Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: pbman1953 on December 29, 2011, 07:44:31 am
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HI
I was wondering if the newer re-issue Fender tweed Basman's are able to be biased. Some of the newer Fenders have a fixed bias
Thanks
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The Reissue '59 Bassman is fixed bias and is not adjustable (unless you modify it).
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Had a feeling, Thanks & Happy New Year!
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Actaully one last one,
for this amp-
SS rect or tube?
There's a GT tube in there now but a SS also left in the the bottom of the cab
Amp has-
Pre's-EH
Power- Tung Sol- 5881
Trying to helps a friend
Thanks
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There's a complete service manual in Doug's schematic library.
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Within reason, rectifiers are a matter of choice, but they do usually need a rebias after a change. Most people like Tube, GZ34. Doug sells a strong Sovtek. Has less sag than other tubes, but a little more than SS. Then there re 5u4 and variations. Prettycheap NOS on ebay. Had a little more sag than GZ34. Then the 5y3 which has the most sag of all mentioned. I personally like either 5u4 or 5y3 in tweed amps as I prefer the sag. Weber sells a copper cap SS rectifier with sag as well which is a good choice for durability, but if you fine a Bendix 6106 NOS which is the same as a 5y3, it will last longer than people usually have amps. If you plan to roll Rectifier tubes, you will need to learn how to bias the amp. It will cause a resistor change or conversion to adjustable bias. IMO, the rectifier tube is the most important tube for overall tone. It sets the stage for how the amp will operate. It all comes down to playing style. I just built a Bassman and the tubes I ended up with are V-1-5751 RCA NOS, V-2 12ax7 RCA NOS, V-3 12ax7 RCA NOS all black plates. Power Tubes are very well matched Winged "C" 6L6GC and a Bindex 6103 5Y3. Power Tubes bias set -40mv. I am waiting on some NOS 5881 Tung-sol to try out. Word is these have the sweetest sound in a tweed bassman.
Sorry for so much info, but if you can get NOS tubes IMO there is a significant tone enhancement. For new Rectifier with medium sag I think the EH 5u4gbeh is the best for the money. They are around $15. Lots of people like JJ's, but for a rectifier they do not have very much sag. Might as well use GZ-34. BTW, the Mullard GZ-34 NOS is the best, but they are overpriced for Guitar amps.
BTW, Doug sells all the tubes I mentioned except he does not deal in NOS tubes. I assume it is because it is difficult to warranty old tubes. Just look above and you will see a link to Tubes/Valves.
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Ed, thanks for the info and I'll pass that on to my freind
One more for you-
I have my Sunn 2000s with Weber copper caps. It's been so very long since I've heard the amp with a tube rect. Should I bother going back?
Am I missing out on anything?
Thanks
Rich
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The correct Bendix number is 6106.
Those are remarkable tubes. Plug them into a tube tester and 45 seconds to one minute later, they will show NO emission. They really take a heck of a long time to warm up. Quite the fetish item = expensive.
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Ed, thanks for the info and I'll pass that on to my freind
One more for you-
I have my Sunn 2000s with Weber copper caps. It's been so very long since I've heard the amp with a tube rect. Should I bother going back?
Am I missing out on anything?
Thanks
Rich
Probably not. The copper cap essentially mimics a tube rectifier by adding series resistance to add voltage drop and sag.
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Thanks
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The correct Bendix number is 6106.
Those are remarkable tubes. Plug them into a tube tester and 45 seconds to one minute later, they will show NO emission. They really take a heck of a long time to warm up. Quite the fetish item = expensive.
My Mistake, it is 6106.
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I like the Weber copper cap rectifiers. The only thing is different rectifier Manufacturers will have slightly different tonal qualities. For instance webers version of the GZ-34 is not the same as a Mullard which is not the same as a Sovtek which is not the same as a JJ. Kind of splitting hairs here. I have some Mullards I got before the got so expensive and there is a noticeable difference. In the 5y3 the Bendix 6106/5y3 is my favorite. There were some made with this in them JAN- CHY 5Y3WGTA. Military. If ever in doubt, you cannot go wrong with RCA NOS. This is my opinion of course. But again, tube choice is very subjective and lends itself to players style and type of amp. For instance, I don't like 5y3's in JTM-45 Marshalls as they have too much sag from what I expect from a Marshall amp. I use GZ-34 here and really like the copper version from Weber