This is not just another gainclone

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Jump to Latest
Z

zygibajt

Member
Joined 2003
Hi,
I fired up my Gainclone yesterday.Everything seems to be allright.I have three diffrent pairs of speakers.One of them are Altec 891A,two way studio monitors.When I hooked them up they started cracking.They play the music but crack.Only when listened very silent they don't.I was investigating what is happening and figured that the couse was a speaker cable (quite expensive one,figh capacity-about 1nF per meter).Exchanged cable and everything works fine.It happens only with Altec's.Other speakers don't crack with this cable.Also when I unplug one of the Altecs from GC there is no cracking and I can listen as loud as I want.Is it possible that GC is so sensitive? But why there is no cracking when only one speaker is connected.There is no diffrance which channel and which speaker.

I used 800VA ,2*19VAC tr.,25A single bridge,2,2uF coupling cap ,220K feedback resistor.Also I have DIY Aleph P preamp so instead of 50K pot I put 47K resistor to ground.
Dc offset is about 50mV ,same in both channels.
Do You have any idea why does it crack?
Bartek
 
Cradle22

Cradle22

Member
Joined 2003
Matttcattt said:

http://www.freewebs.com/matttcatttweb/index.htm

any comments?
Click to expand...

On your site you mention building GC for a car amp. But what do you do about voltage regulation?

Or do you use the simple 0-14.4 V voltage swing of a car? In that case the National LM chips would not work because they must have a +- supply, whereas the OPA chips will work (but I think that you use them).

But with 0-14.4 V you waste a lot of potential of these amp chips, since most of them are designed to work up to 80 V voltage swing...

And how will you stabilize the voltage? Simply with filter caps? I do not think that the solution will be sufficient...

If building a chip amp for a car I would stick to those chips now commonly used inside car stereo units... and not those for home use...


Bye,

Arndt
 
fdegrove

fdegrove

diyAudio Senior Member
Joined 2002
Hi,

Strange...I am using IE6.0 SP1 + a whole raft of sandbag updates on Win2K and have no problem whatsoever.

If you guys want that page in a different format I can convert it to *.doc (MS Office 2000) or *.PDF (you'll need Acrobat Reader for that, free at adobe.com).

Just send me a e-mail through the forum and I'll mail it to you.

Cheers,;)
 
moamps

moamps

diyAudio Member
Joined 2002
moxtone.com
zygibajt said:
They play the music but crack.Only when listened very silent they don't.I was investigating what is happening and figured that the couse was a speaker cable (quite expensive one,figh capacity-about 1nF per meter).Exchanged cable and everything works fine.It happens only with Altec's.
Click to expand...

Hi,

Your amp oscillates, IMHO.
Place Zobel network on amp output terminals.

Regards
 
fdegrove

fdegrove

diyAudio Senior Member
Joined 2002
Hi,

(quite expensive one,figh capacity-about 1nF per meter).Exchanged cable and everything works fine.It happens only with Altec's.
Click to expand...

At a nanoF/m this to be expected....can't imagine any half sane cable designer putting such a crazy cable onto the market.

A well designed OPT coupled tube amp would drive that without going belly up but that's about it.

Place Zobel network on amp output terminals.
Click to expand...

It'll still be on the brink of stability and I doubt it would solve it entirely...beter than nothing, I agree.

Cheers,;)
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Top Bottom