Obnoxious hum on Bogner Shiva 20th Anniversary head

[derrek_clay]

Hi, everybody.
So, I'm having a problem with my guitar amp humming. I've tried everything to fix the issue, including taking my amp to two different techs. I'm kinda at a loss.
The amp head is a Bogner Shiva 20th Anniversary w/ reverb.

I use the amp for recording work, so unfortunately, simply tolerating the hum is not an option. I need the hum gone or at least made very, very quiet.
As of now, it's at a very audible volume. I wouldn't call it loud, but it is far from quiet and it is incredibly distracting.

Before anyone suggests it - Yes, I could filter out the hum after its made it's way onto the recording, but this is a huge pain to have to do to every single guitar track I record. This would not actually fix the problem and isn't really a good solution, so don't suggest this please.

- Please read all bullet points/symptoms below before making suggestions - as they should help to narrow down the issue and eliminate many theories/causes.

I'll attach a clip of the hum below, but here are all the pertinent details.


- The amp hums with nothing plugged in

- Hum seems to be at 120hz. Possibly 60hz. Listen to recording for reference.

- Hum does NOT increase with volume - constant level

- I tried pulling all tubes except the phase inverter, one at a time - hum remained.

- Put all tubes back in, removed Phase Inverter tube (V7) hum disappeared completely

- I have tried a HumX, power conditioner, a Furman hum/noise eliminating power strip - all to no avail

- I have taken it to two amp techs - both of whom supposedly fixed the issue (according to them) by replacing filter caps. Yet the hum remains

- The amp's Presence knob adds a bit to the hum. Brings in an additional overtone. Sounds like a separate issue, or merely the knob adding actual presence to the hum. This overtone is much quieter. The hum still remains if presence knob is backed all the way down, and does very little to affect the hum.

- Plugged in a friend's amp at my house. Seemed to hum a small amount, but nowhere near as loud as mine.

- The hum does not come in immediately when turning on the amp. Rather, it warms up with the amp - so as the amp begins to pass audio as it warms up, the hum comes in as well.

- There is no noise or hiss associated with the hum.

- The hum persists even when plugged into other power outlets

- Going through the FX loop makes no difference

- Plugging into power strip/surge protector makes no difference

- Changing out power cable and speaker cable makes no difference

- Changing the amp's impedance (also changing the cab to match) makes no difference

- both channels of the amp produce hum

- hum becomes even louder if reverb channel is engaged (spring reverb w/ tank)

- hum remains even with reverb all the way down, disconnected, or reverb tank removed from the chasis completely - hum persists

I should note that I have a pair of studio monitors in the same room which do not hum. Given that my friend's amp also produced very little hum, I'm not sure if the room itself is actually the culprit.

I'm going to try taking the head to a friend's house and plugging it up there to see what happens, but as for now, I've tried absolutely everything.
I absolutely love the tone of this amp. I really don't want to have to sell it, but it's beginning to look like I'm running out of options.

Any help/advice would be greatly appreciated.
Thanks!

 

[LP Freak]

I had a similar problem with a Marshall style head. It turned out to be the windings in the PT vibrating. I swapped it out and viola! I'd give Bogner a call they're pretty helpful over there.

 

[232cap]

Try the power tubes.

 

[Chris6870]

I'd give Bogner a call they're pretty helpful over there.

This - They helped me over the phone in the past.

 

[Hey_bert_whtcha_doin_bert]

I'd say also to try power tubes since you never said you actually replaced them

 

[Hey_bert_whtcha_doin_bert]

Did the "techs" recreate the sound at their shop?

 

[glip22]

I might be able to help you. I had the same issue with my 20th. I told Bogner that I thought it was emf generating from the power section. I sent the amp to Bogner and they rewired the PT leads and called it fixed. It was not fixed.
I figured out what it was and was able to diminish it greatly. I believe you have the same issue. It's been a awhile so I will need a refresh on the guts. There are 2 large ceramic caps near the power tubes. I think they are green discs. These caps were picking up the emf and injecting it into the circuit. What I did was carefully bent those caps down toward the edge of the rear of the amp where they are located. I was lucky as this somehow reduced the emf injection. I placed my fingers in the amp without touching anything, noticing how my body would act as ground and reduce the hum. I figured the caps out this way.
There is also something else you can try since your presence pot is affecting the hum allot. I cannot remember if my presence acted the same but I think it did.
At the time I owned that amp I did not have the fix for the presence. I later figured that out on another head that had hum injection affected from the presence circuit. The fix was to place a 5-10pf mica cap across the ground side of the PI coupling caps or two resistors in that area. I would need to refresh myself on exactly which resistors. They had to do with the PI. Maybe tail resistors.Completely eliminated it and will not affect tone. I am not sure if it will work in the Shiva but it might. I can tell you it made the hum much much less and really what I would consider quite normal in some amps.

 

[just42dave]

I was gonna say replace pi and power section as presence works the power tubes if im correct. But what glip said takes the cake ..Pure genius

 

[derrek_clay]

I had a similar problem with a Marshall style head. It turned out to be the windings in the PT vibrating. I swapped it out and viola! I'd give Bogner a call they're pretty helpful over there.

This might be the issue then. I'll try taking the amp to yet another amp tech and have them address this as well. Perhaps that paired with Glip's suggestions will finally rid me of the hum.

Try the power tubes.

I'd say also to try power tubes since you never said you actually replaced them

Interestingly enough, I swapped out the power tubes and the hum got slightly duller sounding. A little bit more quiet too. This leads me to believe that something in the power section of the amp is getting amplified before it reaches the output.

I'd give Bogner a call they're pretty helpful over there.

This - They helped me over the phone in the past.

They basically just told to take the amp to a tech, which I did... twice. :'(

Did the "techs" recreate the sound at their shop?

Ya know, it's funny... I brought the amp back today and the hum was significantly quieter at their shop... Dirty power at my house perhaps?

I might be able to help you. I had the same issue with my 20th. I told Bogner that I thought it was emf generating from the power section. I sent the amp to Bogner and they rewired the PT leads and called it fixed. It was not fixed.
I figured out what it was and was able to diminish it greatly. I believe you have the same issue. It's been a awhile so I will need a refresh on the guts. There are 2 large ceramic caps near the power tubes. I think they are green discs. These caps were picking up the emf and injecting it into the circuit. What I did was carefully bent those caps down toward the edge of the rear of the amp where they are located. I was lucky as this somehow reduced the emf injection. I placed my fingers in the amp without touching anything, noticing how my body would act as ground and reduce the hum. I figured the caps out this way.
There is also something else you can try since your presence pot is affecting the hum allot. I cannot remember if my presence acted the same but I think it did.
At the time I owned that amp I did not have the fix for the presence. I later figured that out on another head that had hum injection affected from the presence circuit. The fix was to place a 5-10pf mica cap across the ground side of the PI coupling caps or two resistors in that area. I would need to refresh myself on exactly which resistors. They had to do with the PI. Maybe tail resistors.Completely eliminated it and will not affect tone. I am not sure if it will work in the Shiva but it might. I can tell you it made the hum much much less and really what I would consider quite normal in some amps.

With any luck, you might have just pegged the issue. If you can find out specifically what you did/what caps you used, etc. that would be incredibly helpful. That way I can take the amp to someone else and have them look into this. Hopefully addressing the issue specifically will help.

 

[glip22]

I had a similar problem with a Marshall style head. It turned out to be the windings in the PT vibrating. I swapped it out and viola! I'd give Bogner a call they're pretty helpful over there.

This might be the issue then. I'll try taking the amp to yet another amp tech and have them address this as well. Perhaps that paired with Glip's suggestions will finally rid me of the hum.

Try the power tubes.

I'd say also to try power tubes since you never said you actually replaced them

Interestingly enough, I swapped out the power tubes and the hum got slightly duller sounding. A little bit more quiet too. This leads me to believe that something in the power section of the amp is getting amplified before it reaches the output.

I'd give Bogner a call they're pretty helpful over there.

This - They helped me over the phone in the past.

They basically just told to take the amp to a tech, which I did... twice. :'(

Did the "techs" recreate the sound at their shop?

Ya know, it's funny... I brought the amp back today and the hum was significantly quieter at their shop... Dirty power at my house perhaps?

I might be able to help you. I had the same issue with my 20th. I told Bogner that I thought it was emf generating from the power section. I sent the amp to Bogner and they rewired the PT leads and called it fixed. It was not fixed.
I figured out what it was and was able to diminish it greatly. I believe you have the same issue. It's been a awhile so I will need a refresh on the guts. There are 2 large ceramic caps near the power tubes. I think they are green discs. These caps were picking up the emf and injecting it into the circuit. What I did was carefully bent those caps down toward the edge of the rear of the amp where they are located. I was lucky as this somehow reduced the emf injection. I placed my fingers in the amp without touching anything, noticing how my body would act as ground and reduce the hum. I figured the caps out this way.
There is also something else you can try since your presence pot is affecting the hum allot. I cannot remember if my presence acted the same but I think it did.
At the time I owned that amp I did not have the fix for the presence. I later figured that out on another head that had hum injection affected from the presence circuit. The fix was to place a 5-10pf mica cap across the ground side of the PI coupling caps or two resistors in that area. I would need to refresh myself on exactly which resistors. They had to do with the PI. Maybe tail resistors.Completely eliminated it and will not affect tone. I am not sure if it will work in the Shiva but it might. I can tell you it made the hum much much less and really what I would consider quite normal in some amps.

With any luck, you might have just pegged the issue. If you can find out specifically what you did/what caps you used, etc. that would be incredibly helpful. That way I can take the amp to someone else and have them look into this. Hopefully addressing the issue specifically will help.

Just show them the post. Any tech will easily know what I am referring too. I used a 10 pf mica 500v cap, but others will work. It may have been a 5 pf. Whatever lowest value of PF that might work. I am fairly sure I bridged the PI coupling caps with the cap. This was on a MArshall mod though. The Shiva I just bent the caps down. Start with bending the caps down or if the tech gas a better idea, go for it. A small shield might work. Granting this is the issue. Probably is.

 

[derrek_clay]

I see, I see. Not sure if I'd feel comfortable trying it myself though. Haha I'd be too afraid of breaking something or getting shocked to death. Might be better to let a tech give it a shot.. though I hate to spend any more money on it at this point... :'(

 

[glip22]

I see, I see. Not sure if I'd feel comfortable trying it myself though. Haha I'd be too afraid of breaking something or getting shocked to death. Might be better to let a tech give it a shot.. though I hate to spend any more money on it at this point... :'(

It's something in the design of the 20th Shiva. Bogner agreed it was emf. They thought it was beacuse of PT lead dress or the lead routing which is why they rerouted some leads trying to cancel it out. I feel it is because of the power tube's bass layout in conjunction with the back end of the preamp output. I'm am amateur at best though. As I said it is generating an electro magnetic field which is being injected into the circuit near or at the PI outs. Do you have any experience at all with amps. If not definitely see a tech. He shouldn't charge you much at all just to see if this is the issue.

 

[derrek_clay]

I see, I see. Not sure if I'd feel comfortable trying it myself though. Haha I'd be too afraid of breaking something or getting shocked to death. Might be better to let a tech give it a shot.. though I hate to spend any more money on it at this point... :'(

It's something in the design of the 20th Shiva. Bogner agreed it was emf. They thought it was beacuse of PT lead dress or the lead routing which is why they rerouted some leads trying to cancel it out. I feel it is because of the power tube's bass layout in conjunction with the back end of the preamp output. I'm am amateur at best though. As I said it is generating an electro magnetic field which is being injected into the circuit near or at the PI outs. Do you have any experience at all with amps. If not definitely see a tech. He shouldn't charge you much at all just to see if this is the issue.

Thanks for all the great info! Beyond changing tubes, I don't have much experience with amps. I'm sure I'd be capable enough to remove the amp from the chasis and identify the caps... but like I said, I'd be afraid of getting shocked or breaking something in the process. It seems like the techs I took the amp to were simply looking for the wrong thing in the wrong place. But given my own troubleshooting discoveries, and your own experiences (with the same amp, no less), I'd say this is very likely the issue. Everything I've found seems to be congruent with your theory.

 

[glip22]

I see, I see. Not sure if I'd feel comfortable trying it myself though. Haha I'd be too afraid of breaking something or getting shocked to death. Might be better to let a tech give it a shot.. though I hate to spend any more money on it at this point... :'(

It's something in the design of the 20th Shiva. Bogner agreed it was emf. They thought it was beacuse of PT lead dress or the lead routing which is why they rerouted some leads trying to cancel it out. I feel it is because of the power tube's bass layout in conjunction with the back end of the preamp output. I'm am amateur at best though. As I said it is generating an electro magnetic field which is being injected into the circuit near or at the PI outs. Do you have any experience at all with amps. If not definitely see a tech. He shouldn't charge you much at all just to see if this is the issue.

Thanks for all the great info! Beyond changing tubes, I don't have much experience with amps. I'm sure I'd be capable enough to remove the amp from the chasis and identify the caps... but like I said, I'd be afraid of getting shocked or breaking something in the process. It seems like the techs I took the amp to were simply looking for the wrong thing in the wrong place. But given my own troubleshooting discoveries, and your own experiences (with the same amp, no less), I'd say this is very likely the issue. Everything I've found seems to be congruent with your theory.

Can you use a multi-meter and test for dc voltage. If so you can give it a try. See the 2 large ceramic disc caps to the right of the power tube base. You want to bend those slowly and carefully toward the chassis edge down. Do the one closest to the chassis first and then the other. They are black not green it looks. I could be way off but I know it helped mine allot.

 

[derrek_clay]

I'll give it a shot!

Also, racerxrated, if you can see this, I'm unable to use PMs (haven't been on the forum long enough). I have tried swapping out the PI tube and it made no difference.

 

[derrek_clay]

Just to clarify, I assume you mean these, right? (circled in purple)

And you're suggesting that I bend them down, so that the broad, circular side is facing down toward the circuit board? Am I understanding correctly?

also, any tips on how to not get electrocuted in the process? haha

 

[Racerxrated]

I'll give it a shot!

Also, racerxrated, if you can see this, I'm unable to use PMs (haven't been on the forum long enough). I have tried swapping out the PI tube and it made no difference.

Yeah, when I read the above post of what you've done I didn't see that you did that. I just swapped the PI in my Marshall and made a good amp even better. Gary knows his stuff though! Good luck!

 

[derrek_clay]

I'll give it a shot!

Also, racerxrated, if you can see this, I'm unable to use PMs (haven't been on the forum long enough). I have tried swapping out the PI tube and it made no difference.

Yeah, when I read the above post of what you've done I didn't see that you did that. I just swapped the PI in my Marshall and made a good amp even better. Gary knows his stuff though! Good luck!

Very true! The V1 and PI slots seem to have the biggest impact on tone in my amp.

 

[glip22]

Just to clarify, I assume you mean these, right? (circled in purple)

And you're suggesting that I bend them down, so that the broad, circular side is facing down toward the circuit board? Am I understanding correctly?

also, any tips on how to not get electrocuted in the process? haha

Correct. Bend them toward the circuit board but make sure they are not touching anything which is no problem. Don;t have the amp plugged in and make sure all you touch is the caps. It won't be difficult. See if it helps. If not bend them back up. They bend fairly easy. Just go slow with even pressure. Before doing this you might want to have the amp powered up and off standby. Carefully move a couple of your fingers around in the area around the caps while listening. Just in the air. See if it affects the hum. You won't get shocked. If it has an effect, bend the caps. Your body will act as a ground and should lower the hum if it is emf.

 

[derrek_clay]

Gotcha, gotcha. Haha I might use something other than my hand to bend down the caps, just in case.