I am building something ambitious

Granny Gremlin · February 02, 2018, 08:24:50 AM

At least 13.

I am building one of these:

Which is basically a Champ with a line out to feed another amp; an OD preamp sort of thing (but can still use it as an amp too). The main change I am making is adding the infamous (up here anyway) Stinger fuzz circuit (as found on the larger Garnet amps in the early period) ... and relay switching for general bypass as well as the Stinger.

Queue Uwe with the Randy Bachman jokes.

Highlander · February 02, 2018, 02:07:39 PM

What Randy Bachman jokes...?

doombass · February 02, 2018, 03:12:23 PM

We don't need Uwe to make any jokes (though I love his wits) when Randy himself is being funny enough for himself sharing his . Out of curiousity I did some read up on Garnet and its Randy Bachman history quoted by the man himself (which is entertaining if you know the technical side of a tube output stage that is):

Gar and I developed this unit together back in '65-'66. Growing up playing violin, I loved the sustain, especially of a viola or cello. So early on in the mid '60's, I found out that by plugging a small amplifier into a bigger amplifier, I could get this sound. Now I was taking the power out, which normally would go to the speaker and plugging it into the input of another amp. The result, for a few short minutes was a cool, great new sustained sound. Gar Gillies had a tv/radio repair shop, was a cool musician, and I wasn't embarrassed to take in my amps, which were literally burned by the power misuse; fried, to say the least. Gar asked what the heck I was doing, and when I told him, he said, you're insane to do this, its very dangerous. So he offered to help me do it a safer and less destructive way. Gar proceeded to build me a tube pre-amp, which when put into another amp, got me the desired sound.

I've always been struck by the guitar sound of American Woman but never investigated what equipment was involved making it. This makes your project even cooler Jake.

Granny Gremlin · February 02, 2018, 04:24:52 PM

Yeah... I've only ever actually heard that story as told by Gar Gillies; basicially the same but with more explatives.

Anyway, I have learned that power tube (tetrode/pentode) distortion is what I like best - e.g. all my favorite mic preamps have a pentode in them, not just the same old 12A whatevers. Also the key is not driving the snot out of a triode but overdriving multiple cascaded gain stages. Tet/Pentodes get you there in fewer stages than triodes - dunno why, they just do.

The Herzog, being the Champ circuit, has a 6V6 tetrode in it (and you can dime it - the line has an attenuator). Adding the Stinger fuzz puts another triode as well as another pentode (6AN8 tube, which I love the sound of - I have other gear using those) in the circuit so I am really thinking this will be the one; my ultimate dirt machine.

clankenstein · February 02, 2018, 09:17:23 PM

Most interesting.The relay switching sounds like a good idea too.When i lived in London i ran the line(attenuated speaker)output of my laney lc15r in to a jcm800 marshall,That was a great guitar sound!

Granny Gremlin · March 03, 2018, 08:29:16 AM

So I have been distracted from this project because I managed to score a Garnet Sessionman PA head (the same model I sold to buy my Sunn 1200s when I needed more power). That was a great amp and it's been sitting in this local junk shop for ages, rusted to shit. I recently learned that the shop owner's #1 trade option is old tubes (doesn't care if used); he often buys old amps to pull the tubes and then flips the chassis. So when I found the set of 70s GE 6550As that were in my Sunn, replaced when I had an issue that turned out to be the screen resistor on one of them and since tested as OK) I figured I'd give it a shot. It helped that I had some Karma at their store: the second last time I was there they were all in the basement but had left the door open with a nice Traynoy YBNA-3 Custom Special standing on the floor right there. I came in and hollered but they didn't hear me, so I spent a good half hour poking around before I hollered again and they came up. Came back fro that Traynor and they had sold it on me; joked about how I shoulda just walked out with it the other time.

Anyway, after testing the thing worked (soooooo rusty) we did a straight trade - the tubes for the amp (unloaded; one of the power tubes was buggered anyway - all cloudy inside; the preamp tubes are all Garnet branded Mullards).

Been a bit busy cleaning this one up and dealing with the 2 prong cord. Long story short it looks like all original wiring inside and the part date codes go back to before the official start of production so I may have lucked in to the very first one; at the very least looks like made by Gar himself vs one of his, at the time, 'factory workers.'

.... aaaaaaand just today an actual Garnet Herzog (though granted the 90s/00s reissue; still made by Gar himself) comes up for sale at a very reasonable price (if anyone is interested I can link you; no relation); IIRC I've seen them sell for not quite double this person's ask.

Dave W · March 03, 2018, 10:18:42 AM

Sounds like you got the better deal out of the trade.

Granny Gremlin · March 03, 2018, 11:13:23 AM

I think so! Dude probably woudn't have agreed if it wasn't for me not stealing that Traynor (and being a regular).

Granny Gremlin · June 29, 2021, 10:46:55 AM

OK, I know it's been ages, but between this project being a tad ambitious for my skill level (first tube build and I had to just go mod the circuit to make things even harder; learned so much tho) and you know, everything, I finally got it working today.

So, as mentioned previously, it's basically a Garnet Herzog (modified Fender Champ), but Champier, and with the Garnet "Stinger" fuzz tacked on. Can be used as a stand alone amp (8 ohm out) or as a preamp in front of another amp (dummy load on the speaker out). Feeling a little Malcolm Young today as I did a quickie demo (will do some more detailed ones later, including with bass).

The hangup for the last year or so was squealing oscillations in the 6AN8 fuzz tube. Eventually added some decoupling for that tube specifically (don't think that did it, but probably a good idea) and threw a plate load resistor bypass cap on the first stage (pentode half feeds the triode half) to tame the high end squeal.

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Granny Gremlin · October 07, 2021, 04:46:28 PM

Finally done. 4.5 years but I feel better seeing Scott's bass build thread.

Kinda gunmetal grey transparent plexi front panel (had some kicking about, bit scratched but whatever - never doing that again; what a pain) and a white doghair finish that's hard to see in pics (unfortunately it does highlight the mitre joints). Cab is solid poplar (which people shit on but I really like).

I am pleased to report that it is rather aptly named, but then there's also the bright and brighter settings. Now gonna build another in a floor box version, minus a few things (like the tube rectifier - I don't think it does anything useful vs diodes in a 5 watt single ended amp, but this was an experience in self education, and normal relays vs the industrial octal plug in ones here). The Negative feedback defeat switch is definitely a worthwhile option.

BTL · October 07, 2021, 09:40:47 PM

That turned out great, congratulations!

Dave W · October 07, 2021, 11:24:47 PM

It's beautiful. Hope it does what you designed it to do.

amptech · October 08, 2021, 12:24:58 AM

Nice👍

morrow · October 08, 2021, 05:45:12 AM

That looks really good !

Granny Gremlin · October 08, 2021, 07:33:40 AM

Thanks guys!

Quote from: Dave W on October 07, 2021, 11:24:47 PM
It's beautiful. Hope it does what you designed it to do.

It does! It can get dark and doomy through brighter than I care for.

The fuzz is great but can fizz out a bit at the top of the dime depending on yer pickups. with the dull cap (plate load bypass on the fuzz tube) I put in to tame the oscillation it's not nearly as unwieldly as old school hoser rockers say about version 1 Garnet Stingers. If the gain is dimed, turning on the fuzz takes it to that next level where it's not more distortion so much as compression and evening things out (and top end maybe, depending on normal path tone vs fuzz tone settings).

I was surprised how much the NFB switch being engaged cleans the thing up (still get dirt but less for the same setting). I haven't played with that very much yet, but that part of it was immediately obvious even at lower gain settings.

A great learning experience - for example, at least in lower powered single ended amps, tube rectification is a waste of parts and space. I'm going to take it to the studio to see if I can push it to sag but I don't think it will.