Change Marshall DSL100H preamp HT voltages

[Rod]

Hello everyone!

Is it possible to change the Marshall DSL100 HT preamp voltages, HT1, HT2, HT3, HT5( I want to remove and bypass the V2B gain stage from the DSL100) to be similar like the same voltages in the Marshall JVM410? will this changes in the HT preamp voltages make the amp more articulated?

Attached to this email there is the schematics of the two amps.

Thanks.

[Rod]

Im asking this because for some reason im unable to make the DSL100 tigher and articulated, i allready tryed everything, i have lowered the value of the coupling caps values, i have lowered the values of cathode bypass caps, it seems that the amp has to much bass in the first gain stages

So it seems to me that maybe the problem must be in the HT's of the preamp.or something else

[J M Fahey]

No, leave voltages as-is.

Your somewhat lowering coupling and cathode caps is fine; now Iīll check about presence/absence of the cold cathode clipper, it is WAY more important than people think.

Typical noob/no_clue mod is to replace 10k cathode resistor with a lower value one, and even worse, bypass it with some kind of cap, then pat themselves in their own backs happy because of the (very muddy) extra gain.
WROOOOONNNNNGGGGG

EDIT:

• jvm410-60-02-iss2-1.pdf (173.2 KB, 0 views)

"Invalid file specified"

[Rod]

No, leave voltages as-is.

Your somewhat lowering coupling and cathode caps is fine; now Iīll check about presence/absence of the cold cathode clipper, it is WAY more important than people think.

Typical noob/no_clue mod is to replace 10k cathode resistor with a lower value one, and even worse, bypass it with some kind of cap, then pat themselves in their own backs happy because ofvthe extra gain.
WROOOOONNNNNGGGGG

Thanks again JM Fahey, i have lowered The R38 the resistor of the cold clipper on the DSL100 to 10K , do you think that this could be the problem?

[J M Fahey]

Thanks again JM Fahey, i have lowered The R38 the resistor of the cold clipper on the DSL100 to 10K , do you think that this could be the problem?

"THE" clipper in Marshall amps since Day 1 which gives them their classic buzzy punchy aggressive distortion is the combined gain stage + cathode follower driving the tone stack, inherited from Tweed Bassman which is a killer amp.

You need a cold clipper as the stage immediately before it.

As you see, itīs "too early" in the chain, since itīs before V2b, to boot itīs not *that* cold. (4k7 cathode)

I would either make R38 10k AND straight drive V3a, bypassing V2b as I suggested with my added switch, *OR* make R39 10k IF you use V2b .

Try both and you tell me

[Rod]

"THE" clipper in Marshall amps since Day 1 which gives them their classic buzzy punchy aggressive distortion is the combined gain stage + cathode follower driving the tone stack, inherited from Tweed Bassman which is a killer amp.

You need a cold clipper as the stage immediately before it.

As you see, itīs "too early" in the chain, since itīs before V2b, to boot itīs not *that* cold. (4k7 cathode)

I would either make R38 10k AND straight drive V3a, bypassing V2b as I suggested with my added switch, *OR* make R39 10k IF you use V2b .

Try both and you tell me

Hi Fahey, well there is something in the DSL100H mids that always make the amp sound harsh no matter the mods i make that i cannot get rid off, I think that maybe this could be of the quality of some components in the amp. Because this is the vietnam model, so maybe poor quality output and power transformer.

I cannot get from the amp the articulation, definiton that my JVM410 has, also there is something going strange in the mids. What is component that can have great effect on this, the output transformer?, or both power and output or is it better to sell the amp, because no matter what upgrades i made the amp will always sound like that?

[loudthud]

Are you sure the differences aren't just differences in the speakers ?

[Rod]

The speakers and cab is the same when i play both heads, a marshall cab with vintage speakers.

[thesvtguy]

I had the same problem with harshness at first, but I figured out if you add a gain control after v1b and leave always leave the stock gain control dimed it sounds far better. It was a very simple mod, I just soldered a wire to TP5, connected it to a resistor (anything from 2k to 10k will work fine) and then to a pot (I used an a100k) and then to ground.