HRM

[WhopperPlate]

What's the difference between the HRM and non-HRM amps? Search function is giving me a ton of hits.

I just got done with an Express build; I'm thinking of starting a an ODS build and I'm trying to nail all the details.

Thanks for the time!

[mbeldyga]

HRM is tone stack for OD section. It allows you to customize OD tone to your preferences.

[Gibsonman63]

HRM is an ackronym for... ?

Can someone humor us heathens from the dark side (TW) of the forum expand a bit on the explanation?

Whopperplate, you are a glutton for punishment. I don't see doing another build until next year. I never realized that amp building could be so tedious, but guys built ships inside of bottles before there were amplifiers.

[greenbottle]

Well Daft Ada
Go to the "Dumble Files"
Look in "Sticky 124 ccts etc" Get a copy of 124 cct pdf.

Go to search. Enter Bluesmaster (all one word) Pick forum "Dumble Files"
Tick box labeled "search for all terms"
Second line. Find BM_DCLONE_100Wv12.pdf Print
Compare output of overdrive in both ccts and observe Hot Rodded Marshall in Blues Master.

Looks like a computer programme. Goto,if then, else

DAFT Slightly crazy
ADA computer language named after female mathamatician(nationality not remembered. Pascal was French but Ada ?)

Alan

[mbeldyga]

HRM is an ackronym for... ?

Hot Rubber Monkey

[ChrisM]

^indeed, not Hot Rodded Marshall, as that does come up.

[erwin_ve]

The tonestack at the HRM Od circuit is a marshall tonestack.

[WhopperPlate]

Thanks everyone.

So HRM; an all internally adjusted Marshall tonestack. From what I have gathered many seem to think the non-HRM is the more "forgiving" and "holy grail" setup; correct me if I'm wrong.

I'm not looking to imitate anyone, just build an incredible sounding amp.

I've read for hours about these amps and I can tell I've only hit the tip of the iceburg. Lots more studying to pursue.

[Structo]

I'm also curious to find out if the guys here that have built both a non HRM amp and HRM amp, both 100w, which style do you prefer to play?

Or how about this.
If you had to pick only one, which one would stay and which one would go?

Perhaps it is apples to oranges but I have an upcoming project and was trying to figure out which way to lean.

[phsyconoodler]

another question to add to Structo's.
Why not use the HRM tonestack on the outside of the amp?

[JD0x0]

Or how about this.
If you had to pick only one, which one would stay and which one would go?

Perhaps it is apples to oranges but I have an upcoming project and was trying to figure out which way to lean.

well if i had the choice between the standard HRM and non hrm i'd chose non-HRM

I use different HRM values to increase the gain (actually reduce less gain) also IMO the values i use make for a much more versatile preamp. Which is also a negative factor especially with internal pots which is why i put the HRM on the front since it's pretty much infinitly adjustable

[da Geezer]

I use different HRM values to increase the gain (actually reduce less gain) also IMO the values i use make for a much more versatile preamp.

Would you be willing to share what those values are??

TIA, Geezer

[JD0x0]

Would you be willing to share what those values are??

TIA, Geezer

Of course

firstly the slope is switchable from 100k to 33k (33K is my favorite the 100k reduces gain but is better for guitars prone to feedback)
The treble cap is 200pf but feel free to adjust to taste. I prefer to keep it low.

now heres where it gets interesting.

I have two separate mid and bass cap settups which are switchable. the first is closer to the HRM nature (20n bass, 8n mid) the second position is a kind of mid shift to boost the low mids and cut some of the deepest bass frequencies to compensate and make sure theres no mud. The switch simultaniously switches the mid cap to 4n and the bass cap to 8n.
This coupled with the 33k slope produces very interesting results and IMO this is where the versatility comes from. with all controls at "0" you get a "mid hump" where the bass and treble gradually drop out leaving the mids. (AFAIK no other preamp can do this or get a hump this dramatic)
setting the tone stack in a "mid scoop" will not scoop the lower mids with this settup but instead was intended to "relax" the harsher frequencies in the 2-3K range. This preamp is also capable of a flat EQ.

to get a better idea plug the values into tone stack calculator and you can see the results. My intentions was to create a very thick OD tone with single coil guitars so slight tweeking may be needed. This is the reason i added the two switches to accomodate warmer guitars.

I also forgot to mention i raise the mid pot value to 100k to give the mids a bigger sweep and more mids if desired. Less importantly i use a 500k bass pot but the standard 1M will do just as well. The build i used these values on was a KT88 build with huge iron so i needed to keep the bass controlled

[WhopperPlate]

So I'm going to make a dumble ODS type amp based roughly on #124 with a bunch of spare parts lying around.

I've got a Fender Bassman Ten chassis with some 70's silver face twin trannys and a Marshall club country chassis and transformers.I also have a Music Man amp that can be a donor, I forget what model (112 combo, dual 6l6 power section). I seem to remember reading that Marshall PT with Fender OT is preferred.

I have a bunch of sprague 100uf and was thinking of running 6 parallel/series for the mains filtering an 20uf for the rest.

I've got a huge stash of Ruby/ Magic Parts polypro orange drops. Anyone familiar with these guys in a dumble type build?

I'll be documenting the rest of the build as it develops. Thanks for the wealth of information everyone!

[erwin_ve]

I'm also curious to find out if the guys here that have built both a non HRM amp and HRM amp, both 100w, which style do you prefer to play?

Built both and still play both with a dumblelator.
HRM is better if you're a heavy consistent picker. It's very attack sensitive.
If you're more a legato player you probably like the Non-HRM better. Non_hrm is easier to play.

HRM controls on the front: several builders are doing that: Glaswerks, Two Rock. It takes some time to develop and test. The position of the pots are very important otherwise you end up with humming amp.