favorite tubes and speakers for thunderbass heads.

kinda just wondering what the title states. if anyone instead of 6l6's, has put el34's in their head? or if not, what's your fav 6l6 to stick in it? preamp as well? speakers? thanks for the opinions.

cj in 5...4...3...2...1...

haha. he does indeed know quite a bit about guild amps. without him and this board, i'd be pretty lost. so thank you.

cosmic erosion said:

kinda just wondering what the title states. if anyone instead of 6l6's, has put el34's in their head? or if not, what's your fav 6l6 to stick in it? preamp as well? speakers? thanks for the opinions.

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I think Darryl probably has EL84s in his head.

Definitely not Solid State !!!

cosmic erosion said:

....if anyone instead of 6l6's, has put el34's in their head? or if not, what's your fav 6l6 to stick in it? preamp as well? speakers? thanks for the opinions.

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Hi CE; a little background first; Guild Thunderbass heads came in 2, 3, and 4-tube preamp configurations; some of the latter were fittted w/ 6GF7 screen voltage regulators (Quantum) and there was apparently another larger bass amp '747' that, while built, may have never flown. It's seen in ads but not many actual sightings.

Some / many / all the earlier TBasses w/ 2-tube preamps were fitted w/ 7591s; our BBer ThunderCat has this model. The 3 and 4 tube preamp models were either 8417s or, later, 6L6. That is, as far as I know, none of the Guild Thunderbass amps ever sported the venerable EL34/6CA7. The EL34 was a favorite of Marshall amps; a quad to get 100 watts of steaming tuber power. The other application for the EL34 is hi fi: pic of Marantz 8 below - 35 wpc of arguably the finest US commerical design ever manufactured.



The chart below compares the electrical pinout connections for the 6L6, 8417, EL34, and 7591. Except as noted, only the 6L6 and the 8417 are drop-in physical replacements for each other. As you can see, the 7591 is similar to both however the EL34 doesn't resemble any of the others.



The 8417 is no longer being supported; I have an '8417' 4-tube preamp Thunderbass that is on my bench waiting to have its power supply overhauled and altered to support the 6L6; see thread below for discussion of converting from 8417 to 6L6 operation: http://letstalkguild.com/phpBB2/viewtop ... f=7&t=5394 In short, without comprehensive re-wiring and changing the power supply, no way to get an EL34 into an otherwise stock Thunderbass.

Both the 3 and 4-tube preamp Thunderbass amps use a 7247/12DW7 as the driver; we have a Canadian member who runs a 12AX7 there because (1) it works, and (2) he is Canadian... and it will work however the circuit is designed to drop considerable voltage on the 2nd stage of this tube and, these tubes are in plentiful supply and would recommend nothing other than a 7247/12DW7 .... unless of course you are Canadian.... :wink:

There are just too many 'flavors' of 12AX7s and 6L6s to cover here. Suggest in hard copy either / both Gerald Weber's book on amps or even Aspen Pittman; or just searching the web to read. The 6L6s often carry suffixes indicating source, construction materials, and people who know these tubes well are able to make close distinctions - as another of our BBer's calls it: 'Cork Sniffing'. It's a certainty than some will do good with bass and mids, others shine w/ highs, some don't last, some do. On and on..... On the subject of speakers, most of my gear is low power and I buy Weber Jensen clones; well-made reproductions of simple, staightforward designs from back in the day. Since I am from back in the day .... you see where I'm going.

As a suggestion, I'd try some vintage 60s 12AX7s and 6L6s for variety but if I want my amp to come on, stay on, let me push it, then I think I want newer; and save the 'specials' for fooling around.

that's so weird. my two preamp one has 6l6's and the little tube chart in the chasis says 6l6 on it. now i'm really confused, and need to get my digital camera working again.

cosmic erosion said:

that's so weird. my two preamp one has 6l6's and the little tube chart in the chasis says 6l6 on it. now i'm really confused, and need to get my digital camera working again.

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Hi CE: check these brochures; http://letstalkguild.com/phpBB2/viewtopic.php?f=7&t=5831 According to them, your ThunderBass 2-tube preamp model, at least in the later config, includes a pair of 6L6s. As a 'working theory', the 2-tube preamp model may have started w/ 7591s, then 8417s, then gone to 6L6s.... If it weren't such a pain in the rectifier, I'd say all this confusion was part of the .... ahem ..... charm :evil: cj

mines the one with the tubes 12ax7, 7247, and 2 6l6's. even has the matching 1x15 cab.

cosmic erosion said:

mines the one with the tubes 12ax7, 7247, and 2 6l6's. even has the matching 1x15 cab.

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Then you're in good shape! have a schematic for it? Original filter caps still in it? Speaker make? cj

i'm still trying to find the schematic. i don't think i have one. i just had the caps replaced. they were done for. the speaker is original, but it has no id on it at all. so i have no idea what kind it is. no markings or anything.

cosmic erosion said:

i'm still trying to find the schematic. i don't think i have one. i just had the caps replaced. they were done for. the speaker is original, but it has no id on it at all. so i have no idea what kind it is. no markings or anything.

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Hi CE; no printed numbers on the speaker at all? Usually found on the back rim or sometimes the magnet. If none whatsoever and if speaker hasn't been repainted as part of reconing, then chances are you have a 'no namer' in there. The end of the bad news; unless you have an unusally good speaker, normally get a tone uptick in replacing it. If replaced with new, expect 5 - 10 hours of play before the speaker cone breaks in - loses some of it's original stiffness. cj

cosmic erosion said:

i'm still trying to find the schematic. i don't think i have one. i just had the caps replaced. they were done for. the speaker is original, but it has no id on it at all. so i have no idea what kind it is. no markings or anything.

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I can help with that.. send me a pm or email with your email and I'll send you a pdf of the schematic.

And for the record. I think the EV SRO speakers are the best.

capnjuan said:

we have a Canadian member who runs a 12AX7 there because (1) it works, and (2) he is Canadian... and it will work however the circuit is designed to drop considerable voltage on the 2nd stage of this tube and, these tubes are in plentiful supply and would recommend nothing other than a 7247/12DW7 .... unless of course you are Canadian.... :wink:

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I run the 12AX7 there because it came with the amp, and I just haven't developed the energy to chase down a 7247. Not just a Canadian trait - any lazy person anywhere in the world might have done the same. I will get it done, someday soon . . .

I use a reconed 2x10 Guild/Hartke cab. Lovely and fat.

A little more drive into the output tubes as well.

john_kidder said:

capnjuan said:

we have a Canadian member who runs a 12AX7 there because (1) it works, and (2) he is Canadian... and it will work however the circuit is designed to drop considerable voltage on the 2nd stage of this tube and, these tubes are in plentiful supply and would recommend nothing other than a 7247/12DW7 .... unless of course you are Canadian.... :wink:

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I run the 12AX7 there because it came with the amp, and I just haven't developed the energy to chase down a 7247. Not just a Canadian trait - any lazy person anywhere in the world might have done the same. I will get it done, someday soon . . . I use a reconed 2x10 Guild/Hartke cab. Lovely and fat.

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Hi John: jus' joshing ... and appreciating your and Canadians' "if it ain't broke ..." attitude. If your amp is 8417-based, then you have a guitar channel that CE's 2-tube model doesn't. cj

sfIII said:

I can help with that.. send me a pm or email with your email and I'll send you a pdf of the schematic.

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Hi Howard; have sent you my email address too but, IIRC, we went through this with ThunderCat's amp (2-tube preamp like CE's and pictured below) and I think your schematic is for a 3-tube preamp? (pair 12AX7s and 1 7247 driver) See also this thread Guild / Avent amp brochures contains pics of ThunderStar bass amp; single channel, two inputs. The (later?) ThunderBass 1A Deluxe two channels, two inputs each. Anyway, I'd appreciate the schematic too; the one not found so far is the 2-tube preamp version. Thank you. cj

I think Darryl probably has EL84s in his head.

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Nope. In my pants.

Darryl Hattenhauer said:

I think Darryl probably has EL84s in his head.

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Nope. In my pants.

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BIG problem if your main squeeze has a 7-pin socket !

Coastie,

You know my sister?

Darryl Hattenhauer said:

Coastie,

You know my sister?

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I believe she toured here once with the circus.

Didn't see her though.