newborn 5f6-a

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es347
Junior tube assistant
Posts: 9
(2/8/04 3:34 pm)
 newborn 5f6-a
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 I recently finished my Bassman and I have some questions and maybe concerns. Here are the voltages.
v1 p1=176 p2=0 p3=2.9 p4=3.2ac p5=3.2acp6=167 p7=0 p8=2.9 p9=3.2ac
v2 p1=195 p2=0 p3=1.15 p4=3.18ac p5=3.18ac p6=334 p7=195 p8=196 p9=3.2ac
v3 p1=280 p2=25 p3=41 p4=3.2ac p5=3.2ac p6=267 p7=26 p8=41 p9=3.2ac
v4 p1=0 p2=3.2ac p3=452 p4=451 p5=-48 p6=451 p7=3.2ac p8=0
v5 p1=0 p2=3.2ac p3=455 p4=449 p5=-48 p6=454 p7=3.2ac p8=0
MY B is 455vdc. Note: The amp seems to work fine There are just a few things I want to be sure of. 1. It doesn't seem as loud as I expected. It stays pretty clean until it pushed past about seven. Right now all I can play it through is four 15" speakers wired in parallel to get 2 ohms. The only other Bassman I have ever played was a reissue a few years back. It seemed as far as I can remember to get louder much quicker than mine. Could this be a result of the audio taper pots I used where as the reissues I think use a linear taper? 2. On the speaker issue, In one of Webers books i read that he stated the the Bassman inverts the signal to the speakers. He went on to say that If you own a reissue you should reverse the speaker leads so that the positive terminals go to the sleeve to make the amp play forwards. Is this something I should do with mine? 3. my power tubes at this time are a old set of groove tubes6l6. They are not matched and are bias to aproxx 33ma and 40ma. My concern is that when I push the amp play aggressively there is a specific part in the tube that will burn/glow brighter with intensity and fluctuate. The plates are not red. I read about this in another post and just to clarify if this is sort of normal or not? Its not just that purple/blue glow you usually see, but a more focused specific part of the tube. The only reason I noticed it was because I was playing in the dark, Don't ask. Anyway I'm sorry this was long winded but your comments would be greatly appreciated. Mike
 
GroundhogKen
Forum Moderator
Posts: 2248
(2/8/04 3:58 pm)
 Re: newborn 5f6-a
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 The two volume pots and the bass should be audio taper--the rest are linear. Your voltages look OK.

Did you use a 12AY7 or an AX7 as the first tube? The AX7 would give much more gain and is probably used in the reissues.

Speakers make a big difference. If you have inefficient speakers, it takes a lot more power to get the same volume as a more efficient set.


Ken

 
es347
Junior tube assistant
Posts: 10
(2/8/04 4:29 pm)
 Re: newborn 5f6-a
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 I'm using a 12ay7 in the first position. As far as the volume output I think I was just expecting something different. i thuoght it would break up sooner. I think the speakers are fooling me too, actually two of them are p.a. speakers and one is a bass speaker, i know thats silly but thats all i can do right now. The only other amp I can compare it to is a silverface Bassman 50, but again its a totally different animal. My main concern is the power tubes. In the other post I think they were referring to the screens? In mine when I hit a hard chord or note, there is a white glow from something in there . It glows bright for a moment then dies down. this is with the volume up around 8 or 9. Should I worry or just Rock On?
 
Wanabejimi
Junior tube assistant
Posts: 40
(2/11/04 1:00 pm)
 Re: newborn 5f6-a
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 I think the lack of volume would probably be a result of inefficient speakers....and likely, you aren't getting the most out of those tubes....since you described them as unmatched and old. If you are using speakers that are designed for PA or bass, that measly 35-40 watts your are hitting them with ain't exactly making them jump. Put a 12ax7 in the first preamp socket. You'll get a bit more grind, but it won't make it any louder. Buy a set of matched 6l6's and find someone with a efficient speaker cab you can borrow.
 
es347
Junior tube assistant
Posts: 11
(2/11/04 4:58 pm)
 Re: newborn 5f6-a
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 Thanks for the reply, I have four Jensen P10R speakers to use when I eventually get my cabinet. I managed to reconfigure my temporary speaker set up using one of the Jensens and I think that made a difference also.
Have you or anyone else heard about the Bassman amp inverting the signal? In Gerald Weber's book he says that the speakers should be hooked up with the positive terminals going to the sleeve and the negatives going to the tip.
 
GroundhogKen
Forum Moderator
Posts: 2258
(2/11/04 10:19 pm)
 Re: newborn 5f6-a
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 I've always thought that "amp plays forward" stuff was hogwash, but I've never experimented to see. I don't see how it could make any difference electrically.

Of course, if one of the speakers was wired backwards or marked wrong that would make a big difference.
Ken
 
 
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