heavy distortion in sonic t-amp after input mods

[pne]

i've just finished modifying the input stage according to the diagram on mardis's site. Blackgates are still on order so I used some plain electrolytic caps rated 2.2uf 50v with 22k 1/4watt resistors. The amp plays fine for a few minutes, then it outputs heavy sputtering/distortion. Could this be due to the caps I used?

The diagram
[IMGDEAD]http://www.michael.mardis.com/sonic/images/input-sonic.jpg[/IMGDEAD]
shows the negative lead of the cap going to the resistor right? Are the blackgate c series nonpolar? Am I using the wrong type of cap?

thanks.

 

[phase_accurate]

AFAIK is the input potential of the Tripath chip around half the supply voltage so the cap should be soldered the other way around i.e. plus to the resistor - minus to the pot.

Regards

Charles

 

[pne]

blast! In the process of unsoldering the caps I accidently lifted one of the pads the resistor lead goes into. Is there another place I can solder the lead to or is this amp done?

 

[TriodeGuy]

It's been my experience that just about every foul up can be fixed. You just need to look at the input schematic and poke around a bit with an ohm meter to find "other" end of the trace...then bypass the trace with some blue wire.

I have to give mad props to those who've been able to solder thru hole leads onto those smd pads and get it to work. I would'nt even attempt it. For me it was much easier to remove all the parts in the signal path and then bridge these with blue wire. Basically making a direct signal path from the pot's connector to the signal inputs on the chip. I then ran the leads from my input caps thru the holes left behind by the removed connector.

 

[TriodeGuy]

Need to make a correction here... I do leave the 20k resistors in the signal path, but everything that comes before is removed.

 

[kujina]

Hi I'm a bit of a newb, how does this input mod benefit the amp/sound?
And can anyone give links to any other mods for this amp.

...Thanks...

 

[kec]

Do the input caps need to be electrolytic? Can you use Solen caps?

-Ken

 

[wim]

I have the same question as KEC, because i read over and over that people use electrolyts as inputcap; in all me amps the inputcap is a good quality cap with no polarity (most off the time i use chateauroux polypropylene (MKP)).

i always thought a electrolyt is no good inputcap, but please tell me if i am wrong, and why i am wrong.

 

[Wayne1]

I think people use NP electrolytics, such as Black Gate N or NX series, because they are physically small.

A film or film and foil cap of 2.2 or 3.3 uF is a very large cap.

If you have space in whatever chassis you are using, a film cap will work fine. If you have a LOT of space and money, try using a paper in oil cap, like the Jensen.

I personally use Sonicaps in all of my Tripath amp builds.