Still getting buzz with D'Lite build on OD setting. Ideas?

[markmalin]

Hi guys,

I'm still having problems with a buzz when I switch to the OD setting and turn up the level. I have a fainter, higher frequency buzz when I switch on the bright switch. Just wondering if I could get some advice on how to debug this (or if this is normal??). Note that the clean channel is real quiet, even when I turn up the volumes.

I'm playing a Strat, which may be an issue. Things I've tried so far are to use shielded cable on the master volume, preamp volume and drive pot. That helped some. I've shortened grid wires as best I can, and shortened the leads on the caps and resistors on V1. I've poked around a lot with a chopstick, but moving wires around doesn't change the buzz.

Again, this is only in the OD setting (and bright switch). If I play at livingroom volumes, it's faint (almost undetected), but when I turn the levels up it's pretty anoying. Characteristic of the amp??

Thanks for any help or advice on how to track this down.
Mark.

- PS - my digital camera bit the dust so I can't post any pictures of my layout, but I've tried to keep grid wires short and not run grid and plate wires parallel (but I do let them cross). My ground setup is like in the "relay" version of the D'Lite layout diagram from Normster's FTP site. I'm using Orange Drop caps, and all the smaller caps (pf) are silver mica.

[dogears]

Try replacing the bright switch with a 120pf. Should yield a much more useable bright switch tone. I'd 86 the shielded on the master, but use it on the OD pots.

It is not unusual to hear some faint buzz with the bright switch on and OD on. It is probably more unusual to use both together! I use a relay that only allows bright switch operation on the cleans. Great idea as it really wakes up the cleans and doesn't harsh up the OD.

Have you A/Bed the silver mica versus ceramic discs? If not, I'd suggest swapping to ceramic. Not just for the tone, but also reliability (if what I heard about leaky micas is true)

[markmalin]

I'd 86 the shielded on the master, but use it on the OD pots.

dogears,

When you say to use shielded wire on the "OD pots", do you mean all the wires going to both OD pots? Right now I just have the one run from V2 to the OD Drive pot's center connection (whiper). Are you suggesting I use shielded cable on both the OD Level and the Drive pot? And which wires?

Thanks for the clarification
Mark.

[heisthl]

Ideally shield:
1. Input jack to 1st grid resistor (CL1)
2. Volume wiper to 2nd grid resistor (CL2)
3. OD entrance Trim pot to 3rd grid resistor(OD1)(this is kind of optional - because it's a short run, lately I've been doing it anyway for less high end fizz)
4. OD1 output resistor to P1 of Drive Pot
5. Drive Pot wiper to 4th grid resistor (OD2)
6. OD2 ouput resistor (or HRM treble wiper resistor) to P1 of Level Pot
Thats it - try to NOT shield the Master volume or Pre/Pwr jack leads. In spite of all the talk about high end low PF per foot coax, you may find that cheaper cable in the OD signal path makes the OD sound "smoother".

[greiswig]

Trying to tame some of the highs off the OD section on my amp, I ended up putting 50pF or so between the hot leg of the OD trimmer and ground. That seemed to help, but I'm not sure what other effects it may have on the rest of the circuit.

I'm still trying to figure out how to get some low mids/bass back into the PAB section...

[markmalin]

Ideally shield:
1. Input jack to 1st grid resistor (CL1)
2. Volume wiper to 2nd grid resistor (CL2)
3. OD entrance Trim pot to 3rd grid resistor(OD1)(this is kind of optional - because it's a short run, lately I've been doing it anyway for less high end fizz)
4. OD1 output resistor to P1 of Drive Pot
5. Drive Pot wiper to 4th grid resistor (OD2)
6. OD2 ouput resistor (or HRM treble wiper resistor) to P1 of Level Pot
Thats it - try to NOT shield the Master volume or Pre/Pwr jack leads. In spite of all the talk about high end low PF per foot coax, you may find that cheaper cable in the OD signal path makes the OD sound "smoother".

I was able to make all these changes, and swap out the bright cap as well as swap the treble cap for a 330pf (to fatten up the tone). Not a whole lot of change to my ears, but I'm still getting used to using this amp. I'm still waiting on a speaker (thinking of either Weber's version of the G12-65 or the mojotone psyconoodler used on his last amp). That may help with the tone.

Still have the buzz It's not noticable at livingroom volumes on OD, or on the non-OD setting. When you start turning up the volume, though, you can hear the buzz. Heck.... maybe it's my strat and the fact that it's such a high gain amp? If I turn certain directions it will all but stop.

Anyhow... I'm still tweaking!

Mark.

[mlp-mx6]

If you turn the guitar volume all the way down, does it hum? If so, the hum is definitely in the amp. If not, the hum is likely in the input signal. Can you try the amp with a humbucker guitar? (borrowed, whatever) My hunch is that you're hearing single-coil hum, not amp hum.

[tele_player]

If I turn certain directions it will all but stop.

This is pretty definitive proof it's not something in the amp, and is just normal single-coil buzz, highly amplified.

[Ed de Jager]

I am currently struggling with about the same issue.
My amp is absolutely perfect while it is in the clean mode but when i switch on the OD there is a hum whitch i find very annoying.Switching the PAB on too makes it worse so i am looking for a grounding issue in the relay wiring but am unable to find it so far.
I did change the wires to the OD pots to shielded ones but that didn`t make things any better,i changed the grid resistors on V2 to metal film ones,no change.Replaced the shielded wire from the OD drive to V2-7.Same thing.
Off course i firstly changed the V2 itself.I have quite a bit of them and there is a little difference between them,humwise,but on all of them there is hum.

I am currently running ground from the relay PS to the second leg of the PT,from there to the panel switches and from there to the XLR on the back of the amp and have not grounded the housing of the XLR.

Later today i am going to expiriment some with the relay grounds for i have a strong idea that is where i have messed things up somewhat

[markmalin]

If you turn the guitar volume all the way down, does it hum? If so, the hum is definitely in the amp. If not, the hum is likely in the input signal. Can you try the amp with a humbucker guitar? (borrowed, whatever) My hunch is that you're hearing single-coil hum, not amp hum.

Yah, it does go away when I turn the volume off. It's certainly in the input signal -- likely the single coil pickups. In fact, when I switch to position 2 on the strat (humbucking neck and center pickup) it's quieter. Sounds like it's just single coil hum being amplified.

I'll try my ES-175 through it today to see if humbuckers help.

Mark.

[markmalin]

Later today i am going to expiriment some with the relay grounds for i have a strong idea that is where i have messed things up somewhat

Let me know what happens when you do this. I'm curious to know if you come up with anything.

Cheers,
Mark.

[Normster]

Later today i am going to expiriment some with the relay grounds for i have a strong idea that is where i have messed things up somewhat

I had similar issues with OD hum on an early build. I replaced the relay board and the noise went away. I didn't check the board, but I suspect that I had some conductive flux or maybe sloppy wiring beneath the board. Anyway, I think you're on the right track.

[markmalin]

I had similar issues with OD hum on an early build. I replaced the relay board and the noise went away. I didn't check the board, but I suspect that I had some conductive flux or maybe sloppy wiring beneath the board. Anyway, I think you're on the right track.

Hey Normster,

Did you replace the relays, too, or just the board? I was wondering about the relays or the board, or lead dress on the relay board. Maybe I'll look at that -- but could the relays be suspect, too?

Mark.

[Ed de Jager]

I will take out the board and check the backside.
Had no luck so far.
Grounding of the XLR didn`t help nor changing the ground wires to a different leg on the PT.
Tried an ecc81 in V2 but the hum`s still there.I thought it was due to the high amplification and changing to a tube with less would help.
I did like the tone i got with it very much though.
I`ll look at changing the ground wire of the anodes but don`t think that will help a lot.
The treble relay doesn`t add to the humm,it`s just the OD and PAB so it kind of must be in the grounding i think.

[markmalin]

I will take out the board and check the backside.
Had no luck so far.
Grounding of the XLR didn`t help nor changing the ground wires to a different leg on the PT.
Tried an ecc81 in V2 but the hum`s still there.I thought it was due to the high amplification and changing to a tube with less would help.
I did like the tone i got with it very much though.
I`ll look at changing the ground wire of the anodes but don`t think that will help a lot.
The treble relay doesn`t add to the humm,it`s just the OD and PAB so it kind of must be in the grounding i think.

Thanks for the update. I had also considered a 12AT7/ECC81 in V1 or V2. I'm curious, what do you like more about the tone with the ECC81?

I'm still not completely satisfied with the tone of the amp. I'm such a "Fender guy" that I'm expecting the depth of a Fender in the clean setting, but I think I need to just get used to using it. Haven't had a chance to really "open it up" volume-wise yet because someone else is always home Once I get the speaker I'll have to take it to a blues jam and see how it really sounds!

Mark.