Ampeg Heritage 50th Anniversary SVT issue

[OkayistBassist]

I just ordered a second 50th Anniversary SVT today (along with a 212AV). My first one was quiet. Hopefully this one is as well!

 

[Patrice B]

Just to clarify: The information posted in this thread about getting rid of noise in various SVT models is helpful to other SVT users and I appreciate it. But this thread is specifically about the 50th Anniversary SVT amp head, not other current or discontinued SVT models that have different designs and noise issues. The apparent design defect/issue that Psionic Audio identified in the linked video specifically concerns the 50th Anniversary SVT's circuit layout, in which the AC voltage on the standby switch is too close to the preamp circuit board and induces the constant buzz that concerns me. Psionic Audio explained that when he detached the standby switch and moved it away from the preamp board the buzz went away.

As such, the identified buzz for at least some 50th Anniversary SVTs is likely not the result of poor preamp tubes, poor preamp tube pin connections, poor tube bias, etc., and they are probably not effective solutions for that issue with this model amp. (But, I may try them anyway because I have been wrong plenty of times before.)

Psionic Audio's suggested fixes for the issue with this amp include disconnecting the AC to the standby switch on the face of the amp, leave the switch in place for cosmetic reasons, and install a new standby switch on the back of the SVT, away from the preamp circuit board. Alternatively, using the existing standby switch to trigger a relay installed to operate the standby function, so that the voltage to the standby switch to operate the relay is much less than the 120 AC volts and does not induce a buzz.

Others have suggested fabricating a metal shielding box to put around the standby switch to reduce its effect on the preamp board of the SVT-VR. Ampeg SVT-VR Ch 2 Buzz/Hum - Music Electronics Forum

Anyone have a better idea?

Sorry for disturbing your thread!

 

[denton57]

Wonder why some have this issue and others do not?

 

[Wasnex]

Honestly the level of hum demonstrated throughout most of the Psionic video seems lower than most of the SVTs I have played...including the two vintage amps I own. I am not saying it's not a design flaw, only that it does not seem all that unusual. Every SVT I have ever played has had some residual hum. But you may not notice it over the whirling noise from the fan.

However, if the hum is super loud like at this point in the video:

Then yes there is a problem. However, keep in mind the video is exaggerating the noise level at this point by cranking up the gain on the recording interface. That is not representative of the level of hum you should hear in the room with this amp

Why do some complain while others don't? Perhaps some amps have more hum than others. Or perhaps some people are less sensitive to the noise. Or perhaps it has something to do with the speaker being used. If you use a speaker with a tweeter and/or a high sensitivity rating, you are more likely to hear residual hum.

The Ampeg 810 has a pretty high sensitivity rating, but I perceive it as a rather dark sounding cab (no tweeter). So if the energy from the hum is focused down near 60 or 120 hz, it will probably be fairly noticeable with an 810. However, the buzz in video is more of a wiry, high-frequency noise. A cab with a tweeter will probably bring out the wiry quality even more than an 810.

 

[bobyoung53]

Oh, an another source of buzz (and what a buzz!) I just experimented myself. Loos input jack that won’t short once cable disconnected. I had to use a pair pliers to tighten the metal tabs on the 0dB input jack a few minutes ago. Scared the hell of me as I started the amp @full blast!! BZZZZZZ x 300w!

A little squirt of Deoxit too (very little!).

View attachment 4737289

I hate those new input jacks, I have one in a 90's B-15 and they r at least mine doesn't grip the jack very tightly. The 70's Ampegs really grip the jack.

 

[bobyoung53]

Just to clarify: The information posted in this thread about getting rid of noise in various SVT models is helpful to other SVT users and I appreciate it. But this thread is specifically about the 50th Anniversary SVT amp head, not other current or discontinued SVT models that have different designs and noise issues. The apparent design defect/issue that Psionic Audio identified in the linked video specifically concerns the 50th Anniversary SVT's circuit layout, in which the AC voltage on the standby switch is too close to the preamp circuit board and induces the constant buzz that concerns me. Psionic Audio explained that when he detached the standby switch and moved it away from the preamp board the buzz went away.

As such, the identified buzz for at least some 50th Anniversary SVTs is likely not the result of poor preamp tubes, poor preamp tube pin connections, poor tube bias, etc., and they are probably not effective solutions for that issue with this model amp. (But, I may try them anyway because I have been wrong plenty of times before.)

Psionic Audio's suggested fixes for the issue with this amp include disconnecting the AC to the standby switch on the face of the amp, leave the switch in place for cosmetic reasons, and install a new standby switch on the back of the SVT, away from the preamp circuit board. Alternatively, using the existing standby switch to trigger a relay installed to operate the standby function, so that the voltage to the standby switch to operate the relay is much less than the 120 AC volts and does not induce a buzz.

Others have suggested fabricating a metal shielding box to put around the standby switch to reduce its effect on the preamp board of the SVT-VR. Ampeg SVT-VR Ch 2 Buzz/Hum - Music Electronics Forum

Anyone have a better idea?

Welcome to TalkBass.

 

[bobyoung53]

Honestly the level of hum demonstrated throughout most of the Psionic video seems lower than most of the SVTs I have played...including the two vintage amps I own. I am not saying it's not a design flaw, only that it does not seem all that unusual. Every SVT I have ever played has had some residual hum. But you may not notice it over the whirling noise from the fan.

However, if the hum is super loud like at this point in the video:

Then yes there is a problem. However, keep in mind the video is exaggerating the noise level at this point by cranking up the gain on the recording interface. That is not representative of the level of hum you should hear in the room with this amp

Why do some complain while others don't? Perhaps some amps have more hum than others. Or perhaps some people are less sensitive to the noise. Or perhaps it has something to do with the speaker being used. If you use a speaker with a tweeter and/or a high sensitivity rating, you are more likely to hear residual hum.

The Ampeg 810 has a pretty high sensitivity rating, but I perceive it as a rather dark sounding cab (no tweeter). So if the energy from the hum is focused down near 60 or 120 hz, it will probably be fairly noticeable with an 810. However, the buzz in video is more of a wiry, high-frequency noise. A cab with a tweeter will probably bring out the wiry quality even more than an 810.

He's probably got a point, all the older SVT's had the standby on the back of the head. But saying that I can hardly hear the buzz and turning it up with a mic in front of the speaker is not realistic. SVT's are very high gain and I don't think i've ever heard a completely dead quiet SVT and I've been using them for 47 years now. That fan in that thing is very quiet. I would like to hear that in real life, you cannot judge how loud it is in a video.

 

[Robal]

He's probably got a point, all the older SVT's had the standby on the back of the head. But saying that I can hardly hear the buzz and turning it up with a mic in front of the speaker is not realistic. SVT's are very high gain and I don't think i've ever heard a completely dead quiet SVT and I've been using them for 47 years now. That fan in that thing is very quiet. I would like to hear that in real life, you cannot judge how loud it is in a video.

There may be variation from SVT to SVT because, among other things, the lead dress/position of the AC wires connecting to the standby switch may be different and mitigate the buzz -- but wires can move around and then buzz can the get much worse. That was suggested by the tech in Ampeg SVT-VR Ch 2 Buzz/Hum - Music Electronics Forum

In my case the buzz for my 50th Anniversary SVT amp is sufficiently loud that when I raised the issue with Ampeg Technical Support it was immediately acknowledged by TS and I was advised to return the amp to the vendor. That's what Psionic Audio said was the resolution for the SVT's buzz he diagnosed in the linked video. I doubt Ampeg TS would say return the amp -- which potentially entails the expense of shipping an 85 pound amp among the customer, vendor, and Ampeg -- if this a non-issue. Also, when the SVT's preamp is bypassed, the tube power amp section has no hum, buzz, or other noise issue at all on my amp. Absent the buzz, the preamp section is not microphonic or noisey either. If you play live, or with a cab that rolls off the high, you probably won't notice it much. If you want to record with it, you can't get rid of it so easily (besides muting the mic or riding a fader).

I tried to raise two basic points with my posts. First, what good fixes are there to mitigate or eliminate the buzz issue for this model SVT (which Ampeg Technical Support acknowledges can warrant returning the amp to the vendor)? Second, why doesn't Ampeg Technical Support have a fix for it or even appear to be working toward a fix for it on Ampeg's most expensive, flagship tube amp?

 

[seamonkey]

I tried to raise two basic points with my posts. First, does anyone have a good solution to the buzz issue for this model SVT that Ampeg Technical Support acknowledges justifies returning the amp to the vendor? Second, why doesn't Ampeg (owned by MI titan Yamaha) have a fix for it or even appear to be working toward a fix for it?

I doubt half the people who buy this even recognize it as a problem.
Psionic Audio has a great solution. Add a relay. It routes the high voltage wires away from the pre-amp, and any extra sensitive tubes or circuitry in the pre-amp.

Why Ampeg/Yamaha don't recognize it as a fixable problem is if they did then they would likely have to recall them from people who don't even know it, and/or offer free fixes for years to come. Same reason they have so many board revisions on the pf line of amps.

 

[bobyoung53]

There may be variation from SVT to SVT because, among other things, the lead dress/position of the AC wires connecting to the standby switch may be different and mitigate the buzz -- but wires can move around and then buzz can the get much worse. That was suggested by the tech in Ampeg SVT-VR Ch 2 Buzz/Hum - Music Electronics Forum

In my case the buzz for my 50th Anniversary SVT amp is sufficiently loud that when I raised the issue with Ampeg Technical Support it was immediately acknowledged by TS and I was advised to return the amp to the vendor. That's what Psionic Audio said was the resolution for the SVT's buzz he diagnosed in the linked video. I doubt Ampeg TS would say return the amp -- which potentially entails the expense of shipping an 85 pound amp among the customer, vendor, and Ampeg -- if this a non-issue. Also, when the SVT's preamp is bypassed, the tube power amp section has no hum, buzz, or other noise issue at all on my amp. Absent the buzz, the preamp section is not microphonic or noisey either. If you play live, or with a cab that rolls off the high, you probably won't notice it much. If you want to record with it, you can't get rid of it so easily (besides muting the mic or riding a fader).

I tried to raise two basic points with my posts. First, what good fixes are there to mitigate or eliminate the buzz issue for this model SVT (which Ampeg Technical Support acknowledges can warrant returning the amp to the vendor)? Second, why doesn't Ampeg Technical Support have a fix for it or even appear to be working toward a fix for it on Ampeg's most expensive, flagship tube amp?

I did read where you bypassed the preamp. If I read your post correctly, they want you to return it to the vendor, in exchange for another head? And they acknowledge it but also that they don't have a fix for it and aren't even trying? Weird, that makes me think they do have a solution for it but don't want it out in the open for some reason (hmmm). I thought I heard a little 120 cycle buzz, is that the problem?

 

[Wasnex]

There may be variation from SVT to SVT because, among other things, the lead dress/position of the AC wires connecting to the standby switch may be different and mitigate the buzz -- but wires can move around and then buzz can the get much worse. That was suggested by the tech in Ampeg SVT-VR Ch 2 Buzz/Hum - Music Electronics Forum

In my case the buzz for my 50th Anniversary SVT amp is sufficiently loud that when I raised the issue with Ampeg Technical Support it was immediately acknowledged by TS and I was advised to return the amp to the vendor. That's what Psionic Audio said was the resolution for the SVT's buzz he diagnosed in the linked video. I doubt Ampeg TS would say return the amp -- which potentially entails the expense of shipping an 85 pound amp among the customer, vendor, and Ampeg -- if this a non-issue. Also, when the SVT's preamp is bypassed, the tube power amp section has no hum, buzz, or other noise issue at all on my amp. Absent the buzz, the preamp section is not microphonic or noisey either. If you play live, or with a cab that rolls off the high, you probably won't notice it much. If you want to record with it, you can't get rid of it so easily (besides muting the mic or riding a fader).

I tried to raise two basic points with my posts. First, what good fixes are there to mitigate or eliminate the buzz issue for this model SVT (which Ampeg Technical Support acknowledges can warrant returning the amp to the vendor)? Second, why doesn't Ampeg Technical Support have a fix for it or even appear to be working toward a fix for it on Ampeg's most expensive, flagship tube amp?

I think there is no Ampeg solution, because the solution is cost prohibitive, and most people probably don't even notice.

The Psionic video mentioned the VR has the same issue, and suggests the 50th AV uses the same output section. I suspect the AV and VR also use the same preamp architecture and the AV just trades out the values of a few components to give channel 2 it's unique voice.

The CL probably has the same problem to some extent, but the CL uses a single channel preamp, so the circuit board may not extend all the way across the front panel. Maybe the sensitive components in the preamp are far enough from the switches that it's not as noticeable.

Ampeg probably can't use Psionic's proposed solutions. Mass produced amps must be certified and moving the standby or adding a relay would probably invalidate the certification.

The only part I find perplexing is Ampeg's willingness to send replacement heads that will likely have the same exact problem. Shipping on a big, heavy amp is not exactly cheap, and some amps will incur damage in transit.

Pretty sure I have seen posts from multiple people who asked for a replacement and had to send it back as well, because the replacement had the same exaxt problem.

IMHO if you want an Ampeg for recording, try a PF50T. The early ones had a hum problem, but that has been resolved. If you buy used, the fix is relatively easy: Ampeg PF-50T Humbuster | TalkBass.com

 

[Robal]

I think there is no Ampeg solution, because the solution is cost prohibitive, and most people probably don't even notice.

Sure, many people will not notice the noise problem. I measured the noise with the standby on and off; and standby off measured 10+ db higher than standby on. That means the noise level with standby off, which is when the AC buzz appears, is more than twice as loud as with standby off. (This is measured with both channel volumes at 0, so the only added noise is the AC buzz; also the amp's fan noise is not a factor in the measurement because the fan stays on with or without standby off.)

As I said in a prior post, if Ampeg's position is that it will continue to release 50th Anniversary SVT amps with this buzz issue and won't develop a fix for it, it is rather disappointing for a company with the resources of Ampeg/Yamaha.

If I keep this SVT and can get it fixed, I will post here about the outcome for those 50th Anniversay SVT users who care about the standby switch AC buzz.

 

[Patrice B]

This user on Music Electronics Forum has built a little shielded thing to tame the buzz:

Ampeg SVT-VR Ch 2 Buzz/Hum - Music Electronics Forum

The buzz is present on some SVT’s because 120 volts AC is right on top of the preamp board. You could also try to route the standby cables differently…

 

[Wasnex]

Sure, many people will not notice the noise problem. I measured the noise with the standby on and off; and standby off measured 10+ db higher than standby on. That means the noise level with standby off, which is when the AC buzz appears, is more than twice as loud as with standby off. (This is measured with both channel volumes at 0, so the only added noise is the AC buzz; also the amp's fan noise is not a factor in the measurement because the fan stays on with or without standby off.)

As I said in a prior post, if Ampeg's position is that it will continue to release 50th Anniversary SVT amps with this buzz issue and won't develop a fix for it, it is rather disappointing for a company with the resources of Ampeg/Yamaha.

If I keep this SVT and can get it fixed, I will post here about the outcome for those 50th Anniversay SVT users who care about the standby switch AC buzz.

This user on Music Electronics Forum has built a little shielded thing to tame the buzz:

Ampeg SVT-VR Ch 2 Buzz/Hum - Music Electronics Forum

The buzz is present on some SVT’s because 120 volts AC is right on top of the preamp board. You could also try to route the standby cables differently…

View attachment 4740338

IMHO if the shield works, make sure and send a link to the thread to Ampeg. I believe the PF50T humbuster thread led to a change in how the amp is made. Ampeg essentially compied the humbuster mod. I believe they also fixed quite a few amps under warranty.

Also if "nevetslab" from the thread is an authorized Ampeg warranty center, he may be able to advocate for you to reduce/eliminate cost.

 

[Patrice B]

@TechnoTurian and @Robal

Just a quick update:

As you may know, the SVT-AV has gain and master, the Heritage only gain so « master « is always full open.

Yesterday, I tried, as suggested in some threads, running master dimed and adjusting volume with gain. There is now indeed a « buzz » with my SVT-AV. Now, is it obnoxious for me? I don’t know. I cannot tell if it’s as loud as the published videos in this thread neither…

For reference, the buzz on my old V4 is louder than that so maybe I’m not the best person to ask.

Anyway, as the Heritage has no master, more noise is probably expected. However, how much is acceptable? This neither I can’t answer…

Any updates on your side?

 

[agedhorse]

This user on Music Electronics Forum has built a little shielded thing to tame the buzz:

Ampeg SVT-VR Ch 2 Buzz/Hum - Music Electronics Forum

The buzz is present on some SVT’s because 120 volts AC is right on top of the preamp board. You could also try to route the standby cables differently…

View attachment 4740338

If that's a brass sheet shield, it will have no effect on the hum because brass is essentially transparent to LF EMF. I would beware of claims that go against the physics. It would have to be some form of steel, the higher the permeability the more effective.

There's a lot of BS claims and dubious measurements masquerading as gospel, yet when a knowledgeable person investigates these claims, it becomes obvious that they are bunk. Lots of perfectly good amps get jacked up by such DIY repair attempts.

 

[Patrice B]

If that's a brass sheet shield, it will have no effect on the hum because brass is essentially transparent to LF EMF. I would beware of claims that go against the physics. It would have to be some form of steel, the higher the permeability the more effective.

There's a lot of BS claims and dubious measurements masquerading as gospel, yet when a knowledgeable person investigates these claims, it becomes obvious that they are bunk. Lots of perfectly good amps get jacked up by such DIY repair attempts.

Sorry @agedhorse , my intention wasn’t to perpetuate bad information (but I did!) .Mea culpa… Like you’ve said in another thread, some things on this forum (Music Electronics Forum) had to be taken with a grain of salt I guess…

 

[Robal]

If I keep this SVT and can get it fixed, I will post here about the outcome for those 50th Anniversary SVT users who care about the standby switch AC buzz.

Good news. I did get my Heritage 50th SVT fixed by a local amp tech in North Hollywood, CA. Now the loud buzz is not an issue, even in a quiet studio setting. I measured the noise db difference between standby on and standby off and it is much less that the 10+ db I previously measured.

 

[sgiacomo]

Good news. I did get my Heritage 50th SVT fixed by a local amp tech in North Hollywood, CA. Now the loud buzz is not an issue, even in a quiet studio setting. I measured the noise db difference between standby on and standby off and it is much less that the 10+ db I previously measured.

Cool. Do you know what the tech did to fix? I have an 50th Anniversary SVT arriving today.

 

[Richhillbass]

I finally got mine today, but I am wondering about the fan noise. While in a band context it surely is no problem, at home it sounds a bit like a jet plane. Is this normal or should I get it fixed?

Thats close if not same as mine- However a tick tick sound on mine of fan blade nicking metal screen -Ampeg sent new fan...all better.......I am using this amp in pit of Grease show (ya excessive maybe but man it sounds so good...and it was amp in car from night before !)