Help upgrading ZenV2 to ZenV4

df · 14th October 2002, 01:51 PM

After more then 20 years without a soldering iron, I was looking for an phono preamp. So I dropped to the pass labs web page. Since then the virus hat got me, I have build a ZEN-lite and a Zen V2. Thank you everybody for posting and answering in this forum, specially the one and only.

This weekend I’ve tried to apply the buffer of V4 to the input of V2. I could not find in Switzerland the ZVP3310 so tried with BS 250, like it was said somewhere in this forum.

The resulting sound hat more dynamics but has some kind of distortion and has lost all of his relaxed clarity.

- I did not touch the power supply, it is still the one of V2, is this a problem?

- Between drain and source of Q4 (BS250) I have only 2,15 V. When I lower R13 to 2.3 kOhm it goes up to 2,35 V. It should be at 4 V!

- When I lower R2 to 22kOhm and/or R3 to 100kOhm the sound gets a little better but only a little…

Any ideas?

Daniel

Nelson Pass · 14th October 2002, 05:50 PM

No reason why it shouldn't work.

Check your wiring, make certain that all the parts are
at or close to specified values, try another Mosfet.

df · 21st October 2002, 06:23 AM

Thank you Nelson

C12 was the problem. I made it out of two twisted wires but only 3cm long, now it is 7cm long and the distortion is no longer audible.

Before I changed back R0/R1 to 0.33 for 2 amps. With my IRFP150 it sounds better…

Playing around a bit with the BS250 I thought of making an aleph cascode input stage out of them. The power supply has to be changed…

Is this possible?

Daniel

Nelson Pass · 21st October 2002, 08:17 PM

You can cascode the front end diff pair easily, and without
any alteration to the supply.

For reference, check out the cascode amp article at
www.passlabs.com or the A75 article at www.passdiy.com

BTW, the wires I use for making tiny capacitors are the
very tiny wire-wrap kind, so you get more capacitance
per centimeter. Then I make them too long and trim them
with a pair of scissors.

Some people will prefer the sound of a 150 over a 140. It
is similar to 2 140's in parallel.

14th October 2002, 01:51 PM	#1
df diyAudio Member Join Date: May 2002 Location: Switzerland	Help upgrading ZenV2 to ZenV4 After more then 20 years without a soldering iron, I was looking for an phono preamp. So I dropped to the pass labs web page. Since then the virus hat got me, I have build a ZEN-lite and a Zen V2. Thank you everybody for posting and answering in this forum, specially the one and only. This weekend I’ve tried to apply the buffer of V4 to the input of V2. I could not find in Switzerland the ZVP3310 so tried with BS 250, like it was said somewhere in this forum. The resulting sound hat more dynamics but has some kind of distortion and has lost all of his relaxed clarity. - I did not touch the power supply, it is still the one of V2, is this a problem? - Between drain and source of Q4 (BS250) I have only 2,15 V. When I lower R13 to 2.3 kOhm it goes up to 2,35 V. It should be at 4 V! - When I lower R2 to 22kOhm and/or R3 to 100kOhm the sound gets a little better but only a little… Any ideas? Daniel

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14th October 2002, 05:50 PM	#2
Nelson Pass The one and only Join Date: Mar 2001	No reason why it shouldn't work. Check your wiring, make certain that all the parts are at or close to specified values, try another Mosfet.

21st October 2002, 06:23 AM	#3
df diyAudio Member Join Date: May 2002 Location: Switzerland	Thank you Nelson C12 was the problem. I made it out of two twisted wires but only 3cm long, now it is 7cm long and the distortion is no longer audible. Before I changed back R0/R1 to 0.33 for 2 amps. With my IRFP150 it sounds better… Playing around a bit with the BS250 I thought of making an aleph cascode input stage out of them. The power supply has to be changed… Is this possible? Daniel

21st October 2002, 08:17 PM	#4
Nelson Pass The one and only Join Date: Mar 2001	You can cascode the front end diff pair easily, and without any alteration to the supply. For reference, check out the cascode amp article at www.passlabs.com or the A75 article at www.passdiy.com BTW, the wires I use for making tiny capacitors are the very tiny wire-wrap kind, so you get more capacitance per centimeter. Then I make them too long and trim them with a pair of scissors. Some people will prefer the sound of a 150 over a 140. It is similar to 2 140's in parallel.

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