Advice on setting up HRM

[pedro]

Hi all,

I built an HRM ODS-50 ( BM circuit ) back in 2006/2007 with a lot of help from dogears and a couple of others on this great forum.

Over the years its been HRM, then Non-HRM , and now I have it back to HRM. Its definitely a great amp and one of my favorite builds.

To be honest I've been playing it so long now I cant quite trace the evolution of all the tweaks and circuit changes I made with all the advice I got !!! I shoulda kept all those old emails and mssgs !

But now I have the urge to open up the amp again and try to optimise my OD tone , I got to wondering whether there was any good way to tweak the HRM settings for the sweet spot ?

The amp has fantastic creamy cleans, and the OD sound with PAB is already great - but I never felt I was optimising the post-OD HRM tonestack settings really and it was a bit hit-and-miss.

I know the HRM tweaking depends on so many factors - guitar, speakers, playing style etc, but does anyone have a view on the best way to go about setting the HRM trimmers ?

I'd welcome your views
Thanks
PeteC

[tjauernig]

I like to put in another relay or a push/pull pot and make the HRM switchable in/out. Then you have 2 OD tones at your disposal

[boldaslove6789]

Try to post some pics of the inside of your amp and we might be able to help you better the sound of your amp.

Following Dumble Lead dress, and parts choice is sooo Key to great OD tones.

[pedro]

OK Greg
I'll get some pics done.

have to admit that this amp was built in an old donor tube p.a. chassis - so not the standard chassis at all.

Having said that the build is dead quiet and has plenty of sparkle when needed - so not worried about cable run capacitance losses etc. The clean sound is extremely dumble-esque so I'm pretty close i think.

Also I used a variety of parts that I had in my stash rather than building to exact component types - so maybe there is an impact there too.

Will get the pics uploaded

Rgds
PeteC

[phsyconoodler]

There are no global settings,how could there be?Every amp reacts differently and every players touch is different.The best way to make an HRM to work is to put the controls outside the amp or have access to them through a trap door like Fuchs has done on their latest amps.
To hide a set of EQ controls inside a chassis is kind of silly to me.
Just my .02 cents worth.

[ayan]

There are no global settings,how could there be?Every amp reacts differently and every players touch is different.The best way to make an HRM to work is to put the controls outside the amp or have access to them through a trap door like Fuchs has done on their latest amps.
To hide a set of EQ controls inside a chassis is kind of silly to me.
Just my .02 cents worth.

Having built enough HRMs, I think I have some global settings that will probably work as a starting point for someone new to tweaking the HRM beast. To me, those controls proved to be almost as difficult to tweak as the PI trimmer. Let me qualify my answer below, my goal was to try to set the HRM tone controls so that the OD would be more or less an extension of the clean sound, and not sound buzzy when the gain was turned up. If, on the contrary, you want to dial a radical overdrive with tons of low end, the HRM will probably be much easier to fine tune. Having said this:

1. The bass trimmer is 1 Meg and linear which means most of your bass will come on all of a sudden as you turn up the trimmer. I think I found my sweet spot around 90-100 Ohms beween the wiper (which is tied to the CW end) and the CCW end. Some people set this higher, but I think in most cases replacing the 1 Meg trimmer with a 500K ohm one would make the range more usable.

2. The middle control is 20K and, IMHO, it can make or break the sound of the amp. I would set mine around 8 K between the wiper (again, tied to the CW end) and the CCW end. Now, the advantage of turning the bass up from my starting point is that you will have more of a usable range in the middle and treble controls before the amp sounds harsh. The problem to me was that turning the bass higher would make the OD sound less like the clean channel.

3. The treble control will adjust the overall brightness of the sound. The trimmer is 250K and I would set mine with about 100K between the wiper (not tied to the CW end) and the CCW end.

Mind you, speaker choice will change things radically, and my settings were tamer than everyone else I ever talked to about this. I use EVM speakers, which most people consider to be bright, and in 1x12 configurations. If you use a 2x12 or 4x12 cabinet with Celestions, you will probably be able to -- and need to -- turn all trimmers up, especially midrange and treble.

Agreed that, ideally, these controls would be outside the amp so that you could go for midrange heavy to scooped tonality at will. The most elegant implementation I have seen was by Gary Johnson, since he worked towards customizing the range of the controls to where there is not a bad sound to be dialed in on his amps -- can't say the same about some Marshalls, for example.

Hope this helps a bit,

Gil

[phsyconoodler]

It seems to me that the values are wrong if they come on too quick.A revamping of the HRM controls would give more pleasant results if you ask me.
This is likely why I don't like HRM's.To have an EQ for the drive channel makes perfect sense,but if the controls are too touchy it makes no sense.

[ayan]

It seems to me that the values are wrong if they come on too quick.A revamping of the HRM controls would give more pleasant results if you ask me.
This is likely why I don't like HRM's.To have an EQ for the drive channel makes perfect sense,but if the controls are too touchy it makes no sense.

The thing is that all trimmers are linear taper, if they were audio they would certainly be easier to dial in. Another good reason for putting the controls outside since it allows using audio taper pots instead.

Gil

[stelligan]

Outside control is how heisthl implements Drive 2(HRM) on his RedPlate "Dust" series. That Magic Dust is an end all amp for me. Favorite amp of my own builds was a 50 watt modified D'Lite HRM. It took FOREVER to set those internal trimmers to taste. Setting the bass was a bitch. Barely on seemed to work best - the trimmer acts more like a switch at stock values....

[pedro]

Gil,
thats really helpful, and I am shooting for a similar situation to the one you describe ...where the OD becomes an extension of the ballsy end of the clean tone ( when the input gain is set fairly well up ).

I don't want to have any fuzzy artefacts around the edges of the fundamental tone - if that makes sense.

You know that tone when you use something like a rangemaster or treble boost at the input but then attenuate most of the highs on an amp and get a really nice violin-like pure tone.....thats what I hear in many OD clips and on some RF tracks and want to get as close to as possible. Its close i think - though i realise there are so many external factors. I'll try the setting you suggest

I have 2 speaker setups - one a 4x12 closed back with x pattern V30s and G12K85's, the other is a 2x12 with Fane Studio 12's.

Anyway thanks very much for the tips guys.

I'm almost embarrassed to share pics of the guts knowing how clean many of your builds are here - but this was always a test-bed donor amp that stayed ODS-50 cos it is so nice a sound . I'll post pics soon for critique.

Rgds
Pete

[ayan]

Hey Pete,

I can share this with you: one can never go by what you hear on a recording. Most recorded guitar sounds come from mic'd cabinets and too many things come into play. I don't believe I have been on any recording session where the engineer hasn't said he needs for the sound to be brighter that I would like to hear as I play it. They can take the edge off on the mix later if needed...but you cannot add clarity if there was none to begin with.

Some people have played RF's amp, many others have seen RF live over the years. Robben's sound can be painfully bright live, and those who played his amp have said the same thing. So, you may want to take the "violin tone" with a grain of salt. Also, Robben's amp is not an HRM. Personally, I have always found the non HRM amps easier to play and to dial in, since you have fewer choices of what to mess with.

Cheers,

Gil

Gil,
thats really helpful, and I am shooting for a similar situation to the one you describe ...where the OD becomes an extension of the ballsy end of the clean tone ( when the input gain is set fairly well up ).

I don't want to have any fuzzy artefacts around the edges of the fundamental tone - if that makes sense.

You know that tone when you use something like a rangemaster or treble boost at the input but then attenuate most of the highs on an amp and get a really nice violin-like pure tone.....thats what I hear in many OD clips and on some RF tracks and want to get as close to as possible. Its close i think - though i realise there are so many external factors. I'll try the setting you suggest

I have 2 speaker setups - one a 4x12 closed back with x pattern V30s and G12K85's, the other is a 2x12 with Fane Studio 12's.

Anyway thanks very much for the tips guys.

I'm almost embarrassed to share pics of the guts knowing how clean many of your builds are here - but this was always a test-bed donor amp that stayed ODS-50 cos it is so nice a sound . I'll post pics soon for critique.

Rgds
Pete

[tubedogsmith]

FWIW, I've struggled with the HRM circuit for a long time and really disliked it for the most part, real HRM Dumbles included. After woodshedding with one of my builds for about 6 months I finally got what I think sounds at least as good and IMO better tone for what I like than the non HRM.

The HRM slope resistor is 100k and the treble cap is 330pf. I set the 1 meg bass pot at 130k, mid at 4.5 to 6k, and treble between 82k and 95k.

[Bob-I]

Great explaination alyn. I've found the a properly dialed in HRM sounds amazing, a poorly dialed in HRM sounds like total junk. I also learned that setting the HRM on a bluesmaster is a totally different beast, dogears helped me out and my bluesmaster sounds awesome now.

[boldaslove6789]

Personally, I have always found the non HRM amps easier to play and to dial in, since you have fewer choices of what to mess with]

Indeed I aggree, I dig HRM's but often without the PAB engaged they can sound, well, muffled, like a blanket is over them, they really have to be tuned to sound right for certain picking style, pick attack. Just recently I switched to Non-HRM's almost exclusively as they can be clearer but at the same time very unforgiving, whether you like it or not. But I guess it's all preference.

[ayan]

I had forgotten about that! Because of the characteristics of the PAB in regular Skyliner amps (i.e., losing quite a bit of bottom end), setting the HRM for both OD and OD + PAB proved to be all but impossible for me. The Bluesmaster mega boost style PAB is a different animal and made it easier to find HRM settings that worked both with and without PAB. Still, too much of a headache, and in the end, I wished I had access to more sounds since I knew they were in there, accessible through the trimmers. Non HRMs are a "one trick pony" which is a good thing IMNSHO.

Cheers,

Gil

Personally, I have always found the non HRM amps easier to play and to dial in, since you have fewer choices of what to mess with]

Indeed I aggree, I dig HRM's but often without the PAB engaged they can sound, well, muffled, like a blanket is over them, they really have to be tuned to sound right for certain picking style, pick attack. Just recently I switched to Non-HRM's almost exclusively as they can be clearer but at the same time very unforgiving, whether you like it or not. But I guess it's all preference.