DRRI issue - microphonic? - now fixed

Darrell · March 24th, 2006, 03:07 PM

It seems that my DRRI is somewhat microphonic when I am playing. Has anyone heard of that?

I thought I was running the pickups to close on the guitar, and this was the issue....so I backed them way back...and the issue is still there.

I started to eliminate pedals from the mix last night...but the microphonic is still there. I forgot that I had one pedal on before I shut down last night. I will see if it is the culprit tonight.

Darrell · March 25th, 2006, 11:10 PM

I bought the amp used a few months ago.

So, I went down the tube chart comparing tubes in the amp with what is SUPOSE to be in the amp.

All of them were right except one. The second from the end. It is an AT7 and should be an AX7.

It just so happens that I carry an extra AX7. So I popped it in.

And the problem was solved.

I don't know if it was a bad tube, or what, but that was the issue.

milocj · March 26th, 2006, 02:26 AM

I take it you mean the tube that is the second one from the right hand side when looking at the back of the amp? That's the first gain stage for your vibrato channel and it has the most effect on the sound for that channel.

It would be okay to use a 12AT7 in that slot if you wanted a little bit less gain so the problem wasn't that the "wrong" tube was in that socket, but that particular tube had gone microphonic. Since this is the first gain stage a microphonic tube gets amplified throughout the rest of the signal chain. If you get a problem like this again you can take a pencil and tap the eraser on each tube while listening with the amp turned on. The microphonic tube should be pretty obvious when you tap on that one.

Darrell · March 27th, 2006, 12:15 PM

is it commonplace to have a "microphonic" tube, or is this just a sign of a "bad" tube altogether?

I may run that little test on the rest of the tubes.

Thanks

Scotland · March 27th, 2006, 01:58 PM

Tubes can go microphonic regardless of age or brand, some brands are worse than others but generally you would hear it in an instant.

Darrell · March 27th, 2006, 02:43 PM

I don't have the best hearing. I am actually deaf in one hear. It wasn't until the slap back and reverb carried it back to me after I stopped playing, when I knew I had an issue.

March 24th, 2006, 03:07 PM	#1 (permalink)
Darrell Friend of Leo's Join Date: Mar 2003 Location: Houston, Texas Age: 48 Posts: 2,528	DRRI issue - microphonic? - now fixed It seems that my DRRI is somewhat microphonic when I am playing. Has anyone heard of that? I thought I was running the pickups to close on the guitar, and this was the issue....so I backed them way back...and the issue is still there. I started to eliminate pedals from the mix last night...but the microphonic is still there. I forgot that I had one pedal on before I shut down last night. I will see if it is the culprit tonight. __________________ "Yeap, I like the American Standard Telecaster, I can even live with one a them PCB amps, and I even use one a them mul-tie-effects things too."

March 25th, 2006, 11:10 PM	#2 (permalink)
Darrell Friend of Leo's Join Date: Mar 2003 Location: Houston, Texas Age: 48 Posts: 2,528	Problem solved I bought the amp used a few months ago. So, I went down the tube chart comparing tubes in the amp with what is SUPOSE to be in the amp. All of them were right except one. The second from the end. It is an AT7 and should be an AX7. It just so happens that I carry an extra AX7. So I popped it in. And the problem was solved. I don't know if it was a bad tube, or what, but that was the issue. __________________ "Yeap, I like the American Standard Telecaster, I can even live with one a them PCB amps, and I even use one a them mul-tie-effects things too."

March 27th, 2006, 12:15 PM	#4 (permalink)
Darrell Friend of Leo's Join Date: Mar 2003 Location: Houston, Texas Age: 48 Posts: 2,528	Is it commonplace is it commonplace to have a "microphonic" tube, or is this just a sign of a "bad" tube altogether? I may run that little test on the rest of the tubes. Thanks __________________ "Yeap, I like the American Standard Telecaster, I can even live with one a them PCB amps, and I even use one a them mul-tie-effects things too."

March 27th, 2006, 01:58 PM	#5 (permalink)
Scotland Poster Extraordinaire Join Date: Mar 2003 Location: Aberdeen, Scotland, Yewrup Age: 54 Posts: 6,612 3 Photos	Tubes can go microphonic regardless of age or brand, some brands are worse than others but generally you would hear it in an instant. __________________ All those who believe in psycho-kinesis, raise my hand !

March 27th, 2006, 02:43 PM	#6 (permalink)
Darrell Friend of Leo's Join Date: Mar 2003 Location: Houston, Texas Age: 48 Posts: 2,528	Scotland I don't have the best hearing. I am actually deaf in one hear. It wasn't until the slap back and reverb carried it back to me after I stopped playing, when I knew I had an issue. __________________ "Yeap, I like the American Standard Telecaster, I can even live with one a them PCB amps, and I even use one a them mul-tie-effects things too."

March 26th, 2006, 02:26 AM	#3 (permalink)
milocj Tele-Meister Join Date: Aug 2005 Location: Michigan Posts: 453 3 Photos	I take it you mean the tube that is the second one from the right hand side when looking at the back of the amp? That's the first gain stage for your vibrato channel and it has the most effect on the sound for that channel. It would be okay to use a 12AT7 in that slot if you wanted a little bit less gain so the problem wasn't that the "wrong" tube was in that socket, but that particular tube had gone microphonic. Since this is the first gain stage a microphonic tube gets amplified throughout the rest of the signal chain. If you get a problem like this again you can take a pencil and tap the eraser on each tube while listening with the amp turned on. The microphonic tube should be pretty obvious when you tap on that one.