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Discussion Starter · #1 ·
I'm trying to convert a 5 watt Garnet Banshee Bass into something a little more 'herzog'. I figured it would be a pretty good candidate for a 'bass-herzog' as a 5watt bass amp is a little silly, it has the same tube compliment and PT as a herzog, and the layout looks very similar aside from the EQ.

I'm very new to amps (but have done lots of guitar electronics work), and this is the first project I've undertaken trying to use schematics instead of diagrams. Having very little idea about what-does-what, I've mashed up a couple of schematics found online. I was hoping someone more knowledgeable than myself could let me know if it looks like a Herzog or bluesmokedeathmachine. My sources are all here

Here's what I've drawn from those:


Any help, tip, or suggestion is appreciated
 

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Seems like early version Herzog vs later (which had no speaker out).

Personally I would worry a bit about running parallel speaker and line outs; make that switchable (one or the other) or use a second output tranny to isolate them (I know Garnet originally did it this way, as drawn above, but he did change that later; there was probably a reason for that since a jack and some wire is hardly much additional cost). Those are small and cheap - Hammond should still have similar ones available (the original is a Hammond). ... or better still replace with one that has 2 secondaries (not sure if such a beast exists, as regards power handling and requisite turns ratio).

I'd also change the dummy load power resistor on the speaker jack to 10watt just to be safe (again, as Garnet later did), and 8 ohm which nowadays should not be any harder to find than 10 (later Herzogs have 6 Ohm, with the same OT as this here on the schem ; not sure what the earlier HZogs w 10Ohm dummy used; likely the same but dunno). That resistor in series with the 1 meg pot/cascaded amp input, will show just a tad less to the OT than what it's value is (so like 7.8 - 7.9 if the dummy load is 8).

Final note: I am by no means an expert either. You want JBWelder to chime in here.
 

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Discussion Starter · #3 ·
thanks for the input! I thought the switching jack on the speaker out was taking care of speaker/lineout or is that just a 'it won't blow up if not plugged into a speaker' switch (and still bad to run into speaker AND use as an effect at the same time? man... electricity is hard :)
 

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You can run both, but they interact. The dummy load is there (and should be on all tube amps, where feasible) to protect against no load at all. In this case it also helps with stabilizing the load seen by the OT when a speaker is plugged in vs line output (or both) but it does not switch between them in the sense of preventing one or the other from being active (the switch is actuated by inserting a jack into the speaker out, and does not cut off signal to the line output, which is in front of it).... you could make the speaker jack work that way by moving the lead connected to the level pot from just after the OT to the shorted tab on the switch (parallel to that 10Ohm resistor) - that way, using a speaker disables the line out
 

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I may be ex- something or other, but I wouldn't claim any more than that. :D
It looks ok to go, no signs of impending disaster. Agree with bigger power resistor for the load.
See how it sounds, it's fairly simple to change over other things to match the herzog later if you find anything lacking. (coupling cap values, plate & cathode resistor values on preamp tube) One of the first things to try would be to see if you want the NFB loop connected or not. Just disconnect one end of the 2700 ohm feedback resistor coming off the output transformer. See if you like it better with the loop in or out.

P.S. There is a typo on the Banshee schematic, won't matter much unless you were building one or the original resistor got burnt beyond recognition. The resistor between the 315V and 295V nodes of the power supply is 10K (10,000 ohm), not 10,000K (10meg).
 

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Interesting timing on this thread as I had just posted the following in another thread about a few small mods I made to my Gnome (same amp as the banshee but with tremolo).

Today I ran the modded Gnome into my attenuator (set to load) and then from the attenuator's line out into the front of my amp (Bass Master). I am willing to bet that the Garnet Herzog is basically a Gnome with a bypassed tone section, removed NFB loop, running into a dummy load. Not sure if that is exactly what is going on in the Herzog, but boy does it sound similar.

TG
 

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Discussion Starter · #7 ·
Thanks for sharing your knowledge folks. A 10watt/8ohm resistor is on the way, and a quick googling of negative feedback loops was very insightful, sounds like that will probably go. It's great to have these little functionalities of sections pointed out with such a sparse circuit... those moments of borderline comprehension are awesome :)
 

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You can make the NFB loop switchable very easily. In solid state amps and pedals it's a common thing to do as a alt tonal option.
 

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Discussion Starter · #10 ·
Well I'll be darned! Plugged it in for a quick spin over the weekend and almost immediately went back and put the NFB loop on a switch. Played around for about a half hour, no smoke, no blown tubes or fuses...so I guess it works! Thanks all! I'm still confused why the amp I'm feeding it into isn't ablaze, so much more signal coming in....black magic?

Now that it's up and running, I would like to coax a little more gain/dirt/distortion out of it. I've been reading over TraynorGarnets thread here and on the Yahoogarnetgroup and it sounds like swapping the plate (& cathode?) resistors/caps is my next stop , as suggested by JBWelder as well. Soooo.... can I just toss 220k resistors with .47uf caps as found on the later hzog safely? (on the diagram I posted @ 100k/.002uf and 100k/.01uf)? Replies to TG on the subject looked far more ...in-depth.... Any other thoughts on ramping this up from overdrive to fuzz?

I'm also tempted to add an EQ bypass on a push/pull as well, but do like having access to a little shaping. A foot switch would be handy too, but I find the hzog switching dumbfounding.
 

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Discussion Starter · #12 ·
probably won't get to it till the new year, but I expect between that and/or resistor swaps it should get pretty nasty :)
 
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