HRM bypass

[mbeldyga]

Hi.

Have anyone ever try this? I have one free relay left so I thought it may be good idea. Some kind of boost for OD section. What do you think?

[Structo]

I think it is worth a try.

[ayan]

Hi.

Have anyone ever try this? I have one free relay left so I thought it may be good idea. Some kind of boost for OD section. What do you think?

This has been done before in one of the many TR models. I think the way it was implemented was something like:

1. Lifting the ground off the OD tone stack. Not sure if they lifted it entirely or if they had a tail resistor or resistor//cap which remained in the circuit.

2. With the other pole, you can hang a variable resistor (VR) in parallel with the 1 Meg overdrive master volume to knock down the signal level and bass some as you bypass the OD tone stack. If you dial in the VR to your taste, you get a footswitchable sound that doesn't have to be a boost unless YOU want it to be.

Cheers,

Gil

[mbeldyga]

Thanks ayan. It's very helpful. I think i'll give it a shot.
I found out that TR you talking about is OPAL model. From gut shots i have of it i can say that there is indeed another resistor and trimmer at HRM board. I'm going to study it little more later, after school:)

[ayan]

Thanks ayan. It's very helpful. I think i'll give it a shot.
I found out that TR you talking about is OPAL model. From gut shots i have of it i can say that there is indeed another resistor and trimmer at HRM board. I'm going to study it little more later, after school:)

I never heard that myself, but I am sure there is a good sound to be had from that arrangement. Hope you can give it a try and report your results later to the rest of us.

Cheers,

Gil

[mbeldyga]

Sure i will, but this can take some time. High school, work, driving license exam and other stuff don't leave me much free time. Also i'm still waiting for chassis so this tread is just theoretical (right now:) ). But as soon as i finish with amp i'll post my obs.

[mbeldyga]

I just finished soldering main board for my amp, and totally forgot that i wanted to implement this mod and already solder 10n coupling cap after second gain stage in OD section. I could desolder it but this board looks to good

So i left with one relay and one hole in chassis for small switch. Any ideas how to use it?

[Structo]

Not sure what you already have on the relays but the one mod that switches the bright cap on in clean mode and off in OD mode is a good one.
I have that on the front panel bright switch and relay.
You use the OD relay to trip the bright cap relay.

[mbeldyga]

I have four button footswitch and so far i have FET on/off, OD, and PAB and for the last switch i was thinking mid boost maybe?

[Structo]

Yeah if you like mid boost you can put it on the foot switch.
I put that on a pull/push mid pot switch but I don't really find myself using it much, if at all.
I may try the Deep switch instead and see if I like that.

[mbeldyga]

Deep switch? I might try it.

Have you tried switchable local feedback?

[Structo]

Yes, I have that on a switch on the back panel.
I just have on and off on mine but others have made it with a couple resistor choices.
Next to that I have a mid cap switch for choosing .01 or adding a .05 for a total of .06

[mbeldyga]

And how do you like it? Do you use it often?

[Structo]

I leave the mid cap on the .01 the majority of time.
If I play lower volume (when wife is home) it can sound good with the added cap.

The Fat/ Raw LNFB switch is subtle but more apparent at louder volumes.

The best thing is the OD trimmer pot on the back.
You can set it low for a cleaner or more raw overdrive tone or set it higher gain and smooth it a bit more.

[LPSGME]

I leave the mid cap on the .01 the majority of time.
If I play lower volume (when wife is home) it can sound good with the added cap.

The Fat/ Raw LNFB switch is subtle but more apparent at louder volumes.

The best thing is the OD trimmer pot on the back.
You can set it low for a cleaner or more raw overdrive tone or set it higher gain and smooth it a bit more.

I just tried lifting the LNFB last night and found the effect definitely worthy of a switch.

I think I'm also going to add a resistor to lift the input volume control further from ground and then jumper the resistor with a relay that will short it when the PAB is ON - so that the clean and PAB signals are more equal in volume.

Has anyone found any improvement by bypassing an HRM's trim pot tone stack? I can't imagine it doing anything good.