Carbon comp resistors
- Thread starter riggler
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babyhead
Well-known member
I'll vote for CC on the cathodes, and MF on the rest, unless you want to be crazy and put tants in for the anodes. WW for the big PSU resistors. imho.
riggler
Well-known member
Yes Batuu that is correct! I got the schematic from emrr.
I know the original was all carbon comp, but I'm wondering if I can get a lower noise floor. Well, maybe it wouldn't be a big difference. Which is why I had the experiment option up there!
The only "power resistor" shown on this schematic is 1R7. Will be rolling my own PSU most likely. Going to tube rectify I think, should be sweet...
I know the original was all carbon comp, but I'm wondering if I can get a lower noise floor. Well, maybe it wouldn't be a big difference. Which is why I had the experiment option up there!
The only "power resistor" shown on this schematic is 1R7. Will be rolling my own PSU most likely. Going to tube rectify I think, should be sweet...
gridcurrent
Well-known member
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- Aug 28, 2009
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riggler said:
Before jumping onto those film resistors, you had better check the voltage rating. Even though metal films would function fine in the cathode circuit, I'm confident that new carbon comps would measure only slightly worse, if at all.
In the cathodes they don't make too much sense. I guess you want to use them for their sound and not for authenticity's sake. So you want to put them in the places where you have big signal voltage drops across them, which would be mainly the anode. Or the cathode for the follower.
But be aware of several things: you will have to buy some more resistors, because they really measure all over the place. They are extremely sensitive to temperature. Soldering too long will throw their value off or even damage them. And over the years of use their values will drift further around. Might attribute to a distinctive sound for one unit, but this is also the reason why no vintage amp sounds the same as the next one. You are probably well aware of the distortion and noise characteristics, so in the end you will have to try and see if it's what you expected and if the shortcomings are ok to live with.
Despite the fact that for example a Mallory might sound a little bit different than a Wima cap in some cases (and in some not), I still like to think that it's the circuit that determines the sound. With all those nonideal components, and actually most are to some degree, I change the circuit and not the type of component I use, to achieve something specific. But maybe that's just me. Have fun!
But be aware of several things: you will have to buy some more resistors, because they really measure all over the place. They are extremely sensitive to temperature. Soldering too long will throw their value off or even damage them. And over the years of use their values will drift further around. Might attribute to a distinctive sound for one unit, but this is also the reason why no vintage amp sounds the same as the next one. You are probably well aware of the distortion and noise characteristics, so in the end you will have to try and see if it's what you expected and if the shortcomings are ok to live with.
Despite the fact that for example a Mallory might sound a little bit different than a Wima cap in some cases (and in some not), I still like to think that it's the circuit that determines the sound. With all those nonideal components, and actually most are to some degree, I change the circuit and not the type of component I use, to achieve something specific. But maybe that's just me. Have fun!
Ther is something of interest here.riggler said:
1R1 and 1R7 are spec'd at 1W, although they have to dissipate much less than the anode resistors of the same tubes.
And 1R4 and 1R11 are not spec'd other than standard.
I think the designers found out that 1W res were less noisy than standard 1/2W.
It matters in the 1st and 3rd tube because their noise is fully amplified, in the 2nd and 4th tube they are within a NFB loop so noise is eliminated.
riggler
Well-known member
Hey Abbey thanks for that insight. Seriously I will be considering that when I build this thing.
If you're looking for noise floor reduction, maybe consider using wirewounds throughout.
They're traditionally recommended in a lot of the older literature from that era. They may work well as an in-between between metal films and CCs for both noise and whatever may be perceived on the sound end.
If you're building it fully P to P keep in mind the 1W CCs will be somewhat of a bull in a china shop on the petite 9-pin socket lugs - still doable - compared to 1-3W MFs or MOs.
I guess for overall knowledge's sake my vote would be (if practical) to do one with CCs on everything then do another with your other choice - MF or whatever on the entire build. It would put the question in the books.
You could experiment with breadboarding but it's hard to get a definitive answer on say noise since you have all those often longer than proper build wires all over the place and perhaps a less than optimum layout. Very easy to get buzz in that setting.
Its also difficult to get a meaningful answer on the sound question too in breadboardland as it takes using the amp in a real world setting over a period of time to fully discern the differences.
They're traditionally recommended in a lot of the older literature from that era. They may work well as an in-between between metal films and CCs for both noise and whatever may be perceived on the sound end.
If you're building it fully P to P keep in mind the 1W CCs will be somewhat of a bull in a china shop on the petite 9-pin socket lugs - still doable - compared to 1-3W MFs or MOs.
I guess for overall knowledge's sake my vote would be (if practical) to do one with CCs on everything then do another with your other choice - MF or whatever on the entire build. It would put the question in the books.
You could experiment with breadboarding but it's hard to get a definitive answer on say noise since you have all those often longer than proper build wires all over the place and perhaps a less than optimum layout. Very easy to get buzz in that setting.
Its also difficult to get a meaningful answer on the sound question too in breadboardland as it takes using the amp in a real world setting over a period of time to fully discern the differences.
