Best Way to Reduce Hum?

[FourT6and2]

I am starting a build based on this amp from Ceriatone (Chupacabra): http://www.ceriatone.com/ceriatone/w...0Sept-2015.jpg

As you can see, this particular circuit, as Ceriatone designed it, incorporates DC Heaters—on V1 and V2 only—by using the JTM45-style 1202-55 Power Transformer's 5v taps. Since that amp originally used a tube rectifier and this one uses SS diodes, those taps are free for use.

Anyway, I read on another forum where some people were saying this method of running DC Heaters wasn't very good. So my question is what would y'all do instead? The amp is high-gain. And very angry sounding (in a good way).

Options:

1. Do nothing and run the amp with regular AC Heaters.
2. Use the DC Heater scheme as Ceriatone does it in the above layout.
3. Install a simple Humdinger pot at the end of the heater string.

Or...

4. Elevate the heaters as I've drawn here. Did I do this correctly? Is that a good place to reference the heaters or is there a better place where the B+ might be more filtered? I found a schematic on this site for the Yeti, which is a similar amp. HT2 at this point in that schematic was listed at 465v. Using that number, I calculate 42.3v for an elevated heater reference. But no way of knowing for sure because I haven't built the amp yet and I'm probably using a different PT transformer. LINK: http://orig10.deviantart.net/d4cd/f/...lm-dbaw3uv.jpg

Thanks!

[Enzo]

My option:
Ignore the some people on an internet forum who say it is a bad method., and just wire the thing like the people who MAKE the amp suggest.

If you elevated something in your layout, I don;t see it, much prefer using a schematic. LAyouts are for building, not for circuit discussions.

[FourT6and2]

My option:
Ignore the some people on an internet forum who say it is a bad method., and just wire the thing like the people who MAKE the amp suggest.

If you elevated something in your layout, I don;t see it, much prefer using a schematic. LAyouts are for building, not for circuit discussions.

Ah. I see.

Well, the circuit wasn't designed by Ceriatone. I don't want to get into the politics of it or anything. But the actual design came from an incorrectly-drawn schematic found on the net. So it's not like it was designed to sterling standards if you know what I mean...

As far as a schematic goes, here's a link to the Yeti, which is the same amp (beyond a few voicing changes). You can see the the DC Heater arrangement there: LINK: http://music-electronics-forum.com/t43046/ But that schematic's DC regulation doesn't match the layout from Ceriatone. I'll see if I can create one that matches the layout and matches the amp I have and post it when I can.

As for my layout, the Elevated Heaters are next to the Power Transformer and labeled "Elevated Heaters."

[Enzo]

Fair enough. But no reason a nice DC supply can;t come from the 5v winding. Frankly I;'d ditch the regulator and just use a diode to drop half a volt.

[Tom Phillips]

... Layouts are for building, not for circuit discussions.

I agree. It is best to post the SCHEMATIC when requesting opinions about circuit theory or function.

[FourT6and2]

I agree. It is best to post the SCHEMATIC when requesting opinions about circuit theory or function.

I would love to post a schematic. But one does not exist.

Here is the best I could do with the free software online that I don't know how to use lol. This is how the layout shows it as far as I can tell. So... go this route or elevate the heaters instead or just run regular AC heaters?

[Enzo]

This should work, or my diode approach. You could easily elevate the entire heater string instead of using DC. There is no right and wrong here, there is just a multiple option choice.

[FourT6and2]

This should work, or my diode approach. You could easily elevate the entire heater string instead of using DC. There is no right and wrong here, there is just a multiple option choice.

Right, that's why I started this thread. There is no right or wrong way. But there are options. I'm trying to understand the pros/cons of each one so I can make the right decision for this specific application. Here's where my head is at:

AC Heaters
Simple. Easy. Standard. The way it's been done for years. But can induce hum if lead dress is bad, or even if lead dress is good if the amp is high-gain (like this one).

AC Heaters with Humdinger
I've never tried this. So I don't know how it can turn out.

DC Heaters as Shown in Layout/Above Schematic
I do have this amp already built by Ceriatone and it sounds good. There isn't a lot of hum or noise. But I have nothing to compare it to. Some people more knowledgable than I say it can cause more noise than it resolves and it can adversely affect the sound/tone of the amp somehow... I don't know either way. Another con is just added parts/labor for the build. My goal with building one for myself is to experiment. So I guess I might try it with and without this method...

Elevated Heaters
Good for reducing cathode-to-ground voltage differential on CF stages. Can also reduce some noise. But some people have told me they haven't noticed a single bit of difference with/without elevating the heaters in a circuit like this (noise-wise). So that might mean there isn't a lot of noise induced from the heaters in the first place? Pro is it's easer to implement than DC Heaters and it can help with CF stages even if there is no noise reduction.

I guess I'm posing the question as: if you were building this amp, which would you go with and why? My instinct is to go with elevated heaters because it's simple and less can go wrong than with DC Heaters.

[Enzo]

There are a zillion sources of hum, each one different from the next, and each with its own solution. Filter caps have no effect on grounding hum, and shielding signal leads does nothing about power supply ripple, for example. Not all amps have all types of hum. There are plain old vanilla wired amps that are quiet, and there are fancy high tech wired ones that STILL hum. While it is a nice side effect, elevating the heaters by 20v or whatever is not about reducing the CF voltage thing, it is about reducing the potential for heater to cathode noise in sensitive preamp tubes.

If someone sees (well, hears) no difference between elevated and not, then that particular amp is not suffering from heater/cathode induced hum. So the cure does nothing. Might make a difference one day with different tubes in it though.

Lead dress matters in all amps, regardless of heater involvement. Your high gain amp might hum for reasons other than lead dress, so perfect dress being only ONE factor, it isn;t ALL the problem.

Plain old AC heaters work just fine, a billion Fender amps as evidence if nothing else. But heaters must always be referenced to ground one way or another, usually by a grounded center tap, or virtual center tap (the pair of 100 ohm resistors on soooo many Fender amps). Even grounding one side is better than no ground reference.

Humdinger - the hum pot? It is nothing more than the two 100 ohm resistors turned into a pot. It allows you to tweak it. You can ground the wiper or connect it to a DC elevated source.

DC heaters? That is another way for input stages and high gain stages to eliminate the heater cathode hum. If you have one wired this way and it is quiet, then it is quiet. If it magically makes noise you can't hear, well, you can't hear it. Ifhere is some small amount of hum, it may well have nothing to do with heaters in the first place.

Ever hear someone complain their amp hums at volume zero, but hum goes away around 2 or 3 on the control, and them louder after that? ie, hum is least at 3 on the knob. I hear that a lot, and what it means is that amp has at least two sources of hum, and they happen to be out of phase with each other. They meet at that control, and 3 is where they exactly cancel.

In my head, I use elevation if I have cathode biased power tubes, as the cathode voltage is a simple, convenient place to steal a positive voltage. Fenderish amp, I wire like any Fender amp, plain old AC heaters. If I want to build a screaming high gain MArshally thing - not my personal taste - I'd likely wire the first two tubes for DC, but frankly I;d leave space for that supply, and just wire it AC first and see if I even have the problem.

All these approaches have been around for decades, and all work. If someone makes a vague claim that it causes more problems than it solves, I would immediately ask, what are those problems specifically, and how often do they arise? And if they tell you heater wiring affects tone, ask the same thing. Just what specific affect does it have on tone?

[FourT6and2]

There are a zillion sources of hum, each one different from the next, and each with its own solution. Filter caps have no effect on grounding hum, and shielding signal leads does nothing about power supply ripple, for example. Not all amps have all types of hum. There are plain old vanilla wired amps that are quiet, and there are fancy high tech wired ones that STILL hum. While it is a nice side effect, elevating the heaters by 20v or whatever is not about reducing the CF voltage thing, it is about reducing the potential for heater to cathode noise in sensitive preamp tubes.

If someone sees (well, hears) no difference between elevated and not, then that particular amp is not suffering from heater/cathode induced hum. So the cure does nothing. Might make a difference one day with different tubes in it though.

Lead dress matters in all amps, regardless of heater involvement. Your high gain amp might hum for reasons other than lead dress, so perfect dress being only ONE factor, it isn;t ALL the problem.

Plain old AC heaters work just fine, a billion Fender amps as evidence if nothing else. But heaters must always be referenced to ground one way or another, usually by a grounded center tap, or virtual center tap (the pair of 100 ohm resistors on soooo many Fender amps). Even grounding one side is better than no ground reference.

Humdinger - the hum pot? It is nothing more than the two 100 ohm resistors turned into a pot. It allows you to tweak it. You can ground the wiper or connect it to a DC elevated source.

DC heaters? That is another way for input stages and high gain stages to eliminate the heater cathode hum. If you have one wired this way and it is quiet, then it is quiet. If it magically makes noise you can't hear, well, you can't hear it. Ifhere is some small amount of hum, it may well have nothing to do with heaters in the first place.

Ever hear someone complain their amp hums at volume zero, but hum goes away around 2 or 3 on the control, and them louder after that? ie, hum is least at 3 on the knob. I hear that a lot, and what it means is that amp has at least two sources of hum, and they happen to be out of phase with each other. They meet at that control, and 3 is where they exactly cancel.

In my head, I use elevation if I have cathode biased power tubes, as the cathode voltage is a simple, convenient place to steal a positive voltage. Fenderish amp, I wire like any Fender amp, plain old AC heaters. If I want to build a screaming high gain MArshally thing - not my personal taste - I'd likely wire the first two tubes for DC, but frankly I;d leave space for that supply, and just wire it AC first and see if I even have the problem.

All these approaches have been around for decades, and all work. If someone makes a vague claim that it causes more problems than it solves, I would immediately ask, what are those problems specifically, and how often do they arise? And if they tell you heater wiring affects tone, ask the same thing. Just what specific affect does it have on tone?

Thank you for that thought-out response

Yeah, those are the exact questions I had when people made those comments. I received no response.

This amp is indeed a "screaming high gain Marshally thing" So I'd like to make sure it's quiet. The one I have (built by Ceriatone) is quiet enough. But since I'm building my own, I figured I'd try something else. But I guess if it ain't broke...

[Enzo]

Hey, go ahead and try something else. It isn't hard to alter heater wiring if you allow for it ahead of time. I have my opinions on things, but there is no reason you can;t explore and learn. You will learn a hell of a lot more by doing the experiment than you will from reading internet debates on it.

[Randall]

I say try all three, and answer the questions yourself, and then tell us what you found.

[FourT6and2]

I say try all three, and answer the questions yourself, and then tell us what you found.

Ain't nobody got time fo' that!

It'd be easy enough to compare AC Heaters and DC Elevated Heaters. Would only require lifting one wire and jumping the PT CT back to ground instead of the voltage divider. But to test out the DC Heaters, I'd have to wire up and install a whole new board and set of parts and additional heater wire string to V1 and V2. That's too much work. I already have this amp built with DC Heaters though. So I could compare it to that one, back-to-back.

[Enzo]

I'd have to wire up and install a whole new board and set of parts and additional heater wire string to V1 and V2. That's too much work.

Do whatever you are interested in doing. As to the heater wiring, all you need do is lift the wires from V3 over to V2, and connect then instead to a DC supply on a tiny piece of perf board. And for that matter, you could run this amp for a year, and then alter the heater wiring then in a fit of interest.

[Chuck H]

The amp in question uses partially bypassed preamp cathodes for voicing. This is a good case for DC heaters. Even with higher gain designs I've done well with typical AC filament wiring by fully bypassing the cathode of first gain stage. The trend of using partially bypassed cathodes for guitar amp voicing has been taken out of context IMO. I do design with partially bypassed preamp cathodes, but I've gone back to some older designs and revoiced them with a fully bypassed first gain stage and a smaller coupling cap. Or, when the coupling cap and bypass cap create a shelving effect I've had to get a little more creative. But IMHO you can reduce the potential for filament hum (all other things being ideal) by just fully bypassing the first gain stage and omit the need for DC filaments. YMMV.