Dismiss Notice

Psst... Ready to join TalkBass and start posting, make new friends, sell your gear, and more?  Register your free account in 30 seconds.

Schematics for SVP-BSP?

Discussion in 'Amps and Cabs [BG]' started by Frank Martin, May 21, 2004.


  1. Frank Martin

    Frank Martin Bitten by the luthiery bug...

    Oct 8, 2001
    Budapest, Hungary, EU
    HI!

    Does anyone have the wiring schematics for the SVP-BSP? I've scoured the net, but couldnt find it so far. (I'm looking for a more detailed one than at the Ampeg site.)

    Why do I need it? :eyebrow:
    I was thinking of modifying my SVP-BSP: I really like the smooth clean channel, but the OD channel has too much OD and Dist even with the Gain boost off. So I asked my Dad (he's an electro-engineer) if it is possible to tame the OD and maybe even install tubes to the OD section, and he said it is possible, but a detailed schematics is necessary for it. I'll post about the results once it is done :hyper: :cool:

    So: anyone have the SVP-BSP schematics or know where I can find it?

    Thanks! :cool:
     
  2. Frank Martin

    Frank Martin Bitten by the luthiery bug...

    Oct 8, 2001
    Budapest, Hungary, EU
    Bump...

    Do you at least think its a good or a bad idea to mod my preamp?
     
  3. notanaggie

    notanaggie Guest

    Sep 30, 2003
    Don't have them. But in general, some modding is Ok, not too much trouble, and works OK.

    If you get too wild, especially in a tight single-rack unit like that, you just reach a point where stuff doesn't work right because you can't put it where it wants to be...no room. Wires get long, it gets unstable, etc.

    I would think putting tubes in the solid state channel would be like that. Not to speak of needing another half an amp or so of filament current (depends if the filaments are wired 12V series or 6V parallel), and some more plate current. Don't those have a rather small transformer? Not much room in there.

    Probably someone somewhere has done it. But I'll also bet its a real pain in the rump to do.
     
  4. Frank Martin

    Frank Martin Bitten by the luthiery bug...

    Oct 8, 2001
    Budapest, Hungary, EU
    Hmm... maybe then I'll ditch the tube idea, and only soften up the overdrive... that overdrive is simply overkill: at noon, it sounds like the SVP-Pro at full gain with drive on full, too, and if you pull on the boost knob... :eek: yeah, its a bit too much...
    I'll ask my Dad to take a look at it when he has time...
    Maybe I just switch the entire SS OD channel to something like a close copy of my SVP-Pro? :meh: :smug:

    Ther reason I'm doing this is because I would like a channel-switching&combining pre that has a very clean, smooth and punchy SS Clean channel, like htis BSP, but also has a bit more dirty tube-overdriven channel, like my SVP-Pro, but these two in only one unit.
    This pre was the closest I could find to what I was looking for (even at first I thought - hoped - that the OD channel had the tube).
    Why not use the BSP for clean and the SVP-Pro for dirty?
    I cant keep both pres, I need the money for a poweramp, then I'll sell the rest of my old rig for cab(s).

    Thanks for the reply!
     
  5. nonsqtr

    nonsqtr The emperor has no clothes!

    Aug 29, 2003
    Burbank CA USA
    Hi mutantbassist, I'd nix the tube idea. You'd need to add a high voltage power supply, filament supply, and drill some new holes in the chassis. But taming the overdrive should be quite easy (assuming you can find the schematic), I'd bet a buck that you could do this by changing the value of a single resistor. On the other hand, doing that will result in a "modded" preamp, which will (always) decrease its resale value. Another thing to consider might be an outboard gain/distortion stompbox-type device. Now those you can easily get in tube flavors. Even some of the "guitar" units will work great for bass. I have one called a Tube Driver, it's intended as an extra gain stage to front-end a vintage tube amp (like a Fender Twin or something), but it works great with an SWR 750 too. And it even has a full set of tone controls on it, so you can dial up the sound you want.
     
  6. Frank Martin

    Frank Martin Bitten by the luthiery bug...

    Oct 8, 2001
    Budapest, Hungary, EU
    Ok, then this tube idea is really nearing ditching
    (but the BSP has a tube in it, so it should have the circuitry already... - or not?)
    And many dist/od pedals just dont get that Ampeg tube tone like the SVP-Pro - or are there some you recommend looking into?

    Resale value doesnt really matter to me, I will sell the SVP-Pro, but this is gonna stay for a couple more years.

    Thanks!
     
  7. nonsqtr

    nonsqtr The emperor has no clothes!

    Aug 29, 2003
    Burbank CA USA
    Yes, it does, but typically these days the trannies are spec'd on the hairy edge of self-destruction, in other words it probably handles only barely enough juice to supply the tube components that are already there. If you add another tube and try to tap off the existing supply, your trannie may overheat, and the world may come to an end. Maybe there's some headroom in the existing trannie, but maybe not. To find out for sure you'd have to get the exact specs on the power transformer (Ampeg part number 94-129-30), which wouldn't normally be listed on the schematic (you'd need an actual service manual, or you could try tracing it through Ampeg, or the trannie manufacturer if they're accessible).

    Well, that's an interesting thought. I don't know of any that get the "Ampeg" tube tone, but then again tubes are tubes, and Ampeg's tone isn't all that different from a lot of other stuff on the market. That sounds like one of those things where you just have to go out and find the right one, 'cause as you know there are literally thousands of gain/distortion type devices available to the consumer, including both new ones and vintage ones. Your ear is different from mine, so you'll want to get the one that sounds right to your ear. It's true that simply adding a gain stage in front of the clean channel may not give you an equivalent sound to the OD channel. But I'll bet you can come pretty close with an outboard device. If resale value isn't an issue, and you are (or your dad is) handy with a soldering iron, then a mod might be the better way to go. It'll definitely be a simple (even trivial) mod, once you have the schematic. Can you get it directly from Ampeg? Or if that fails, you might contact your nearest authorized Ampeg service center, if the techs are having a good day they might be willing to share a copy with you.
     
  8. Frank Martin

    Frank Martin Bitten by the luthiery bug...

    Oct 8, 2001
    Budapest, Hungary, EU
    Gee do I love "cost-effectiveness" in companies. :rolleyes:
    Nothing is built like in the good old days, that would handle a lot of abuse and keep on working...

    Oh yeah, the schematic and the shops... :rolleyes:
    the distributor doesnt even list Ampeg on its site... :rolleyes:
    One of their dealers, whom I know is and Ampeg dealer, I asked what an SVP-Pro cost. they tell me "We are busy now. Its somewhere in that stack of papers. If you wait an hour, we will tell you..." :eek: :rolleyes: :mad:
    At this point I left them and havent returned there since.
    And counting on the techs having a good day and sharing a copy with me is not going to work here. the dealers here dont understand how much services mean, the only thing they can do is stretch out their hand for their profit-rate... :rollno: :mad:
     
  9. Frank Martin

    Frank Martin Bitten by the luthiery bug...

    Oct 8, 2001
    Budapest, Hungary, EU
    Forgot to add:

    So this is why I posted this question here: I trust you guys better than those techs here, and everybody here is way more helpful then those bastards! :cool: :)
     
  10. There's a guy on this forum named "Ampeg Insider", who might help you. Do a search - then sending an e-mail perhaps? :ninja:

    Jure
     
  11. Frank Martin

    Frank Martin Bitten by the luthiery bug...

    Oct 8, 2001
    Budapest, Hungary, EU
    Yeah I've met ... erm posted in the same thread as he did, might be a viable alternative...
    Thx
     
  12. BillyB_from_LZ

    BillyB_from_LZ Supporting Member

    Sep 7, 2000
    Chicago
    You should be able to order a complete schematic diagram directly from Ampeg.

    I'd doubt that the transformer would be able to handle the load of another filament...if there were ten tubes in it and you wanted to add one, perhaps, but it's unlikely that they're only using half of the filament winding's capacity.

    Good luck!!!!
     
  13. lsimy

    lsimy Supporting Member

    Apr 18, 2003
    Virginia, USA
    I know this may sound silly (I'm no EE) but if the tube section is driving the overdrive channel, what about just changing the value of the tube ?? If it's a 12AX7, how about trying an AT7 or AU7 ??

    Just a thought.
     
  14. BillyB_from_LZ

    BillyB_from_LZ Supporting Member

    Sep 7, 2000
    Chicago
    That's a good idea, but unfortunately the overdrive in the BSP is purely solid state (as Billy Sheehan likes it). I envision that it should be easy to tame the OD channel by some simple resistor substitutions, but don't know for sure, since I've never seen the schematic.
     
  15. lsimy

    lsimy Supporting Member

    Apr 18, 2003
    Virginia, USA
    Sorry to dig up such a moldy oldie thread here.

    Mutantbassist, what ended up happening with the BSP preamp ?? Did you end up modding the drive channel ??
     
  16. kringle77

    kringle77 Supporting Member

    Jul 30, 2004
    Massena NY
    With one wave of my hand, I resurrect this long dead thread!

    Really, did anything ever come of this svp-bsp mod?