Discussion in 'Amps and Cabs [BG]' started by GreyBeard, May 30, 2003.

  1. Got the GAS for some Ampeg tone so I picked up a SVP-Pro and I hooked it up last night. I love the sound but I think, at least in my studio, it's really noisy. Is this characteristic of this pre-amp :meh: or do I have a lemon.:(
  2. Well I did a search (like I should have done in the first place) and found that it is a very common problem with the Little Beast. I'll learn to live with it.
  3. Nino Valenti

    Nino Valenti Supporting Member Commercial User

    Feb 2, 2001
    Staten Island NYC
    Builder: Valenti Basses
    I have one that I use with my SVP-1500 poweramp & I don't recall any noise. But then again I only gig with it & I have earplugs in while I'm on stage. Next gig, I'll pay more attention.
  4. submelodic


    Feb 7, 2002
    Seattle, WA
    I have the same problem - even after changing the stock tubes to Electro-Harmonix. Mine also generates a loud hum. I tried everything before finally sending it to Ampeg for a warranty repair. They changed one tube and sent it back, saying that it was up to spec. The hum is still present.

    I like the tone a lot, but the problems with this particular preamp are substantial.
  5. Here's what I'm doing so far. I have a DBX 266 (2 channel) compressor gate. I've connected the output of the SVP to channel 1 of the compressor/gate and gated out the hum. I use the other side of the compressor for the input of the SVP. So I've got the compressor/gate on both ends of the pre-amp. Not a very elegant solution, but it works so far.
  6. GrooveSlave


    Mar 20, 2003
    Dallas, TX
    Why don't you just run one stage of compression on the output of the SVP? That should gate the noise and control the signal for sending to the power amp.

    Am I missing something here?
  7. jobu3

    jobu3 Artist formerly known as Big Joe Supporting Member

    Feb 17, 2002
    Mountain Top, PA
    try balanced cables? it worked for mine...

    and for what it's worth, i've found EH tubes to be just as noisy as GT and other cheapies... ;)
  8. Mine buzzes too! This is a preamp with serious issues. But it sounds nice and isn't as expensive as aguilars or edens or whatever. It sounds good, but the buzzing business (as well as crackling) really messes up its rep.
  9. rok51


    Sep 2, 2002
    Crawfordville, FL
    Was thinking about getting one. I'm sure it sounds good. Not too keen on the mounting of the tubes, though. Think I'll hang onto my III Pro.
  10. RebelX

    RebelX Guest

    Oct 27, 2001
    Merrimack, NH

    I've got one of these that I picked up new about 1.5 years ago. No noise on mine. When I power it on, there is hum of the 5 tubes, but none of that makes it through any of the connections. It's just about as quiet as my SWR Grand Prix. In a conversation I had with SLM/Ampeg support, they said this unit was really picky about tubes and that when changing them out you need to replace them with quiet tubes. Here's the highlights of the response I had from the support guy on the tube layout of this fantastic pre:

    o The tubes are numbered V1-V5 from left to right when the unit's control is facing you. Each tube is divided into two stages.

    o V1 is the Groove Tube 12AX7 when it leaves the factory and V4 is the 12AU7.

    o The signal enters the unit and immediately travels through stage one of V1, then through the gain pot and then stage two of V1.

    o The bright, ultra high and ultra low switches are next up, then stage one of V2.

    o The drive pot is next up then stage two of V2 and stage one of V3, all of V4, the tone stack and finally V5.

    o "This is only a basic path of this thing? It's a bit complicated and actually has some parallel paths. If you are trying to really fine tune your sound be ready to spend a lot of time experimenting with tube combinations. Also, it is only fair to warn you that the SVP-PRO is very picky about the tubes you put in it; you'll have to search out nice, super-quiet tubes." (Directly from the SLM Service Department)

    Good luck. I love mine and have never been happier with my sound.:bassist:
  11. I've never had a noise issue w/ mine. Even w/ stock tubes. I play into a mixer board out of the DI, and through in-ear monitors. Even when playing w/o's dead silent compared to everything else that's on! Guitars/PA/Etc. I use a setting very similar to the "Rock" Preset in the manual.

    Tell ya what, anyone that doesn't like theirs..I'll buy it for $20 :D Shipping included. I's junk to you basically right? The way you guys speak about it's "noise". Do you guys actually play your bass into your equipment...or do you just turn things on and listen for hum that could be induced by a bunch of different things? :D
  12. I use the compressor on the front end and the gate on the back. I like to compress before the pre-amp and gate after.
  13. doctorgonedon


    Jan 27, 2008
    Same sort of problem, let me explain what I've done and see if this makes sense to anyone:

    Strong 60 Hz hum on the preamp, band members asking me to do something about it, seems to have little to do with tube quality, as I've changed a bunch.

    A buddy suggested that since I was padding the front end, and had it turned way down, that I change the front end tube to a lower gain, so I changed the 12AX7 to a 12AT7, bringing the gain down from 100 to 60. It helped with signal to noise, but not with the hum.

    I saw a post here recently that called out the tube order, and noticed I had a 12AX7 in tube 4 position. I yanked that and installed the correct 12AU7 (big difference in gain, from 100 to 19) and that did lower the hum, but it is still there. I suspect I've lowered the output from the preamop as well, and that the proportion of hum is the same. I am much more pleased with the overall sound, especially with the new front end tube (12AT7). I would even suggest experimenting with a 12AU7 on the front, I just didn't have an extra.

    I suspect that these preamps have, as some have referred in this post, a design that tends to be fraught with hum, and there is likely a primary level physical design flaw (whether that be shielding or general proximity of components) that would take a few hours to pinpoint and relieve.

    Also, I noticed that very coincidentally, the graphic bands that notch the hum also make for a throaty kind of sound, so I use that between 3-6 dB on 2 bands (you'll know the bands when you try this).

    If anyone has suggestions for alternate configurations (I do not rack a gate), I would be very receptive. Wondering about the compressor in the effects loop, not sure this is a good position, but it adjusts and sounds fine.

    As for the hum of the pre, I see this as a spicy analogue: you just don't get the same taste without the hurt :hyper:.

    Spector Euro 4LX Tone Pump pre
    Spector NS20004 EMG 35DC and Aguilar 3B pre
    SVP-Pro (I think about 8-10 years old)
    Peavey 2-way xover (400Hz)
    Peavey 2 x 700W Amp
    Analogue compressor in the effect loop
    Rack tuner
    SWR Working pro 210
    SWR Big Bertha 215
  14. doctorgonedon


    Jan 27, 2008
    Thanks to Rebel above, I wouldnèt have known the tube positions without that post. Funny you would think they would put it in the user manual :bassist:
  15. B-string

    B-string Supporting Member

    I HATE when I read this kind of thing. Makes me want one just so I can find a general solution :mad: 12AT7 would not be my first choice, too harsh sounding, a 12AY7 yes.
  16. ibanezroadster


    Apr 9, 2012
    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.