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Post subject: Twin Reverb with noisy Reverb and microphonic V2 Tube
Posted: Sun Feb 12, 2017 5:36 am
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Hello everybody

I recently purchased a Blackface Twin Reverb Reissue from around 1994. The amp sounds really good, however the reverb is noisy when turned up. I swapped all tubes but the V2 tube position remains very microphonic when the reverb is turned up. I shot a short video on this as well



Any suggestions on this one? Cap change needed?

I am looking forward to your replies, thank you very much.


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Post subject: Re: Twin Reverb with noisy Reverb and microphonic V2 Tube
Posted: Mon Feb 13, 2017 2:08 am
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Welcome to the forum.
You may need a new quiet V3 and V4 these are reverb tubes?

Check if V3 and V6 are 12AT7 not 12AX7
V1 is the first tube from the right , if you look amp from the back

V3 is reverb send tube, V6 is phase inverter.

All other tubes must be 12AX7.
Give brand of each tube

You said you put brand new tube ; V2 ? V2 is often microphonic and it is normal
You said Reverb knob turn up ; wich number on knob ? Try at 3
Volume at wich number ?


Caps, if you are talking about filter caps, are nothing to do with this.

Please delete the second post


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Post subject: Re: Twin Reverb with noisy Reverb and microphonic V2 Tube
Posted: Mon Feb 13, 2017 3:43 am
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Reverb noise seems to be a frequent problem on the reissue amps. I have a DRRI I bought new 2 years ago and it is noisy when the reverb control is set above about 3 and gets louder the higher it is set. Fortunately I never use it above 3!

I have tried changing the tubes in V3 and V4 with negligible impact.


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Post subject: Re: Twin Reverb with noisy Reverb and microphonic V2 Tube
Posted: Sat Feb 18, 2017 11:22 am
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Thank you very much for getting back to me with your comments. My tube setup is as follows:

V1 Fender 12AX7A
V2 Tung Sol 12AX
V3 Electro Harmonix 12AT7EH
V4 Tung Sol 12AX7
V5 Fender 12AX7A
V6 TAD 12AX7A

The reverb gets really noisy when its above 2...


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Post subject: Re: Twin Reverb with noisy Reverb and microphonic V2 Tube
Posted: Sat Feb 18, 2017 11:51 am
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V6 should be a at7, but that doesn't have anything to do with noisy reverb. I have had success with better shielded cables for the reverb, maybe give that a shot?

Good luck!

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Post subject: Re: Twin Reverb with noisy Reverb and microphonic V2 Tube
Posted: Sat Feb 18, 2017 12:12 pm
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Try another 12AX7 , V4 ( from your amp ) and another 12AT7 in V3, a know quiet tube.

These tubes could be noisy.

12AX7 in V6 = more gain = more noise, use 12AT7

That is the only thing you could try with a new shielded wire between reverb and amp.
Remove tank from the amp and clean rca connectors.

If you can't do all of those tests, amp must see a qualified tech.
These are the very fist things to do


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Post subject: Re: Twin Reverb with noisy Reverb and microphonic V2 Tube
Posted: Wed Feb 22, 2017 2:25 pm
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Victor_Reymartinez wrote:
Hello everybody

I recently purchased a Blackface Twin Reverb Reissue from around 1994. The amp sounds really good, however the reverb is noisy when turned up. I swapped all tubes but the V2 tube position remains very microphonic when the reverb is turned up. I shot a short video on this as well


Any suggestions on this one? Cap change needed?

I am looking forward to your replies, thank you very much.


As others suggest, try the known good tubes in the positions where you're hearing problems.

V2 tubes clearly sounds microphonic.
BTW, what volume level is the amp at on both channels?

You say that the reverb is set to max/10, which is going to expose any potential noisy tube.

You also state that the reverb return, V4, is microphonic.
It doesn't sound microphonic to me. It simply sounds like a tube being tapped.
A microphonic tube sounds like the one in V2, and a very bad microphonic tube will actually start to ring even at low volumes, and when it starts ringing it intensifies in level.

I just bought a pair of NOS Ei, Yugoslavian made 12ax7's, and installed the in V1 and V2 of the 68 CDR.
Both are microphonic. One of them sounds like yours even at volume level 2. The other one, even at volume level 2 starts to ring and ring and ring and ring, until I turn the volume completely off.
THAT'S a very bad tube.

I just got replacements last night in the mail, but haven't had a chance to try the out yet.
But, these are "long plate" 12ax7's, and many long plates can be microphonic in combo amps especially when played loudly. In my case, I was only on volume level 2 or 2.5.

As for the reverb send and return, there are tubes that will be noisier than others, and that noise will be dependent on the reverb level. In my 68 CDR the reverb is noisier than I like, but it starts to become noisy when I try to go past 4-5 on the level. Typically I keep it around 3 to 3.5 and it sounds nice there.
I have had a couple of tubes that were quiet in the V3 position, it was either a JJ, Mullard, or EH as I have plenty of those modern made tubes.

V3 send should be a 12at7, but I've had good with 5751's in there are well.
V4 return should be a 12ax7, and I've had good success with 5751's in there as well.

As others have noted the PI should be a 12at7, but 12ax7's work fine in the PI as well. The 12at7 lets the amp stay a bit cleaner as you turn up the volume level compared to a 12ax7, which can get into natural tube distortion at lower volume levels.

I've had good success with 5751's in the PI as well. Right now I'm using an NOS 12at7 Mullard and the amp sounds great.

It seems that most modern pre tube reviews and descriptions say that EH tubes are quiet more often than other tubes. One of the noisiest, though nice sounding tonally, is the Tung Sol 12ax7. I can verify that 12ax7 Tung's are not quiet tubes.

You should get a variety of pre tubes and find a set that lets your amp become it's quietest, that will be base set by which you can then test new or NOS tubes for issues they may have.

My other Fender amp is a 68 CVR and it's reverb is completely silent even turned to level 10. Its a quieter reverb overall and not as finicky about which tubes are sending and receiving in the verb circuit.

Happy tubing! :)


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Post subject: Re: Twin Reverb with noisy Reverb and microphonic V2 Tube
Posted: Sat Feb 25, 2017 4:20 am
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Thank you very much for all your replies! I changed V3 and V4 for new tubes with little to no effect. I will now get some shielded RCA Connectors as a last try :)


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Post subject: Re: Twin Reverb with noisy Reverb and microphonic V2 Tube
Posted: Sat Feb 25, 2017 4:38 am
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[quote="Victor_Reymartinez" will now get some shielded RCA Connectors as a last try :)[/quote]

Any good home stereo cable will do the job.


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