Hertzog Simulator?

[jmusser]

There's been several amp simulators that have come out lately, and ROG has had several of them, but I have never seen anyone try to simulate the Garnet Hertzog. The closest thing I've heard to the violin type sustain it has, is out of the Whisker Biscuit, and it's mother circuit, the Big Muff. I have heard that there's an "American Woman" type pedal that supposed to come close to the Herzog, but I've never heard any samples of it. The thing is, not only does it have to have the sustain, it has to have the tube sound to it too, or it's just another distortion. I have come very close to this tone, running a DOD Big Fat Pig Distortion ito a Russian Big Muff, but it lacks the tube squash. I know Doug Hammond has a Firezog, but I believe it's tube based. Does anyone want to take this one on, or is it even possible?

[Skreddy]

I have thought for a very long time along the lines of over-saturating a small Radioshack telephone-coupling transformer to see if it would get anywhere close to a tube-amp squash.  I think it's about time to get on that idea.     The main thing, I assume, is to boost way too much signal into it, and then use a very lossy means of recovering the signal out of the other side, avoiding the buzziness, hopefully, that common resistive amp attenuators suffer.

[The Tone God]

The function is your friend:

Search criteria: herzog

http://www.elixant.com/~stompbox/smfforum/index.php?topic=22231.0

Andrew

[MartyMart]

Has anyone tried this ?
Wondering if it did work out .... !

MM.

[jmusser]

I didn't realize that I had actually asked about this before! Actually, I didn't ask about it perse' as being simulated, but it did come out during a discussion on the Hertzog in June of 2004. I'm with Marty though, do we know if this thing works before I got to the trouble of building it? It looks pretty labor intensive, but would be worth it for the tone if it did work. Also, how much hacking on the core lattices does a person need to do, and what turn ratio are we talking on the audio transformer? Is this a step up, or an isolation type where both primary and secondary are the same? As for the dummy loading, are you basically clipping the 10Ks onto the - and + of the speaker terminals? Where does the output go, back into the amp?

[Skreddy]

Well, reading RG's comments, it seems that hacking iron out of the core is not the way to go.  That would apparently only decrease the bass response (?).

He says the best way to saturate a core is to bias it with some DC (which would make it assymetrically clip).  So perhaps make a push-pull instead of single-ended design, into two really-small audio transformers, each biased with DC into non-linearity.

I'd experiment with something like 10:1 stepup transformers, but I'd run the signal (and DC) throught the 10 side (to really saturate the tiny core with lots of windings) and recover on the 1 side, with a variable L-pad attenuator.

Those are my thoughts as to where to get started.  I'm not planning to build something that's already been done, per se; though obviously this isn't a novel idea.  I'm glad to see others have thought this idea through, since I haven't.  Usually those ideas that just stew in the back of my mind for years turn out to be the best once I finally build them.  Perhaps because by that time I'm dedicated to some positive outcome and I do what it takes to make something good out of it. 

[jmusser]

Skreddy, is there anyway you could mark up the Fetzog schematic to show me exactly what you're talking about? (I've never heard of an L-Pad attenuator, for example) I understood some of what R.G. was saying, but I thought that maybe the Fetzog had actually been a working model, and at one time maybe the cuts had worked. Is the actual Fetzog circuit concept sound to start with, with the exception of the modified transformer core? I'd be willing to prototype it, if I knew that in the end, I'd have more than just a quiet pile of soldered components. If I half way understand what R.G. is saying, would the transformer actually need to be saturated by a DC source at a lower level than the AC signal of the output to get the tube squash sound?

[Skreddy]

Based on RG's comments, here's a quick schematic I came up with (copying various sources, unattributed, with apologies to original copyright holders...)
http://skreddypedals.com/circuits/SkreddZog.gif

Use at own risk.   

[jmusser]

Wow, Thanks for all the work! I believe I have most everything you show here on hand, except two transformers that are alike and are 10 to 1 ratio. This looks really interesting. I guess the only way to know if we're on our way to Bachman Land, is to build it.

[Skreddy]

Maybe 1:1 small audio xformers from RadioShack would work just fine.  And, since it calls for dual 386 power-amp chips (!), the bias current might even be redundant.    The only way to tell is just to build it.  This is all just cobbled together with of course no taste-testing on my part just yet.  The power-amp sections are of course copied directly out of the application notes for the 386 chip.  Check out other 386 amp schematics for more tips (Ruby, etc).

The preamp doesn't have any tone controls or even high cut or variable gain--nothing.  I have never built that design; it just looked like a generic preamp, so I copied and pasted.  Anything would work in there... BMP, FuzzFace, MuAmp, TubeScreamer, any number of the fine amp sims from ROG, etc., etc. 

Any common BJT transistors that you have laying around would work for the phase inverter section (2N5088, etc).

Also, I was just guessing with the attenuation and speaker-sim portions of the circuit (the stuff right after the transformers).  The 1k to ground followed by 100k in series forms the "L pad", and those values can of course be adjusted.  It seemed like those were safe values to use to bring a power circuit output down to line level.  But if you wanted to more closely simulate the saturation effect, maybe something more like two 16 ohm power resistors to ground instead of 1k to ground would be better.  Oh yeah; by the way!  hehe  That resistor to ground needs to be able to carry whatever the 386's current capacity.  So power resistor, eh?  I think I'll annotate my schematic with that idea right now...

The .015uf output cap followed by the mild lowpass filter 10k/.0033uf was just a guess at what might make a reasonable tone.  Maybe a bigger cap to ground, if it's too noisy or a 100k pot wired as a series resistor instead of the 10k--whatever.

As you can see, I did everything in a very 'vanilla' fashion to emphasize only the squash effect of over-saturating those little transformers, which was the whole point of this exercise.  A lot of work and parts just to test that one theory, but there it is. 

Let me know how your proto project goes and if you want any help with anything as you move along in your decision-making process about how to go about actually testing this idea.  If you actually do build it, you have my admiration and thanks.

Edit: Okay; I've just edited the schematic.  I specify 16 Ohm power resistors to ground after the transformers, and I've replaced the 100k resistors with 1k resistors, followed by a 100k pot in series (I got these values from the line-out section of a Mesa Boogie amp).

[Pushtone]

Here is a schem I have but I can not recall where it came from.
A google on RK Amplifiers didn't uncover much.
But it looks like what you are describing.

http://www3.telus.net/david65/bobzogg.pdf

Pushtone

[Skreddy]

Cool; thanks!  His is a speaker-load thingy, so it lacks all the amp stuff and just goes after the output of a cranked amp and presumably into the input of another amp or effects chain or whatever.  But it's nice that he includes the part number for the transformer, Radio Shack Audio Isolation Transformer (1:1) part # 273-1374

This transformer has a rolloff frequency of 5k, which is actually cool, since we're going for a squishy, liquidy, low-passed sound in this case.  Simply upgrade to a more audiophile unit if desired.

Again.. here's the schematic: http://skreddypedals.com/circuits/SkreddZog.gif

I'll update this file from time to time as ideas, feedback, and suggestions come in.

[christianbird]

Hello!

This post hasnt been added to in quite a while, but I'm really interested in this circuit. Has anyone tried anything similar?

I also posted in Suggestion to test: Distortion using transformer saturation (http://www.diystompboxes.com/smfforum/index.php?topic=40910.msg294489#msg294489)

I'm trying to get a clone / similar of the transformer distortion in the IVP Preamp.... check here for info http://projectivp.wordpress.com/

Thanks!
C

[pinkjimiphoton]

there's also the fetzog...i have a schem somewhere if you wanna see it.

[cloudscapes]

I thought this was gonna be about

[pinkjimiphoton]

[DougH]

Simulate a Hertzog?

Sorry, complete overkill...

If you're looking for the "American Woman" sound:

1. build any garden variety fuzz box
2. turn the tone control down on your guitar
3. go

The Hertzog is just a way of getting a line-out from an amp while leaving it properly loaded, then using that for whatever- going to a "slave" amp for more power, re-amping and getting the amp sound at a lower volume, and yeah... "fuzz" too. Nothing special about the Hertzog "sound" in and of itself- completely depends on how you use it.

[pinkjimiphoton]

doug, ya forgot to use your neck pickup there!! 

but i agree...the ruder the fuzz, the better.  :thu: