New project stuff maybe?

V

vigilante398

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One of the guitarists in my band uses a Victory V4 Countess for his main tone, and we always talked about having me trace it and build a clone that's smaller and more convenient, but nothing ever became of it. Well on tuesday night we had practice at my place, and we're practicing again here thursday (we went a month without practicing then decided to book 3 gigs a few days apart), so his rig would be spending 48 hours or so in my basement.

I cracked it open a couple hours after he left, and finished the trace wednesday morning. I was initially intrigued by their use of unusual tubes (EC900 single triode and CV4014 pentodes), but upon finishing the trace the circuit is actually disappointingly simple. My schematic is obviously unverified, but my limited knowledge of tube circuits is enough to know that what I've drawn will work, so I'm relatively confident it's correct.

The problem is, now that I'm finished tracing and not seeing anything new and exciting in the circuit, I have zero motivation to do a layout :confused:

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Betty Wont said:
I’m intrigued but at this point if I’m putting 4 tubes in a pedal, it had better deliver Uberschall gain.
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Exactly. It's not a bad sounding pedal and it can get a healthy level of gain, I would say more or less on-par with Black Eye, but I think it would make more sense to redesign it for dual triodes instead of all these single-stage tubes. They're not doing anything super complicated with the pentodes anyway, they could easily be replaced with triode stages and get pretty well the same sound.

I'm all for trying something new and using pentodes as preamp tubes (EF86 for example has very cool characteristics that make it unique sounding), but the amount of power required for running 4 tubes is considerable, and you could easily get the same (or more) amount of gain with a pair of 12AX7.

With regards to mu (amplification factor), the EC900 and CV4014 all have a mu of 75, so you have 4x 75-mu gainstages. 12AX7 has a mu of 100, so Black Eye has 4x 100-mu gainstages. A pair of 5751 (mu of 70) would get you in the same ballpark as the Countess and save you a load of power.
 
Betty Wont said:
I’m intrigued but at this point if I’m putting 4 tubes in a pedal, it had better deliver Uberschall gain.
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I'm not saying it's going to happen, but your comment made me look up the Uberschall schematic. My brain immediately went to Hammond 1590D, 12V power supply, current draw would probably be around 600-700mA operating. You need 5 stages for the OD channel, which means use 3x 12AX7 and you can do a clean channel too, you could even do relay switching for the channels. If you used a beefy enough supply you could probably get away with adding in a 4th tube and keeping the FX loop in there too, the 1590D has enough real estate to add in a couple more jacks for a loop. NE555-based HV power supply can supply around 15mA at 250V, but a 12AX7 only needs 2.4mA per tube (1.2mA per triode) so you're realistically covered for up to 5 tubes.

Somebody (not necessarily me) could make it work.
 
vigilante398 said:
I'm not saying it's going to happen, but your comment made me look up the Uberschall schematic. My brain immediately went to Hammond 1590D, 12V power supply, current draw would probably be around 600-700mA operating. You need 5 stages for the OD channel, which means use 3x 12AX7 and you can do a clean channel too, you could even do relay switching for the channels. If you used a beefy enough supply you could probably get away with adding in a 4th tube and keeping the FX loop in there too, the 1590D has enough real estate to add in a couple more jacks for a loop. NE555-based HV power supply can supply around 15mA at 250V, but a 12AX7 only needs 2.4mA per tube (1.2mA per triode) so you're realistically covered for up to 5 tubes.

Somebody (not necessarily me) could make it work.
Click to expand...
I’m looking around at a whole bunch of faces looking right at you, man. 😂
 
vigilante398 said:
I'm not saying it's going to happen, but your comment made me look up the Uberschall schematic. My brain immediately went to Hammond 1590D, 12V power supply, current draw would probably be around 600-700mA operating. You need 5 stages for the OD channel, which means use 3x 12AX7 and you can do a clean channel too, you could even do relay switching for the channels. If you used a beefy enough supply you could probably get away with adding in a 4th tube and keeping the FX loop in there too, the 1590D has enough real estate to add in a couple more jacks for a loop. NE555-based HV power supply can supply around 15mA at 250V, but a 12AX7 only needs 2.4mA per tube (1.2mA per triode) so you're realistically covered for up to 5 tubes.

Somebody (not necessarily me) could make it work.
Click to expand...
Don't the higher gain amps need upwards of 300-350V to sound right? I'm definitely no expert, but I've seen a few comments from techs who say part of the modern high gain "magic sauce" was higher voltages.

(I'm sure it will still sound great at 230V, but if we're shooting, shoot to kill!)
 
So far most the high gain pedals i have tried are underwhelming. The amptweaker tight metal is the best one ive tried so far. godcity socialist is a close second. followed by friedman be-od. ive built some other high gains stuff i cant remember off the top of my head.
 
Laundryroom David said:
I’m looking around at a whole bunch of faces looking right at you, man. 😂
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Weird, even after I specifically said "not necessarily me"? :unsure:

szukalski said:
Don't the higher gain amps need upwards of 300-350V to sound right? I'm definitely no expert, but I've seen a few comments from techs who say part of the modern high gain "magic sauce" was higher voltages.

(I'm sure it will still sound great at 230V, but if we're shooting, shoot to kill!)
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I mean maybe. The Uberschall schematic I'm looking at doesn't have voltages labeled, but the SLO schematic I used when I built mine says around 350V for B+ in the preamp. Still not a problem, I regularly coax 350V out of the NE555-based SMPS for my production builds, doesn't take much modification.
 
Super quick update on this:

I don't think I have the free time that would be required to do a good job at an Uberschall preamp project, but I have a friend at work (also an EE and also a guitarist) that has talked about doing more electronics stuff outside of work that has expressed interest in taking a swing at a PCB layout. It was a quick conversation on friday morning and I haven't talked to him since, but I'll touch base with him Monday morning and see how serious he was about it.

But yeah I'm just not really excited about the Victory preamp, and it doesn't sound like anyone else really is either.
 
Bricksnbeatles said:
What *would* be exciting is a Garnet Herzog pedal ;)

View attachment 52474
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I mean it's basically a modified Champ with a dummy load, right? I won't say it's impossible to get that into a pedal, engineers don't like being told anything is impossible, but here's a couple reasons why it would be difficult:
  • Power: 6V6 takes a lot of current, both on the heater (6.3V 450mA steady state) and on the plate (315V 34mA). The NE555-based HV supply I use maxes out around 15mA, so another method would be needed to get the high voltage rail.
  • Heat: this goes along with power. I put vents in my enclosures largely for decoration, preamp tubes don't get hot enough to really require ventilation. Once you throw that 6V6 in there though things change. Power tubes will get HOT. If I were to design a stompbox-sized unit like this for commercial production I would definitely put active cooling (at least one fan) into it.
  • Transformer: there are ways to get around a power transformer (like an SMPS), but it's hard to get around using an output transformer. You would need to find a transformer big enough to handle the power but small enough to fit inside a pedal chassis (unless you want to mount it on the top, which I personally don't like doing with pedals).
  • Size: between the 12AX7, 6V6, and output transformer, you've got a lot of big things going on. You're literally talking about building a stompbox-sized Champ. Not impossible, but not easy. If you could find an SMPS beefy enough to handle the HV so you don't need a power transformer I would still probably look at something like a Hammond 1590D at a bare minimum. If you're keeping true to the original and using a power transformer, you'll be looking at going even bigger.
I'll repeat that it's not impossible, but it's equivalent to an amp build, so it's not trivial. The easiest method would probably be to get a cheap Champ kit and modify it to be a Herzog.
 
vigilante398 said:
I mean it's basically a modified Champ with a dummy load, right? I won't say it's impossible to get that into a pedal, engineers don't like being told anything is impossible, but here's a couple reasons why it would be difficult:
  • Power: 6V6 takes a lot of current, both on the heater (6.3V 450mA steady state) and on the plate (315V 34mA). The NE555-based HV supply I use maxes out around 15mA, so another method would be needed to get the high voltage rail.
  • Heat: this goes along with power. I put vents in my enclosures largely for decoration, preamp tubes don't get hot enough to really require ventilation. Once you throw that 6V6 in there though things change. Power tubes will get HOT. If I were to design a stompbox-sized unit like this for commercial production I would definitely put active cooling (at least one fan) into it.
  • Transformer: there are ways to get around a power transformer (like an SMPS), but it's hard to get around using an output transformer. You would need to find a transformer big enough to handle the power but small enough to fit inside a pedal chassis (unless you want to mount it on the top, which I personally don't like doing with pedals).
  • Size: between the 12AX7, 6V6, and output transformer, you've got a lot of big things going on. You're literally talking about building a stompbox-sized Champ. Not impossible, but not easy. If you could find an SMPS beefy enough to handle the HV so you don't need a power transformer I would still probably look at something like a Hammond 1590D at a bare minimum. If you're keeping true to the original and using a power transformer, you'll be looking at going even bigger.
I'll repeat that it's not impossible, but it's equivalent to an amp build, so it's not trivial. The easiest method would probably be to get a cheap Champ kit and modify it to be a Herzog.
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Yup— that’s essentially all it is. Champ with a dummy load, as you said.
Figured the transformer would likely have to be externally mounted unless modern technology has created much more compact output transformers than I was aware of. Didn’t think about the current limit of the 555 supply, which is what made me think it could be done without a prohibitively large enclosure (I was thinking a vertical 1590D might work, with the transformer being mounted up near the top so it’s far from the footswitch). Figured a combination of a heatsink and a small fan or thermoelectric cooler might get it so it’s not necessary running at an ideal temperature, but at least not hot enough to cause burns from touching the exterior of the enclosure.
Definitely makes sense why it wouldn’t likely be as worthwhile as just building an actual champ.

Not necessarily a suggestion, as much as myself thinking out loud, but I wonder if, just as the lab rat is a combination of a tube input section and typical op amp clipping section, would it be a worthwhile experiment to do the 12ax7 preamp section of the Herzog followed by either a very low-wattage class A solid state circuit (though the power amp saturation is sort of the key to the sound of the Herzog, and a solid state power amp wouldn’t be all that similar) or (I believe I’ve seen these before) one of the mosfet-based tube-power amp emulation circuits, or even an LM368-based circuit like 1/2 of an Acapulco gold?
 
What if...

You used something like
6111
6112
6148
6021

A Sub-miniature tubed Herzog, like the SuperFly Amp

or, yeah, a Countess based on sub-miniatures...
 
Feral Feline said:
What if...

You used something like
6111
6112
6148
6021

A Sub-miniature tubed Herzog, like the SuperFly Amp

or, yeah, a Countess based on sub-miniatures...
Click to expand...
I've sworn off subminis after using 6N21B and 6N17B-V for years, I won't design for them anymore.

But honestly if you're not picky about staying true to the original you could use a 12AX7 for the preamp tube and 12AU7 for the power tube in self-split like the Firefly. The Hammond 125A output transformer is small enough to fit into a 1590X, and you could get away with a 1W dummy load. So that's an option.

I wouldn't want to do a Countess based on subminis, I would be much more likely to use a pair of 12AX7 or 5751 if I were to take a swing at it.
 
Talked to my buddy Jeff about the Uberschall this morning, he said he's serious about taking a swing at it. We're going to talk details over lunch today and he'll get started on the layout later. He uses the same CAD tool I do so it will be easy for me to give him my parts libraries and board outlines to get him going.
 
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