Ampeg SVT-VR hum problem

[gumbystuff]

Hi all,

I was hoping to get some feedback on my Ampeg SVT-VR start up noises and constant humming. Before I take it 170 miles one way to the warranty repair shop, I thought I could get some knowledge to be sure it is not a tube problem or simple fix.

I made a short recording of the sounds and posted it here:

http://www.youtube.com/watch?v=Ya-D4T04WtI

The amp is a 2006 USA made model with only about 10 to 15 hours of play time since I bought it new. All original tubes.

I have checked the 2 rear driver tubes by exchanging them with new ones with no hum change. The chopstick test shows the preamp tube in position JW2 has a loud pop noise when tapped, so I exchanged it, but got the same noise.

The amp sounds great when turned up and the hum does not get much louder. It hums the same with or without a bass plugged in. I have tried different power circuits in different homes, a voltage regulator, power conditioners, power cords, speaker cables and speaker cabs. I tried the polarity switch in all positions and made sure the bias adjustment is correct.


Is that a 60 cycle hum I hear? Does that indicate a ground problem? Are the power up thumps normal?

I live in Oregon and do not have any experience with any authorized Ampeg repair shops. I wonder who is the best warranty repair tech for this amp?

Any advice would be appreciated.

Thanks,
Dave

[anderbass]

Has your amp always done this, or did it just suddenly start?

I cant tell how loud that standby sw. engagement pop and hum actually is from your video, but with placing a mic close enough I know I could duplicate that audio with both of my recently serviced (all-tube) SVT's.

Have you tried adjusting the amps Hum Balance pot?

[johnk_10]

i'm not sure, but your's may be one of the ones that had the 12V regulator grounding problem:

http://music-electronics-forum.com/t15670/

mine's a late 2007 (Vietnam one) and didn't, but you can easily determine if your's does by opening it up or taking it to a tech that is familiar with them.

[Toolmybass]

Originally Posted by gumbystuff

Hi all,

I was hoping to get some feedback on my Ampeg SVT-VR start up noises and constant humming. Before I take it 170 miles one way to the warranty repair shop, I thought I could get some knowledge to be sure it is not a tube problem or simple fix.

I made a short recording of the sounds and posted it here:

http://www.youtube.com/watch?v=Ya-D4T04WtI

The amp is a 2006 USA made model with only about 10 to 15 hours of play time since I bought it new. All original tubes.

I have checked the 2 rear driver tubes by exchanging them with new ones with no hum change. The chopstick test shows the preamp tube in position JW2 has a loud pop noise when tapped, so I exchanged it, but got the same noise.

The amp sounds great when turned up and the hum does not get much louder. It hums the same with or without a bass plugged in. I have tried different power circuits in different homes, a voltage regulator, power conditioners, power cords, speaker cables and speaker cabs. I tried the polarity switch in all positions and made sure the bias adjustment is correct.


Is that a 60 cycle hum I hear? Does that indicate a ground problem? Are the power up thumps normal?

I live in Oregon and do not have any experience with any authorized Ampeg repair shops. I wonder who is the best warranty repair tech for this amp?

Any advice would be appreciated.

Thanks,
Dave

DO NOT take this to Ampeg (or an Ampeg warranty place)for repair. Especially because it a US model. All they do now is ship them overseas and replace the guts with inferior parts. I was TOLD this outright when i bought mine. If you do have to take it make sure they GUARANTEE you that it doesnt leave the store and or state!.... Find out through your closest major store on someone they use locally to deal with TUBE head service and eat the cost. Unless you think you amp will be worth the same amount with overseas guts in it...instead of USA.

It could be a simple adjustment.

I hope this helps
TMB

[Jerrold Tiers]

First, NEVER SAY ANYTHING THAT IMPLIES "AMPEG" EXISTS. it does not.

"AMPEG" is just a brand name owned by "Loud Technologies Inc"..

When you say what "Ampeg" will do, you really mean what "Loud" will do.

They had that service plan back a ways, everything was supposed to go to Shanghai.

But you wouldn't get YOUR unit back, ever.... (or your $300 of new tubes) you'd get a replacement unit from current production, OR a refurbished as first choice if available. Nobody thought about the serial number issue..... I don't know how that worked.

That plan, put forth by Jamie Engen, was an abject failure, and Loud had to backtrack on it. Is it being re-established now?

[johnk_10]

Originally Posted by Toolmybass

DO NOT take this to Ampeg (or an Ampeg warranty place)for repair. Especially because it a US model. All they do now is ship them overseas and replace the guts with inferior parts. I was TOLD this outright when i bought mine.
TMB

i don't know who told you that, but every authorized ampeg warranty center that i've dealt with or talked to repairs/services them in house.

maybe if it needed a complete poweramp PCB assembly, but i still doubt it, since it's so much cheaper to just ship a PCB than the whole amp.

[Toolmybass]

Originally Posted by johnk_10

i don't know who told you that

Umm the authorized Ampeg dealer i bought the amp from. Which happens to be the biggest chain of music stores in Canada. So i will take their word for it.

[Toolmybass]

Originally Posted by Jerrold Tiers

First, NEVER SAY ANYTHING THAT IMPLIES "AMPEG" EXISTS. it does not.

"AMPEG" is just a brand name owned by "Loud Technologies Inc"..

When you say what "Ampeg" will do, you really mean what "Loud" will do.

They had that service plan back a ways, everything was supposed to go to Shanghai.

But you wouldn't get YOUR unit back, ever.... (or your $300 of new tubes) you'd get a replacement unit from current production, OR a refurbished as first choice if available. Nobody thought about the serial number issue..... I don't know how that worked.

That plan, put forth by Jamie Engen, was an abject failure, and Loud had to backtrack on it. Is it being re-established now?

Exactly +1

[johnk_10]

Originally Posted by Toolmybass

Umm the authorized Ampeg dealer i bought the amp from. Which happens to be the biggest chain of music stores in Canada. So i will take their word for it.

you are certainly entitled to, but not a single one in the USA that i've spoken to has ever said that.

[Toolmybass]

Originally Posted by johnk_10

you are certainly entitled to, but not a single one in the USA that i've spoken to has ever said that.

Umm if you look above and read the quote by Jerrold, this is common knowledge....If you can also read the last line where it says he used to work for Ampeg. But to believe otherwise "you are certainly entitled to"

[derridiandrift]

Originally Posted by gumbystuff

Is that a 60 cycle hum I hear? Does that indicate a ground problem? Are the power up thumps normal?

Dave, this is interesting because the very first VR I bought was a Vietnam model and it had the very same problem.

I bought it in late December 2009 on a Thursday, used it on a weekend of gigs and returned it (to Long & McQuade) on a Monday as a result of the noise it was making. They turned it over to the local authorized repair shop. About five weeks later it came back to the store and I was ready to buy it if it worked properly. It was the same chassis (I checked the serial number) but I don't know what the repair place did, or if they sent it out of the country to have the boards replaced. That seems a bit silly when the local repair shop can do the same thing without having to pay for all that shipping of the rest of the chassis.

Anyway, when the amp came back it had a different problem, but the initial noise problem was fixed. I didn't buy that one. I went to a different L&M store with the intention of buying the unit they had on the floor. This one wouldn't come out of standby for the longest time, but when it finally did it sounded fine. I didn't know about the low-voltage mains mod at the time. The unit was probably fine otherwise but I didn't buy it because the product didn't inspire much confidence in me.

Intent on eventually getting a VR, I've since bought a used USA VR and I've done the low-voltage mains mod. I've had no issues so far, but I'm going to stay alert to this ground loop issue.

I wonder if we should start a SVT-VR "club" like Jimmy's fliptop club. We can keep each other up to speed on issues that come up and how to fix them. Maybe this isn't necessary.

Regardless of its issues, I believe the SVT-VR to be one of the very best sounding amps currently in production. Too bad LOUD is struggling to get their act together with respect to assembly quality control.

[gumbystuff]

Originally Posted by anderbass

Has your amp always done this, or did it just suddenly start?

I cant tell how loud that standby sw. engagement pop and hum actually is from your video, but with placing a mic close enough I know I could duplicate that audio with both of my recently serviced (all-tube) SVT's.

Have you tried adjusting the amps Hum Balance pot?

anderbass:
It had very low noise when new and recently started being more noisy. I do not have the equipment to check the balance myself.
Thanks

[derridiandrift]

Originally Posted by gumbystuff

Hi all,

I have checked the 2 rear driver tubes by exchanging them with new ones with no hum change. The chopstick test shows the preamp tube in position JW2 has a loud pop noise when tapped, so I exchanged it, but got the same noise.

Good that you went through the process of checking the tubes. I had a serious noise problem with the 12AX7 driver tube in the power amp section at the back of my SVT-CL. Crazy thing though, this tube worked fine in the preamp of another head. I didn't understand why this was happening, but after switching out that tube the amp worked fine. I don't have a tube tester, so I just threw out the offending 12AX7. It happened to be a Sovtek tube that came in another amp, and I'm not a big raging fan of Sovtek tubes anyway so it was no big loss. It just seems odd to me that a tube can appear to work in one application but not in another.

[gumbystuff]

Originally Posted by johnk_10

i'm not sure, but your's may be one of the ones that had the 12V regulator grounding problem:

http://music-electronics-forum.com/t15670/

mine's a late 2007 (Vietnam one) and didn't, but you can easily determine if your's does by opening it up or taking it to a tech that is familiar with them.

johnk,

Thanks for the link. It mentions that the problem goes away after inserting a cable into the input jack, but mine has the same hum with or without cable in jack.

I checked the DI output for the first time and it has a very low output level even with it's volume all the way up. My Avalon U5 and SWR M2 DI's have a much higher output level. I wonder if it is a malfunctioning DI circuit? The hum is audible through the DI as well. Is there a specific tube to check for the DI?

[gumbystuff]

Originally Posted by Toolmybass

DO NOT take this to Ampeg (or an Ampeg warranty place)for repair. Especially because it a US model. All they do now is ship them overseas and replace the guts with inferior parts. I was TOLD this outright when i bought mine. If you do have to take it make sure they GUARANTEE you that it doesnt leave the store and or state!.... Find out through your closest major store on someone they use locally to deal with TUBE head service and eat the cost. Unless you think you amp will be worth the same amount with overseas guts in it...instead of USA.

It could be a simple adjustment.

I hope this helps
TMB

Toolmybass,

Thanks for the heads up.

[gumbystuff]

Originally Posted by derridiandrift

Good that you went through the process of checking the tubes. I had a serious noise problem with the 12AX7 driver tube in the power amp section at the back of my SVT-CL. Crazy thing though, this tube worked fine in the preamp of another head. I didn't understand why this was happening, but after switching out that tube the amp worked fine. I don't have a tube tester, so I just threw out the offending 12AX7. It happened to be a Sovtek tube that came in another amp, and I'm not a big raging fan of Sovtek tubes anyway so it was no big loss. It just seems odd to me that a tube can appear to work in one application but not in another.

derridiandrift,

Thanks for the input. I will swap all of the preamp tubes next and I am going to also check the 12AX7 in the power section as per Jerrold Tiers recommendation.

[johnk_10]

Originally Posted by Toolmybass

Umm if you look above and read the quote by Jerrold, this is common knowledge....If you can also read the last line where it says he used to work for Ampeg. But to believe otherwise "you are certainly entitled to"

whatever.
IMO, it's common knowledge that is 4-5 years old.

[vinxbass]

Originally Posted by Toolmybass

DO NOT take this to Ampeg (or an Ampeg warranty place)for repair. Especially because it a US model. All they do now is ship them overseas and replace the guts with inferior parts. I was TOLD this outright when i bought mine. If you do have to take it make sure they GUARANTEE you that it doesnt leave the store and or state!.... Find out through your closest major store on someone they use locally to deal with TUBE head service and eat the cost. Unless you think you amp will be worth the same amount with overseas guts in it...instead of USA.

It could be a simple adjustment.

I hope this helps
TMB

This sounds really far fetched. Why wouldn't a company guarantee their work, or at least work on their own products to make them servicable again. I don't get it.

[Hoss]

Originally Posted by gumbystuff

It mentions that the problem goes away after inserting a cable into the input jack, but mine has the same hum with or without cable in jack.

Its NOT the input jack on the front panel! What they mean is: It goes away when something plugged into the Power Amp In Jack. This one is located on the back panel of your amp.
When something plugged into that Jack - the connection between preamp and poweramp is cut.
The hum is generated by the preamp. So when connection internally cut by plugging into the Power amp in - the hum is gone.

[Toolmybass]

Originally Posted by vinxbass

This sounds really far fetched. Why wouldn't a company guarantee their work, or at least work on their own products to make them servicable again. I don't get it.

Read above. The part that talks about another company running the "name" Ampeg. Not all companies have very good warranty practices after taking over someone elses product.

Do they not ship the "common knowledge books" to CA?.... Im joking of course.