Reverb driver tube - advice needed

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r_cod_81

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About a year and a half ago I bought a 2nd hand studio preamp made - according to the hand-written numbers on the circuit boards - in 1989/1990. I've always though that the reverb, while sounding nice, was rather understated. I had left it as I had myriad other things to fiddle with but I did find that when sticking a pedal in the effects loop for a lead boost the reverb became much more pronounced due to the extra gain in the signal.

The current driver tube is an 12AT7; and judging by the state of it I'm guessing it's the original. Could I swap it for a higher gain tube and if so what type should I go for? I've been told a 12AX7 would be possible.

Cheers for any ideas!

Richard
 
I wouldn't do that. If it doesn't harm the amp you'll most likely end up with more noise due to the higher wattage.
 
i good, inexpensive vintage 12AT7 like a GE would probably last the life of the amp. I have about 7 of those that i use as PI tubes sometimes.
 
my heartbreaker came with a 12AX7 as the reverb driver tube. I switched to a NOS 12AT7 tube and though the reverb did sound better, it was not as pronounced.
 
The 12AT7 is in there to get more of a current swing going into the reverb transformer. Don't think a 12AX7 will help much because these tubes are to get more of a voltage swing - they don't drive low impedance loads too well. Fend*r uses both triodes of the 12AT7 in parallel to drive a reverb transformer with an 8 ohn secondary in their designs since the 1960's and it produces about 1 watt of power. You can actually hook up a speaker to the tank input and it would drive it. I don't think you can get there from here without tweaking the actual circuit and to do that we would probably have to know the primary impedance of the reverb drive transformer and other things. All this is out the window if you think the Studio Pre is broken some how.

Sorry to harsh your buzz. :( - Pat
 
shytfayse said:
The 12AT7 is in there to get more of a current swing going into the reverb transformer. Don't think a 12AX7 will help much because these tubes are to get more of a voltage swing - they don't drive low impedance loads too well. Fend*r uses both triodes of the 12AT7 in parallel to drive a reverb transformer with an 8 ohn secondary in their designs since the 1960's and it produces about 1 watt of power. You can actually hook up a speaker to the tank input and it would drive it. I don't think you can get there from here without tweaking the actual circuit and to do that we would probably have to know the primary impedance of the reverb drive transformer and other things. All this is out the window if you think the Studio Pre is broken some how.

Sorry to harsh your buzz. :( - Pat
Click to expand...

+1

IMO a great 12AT7 to use for a Reverb Driver is the NOS Mullard CV4024 (they make a great PI as well). I have purchased 4-5 of them from eBay seller BNB Tubes with no issues at all.

http://www.ebay.com/itm/Genuine-Mul...509?pt=LH_DefaultDomain_0&hash=item4840e5b23d

Dom
 
I would call Mesa to find out what they put in that model when it left the factory. I found this review which says the stock reverb driver tube is a 12AX7.

http://www.dolphinstreet.com/amps/mesa_boogie_studio_preamp/

However, even that could be wrong. I always call Mesa when I find an amp to check out things like tubes, reverb tank type used, and replacement part availability. But I am neurotic that way :lol:

Dennis
 
jpdennis said:
I would call Mesa to find out what they put in that model when it left the factory. I found this review which says the stock reverb driver tube is a 12AX7.
Click to expand...

I contacted th UK distro. centre (West side Music in Glasgow) and they said that the Studio Pre was designed with a 12AT7 as the reverb driver/ receiver. I'll get a new one in there at some point and se what the effect is. Cheers for your responses guys!


Richard
 
domct203 said:
shytfayse said:
The 12AT7 is in there to get more of a current swing going into the reverb transformer. Don't think a 12AX7 will help much because these tubes are to get more of a voltage swing - they don't drive low impedance loads too well. Fend*r uses both triodes of the 12AT7 in parallel to drive a reverb transformer with an 8 ohn secondary in their designs since the 1960's and it produces about 1 watt of power. You can actually hook up a speaker to the tank input and it would drive it. I don't think you can get there from here without tweaking the actual circuit and to do that we would probably have to know the primary impedance of the reverb drive transformer and other things. All this is out the window if you think the Studio Pre is broken some how.

Sorry to harsh your buzz. :( - Pat
Click to expand...

+1

IMO a great 12AT7 to use for a Reverb Driver is the NOS Mullard CV4024 (they make a great PI as well). I have purchased 4-5 of them from eBay seller BNB Tubes with no issues at all.

http://www.ebay.com/itm/Genuine-Mul...509?pt=LH_DefaultDomain_0&hash=item4840e5b23d

Dom
Click to expand...

this, but that's wayyyy too high. i've bought them for 15$ at most! just gotta watch the auctions.
Great tooob though!
 
Hey folks, a happy new year to all!

A wee update: I ordered and received me a shiny new 12AT7 (a Russian-made Electro-Harmonix from Andertons in the UK) and it sounds positively cavernous; pun absolutley intended!

I took the original tube out and the pins were very corroded - date of '1990' on the circuit board, VERY old-looking Mesa tube - so I filed them a wee bit to get a good connection and then swapped it into the preamp of a 5W class A that I built recently and the tube works fine! I might put it back in the studio's reverb circuit if I can be bothered de-racking it again to see how it sounds compared to my new tube.
 

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