Pass A40 versus ZEN-4

Skorpio · 27th October 2005, 12:24 PM

Do you have some pros and cons on these two interesting construction?

My speakers are Snell E3 and I don't expect high sound pressure, rather high quality (jazz, blues, etc.). Vocals are important.

My own list:

A40 Pros: Reputation, output power, BJTs
A40 Cons: Old, power transistors hard to get

Z4 Pros: Reputation, simplicity
Z4 Cons: Output power, MOS-FETs

Skorpio · 27th October 2005, 02:21 PM

Another thing....the Pass A40 has a special idle current feedback loop. Will this work also, if the amp i biased in class A/B mode at ex. 15-20W class A?

Nelson Pass · 27th October 2005, 04:42 PM

Quote:

Originally posted by Skorpio
Another thing....the Pass A40 has a special idle current feedback loop. Will this work also, if the amp i biased in class A/B mode at ex. 15-20W class A?

If you want to operate the amp Class AB, or for that matter if
you want to bias it to other than the default value, I suggest
an ordinary Vbe multiplier like you see everywhere else.

Eric · 28th October 2005, 12:42 PM

Skorpio,

See my web page for some detalis on the a40

It has everything you need to build the amp, including a full parts list with associated vendors where the parts may be found. I've been using my for a few years now and enjoy it very much!

Eric

MikeW · 28th October 2005, 03:02 PM

Eric nice website.
MOSFET A-40
http://www.diyaudio.com/forums/showt...527#post581527

Eric · 28th October 2005, 07:10 PM

Thanks for the nice comments, Mike. I've been following the development of the Mosfet A40 as well...

Eric

Buhl · 2nd November 2005, 11:21 AM

hello Skorpio

I have two assembled Z4 boards and psu parts on my "will never get finished" shelf - they are for sale if you are interested - have sent you a mail via this site.

Cheers !
Buhl

Skorpio · 5th November 2005, 08:39 AM

Quote:

Originally posted by Buhl
hello Skorpio

I have two assembled Z4 boards and psu parts on my "will never get finished" shelf - they are for sale if you are interested - have sent you a mail via this site.

Cheers !
Buhl

I have also send you one...

Skorpio · 23rd November 2005, 07:41 AM

Quote:

Originally posted by Nelson Pass

If you want to operate the amp Class AB, or for that matter if
you want to bias it to other than the default value, I suggest
an ordinary Vbe multiplier like you see everywhere else.

I guess this will require some terminal feedback from the main heat sink to the VBE transistor? Is this also relevant in the original design?

Is it possilbe to make it switchable, A/B in normal mode and A with feed-back i special mode? And can this switch be operated in listening mode?

Skorpio · 23rd November 2005, 08:18 AM

Also I thinking on changing the original in-package darlington power transistors to a discrete variant:

Two set of MJ15003/4 on the main heatsink with 0.68ohm emitter resistors.

On the PCB board with heatsinks, drivers for the output, BD139/140 as emitterfollowers, with 100ohm between emitters.

Will this work ok?
Do I need resistance between BD139/140 and bases on output transistors?

27th October 2005, 12:24 PM	#1
Skorpio diyAudio Member Join Date: Mar 2004 Location: Denmark	Pass A40 versus ZEN-4 Do you have some pros and cons on these two interesting construction? My speakers are Snell E3 and I don't expect high sound pressure, rather high quality (jazz, blues, etc.). Vocals are important. My own list: A40 Pros: Reputation, output power, BJTs A40 Cons: Old, power transistors hard to get Z4 Pros: Reputation, simplicity Z4 Cons: Output power, MOS-FETs

28th October 2005, 03:02 PM	#5
MikeW diyAudio Member Join Date: Sep 2002 Location: North of Boston	Eric nice website. MOSFET A-40 http://www.diyaudio.com/forums/showt...527#post581527 __________________ MikeW

2nd November 2005, 11:21 AM	#7
Buhl diyAudio Member Join Date: May 2002 Location: Aalborg, Denmark	Zen V.4 parts hello Skorpio I have two assembled Z4 boards and psu parts on my "will never get finished" shelf - they are for sale if you are interested - have sent you a mail via this site. Cheers ! Buhl __________________ "Calculations? We don't need no stinkin calculations! We just make them really big!" Quote: Nelson Pass

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27th October 2005, 02:21 PM	#2
Skorpio diyAudio Member Join Date: Mar 2004 Location: Denmark	Another thing....the Pass A40 has a special idle current feedback loop. Will this work also, if the amp i biased in class A/B mode at ex. 15-20W class A?

28th October 2005, 12:42 PM	#4
Eric diyAudio Member Join Date: Nov 2000 Location: Central PA, USA	Skorpio, See my web page for some detalis on the a40 It has everything you need to build the amp, including a full parts list with associated vendors where the parts may be found. I've been using my for a few years now and enjoy it very much! Eric

28th October 2005, 07:10 PM	#6
Eric diyAudio Member Join Date: Nov 2000 Location: Central PA, USA	Thanks for the nice comments, Mike. I've been following the development of the Mosfet A40 as well... Eric

23rd November 2005, 08:18 AM	#10
Skorpio diyAudio Member Join Date: Mar 2004 Location: Denmark	Also I thinking on changing the original in-package darlington power transistors to a discrete variant: Two set of MJ15003/4 on the main heatsink with 0.68ohm emitter resistors. On the PCB board with heatsinks, drivers for the output, BD139/140 as emitterfollowers, with 100ohm between emitters. Will this work ok? Do I need resistance between BD139/140 and bases on output transistors?

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