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High gain noise management
High gain noise management
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Old 9th April 2019, 07:03 AM   #11
dreamth is offline dreamth  Romania
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here you have the channel 3 sound(5 triodes):
YouTube
YouTube

here you have the channel 4(11 triodes)
YouTube
each channel has multiple mods and variations.
Unfortunately they put so many drive mods on an amp who had one of the best clean ever...Clean players aren't really dead about drive...so they discontinued it for the right reasons.
A small review that tells a lot to an electronics engineer:
"Channel 4: Grosse distortion, but not Hi-Gain so far. Good sound, quite versatile, especially thanks to the équalo. A good distortion lamp, but ultimately lacks personality"
as channel 4 lacks high gain usual hum...the hum is the one that makes the high gain "recognizable high gain", Carvin has no hum in high gain...just distortion and a lot of it!

Last edited by dreamth; 9th April 2019 at 07:16 AM.
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Old 9th April 2019, 09:01 AM   #12
thoglette is offline thoglette  Australia
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Quote:
Originally Posted by dreamth View Post
as channel 4 lacks high gain usual hum...the hum is the one that makes the high gain "recognizable high gain", Carvin has no hum in high gain...just distortion and a lot of it!
Agreed. IMD from power rail recharging/screen IMD seems to be a key component of the high gain power chord, even if they don't allow as much sag as earlier "mid gain" amps.

In the case of my "clean" chain I think I'll need each pair set closer to "clean" but with similar gain/attenuate so that all even stages clip at the same time, first into cut off (for lotsa 2nd) and then it's a race between the odd stages and grid cutoff.

I think. Maybe I want grid bias in the odd (warm) stages first

Last edited by thoglette; 9th April 2019 at 09:06 AM.
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Old 9th April 2019, 12:06 PM   #13
dreamth is offline dreamth  Romania
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Originally Posted by thoglette View Post

In the case of my "clean" chain I think I'll need each pair set closer to "clean" but with similar gain/attenuate so that all even stages clip at the same time
not really true...Look at how Mesa(dual rectifier) implemented the Soldano slo100 gain stage vs Hughes and Ketner(Triamp)
Mesa used the 2nd and 3rd gain triodes in one valve , Ketner used them in separate valves.
The difference is that H&K had a higher output because using those two stages in one valve, there was some kind of negative feedback, while H&K needed to add an external feedback at higher frequency to keep it clean, though the gain is definitely higher just by using those two stages in different valves.
I built both versions and that is how i found out...
Carvin preamp has a lot of low quality semiconductor on the signal path too...
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Old 9th April 2019, 01:31 PM   #14
thoglette is offline thoglette  Australia
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Originally Posted by dreamth View Post
not really true...Look at how Mesa(dual rectifier) implemented the Soldano slo100 gain stage vs Hughes and Ketner(Triamp).
Ah, more homework!
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Old 9th April 2019, 01:43 PM   #15
dreamth is offline dreamth  Romania
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You might like the H&K version as it is a bit more open while the Mesa is a bit darker...
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Old 9th April 2019, 09:32 PM   #16
PRR is offline PRR  United States
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Originally Posted by thoglette View Post
Fascinating. ..... I wonder if the bias shift (in your simulation) has an audible effect?
The bias shift is done before 10mS. At guitar time-scale and pluck transient, I suspect bias-shift has "no" audible effect.

I would not say the chips are low quality. They are low-spec by audiophile standards, true. However at guitar level and bandwidth, the '558 have been a mainstay of guitar electronics. They work. I might chose a different chip, not sure; but it isn't a bad choice.

Anyway if those tubes do anything they ought to overwhelm the chips.

Quote:
all even stages clip at the same time
My suspicion is that you want "layered" clipping, not all-at-once. However only the breadboard can tell for sure.
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Old 10th April 2019, 02:45 AM   #17
dreamth is offline dreamth  Romania
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the njm4558 is widely used and appreciated for its trashy sound in Polytone where some people try opa2134 for a cleaner sound...but here we have countless 4558 in series everywhere.It sounds like a "fine choice"...Now...for a drive circuit you don't want a trashy nonlinear stage before the drive circuit because you won't be able to trim the final products in the eq section.There are lots of fet switchers too and then.... should we wonder why people say that the drive section lacks dynamics?
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