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Hartman LM308 Op Amp Distortion

KRAA!!

By KRAA!!
in Effects and Processors

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VonBonfire Newbie

VonBonfire

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Yes, I JUST got a Hartman Germanium Treble Booster. I think I damn near got the last one with the Mullard oc44 transistor. Let me tell you, inside is one clean machine. Please read on.

 

It's mil spec wiring so it's quality. True bypass of course. Beautiful paint job. The LED on this sucker is so bright it is blinding even in broad daylight. I could go spelunking with this thing.

 

The oc44 is one of the sweetest sounding fuzz transistors I have ever heard. There isn't a ton of break up there but what you do get is so warm. Such a natural sounding unit. Awesome. No wonder they are sought after.

 

Onward.

 

I'll post pics later tonite.

 

I just sold my Rat 2. I want that freaking pedal NOW. I do have a couple questions for Theo before I order again. I also need to come up with more cash, as this shit costs a bit of money. 150 bucks right now for the op amp distortion. Sale price. He is definitely competitive with the other boutique makers though.

 

Let me tell you about Mr. Hartman himself and plug his company a bit since he doesn't get much publicity in comparison to Keeley, analogman, etc. He is a really nice guy. I'd love to see his products take off like these other guys but then I couldn't get Theo to respond to my questions personally like he will do for you at this point in time.

 

Mr Hartman tweaked the boost range to mid/full settings rather than mid/hi. He didn't charge me extra for any of this and I believe he took a deal of time to tune it.

 

His responses to my questions were so thorough. I've never had this kind of customer service. So now, since I have one great product and have been offered a 10% discount on my next order, I'm more than likely gonna have a shot at that LM308 Op-Amp pedal or possibly his germanium fuzzbox. Decisions, decisions.

 

Anyway......Theo if you are reading this....You rock. Your pedals rock. Don't change a damn thing.:)

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zacheryhunter Newbie

zacheryhunter

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Yes, I've seen the Keeley and the FKR, but I haven't seen FOOTSWITCHABLE clipping diodes. Oh wait, someone already caught that. A good idea if you ask me. I would really like one of these. Maybe in a few months after I gather some funds. I'm not sure I would use the second footswitch all that much, but it may eliminate any temptation to use more than one pedal.

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theohartman Newbie

theohartman

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VonBonfire, glad you're enjoying your pedal!

 

The LM308 pedal uses diode clipping for one of its two distortions (the one that emulates the rodent identified by the chinese zodiac symbol). No diodes are used in the other mode.

 

When I designed this pedal I experimented with alternative forms of diode-clipping quite a bit. Some of them are cool, but they all shared one thing in common--they tended to 'mask' the tone of the instrument and supercede it with their clipping tone. Granted, predictability can be virtue: the quarter-pounder with cheese, for instance. But I was interested in opening the sound up a bit, making the distortion less one-dimensional, and getting a feel closer to straight-in into an overdriven amp. The LM308 is a cool chip for this kind of thing because it allows you to alter its frequency response externally, something not all chips do (e.g. the 4558s). It also breaks up nicely, especially the -AH.

 

The second distortion mode comes from the chip alone, via altered compensation and feedback. It's a different sound, one that could rightly be put in its own pedal, but with pedalboard real estate being what it is these days, and the fact that it shares a chip in common with one of my favorite distortion pedals growing up, I opted to put them in the same box together.

 

Best,

 

-theo

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willburford Newbie

willburford

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Hmm, I might just get one of these. How do the asym/sym sides differ? I see that hartman said they are different, just wondering how they are different.

Also, can this do low gain sounds well? If so, I'm sold. Well, between this and the Brown Rabbit... and then there's all the modded rats out there...but I think I'd rather have this...

 

I'm overwhelmed. And no, I'm not referring to the forumite.

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theohartman Newbie

theohartman

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hello-

 

tolling bells, probably the most noticeable difference between the two modes is the increased headroom and transient response of the SYM mode--that, and the absence of the diodes' signature 'midrange hash'.

 

diode clipping achieves its magic at the expense of lopping a volt or two off the peaks of the signal. SYM removes this constraint. in SYM mode, the controls affect how much you're overdriving the LM308, not the diodes. as a result, in SYM mode, you can actually achieve degrees of breakup/clean-up at lower settings of the Distortion knob in ways you can't in Mode A (RAT-type).

 

another way of describing the difference might be: in SYM, if you want to be able to tell what kind of guitar you're playing through the pedal, you can. 8)

 

a quick clip is on the product page on the site. i hope to have a more illustrative one up in the coming weeks. i have some soldering to do in the meantime.

 

best,

 

-t

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  • 3 weeks later...
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KRAA!! Newbie

KRAA!!

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I ordered one of the LM308 pedals. I'll do a comparison when I get it.

 

Well, I got the LM308 distortion. The dual-color LED for the two modes lights up even when the pedal is off so you know which mode the pedal is in before you turn it on. This is convenient because there's a large difference in volume between the two modes.

 

As I expected it sounds like a Rat. The tone control doesn't seem to allow as much treble through as my old 1982 big box Rat, but that might be partially because of the metal can LM308 op-amp I ordered (Theo Hartman suggests that it has less treble). Overall the LM308 sounds just slightly less aggressive than the old 1982 Rat.

 

BUT the 2nd footswitch disconnects the clipping diodes and changes the EQ of the pedal a little. Here is where this pedal kicks ass. It's much louder, smoother, and has less gain as I expected. It also has a huge amount of sustain and a little more bass. I guess this just is the way the pedal reacts; it just must be a lot of compression with this combination of components.

 

Summary: great Rat like pedal with a kick ass non-TS overdrive built in. :love:

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  • 7 months later...
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Jules-RM Newbie

Jules-RM

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Thread ressurrection time.

 

My Keeley Rat has been giving me problems lately. Once and a while I when I hit it, no volume. I think the switch is giving out. I can just tap it off then on again and it usually works. Thing is, this is about the 4th problem I've had this particular Rat. I just don't trust the damn thing anymore, and I'm tired of sending it back to Keeley.

 

I've just got a Brown Rabbit, and I don't like it very much. It's close to a Rat, but it lacks the deffinition and focus of the Keeley Rat. Side by side it sounds very similar, but at practice it wouldn't cut through the mix like the Keeley Rat does.

 

Hows the Hartman? What I'm looking for is basically the sound of the keeley Rat with the switch to the right (stock Rat). I wouldn't mind if it has a bit more bottom end than the Keeley.

 

Thanks.

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