Mojo tone super reverb new build causing ghost notes

[mresistor]

I'm late to this thread and pardon me if you've said so already.. but have you tried swapping out tubes?

[Willabe]

Your build looks nice.

The notes i am hearing are octave sounding lower and out of tune with the root note, it decays before the root note, and more noticeable the harder you dig into the note.

That can be a bad B+ filter cap or not enough B+ filtering.

[Willabe]

How did you do your grounding?

Looks like you didn't separate the B+ filter cap grounds, power tube OT CT filter cap, screen cap, PI cap, from the rest of the B+ filter caps?

I only see a white wire from under the chassis, the dog house, going to a PT bolt with the PT CT red/yellow wire?  Is another dog house ground wire?

You have the roach trem grounded with the power tube  - bias ground. That could be a problem.   

Link for eggbert's chassis gut pics;   
https://el34world.com/Forum/index.php?topic=27534.msg302734#msg302734

Grounding;

http://www.valvewizard.co.uk/Grounding.pdf

[Willabe]

You have ground spade lugs on all 4 of the PT bolts.

Those nuts will get loose over the years, even with thread lock.

And your power cord 3rd wire safety ground is on 1 of those bolts. At the very least put a 2nd nut, with no washer, on each bolt and with a wrench on the nut touching the chassis take a nut driver and tighten those 2 nuts together, with thread lock.

[eggbert]

Sorry getting back so late to your reply’s, most of the things you mentioned about grounding and filter caps, etc, has all been redone those pics are older, p.t bolts grounds were redone again even after a p.t. Swap.  I ran signal from my 22watt preamp out to phase inverter of the 40 watt and ghost notes were still there, even ran the pre signal out of the 40 watt into my 22 watt at the p.i and ghost notes present there too ??????? I dont get it. Again sorry for late response. Changed ot and pt, choke, tubes filter caps, coupling caps etc,  th only thing to do is rebuild it on a epoxy board instead of fiber board,  maybe conductive ? 

[shooter]

is this a fixed bias amp?
if so, drop the bias to "cold" any change?
if it's self biased, you can get some pretty ugly harmonics (non musical) when driving it to square waves

[joesatch]

keep us updated. I'm building this exact kit, i received it from Mojo last week. I assume you're measuring all values before soldering. Some of those Carbon Comp resistors can be way off. I measured some of the 470k and they were reading less than 400k

[gfarina55]

The notes i am hearing are octave sounding lower and out of tune with the root note, it decays before the root note, and more noticeable the harder you dig into the note. I will try to upload a clip as soon as i can. Thanks for the reply’s

What guitar are you using?

I just built a 5F6A that does this to a certain extent, as do some of my other vintage-style amps. And by "this", I mean the exact phenomenon you describe above. I was a bit worried that I'd done something wrong, but then I tried playing some overdriven leads with the same guitar on my trusty C-30, and low and behold, ghost notes! (Why had I never before noticed this?) Then I tried a few more vintage-style amps, and some did and some didn't. Then I tried experimenting with pickups: Les Paul humbucker neck pickups = annoying out-of-tune ghost notes on many amps when overdriven. Single coils = almost never, occasionally on a very hot neck pickup.

I spent some time tracking down possible causes. (I tried grid-stoppers, messed with grounding, tried to track down oscillations, etc. to no avail.) Then I searched for this phenomenon on the guitar forums. It's apparently common, especially among Les Paul players who play overdriven leads on the neck PU. I came to the conclusion that the cause is the "vintage" power filtering on some amps that were never designed to handle the thick, powerful tone that comes from a Les Paul humbucker. You can beef up the power filtering, but that changes the tone of the amp, and I chose to leave my 5F6A stock. Interestingly my Les Paul is the main culprit, and I can successfully use my 335 on most of my Tweed amps w/out ghost notes.

So my solution is to match the guitar to the amp. I'd never sacrifice the magical sound of a Tele through a great tweed just so I can play overdriven Les Paul leads through the same amp. Your problem may be something completely different (I didn't read the entire thread), but I can say that your description sounds exactly like what I'm hearing.

[eggbert]

Fixed adjustable bias, yes i tried a very cold bias 12 to 14 ma/my per tube, amp sounds best @ 32 to 34 and dead quite, no hum issues at all.  I do measure all my pieces before install and i pick certain ones, just totally stumped i have built a few exact with no issues at all, yet did measure small dc on fiberboard in different spots, thinking board is too conductive and maybe that’s why i get it thru preamp section out to another amp, and power section being feed by another amp…. Guess that’s the true meaning of GHOST NOTES.

[eggbert]

I already increased the filtering in the amp, almost doubled the original values just to test and didnt worry bout the tone for testing just wanted them ghosts to go bye bye. Also used several different guitars and cabs, 12 guitars and 8 different speaker setups, to be exact. It is more apparent on neck pickups doing single notes 9th fret and higher. But its there… i have used same wire, solder, placement of parts and layout on previous amps with no issue. Changed the tubes i think 5 times now, just lost on it.  Thank you to everyone jumping in and trying to help, much appreciated.

[gfarina55]

I already increased the filtering in the amp, almost doubled the original values just to test and didnt worry bout the tone for testing just wanted them ghosts to go bye bye. Also used several different guitars and cabs, 12 guitars and 8 different speaker setups, to be exact.

Well, there goes my theory then. Good luck!

[joesatch]

Lift the board off the chassis as high as you can, put some pieces of wood or plastic under it and test again

[eggbert]

Already unbolted the board and lifted as high as i could, no difference. Even used different make trannys just to see if it is heyboer bad batch or run ? Ran nfb, 3 way to switch still did it, disconnected nfb still did, disconnected reverb section and tranny still did it, redid bias section 3 times with different grounding, still did it, everything seems perfect, and sounds great, just the ghosts are really noticeable when volume is above 5 and start to push the amp into breakup. A distortion or overdrive pedal makes them appear at lower volumes, almost like its in both pre and output sections, that’s why i am thinking its the board.  Thanks again everyone

[joesatch]

could be a bad tube socket

[eggbert]

Thought that at 1 point or another until i ran the preamp section out to another tube power amp and low and behold the ghosts are still there…… as i said earlier i also ran my 22watt preamp and tied it to the phase inverter and the ghosts are still there….. almost like its in both sections so the only thing left i thought is preamp power caps ( changed them 3 times) grounding that may tie these points together ( ran separate grounds in 3 different ways ) still there.   Type of solder ???????  Or conductive board ??????  Thanks

[PRR]

Ceiling fan??

(Years ago we had a RASH of odd sounds. After all the usual electric suggestions, we learned to ask "Ceiling fan?" In many cases, that was the cause. The blades reflect sound in strange ways. However we have not see in in some years? Obviously weather related-- is this a hot September somewhere?)

[eggbert]

No ceiling or regular fans, no ac on, dehumidifier turned off. Work bench has its own breaker, with and without ac regulator, still ghosts. I am not giving up.  Thanks