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AMPEG SVP PRO TROUBLE

#2
Originally posted by axe
I just bought an ampeg svp pro pre-amp off e-bay just got it hooked up with all good cables. But there is a nasty humming buzz that sounds terrible. Do I need to replace the tubes or is this something more severe?
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I bet you cant find a thread on talkbass that doesn't have somebody commenting on how noisy these are. I bought one, and sold it quickly. I find this is not uncommon, and I think this is why you see so many of them on e-bay.
 
#3
There's a mechanical transformer buzz with the SVP-PRO, but it doesn't come through the speakers or DI.

Run your DI into something you can plug headphones into, you won't hear it. Or use a long cable and move it far enough away from the speaker (like another room), you won't hear it. Or just turn up loud enough that you don't hear it. :D

[/megaphone on]
Pick up the bass, and step away from the SVP!
[/megaphone off]
 
#5
I agree that they do make noise, but I never noticed an unusual amount of noise coming through my rig when I used the svp-pro. You may want to try swapping out the tubes as they may have been banged around alot during the shipping. If I am not mistaken, there are 5 tubes in the the thing, 4 12ax7s and 1 au7's (?) as the "drive" tube. They do sound very good when all the tubes are in good working condition.

John
 
#11
I bought a Lord Valve retubed SVP from boogiebass, and while it is a bit noisier than my very quiet Alembic F2B, this SVP is still plenty quiet for live use.

Originally posted by Schwinn
People say that the SVP is not in the same league as Aguilar, Kern, and Demeter, which I'm sure is true, but the SVP gives my exactly the kind of tone I'm going for so I'm a happy camper.
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As for being in the same league with Aggie/Kern/Dem: no, it isn't, but then it isn't priced in that same league either! As mentioned many times, with proper tubes the SVP should work fine. If you like the Ampeg tone and don't mind a little more noise, then there's nothing wrong with choosing Ampeg over the higher-priced models. Sometimes I use Alembic, sometimes I go with Ampeg... depends on my mood.
 
#13
Open mouth, insert foot... ok I plugged straight into my SVP-PRO (instead of going thru my pedalboard with distortion), turned it up pretty high while not playing, put ear next to speaker, and lo and behold there is in fact a horrid buzzing noise. I had to turn it up pretty high to hear it, so I don't know if a LV retube would help or if that's as good as it gets.
 
#14
Originally posted by Metal Mitch
Open mouth, insert foot... ok I plugged straight into my SVP-PRO (instead of going thru my pedalboard with distortion), turned it up pretty high while not playing, put ear next to speaker, and lo and behold there is in fact a horrid buzzing noise. I had to turn it up pretty high to hear it, so I don't know if a LV retube would help or if that's as good as it gets.
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Well...it might be as good as it gets. If you crank the volume you will hear noise, but it shouldn't be audible while you're playing. LV said that there is a design issue with the preamp, but that the right tubes can only minimize it. Other amps that I've used get real noisy when the volume is cranked up anyway....
 
#16
The problem everyone is discussing is with out a doubt a earth problem. What the issue is a potential difference in your earth between the preamp and the power amp. What verified this to me was the guys who use the di output don't suffer from this hum. This because there is a isolating transformer between them and the signal. All you need to fix the issue is to purchase a good quality. and lots of car audio stores stock them. A good Earth loop isolator and use this between the preamp and the power amp. Problem solved.
 
#17
Hi.

ibanezroadster said:
The problem everyone is discussing is with out a doubt a earth problem. What the issue is a potential difference in your earth between the preamp and the power amp. What verified this to me was the guys who use the di output don't suffer from this hum. This because there is a isolating transformer between them and the signal. All you need to fix the issue is to purchase a good quality. and lots of car audio stores stock them. A good Earth loop isolator and use this between the preamp and the power amp. Problem solved.
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Just out of curiosity, are You on some kind of a quest?

To find all SVP threads proposing the same fix?
Which even isn't a fix IMO.

Or just very bored and desperately seeking attention?

If the latter, You got mine :)

Regards
Sam
 
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#20
axe said:
I just bought an ampeg svp pro pre-amp off e-bay just got it hooked up with all good cables. But there is a nasty humming buzz that sounds terrible. Do I need to replace the tubes or is this something more severe?
Click to expand...

Hi all, I'm a new guy on this forum and don't speak very well in English but.... finally found on my SVP-PRO the reason of the buzz, noise, hisss issue. No information is available on any forum about this solution and believe me,,, the noise floor is actualy below -95db with GAIN AND MASTER set to max. Two days ago I found the svp pro schematic on web and this morning I've found a little mistake on the diagram ... and this mistake was in my unit as well... if you looking carefully on schematic you can see that all tube heaters are NOT REGULATED... heaters are connected before the VOLTAGE regulators...that mean heaters are driven by AC VOLTAGE rather than D.C. VOLTAGE. (Way more noisy with AC VOLTAGE)
I did the little mod into my unit ( 4 little wires ) add a capacitor to remove extra noise to the heaters and now ------ quiet SVP-PRO :-). I can provide pictures on request. Cheers !!!
 
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