Photo of my honey which I built into an old pedal enclosure.

Quote from: g1 on October 26, 2025, 11:09:54 AMAgree with Juan, screens were not as big a concern back when tubes were much more robust and had tighter tolerances in manufacture.
Screen resistors were sometimes just used for dealing with instability due to layout etc.
You will find a fair bit of stuff from that era with screen resistors only on some of the power tubes.  The power supply dropper resistor for the screen node is considered a 'common screen resistor' for all the power tubes together.  So much so that Traynor even set bias for one of it's models by measuring voltage drop across the screen node supply resistor.

Thanks G1  !!!

I have seen the common PS dropper resistor in other Peavey amps (as in the Triumph 60/120).  But in those amps, each tube had its own screen resistor. 

I guess it was an evolving design - as the next Mace version (the VT) included a resistor for each tube.

So far, the amp owner reports the amp is working - but he is using it at a very low volume.  If the amp ever makes it to a live gig and higher volume levels, perhaps it will be time for a sextet  set, modifying the screen resistors, and biasing.

And G1, good to see you and JMF here!!!

Thank you.

Agree with Juan, screens were not as big a concern back when tubes were much more robust and had tighter tolerances in manufacture.
Screen resistors were sometimes just used for dealing with instability due to layout etc.
You will find a fair bit of stuff from that era with screen resistors only on some of the power tubes.  The power supply dropper resistor for the screen node is considered a 'common screen resistor' for all the power tubes together.  So much so that Traynor even set bias for one of it's models by measuring voltage drop across the screen node supply resistor.

Have you checked the spec for input sensitivity of this power amp?  If it's designed for PA use it may need more signal than you are used to with hifi components.

The most standard, tried and true method is a pad/attenuator at the input; either using 2 input jacks or a switch.  Usually labelled Lo and High, or passive/active.
It is still the most common method you will find in use today.
Is there a particular reason you do not want to use this method?  Perhaps trying to address any shortcomings would be easier than trying to 're-invent the wheel' so to speak.

The pre-amp I'm designing is running off of ±12V, and boosts over 5x already start clipping transients, and that's from some overwound mini-humbuckers.  I hesitate to think what full 'buckers or active pickups like the EMGs that can output up to 3V will do. The goal is clean boost at the front end, so all the overdrive comes from everything after that.

So, basically, just design for the most headroom and hope for the best?  There aren't too many common op-amps designed for high voltage, unless I want to use a poweramp like the LM1875 as a common op-amp; that one goes up to 60V (I assume that means ±30v), or new devices like the MAX74810 that can handle 50V.  The cheapest, highest voltage through-hole DIP I could find was the LF356 that can handle 44V, but you have to get the right one.  All others in the LF35x line are 36V, which is still respectable, but that's what most common op-amps will handle, so why look for specialty devices?

I was thinking also some simple soft-limiting up front might be ideal, which would leave the potential for some clipping at input, but then again, there's not many tube amps that are completely clean, and overdriving them is kinda the point, so maybe that would be OK.  Back to the drawing board... 

I got my replacement pot in today it's a little shorter but seems to be long enough

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I wigged out noticing the locater tab was 180 off but realized I put the old one back on wrong

Got everything soldered up and installed

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The first thing I did was hook up signal and scope but I couldn't get it to work 
I wanted to watch the amplitude change as I turned the volume control.  I did manage to get input and output signal but seemed to be backwards to my horror   

Moving right along I had to unhook my present jams and attach some speakers and a cassette player

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And I'm glad it's working 

I'm glad the meters work and the volume is not backwards
I'm glad that both channels work.
I'm glad that surprisingly it's dead quiet when nothing is playing

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The thing that bothers me and that is for another day....is this thing is at like 3/4 volume and either the cops should be here or my wife trying to kill me.

So yeah it's not the loudest. 

I have it at (for me) decent listening volume.  If we were talking you might have to speak up or occasionally ask me to repeat something so that's cool.

But I thought like at half volume speakers would be melting 

And I know yeah there's probably many other factors 

I'm noticing now the power light doesn't work.

But hey I'm loving it right now     

Been a crazy busy week and now I'm sitting here at 0430 rockin some tunes 

Quote from: J M Fahey on October 24, 2025, 07:58:52 AMJust add the 1k 5W screen resistors plus fresh tubes.

Thank you Juan...

In principle, lower first stage gain, there is only so much swing you can get out of a piss poor 9V supply.

For high gain humbuckers or active pickups, often no more than 2X, go figure.

A regular Op Amp, say TL072, can only swing within 2V of 9V or ground so 5Vpp tops.

Rail to Rail Op Amps such as LM833 can swing the full 9V pp

IF you increase supply to 18V or higher, up to +30V single supply, headroom improves dramatically.

I see there are 4 or 5 different threads on the Honeybadger amp, some must include necessary data, it HAS been built by a few.

If not, we can kludge up a BOM but first search around.
No need to reinvent the wheel