Blackbox
Joined: Mar 19, 2017
Posts: 50
Davis, CA
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Posted on May 15 2018 01:36 PM
I know there are some older threads about this, but figured I'd start a fresh discussion as I'm currently going through this. I'm messing around with NOS tubes in my 62' Fender Reverb unit. Bought a couple of overpriced RCA 6k6s to swap out with the unlabeled tube that came with it when I purchased it. I noticed an immediate increase in the focus of the reverb: it added depth but with more room before the notes become "washed out," you might say. Replaced a modern 12at7 with a vintage RCA, noticed less noise...not sure if it was that big of a difference. I also picked up a few vintage Mullard 12at7s to try. I swapped out another Russian EH 12ax7 that was in the unit with a vintage RCA...didn't notice a real difference. Going to try a Mullard in there too once it arrives.
Any thoughts people have on these units and tubes would be appreciated. Just trying to milk the most tone and usability I can get out of this thing.
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reventlos
Joined: May 23, 2006
Posts: 209
Costa Mesa
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Posted on May 15 2018 11:49 PM
Hopefully we'll get a lively discussion going on NOS vs current production stuff. I've also experimented with all kinds of tubes in my Reverb Units and other vintage Fender amps. I've formed a few opinions, along with some favorite tube types. It would seem that, more often than not, Fender gear from the '60's came with RCA tubes, and later the etched glass GE stuff. (BUT, just like with speakers, it's whatever they could get a good deal on in bulk). The notable exceptions are the Tung Sol 5881 power tubes that were OEM in lots of late 50's early '60's amps, and the RCA labeled Mullard GZ-34/5AR4 rectifiers found in several of the combo amps. Back to your Reverb: the 12AT7 probably won't affect the tone much, so I use pretty much anything, new or old. After throwing about six different 6K6's in mine, all NOS USA stock, I ended up putting back the funky orig RCA with a zillion hours on it. I just liked it better. (I'm definitely NOT an expert, but my impression is that Reverbs don't run at as high voltages as the amps do, and the tubes tend to last forever). As far as 12AX7's go, my all time favorite, in any application, are the Amperex made in Holland Bugle Boys. Some guys like their Mullards, some their Telefunkens, and nothing wrong with RCA's, but I've found the Amperexes to be just about perfect in whatever I've put them in. Along with everything else vintage and NOS, they've gotten stupid expensive, but don't be afraid to try a couple of used/good ones.
On a related note, any feedback on the recent production Tung Sol re-issues?
Last edited: May 15, 2018 23:53:49
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Blackbox
Joined: Mar 19, 2017
Posts: 50
Davis, CA
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Posted on May 15 2018 11:57 PM
Replacing the 6K6 with a vintage RCA was definitely the biggest bang for the buck so far for me.
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vintagesurfdude
Joined: Nov 28, 2011
Posts: 795
Prescott Valley, AZ
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Posted on May 16 2018 01:57 AM
Blackbox wrote:
Replacing the 6K6 with a vintage RCA was definitely the biggest bang for the buck so far for me.
Same here. RCA 6K6
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Redfeather
Joined: Jul 30, 2016
Posts: 853
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Posted on May 16 2018 03:00 AM
I recently swapped a vintage Tung-Sol 6K6GT into my reissue to eliminate the overdriving that the 6V6GT was causing and it worked like a charm. Beyond that, I think the nuances of tone from a reverb unit are lost on me. It changes the dry tone so extremely anyway that the little differences between tubes don't add up to much, to my ear.
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DeathTide
Joined: Apr 13, 2018
Posts: 1330
New Orleans
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Posted on May 16 2018 08:16 AM
I freely admit don’t know much about this, but I am interested. Are you guys rebiasing everytime you change a tube? Don’t you need fancy stuff to figure out the output of each tube? And then tweak something weird inside the amp? Or is that not a big deal with preamp tubes vs. power tubes?
I ask because I’ve thought about changing the power tubes but I don’t wanna wait two weeks for the amp dude to rebias just to hear if there’s a difference. I also admit I have done zero research!
Dan Izen
— Daniel Deathtide
Last edited: May 16, 2018 08:16:59
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Brian
Joined: Feb 25, 2006
Posts: 19190
Des Moines, Iowa, USA
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Posted on May 16 2018 08:59 AM
You only need to bias power tubes, and then only in certain circuits (most Fender amps would be included here).
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Blackbox
Joined: Mar 19, 2017
Posts: 50
Davis, CA
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Posted on May 16 2018 11:01 AM
I haven't been doing any sort of rebias when switching out the 6k6.
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Tailrocker
Joined: May 09, 2018
Posts: 63
Morgantown, WV
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Posted on May 16 2018 12:22 PM
The Fender Reverb is cathode-biased. Swap away.
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DeathTide
Joined: Apr 13, 2018
Posts: 1330
New Orleans
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Posted on May 16 2018 02:12 PM
Ah! Copy that thanks for the info!
— Daniel Deathtide
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Blackbox
Joined: Mar 19, 2017
Posts: 50
Davis, CA
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Posted on May 16 2018 07:54 PM
After going through a bunch, settled on the RCA 6k6, a Mullard 12at7 and a Telefunken 12ax7. I tried a Mullard 12ax7 but it was a bit too aggression. The Telefunken seemed cleaner and tighter.
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