Seems a little funny, Winecaster.  The boost volume is pretty substantial, but the amp should be pretty loud without it.  With the volume and master at 12:00 on the clean channel it should be plenty loud without the boost.   The amp controls are complicated enough, though, that it's possible that you just haven't found the right settings.  It's not unusual for you to have to throttle back the drive channel volume using the ratio control to keep the drive channel volume down so it matches the clean channel's volume properly.

I hope this helps.

If you're a Celestion guy, you might want to try a Greenback or a Blue, depending on what flavor of tone you want.  Like a 25 to 30 watt speaker.  I tend to like Weber speakers - they make Celestion style models, like the 1225 ceramic and also American style speakers, like the 12A150, a 25 or 30 watt alnico with a tweed sound and the 12F150, a 25 or 30 watt ceramic with more of a Blackface sound.  Check here -

https://taweber.powweb.com/weber/

Hope this helps.

That's an awful lot of speaker for a 20 watt amp.  One of those speakers is still kind of a lot for that amp.  They'll work.  They're just big.

Yes - Your amp tech should be able to do this easily.  The last one I did, I used a push/pull pot for the slope control knob and used the switching function of the pot for the rock/jazz switch.  That way, the rock/jazz switch can be maintained while adding the adjustable slope function.

50 Watt BM built by me from the kit.

Adjustable slope control knob. Adjustable volume boost knob.  1x12 cab with Celestion G12H-75.

I use it with a C lator, tube reverb unit and various pedals.

Awesome.

I have an HRM Bluesmaster 50 and have built some OTS20's  They're very similar sounding.  The OTS20 will definitely cover the same territory as the larger OTS models.

We built a Bluesmaster type OTS20 Lunchbox amp.  I call it the BluesBox, lol.  The BluesBox is to the OTS20 Lunchbox as the Bluesmaster is to the HRM.  The tone stack and PAB switching are wired like the Bluesmaster.  We really haven't played the crap out of this amp yet, but it sounds like you'd think.  More Fendery on the clean channel and kind of brassy on the overdrive channel.  Check it out and see what you all think.  And check out the variable slope control.  We call it the Allegiance Knob.  It leaves the rock/jazz switching intact but allows the slope resistance in the tone stack to be varied from 50k to 100k.  It's kind of like a Marshally/Fendery control.  Revisions are shown in red.

I ran some models on the tone stack:

1.  The most effective thing to do is to be able to get the slope resistance up.  That will scoop the tone. Mine is adjustable from like 34k to 108k.  Stock is 47k.  Best thing to do might be to keep the 47k slope resistor and add a b50k push/pull mini pot in series to make it adjustable from 47k to 97k.  Install it thru the rock/jazz switch hole - slight reaming is probably required.  Maintain the switching function of the rock/jazz switch but install the components on the p/p pot.  That way you have a slope dial plus the rock/jazz switch.

It really makes a lot of difference.  It's almost like a Marshall/Fender knob.  I did mine a little differently but then realized that I should have done it this way.  Next time I'm in there I'll redo it.

2.  Changing the 330p cap on the mid boost switch - that's the treble cap in the tonestack - to a 300p will change the effective value (in series with the .002 uf) from 326p to 283p.  That widens out the scoop range a little.  It makes the curve more Fendery.

This made a little bit of difference in the breadth of the scoop.  I'm going to try this ASAP.

3.  I might try upping the bass cap to a 0.047.  Even though is seems counterintuitive, it might help to separate the highs and lows some.  Maybe I'll clip another 0.022 in parallel with the existing one and A/B it.

You can try changing the slope resistor (47k) to a higher value, or you can make it adjustable.  On the clean channel the amp seems to like a higher slope value - that will make it sound more scooped.  The drive channel seems to like a lower slope value.

On the overdrive channel, pay attention to the internal tone stack settings.  The internal bass pot needs to be just cracked barely open.  See the note on the layout sheet about setting the post-gain tone stack.

The BM has a .002 with a 390p in series.  That's effectively 326 p.  When the mid boost in engaged, it puts the 390p cap in parallel, giving an the effective value of 2390p.

Other models are similar - some just disengage the small cap completely when the MB is engaged. The Modern Eagle has a 0.001 in there with a 390 in series - that's 280p/1000p.

The OTS lunchbox is like the modern eagle - 280p normally, 1000p with MB engaged.

If you wanted a lower effective value, you could use a .001 with a 330p.  That would give you 1330p in mid-boost and 248p without the mid boost engaged.

Or use a .002 with a 330 - yields 283p/2330p.

Please check my logic and math.

The main thing to keep in mind is that the effective value with MB off is controlled by the small cap and the mid boosted value is controlled by the big cap.

I think I might just swap out the 390 on mine for a 330 and get myself closer to Fender territory.

HRM Bluesmaster 50 in a denim covered cab -




And then built into a Dumble style combo cab with C-Lator slot -

Not sure how to do it, but you might be able to figure out what to do by studying the schematic for your amp and comparing it to the schematic for the new '68 Reissue Twin Reverb.  I think the newer '68's have reverb on both channels.  Not sure.  But looking at the schematic would be the place to start.

The Fender Supersonic amps also have reverb on both channels.  Studying those would help.

We recently finished up a Bluesmaster 50 build and made a couple of mods. 

We removed the rock/jazz switch and added a slope pot to adjust the slope resistance in the tone stack.  The rock/jazz switch was kind of doing the same thing, but in a less effective way.  The mod provides a usable range of 33 to 108 kohm for the slope resistance.  You can get more distinctive Marshall vs. Fender voicings, and the volume doesn't change when you adjust the setting.  To do this, we removed the rock/jazz switch, replace the 47k r on the board with a 120k, installed a 1mA pot in series with the 47k r and installed that ass'y in parallel with the 120k r on the board.  Installed the pot in the switch hole (slight reaming required) and reconnected all the loose wires - which was pretty easy to figure out.  I can provide a layout if anybody wants it.

We added a pot to adjust the PAB volume boost level.  This was done by replacing the 68k r on the tail end of the mids control with a 22k r in series with a 50kb pot, providing a resistance of 22 to 72k.  We installed the pot through an existing hole which we slightly enlarged in the chassis located between V3 and the power tubes so it can be adjusted from the back of the amp.  Wired it back to the mids pot with shielded cable.  We plan to install a p/p pot in the mid-boost switch hole so the boost can be adjusted from the front and to keep the mid boost switching intact.