Taking the leap into DIY with GT Supre and want to upgrade the components

[djrobyowallet]

Hi Everyone,

I have some very minor knowledge of electronics and have decided to upgrade and mod a GT Supre that i recently purchased. I have seen on forums that replacing the resistors with PR9372 resistors can help the sound, as well as 5N wiring, upgrading the caps to Wima or better, Kimber hookup wire, tube upgrades, and even upgrading the electrolytic caps to Black Gate. This is a personal project for me and something that i want to take the time to get right. If anyone can help point me in the right direction, or even help me to understand areas where certain upgraded components are see more noticeable results, then please impart your wisdom! I also have a full schematic for the Supre.

Cheers!

 

[Khron]

Any (clear) idea about what you're hoping to achieve with these mods? Except spending money, i mean...

 

[gyraf]

Perhaps post a schematic and a pic of actual implementation, and we can help guessing what can be done?

I don't think we believe in replacing wiring around here, but knowing the brand, there may be room for improvement..

 

[scott2000]

post a schematic

Looks like it's in the Tech Docs

https://groupdiy.com/threads/groove-tubes.45261/

 

[djrobyowallet]

I plugged the unit up and ran a mix through it. It sounded a little "grainy" to me and i read a thread on gearspace where someone was able to reduce the "grainy" aspect by upgrading the resistors to non-magnetic ones, replacing capacitors and electrolytic capacitors, and upgrading the tubes. Overall i am looking for a smoother sound, if that makes sense.

 

[Khron]

And cue the confirmation bias... (Yes, i'm THAT cynical.)

"Better" tubes might get you a lower noise floor, but other than that...

 

[djrobyowallet]

Would changing the resistors have any effect on the sound? going from magnetic to non-magnetic?

 

[Khron]

Why or how would it? Are any resistors (that are in the signal path) THAT close to any transformers, or sources of magnetic interference?

 

[emrr]

If it’s built with a bunch of internal push on connectors like the Vipre, clean all that and listen. Maybe a necessary evil in a complex multi-pcb design. Otherwise wire is….wire. Unless you want to buy into silver wire, or vintage wire that was pulled more slowly and ‘healed’ longer.

It’s a transformer coupled device, so they will dominate the sound over all else.

There’s the study that says carbon comp resistors with a higher voltage differential will add more 2nd harmonic. Not much voltage drop, not much effect. If you go there use overrated wattage as the ancients did to lower noise. Like a 2W where a 1/4W would be fine.

A better plan might be leaving this alone, keeping it for reference, and build a test bed in which you can experiment with various preamp circuits and swap component types in and out until you beat the Supre….then you can sell it!

 

[abbey road d enfer]

Would changing the resistors have any effect on the sound? going from magnetic to non-magnetic?

Snake oil.

 

[abbey road d enfer]

There’s the study that says carbon comp resistors with a higher voltage differential will add more 2nd harmonic.

It's not the first time I see this assertion, but I never saw this supposed study.
OTOH, there is a number of papers that document Resistor Voltage Coefficient, which is a well-known and validated effect, producing essentially 3rd-order distortion.
Now, when said resistor is in the plate or collector citcuit of a class A stage, resistance variations are different between positive and negative (actually less-positive) swing, so it creates a dissymmetry that probably results in 2nd-order distortion.
Actually, most resistors exhibit resistance variation vs. voltage; since it's related, amongst other things, to the electrical field, short resistors tend to exacerbate the effect. It's a well-known issue with the smallest SMT resistors.

 

[djrobyowallet]

Thank you all for the insight and knowledge!!!! I think i am going to scrap this idea and just learn a bunch before tackling such projects as modifying gear.

 

[Khron]

It also helps to have an idea of WHAT you want to achieve, then ask yourself why, and THEN figure out the "how".