OD volume level in Non HRM SOLVED!

[dogears]

I have had 2 real HRM Dumbles here for my perusal. In both cases, the clean master does indeed hang as a load when in OD mode. The wiper is broken on it, not the input or ground.

This means any bright cap acts as treble bleed when in OD mode.

[bluesfendermanblues]

I'm pouring over the schematics I have on hand and from what I can tell, the correct way for an HRM amp to be wired is to have the Clean Master before the Clean/OD relay.
So that when it switches to OD, the Clean Master volume pot is taken completely out of circuit.
So that the two clean stages feed directly into the OD stages.
Then the OD volume or OD Master Volume controls the volume.
It is still dependent on the Pre-Gain volume for overall volume but this way the Clean Master and OD Master are independent of each other.

I notice quite a few of the HRM schematics I have do not show this correctly.

Claus this may be an alternative to your problem and would only require rewiring where the Master Volume resides in the circuit.

The schematic I attached shows this the clearest of the many I have.

Tom, thanks a bunch for the schemo, still the Clean master will affect the loading of the OD input.

[bluesfendermanblues]

Tom,

Doesn't that circuit still leave the 1 Meg clean master hanging on the OD input?

The only way I can think to wire the relay, so that it doesn't, would leave off the the ability to ground the OD input - like this.

[IMG:500:500]http://i275.photobucket.com/albums/jj30 ... lean-1.jpg[/img]

Otherwise, regarding all the talk of impedance etc. I don't think there is any one 'right' set of resistor or pot values. Changing them slightly imparts different a tone and response that can be used in best match to the one's guitar or and the pickups etc.

I'm also using 250K (rather than 100k) on the Drive or Level pot, but I've opted to use different input and output resistors as well.

That schemo should solve the problem, only you have to be real carefull with the wiring bacause the OD input is not grounded, it might produce ghost notes when in clean mode. Think I'll settle for the 250k pot solution.

[LPSGME]

That schemo should solve the problem, only you have to be real carefull with the wiring bacause the OD input is not grounded, it might produce ghost notes when in clean mode. Think I'll settle for the 250k pot solution.

What about piggy-backing a small single pole relay to the OD relay to add the ground? Radio Shack has one that I use to lower the 150K slope to 100 when in OD mode.

I'm still unclear which pot you are changing to 250.

After experimenting a lot, I think I'm going to add a center off toggle or two to change the mix of resistor values in the OD circuit.

[bluesfendermanblues]

I'm still unclear which pot you are changing to 250.

The OD master, which is labeled 'Volume' or 'Ratio'...

[bluesfendermanblues]

Swapped the 100KB OD volume for a 250KB and bridged the fixed 150k resistor fom V2b to the pot.

As a result I do no have to max the pot. I can leave it at 12 o'clock even with the input volume at 7-8.

Thanks for the tip guys!!

[Structo]

I have had 2 real HRM Dumbles here for my perusal. In both cases, the clean master does indeed hang as a load when in OD mode. The wiper is broken on it, not the input or ground.

This means any bright cap acts as treble bleed when in OD mode.

So then this schematic is correct despite the lack of a bright cap?