I cant say, besides my experience and few of the others posting here, does this 50th anniversary model have a bad reputation?
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Issues with the Ampeg Heritage 50th Anniversary SVT
- Thread starter thedovewarlord
- Start date
The first one I bought had shipping issues but the second one, man oh man is it good.
Mine makes noise, not exactly like that, but it does, compared to my V4b Reissue, nothing you'll hear on a gig. I'm more interested in hearing if someone actually has one that's dead quiet.
i've owned two magnavox era SVTs - both dead quiet. something is up with these new ones, IMHO.
It's interesting (or odd I suppose) what he says how they borrowed the standby circuit from the CL but it only makes noise on the VR and 50th. Wonder why it doesn't buzz on the CL. And apparently only some of the 50th anniversary versions buzz so it's not even a consistent problem there either.
Supposedly one of the front panel circuit cards is too close to the Standby switch. The amount of hum appears to vary from amp to amp. It's claimed this was a flaw on the VR that apparently was carried over into the 50thAV. These opinion were expressed in a YouTube video some tech did.
I have never come across a vintage SVT that was dead quiet, so your's are a bit extraordinary IMHO. My 87 Skunk is the quietest I have ever played, but it still has some residual hum. My 69 has a bit more hum than the Skunk, but it's barely noticeable over the roar of the fan. From what I remember, the MTI I bought (new) in the early 80s split the difference between Skunk and the 69.
Legacy TB member Cerrem said the hum problem in the vintage amps is due ground loops in the preamp. For the record, the power amp in my 69 is dead quite if I short out the preamp feed.
Supposedly the problem can be successfully mitigated, but it involves cutting traces and redoing the ground scheme in the preamp. This involves a level of skill that is significantly beyond me...and it's also a lot of work.
By dead quiet I mean aside from the (essentially inaudible ) fan there was no discernible sound when standing next to the amp at idle.
I'm having the same problem as the op. When I turn on the standby switch after having let it warm up for 10 minutes, there's a big bunch of pops that is soooper loud. I'm trouble shooting further, I opened the back and found wires touching tubes and loose screws on the fan (1 was missing too, who knows where it is), got things secured a bit but still having the same trouble. I took it to a guy who couldn't get to it right away and let it sit about 3 weeks, then when he plugged it in he couldn't replicate the problem and said he saw nothing wrong with the wiring, so I took it home, played it a few days, and the problem is back. I may be able to mediate for it by turning ALL knobs to zero before turning the standby switch on, and letting the vomit happen for a few seconds before turning back up (so far I can play it after about 15 seconds of noise…..before I took it into the shop the noise wasn't stopping so I don't know how long this will last), but I shouldn't have to do this on an amp made in 2019. When it's not screwing up it's the most fabulous amp I've ever played, but I'm scared to gig with it now. I bought it used so warranty's not an option. Just kind of sad in my heart. Really hoping someone else has figured out what this is and can point me in the right direction.
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Sorry you're dealing with this. Since you bought it used, best advice I can give you is take it to a certified Ampeg repair technician. SVTs are supposed to be bullet proof (mine are) and not all that complicated. Whatever the problem is, it's surely fixable. Plenty of knowledgeable people here too who might be able to offer some advice.
There isn't a single answer to this issue, numerous things can cause popping. Don't worry, it can be fixed. A tech with experience with SVT's is best. As suggested, try an Ampeg service center.
It could be a tube. These are quick and easy things to try first. There are tubes inside the top chassis, and tubes in the bottom chassis that you can see. Start by reseating them. If the tubes slide in and out too easily, the tube socket contacts could need re-tensioning. This involves carefully tightening the contact. If that doesn't help, change out the small tubes one at a time.
Reseat all the wire connectors. They are in the pre as well as the power amp.
If the issue persists, separate the pre and power amp signals and try to determine if the noise is in the pre or the power amp. Take the preamp out signal from the back of the amp and with an instrument cable, feed it into another amp. Listen for the noise coming out of the other amp. Similarly, take the preamp out from another amp and plug it into the SVT's power amp. See if the problem is in the power amp. Once you know which part has the noise, further isolation will be required. It could be a bad solder joint, it could be a component. The tech would have to trace the signal to identify where in the signal path the noise is originating.
@Thatguy78 If the volume and tone controls mitigate the problem, the noise is being injected somewhere in the preamp. It could be a tube problem, but it could be lot's of other things as well. It's possible the noise is being injected into the preamp, but the source of noise is not in the preamp. Also intermittent problems are very difficult to troubleshoot.
If you don't have an electronics background, about all you can do before sending the amp to a tech is swap out tubes and do a visual inspection to see if you can find something super obvious. However, this amp has close to 700 volts inside, so it's a bit dangerous for you to go poking around. For the safety of you and the amp, it's a better idea to send it to an expert IMHO.
If you want to try swapping at a few tubes, it would be helpful if you could narrow the location of the problem down a bit. This can be done if you know the signal path. The idea is you adjust the controls to determine which controls have an impact. Then you replace the tube stage(s) that immediately precede the first control that impacts the problem.
The original SVTs used three 12DW7 in channel one, one 12AX7 in channel two, and one 6C4 to blend the two channels. All of these tube types have two triodes, except the 6C4 which only has one triode. All nine triodes are used.
A 12DW7 is equivalent to one 12AX7 triode and one 12AU7 triode. A 6C4 is equivalent to one 12AU7 triode.
The SVT VR is pretty much functionally identical to a vintage SVT, but it does not use the same signal path. In a vintage amp, the signal flows in channel 1 sequentially through the two triodes in V1, then the two triodes in V3 and finally the two triodes in V4. V2 is the 12AX7 used for Channel 2.
My belief is the Heritage 50th AV has the same signal path as the VR, but a few components are changed. I have access to the VR schematics, but have not seen 50th AV schematics, so this info could be wrong.
In the SVT VR the signal in channel 1 flows in and out of various 12AX7 and 12AU7 tubes. Here's the order: V1a, V2b, V2a, V3b, V3a, V4b. Since the VR uses three 12AX7s and two 12AU7s, ten triodes are available, but only 9 are used, just like the vintage amps. The unused triode is V1b. V5a and V5b make up the gain stages of channel 2, and V4a fills the role of the 6C4.
Signal Paths:
Channel 1 (Input Jack Network), (V1a, V2b), (Ultra Low and Ultra High), (Volume), (V2a), (Bass and Treble), [(V3b, V3a, V4b), Mid**]--->(V4a mixer)
** The Mid control circuit is connected across V3b and V4b.
Channel 2 (Input Jack Network), (V5a), (Ultra Low and Ultra High), (Volume), (V5b), (Bass and Treble)--->(V4a mixer)
Both Channels are mixed at the input of V4a.
Examples
If the Channel 1 Volume control has an impact on the sound, the problem may be V1a or V2b. Replace one tube at a time.
If the problem is in Channel 2, replace V5.
If the preamp controls have an impact on the noise, but changing tubes does not fix the problem...take the amp to a good tech.
If you don't have an electronics background, about all you can do before sending the amp to a tech is swap out tubes and do a visual inspection to see if you can find something super obvious. However, this amp has close to 700 volts inside, so it's a bit dangerous for you to go poking around. For the safety of you and the amp, it's a better idea to send it to an expert IMHO.
If you want to try swapping at a few tubes, it would be helpful if you could narrow the location of the problem down a bit. This can be done if you know the signal path. The idea is you adjust the controls to determine which controls have an impact. Then you replace the tube stage(s) that immediately precede the first control that impacts the problem.
The original SVTs used three 12DW7 in channel one, one 12AX7 in channel two, and one 6C4 to blend the two channels. All of these tube types have two triodes, except the 6C4 which only has one triode. All nine triodes are used.
A 12DW7 is equivalent to one 12AX7 triode and one 12AU7 triode. A 6C4 is equivalent to one 12AU7 triode.
The SVT VR is pretty much functionally identical to a vintage SVT, but it does not use the same signal path. In a vintage amp, the signal flows in channel 1 sequentially through the two triodes in V1, then the two triodes in V3 and finally the two triodes in V4. V2 is the 12AX7 used for Channel 2.
My belief is the Heritage 50th AV has the same signal path as the VR, but a few components are changed. I have access to the VR schematics, but have not seen 50th AV schematics, so this info could be wrong.
In the SVT VR the signal in channel 1 flows in and out of various 12AX7 and 12AU7 tubes. Here's the order: V1a, V2b, V2a, V3b, V3a, V4b. Since the VR uses three 12AX7s and two 12AU7s, ten triodes are available, but only 9 are used, just like the vintage amps. The unused triode is V1b. V5a and V5b make up the gain stages of channel 2, and V4a fills the role of the 6C4.
Signal Paths:
Channel 1 (Input Jack Network), (V1a, V2b), (Ultra Low and Ultra High), (Volume), (V2a), (Bass and Treble), [(V3b, V3a, V4b), Mid**]--->(V4a mixer)
** The Mid control circuit is connected across V3b and V4b.
Channel 2 (Input Jack Network), (V5a), (Ultra Low and Ultra High), (Volume), (V5b), (Bass and Treble)--->(V4a mixer)
Both Channels are mixed at the input of V4a.
Examples
If the Channel 1 Volume control has an impact on the sound, the problem may be V1a or V2b. Replace one tube at a time.
If the problem is in Channel 2, replace V5.
If the preamp controls have an impact on the noise, but changing tubes does not fix the problem...take the amp to a good tech.
- Feb 12, 2006
- 61,095
- 5
- 221,230
- Disclosures
- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
A qualified Ampeg service center should be able to sort this out without trial and error guessing (which costs more than proper troubleshooting and repairing a correctly identified cause).
All this guessing typically points to incorrectly diagnosed amps.
All this guessing typically points to incorrectly diagnosed amps.
I see guessing as something someone without test equipment can do at home before taking the amp in if necessary. Some fixes are simple.
Unfortunately, some techs will accept an amp and sit on it untouched for weeks. Not a good business practice but many do it. Saying "this is what a tech might do" is a way of making suggestions of things to try without endorsing opening the amp. Someone without any service experience shouldn't open an amp.
Unfortunately, some techs will accept an amp and sit on it untouched for weeks. Not a good business practice but many do it. Saying "this is what a tech might do" is a way of making suggestions of things to try without endorsing opening the amp. Someone without any service experience shouldn't open an amp.
- Feb 12, 2006
- 61,095
- 5
- 221,230
- Disclosures
- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
Folks without electrical/electronics safety experience should not mess around inside amps. Especially this amp.
Thank you all for the kind replies! After playing with it some more, it looks like it may have something to do with the bass knob on channel 2. I definitely don't feel comfortable messing around inside so will take to it to an ampeg person as soon as I can, and will update this when I hear something official. I really appreciate the encouragement as far as the fixability of the issue, this amp is a real joy to me.
Even my 70s SVT once started to suffer on this buzz issue.
The issue can be easily fixed with some lining of sealing tape (or something similar that was suited to fix this buzz issue)
I thought the new Ampeg ownership might prove to be beneficial. On the other hand, my 5 year old SVT CL continues to shine without so much as a hiccup. Pretty pleased with it.
