Depth Control - Different Capacitor / Different Range & Feel

  • Thread starter Thread starter RealAmpsAreDead
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There is so much you can do with the NFB and depth circuit. This video is just touching the surface. Also, different cap types will sound different. So just when you think you found something you like, change out the cap type. I will say, depth circuits tend to like ceramic caps for Jose type designs.

What amp is in the video? I ask because it is the sum of the total circuit, not just one section.
 
psychodave said:
There is so much you can do with the NFB and depth circuit. This video is just touching the surface. Also, different cap types will sound different. So just when you think you found something you like, change out the cap type. I will say, depth circuits tend to like ceramic caps for Jose type designs.

What amp is in the video? I ask because it is the sum of the total circuit, not just one section.
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Thanks for the info! It is Evolve DIY Cali 50w.
 
psychodave said:
So it is a Jose design.... what are you looking for in the depth circuit? Versatility? A specific sound spectrum?
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I am actuall quite happy with the one I got. But let me know what to try next! Always curious in new things. Different capacitor types sound interesting to try actually. What is your favorite depth / nfb circuit then for a Jose style amp?
 
RealAmpsAreDead said:
I am actuall quite happy with the one I got. But let me know what to try next! Always curious in new things. Different capacitor types sound interesting to try actually. What is your favorite depth / nfb circuit then for a Jose style amp?
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For Jose style amps I like 100k NFB, .0033uf ceramic depth cap with a 39k resistor in parallel.

For options, this is hard to beat: switchable NFB 82k, 100k and 120k values. Depth caps: 500pf across the pot, then switchable between .002 to .0047 (so off is the 500pf cap, then the switch adds in the .002 or .0047). You can actually add an additional 1 meg pot with a .002 or .0047 across it (or throw it on a switch) to be able to vary. I also like to add a 39k resistor (or any value around it) across the depth cap on a switch to focus in on mids when I want it).
 
psychodave said:
For Jose style amps I like 100k NFB, .0033uf ceramic depth cap with a 39k resistor in parallel.

For options, this is hard to beat: switchable NFB 82k, 100k and 120k values. Depth caps: 500pf across the pot, then switchable between .002 to .0047 (so off is the 500pf cap, then the switch adds in the .002 or .0047). You can actually add an additional 1 meg pot with a .002 or .0047 across it (or throw it on a switch) to be able to vary. I also like to add a 39k resistor (or any value around it) across the depth cap on a switch to focus in on mids when I want it).
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Thx a lot! And what OT tap do you use? 4, 8 or 16 ohm?

And that 39k resistor on a switch across the depth cap in addition to a 1M pot?
 
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RealAmpsAreDead said:
Thx a lot! And what OT tap do you use? 4, 8 or 16 ohm?

And that 39k resistor on a switch across the depth cap in addition to a 1M pot?
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I like 8 ohm tap. It's a good middle ground. I find 16 to be too stiff and 4 to be too loose and grainy.

Yes, add the 39k to the depth cap on a switch. It will focus in on a certain frequency. You might like something different, so experiment.
 
People really don't realize how powerful NFB is. A lot of "gurus" that charge big bucks for their famous mods... al they're doing is swapping out a couple resistors and caps for simple tweaks like shown here. Change the NFB resistor, depth cap, slope resistor, and bright cap and voila... new amp.

Keep making these videos. Nice job.

Could try slope resistor next
Different cathode arrangements on V1a, V1b, and V2a (2k7/.68, 3k/1uF, 820R/.68, etc.)
Coupling cap values and order: 0.022uF vs 0.0022uF and in which location
PI cap and grid leak values

list goes on and on
 
FourT6and2 said:
People really don't realize how powerful NFB is. A lot of "gurus" that charge big bucks for their famous mods... al they're doing is swapping out a couple resistors and caps for simple tweaks like shown here. Change the NFB resistor, depth cap, slope resistor, and bright cap and voila... new amp.

Keep making these videos. Nice job.

Could try slope resistor next
Different cathode arrangements on V1a, V1b, and V2a (2k7/.68, 3k/1uF, 820R/.68, etc.)
Coupling cap values and order: 0.022uF vs 0.0022uF and in which location
PI cap and grid leak values

list goes on and on
Click to expand...
Kinda like "my stock Marshall is a bit bright and grainy." Let do this, lets do that, etc. and they change the entire feel of the amp. Meanwhile, you could just add a 250pf or 220pf cap across the NFB resistor and boom that crazy high end shrill is gone...all without doing a ton of mods. Get tired of it, simply remove the cap. Done, back to stock. All for the cost of 25 cents.
 
psychodave said:
For Jose style amps I like 100k NFB, .0033uf ceramic depth cap with a 39k resistor in parallel.

For options, this is hard to beat: switchable NFB 82k, 100k and 120k values. Depth caps: 500pf across the pot, then switchable between .002 to .0047 (so off is the 500pf cap, then the switch adds in the .002 or .0047). You can actually add an additional 1 meg pot with a .002 or .0047 across it (or throw it on a switch) to be able to vary. I also like to add a 39k resistor (or any value around it) across the depth cap on a switch to focus in on mids when I want it).
Click to expand...
If you’re referring to the Cameron style depth I’m pretty sure that resistor is in series with the depth cap, not in parallel. Unless you’re changing the value/ taper of the pot intentionally by going in parallel.
 
Just to add to this - I think NFB is an untapped resource for new and creative sounds. I’ve mentioned Naylors before, the NFB setup is so genius and makes an amp with .0022uF coupling caps in both of the first two stages sound massive. Very little bass in preamp, all the lows in the NFB section. But much bigger than your standard depth pot will provide.

I’ve started to deep dive into the NFB section myself a bit. But plan to get a lot more experimental. You just have to try and think outside the box and come up with new ideas. It is very powerful, no doubt.
 
RedPlated said:
Just to add to this - I think NFB is an untapped resource for new and creative sounds. I’ve mentioned Naylors before, the NFB setup is so genius and makes an amp with .0022uF coupling caps in both of the first two stages sound massive. Very little bass in preamp, all the lows in the NFB section. But much bigger than your standard depth pot will provide.

I’ve started to deep dive into the NFB section myself a bit. But plan to get a lot more experimental. You just have to try and think outside the box and come up with new ideas. It is very powerful, no doubt.
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How about no NFB?
 
psychodave said:
How about no NFB?
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Definitely a place for that, too. Rectifier red channel has no NFB. I use a large pot for my NFB control in my amps. You’re essentially removing the NFB when you turn it up all the way. Cuts hard but must be tamed in other ways or else it gets really biting.
 
psychodave said:
How about no NFB?
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I think Folkesson does that. But never found a schematic and in my modded amp by him you can‘t see what he has done - all covered in a black substance. Amp sounds killer!
 
psychodave said:
There is so much you can do with the NFB and depth circuit. This video is just touching the surface. Also, different cap types will sound different. So just when you think you found something you like, change out the cap type. I will say, depth circuits tend to like ceramic caps for Jose type designs.

What amp is in the video? I ask because it is the sum of the total circuit, not just one section.
Click to expand...
What I do to SLO-100 to tighten up? Probably a pedal to the front is the answer, but I am curious about other ways.

Mine doesnt’t have a Depth mod, I was curious of should I ever consider adding one, as I heard them say Depth knob below noon reduces excess bass, like noon is neutral/non-mod point and you start from there.
 
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RealAmpsAreDead said:
I think Folkesson does that. But never found a schematic and in my modded amp by him you can‘t see what he has done - all covered in a black substance. Amp sounds killer!
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Folkesson? What amp is that?

Also I involuntarily get hostile when I hear black substance on the board 😂
 
RedPlated said:
Definitely a place for that, too. Rectifier red channel has no NFB. I use a large pot for my NFB control in my amps. You’re essentially removing the NFB when you turn it up all the way. Cuts hard but must be tamed in other ways or else it gets really biting.
Click to expand...
Have you tried inductors in the depth circuit? You can get that Uber bottom end. I can make my JCA 20 watt throw more bottom end than a full size recto.
 
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