Low Heater Voltage on Herzog Clone

[diagrammatiks]

like a said before man there's not that much going on in the circuit.

All it is a dummy load attached at the output and a tapped direct out.

the preamp circuit doesn't matter.

all that's different between the two versions you posted is how the volume and tone stack function.

all the information is available in merlin. it'll help a lot to learn what each piece of the circuit is doing.

[The New Steve H]

I studied up on this thing and decided to put smaller coupling caps in. I removed two .047uFs and replaced them with .022uF. The amp seems less dark, so I guess this was the right move.

It took about 15 minutes to make a stompbox for it, so now I have a Herzog footswitch on my board.

I am currently using a 12AY7 preamp tube. I am not getting oscillation with it, the way I did with the 12AX7. The sound is also sweeter and less grainy.

The sound is still what I expected. I'm getting plenty of sustain and gain, but the tone reminds me of a 1970s synthesizer. It reminds me of the opening licks from Norman Greenbaum's "Spirit in the Sky."

[The New Steve H]

Nice view of the new baby, with knobs installed. Now that it works it will have to have a cabinet.

[Structo]

So can you get American Woman tones out of it yet?

[The New Steve H]

I have no idea whether I can do that. So far it's a little off. I am going to try to record some of the sounds.

I don't know how the amp (not the Herzog) was set when that tune was recorded. There are a lot of variables at work, starting with the wacky schematics and my dubious wiring skills, and the amp and Herzog settings just add to the mix.

I am not sure my incompetence caused the oscillation, which is definitely in the preamp, since it happens regardless of the output volume setting. It seems like the 12AX7 had way too much gain, plain and simple.

I see that the TUT Herzog has a 100K resistor on the V1b plate, where the schematic I used has 220k. Wondering if I should change that. I don't know how much the big resistor increases the gain, but I obviously have more than I need. Or maybe I should put a bigger resistor in there and keep the 12AY7, so I can get enough gain to break it up, without going into spastic conniptions.

Now that I've built this thing, I am tempted to build a tiny class AB amp similar to the Bassman and Herzogify it. I wanted to do a little amp like that anyway, and adding Herzog capability would be very little work. I think the tone would be a lot sweeter.

[The New Steve H]

I'm going to take it to church and let the guitarists fool with it. I had to put some kind of base on it, but I didn't have time to make a cabinet. Thank God for cable ties.

[renshen1957]

I have no idea whether I can do that. So far it's a little off. I am going to try to record some of the sounds.

I don't know how the second amp (not the Herzog) was set when that tune was recorded. There are a lot of variables at work, starting with the wacky schematics and my dubious wiring skills, and the amp and Herzog settings just add to the mix.

I am not sure my incompetence caused the oscillation, which is definitely in the preamp, since it happens regardless of the output volume setting. It seems like the 12AX7 had way too much gain, plain and simple.

I see that the TUT Herzog has a 100K resistor on the V1b plate, where the schematic I used has 220k. Wondering if I should change that. I don't know how much the big resistor increases the gain, but I obviously have more than I need. Or maybe I should put a bigger resistor in there and keep the 12AY7, so I can get enough gain to break it up, without going into spastic conniptions.

Now that I've built this thing, I am tempted to build a tiny class AB amp similar to the Bassman and Herzogify it. I wanted to do a little amp like that anyway, and adding Herzog capability would be very little work. I think the tone would be a lot sweeter.

Hi New Steve,

The Herzog is basically a Champ SE amp without the speaker, without rectifier tube, or tone stack, pretty simple.

As to oscillation, you might want to investigate the chapter 2 in TUT3, making the right connections, especially decoupling, galactic grounds, grounding, etc.

You might find it necessary to add a 10k grid stop to the V1B stage, sometimes grid rectification from too much gain can make a flatulent sound (some call it sticky or farty) in cascaded gain stages. I add these in any amp I make, even if not on the original schematic.

I haven't seen a picture of your circuit board. It's best to make as much space between the components as possible, this reduces parasitic capicitance.

The layout in TUT 3 Herzog Chapter (which since you referenced you must have access to) is a good starting point.

The cap attached the the V1A plate is .022 in the original RBH, later versions use .047 but different cathode resistors (more below). The plate resistor on V1B is 100k in the original R B Herzog, later versions have 220K . KOC has the original values (yet his version of the amp is an improved "Super Stock" version). Cathode resistors are 1k5 on original R G H, later 2k7. The 220K resistor plate would have a different set of brighter harmonic components, compared to say the 100K resistor. As to Cathode Resistors and Cathode Caps, too much to comment on, trust your ears.

The later version does not have a cap across the Primary of the SE OT to stop ringing.

As to the "American Woman" tone, it would help if the second amp in the Chain was also a Garnet Amp or amp that was designed to be played loud and clean (like most Canandian Amps). Garnet amps usually had a 12au7 in the PI position (and previously it was a 6SL7).

In context, the 12AX7 is a high mu (100 amplification) tube. However, due to design and variances of assembly, cathode chemicals, construction there are high, medium, and lower gain varieties of the Tube.

What brand is your 12AX7 you tried?

Certain tubes manufacturers seem to favor the higher gain varieties than others. To my experience all the Chinese tubes are all higher gain (and harsher sounding, even after breaking in).

Russian and Slovak offerings vary from medium to high gain tube depending on the tube, AES offers for sale Fenders version of the Sovtek 12AX7C which is in their (AES, CE, amplified parts tables) advertising as a low gain tube

Original NOS 12AX7 tubes were by and large for comparasion, medium gain varieties, frequently used in Hi-Fi amps, therefore all around tubes. These were the tubes Gar Gillies designed the Herzog around (and not have it blow up; Gar also wanted to stop Randy's previous experiments with Amp Chaining from electrocuting the Guitar slinger).

As to the 12AX7, New Steve, try some tube rolling.

The original Garnet lableled 12Ax7 tubes were relabled Mullard tubes (medium gain). Mullards (even the used ones) have been sifted through over the last 30 years) between Audiophiles and Marshall & Vox owners.

You might try medium gain varieties of the 12Ax7s such as JJ's 12AX7-S (but not the gold pin version high gain tube) or the Sovtek 12AX7WA/Sunrise 12AX 7(same oversized tube, might not fit in a Chinese tube shield, but will fit in US and Korean sockets) if it will fit.

I would avoid TAD, Ruby, or Groove Tubes, these are Chinese 12AX7 which are high Gain tubes and too many ears, harsh.

A 5751 (NOS) might be the ticket, its Amplification is 70 compared to the 12AX7's 100 or the 12AY7 40 and possibly what you are looking for.

Using a lower gain tube (5751, 12AT7, 12AY7, or 12AU7) will give you a new/different tonal palette, but it won't be the solution to the oscillation problem. That has more to do with lead dress, the capacitors in the B+ power supply, or circuit design.

Best Regards,

Steve

PS If you are considering building a push-pull amp, read the Chain Chapter that follows the Herzog in TUT 3.

[The New Steve H]

Thanks for all the help.

I took this thing to church, and the guitarists tried it with a Vox AC30CC2. The effect was really weak! Needless to say, they didn't like it.

With my 5F6A clone, the effect is very pronounced. It sounds like a brass instrument, which I did not expect, but it's a pleasant and unique kind of distortion. I have no idea why it was so lame with the Vox. I hate that amp. To me, it sounds like a Fender wrapped in blankets.

I believe all of my 12AX7s are JJs. They sound scratchy to me.

I don't have a photo of the board, but it's about 2" wide, and the components go across it. They are about 1/2" apart.

I didn't get access to the TUT schematic until this one was nearly done.

Here's the idea I have rolling around in my head. I think it would be interesting to build an amp similar to a 5f6A, with lower wattage, rigged up for Herzog use. Now that I think about it, three 12AY7s and two EL84s might be an interesting combination.

So far, I haven't heard a Class A amp I really liked. The Bassman, on the other hand, is like having cool honey poured into your ears.

[bcmatt]

PS If you are considering building a push-pull amp, read the Chain Chapter that follows the Herzog in TUT 3.

I'd be interested to know what sorts of things you are referring to in that chapter since I don't have that book, but I am thinking of this sort of idea.

I've been watching carefully and have been tempted by the Herzog idea because I have a couple of 70s Traynor YGL-3A heads that are big clean amps but quite nice sounding.

At the same time, I am dirt poor but can't resist the urge to build.

Since I have about a 30 watt OT with 4, 8, and 16 ohms secondaries and a 4k3 CT primary, I feel like it would be wrong to not use it for something. I don't have a 5e3, and figure that would be a nice amp to have (or sell off quickly in a starvation situation), I'm wondering about building a Tweed Deluxe with it. I guess it would be like a 8K6 primaried OT with 2, 4 and 8 ohm secondaries (am I right here?). I figure that would be close enough for a sort of 5E3 OT?

So, what I am wondering about, is if I were to give the whole Herzog option off the 4 ohm tap (originally the 8 ohm tap), could I use 3x 20 ohm 10 watt wirewound cement power resisters in parallel (6.7 ohm total rated for 30 watts) for the whole load thing?
http://www.tubesandmore.com/scripts/fox ... item=R-R20
that should be rated to handle 30 watts, right? Would that be above spec enough for a 5e3 type amp?

I figure a 5e3 (with way oversized OT) should be a little more useful as an amp on its own, as well as an interesting candidate as something driving a clean amp.... Thoughts?

[diagrammatiks]

if you make the dummy load i'd suggest 2 to 4 times the output power of the amp.

[bcmatt]

if you make the dummy load i'd suggest 2 to 4 times the output power of the amp.

Ok, so maybe 4x 10 watt resisters in parallel then. 10 watters are the biggest I can find at AES (where I'd order everything else I need).

rated 40 watt dummy load for a 12 watt amp should be safe I guess.

[diagrammatiks]

steven,

I can't believe I just remembered this.

do a search for the marshall class 5 schematic.

they implemented almost the same idea on the output with a 15R 25w resistor.

[The New Steve H]

Will look. Thanks.

[Reeltarded]

Are you using speaker wire for a line level output to an amplifier?

[The New Steve H]

Cheesy Guitar Center guitar cable.