Aleph P1.7 first pictures

[acaudio]

Originally posted by Clarkcr
Where is the universal ground? Doesn't the circuit need a ground?

Nice looking setup.

C

Hi,
maybe i don´t understand your question.

Ground:

both channels have separate ground.
powersupply too.
The controlboard too.
The volume control relay shared a 12VDC supply and are switched to Control-gnd via transistors, see pic. Left and right channel are not an common ground. As i buy an second transformer, are both channels fully separate.
All pcbs are made with Ground plane at bottom. Maybe is it not a best? But singlesided layout with a straight star ground wirng is not so easy... This should be realise by next project (AX)

greetings

Adam

[Clarkcr]

Okay, I just didn't see where there was a ground anywhere. I always thought there needed to be a star washer type ground.

C

[Holger Barske]

Originally posted by Clarkcr
Okay, I just didn't see where there was a ground anywhere. I always thought there needed to be a star washer type ground.
C

Have a look at the bottom pcb layer. There you'll find the ground plane. It doesn't show in the other PDFs.

[rsbay]

Hallo Adam,

nice work !!! I also plan to build an Aleph P. Which type of MOSFET's
you have used in your design ? The original types are not available
at my favorite dealer (Reichelt).

Regards

Ralph

[acaudio]

Originally posted by rsbay
...Which type of MOSFET's
you have used in your design ? The original types are not available
at my favorite dealer (Reichelt)....

Thanks Ralph!

Reichelt is too my favorite.
I used IRF510 (SEC) and IRF9610 (Fairchild) both from Reichelt.I bought 50+50 piece , selected these from equally lot and matched in pair to 1mV. See my matching-circuit. At Reichelt you can´t buy a original sealed tube from producer, only mix.
But you can buy more and send what you don´t need back.

thx
Adam

[rsbay]

Hallo Adam,

I take a look at the datasheets of the 610 and 9610 at
International Rectifier and I think about giving the 630 and 9630 a
chance. They have nearly the same data's, but the Rds_on of the
630/9630 are a little bit lower. These MOSFET's are available
at Reichelt.

Greetings from Titz

Ralph

[uli]

I wouldnt use the 630/9630. In a preamp the Rdson is of no
importance and as these Mosfets are primarily designed as
switches they dont perform too well in an analog circuit.

You may read some of the background literature by NP as well
as the construction articles about A75 by NP and Norm Thagard.

Uli

[acaudio]

Originally posted by rsbay
...They have nearly the same data's, but the Rds_on of the
630/9630 are a little bit lower. ...

Hi Ralph,

Have a look at the in-/out capacitance:

IRF610 140/53pF
IRF510 180/81pF
IRF630 800/240pF

/Adam

[rsbay]

Thanks Adam & Uli,

I only take a look at the current and the channel resistance, but forgot
the capacitance. I will look a second time and also read the articels.

Regards

Ralph

[rsbay]

Hello,

I followed your tips and bought IRF610 / IRF9610 (50 pieces each)
at Conrad Elektronik. A little bit more expensive than my prefered
supplier Reichelt, but I get the "original" from International Rectifier.

In the next step I have to select the right MOSFET's for my Aleph P.
Which MOSFET should be equal ? I think the two upper current source
transistors, the two lower current source transistors and the two
amplifier transistors in the middle should have the same values, so that
both sides of the preamp are identical.

Regards

Ralph