Tricky little problem with Z4 component

Buhl · 19th August 2003, 03:14 PM

Hi there !

This is a little embarressing, but when i ordered the parts for my dual bridged Z4, i couldent get fixed value 5 pF capacitors, so i ordered variable 5-15 pF. Fine enough, but how do I check i witch of the outer positions (the lowest 5 pF one) those trimmers has to be in ?

I have no scope to measure the square wave as mentioned by
nelson in the article, only a "standard multimeter that can measure volts, amps, resistance and diode function.

Can I do this without a capacitance-meter ?

Cheers !

Hans Houmøller

Netlist · 19th August 2003, 03:39 PM

Hans
You should definitely try to buy a scope.
As for the cap, only with a scope it will be possible to trim a square wave up to it's nicest shape.
You could also buy 2 10pf caps and solder them in series.
If you get some decent caps (silver mica) it will improve the sound as well. I'm not claiming I would hear the difference but a trimming cap is probably not the best sounding device to put in a feedback loop.
Without a scope, my guess is that it will be difficult to measure
the trimming position with such low values.
Maybe others know how to do this...

Greetings

/Hugo

Buhl · 19th August 2003, 08:58 PM

Quote:

Originally posted by Netlist
Hans
You should definitely try to buy a scope.
As for the cap, only with a scope it will be possible to trim a square wave up to it's nicest shape.
You could also buy 2 10pf caps and solder them in series.
If you get some decent caps (silver mica) it will improve the sound as well. I'm not claiming I would hear the difference but a trimming cap is probably not the best sounding device to put in a feedback loop.
Without a scope, my guess is that it will be difficult to measure
the trimming position with such low values.
Maybe others know how to do this...

Greetings

/Hugo

Thnx for the advice Hugo - Ill try and persuade someone with a scope to measure a squarewave for me. No harm will come to the amp or speaker though if operating for a short while in the 15 pF mode instead of 5 pF - just in the power-up period ?

Cheers !

Hans Houmøller

Nelson Pass · 20th August 2003, 07:37 PM

This is not a critical thing. When I want 5 pF, I twist 2
pieces of wire wrap wire (the teflon insulated kind) together
for about an inch.

eLarson · 21st August 2003, 01:15 AM

A teflon trimmer capacitor that anyone could afford! How cool is that?

Erik

Buhl · 21st August 2003, 03:10 PM

Thanx for the replys, but I actually came across 4 pcs. of 5 pF at my local electronics shop, that normally have everything but the partsI need, but in this case - they had what I couldnt find on the web......

Another thing, I very soon about to fire up my Z4 - can i run two boards supply from the unregulated supply in parallel ? Simply connecting board two to the same supply + and - as board one ?

/cheers !

Hans Houmøller

19th August 2003, 03:14 PM	#1
Buhl diyAudio Member Join Date: May 2002 Location: Aalborg, Denmark	Tricky little problem with Z4 component Hi there ! This is a little embarressing, but when i ordered the parts for my dual bridged Z4, i couldent get fixed value 5 pF capacitors, so i ordered variable 5-15 pF. Fine enough, but how do I check i witch of the outer positions (the lowest 5 pF one) those trimmers has to be in ? I have no scope to measure the square wave as mentioned by nelson in the article, only a "standard multimeter that can measure volts, amps, resistance and diode function. Can I do this without a capacitance-meter ? Cheers ! Hans Houmøller

21st August 2003, 01:15 AM	#5
eLarson diyAudio Member Join Date: Aug 2002 Location: Gaithersburg, MD	A teflon trimmer capacitor that anyone could afford! How cool is that? Erik __________________ Would a woodchuck bother to chuck MDF?

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19th August 2003, 03:39 PM	#2
Netlist diyAudio Moderator Join Date: Jan 2003	Hans You should definitely try to buy a scope. As for the cap, only with a scope it will be possible to trim a square wave up to it's nicest shape. You could also buy 2 10pf caps and solder them in series. If you get some decent caps (silver mica) it will improve the sound as well. I'm not claiming I would hear the difference but a trimming cap is probably not the best sounding device to put in a feedback loop. Without a scope, my guess is that it will be difficult to measure the trimming position with such low values. Maybe others know how to do this... Greetings /Hugo

20th August 2003, 07:37 PM	#4
Nelson Pass The one and only Join Date: Mar 2001	This is not a critical thing. When I want 5 pF, I twist 2 pieces of wire wrap wire (the teflon insulated kind) together for about an inch.

21st August 2003, 03:10 PM	#6
Buhl diyAudio Member Join Date: May 2002 Location: Aalborg, Denmark	Thanx for the replys, but I actually came across 4 pcs. of 5 pF at my local electronics shop, that normally have everything but the partsI need, but in this case - they had what I couldnt find on the web...... Another thing, I very soon about to fire up my Z4 - can i run two boards supply from the unregulated supply in parallel ? Simply connecting board two to the same supply + and - as board one ? /cheers ! Hans Houmøller

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