HRM Settings: Not Good :D

[ayan]

Hi guys,

As you all probably know, I am a big fan of non HRM amps, having dubbled at HRMs without much success a long time ago. I decided to tackle the HRM beast again in my latest build, which started off as a full blown BM amp. Tweaked it a while, then decided to lose the BM preamp and changed it into a Skyliner, which I liked better (because of the PAB and overdrive). I then lost the BM PI an reverted to the standard Dumble PI. Finally, following guidelines from you all, I set the HRM trimmers about halway up and took the amp to rehearsal yesterday.

The puppy came out of the cabinet immediately and I started tweaking the HRM settings on the fly while playing with the band. Being totally frustrated, I pulled out my Zendrive and used it for the rest of the rehearsal. I came back home pretty dissapointed and looked for the old HRM boards I had from two previous amps (which I converted to non HRMs, but saved the boards). I measured the two of them and the results are basically the same:

1. Bass control wiper at about 140 K to ground.
2. Middle control at about 13K to ground.
3. Treble control at about 80K above bass control input/wiper.

It was obvious I was trying to get the amp to sound like a non HRM with those settings... I can give them a try in the new amp and see what that sounds like, but I would like to "hear" what all of you are raving about.

Anyway, the amp is 100% a copy of the low-gain HRM. With the settings roughly halfway up, the sound was brittle, harsh, not sustainy, etc. I tried it with my oval ported 2x12 cabinet with some kind of Eminence (M120-8, I believe), which sound good with my non HRMs. At home, I had tried the amp with my 1x12 EVM 12L cabinets, and I was not convinced by that either. The PAB VS non PAB in OD mode is bad in this amp... as no PAB has little gain and sounds dark, while PAB has a lot more gain and too much top end (I kind of remember this). In contrast, the non HRM amps yield two very usable OD tones with and w/o PAB...

Thoughts, suggested settings. etc?

Cheers,

Gil

[stelligan]

Gil,

I wanna love my HRM too!! I think, with a lot of noodling, I can get it where I want it to be. My main bitch is that I want the tonality of my amp to stay relatively constant through the gain stages. I am getting closer, but not there yet. If I could get from clean to OD+PAB without a huge tone shift I would be in heaven. I would settle for 2 sounds on the gig and my guitar volume knob.

I lurk optimistically.........

Dave

[yeahyeah]

I had the same issue with my first build. I thought there was something wrong with it because it sounded so bad. (see my thread "help my hrm sounds harsh") Anyway, i sent it to Hiesthl (sp?) and he worked on it and sent it back. It sounded about the same, still harsh! So I went inside and started tweaking the HRM pots.

I know dogears reccomends keeping the bass at about 50% mids slightly less than 50% and treble at 60% because supposedly this is what dumble did in an amp he has seen.

No offense dogears, but I thought that sounded like crap and I had to go with my ears. I tweaked for several days and I ended up with my bass at 60%, mids at 50%, and treble at about 25-30%.

Sounds much better.

[dogears]

Why no offense? The amp I saw was an EL34 amp. This is what sounded good in it. High treble setting works well in EL34 amps.

Check out my Bluesmaster clip. Settings are WAY different. Mids and bass are both really low.

Every HRM has different sweet settings.

Glad you got it to sound good.

[ayan]

I had the same issue with my first build. I thought there was something wrong with it because it sounded so bad. (see my thread "help my hrm sounds harsh") Anyway, i sent it to Hiesthl (sp?) and he worked on it and sent it back. It sounded about the same, still harsh! So I went inside and started tweaking the HRM pots.

I know dogears reccomends keeping the bass at about 50% mids slightly less than 50% and treble at 60% because supposedly this is what dumble did in an amp he has seen.

No offense dogears, but I thought that sounded like crap and I had to go with my ears. I tweaked for several days and I ended up with my bass at 60%, mids at 50%, and treble at about 25-30%.

Sounds much better.

Thanks, it kind of validates (again) my findings. And thanks Scott for the follow up.

What I will do is defeat the HRM in the amp, at least momentarily and see if it has the "mojo." If it doesn't, I will tweak a bit; if it does, then I will swap in the HRM board again and tweak.

Gil

[JimiB]

Gil,
Do you have a treble bleeder in this amp?

Does anyone do treble bleeders in HRM's?

[mlp-mx6]

Are you guys using similar speakers?

I remember the thread yeahyeah mentioned. Heisthl RAVED about the tone of that amp before yeahyeah had received it, almost as if he hated to return it. Then to learn that yeahyeah found it not significantly different...

Something seems odd here.

[ayan]

Gil,
Do you have a treble bleeder in this amp?

Does anyone do treble bleeders in HRM's?

I do not. I had an OD2 plate bypass cap when I had the BM PI in place, but when that went, so did the bleeder. I used a .001uF OD2 plate bypass in my old (1999) HRM amps as I felt it gave me a little more leeway on the treble HRM trimmer. I know Funk may put "puffs" on HRM amps, depending on each amp. But I guess neither approach is a "bleeder" with a trimpot, etc.

Still, I have never heard of a real HRM ODS having either plate bypass, or "socket puffs," or a treble bleeder.

Gil

[Fischerman]

Does anyone do treble bleeders in HRM's?

I tried one in mine but pulled it out. I prefered the ole bypass cap across the plate resistor.

Wish I could add something Gil...but the fact is the OD on my Skyliner/HRM sounds pretty crappy (and I'm being kind). And it's not the HRM trimmers...it just doesn't distort gracefully or pleasingly so no amount of turning HRM pots addresses the 'problem' (whatever it is). If I want to enjoy OD through that amp I have to use a pedal.

[stelligan]

The experience I am having with my HRM doesn't quite coincide with these findings above. IMHO - I can get the amp to sound damn nice in clean or OD - it's just that the timbre varies too widely from one gain stage to the other. I have been losing the low end content in PAB, but am getting closer and far from giving in.

[Tonegeek]

Gil,
Sounds like you are describing my HRM amp when I first got it going! FWIW I had no luck using all of the accepted values (ODS 101). To get my amp sounding right (well right to my ears) I had to go "off the reservation" and do my own thing after getting frustrated with trying accepted practices. The changes to my amp that made the most difference were in these areas: Treble bleeders around pots, coupler values, the OD entrance, the HRM cap values (mine are non-standard by a big margin), plate couplers. I did stick mostly with the cathode rc and plate r values, and everything past the PI is standard stuff. I don't have any high cuts going on (no snubbers, etc.) I did end up adding a 47pf across the clean master and back on the 470K in front of OD entrance. I have no other pot bleeders. I have 2 proprietary tweaks (thanks Groovtubin!) that helped me a lot but the amp is now at the point where it would still sound good without either one (just different).

I would be happy to share in detail most of what i did (except the two proprietary tweaks mentioned) but I really think if you want to stick with the accepted practices then Scott and some of the other more experienced HRMer's should weigh in first. Maybe just start by lifting one side of any pot bleeders and the 47p at the OD entrance and see if that fattens it up a little. I also found with the standard values, these amps are really sensitive to the gain structure. At first mine sounded best with the volume at about 60%. If I went much over that it thinned out and got buzzy in OD. Needless to say, tweak without anything in the loop till you get a feel for it.
Good luck.

[ayan]

Gil,
Sounds like you are describing my HRM amp when I first got it going! FWIW I had no luck using all of the accepted values (ODS 101)....

Thanks. See, the problem is not making the amp sound good... I can do that without much difficulty. What bothers me, same as it did back in 1999, is that I had to change these guys into Something else to make them sound "good," but some of the real things sounded good all by themselves, as is, no crutches.

Gil

[JammyDodger]

To All,

I am about to start my build of a 100W HRM based on the ODS-101 schematics. This is really starting to worry me as I don't have the experience in tweaking as many on the board here do. There are just too many variables!

Would it make any sense to start with the Non-HRM minus the snubbers and try and dial this in first? Then add the HRM board and dial in from there.

Cheers, Mike

P.S. - I think I'll call mine an OCD (Overdrive, Clean, Distorted)

[nickt]

I'm in a similar situation to JammyDodger. Frankly surprised that so many folks are fessing up to having trouble getting their HRM's to sound good. I must have missed a lot in other posts

Anyway this has convinced me that a straight up non-HRM D'lite is the place for me to start so Merry Xmas everyone!

[Fischerman]

IMHO - I can get the amp to sound damn nice in clean or OD - it's just that the timbre varies too widely from one gain stage to the other.

FWIW, I recently went through my HRM preamp with one of those amp stethoscopes and the timbre in mine was fairly consistent through the first three stages (listening at the plates)...but then when I listened to the OD2 plate it got extremely bright and harsh with lots of buzzy harmonics.

Frankly surprised that so many folks are fessing up to having trouble getting their HRM's to sound good. I must have missed a lot in other posts

I'm new to these amps nickt so when I first fired mine up and it worked correctly with no hum/noise I was probably overly happy...and I still like the clean. But the more I play mine the less I like the OD. I played my Chandler Tube Driver through the clean channel this weekend and it sounded great.