

And: 26 IRF 230 & 26 IRF 9230+
a serie of pcb's & pcb for power supply
on their way too.

Future...

Heatsinks waiting for price from acellthermal

Negociating for a stainless steel enclosure

A happy DIY'er.

Thanks to Nelson for the virus!

[Nelson Pass]

Your welcome

I will remind people that the A75 as published had about
twice as many outputs as it really needed. You can easily
cut back if your budget is low.

[mwmkravchenko]

You should be able to do much better on the price of the transistors. Check out allied , electrosonic, newark,even digikey

Mark