The Boobtube21 HRDLX Mod...

[boobtube21]

OK, this is likely going to sound like the stupidest and most pointless endeavor, but what can I say, I'm a tweaker.

How hard would it be (try not to laugh) to add a preamp volume to the CLEAN channel of a HRD? I realize the Drive channel is effectively the clean channel with a seperate preamp volume, as they use the same tone stack, but I know there's something in there to voice them differently. This 'something' makes the drive channel sound like ass.

Can (not should) it be done? Or would it be easier to, say, change out a couple of components to get a brighter, cleaner sound out of the Drive channel?

Thanks in advance.



No really, I'm serious...

[JAM]

IMO trying to mod an amp like this is a big waste of time. If your real unhappy with the sound, sell or trade it for something that gets the sound you want.

[NTBluesGuitar]

Can (not should) it be done? Or would it be easier to, say, change out a couple of components to get a brighter, cleaner sound out of the Drive channel?

IMO, mods for the HR series really shouldn't go farther than changes in components on the PCBs.

What you're wanting to do sounds like a fun experiment, however, I agree with JAM. If you're THAT unhappy with the sound to go to such an extreme as to add things that would have you be drilling holes, etc., it may be time to look into an alternative amp.

If you're concerned with the drive channel alone, you can do a lot with some component changes. I've done a lot to mine and have it JUST where I want it.

[FrankJohnson]

I used an older SOHO External preamp in the loop and in front of the amp.....In front like a stomp box worked best. It was CLEAN and it was LOUD!

No mod required....and it had like 5 12AX7 tubes in it........I get to use it once in a great while, and would buy it if he would part with it.!

[boobtube21]

Thanks guys,
I figured that would be the consensus, and I've pretty much been leaning in that direction anyways, but I do like to take shit apart.

NTBluesguitar, what sound/change in sound were you looking to achieve, and what got you there? I've noticed a lot lately how dark the sound of the HRD is, did your mods brighten it up any?

[Constellation80]

Id check justins site, he has some great mods on there. I've been wan'ting to find a cheap used HRDX, just to experiment and try things myself

[Guitar_Mc]

If you want another amp, get it.

But keep your HRDx for experimenting on. Wouldn't you feel bad if the tweaker in you screwed up your brand new DRRI?

You might be able to replace components in the drive channel to match the clean channel (+ MV), but you would also have to (probably) cut some traces and jumper past that V2 that the clean channel doesn't have. Once you've done that, I think you end up with a Blues Deluxe.

That would free up some tubes if you wanted to mod in a tube driven reverb.

[NTBluesGuitar]

NTBluesguitar, what sound/change in sound were you looking to achieve, and what got you there? I've noticed a lot lately how dark the sound of the HRD is, did your mods brighten it up any?

Hmm...well, I was looking to really take the harshness out of the drive channels and get usability out of Drive AND More Drive. Ultimately, I wanted my amp to have the following: Clean (no prob there), Blues (settling the drive channel down), and a good Classic Rock (settling the more drive down).

Keeping in mind I have the Celestion V30 in it and some NOS tubes of various makers, everything I did was either from Justin's site (I've done several mods straight from there) or just a component change to higher quality (Sprague Atoms and Orange Drops).

I think if you just want to start with component swaps, you might start with the caps around V3, since they deal with all the preamp signal going to the poweramp. I also bought a replacement Volume pot and installed it in the Master spot...thus giving me an Audio taper there. That helps a lot too. Add a couple of lower gain tubes in V2 and V3, and you'd ought to be having some improvements.

I have a blog article on my website about most of what I did...and you can e-mail me if you want me to get you details from my notes or something.

Oh, I agree about keeping the HRDlx for experimenting. I bought mine specifically for that fact.

[JAM]

PCB amps are a poor platform for serious experimenting. Too many component changes is going to cause traces to lift and you very well may end up with an amp with even more problems than you started with. Then it's resale value is just about zero.

[boobtube21]

NTBluesguitar: Good stuff on that site. Where'd you get those caps from, Mouser? And were they pricey? The tweaker in me is intrigued.

JAM, I know you're right and I appreciate the sound advice. I could probably sell it now and get enough to go towards a DRRI or ? but I've been taking shit apart that I probably shouldn't for as long as I can remember. I'm also experimenting with 'mods' on a car I paid almost $1000 for, but I figure--that's just as much a part of the hobby for me as playing my guitar or driving my car, so what the hell.

I'm not scared, I've broken more expensive things.

[JAM]

OK then, but the mods arent going to turn the HRDx into the ultimate amp. If you change components enough times you'll have a PTP amp though!

[boobtube21]

It might turn it into the ultimate HRD, though!

[boobtube21]

"Yugo nowhere"? Aw, come on...

[boobtube21]

That Yugo looks startlingly similar to my daily driver, a '93 Ford Escort. This is the car I experiment with how long I can go before I fix the stuff falling off of it

[Brian]

One simple mod from Justins site was a jumper on the mid pot:

http://studentweb.eku.edu/justin_holton/jvmods.html

"Follow steps 1 and 2 above. Solder a jumper between the left and middle terminals of the mid control (when facing the amp from the rear, as you would be when working on it). That’s it. You can now reverse steps 1 and 2 and try it out. If you did it right, you should now be able to turn your volume down to 0 by turning all of your tone controls to 0. More importantly, you can now dial in just the right amount of low end with the mid and Bass controls. Remember, they’re interactive. The higher you set the mid control, the more bass you will get. "

One of the advantages is you can turn your tone controls down and volume control up, and then dial in the tone controls a little bit to get good tone at low volumes

[NTBluesGuitar]

PCB amps are a poor platform for serious experimenting. Too many component changes is going to cause traces to lift and you very well may end up with an amp with even more problems than you started with. Then it's resale value is just about zero.

Good points! However, for someone to learn to experiment on tonal circuitry, it's a good platform. I would suggest getting VERY good with desoldering braid first, though.

One simple mod from Justin's site was a jumper on the mid pot...

That's one of my favorites, it makes the amp significantly more dynamic, too, IMO.

NTBluesguitar: Good stuff on that site. Where'd you get those caps from, Mouser? And were they pricey? The tweaker in me is intrigued.

JAM, I know you're right and I appreciate the sound advice.

JAM rules!!!

Anyway, yes...you can get the Sprague caps at Mouser. They have everything! They aren't TOO pricey...well, compared to other components, the filter caps were somewhat pricey. I think $6.03 at Mouser and $5.60 at Antique Electronics (tubesandmore.com). Luckily, you only need 5 of those.

The replacement pots for the HRDlx (if you want to get a new Volume control audio taper for the Master control) are also at Antique electronics for a couple of bucks.

The Orange Drops at Mouser in the 400V range run at most $1.80 I think.

The price can add up, but about $50 would cover most of the stuff I wrote about on my site. I did it in stages, though.

[JAM]

FWIW, I dont think the electrolytics in the stock amp need replacing. Also, I've never been impressed with the way Orange Drops sound. This IMO is an example of 'group think', someone suggests these are great and everyone else just goes along. I prefer the Mallory 150s or even Xicons, (Xicons dont seem to have a 'sound') There are some minor component value changes rather than brands that will have a much greater impact on the sound.

[NTBluesGuitar]

The stock electrolytics don't need it for sound, I agree. I did it because the amp was used and sounding noisy, and I wanted to be on the safe side.

Compared with stock, the ODs made a nice change for me. There's a coupling cap (C23) that is probably the one that needs the most attention in the HRDlx. I upped mine from 1.5nF to .0022uF and it took away a lot of drive harshness; really warmed it up.

Changing the slope resitor helped, too.

[pc]

IMO, modding an HRDx = polishing the brass on the Titanic.

Well... it does have the value of learning amp mods I suppose, but you know what I mean.

That said, the initial point has merit, because I too found that my BLDx greatly benefitted from having my Fulltone Fat-Boost always-on in my signal chain. Fattened things up nicely and masked some of the things that the series of amps is forever and always missing.

But still...

[NTBluesGuitar]

IMO, modding an HRDx = polishing the brass on the Titanic.

Well... it does have the value of learning amp mods I suppose, but you know what I mean.

Not only is it a valuable learning experience, but now that mine behaves nicely, I think it's a pretty darn good practice amp. I can do Clean, Blues, and Rock in the Clean, Drive, and More Drive channels respectively. It's a lot of fun to play with...and isn't that alone worth it? To have fun playin' it?

Now...as a main, gigging amp? You're right...it's not really something worth spending all this time and money on. But again, I think it's a great platform for learning mods, schematics, etc. Of course I bought mine used...I wouldn't buy a new one.

When I'm to the point that I'm regularly gigging, the HRDlx will not come along for the ride. It'll stay right at home for me to practice/play with later.

I hope I'm not sounding obtuse...

[pc]

I hope I'm not sounding obtuse...

Not at all, I agree 100%. My BLDx was my gigging amp for 12 years. My point was that when I really got serious about doing a bunch of mods to it after reading a lot of great advice here, I realized "What's the point? It'll always be a BLDx."

I got really intrigued about the idea of having it gutted and turned into something else (like a Dumble clone ), but why not just spend the money on a whole new, better amp.

It (to me) was worth every dime of the $485 I paid for it in 1994, but when it came down to serious mods beyond usual maintenance... no.