Thunderbass

megadan

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I just picked up an old thunderbass from ebay...
here's a few pics:

front.jpg


alltubes.jpg


firstpre.jpg


Any one have any info on this amp, schematics, dating info, nostalgic storys? :)
 

Mr.Tidy

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I have no info just wondering how it sounds.
I've used tube bass amps before for guitar becuase I like their loud clean sound. Have you played geeetar through it?
How's it sound for bass too?
 

megadan

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I don't know... it worked for a few seconds, sounded very warm and bassy.... then it blew up :(

needs new power tubes, 6550's
 

dklsplace

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Have you had it checked out to see if there's any other damage?
 

megadan

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I plan to take it to an amp tech, supposedly the best tube amp tech in Canada, actually, to have it checked out, as soon as I have the cash.
It needs a new 3 prong power cord to replace the 2 prong shock inducer, for one thing :!:
 

matsickma

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Hi megadan,

The amp you have is more than a Guild Thunderbass. It is a Quantum! This amp uses a pair of 6550 finals and is the most powerful amp Guild ever made. It had the power of a 100 W Marshall plexi without the "presence"control.

This looks like a Thunderbass only by the front name marker. Guild was always very thrifty on using common parts. However if you look inside this amp you will notice the amp is in two sections. You will also find a Quantum name plate on the power housing. The preamp control and power amp section are seperate. The size of the amp head is huge.

If a conventional Thunderbass amp was mounted on top of your amp it would look quite small. The Quantum is 23" W x 9 1/2"H x 15" D. A Thunderbass is 21 1/2 W x 8"H x 11 3/8"D.

Earlier Quantums were packaged in a Thunderbass cab and housing. These tended to overheat. The larger model was the last version.

I just blew one of the 6550 finals running my Quantum through a Power Soak. Hope I didn't damage anything else. I just ordered a new set.

matsickma
 

megadan

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Wow, matsickma. Thanks for the info!
In a few months I should have the cash to get this thing repair (I know, I know; I'm a poor student). I can't wait to get in cranking :D
 

megadan

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So
I just got this amp back from my tech, finally...

let me tell you, at first I was skeptical about this being a Quantum model, as was my tech: he has never seen one of these before, but his guess was that it would "not be very loud"
Well let me tell you he was wrong! This thing is amazingly loud... I would say it has almost as much volume and presence as my modern SWR350 amp... wow...

It sounds very modern, clean, warm without being muddy, and a massive amount of treble is avaliable, just as described in other posts. I haven't cranked it to 10 yet, but it got wall rattlingly loud, without overdriving! :eek:

The only downside to this amp is that the caps are leaking, creating a lot of buzz and hum that can't be removed (even hums on standby). Unfortunatly to replace the caps, and essentially rebuild the entire amp, would cost much more than I paid for it, and much more than I have.

But it does indeed sound amazing!
 

megadan

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So
I just got this amp back from my tech, finally...

let me tell you, at first I was skeptical about this being a Quantum model, as was my tech: he has never seen one of these before, but his guess was that it would "not be very loud"
Well let me tell you he was wrong! This thing is amazingly loud... I would say it has almost as much volume and presence as my modern SWR350 amp... wow...

It sounds very modern, clean, warm without being muddy, and a massive amount of treble is avaliable, just as described in other posts. I haven't cranked it to 10 yet, but it got wall rattlingly loud, without overdriving! :eek:

The only downside to this amp is that the caps are leaking, creating a lot of buzz and hum that can't be removed (even hums on standby). Unfortunatly to replace the caps, and essentially rebuild the entire amp, would cost much more than I paid for it, and much more than I have.

But it does indeed sound amazing!
 
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Guild Quantum Thunderbass

I just got this Guild Quantum Thunderbass amp from a woman in Pennsylvania. She told me she bought it in '70 or '71 used it a short while and put it in storage. It is very clean and doesn't look abused like if a guy had it for over 30 years.I doubt it ever really got cranked up. What I would like to find out is how low of an ohm load it can handle-2,4 or 8. I got it with the Guild 2-15 cabinet loaded with JBL signature series D-140's,not even dusty. This amp sounds tremendous,especially with my old EB-3 bass. But if anyone has any technicle information I would greatly appreciate it. I was going to put some pictures on too but I'm not really savy on this computer stuff. I can e-mail some though if you want to see.
 

matsickma

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Hi tsd63,

It looks like you got the Mother Load of Guild Bass amps! The Quantum with a pair of JBL D140's was the top of the line back in 1969. The Bass player from Blood, Sweat and Tears used a Quantum with 2-dual JBL D-140 cabinets! His sound was killer.

What is the impedance of the speaker cabinet you have now? The Quantum has an additional Aux output that can be used to drive a second cabinet. It is not directely hooked up to the primary speaker output. It is a separate tap off of the output transformer.

The Quantum 2-15 JBL cabinet is huge. Can you post the dimensions? Where in PA did you pick up such a prize? Can you tell me the S/N of your amp? Did the amp come with the origional covers? I am interested in seeing your amp so feel free to send me any pictures you take. Check your PM for a message on my email address.

Great find!

matsickma
 

megadan

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Re: Guild Quantum Thunderbass

tsd63 said:
What I would like to find out is how low of an ohm load it can handle-2,4 or 8.

Hi,

my Quantum handles an 8 ohm load from each tap. I use 2 8 ohm cabs - one on each tap.

It's a pretty beefy amp, I would think that it could handle a 4 ohm load but I can't say for sure.

The cab that came with it is probably 8 ohms, but again, I can't say for sure!


Great find, though, have fun with it!
 
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Thunderbass Quantum

The only outputs on this amp are one speaker and one preamp.The preamp works fine running straight to a P.A. power amp.If I can find my ohm meter I'll post the cab ohms. As you can see from the photos this amp is different on the inside from any other pictures I've seen.And the amp has a bigger cabinet with ventilation screens.It looks like there was another badge under the Guild on the speakers. I believe I've seen this on old ads but cannot make out what it's supposed to say.Anyway I hope the pics turn out for you.[IMG:800:600]http://i134.photobucket.com/albums/q93/tsd63/IMG_0877.jpg[/img][IMG:800:600]http://i134.photobucket.com/albums/q93/tsd63/IMG_0869.jpg[/img][IMG:800:600]http://i134.photobucket.com/albums/q93/tsd63/IMG_0870.jpg[/img]














[IMG:800:600]http://i134.photobucket.com/albums/q93/tsd63/IMG_0872.jpg[/img][IMG:600:800]http://i134.photobucket.com/albums/q93/tsd63/IMG_0865.jpg[/img][IMG:800:600]http://i134.photobucket.com/albums/q93/tsd63/IMG_0812.jpg[/img]


















[IMG:600:800]http://i134.photobucket.com/albums/q93/tsd63/IMG_0874.jpg[/img][IMG:600:800]http://i134.photobucket.com/albums/q93/tsd63/IMG_0867.jpg[/img][IMG:600:800]http://i134.photobucket.com/albums/q93/tsd63/IMG_0875.jpg[/img]

















[IMG:800:600]http://i134.photobucket.com/albums/q93/tsd63/IMG_0876.jpg[/img]
 

matsickma

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Hi tsd63,

Great pictures! I always wondered what the inside of a Quantum cab looked like. The upper part of the cabinet looks similar in design to the 1-15 Thunderstar Bass cabinets -front loaded driver with a rear baffle. The bottom speaker section looks be loaded differently. Is that true? If so can you post some additional pictures? Can you post any dimensions?

My Quantum has two speaker outputs. The primary is on the rear right side of the power amp (8 ohms) and the other is an Ext Speaker (8 ohms) on the rear left side of the power amp. What is your configuration? Where is the preamp out?

That is unusual on an amp like this. Can you list what is written on the labels on the rear of the amp? The labels on the back of your amp is different than mine. My amp has one long strip going across the rear upper edge of the power amp section. Your amp has individual labels marking each rear function. It is possible that your amp had custom features or Guild changed the design. What is the SN of your amp? Your S/N may indicate if it was made before mine and megadan's. If you look at megadan's Quantum pictures you will see the difference in rear labels between your amp and ours.

I live near Allentown, PA. Where in PA did you come across this beauty?

matsickma
 

john_kidder

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Wonderful pictures.

Delicate little pair, aren't they? I nearly bought just such a rig a while ago, until I assessed shipping from Pennsylvania to British Columbia. I'm not sure I'd want to turn it up in the midst of that furniture - could be a lot of fractured glue joints in just a few seconds.
 

ThunderCat

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ya

That cabinet looks good! I'm trying to figure out what kind of cabinet my Thunderstar bass amp came with. It doesnt look like a Guild but it does have the round plates for the input jack. The cab works good for bass, not so good for guitar. I have to pry open the front to get a look at the speaker as the back of it is closed up. I may sell the cab to my bass player.
 
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Quantum Info

The 2-15 cabinet is 8 ohms. The labels on the back from left to right are Pre Amp Out - Guild Musical Instruments - Quantum Amplifier Ser.No. Q1049 110/125 Volts AC 60 C/S 285VA - Hum Balance - 4Amp 3AG Fuse - 4Amp Max Aux AC Outlet. No tag on the speaker outlet.The speakers are mounted towards the top and bottom of the cab with 2 baffles and a port in the middle. If you turned the cab upside down it would look the same.The head measures 9-1/2" high 23" wide and 15" deep and has vent screens on top & back.Somewhere on another page here someone described this as a later model head,Ill have to look that up again. The speaker cab measures 41-1/4" high 24" wide and 15" deep. I added the wheels and no I didn't get any covers. I got the amp on the east side of Pittsburg. The woman told me she had it up for sale several times but no takers. Also to megadan could you list what the labels on the back of your amp say, I can't quite make them out in the photos and all of mine are not marked.
 

matsickma

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Hi tsd63,

Great Info. Here is what we got. It looks like your Quantum was manufactured earlier than megadans and my amp. Your S/N is Q1049, mine is Q1163 and megadan's is Q1170. Megadans and my Quantum look identical as would be expected because of the close serial numbers. Yours is similar with the exception of the preamp amp out and the rear labels. Our amps also have two separate 8 Ohm speaker outputs and no Preamp output on the power amp section. It looks possible that the earlier 6550 Quantums has a single 8 Ohm speaker output and preamp output. The later model 6550 Quantums could drive 2-8 ohm cabinets.

The markings on the back of the later 6550 amps is left to right from behind the amp: EXT. SPKR. 8 OHMS, BIAS TEST SEE SERVICE INST., DAMPING HIGH, LOW, HUM BALANCE, 4A SLOBLO, AUX OUTLET 4 AMPS MAX, SPEAKER 8 OHMS.

From your cabinet description is looks like a full size Quantum speaker cabinet has a pair of front loaded speakers with a rear baffle design similar to a pair of stacked 1-15 Thunderstar Bass cabinets.

matsickma
 
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