Blackheart HD 15 Mod Question

paintballer626

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I was wondering if anyone knows how to mod a HD 15 towards a higher gain JCM800?

I've already made a few mods to the amp, pushing it towards a more Marshall-esque quality. Thanks to Lyle Caldwell for the helpful suggestions :thumb:

Heres the link to the thread for Lyle's suggestions:
http://www.mylespaul.com/forums/squawk-box/163757-blackheart-handsome-devil-has-fizzy-overdrive.html

So these are the mods I have currently made to HD 15:
  1. I replaced R8 to 33K, which really brought out that "Marshall" tone with a bit more body.
  2. R9(1M) I changed down to 470K, a definite change with the gain, but I think a bit more gain can be squeezed from the devil.
  3. R22, and R23 both (100 ohm 2W) I replaced with 1K 2W resistors.
  4. I also replaced R4 (100K) with a 220K resistor.

So if anyone has a suggestion on how to squeeze more gain from the HD 15, without adding a pedal to the amps signal path.:hmm:
Any suggestions would be great:thumb:

I also decided to make a nice hardwood grille out of walnut and mahogany for the combo, since I've really been digging the look of custom hardwood amp cabinets:cool2:

417260_3963313959374_1301000908_n.jpg
 

wrc73

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You could add a tone stack bypass mod.
 

paintballer626

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wrc73- By doing a tone stack bypass wouldn't I just be cutting the ground wire to the tone stack? Sorry not a Amp Tech so my knowledge with mods isn't very strong. :confused:
 

paintballer626

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Will I lose complete function of the EQ potentiometers if I tone stack Bypass?
I understand that that the EQ potentiometers being passive drain some of the current, thats why a TS Bypass boosts the signal. Correct me if I'm wrong here?
Is there a way to get more gain without sacrificing the EQ potentiometers?
 

TWANG

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Yes, and no.
You can modify the tone stack cut out switch .. make it a simple circuit.
In my 18W build I used the tone stack cut out switch via a jack to a footswitch.

First you add a value of Resistor to set the low point of the gain increase.
That means you are looking, with your ears, at two things.
how much gain. .and how much of the tone stacks use is lost.

If the gain is not too much, then the tone controls will still have 'some' function.
How much depends on you.

So... the thing you will be trying to decide is..
where the point is at which the tone stack becomes 'too' ineffective.

In my case I made the switch so that when you hit it.. there was just a tick of increase in gain.. and it was more bright by another tick.
then I added a pot.. so the FS has switch, LED, knob..
that way I can vary the amount of gain.. the more gain I dial in, the more tone stack I dial out.

It's got to be brighter.. because the more gain you add the more you are leaning to the full range of the tube with no attenuation of frequencies, and with less and less 'balancing' of the ranges as the tone stack is made less useful.

However, buying parts online you wind up with about 20.00 for a really nice footswitch, and you can, at least, dial this all up to as close as possible.
It's not a wonder mod or something.. there are things that just are what they are in this idea.
But it's tweakable. and in the amp I used this in, very much liked.

You're stealing power back from the tone stack.. so you can understand that the more you take of power, the more you take from the use of the tone stack.

this mod would require adding a shorting jack to the amp control panel.
You could put a switch next to it for 'full tone stack cut'.
and you could run the jack to the pedal for adjustable gain increases.

I have some more mods, but I am too busy to go further now. I'll try to get back in.
Also I have a bh15 here so I would, given time, even tear it down and try somethings out for ya.

The mod I used for the tone stack/fs is based on Belovs footswitch with some of my own changes.

One thing you can do.. even if you don't read schematics.. is compare the schematics..
even a novice can see some things in the front end.. from input through the preamp tub es..of different values, etc.
So you can get an idea of why, without much trouble, of why amps vary in their tones and why you have to compromise, or just get close sometimes.
 

PSM

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I always open these threads saying to myself, :hmm: "This could be an interesting read...", then about three to four posts in, I just go, :shock: "Give me my damn guitar..." and crank up my amp instead.
 

TWANG

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It's not all that hard. Some things are very simple in fact.
Like the above footswitch. Anyone could build it.
 

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