I guess if you like more treble you could try the HRM. Although it has an extra board for post OD tone stack I see no reason you would need it as you can vary the OD other ways.

I have an HRM and went back more toward the OTS.

As Boldaslove said, you really can't go wrong with either a BM or OTS. Plus, depending on the brand of tubes (or combination of brand) used; the model of speaker used; and style of guitar and/or pickup(s) used - not to mention the variation delivered by all the controls [external and internal] and bias setting - there's probably no tone that you couldn't near achieve with either model.

I think Nik might also be able to supply an alternate brand of transformer like an MM if you prefer.

IMHO, I'd say get a regular OTS, especially if you're using a strat. I found the HRM a bit to trebly even for humbuckers.

I think most people prefer the non HRM. Get one, you won't regret it.

Looking inside [with the faceplate facing you] right behind the Treble control is a small board with 3 trim pots (round nickel size black and white pots) for the HRM tone stack. The from let to right are the treble, bass and mid controls.

The trim pots are adjustable using a small screw driver type tool.
WARNING: As there are dangerously high voltages in a tube amp that can kill, it is best to use a non conductive plastic adjustment tool designed for such purposes.

Then, moving further towards the rear, is a larger board that has the pre-amp parts ect.
There are 2 similar pots on there. The one just left of center is the OD trim. The one to the right near the edge of the board furthest from you is the PI trim. That will adjust the balance between the two halves of the inverter tube V3 that drives the output tubes. By changing that you should hear a difference which you can adjust to taste.

Again, adjusting pots while the amp is ON is dangerous, as there are very high voltages inside that can kill.

The name plate is different between an OTS and HRM.
You can sort of see them in this youtube post comparing them.

Sounds interesting. I never experimented to determine just how much a standard stack clamps the signal.

I assume the degradation is due to the load of the ground path hanging on the tube's output. Is there no way or easy way (using tubes) to capacitively separate the treble, mid, and bass and then sum them without using a ground path to reduce their level.

However, sometimes people want the lesser or particular tone that comes from a stack. I believe, for example, the stack design accounts for the difference between a Tweed and Blackface tone - with the 60's having a stronger scoop in the low end so that it sounded cleaner.

Without the stack, the sound is much more robust, which may not be desirable as the only tone.

So maybe the optimal thing to provide the ability to switch between two levels of the stack sound in addition to the direct sound - all of which could be adjusted  by a simple gain pot. That would simply require reducing the gain of the stack for use as the normal sound, and simply eliminating the gain reduction for the relative boost. Then there can also be the option of the sound with the stack bypassed, with a level control.

The circuit layout of the regular OTS and HRM are pretty much the same, with the exception of a gew different part values. So you can easily mod an HRM to be like the OTS. IMHO the internal HRM tone stack at the end of the OD stage is nothing you would miss if you didn't have it.

Knowing this, and that I'd preferred the standard OTS sound, I got an HRM - but only because one was immediately available on ebay and it had several options added.

If you do not intend to build it or mess around inside, then go with the OTS.

I didn't notice much difference in how my tone controls operated with the 10k detached, which is not quite what I would expect.

However, I removed it in effort to get less volume difference between the normal and PAB volume. It seems that the tone stack clamps the sound and volume and that all the PAB does is free it from clamping. So I think the difference, if any, is that the normal sound is a tiny bit more free sounding.

I was mostly trying to get an OD sound that I liked. As I recall the change from lifting the 10K was more noticeable when using the OD than clean.

I've read people complain that activating their OD stage made their sound darker. In the HRM, I found the OD to be too hard and shrill. That is why I increased the interstage coupling cap from .002 to .01 (to be the same as the OTS) and added a treble bleed in front of the OD stage. In listening tests, to me, removing treble at the end of the stage (like the HRM stone stack affords) does not sound any where near as good.

It's too bad there aren't really any sound clips comparing transformers on a overtone, being it's an major expense and not the kind of thing that easily swaps in and out.

However, I think I'm pretty satisfied with the amp's sound. I only just finalized my mod today. I wanted to be able to get a mellow horn like OD, and pretty much ended up with an OTS but with a few differences.

In sequential order around the circuit they are:
1) V1a plate/cathode changed to 120k/1.8k;
2) V1 cathode caps changed to 10uf;
3) Bass control 10k resistor to ground removed;
4) V1b to master volume coupling cap reduced to .02 (from .05);
5) Master volume 47pf bypass cap removed;
6) Switch added to 47pf cap across 470K resistor at OD stage entrance;
7) Three way switch adding .0062 cap; .0022 cap; or no cap; to ground before 470K resistor at OD stage entrance; (treble bleed);
V2a to V2b coupling cap increased to .01 (from .002);
9) V2 cathode caps changed to 15uf
10) External PI trimmer pot;
11) Short black plate RCA at V1; JJ at V2 and PI.

Tell me...
I'm still wondering if a different tranny would help much towards getting a smoother sound.
Oh, I also lowered the .05 cap from V1 to V2 to a .02.

Oh, I meant to type 100K (not 100) and of course I also changed the cathode resistor to compliment.
100k/1.5k.

The standard plate cathode resistor scaling is:
100k/1k5 - 120k/1k8 - 150k/2k2 - 180k/2k7 - 220k/3k3

A lower plate resistor is supposed to make the clean stage clearer and less compressed. But it might also sound thinner unless the cap from cathode to ground is at least 10uf or even 25uf and not the 5uf that it usually is with a higher plate resistor.

Fender amps typically use 100K plate resistors.

But then don't you know this?

Interesting comments.

I added several mods to my HRM so it's also not stock: increased V1a and V1B cathode bypass caps to 10 and the V2a cap to 5; increased v2a to v2b coupling cap to .01; increased V1a .002 coupling to .004; lowered the v1a plate resistor to 100; removed the master vol bypass cap; removed the 47p/470r network at the OD entrance; lifted the 10K from the Bass control; and added an external pot for the PI trim.

I'll have to try changing the PI tube to a T or Y to see the effect.

I had JJs in my HRM and decided to try some old RCA back plates (one long and one short) in V1 and V2. But they seemed to smooth (especially the long plate).

However I did like (decided to go with) the short plate in V1 and the JJs in V2 and the PI.

Do you know if your amp was a factory build or did the person you got it from build it?

The wrong part placed somewhere, resistor or cap,  can boost the bass.