surferXmatt
Joined: Aug 27, 2008
Posts: 1570
New York
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Posted on Aug 12 2009 07:26 AM
Ordered a nice RCA 6K6 tube for my reverb unit, here are my initial thoughts:
It seems to have reduced the amount of overdrive I used to get while playing through the unit. I have noticed a bit more bass content in the tone. It has given my adjustment knobs a wider range, I can know crank the knobs past 6 with out it sounding ridiculous. My wife comments that "It doesn't sound as "Pingy" anymore!". The tube has really taken out the harshness of the unit and made it more mellow. In a way I kind of miss the harshness - it was good for an aggressive sound, but not appropriate for much of what I play.
Anyway, that is all for now - just sharing.
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mad_dog
Joined: Sep 23, 2008
Posts: 349
Montclair, NJ
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Posted on Aug 12 2009 08:51 AM
Surfer:
If you have any better than decent pre-amp tubes to try, that would be worth the effort. My RI Fender came with pretty nowhere 12at7 and 12ax7 tubes. Better ones made a noticeable difference.
MD
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surferXmatt
Joined: Aug 27, 2008
Posts: 1570
New York
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Posted on Aug 12 2009 08:55 AM
As of now - I have the original tubes - have not pulled them out yet, but I believe they would be the same as the 6V6 tube I pulled out - which was made by Sovtek. I will look in to replacing the others, any suggestions? I think my drip factor is down slightly, maybe I am crazy?!
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kick_the_reverb
Joined: Feb 26, 2006
Posts: 1337
Escondido, CA
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Posted on Aug 12 2009 10:34 AM
In my reissue tank, the biggest improvemnet was when switching the 12AT7 to an old US made tube. I think at the time it was a GE, but I have been using RCA for years now.
— The Scimitars
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4AB3C1B
Joined: Feb 09, 2007
Posts: 71
Montreal, Canada
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Posted on Aug 12 2009 11:32 AM
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dp
Joined: Feb 26, 2006
Posts: 3546
mojave desert, california
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Posted on Aug 12 2009 11:50 AM
in my RI Fender Unit,
installed a NOS GE 6K6...
a NOS Mullard 12AT7...
and a NOS GE JAN 5751 (lower gain military spec for 12AX7A)...
smooth sailing!
Last edited: Aug 16, 2009 02:35:43
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groucho26
Joined: Jan 23, 2007
Posts: 111
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Posted on Aug 12 2009 11:15 PM
Ah, yes, the 6K6 discovery - welcome! (Uh, I am a fan if you haven't guessed).  Re preamp tubes, try a bunch of them - almost any older US made tube will also add to the vintage character and great sound.
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scotstandard
Joined: Nov 09, 2008
Posts: 1140
Davenport Iowa
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Posted on Aug 13 2009 12:15 AM
When it comes to pre amp tubes try lots and lots and lots of them, there is no right or wrong answer.
If you were going to buy new id say JJ has my vote
NOS stuff is really cool if you find the RIGHT tube.
but trust me its a night and day diffrence with better tubes.
The harsness you speak of can be really cool, i play a more aggresive dick dale tone most of the time and kind of like some grit from the tank.
The C10 mod mellows it out even more, its nice but not a life or death mod. I sugest getting a double pole double through DPDT switch and putting the stock cap on one side and the Silver mica cap on the other, the stock cap is more harsh than the silver mica and can be cool for some apps.
just drill a tiny hole in bottom of chassis (where the AC plug is on vintage tanks) and put it there.
if your not super handy i can walk you through it.
or if you want send it to me and ill do it for you.
but you can do it. im really intregued about putting old springs in new tanks...somebody was taking about it here and id like to try it. if it helps ill send you some springs. I only have 1000 of them here.
— Give me reverb or give me death!
facebook.com/onenightstandards
https://www.youtube.com/scotstandard
scotstandard@yahoo.com
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Ruhar
Joined: Jun 21, 2007
Posts: 3909
San Diego, CA
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Posted on Aug 13 2009 10:29 AM
I've actually gone back to using a 6V6 in my mid 90s reissue. I have a NOS RCA in there and was pleasantly surprised by the tone. Much more drip at lower settings and not as harsh as the 6k6 in my newer reissue.
— Ryan
The Secret Samurai Website
The Secret Samurai on Facebook
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surferXmatt
Joined: Aug 27, 2008
Posts: 1570
New York
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Posted on Aug 13 2009 10:46 AM
Thanks for all of the suggestions every one.
Scot: You are too generous. I can tinker on my own to some degree.  Not sure how far I will take it with the tank, but we'll see.
I will order some NOS 12at7 and 12ax7 tubes this weekend probably.
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scotstandard
Joined: Nov 09, 2008
Posts: 1140
Davenport Iowa
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Posted on Aug 13 2009 10:41 PM
the mod is pretty easy if nothing else i you can have the silver mica cap sent here and ill do it up on the DPDT for ya and walk ya through the rest.
if you can solder at all you can do it.
— Give me reverb or give me death!
facebook.com/onenightstandards
https://www.youtube.com/scotstandard
scotstandard@yahoo.com
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Hoosier-Hodad
Joined: Jun 09, 2009
Posts: 135
San Jose, CA.
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Posted on Aug 14 2009 12:38 AM
The tube selection is going to have without a doubt the most impact on changing your tone as the tubes are the primary signal drivers. Experiment with different tubes as suggested in this thread. I like the JJs as new tubes, but I have a pretty decent cache of NOS tubes including lots of 6K6 tubes. Using the 6V6/12AX7 combination is way over the top IMO, unless of course you like the extra gain. I want my reverb sparkling clean and prefer to drive the amp. I dont like harsh preamp distortion. The best 6K6 I have is a Tung-Sol. These are legendary tubes with amazingly long lives on par with the Telefunken (100,000+ hours). I like carbon composition resistors as well. The Mallory caps seem to be a little smoother too. I take all my queues from what I see in the old Fenders. You can look at lower gain tube substitutes like the 12AY7 (gain of 40) or 5751 (gain of 60 70). I have a few 7025s that I use for the reverb recovery. The Fender spec is V1 7025, V2 12AT7 and the 6K6GT to drive the input to the two-spring reverb tank and then to one half of the 7025 triode. Ive wondered what a tube rectifier would sound like in a reverb. The silicon rectifiers were a very new innovation for Fender and the industry at the time. This would be the beginning of the solid state era.. soon the photocell tremolo would go into the Blackfaces.
6K6 Data Sheet
http://frank.pocnet.net/sheets/093/6/6K6GT.pdf
6V6 Data Sheet
http://frank.pocnet.net/sheets/093/6/6V6GT.pdf
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dannylectro
Joined: Aug 18, 2008
Posts: 368
Orange, CA
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Posted on Aug 15 2009 06:57 AM
A real NOS 6K6 is the only way to surf if ya ask me.
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SURFmole
Joined: Nov 22, 2007
Posts: 901
Portland, OR
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Posted on Aug 15 2009 02:37 PM
Hoosier-Hodad
Ive wondered what a tube rectifier would sound like in a reverb.
The same as the SS rectifier. You're not going to get much sag out of a unity gain (or actually slightly less than unity gain) preamp. Even with amps you can get the same effect with a sag resistor in the power supply.
— www.apollo4.com
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Icetech
Joined: Dec 16, 2006
Posts: 892
Macomb Mich
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Posted on Aug 15 2009 10:16 PM
My homemade unit is built in a old princeton reverb chassis that had a tube rectifier, so i just used it and it works fine, i don't think sag is an issue in something using very little power
— I wanna play just like him when i grow up...
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Hoosier-Hodad
Joined: Jun 09, 2009
Posts: 135
San Jose, CA.
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Posted on Aug 15 2009 11:46 PM
In this case I would be looking for some additional touch sensitively (sag) that youll find in tube rectified Fender tweed era amplifiers. The tweed era Fenders all have this quality that many find desirable especially for the blues. That said, I think because youre driving the signal into a delay generating device any sag or touch sensitively would probably be negated in this circuit. That and the reverb is in path to the amp. Im sure the Hammonds used TR out of necessity in their original reverb implementations.
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