Tweaking My Low Plate Amp (007): Another Resistor Makeover

[ayan]

Just a couple of notes on caps, overall. In 007, I ended up wit 5uF cathode bypass caps throughout. The amp had 10uF in V1 before, and was little bass heavy, so I thought I'd go in with 5uF and see how I liked the sound. Maybe 5uF with a 6PS mid cap works well, maybe 25uF works well with a 715P cap. In my other amp, the 715P mid cap reduced the low end by a great amount, as I already mentioned in the 102 thread, so this would seem to make sense.

As far as the plastic caps and their orientation, by now we all know that the placement of the outer foil makes a difference. When I started paying attention to that, my observation was that for coupling caps, the outer foil placed towards the lower impedance end would result in a cleaner and more midrangey sound. I think everyone arrived at the same conclusion. My rule of thumb became: whatever comes out of the inner foil end will be cleaner and more sustainy. The next thing would be to analyze what each plastic cap is doing. In the case of the treble and coupling caps, the signal is passed passed on the next stage. Not so with the middle and bass caps, since those dump signal to ground via the middle and bass pots respectively. Furthermore, what side of each one of those caps sees the lower impedance to ground depends on the setting of those pots. Another cap that is unique is the global feedback one, because it works in a negative feedback loop. So whatever that cap dumps to ground will not be subtracted from the signal. So this whole topic is a bit of a can of worms.

One other important thing, one cannot just rely on the factory bands on the caps -- if and when there are any. The 007 pictures will show that one of the two OD caps, both of which are 220P, are labeled differently. The V2A cap has the factory band at the inner end, the V2B cap at the outer end. So if you look at the picture of an amp with banded caps, don't assume you can be sure where the outer foil is.

Lastly, different caps will behave differently when flipped. When we put a scope to a cap to determine where the outer foil is, the lower the value of the cap, the bigger the difference between the 60Hz signals picked up by the cap when it's forward and backwards. But, for a given cap value, the particular cap type will likely behave differently. In my experience, the 715Ps exhibit -- on a scope -- a bigger difference than 6PSs. So, this probably adds an additional nuance to the can of worms.

G.

[pompeiisneaks]

Just a couple of notes on caps, overall. In 007, I ended up wit 5uF cathode bypass caps throughout. The amp had 10uF in V1 before, and was little bass heavy, so I thought I'd go in with 5uF and see how I liked the sound. Maybe 5uF with a 6PS mid cap works well, maybe 25uF works well with a 715P cap. In my other amp, the 715P mid cap reduced the low end by a great amount, as I already mentioned in the 102 thread, so this would seem to make sense.

As far as the plastic caps and their orientation, by now we all know that the placement of the outer foil makes a difference. When I started paying attention to that, my observation was that for coupling caps, the outer foil placed towards the lower impedance end would result in a cleaner and more midrangey sound. I think everyone arrived at the same conclusion. My rule of thumb became: whatever comes out of the inner foil end will be cleaner and more sustainy. The next thing would be to analyze what each plastic cap is doing. In the case of the treble and coupling caps, the signal is passed passed on the next stage. Not so with the middle and bass caps, since those dump signal to ground via the middle and bass pots respectively. Furthermore, what side of each one of those caps sees the lower impedance to ground depends on the setting of those pots. Another cap that is unique is the global feedback one, because it works in a negative feedback loop. So whatever that cap dumps to ground will not be subtracted from the signal. So this whole topic is a bit of a can of worms.

One other important thing, one cannot just rely on the factory bands on the caps -- if and when there are any. The 007 pictures will show that one of the two OD caps, both of which are 220P, are labeled differently. The V2A cap has the factory band at the inner end, the V2B cap at the outer end. So if you look at the picture of an amp with banded caps, don't assume you can be sure where the outer foil is.

Lastly, different caps will behave differently when flipped. When we put a scope to a cap to determine where the outer foil is, the lower the value of the cap, the bigger the difference between the 60Hz signals picked up by the cap when it's forward and backwards. But, for a given cap value, the particular cap type will likely behave differently. In my experience, the 715Ps exhibit -- on a scope -- a bigger difference than 6PSs. So, this probably adds an additional nuance to the can of worms.

G.

Yeah, back in the day, maybe 50's to 60's manufacturers put the band to indicate the outer foil, but stopped, probably to save a few pennies.

I've tried the effort of finding outer foil and installed them in amps and can't say for sure if it helped or not, but it definitely does reject noise better, but is that noticeable by the human ear, to some probaly, to others... not so much . I think taking that extra time to do it is worth it if you're hand building them for customers, to go that extra mile. For myself I just stopped as I'm going deaf anyway (thanks artillery and stuff)

~Phil

[ayan]

Yeah, back in the day, maybe 50's to 60's manufacturers put the band to indicate the outer foil, but stopped, probably to save a few pennies.

I've tried the effort of finding outer foil and installed them in amps and can't say for sure if it helped or not, but it definitely does reject noise better, but is that noticeable by the human ear, to some probaly, to others... not so much . I think taking that extra time to do it is worth it if you're hand building them for customers, to go that extra mile. For myself I just stopped as I'm going deaf anyway (thanks artillery and stuff)

~Phil

Sorry to learn about your hearing, Phil. As it were, in my experience the cap orientation turned out to be a lot more about tweaking the tone than noise rejection.

[pompeiisneaks]

Yeah, back in the day, maybe 50's to 60's manufacturers put the band to indicate the outer foil, but stopped, probably to save a few pennies.

I've tried the effort of finding outer foil and installed them in amps and can't say for sure if it helped or not, but it definitely does reject noise better, but is that noticeable by the human ear, to some probaly, to others... not so much . I think taking that extra time to do it is worth it if you're hand building them for customers, to go that extra mile. For myself I just stopped as I'm going deaf anyway (thanks artillery and stuff)

~Phil

Sorry to learn about your hearing, Phil. As it were, in my experience the cap orientation turned out to be a lot more about tweaking the tone than noise rejection.

Yeah I did note your comments about that. Very curious. I definitely hadn't thought that outer foil placement could have an impact on tone, as much as noise.

~Phil

[talbany]

Just a couple of notes on caps, overall. In 007, I ended up wit 5uF cathode bypass caps throughout. The amp had 10uF in V1 before, and was little bass heavy, so I thought I'd go in with 5uF and see how I liked the sound. Maybe 5uF with a 6PS mid cap works well, maybe 25uF works well with a 715P cap. In my other amp, the 715P mid cap reduced the low end by a great amount, as I already mentioned in the 102 thread, so this would seem to make sense.

Gil
Yes I thought about this after we spoke last and it makes sense to me too. So since you have the 5uF's in your amp you may not want to go there if you like the sound now and the amp is smooth I would let it eat!

Tony

[ayan]

Just a couple of notes on caps, overall. In 007, I ended up wit 5uF cathode bypass caps throughout. The amp had 10uF in V1 before, and was little bass heavy, so I thought I'd go in with 5uF and see how I liked the sound. Maybe 5uF with a 6PS mid cap works well, maybe 25uF works well with a 715P cap. In my other amp, the 715P mid cap reduced the low end by a great amount, as I already mentioned in the 102 thread, so this would seem to make sense.

Gil
Yes I thought about this after we spoke last and it makes sense to me too. So since you have the 5uF's in your amp you may not want to go there if you like the sound now and the amp is smooth I would let it eat!

Tony

Yep, I'm not inclined to touch anything at this point for fear 007 might get pissed and decide to mess with me. I need to just play the amp for a while before considering attempting anything further. BTW, I haven't even rolled tubes yet. I suspect the amp is capable of sounding even better, and it already sounds great.

G.

[talbany]

Just a couple of notes on caps, overall. In 007, I ended up wit 5uF cathode bypass caps throughout. The amp had 10uF in V1 before, and was little bass heavy, so I thought I'd go in with 5uF and see how I liked the sound. Maybe 5uF with a 6PS mid cap works well, maybe 25uF works well with a 715P cap. In my other amp, the 715P mid cap reduced the low end by a great amount, as I already mentioned in the 102 thread, so this would seem to make sense.

Gil
Yes I thought about this after we spoke last and it makes sense to me too. So since you have the 5uF's in your amp you may not want to go there if you like the sound now and the amp is smooth I would let it eat!

Tony

Yep, I'm not inclined to touch anything at this point for fear 007 might get pissed and decide to mess with me. I need to just play the amp for a while before considering attempting anything further. BTW, I haven't even rolled tubes yet. I suspect the amp is capable of sounding even better, and it already sounds great.

G.

Yep let's not piss him off!. FWIW.If you decide to roll I have the best luck with ones in the OD slot are where both triodes are closely matched or within a few volts. I shoot for around 210 smooth as silk. Again FWIW

Have fun!
Tony

[ayan]

Yep let's not piss him off!. FWIW.If you decide to roll I have the best luck with ones in the OD slot are where both triodes are closely matched or within a few volts. I shoot for around 210 smooth as silk. Again FWIW

Have fun!
Tony

Coolness, thanks!

[norburybrook]

Gil
Yes I thought about this after we spoke last and it makes sense to me too. So since you have the 5uF's in your amp you may not want to go there if you like the sound now and the amp is smooth I would let it eat!

Tony

Yep, I'm not inclined to touch anything at this point for fear 007 might get pissed and decide to mess with me. I need to just play the amp for a while before considering attempting anything further. BTW, I haven't even rolled tubes yet. I suspect the amp is capable of sounding even better, and it already sounds great.

G.

Yep let's not piss him off!. FWIW.If you decide to roll I have the best luck with ones in the OD slot are where both triodes are closely matched or within a few volts. I shoot for around 210 smooth as silk. Again FWIW

Have fun!
Tony

Interesting, so a 'balanced' P.I. tube would be a good starting point then?

M

[talbany]

Yep, I'm not inclined to touch anything at this point for fear 007 might get pissed and decide to mess with me. I need to just play the amp for a while before considering attempting anything further. BTW, I haven't even rolled tubes yet. I suspect the amp is capable of sounding even better, and it already sounds great.

G.

Yep let's not piss him off!. FWIW.If you decide to roll I have the best luck with ones in the OD slot are where both triodes are closely matched or within a few volts. I shoot for around 210 smooth as silk. Again FWIW

Have fun!
Tony

Interesting, so a 'balanced' P.I. tube would be a good starting point then?

M

M
A Balanced PI tube is always a good place to be. I was referring to V2
T

[norburybrook]

Yep let's not piss him off!. FWIW.If you decide to roll I have the best luck with ones in the OD slot are where both triodes are closely matched or within a few volts. I shoot for around 210 smooth as silk. Again FWIW

Have fun!
Tony

Interesting, so a 'balanced' P.I. tube would be a good starting point then?

M

M
A Balanced PI tube is always a good place to be. I was referring to V2
T

yes, i know but I meant using a balanced PI tube in V2 as well


M