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SVP-Pro DI hiss vs SVT2-Pro DI hiss

Discussion in 'Amps and Cabs [BG]' started by wyrtti, Sep 21, 2005.


  1. wyrtti

    wyrtti Supporting Member

    Oct 24, 2000
    Helsinki, Finland
    A few years ago I tried an Ampeg SVP-Pro preamp. I loved the tone, but the unit had problems with hiss, especially in the DI, so it didn't work out for recording.

    Now I am in the market for an all tube amp. I am very much tempted by the SVT2-Pro, although it is quite pricey.

    Do any of you have recording experiences with this amp? I am especially interested to hear whether the DI hisses as much as the SVP-Pro or has that been somehow overcome with different layout and perhaps different parts, even though the SVP-Pro is said to be the preamp part of the SVT2-Pro.

    I've tried to search the forum, and from what I've gathered the SVT2-Pro is quieter than the SVP-Pro (unless you're one of the lucky ones with a quiet SVP-Pro), but I haven't found anything relating to the SVT2-Pro's DI.

    Thanks for any info you can provide.
     
  2. I think with the 2pro you'd be best using a mic to record, thus getting the sound of that lovely power tube section, you do know if you using the DI on an all tube amp, you still need a load (ie speaker cab) attatched, even if you just want to use the DI out

    I'd recommend checking out the older SVT II (non-pro) less bells and do-dahs (of which the only one i really miss is the pre-gain), but it sounds nicer than the 2Pro imo, they are also relatively cheap on ebay
     
  3. wyrtti

    wyrtti Supporting Member

    Oct 24, 2000
    Helsinki, Finland
    Oh, I'd be micing the cab also, for the reasons you mentioned, but I would also like to DI the preamp. Ah well, I have other DI's, so it isn't that big a deal. I guess I'm just being overly cautious before making such a big investment.

    Also have to check out other tube amps...the Orange sounded mighty nice, been to the store twice already to try it... :)

    But still, the SVT2-Pro has always had me smiling when I've tried it, I guess I'm hooked on that.

    Thanks for your comments, i_got_a_mohawk.
     
  4. Ask if you can try out the DI on it, i guess thats the only way unless someone chimes in with experience

    I was just saying about the cab just incase you didnt realise, sounded like you were going to go straight from DI

    If you figure out which one you prefer, i'd say go for it, but you'd be best to go second hand and get it for less than half the price it is new :)
     
  5. plus when you get gas for a new amp in a year you'll be able to sell the Ampeg for about what you paid.
     
  6. pickles

    pickles Supporting Member

    Mar 23, 2000
    Ventura, CA
    I imagine the direct outs are very simmilar on the two units. I'd suggest using an outboard DI (like a countryman or radial) for your direct tones. Your (live) soundmen will like it since your EQ changes at the head won't tweak their mix.
     
  7. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    Incidentally, most of the DIs have been re-worked in the last couple years or so. Most that didn't have transformers got them, and gains etc have been adjusted for better performance.

    Some previous ones were line-out type levels, too hot for a mic, not *quite* there for a direct line out...
     
  8. wyrtti

    wyrtti Supporting Member

    Oct 24, 2000
    Helsinki, Finland
    Probably can't find them used around here, this is a small country. I also don't think getting a used one off American eBay is a good idea, due to different voltages etc. I HAVE been watching German eBay, so I might get lucky.

    Thanks to all of you, who answered. The idea of an outboard DI is probably good. I already have a Sansamp, so that will suffice for now. Now I'll just continue dreaming about that lush tube tone... :)
     
  9. el_Kabong

    el_Kabong

    Jul 11, 2005
    It's not quite the same amp but it may be worth knowing that a new svt-cl head has a multi-voltage transformer. It's just a matter of repatching internally to 240v and changing the fuses. Jerrold might be able to tell you if the svt2pro is the same. If Finland is like Australia you can import a new one for half the local cost. I really like the di on the svt-cl, (good job Jerrold!) fat, punchy and quiet. Only 'problem' with it is it is permanently post everything (including master volume).
     
  10. I managed to get my SVT II in the uk dead cheap somehow :D , most of the all tube amps, like said, have transformer "taps" so you can get a tech to change what power supply type its going to use

    That must have been done with mine, its got 110v printed on the back, and we are 240v over in the UK, (maybe 230v now ?), anyway, it had been changed and checked (UK service stickers), so it can be done, the BIG problem with getting an SVT from the US is that postage will be about the same as the amp itself, and then you have import tax's and such ontop :(
     
  11. el_Kabong

    el_Kabong

    Jul 11, 2005
    I paid around USD$200 for ups airfreight from music123 to australia, nowhere near the cost of a new classic. Music123 seems to be pretty reasonable with their international freight costs for amps & cabs.
     
  12. I noticed this, music123.com have an unbelieveably cheap shipping with ups somehow, whenever i looked myself it came to $700+ :(
     
  13. pacAir

    pacAir

    Feb 25, 2008
    N/W Oregon
    Just an info update attached to this old link...

    I ran into some interesting tidbits regarding the Ampeg SVP-PRO bass preamp. There appears to have been at least 3 distinct generations of this product.

    The Ampeg SVP-PRO "blackface" (introduced in 1990, with black faceplate, panels and chassis) had an active D.I. output with level control. There was no output transformer, just an op-amp IC. This version had a power transformer that was mounted with the exposed core oriented left and right.

    This design was apparently carried over into the 2-tone (Black faceplate with Gray panels & chassis) "facelift" in 1995 except shortly after this mpdel was introduced, there was a change in circuit board layout which rotated the power transformer 90 degrees such that the core pointed front and back. It is assumed that this change lowered hum pickup caused by the magnetic field of the older orientation of the power transformer. (Note:These newer PC boards were typically white in color and I have seen a few pictures showing these white boards in a blackface unit.)

    Fast forward to 1999, a new version is introduced (still 2-tone aesthetics) and the only external difference appears to be that the D.I. XLR connector moved to the right side of the "Tuner Out" jack and lost its level control. Inside, the D.I. circuit was changed to that found in most modern Ampeg SVT-PRO heads... a passive transformer-coupled design. (Note:These PC boards were typically green in color.)

    Also, on some post-1999 units a toroidal filter element may have been added to the AC input circuit (presumably to filter out line noise injection). The transformer-coupled D.I. output provides better electrical isolation and potentially less hiss because it is not an active op-amp with gain. None of these versions have a Ground Lift switch on the D.I. output. You either have to modify the circuit or use an external passive D.I. box that already has a Ground Lift switch.

    The best way to tell an early from later model 2-tone unit is the location of the D.I. XLR connector and the presence or absence of a D.I. output level control on the rear panel.

    Most of this info was derived from internet sources (so it must be true) and evaluating SVP-PRO photos of all 3 variants. The SVP-PRO was discontinued in 2007. I have not had all 3 variants in-hand for inspection or testing.

    Corrections or comments welcome.


    Steve
    Pacific Music Services
     
  14. pacAir

    pacAir

    Feb 25, 2008
    N/W Oregon
    I just bought a used Ampeg SVP-PRO preamp and found that it had an annoying hum/buzz audible in the output. I did some troubleshooting and discovered that everything was reasonably quiet until the last tube (V5) which drives the preamp output.

    On an oscilloscope, looking at the output noise with the Master turned all the way up (no input signal) I could see a strange waveform (a 120hz pedestal with a rising-edge pulse 2x the height of the pedestal). This first occurred at the output of the first half of V5. This was the noise I was hearing. V5 is closest to the power transformer and may be more sensitive to the magnetic field of the transformer core. I verified that this noise waveform did NOT originate in the B+ DC power supply (275Vdc).

    I played musical-tubes with a variety of tube-types while watching the scope for noise and found the the NOS JAN Phillips 12AX7A I had put into V5 had the above waveform. I tried a GE 5751, A Sovtek 12AX7, a GT 12AX7R, a new Tung-sol 12AX7 and a new Electro-Harmonix 12AX7EH. All of these tubes were lower in generated & induced noise than the NOS JAN 12AX7WA! Out of all these tubes, the EH had the lowest residual noise floor with a smooth waveform that produced much less audible hum or buzz in the output. However, the 12AX7EH was WAY too microphonic!

    Digging around in my tube collection I found a NOS French military (Valve) CV4024 which I had originally bought for use in a tube condenser microphone. It has about as much gain as a 12AT7 and is very quiet (although it has just a bit more high-frequency hiss than the EH, it is actually quieter overall and is not microphonic in the least).

    When using a 12AX7 as V5 it was possible to get greater than 40Vp-p output level when everything was cranked ( w/ 300mV instrument level input @ 1kHz). With CV4024 in V5, 30-35 Vp-p is a maximum clean output (still plenty of headroom, less noise). When I tried to use a 12AU7 in V5, about 10Vp-p output is all I could get and that is a bit too low for my tastes. It seems that Ampeg designed more gain into the output stage than it did for input stage so it is more susceptible to noise generation, microphonics and induced hum pick-up.

    My current tube line-up is:

    V1: NOS 1971 GE JAN 5751 (Green Label) (Audio Input section w/ Mute, Pad & Peak)
    V2: Groove Tubes 12AX7R (Came with the preamp) (Drive Section)
    V3: Groove Tubes 12AX7R (Came with the preamp) (Tone Control Section)
    V4: NOS 1962 GE 12AU7A (Graphic EQ, Effects Loop, Master Volume Control))
    V5: Valve CV4024 (Preamp Output Stage)

    While the 5751 at V1 is less gain than the 12AX7, the military and Hi-Rel Commercial/Broadcast 5751 tubes were made with additional mica element supports so these tubes are much less likely to go microphonic and have a nice clean tone.

    YMMV

    Steve
    Pacific Music Services