Summary of what I have learned + some clips and schematics

[Tonegeek]

Its been 2 years since i built my HRM clone so I thought I would share what I have learned over that time.

I started with the ODS 101 HRM version. It initially sounded not so good. The OD was buzzy, tinny and unmanageable in the sense that I could not get repeatable results. The cleans were sterile. After fussing with it for a while, I started getting help from the forum. I also got some help from groovetubin (Jim Price - Omegaamps.com) who lives close by. He gave me lots of ideas, most of which helped the amp sound better. Some of the tweaks were in contradiction to most Dumble schematics I had seen, but he really opened my eyes to the infinite possibilities born of having an open mind and using my imagination. I continued to tinker with the amp, mostly with the OD section, trying to squeeze more tone and consistency out of it. Getting the OD sounds was still a hit or miss thing. One day it sounded good, the next it did not usually due to one knob being moved. I finally got to the lets rip it out and start over phase as I had drifted far from the Dumble way. I ended up going back to basics, but I decided to go with 220k, 150k plates on both preamp tubes instead of the ODS 101 values of 220k, 150k, 180k, 120k. I did the Bluesmaster PI and OD but kept the Skyliner preamp. This made a big difference in the OD character and was in the direction I needed to go. I also started tweaking for a better clean sound as I basically wanted the amp to go from clean to mean but keep the same tone. When I hit that OD button I wanted the tone to stay the same, but with some crunch. I monkeyed with the slope resistor and the mid caps a lot, finally settling on 100k for my slope and .01 for the mid cap. There seems to be consensus that Strats sound better with the .047 but after much back and forth, I found the .01 more transparent and it appears to affect the frequency that my amp needed to have tamed. Of course the slope has something to do with that too. I also ended up with 235p on my treble cap which gives me a smoother, chimey high end.

I still had issues with OD so I decided to vary the HRM mid cap. Changing this area had one of the most positive impacts on my tone. Basically, the tone went from thin to fat. I found several cap values that I like so I put them on a 3 way switch. I use this switch when I switch guitars and now can't live without it.

At this point I have my cleans and OD pretty good. I tamed the mid boost to 1n82, down from 2n (.002). This gives me the SRV sounds I like in OD. Before it was too "Tube Screamer" for me.

Up to this point I could not really use OD+PAB - it sounded really middy. OD+PAB+Mid boost sound good and SRV sounds were gotten with OD + Mid Boost. So, my next goal was to get the OD sounding good with PAB. I had noticed a post by 'yeayea' where he was switching a single 500p cap from the top of the slope resistor to the bottom of the treble pot and doing the normal PAB with the same switch. I decided to try this and it is fantastic! I use 910p instead of 500p as it is fatter. I now get full OD with just 2 buttons. Mid boost still has a slight impact though and if I need slightly more bottom (not normally) I will kick it in too.

Some Bluesmaster schematics show a .01 or even .001 cap before the HRM tone stack. I used .01 in mine but later removed it to the improvement of the tone. This opened up some more bass which I could then roll down slightly with the HRM bass trimmer with the effect that I have more low mids now. Others have said this cap is not needed, and I agree. The only downside is now my SRV tone is not quite as good as it was because of the increased low mid. I think I can work around this though becuase I now have another Strat that is more vintage sounding than the one I originally recorded the SRV clips with and I think it will give me that woody sound on the low strings even with the changes I made to the amp.

ok this brings me to my latest tweak. After 2 months of no tweaks and thinking I was finally satisfied I made an accidental discovery. I had read a post by 'ayan' that claimed the best tone is gotten by getting the OD master cranked. I had come to this same conclusion way back when, but for grins I decided to turn the OD master down to 9 oclock and crank the send up to 3 oclock. whoa! it sounds better this way on my amp. I was very surprised. There was a little too much high end the other way and now its just right. I still get the same OD but without any brittleness. I thought I had gotten rid of all that, but sometimes when there is nothing to compare too, then you just don't realize what is going on. Now I know. This setting got me to thinking on how to make the amp more consistent (and by that I mean when you turn a gain/level/volume knob, the level changes, but not the TONE). Usually you do this with bright caps but before I can add a bright cap, I have to have the tone at the higher settings working correctly. My amp is bright when the level is high and rolls off the highs when the level goes down. So what needs to happen first is to get the high setting harshness out and I thought of one way to do this. THe OD entrance normally has a 47p || 470k combination but On mine It was 47p || 180k and the 470k unbypassed. I removed the 47p and things got slightly better on the high end. Then I added some shielded cable to the drive pot output and that helped a bit more. It still has a bit too much highs, but I think with one more run of shield to the drive pot input, I will have it. (Ironically, this will end up looking just like most Dumbles with 4 runs of shielded wire, and also like the Bluesmaster OD entrance that shows no bypass cap. HAD knew what he was doing:)) Then I can start experimenting with bright caps on the OD master.

I am including a schematic that shows my clean and OD sections. you dont see it but I have a clean master and dumbleator. Also have 2 clips of the latest changes.

Recording details: Speaker cab is loaded with 2 Hellatone G12H30 speakers. The cab is an Ear Candy cab. The clips are done with a 57 reissue Strat with Gold Lace Sensor (Holy Grail) pickups. The mic on those clips is facing straight down about 10 inches from the floor and 6 inches from the speaker grill. It is centered between the speakers. Recorded using Audacity with no added effects or eq. There was echo in the amp loop.

enjoy!

EDIT 2/11/09:
Some updates- I have come full circle on the HRM mid values and am now using 19n for my mid cap (might as well be the stock .02). I can still switch it down by 2n increments but it is very subtle and I usually just leave it at 19n. I also re-adjusted my HRM trimmers across the board to-
Input = 13.7k, t=128k,b=81.4k, m=11.31k (measured in circuit, so a contaminated)

I also put the 47p back across the 180k on the OD entrance. I never did add the last bit of shielded cable for the drive pot input. I also now like my OD master better cranked higher for some stuff. It cuts through the mix a little better cranked higher but if I need more thickness I put it down to 9 oclock and crank my FX send pot up to compensate. The changes (especially cranking up the OD input trim) help the amp to sing more and have a sweeter distortion that is more touch sensitive. Also, now with OD on (but no PAB or mid boost) the amp sounds more like the clean channel than ever before,but with some grit. I almost never go to my clean channel now but that is somewhat due to the material I play. I mostly now just live on full OD but working the guitar volume to clean up when needed.

[bluesfendermanblues]

Very nice sound clips - especially the one using the bridge PU IMO. Great creamy overdrive with nice natural (for lack of a more suitable word) compression.

I'm going try out your 910p tweak slope-to-treble-pot-ground to sweeten my OTS 50 a little bit. Its a non HRM model by the way.

[Bob-I]

A common mistake is thinking that the cap before the HRM is in the signal path, it isn't. This cap is connected to a test point, the HRM stack itself is direct to the plate of V2B.

Great tutorial. Thx.

[Tonegeek]

Very nice sound clips - especially the one using the bridge PU IMO. Great creamy overdrive with nice natural (for lack of a more suitable word) compression.

I'm going try out your 910p tweak slope-to-treble-pot-ground to sweeten my OTS 50 a little bit. Its a non HRM model by the way.

I am thinking that mod may give you too much mid in a non HRM but it is easy to try with some test clips. It gives a pretty big gain boost as you can imagine. You can try putting a resistor in series with the cap if you need to tame things a bit. Also try different cap values while you are at it.

A common mistake is thinking that the cap before the HRM is in the signal path, it isn't. This cap is connected to a test point, the HRM stack itself is direct to the plate of V2B.
Great tutorial. Thx.

That makes sense although it is odd that someone would waste a cap on a test point that probably only got used once.
I have seen what looks like test points on dumble pix but never in a schematic. I guess when everything is gooped up, you have to have some way to test.

[Bob-I]

That makes sense although it is odd that someone would waste a cap on a test point that probably only got used once.
I have seen what looks like test points on dumble pix but never in a schematic. I guess when everything is gooped up, you have to have some way to test.

I don't see why either, even if he tests everytime he touches the amp, it's easy enough to put a cap in the meter lead, but I'm not HAD, nor do I play him on the interwebernet.


I finally got to listen to the clips. Sounds great, very much like I'd tweak the OD, but I play mostly hums. Interesting that we go for a similar tone but different PU types. I'd like to hear the clean side as well.

One test I like to do is switch from clean to OD at the exact same volume, to see the transition. To my ears the transistion I'm looking for is heard on Robben's "Don't let me be misunderstood". Nice and bright, a little spanky on the clean side, but warm and sweet on the OD side without jumping out in your face. I've yet to get there.

[JimiB]

sounds really good! Can you do another clip with the mic right up on the grillcloth with the center of the mic pointing at the seam of the speakers dustcap?

[stelligan]

Thanks for sharing the experience with your amp. Very happening HRM Strat tones. This has been my quest as well. Cool playing in the clips too!!

Congratulations.

[Tonegeek]

bobi:
That Robben tune you mentioned is also one of my faves for the tones he uses. I am not there yet either. Every tone on that clip is incredible. My cleans don't have enough harmonic content. Part of it is the fact that I am using a Strat too.

I had a Reverend LP type guitar for a while and was trying to get my amp to play well with the Strats and the Rev. The OD mid switch I implemented on my amp came about partially because of the Rev, and was very helpful when switching between the 2 guitars and even between my 2 Strats. I eventually got disgusted with the Rev and sold it. It did sound great on the bridge pup with my amp and I miss that. There is no substitute for a real LP though so I am holding out till I can get the real deal (the last time I had a good one was in the mid 80's). I mostly play strats because I like the way they feel and I like the tones when playing chords (SRV, Hendrix, Knofler etc.) , but I prefer a humbucker type sound for leads (EJ, Robben, Bonammassa). I am oversimplifying a bit because I also love the rhythm sounds you can get from a really good LP. I seem to only like the LP's I can't have, like this Historic that a friend of mine has and won't sell!

bobi, jimib: More Clips? Well it is Christmas eve but really Christmas is why I decided to post in the first place - my present and a thank you to the forum. So, I will try to sneak away and do some more clips, but it may be a few days in coming due to wife-at-home syndrome. I tend to forget about my clean channel because i live mostly on the OD ones, at least with my current band. I have been working really hard to get where I do it all with the guitar's volume knob. I am considering building a Trainwreck for this reason although the D style amps can sort of get there.

[Normster]

Very nice OD clips! Had a lot of that EJ violin tone going on, but with more mids like Clapton on Crossroads.

Thanks for sharing the details of your journey. It sound like you're on the same path as many of us here who never really "finish" tuning the amp, we just button it up temporarily until the next tweak comes to mind.

Happy Holidays!!!

[Tonegeek]

Very nice OD clips! Had a lot of that EJ violin tone going on, but with more mids like Clapton on Crossroads.

Thanks for sharing the details of your journey. It sound like you're on the same path as many of us here who never really "finish" tuning the amp, we just button it up temporarily until the next tweak comes to mind.

Happy Holidays!!!

Yes, addictions are like that Thanks to you and many others here for the compliments, support and inspiration. Actually double thanks to you for some extra help you gave me a while back. Something you said convinced me to head in the Bluesmaster direction and I have not regretted it. Someday I may implement the full BM schematic, but you hate to mess with a good thing

Per request, here are some more clips - done in a hurry. I broke a string and had to put 9.5 guage on instead of 10s that were on there. what a difference that makes! Sounds real tinny but I made clips anyway... Maybe Santa will bring me some new strings! I repositioned the mike per request by jimib. It is better for the clean recording and OK for the OD one although because of the string change, I like the earlier recording better. If I had the old strings on I might like it better with this mic position. BTW, this is a SM-58, not a 57 as I may have stated previously. The windscreen is gone so it should be about the same as a 57 now as I think they have the same specs without the screen on it.

Merry Christmas people everywhere!