All-tube SVT heads

[christw]

I had a '93 or '94 SVT-II that I mentioned and a newer 2003 SVT-CL. I can't say that I saw anything less from the CL but I didn't own them at the same time or use the same cabinets.

to the OP: cab can't handle the low end. they always say it: Tube Watts don't always equal SS watts. it's not a fair comparison the 1600watts of the 4pro vs the 300watt 2pro . so don't expect quieter/restrained results.

That kind of myth is exactly why people (myself included) have and still do expect too much from tube amps. Yes, their overdrive characteristics are significantly different than SS preamps or output sections are but an amp rated at 300 "clean" watts at x% total harmonic distortion will only put out 300 "clean" watts at x% THD no matter what it's output section is made of. Tube amps often are regarded as sounding better overdriving but that's because their clipping characteristics are different from SS amps. If your 300w RMS ss amp hits it's peak, you'll go "EW!" and turn down a little or turn your compressor up to get more perceived volume but at the expense of some dynamics. That's a bit like running a tube amp to overdrive and a bit of why they seem louder. On top of that, you have a lot of harmonics added in the distortion of the tube amp that can add presence and perceived volume as well.

 

[Alex1984]

Disengage the Ultra-Lo. It tightens the tone and gives you a great scooped tone, but it also cuts down the perceived volume, and with the compression and stuff going on I believe it may be pushing the Warwick cab hard without you realizing it.

 

[Aharon]

Ok so I finally got to A/B the SVT 2 pro today at a decent volume. Here are my observations.....

First things that leapt to my attention:

1. SVT 4 had a much tighter and even-sounding low/mid bass response. Much less dynamic range in this part of the EQ spectrum, quicker to react and 100% clean.

2. When trying to use a DBX160A compressor with the SVT2 pro, it proved difficult when using the gain as the master volume because I couldnt feed the compressor with a hot enough signal from the preamp.

3. When jacking the fx send of the SVT 4 Pro into the power amp in of the SVT 2 pro, the master volume on the 2 pro did not do anything. The gain knob on the SVT 4 seemed to control gain and master volume simultaneously (not sure what is going on here?)

4. The SVT 2 Pro seemed to exagerate dynamic range more than the SVT 4. Aggressive pick playing sounded much more "peaky" and in need of some serious compression / limiting. I think an instrument-level comp pedal would be more appropriate with this amp and the way that I work the gain/master.

5. The SVT 2 Pro appeared to be attenuating some of the ultra-high frequencies and sounds coming from the bass. Roundwound percussive noises and fret buzz seemed to be smoothened out a little, possibly masked by soft clipping and more harmonic content.

6. The SVT 2 had MUCH more harmonic content. This was even more noticable when using the gain as the master volume and further noticable at louder volumes.


I also happened to spot a rather noticable blue glow when I looked at the power tubes from the back, in addition to their natural orange glow. Any ideas? Winged C 6550's are in there.

I'm going to be doing some more experimentation. I got a high-gain sovtek preamp tube that I'm going to try out in the SVT-4 Pro just to see if I can get a little more gain out of it. I may also drop some money on some pre/power tubes for the svt 2 pro, where I am particularly looking to tighten up that low end and increase clean headroom slightly. (sovtek kt88's a good choice?)

 

[JimWasHere]

3. When jacking the fx send of the SVT 4 Pro into the power amp in of the SVT 2 pro, the master volume on the 2 pro did not do anything. The gain knob on the SVT 4 seemed to control gain and master volume simultaneously (not sure what is going on here?)

The master volume of the 2PRO is before the power amp input in the signal chain. So the master volume on the 4pro would be the one that works. The manuals for both amps are accessible on Ampeg's website, and they both have diagrams that really help visualize what's going on in there.

http://www.ampeg.com/pdf/SVT-2PRO.PDF
http://www.ampeg.com/pdf/SVT4PRO.pdf

 

[Aharon]

The master volume of the 2PRO is before the power amp input in the signal chain. So the master volume on the 4pro would be the one that works. The manuals for both amps are accessible on Ampeg's website, and they both have diagrams that really help visualize what's going on in there.

http://www.ampeg.com/pdf/SVT-2PRO.PDF
http://www.ampeg.com/pdf/SVT4PRO.pdf

Thanks Jim.

I'm guessing that the power tubes in the 2 pro are maxed out by default in this case, which would explain why the controls on the svt 4 became so sensetive.

I'm gonna continue to compare/experiment with the two. Right now the 2 pro seems more musical but the 4 pro seems more functional. Might try swapping out some of the tube pre's to see what happens but I'm not sure it will solve the "uneven" sound.

 

[Jonyak]

The ultra low almost always sounds better when you are just by yourself, but in a band setting it will take much more power to make yourself heard above the rest of the band.

The strength in SVT's lies in the mids section. I boost the mids on both of mine and cut through like a hot knife through butter.

Turn on the ultra low and I disappear.

PS: I have owned an SVT II pro, and currently own a 74 SVT and a SVT CL w/ 810e, 410hlf and an eden 410xlt.

 

[kosmicwizard]

I have a sneaking suspicion that you are a nooner, I have an SVT II (non-pro) my BASS is at 11 O'clock, my MIDS are at 1 O'clock, and my HIGHS are at 12 O'clock. Do you engage your EQ? What position are your Gain and Master Volume at? I have J/J KT 88's in mine and since they can take more plate voltage they actually last longer than 6550's. It feels like getting beaten with a pillow for lack of another way of describing it, and sounds heavenly. Yes they will give you more clean head room, but I don't think that is the problem. Also, the Mesa is NOT a 400 watt all tube head, the original BASS 400 got 180 watts with 6 6L6's in it and 234 watts with 6550's in it, the 400+ could get 360 with 12 6L6's I suppose but they were always running cold (about 500 plate voltage) and probably didn't push out anymore than an SVT (at 700 plate volts). Cheers.

Hi all.

Recently acquired an SVT 2 pro. Firstly would like to say I have been reading quite a bit about the different all -tube SVT heads out there regarding headroom, biasing, tube rolling, cab compatability/no. of speakers etc. I have furthered my knowledge immensly but am still wanting to know more.

The bottom line is clean headroom. At band volume the notes on the low E are causing a "farting" kind of break up. After reading extensively on the matter, I am unsure whether this is just what the amp is designed to do or if something is wrong.

The cab is a ported 610 (warwick) that has handled much higher volume and power load with my SVT 4 pro. I also briefly owned a Mesa Bass 400+ and the low end on that didnt fart out at louder volumes, leading me to believe the cab is not the culprit.

I like the subtle, harmonic saturation that occurs with a slight bit of drive, but I do not like any audible "distortion" particularly of the low end. I am not asking for the SVT 2 pro to be squeaky clean like my SVT 4, but surely this low end farting business is not part of the amps design? I opened it up and all the tubes seem to have a healthy glow and the bias lights are both green. I did a microphonics test with a chopstick on the preamp tubes and nothing came out of the speakers. I have tried different combinations of gain/drive/master and it all seems to bottom-out at around the same sort of volume.

Was it the extra 100w of headroom on the Mesa that allowed the low end to stay intact? Can I increase my headroom using KT88's without making the low end all flabby and retubing every 6 months? Do lower gain preamp tubes actually affect power tube break up / headroom or are they purely for tonal shaping? Does the SVT VR have more clean headroom?

Thanks in advance.


Gear used:

Svt 2 Pro (tubed with winged c 6550s)
Gibson Ripper bass (low output)
Warwick 611 pro (900w @ 4ohms, ported)

 

[meatwad]

Please listen to all these other guys, and say "NO!" to Ultra-LO. Sounds great when being played by itself, but most definitely a tone sucker in a band situation. As for comparing the CL to old SVTs, IMO my CL (USA circa 2000) sounds better with JJ preamp and Winged "C" power tubes than it did with the stock Sovteks, and IMO, sounds every bit as good and loud as my two old SVTs did.

I also think a ported cab with a tube amp (in general) isn't the best match. I may be wrong here, I just always though tube amps sound best through sealed cabs, with multiples of 10" drivers.

 

[jmpiwonka]

IME my svtII sounds flat with both hi and low switches off, eq off also.
bass at 11oclock position, mids around 2 oclock and treble at about 1-3 oclock...my 810 cabinet has the darker sounding drivers in it.

volume has to get up to atleast 10oclock or so and thats when it all starts to come together. i usually turn up to about 11oclock.

tube rolling helped a little but not much. mostly rolled the preamp tubes. i think the 12ax7 in the power section is on it's way out, after about 10 minutes of playing signal gets weak and i have to flip it on standby and then back on and it usually works fine the rest of the time.
so i'll be swapping another tube in that position to see if the problem persists.

like was stated previously, the V1 position is the preamp tube to roll. i have a JJ ecc803s in that spot. high gain...sounds best for me...as in the meanest...

 

[jmpiwonka]

oh yeah, also i had to take a screwdriver to practice a few times and adjust my pickup heights to get it more even sounding...you know switching amps/cabs you gotta fine tune stuff sometimes.

also i have a mesa boogie 215 with ev15L drivers, it never really sounded farty in the lows but there was definitely too much bass with that cab. kinda scooped sounding i guess. when i first got the svt i was thinking where the hell are all the mids.

so got an 810e cabinet for cheap off CL and haven't played the mesaboogie since. sealed cabinet is the way to go with tube heads i think...