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Ampeg SVT-II appreciation thread
- Thread starter i_got_a_mohawk
- Start date
Ive got a bad buzz. It buzzes with no gtr cable plugged in as well, gets worse as the volume increases, and stays with eq on or off. Ground lift doesn’t help. Neither does plugging into another circuit from anothe room. No florescent lights. I replaced the preamp tubes this summer and it was fine but hasn’t been played much since. It didn’t help when I jumped the preamp in/out jacks. I opened up the case to ensure all tubes were seated well. Nothing changed.
What’s my next action before it goes to the tech?
What’s my next action before it goes to the tech?
LoGruvz, where do you go? Jeff Bacos is the best I know with SVTs but usually takes a long time.
He is good from what I hear but I have always used Jeff Andrews his shop is Andrews Amp Lab near Perimeter Mall. He has done all my gear for a long time. Always great results.
No. Haha. Just have everything close enough so I can listen to each combo and not have to move anything but a speaker cable.
That contraption on top kinda reminds me of a Jacobs Ladder. I'm not that familiar with the Jule Monique pre and amp but bet it sounds great. Can you run the Dove Cage in front of the SVT II ?
Yes I have run Monique in front of the power section of the II and V4b. I don't think it improves the stage sound. When I use those amps I use Mo as a DI
No. He charges a flat $65 just to open it up then credits that back to any work he does. I have always felt he was more than reasonable. Just look him up and give him a call he can tell you his rates.
Can any of you Ampeg experts out there answer this question for me?
I know that the "non pro" versions (both logo types) of the SVT-II amp need to have the ferrite beads installed and the R23 resistor changed to a jumper (per Ampeg service bulletins).
My question is, does the later "Pro" version of the SVT2 require those mods? Or did Ampeg already take care of those mods when they came out with the Pro version?
Paging @timv or @anderbass or @beans-on-toast or @Jerrold Tiers or anyone else who might know the answer! Thanks!
I know that the "non pro" versions (both logo types) of the SVT-II amp need to have the ferrite beads installed and the R23 resistor changed to a jumper (per Ampeg service bulletins).
My question is, does the later "Pro" version of the SVT2 require those mods? Or did Ampeg already take care of those mods when they came out with the Pro version?
Paging @timv or @anderbass or @beans-on-toast or @Jerrold Tiers or anyone else who might know the answer! Thanks!
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The later svt 2 non pros I believe came from the factory with the updates done so I would assume that the svt 2pro's do not need them.
I think their may be a screen resistor value change and removal of the diodes that is carried through them though.
It's just to make the amp stress the power tubes less since quality of tubes was hit and miss.
If you're amp is working well and you use good tubes it's probably fine.
I think their may be a screen resistor value change and removal of the diodes that is carried through them though.
It's just to make the amp stress the power tubes less since quality of tubes was hit and miss.
If you're amp is working well and you use good tubes it's probably fine.
The best way to tell if your amp is current is to look on the power board. The original power board schematic is below. Taking a queue from other current production SVT amps, the screen resistor is 220 Ohm ½W flameproof, the parallel 1N4007 diodes are not installed.
The ferrite bead that I use is a Murata BL01RN1A1F1J. The resistance increases at high frequencies and damps oscillations.
This is the bead: Link Removed
You want a screen resistor that will blow when required. There are resistors called fusible links such as the NFR25.
This is the fusible link 220R 1/2W screen resistor: Invalid Link Removed
Thanks for that very helpful info, beans! The thing is, I cannot open the amp to look inside as I do not yet own one of those amps. I am considering buying an SVT2 Pro which is why I am asking if any TB'ers happen to know if the upgrades were taken care of by Ampeg in the Pro version.
If you have the serial number, Loud customer service should be able to determine the revision number and tell you if there were any notices that apply to your unit.
Any new old amp should be given a general servicing and checkout by a tech. They can look at that time. At the very least, if it has the 22 ohm screen resistors, they can install the 220 ohm ones. But the amp will run fine either way. Just to be clear, I’ve not seen a IIP with the 220 ohm screen resistor. The power amp is the same as other models and the current ones use that value. That was why I suggested it.
I have a SVT-2Pro (2006 SLM) and the revisions were done.
Thanks Beans! You are a much appreciated resource on TB!
