Low Heater Voltage on Herzog Clone

[The New Steve H]

It runs!

I stuck a 250pF capacitor where I had the 470uF, and immediately, I saw a huge signal on the scope. Clearly, the giant capacitor was the problem.

I took the Herzog into another room and hooked it up to a guitar, a speaker, and a crappy Crate solid state amp. I hooked the speaker up through the 8 ohm speaker output, and I used the effect output for the amp.

The mute works, so that's exciting. The volume control (the 1M pot by V1) works fine, too. The amp makes a bizarre rustling sound when it comes on, but it only lasts a second. I thought it was going into oscillation, but that was not the case.

The speaker I used is a 10" Ragin' Cajun.

I only had a few minutes to check it out, due to the hour, but it definitely functions as an amp. The sound was pleasant and compressed, with a high but acceptable level of AC hum. The only problem is that there is no top end. I really couldn't hear details like string noise. It is entirely possible that I did something to cause this, but I am thinking it may be part of the design, since it's primarily an effect. It has a "bright" control; maybe this is the reason?

The bottom end is more authoritative than I expected.

There is something going on with the effect part. There is a short down there somewhere. I saw a flash while I was fooling with it. I shut it down, and I'll figure that out tomorrow. It doesn't seem to be damaged, and it didn't quit working.

I'm hoping I'll get the final bugs out of it tomorrow, and then I can try to come up with some kind of drawing that makes sense, in case someone else wants to build one in the future.

If I can get it to produce higher frequencies when used as an amp, it ought to be great.

[The New Steve H]

I have been fooling with the Herzog some more. It looks like I underestimated the brightness because the Crate amp was unbelievably bad, and I think the cable I used for the Herzog speaker output dulled the sound. It's still not bright, but not as bad as I thought.

It has less sustain than I thought it would.

I investigated the funny sound I heard last time. I think the amp is oscillating and making a loud, annoying, low-pitched sound, but it only happens when there is nothing in the input jack. Since I don't plan to use it without input, I don't think this is a big deal, but if any of you know better than I do, please let me know.

The mute works.

Getting some shorting at the plate pin on the output tube; will get it fixed so I don't burn the house down.

I think it was stupid to put in a footswitch jack. It would be much smarter to hardwire a footswitch and make a place for it inside the cabinet. This would be my suggestion for anyone else who builds one. After all, what good is an SPST footswitch that isn't dedicated? You would probably lose it.

Funny thing about the relay: it made a tiny buzzing sound when I first got it, but now it's silent.

The Herzog version I now have works, so I can try to create a drawing for other people. I'm sure my layout could use improvement.

[The New Steve H]

More notes for anyone who builds one of these.

Experienced builders may find this pretty obvious. The pot by the 12AX7 is the main volume, and it applies when using the Herzog as an effect (through the effect output) and when using it as an amp (through the speaker output). The pot by the OT controls only the effect output.

I left the filament center tap grounded, and the amp works fine. This is not what the schematic says to do, but it works. When you remove it, you get strange-looking AC through the relay coil.

I used a three-way switch on the speaker output, possibly due to a brainfart. I used it to switch between the 4-ohm OT output, the 8-ohm OT output, and...nothing This was stupid, because it's easy to leave the switch in the middle position accidentally so the OT is not connected. The jack switch turns the resistor on automatically, so all you need is a switch that selects 4-ohm or 8-ohm output. I leave it on 8, figuring that approximates the 10-ohm resistor.

The footswitch and/or manual switch cut out the amp very cleanly. I am no expert, but it sounds like a complete bypass.

Perhaps someone could advise me on making the amp brighter. The bright switch works, but in my opinion, the Herzog is still a little dark when used as an amp. It has an interesting, spanky sort of sound to it, but it could use more highs.

I found an online bypass cap calculator (http://www.ampbooks.com/home/amplifier- ... capacitor/) and fiddled with it. Wondering if I could rig up smaller bypass caps that could be switched in and out. I don't want to change the sound of the effect, so I would want the option of using the original caps.

[bcmatt]

Perhaps someone could advise me on making the amp brighter. The bright switch works, but in my opinion, the Herzog is still a little dark when used as an amp. It has an interesting, spanky sort of sound to it, but it could use more highs.

Would it work to just install a (3 way) bright switch that connects to the 2 lugs of the input volume pot just like the Express or Liverpool? I'm not an expert at all, but I would think it would be worth a try and the centre-off position would be like there is no change in the circuit.

I'd love to see some pics or more info about what you've made. Are you going to do some quick sound clips? I'm excited to hear this thing. I'm super curious about it and quite tempted to try one of these myself. I'm unemployed and almost out of savings, but longing for a new project (but don't need any amps...). A Herzog seems pretty tempting though. I love Gordie Johnson's tone. With the abundance of tube overdrive pedals out there, I wonder if there is any reason to think that a Herzog might be obsolete. I bet nothing really comes nearly as close in tone...
I wish there were more easier to find info about these and sound examples...

[The New Steve H]

I'm looking at an Express schematic, and as might be expected, I don't quite get it. I see a "bright" switch on the volume control. Looks like it shoots some extra treble around the volume pot through a capacitor, into the V1a control grid.

I think the problem with the Herzog is that there is no treble to begin with, since there are big ol' caps under all the cathodes. I don't think injecting extra treble from the V1 plate will help, if that treble isn't there to inject. Someone tell me if I'm wrong. What I am wondering is whether I can install alternate bypass capacitors that switch in and out. I think I'll try it and see what happens.

So far, I don't know what to make of this thing. I haven't had much time to play with it, so I don't really know what it can do. I can't say it's blowing my socks off, but I can say I have the only one on the block.

I will try to come up with sound clips, once I'm pretty sure I have it doing what it should. I don't want to make the concept look bad by recording a poor execution!

If anyone knows the working impedance of a Fender jewel light, please let me know. I have to get mine connected somehow. I'm thinking I might just put it across the 125V connections, in parallel with the amp, with a big resistor to bring the voltage down. If that's a stupid idea, it would be good to know before I try it.

[bcmatt]

If anyone knows the working impedance of a Fender jewel light, please let me know. I have to get mine connected somehow. I'm thinking I might just put it across the 125V connections, in parallel with the amp, with a big resistor to bring the voltage down. If that's a stupid idea, it would be good to know before I try it.

Aren't fender style lamps all just 6.3 volts and meant to connect to the heater filaments? Do you have a Fender Jewel lamp assembly already?

So, is your primary goal to use the Herzog on its own as an amp, or are you going to try plugging it into some other amps? I'm real curious what it sounds like into different tube amps. I'm under the impression that its primary purpose is to just go in front of the input of some tube amps and culminate some extra gain altogether in unique ways. I would love to see a video demo of this sort of thing with explanation and walk through, but there just seems to be an absence of all this online... Ima go search youtube again... Gordie Johnson seems to explain his as being basically pretty much off or full on crazy loud with his rig.. but he runs his into an SVT!

About the treble problem, I think you are right on holding off on the Trainwreck style bright switches for now. There is probably something that is not quite right with how you have it now that should be resolved instead of trying to add something new; my bad.

So, you are using the non-Bachman H-Zog schematic?
diagrammatiks schematic seems to be a mix of the two schematics that you posted, and I wonder if perhaps his might be best...

[IMG764]http://i625.photobucket.com/albums/tt33 ... 0fc369.jpg[/img]

How did you wire the tone control? Did you do a rotary switch or a two position DPDT that would simultaneously lift that preamp .02 uF from ground whilst adding that parallel .005 cap to the 150k resister on the output?

I would get rid of that weird mystery 470 cap (or guessing a value) and go with the other schematics regarding the input volume control values (no cap between pot and ground).

I'm curious what sort of filter cap values you went with since there doesn't seem to be any on any schematics? 8uF like the tweed champ, or 20 uF like the Vibro Champ, or something else?

It's weird how there are mixed reviews about the Herzog. the people that are really impressed with it are using the older 6V6 models. Also, they seem to talk about it being quite trebley and abrasive unless tone is rolled back... but that is whist being used in front of an amp...

[The New Steve H]

I know Fender lamps are 6.3V. I wanted to know the impedance because I have a lot of crap on the filament circuit, and I didn't want to add a lamp. I figured if I knew the impedance, I could stick the lamp elsewhere. I believe I can do it by paralleling the lamp with the entire amplifier, with a suitable voltage divider.

Also considering replacing the bulb with an LED. I have a diode I could replace with an LED, "free of charge." What I mean is, there is already a place for a diode in the circuit, so I may be able to use and LED for that diode. I am not a big fan of tiny flashlight incandescents.

I already have the Fender lamp and assembly.

I don't want to fiddle with the circuit too much. It works, and the hum is just about zero, although I am getting some oscillation when the main volume is high.

If you've seen the widely distributed Herzog schematic PDF with two different drawings, you've seen the schematic I used. I used the drawing that has a footswitch jack. I omitted the SS rectifier and added a 5Y3; maybe this was a mistake, but it works fine.

I didn't use the drawing Diagrammatiks kindly provided, not because I didn't like it, but because the amp started working, and I didn't feel like starting over. For all I know, his drawing is a thousand times as good as the design I ended up with.

The Herzog is intended primarily as an effect, but if you have an effect that can also work as an amp, might as well rig it to swing both ways.

I don't think there is anything wrong with the treble. I believe it's supposed to sound this way when used as an effect. It's not optimal for use as an amp, however. That's the reason for the question about rigging alternate bypass caps.

My tone switch is a simple on-off switch. The drawing shows only one contact, so I saw no reason to install a complicated rotary switch.

I have no idea what that little arrow and dashed line and the word "bass" mean, so I pretended not to see them.

I used 8uF filter caps. No choke.

The 470uF "mystery cap" turned out to be a 470pF cap. I put a 470uF job in there at first (as the drawing indicates), and it killed all sound from the amp. Someone informed me that the cap was too big. It was off by a slight amount, i.e. a factor of one million.

[Firestorm]

A #47 lamp draws .15 amps. I'm sure you've got that to spare so just wire it to the heater supply instead of fooling around with trying to manufacture 6 volts from some other source.

How did you wire the filament circuit: ground one side AND use the center tap? Measure the AC across a tube filament and tell us what you get.

This amp should be plenty bright. Even when cathode Rs are fully bypassed, it's not like the high frequencies aren't present, just that the bass frequencies are also there. You can shape the tone with bright caps across the volume pot or by changing the coupling caps. When you pretended not to see the dotted line on the Bass switch, how did you wire it? Permanently in the Bass position by mistake?

[bcmatt]

Sorry, I don't mean to be annoying you about every detail. I am just super curious about this circuit and wondering whether to pull the trigger on trying to build one myself (and add over $100 worth of parts and transformers to an order I am about to make for a simple $3 dual-ganged pot).

I know Fender lamps are 6.3V. I wanted to know the impedance because I have a lot of crap on the filament circuit, and I didn't want to add a lamp. I figured if I knew the impedance, I could stick the lamp elsewhere. I believe I can do it by paralleling the lamp with the entire amplifier, with a suitable voltage divider.

Also considering replacing the bulb with an LED. I have a diode I could replace with an LED, "free of charge." What I mean is, there is already a place for a diode in the circuit, so I may be able to use and LED for that diode. I am not a big fan of tiny flashlight incandescents.

I already have the Fender lamp and assembly.

Fair enough. I felt stupid saying something so obvious since I figured you already knew, and so I guess I my feeling was justified...

I don't want to fiddle with the circuit too much. It works, and the hum is just about zero, although I am getting some oscillation when the main volume is high.

If you've seen the widely distributed Herzog schematic PDF with two different drawings, you've seen the schematic I used. I used the drawing that has a footswitch jack. I omitted the SS rectifier and added a 5Y3; maybe this was a mistake, but it works fine.

So, did you use eyelet board and make a champ-like layout, or are you wired with terminal strips or point-to-point?

I don't think there is anything wrong with the treble. I believe it's supposed to sound this way when used as an effect. It's not optimal for use as an amp, however. That's the reason for the question about rigging alternate bypass caps.

My tone switch is a simple on-off switch. The drawing shows only one contact, so I saw no reason to install a complicated rotary switch.

I have no idea what that little arrow and dashed line and the word "bass" mean, so I pretended not to see them.

How I understand that "rotary front panel switch" is that it is both that bass and brite switches (right above and below it) wired on a knob that clicks back and forth between two positions. Basically a DPDT would work the same (or two separate SPST switches). Anyways, when one is opened, the other is closed. They work together to change the tone. Lifting the 0.02 uF cap on the plate from the ground in the preamp is half of the equation toward giving the "brite" setting. I know this is not what you are asking for instruction regarding, but I can't help wondering if this is what limits your lack of treble response.

The 470uF "mystery cap" turned out to be a 470pF cap. I put a 470uF job in there at first (as the drawing indicates), and it killed all sound from the amp. Someone informed me that the cap was too big. It was off by a slight amount, i.e. a factor of one million.

It makes sense that they meant to put a pF on that diagram and missed it. I guess what nags at me is that there seem to a few versions of the Herzog and some people love while those same people have experienced other versions that they were very disappointed with, and it would be nice to know the actual schematic for the early popular ones. I have those same 2 schematics from Aspen Pittman's Tube Amp book. Is there only 2 circuits? Is the popular one simply the first model (Randy Bachman's)? Or are both those schematics good and people simply complain about the reissues that used an EL84?
In another forum, someone that seemed familiar with it seemed to want to talk about the Bachman one and making me wonder if it is because he didn't think much of the other one:
It's not so much that you have to change the OT itself. The original Herzog (which is what I am referring to, not the H-Zog of later years) used a Hammond 145 series OT. The OT on aHerzog has a load resistor (6ohm 10 watt) and a 1meg pot (to adjust the output), and then into a DPDT switch (to add or remove the Herzog from the circuit).

Any small amp could be modified to work like a Herzog, it would just be a matter of playing around with the load resistor values etc, to match your circuit. The original Herzogs didn't have a footswitch to turn it on or off, but it could be added fairly easily.

A Hammond 145A (named on the Bachman schematic) isn't a ratio meant to connect to a speaker, so I hope that isn't where the magic of the originals is found...
https://images.tradeservice.com/OMHPCVA ... 128_75.pdf
Part No.: 145A
Application: Driver
Nominal Impedance Primary: 100
Nominal Impedance Secondary: 200 C.T.

[The New Steve H]

How did you wire the filament circuit: ground one side AND use the center tap? Measure the AC across a tube filament and tell us what you get.

I'm going to have to go through it again and make a careful drawing, because my current understanding of what I did is that it has two grounds, just as you say. I can't believe that works. I can check the voltage again.

Sorry, I don't mean to be annoying you about every detail.

Doesn't bother me at all.

I felt stupid saying something so obvious since I figured you already knew

You are not likely to insult my intelligence unless you really work at it. Not at this point.

I made an eyelet board, although now I think point to point might have been better, due to the peculiar geometry of the chassis I made.

You should see the relay board I made. If I post a photo, I foresee considerable hilarity.

My suggestion is to buy the parts and get to work. My input may be useless to you, but there are plenty of other people you can talk to. You'll get it right sooner or later.

[bcmatt]

I made an eyelet board, although now I think point to point might have been better, due to the peculiar geometry of the chassis I made.

You should see the relay board I made. If I post a photo, I foresee considerable hilarity.

My suggestion is to buy the parts and get to work. My input may be useless to you, but there are plenty of other people you can talk to. You'll get it right sooner or later.

I look forward to seeing pics.
You are the only one I have ever met who has attempted one of these. Actually, I've never even conversed with anyone who has ever played a Herzog before.
I really don't know whether I should attempt it or not. I am incredibly interested and if I had money just laying around, I would definitely attempt it. Despite my financial situation, I am tempted anyways...
but is it worth it? Would I actually end up using it regularily?
Then, if I decided that it was something I would use, the big question becomes what version of it do I make, and so how would I know which parts to get?
I suspect the Randy Bachman is the more appealing tonally, but it involves some different transformers (I see the 145A is only like $20 though) I don't even know what power transformer is on that schematic (can't find it online-but I suppose a champ one is fine).

Is it possible that the Randy Bachman doesn't need Filter caps (And hence why they are missing on the diagram), or is that just crazy talk?

A typical champ style amp at least has the safety of being able to sell it to some kid without an amp if I don't want to keep it and be able to recoup the expenditure...

Anyways, I'm trying to figure this all out before being "soon parted with my money" as the fool in the story.

[The New Steve H]

I have a new question, if anyone is paying attention.

Yesterday I was reading Merlin Blencowe's book on power supplies, and it explained that power supplies can cause motorboating. If you suck too much current from the caps, you get swings that mimic your playing, and that shows up at the tubes and comes out as output. Something like that.

I'm getting low-frequency oscillation when I crank up the main volume. I assume this is motorboating. I used four 8uF caps on the power supply. The first two off the PT are paralleled. Is it possible 16uF won't cut it for a 5-watt amp? I can pull them out and put something bigger in there, or I could wedge a third 16uF between them for a total of 48.

[bcmatt]

I have a new question, if anyone is paying attention.

Yesterday I was reading Merlin Blencowe's book on power supplies, and it explained that power supplies can cause motorboating. If you suck too much current from the caps, you get swings that mimic your playing, and that shows up at the tubes and comes out as output. Something like that.

I'm getting low-frequency oscillation when I crank up the main volume. I assume this is motorboating. I used four 8uF caps on the power supply. The first two off the PT are paralleled. Is it possible 16uF won't cut it for a 5-watt amp? I can pull them out and put something bigger in there, or I could wedge a third 16uF between them for a total of 48.

Kevin O'Conner's book has a few pages on the Herzog that someone sent me images of yesterday. IN his version he uses 4 20uF filter caps.
I'll pm you a link to that file you can download if you haven't seen it. I'm planning to order 20s for my build.

[The New Steve H]

Thanks for the help. I wonder why this thing needs such big caps. I wonder if those big bypass caps explain anything.

[Structo]

What I was wondering about is why that first schematic, the Randy Bachman one, not show any filter capacitors?
It's like the power supply is incomplete.

Then the second one doesn't show what the values are.

It should have at least 20uF for the reservoir cap and 16uF or so for each succeeding node.

I would not ground the heater supply either, that is an outdated and unsafe method.

Just copy the way a Fender or other simple amp is done.