NAD: Supro Thunderbolt

[dhsierra1]

The percussionist in one of the bands I'm in recently inherited a rather unusual gem and I thought some of you might enjoy seeing it as it's something you don't see everyday.

His father was for many years (late 50s through the early 80s) an active pro double bassist in the SF Bay Area. The usual gigs: jazz casuals, corporate functions, weddings, recording for local/regional commercials, etc.

He died several years ago and the family has slowly been going through his effects, already giving his two very nice carved German basses to one of the sons who plays.

Recently Gary (the percussionist) was rummaging around in a storage closet at his dad's home when lo and behold a rather large and heavy rectangular object under some sort of vinyl cover appears in a corner.

So he lifts it out into the living room, having a good clue this was some sort of amp, takes off the cover, et voila: his dad's old bass amp, a mid 60s Supro Thunderbolt! He pinged me and I found the following info:

An open backed cab with 2 6L6GCs for the power section generating a whopping 35 watts into a Jensen 15". Not a good bass amp, let alone great one, but as far as blues guitar tone, one of the best, much like the old Fender Bassman amps. Another amp originally designed for bass but didn't pass muster there. Then lovingly adopted by guitarists over the world. But not as common or well known unless you're really into the blues world, apparently.

So he's going to one of the local amp shops and see what needs to be done to make it operable again. That means a properly grounded 3 conductor power cord (it still has the original 60s 2 conductor shocker cord) and recaps. Unknown at the moment what's in the tube complement, so we'll see what turns up as I've not seen this yet personally.

Here's some cell phone pics, pardon the resolution but it'll give you a good idea. I'll be taking better shots and posting them later on this thread. Anyone with more information or stories about this amp, or the other Supro bass amp (they had a closed back 70 watt model) would be appreciated:

[dhsierra1]

more photos:

[dhsierra1]

and one more:

[dlb1001]

This might help:
http://uniqueguitar.blogspot.com/201...underbolt.html

[dhsierra1]

Originally Posted by dlb1001

This might help:
http://uniqueguitar.blogspot.com/201...underbolt.html

excellent, thank you

[mjac28]

Looks to be in great shape cosmetically.

[azwhofan]

Incredible find!

I'll bet Bruce Zinky up in Flagstaff AZ would love to take a peek at it. He's owned the Supro name for a few years now and puts out a great line of repro and not-so-repro amps

[LAG]

I owned one these back in 1973-1975. I used it for bass guitar stacked on top of a Fender 2x12 sealed cab. Not much juice but oh the tone was marvelous. I wish i still had it.

[ntenny]

That's great. Does it have a tube rectifier or solid state? I think they made both versions at different times.

I have a near-equivalent Harmony amp---basically it's the same circuit with the addition of separate bass and treble controls, with the solid-state rectifier, driving the same Jensen speaker in a vertical open-back cabinet. (There was a Gretsch version too, and probably others.) It's been a very useful all-purpose amp for me; at 35 watts it's not a serious bass amp, but for recording and low-volume jamming I actually find its extremely-vintage lo-fi sound has some uses. As a guitar or lap steel amp it's positively good, especially used clean as a "pedal platform" amp; I believe the harmonica folks are pretty fond of them as well. IIRC the preamp uses one and a half 12AX7s, with one triode left idle, and some people have modified the design to use that triode for an extra gain stage, for instance. (Is it possible to do a tube reverb with one triode, I wonder?)

The Thunderbolt is definitely a well-known amp in blues/classic-rock guitar circles, because it's one of the plausible candidates for the amp Jimmy Page used for most of the first Led Zeppelin album. (*I* can't get my Harmony to sound like that, but there might be some reasons for that other than characteristics of the amp, I suppose.)

-NT

[dhsierra1]

I'll convey your comments to the proud adoptive father, thanks folks

AFAIK it has the solid state rectifier. Yes, it's still in cosmetically good shape, used for sure as there's a few dings and tears.

RE JP playing through one, yes, read that he did indeed use one on the first album. Why one can't get his tone is because he's Jimmy Page and really knows how to get some amazing sounds in the studio. Remember, the lead to Stairway To Heaven was played on a Telecaster

Gary (the owner) is supposed to take this thing in to an amp technician to give it the once over sometime this week. When it comes back I'll try to post some more pics. He's still walking on air now that he knows what he has

[will33]

Sweet amp Dierra, I love old stuff like that that's out of the norm Fender/Marshall stuff.

[dhsierra1]

yeah, you don't see Supro's everyday, esp in the bass world, they're not all that common for guitarists, either. Or at least I don't see them come up as much as you'd think.

If they had closed the back on this amp it probably would have been a lot better, 35 watts of tube can be very usable, witness the old Ampeg B-15s, I think those had about the same power back in the 60s.

The knowledge was available then that closed back works better than open for bass, so not sure what the deal was

[dhsierra1]

Originally Posted by ntenny

IIRC the preamp uses one and a half 12AX7s, with one triode left idle, and some people have modified the design to use that triode for an extra gain stage, for instance. (Is it possible to do a tube reverb with one triode, I wonder?)

really good question, I was looking at designing a hybrid tube/op-amp compact reverb circuit and the way I was going to use the triode was simply in the reverb spring return to reamplify the signal.

Never really followed up on it because I then discovered the Boss Fender Reverb pedal and said "why bother?"