Gainclone Problems; Aahh!

[raffir]

I've been building K50 as seen in kitsrus.com/pdf/k50.pdf.

Yet no matter what I do, it seems to occasionally start playing for a couple of seconds and then buzz. Sometimes it just buzzes. I have yet to get consistent playing. I'm using a 15v toroidal supply with one of the dual secondaries. I've also attached a potentionometer on the input.

What do I do? This has been driving me nuts for weeks!

Yours,

Raffi.

 

[till]

could you give a better description of your powersupply or a drawing?

 

[jan.didden]

GC problems

When you say buzz, does this sound through the music? Or does the music disappear and is replaced with the buzz? Can you describe the buzz? Is it noiselike, a tone, humm?

Jan Didden

 

[JAZZ2250]

Why don't you try the following way?

Disconnect the (-) speaker wire from the board and directly connect it from the (-) speaker terminal to ground (star ground point).

 

[Gcollier]

Similar Problem Here!!!

Hi, I'm experiencing a similar problem here. I'm using Jordans Gainclone PCB design that I found in one of these posts (sorry can't remember which). Anyway, the amp plays beautifully for about 15 seconds, then the sound gets distorted. When I turn on the amp without any input there is also no sound for about 10 to 15 seconds then I get a buzz/humm. The chip doesn't seem to be warm or anything like that, in fact it is mounted to a more than generous heatsink, I've been thinking it may have something to do with the caps. Any suggestions???

Thanks.

 

[Philo]

Actually, both problems sound like something is not wired correctly with the psu specifically the bridges. My first attempt had a similar problem. Are you using two bridges per channel? If you are only using a single transformer you should use two bridges per secondary. If you are using two dual secondary transformers, you can get away with one bridge per channel. How is your PSU set up?

 

[jan.didden]

GC stuff

It may help to measure the supplies from switch-on to when the buzz starts. Also DC output and input levels.

Don't just sit there, do something!

Jan Didden

 

[fedde]

Yet no matter what I do, it seems to occasionally start playing for a couple of seconds and then buzz. Sometimes it just buzzes. I have yet to get consistent playing. I'm using a 15v toroidal supply with one of the dual secondaries.

???

You use only one of the two secondaries !? So you have a floating ground and use only around 9+/9- V for the chip. Or... ?

Fedde

 

[raffir]

Response to questions

I do not hear any music; just a buzz.
I'll try connecting the speaker ground to star ground.
Ground is actually just the 3d pin on the AC cord I'm using (the green one).
I'm using one bridge rectifier, which outputs ~15 v (14.58 or some such number).
How should I wire the two secondaries? I have a few extra bridges, and I'd really like to get this all working.

Thanks a lot,

Raffi.

 

[joensd]

Ground is actually just the 3d pin on the AC cord I'm using (the green one).

You mean that´s the only ground you´re using in your circuit?
A lot would come clear then.
Your amplifier should work somehow without the "green one".
That´s for to ground the chassis and then connect to amplifier ground by resistor or so.

You should give a detailed description on the connections you did before you go on.

And please read a bit about the basics before you connect everything up or you might burn the house down ;-)

Have a look here for example :
Rod Elliots Site
A lot of nice articles to read and learn from.
Especially the one about proper grounding (earthing your hifi).

Regards
Jens

 

[joensd]

Here´s are two pictures of possible power supplies you could build :

Link

The thread might be interesting anyway so...
(And there are loads of other threads bout gainclones)

Regards
Jens

 

[raffir]

You mean that´s the only ground you´re using in your circuit?
A lot would come clear then.

You should give a detailed description on the connections you did before you go on.

And please read a bit about the basics before you connect everything up or you might burn the house down ;-)

Have a look here for example :
Rod Elliots Site
A lot of nice articles to read and learn from.

Regards
Jens

Alright. At present there is no chassis; just the bare circuit board. Once stuff starts working I will build a chassis.
I'll try connecting a resistor between amp ground and the green pin, or use two bridge rectifiers and make a ground like that.

I have read a *lot* of stuff on Rod Eilliot's site + every book I could find in the library system on the subject. Nonetheless, this is my first crack at AC powered anything, much less audio equipment. So I'm really grateful for any help I can get. Thanks, really. I'll try all these tips and try not to get killed (that's what the four fuses in each chanel are for).

Thanks,

Raffi.

 

[fedde]

You really need to connect both secondaries !!! And connect the two center secondary wires to the ground when using one bridge. Or use the two bridge configuration from the Thorsten schematic.

( commercial break )
You can find that schematic on my gainclone page, and quite some more information! Have a look at www.fedde.tk !!!
( end of commercial break )

Fedde