HRM with big muff tone stack possible?

[JD0x0]

Would it be possible to build a HRM but instead of the standard tone stack use a big muff tonestack with a single tone control?

I've been experimenting with tone stack calculator and it seems like a cool idea for a more non-HRM tonal quality but tuneable on a pot.

[max_lwedge]

It should be feasible to use a BMP in place of the HRM tone stack. IMHO, the Marshall stack in a D style provides a) a treble bleed, b) limits component tweaking often needed with non-HRM and c) has a sound we all know. HRM adjustment is far from obvious though. The Duncan tone stack calculator shows that with mid control dimed, the treble control can only boost, not cut. Most players I know will walk up to a amp with a TMB tone control, be it Fender Marshall or D Skyliner, and just turn the knobs to the “right” setting without playing it. Might be why the HRM TMB is an internal adjustment.

With the BMP, treble cut and boost is always adjustable with one knob, and can be mounted externally without concern of player getting off in the weeds. The down side of the BMP is that once you have picked the R1/C2 high cut and C1/R2 low cut sides of the BMP, the raw ingredients are fixed and you can only choose the blend. You are stuck with whatever the mid cut or boost was, based on where the 2 knees are. If the treble is turned down, the bass goes up, and vice versa. That being said, if the knees are picked for a particular player’s taste, the result may be just fine. But, you are back to tweaking with the soldering iron instead of tweaking HRM trimmers.

If the schematics can be believed, the famed Supro Thunderbolt had a BMP style control. R1/C2 were 150k/10n and C1/R2 were 3n/110k. The sweep looks a lot different on the Duncan TSC than the Big Muff. They both would be worth trying. Big Muff has low impedance, to me HRM was already pushing it.

I’ve been experimenting with a Dr Z style HRM replacement, but with different values, the original has a lot of mid scoop. I’m liking it so far, but it’s another solder, listen and tweak affair. I do like having the adjustment on the back of the amp, especially for my shrill Strat.

[JD0x0]

Thanks for the info. The reason why i ask is i like ALOT of lower mids which can be attainable with the muff stack. The HRM midcap on my current build is .008uF as opposed to .022uF(marshall-HRM) or .015uF(skyliner) im also adding a switch that will bring it all the way down to .004uF while also bringing the bass cap down from .020uF to .008uf to compensate and keep it from getting muddy.

[gazza]

you could try a simple fender 5e3 tweed deluxe style tone control around the od master pot, the insertion loss is very low.