[pomdomz]

Hey all

I run a tube preamp to a solid state amp, to my headphones. Unfortunately I'm experiencing a constant static noise through my headphones. It's not too loud, but is loud enough to be really annoying. The noise only appears when my preamp is on, so it seems safe to assume that it's caused by the preamp.

In addition to having a tube preamp section (6922), the PSU of the preamp is also tube (6N6).

When I tap the preamp tubes (ever so softly) I can hear a microphonic response through the headphones. When i tap the psu tubes there is no noise.

The preamp tubes are electroharmonix. The PSU tubes are cheap chinese..

now to the question.... Is this static likely to be caused by the preamp tubes, or is the fact that they're microphonic unlikely to cause any problems with headphone use? Are the cheap chinese PSU tubes likely to cause this static? Given the choice to ugrade either microphonic EH preamp tubes or cheap chinese PSU tubes, which would you go for first?

Thanks

 

[Negatron]

Quote:

Originally Posted by pomdomz /img/forum/go_quote.gif Hey all I run a tube preamp to a solid state amp, to my headphones. Unfortunately I'm experiencing a constant static noise through my headphones. It's not too loud, but is loud enough to be really annoying. The noise only appears when my preamp is on, so it seems safe to assume that it's caused by the preamp. In addition to having a tube preamp section (6922), the PSU of the preamp is also tube (6N6). When I tap the preamp tubes (ever so softly) I can hear a microphonic response through the headphones. When i tap the psu tubes there is no noise. The preamp tubes are electroharmonix. The PSU tubes are cheap chinese.. now to the question.... Is this static likely to be caused by the preamp tubes, or is the fact that they're microphonic unlikely to cause any problems with headphone use? Are the cheap chinese PSU tubes likely to cause this static? Given the choice to ugrade either microphonic EH preamp tubes or cheap chinese PSU tubes, which would you go for first? Thanks

OK, I'm going to be away from the computer for awhile but before your question can be answered (hopefully) some more information would be helpful.

1. Is the static in one channel or both?
2. Does the static change when you raise and lower the volume control?
3. What are you using for a source / input to the preamp and is the static present when it and any cables in are disconected.
4. Is the static constant? Does it go up and down or contain any hum?
5. Did this just start or have you just put this combination of gear together?
6: What is the amp, what is the preamp and what is the source?
7. Have you recently switched any medication?

That should be good for a start. By the way, tapping on an amp tube will likely make a sound, a rectifier will most likely remain silent.

 

[pomdomz]

Quote:

Originally Posted by Negatron /img/forum/go_quote.gif OK, I'm going to be away from the computer for awhile but before your question can be answered (hopefully) some more information would be helpful. 1. Is the static in one channel or both? 2. Does the static change when you raise and lower the volume control? 3. What are you using for a source / input to the preamp and is the static present when it and any cables in are disconected. 4. Is the static constant? Does it go up and down or contain any hum? 5. Did this just start or have you just put this combination of gear together? 6: What is the amp, what is the preamp and what is the source? 7. Have you recently switched any medication? That should be good for a start. By the way, tapping on an amp tube will likely make a sound, a rectifier will most likely remain silent.

1. Static is in both channels (but both channels have microphonic tubes)
2. Static doesn't change with volume. it is still there at 0 volume
3. various inputs. dacs, cd players, dvd players. changing inputs doesn't change the static. i cannot use no input because it's tube and i think thats naughty
4. constant hum i think
5. i'm not sure if its always been there or not. i used to have a really bad ground loop caused by another piece of gear which has recently been fixed, and it was covering the static
6. preamp is ming da mc67-ha
7. the doc wont let me

the psu tubes aren't rectifiers. it uses solid state rectification

thanks

 

[Negatron]

Quote:

Originally Posted by pomdomz /img/forum/go_quote.gif 1. Static is in both channels (but both channels have microphonic tubes) 2. Static doesn't change with volume. it is still there at 0 volume 3. various inputs. dacs, cd players, dvd players. changing inputs doesn't change the static. i cannot use no input because it's tube and i think thats naughty 4. constant hum i think 5. i'm not sure if its always been there or not. i used to have a really bad ground loop caused by another piece of gear which has recently been fixed, and it was covering the static 6. preamp is ming da mc67-ha 7. the doc wont let me the psu tubes aren't rectifiers. it uses solid state rectification thanks

So the 6N6 is not a western 6N6 which is an odd dual triode, when you said PSU I figured it was part of a regulator in the power supply unit and was tube rectified. I'm to darn old. The tube is an 6H6 actually, sort of a 6922 on steroids.Neither tube is extremly high gain.

I am assuming by static you mean like the crumbling of paper constantly. Microphonics make strange noises but not usually static sounding. Have you cleaned the pins on the tubes?

Again it would help to know what the amp is. If it is very high gain, it may be low level thermal noise from the preamp that with a normal gain amp you wouldn't hear. You say the hum is constant. It should not be there.

It's begining to sound like a preamp into a very high gain amp. How high to you turn your volume control for normal listening?

Disconecting the input on properly functioning tube gear hurts nothing.
NEVER_NEVER_NEVER run a tube power amp without a load or speakers connected, at least not befor saying a possible goodby to your output transformers.

And with that I'm gone for the morning. Oh yeh, regarding ground loops, never ever immediatly break off the center ground pin that is there for your safety and well being. Even if it is responsible for a large number of ground loop problems. Just because I alway break 'em off with audio gear does not mean anyone else should. Ever!

 

[pomdomz]

how high gain is high? i'm not sure what model the amp is because i'm not at home right now

edit: i haven't cleaned the pins. is it possible to do this with anything around the house or should i buy rubbing alcohol?

i keep the volume knob down low for normal listening. below 9 o clock.

thanks again