headphone amps question

gez · February 17, 2006, 04:26:25 PM

Everything's OK with the small phones though? No squeal?

bloodmist · February 17, 2006, 04:32:18 PM

I checked.. there is alot of distortion with speaker but youre right, no squealing. small headphones are good too..now I have to debug the first amp and see what I did there if anything : )))))))))))
whew. I feel happier now. seems one is working like it should. now I wait until I get my hands on some distortion pedal... and check that.hopefully by tonight.
thank you very much. I learned insane amount of info today. now if the effect works in chain, I will probably hold off on buying an amp : ) and instead build some effects.

gez · February 17, 2006, 04:35:43 PM

It sounds as though you were expecting too much of these little amps. If you want to drive bigger loads you need 'more gun' as Paul would say!

coitmusic · February 17, 2006, 05:12:25 PM

Bloodmist,
glad that you're feeling better about all this. I'm sure everybody here can appreciate how frustrating debugging can be. And ultimately, that's why you got some help....empathy not attitude. People love feeling like a hero to someone who humbly asks for help and hate feeling obligated. Ask nicely, provide lots of info, and you'll get help.

Debugging can take a lot of patience! and sometimes time away from your project. About a year ago I started a vco/vca project and wasn't able to get it working. Frustrated the hell out of me. After a couple attempts at debuging it, I ultimately put in the "reject" pile on my desk. I finally pulled it out yesterday and with a careful comparison with the schematic point by point, I eventually found that I had miswired one pot (I mixed up pins 2 and 3) and that was the only problem! And now looking back, I realize that before going through this, I had no idea how the effect worked, but in the process of checking it over I learned how it worked intimately. This won't happen every time, but I often learn the most about electronics when trying to fix something that isn't working. Very annoying, but very instructive.

Good luck!
Chester

bloodmist · February 17, 2006, 07:22:59 PM

thank you.
nope... connect guitar effect amp(not ruby) everything works.
connect guitar ruby works
connect guitar effect ruby. silence. can I somehow trace the signal?

gez · February 18, 2006, 03:40:59 AM

What is the guitar effect(s). Be specific. Is it something you made yourself?

This sounds like an impedance problem but there shouldn't be one, which suggests a fault at the input buffer stage. Are you sure you have the correct value for the resistor from the FET's gate to ground? Sure the wiring connecting the input is OK - not shorting anything to ground through a solder bridge?

gez · February 18, 2006, 03:43:41 AM

Check for DC voltage at the output of your effect and report back with a reading.

bloodmist · February 18, 2006, 10:34:00 AM

Digitech Rock Distortion. factory made.

connection seems fine(solder clearly separated.). unless I am stupid, and can't read anymore(which happened once already with first project that I made) resistor: brown green green 1.5M right?

voltage: umm...at the output(guitar plugged in, LED on effect says it is on) cable plugged in and put one(probe) on the tip of the poinlt thing and another on the other part(base) right?6-7.5v. but when plugged into the amp(not ruby) works fine.

gez · February 18, 2006, 11:15:41 AM

Quote from: bloodmist on February 18, 2006, 10:34:00 AM
voltage: umm...at the output(guitar plugged in, LED on effect says it is on) cable plugged in and put one(probe) on the tip of the poinlt thing and another on the other part(base) right?6-7.5v. but when plugged into the amp(not ruby) works fine.

What I wanted was the effect on, a lead stuck in the output and you measure the DC voltage between the tip of the jack and its barrel, which is what I think you've done...right? Just a yes will do!

You've said it measures 6-7.5V Which is it...or is you meter flickering all over the place? Plus, this is a DC voltage measurement, yes?

If so, this is what I thought. There's no input cap on the FET buffer stage. It's one of those things that you can get away with 99.9% of the time...until one day you come a cropper. That's why I always stick a DC blocking cap on the input of JFET buffers (or used to, I don't really use them anymore). Try sticking a cap on the input - 47n or larger should do - then try again.

bloodmist · February 18, 2006, 11:27:37 AM

yes this is what I have done...
I use a 3.5 cablewith 3.5 ends and converters to the standart 1/4" on both sides... and so without one of the ends it read 6 with both on, it read 7.3-7.5v.
oki. so a will 100n ceramic cap do?meaning .1F I think : ) also I put it between gate on FET and tip on the input jack?. right?

I have to leave to california for 3 days I have to leave soon so I can't do this right now but I will try it on tuesday...

gez · February 18, 2006, 11:31:04 AM

Quote from: bloodmist on February 18, 2006, 11:27:37 AMwill 100n ceramic cap do?meaning .1F I think : ) also I put it between gate on FET and tip on the input jack?. right?

Yes, 100n is fine. Yes, it goes between the tip of the jack and the gate of the FET. This should solve the problem (the DC voltage is screwing up the bias of the FET).

bloodmist · February 18, 2006, 12:41:36 PM

.1mF(greek looking m) is 100n? so I put it in and still there is no diference : (

gez · February 18, 2006, 12:55:43 PM

Quote from: bloodmist on February 18, 2006, 12:41:36 PM
.1mF(greek looking m) is 100n? so I put it in and still there is no diference : (

100nF is .1uF. This should have solved the problem.

Plug the effect into the Ruby and take voltage measurements for gate source and drain please (leave the input cap in place). Also do this without the effect plugged in. Report back with readings.

Also, when you measured the voltage at the output of the effect which test lead did you have on the barrel of the jack plug and which lead on the tip? The barrel should be ground so the measurement should have been taken with black on the barrel, red on the tip. I just want to know if the reading was negative or positive. Thanks.

gez · February 18, 2006, 01:00:01 PM

PS Could you just confirm what the symptoms are? Do you get any sound at the output, albeit distorted, or is it totally mute?

bloodmist · February 18, 2006, 01:32:41 PM

I have to leave now till tuesday...
plug guitar into amp: works oki.
plaug guitar effect amp. total silence.

gez · February 18, 2006, 02:11:55 PM

Quote from: bloodmist on February 18, 2006, 01:32:41 PM
I have to leave now till tuesday...
plug guitar into amp: works oki.
plaug guitar effect amp. total silence.

No problem.

If the voltage from the effect is negative it might be cutting off the FET, which would account for the silence. The cap should have sorted this out though. The voltages will tell us if the cap's blocking DC ok.

Anyway, bon voyage!

coitmusic · February 18, 2006, 06:52:47 PM

Gez,
Thanks for taking on the most of the helping here...I got busy elsewhere. Plus you sound much more knowledgeable than I.

Bloodmist,

I was also going to suggest an input cap...I think it might be important here to make sure to note that you should cut the wire going from the tip of the input jack to the gate of the FET and put the cap (0.1 uf) there. The fact that the guitar works alone with the amp and not with the effect seems to indicate the the pedal is the problem (or at least a compatability between them). Cable issues might also be the cause as adding the effect also adds another cable. The use of adapers (1/8th to 1/4 in.) seems like a place to look as well. Since it sounds like you do have another amp I'd start with the trace cable mentioned earlier and probe around a bit to find out where the signal drops out.

Best,
Chester

bloodmist · February 26, 2006, 07:57:13 PM

whew I am back.
I was just wasted throughout the week with small sleeping hours and lots of school work to catrch up on.....
now I am fine. soooo..I found the problem : )
My cable (the funny thinn 3.5 mm cable...) had stereo adapters onit and that was what was screwing everything...
I got a different cable(full-fledged 1/4" cable with no adapters mono.) and everything works like a charm.I was soo excited. I was just extatic.
soo...I thank everyone who replied to my attetude and especially gez and coitmusic. THANK YOU THANK YOU THANK YOU.
my next project will be some good distortion...and I am about 2/3 sure I will mess something up.(first project was 1 transistor a couple of diodes and 3 resistors and 2 capasitors... in second project I moved up to an IC.) soo... with that said, can someone suggest a distortion pedal, with 1 IC about 5-15 resistors and 2-3 pots : ) because I really don't know what to build : )))) I only know that I want a distortion with gain control and something like morph(to change the sicklyness of the sound).. any suggestions? ohh and it should have a very detailed building description(should.. but doesn't have to.)...

coitmusic · February 26, 2006, 11:34:30 PM

Glad to hear that everything worked out.

I love the stuff over at 4ms pedals. www.commonsound.com For an easy build, try the fuzz jade. When you've done a bit more, try the noise swash.

Chester

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headphone amps question