Guild Quantum Ohm Load (Attn: Default!)

Hennebeau

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After a two week's search I still can't find a straight answer as to how many ohms my Quantum can handle. Hopefully someone on here finds a free minute to answer a few questions. My particular amp has two speaker jacks on the back. Does this mean that the amp can be run at 4 ohms, and each jack is an 8 ohm jack? Also, can I run a power amp out of the "pre" jack? If so, can the power amp be run in conjunction with the Guilds power amp? My Regards.
 

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Assuming it is the same as my 8417 Thunderbass, which shares much of the same circuits, both speaker outs are 8ohm independently. So you can run two separate 8ohm cabs, or just one 8ohm cab.
 

Hennebeau

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Assuming it is the same as my 8417 Thunderbass, which shares much of the same circuits, both speaker outs are 8ohm independently. So you can run two separate 8ohm cabs, or just one 8ohm cab.

Wonderful! Now I can put this thing to good use. My thanks. Curious, do you have the "pre" jack on your version? I'm wondering If I can attach a power amp to that.
 

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That is what the pre out is intended for, a slave unit. Correct on the 8 ohm, as Mr Squirrel Domicile said. :cool:
 

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Wonderful! Now I can put this thing to good use. My thanks. Curious, do you have the "pre" jack on your version? I'm wondering If I can attach a power amp to that.
No pre-out jack on mine, so I'll let Steve answer that part.
 

Hennebeau

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That is what the pre out is intended for, a slave unit. Correct on the 8 ohm, as Mr Squirrel Domicile said. :cool:

Wonderful news. Thanks to both of you for the knowledge. So, when hooking a power amp to it the chain would go something like this: Guild>4x12 (8 ohm)>Power Amp out of Pre>Into 4x12 (8 ohm)? Do I have that right?
 

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Pre is just a signal. It just goes into whatever amp/pa you are using and it has nothing to do with the Guild amp at all.
 
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Is it the same with all ThunderBass heads? Mine is the 4 tube preamp with 8417 power section.

Rear panel has one speaker 1/4" jack and an Aux 1/4" jack.

Can I run two 8ohm cabs with this head?
 

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Is it the same with all ThunderBass heads? Mine is the 4 tube preamp with 8417 power section.

Rear panel has one speaker 1/4" jack and an Aux 1/4" jack.

Can I run two 8ohm cabs with this head?


Yup! You're good!
 
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Thanks Default! How many watts does this model put out with the 8417 power tubes?
 

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Depends on the voltage at the plates. The 1A puts out 50 watts@400 volts, the Quantum puts out 100 watts@530 volts. If it doesn't say Quantum, it's the fifty watter.
 
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Depends on the voltage at the plates. The 1A puts out 50 watts@400 volts, the Quantum puts out 100 watts@530 volts. If it doesn't say Quantum, it's the fifty watter.

Interesting. So in theory my 50watter can be made into the Quantum pretty easily then?
 

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Custom built transformer and all, plus circuit changing and long out of production tubes? I wouldn't say easy.
 
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Custom built transformer and all, plus circuit changing and long out of production tubes? I wouldn't say easy.

Well there goes that theory. :)

I'll be taking it in for a complete service soon. Should I have the tech switch it over to KT88 power tubes?
 

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It's going to need a new bias supply built because 8417s ran on -17 volts bias. It might need some beefing up on the heater supply, I don't remember exactly how much draw the 8417 had, but I think it was the same as a 6l6. At work now.
 
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It's going to need a new bias supply built because 8417s ran on -17 volts bias. It might need some beefing up on the heater supply, I don't remember exactly how much draw the 8417 had, but I think it was the same as a 6l6. At work now.

Would it be worth switching over to KT88 or leaving it 8417 for now?
 

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If it still plays and sounds good, I wouldn't bother just yet. The tubes are being run so far under spec's that they should still have a lot of life left.
 
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If it still plays and sounds good, I wouldn't bother just yet. The tubes are being run so far under spec's that they should still have a lot of life left.

Good to know. I will be taking it in for a full check up and to replace the two prong power cord to a three prong.
 
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