bogner red channel

[ryu]

Hi, I'm quite unsatisfied with the red channel, I'd like to turn a superlead to red channel specs to tweak it to taste
I'll then apply my tweaks to the original amp


here are some pictures of my amp












here's what i see (please point any error)

v1b
100k plate
820.68 (what is this white cap brand/type?)
.0047
500k gain pot
499k/470pf
499k to gnd

v2a
100k/1000pf plate
4.7k//4.7k (2,3k) 2.2uf tantalum
.0022
499k>499k//470pf
499k to gnd

v2b
100k/470pf
10k
.022
something lol

v3
1k

I think there's a 470k between v2b's .022 and V3 input but I don't know if it goes to ground or to v3's input
well i'm not sure of what happens there, please tell me

.1 PI coupling caps
i have yet to figure out wich presence pot value and presence pot cap

thank you

[joey]

First of all:, these bogners are all over the goddamned place regarding part types, and judging by your photos your model looks newer (the carbon filme plate resistors, tantalum c12, and red FKP-3's), but by the component values you listed sounds like an older model, late 90's. Did you read the values off of the pots, or measured.

second: What do you want to change, or what are you looking to improve from it.

[ryu]

Hi,
this is a 2007 model
my main concern is that this channel is really lacking high mids and has too much compression and way too much bass
I already removed the factory mod over the 10k on v2b (r12) a 2.7k and .22uf


but that drops the gain too much and I have to use the gain boost which in the end to me sounds even more compressed that the mod
eventually I'll try a 4k7 here

my first ideas where to lower the first stage .0047 to .0022 and to lower the 1000pf bypass on the 100k plate to 100pf
this way there would be no highs roll off but it would still prevents from oscilation
and if there's still too much bass also lower the .022 on v2b to .0047

regarding values I just looked at what's on the board
that's why I really don't get what happens between that .022 and the input of the last stage

I don't know if it's curable but the gain pot past 1 o'clock mostly adds bass not gain

thank you

[nico21]

Did you try the cameron mod?
over R12, put a 10k in series with a 1u cap

After that, Mark Cameron probably done other things, but this trick is the one that floating everywhere on the web

[ryu]

Hi,
yes I already tried the cameron's and brent's mod but didn't like it that much
of all the mods, brent's (10k .68 in paralell with the 10k) was the closest to what I'm looking for
but a bit thin sounding and still too much bass and compression
thank you

[nico21]

OK....
what are the preamp voltage filters caps? if they are 16u you could rise them to 32u or 47u

for the bass, yu have too much only on red channel or also with blue channel? you can first try lowering the 4,7n cap...

[ryu]

too much bass in the red, on the blue a bit less wouldn't hurt
that's why I thought begining with v1's .0047 to .0022 as it's common to both
might also lower the v2b's .022 to .0047
that might be the key

regarding the 470pf I wasn't that sure as the highs in the red channel are a bit ear bleeding
i usually set them between 11 and noon
what value would you suggest trying there? 220pf? 100pf?

I have to look back to see preamp's filters cap value but I don't have the amp at hand right now it's at my rehearsal's room

[nico21]

well for the snubber plate of the cold stage i would not go lower than 470pf
maybe try to lower the one of the second stage (the 1000pf one), but will also affect blue channel, and increase the 470pf one

i think (but not sure) the classic version has no 1000pf at the second stage and 470pf at cold stage

Also for exemple the brown channel of the bogner fish has no plate snubber at second stage and has a 1n snubber at the plate of the cold stage

all that to say find two on off on switches to try different configurations of snubber plate

[ryu]

thank you I'll try that


as I said before I don't want to mess that much with the original amp until I'm sure
so I will turn my metal panel into red channel's specs for testing purpose
I made two quick and dirty hand drawn schematic
the only thing I'm not sure about is what happens after v2b's .022 and the input of v3
please can you tell me which one looks correct?






thank you

[nico21]

after the 22n, you should have a 4,7M resistor to ground , then a 499k/499k voltage divider before the stage with the 1k cathode resistor

[joey]

replace the 2.2uf tantalum with a .68uf
lower both plate snubbers to 220pf

see where that gets you tonally, then we will work on the gain

[ryu]

is it correct this time ?



hi joey, thanks for your advice, I'll try that and report back
do you know at which frequency the roll off starts with 220pf?

thank you

[nico21]

after the 4,7M, put A 499k to input grid of next stage, also from input grid a 499k to ground

[ryu]

I hope the fourth is the correct one

[nico21]

YES!!!