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200 Watt SVT? How to do it?

#101
fu22ba55 said:
What about building a 200W all-tube slave from scratch, based off of an SVT schematic, and dropping a genuine turret-board B15 on top? That would be pretty mighty... And mighty expensive.

Heck... that's almost a viable product idea. A 200W ampeg-clone slave, ready to accept any fliptop head? Could you even scavenge the 30W from the fliptop for an additional 30W?
Click to expand...

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Just build one, and bypass the preamp. Or have your tech not build a pre amp....

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Scroll all the way down.

coreyfyfe said:
Addendum to my last post - here's a good starting point - http://cgi.ebay.com/1974-Ampeg-VT-2...742?pt=LH_DefaultDomain_0&hash=item2309b5b93e

Things not working as is so you have a problem amp to start with, drop in new transformers....
Click to expand...

Howdy doodly that is DIRTY! :eek:
 
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#102
johnk_10 said:
have your tech look into lowering the plate voltages on the output tubes. it should run under a $100, and you could even install a 2/3rd's-full power switch somewhere to so you could have it both ways. it might require a re-bias, but you probably could even make it change it's bias when it is switched. alot of guys do it on guitar tube amps all the time.
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John, that sounds fantastic. Thank you. I'll ask my tech tomorrow.

A 2/3rd's switch would be amazing.

Do you think it will give me the same breakup (fuzz) at a lower volume, or less breakup at a lower volume? (Or less breakup at the same volume, which would be bad.)

johnk_10 said:
the reason you never hear of someone doing it on a bass amp is probably because most bass players are always wanting more power, and not less.
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Totally agreed.

The other factor in all of this is still being able to drive a 2 ohm load. It's nice more a lot of air, even at a lower volume, and the problem with many of 200W amps listed in this thread is that they wont drive a 2 ohm load.

So a 2/3rd's switch on my SVT (or any SVT) would be amazing.
 
#106
fu22ba55 said:
Hey Ed.

No I haven't. Would that solve the problem? Just plug in and dial it down? And, more importantly, is that safe for my precious V9?

This page says it's safe...
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Um.

Not really.

Its okay to power an amp up with, and the only way i will if it hasn't been on in awhile, but when you use a variac, you lower ALL the voltages. Even the heaters, which you do NOT want to tamper with. That is, a variac that you plug the amp right into. I've heard some stuff about variacs built into amplifiers, but never dealt with them personally.
 
#107
while i've done it many times in the past, the only problem with a variac is that the filament voltage drops along with everything else (not good for the tubes).

a low power (plate voltage reducing circuit) should yield everything that you're looking for. done right, it could make it into a 200 watt SVT and break up the same way as it does at 300 watts, only at a lower volume.
 
#108
KramerBassFan said:
Um.

Not really.

Its okay to power an amp up with, and the only way i will if it hasn't been on in awhile, but when you use a variac, you lower ALL the voltages. Even the heaters, which you do NOT want to tamper with. That is, a variac that you plug the amp right into. I've heard some stuff about variacs built into amplifiers, but never dealt with them personally.
Click to expand...

I want to buy a variac and use it to power up amps that have been sitting. can you explain how it's done? I've heard it takes hours. thanks :hyper:
 
#109
johnk_10 said:
while i've done it many times in the past, the only problem with a variac is that the filament voltage drops along with everything else (not good for the tubes).

a low power (plate voltage reducing circuit) should yield everything that you're looking for. done right, it could make it into a 200 watt SVT and break up the same way as it does at 300 watts, only at a lower volume.
Click to expand...

I also think that in the long run this is probably the best option.
The only positive to the variac would be the ability to crank it back up when you needed to kill rodents or knock down walls.

You are probably OK if you don't get crazy with the variac.
You can scrub a few volts off, in fact your old V9 probably is happier with 110-115 rather than the common 120 VAC line voltage that is more common today anyway.
If you go too low you can strip filaments and seriously shorten tube life, maybe screw with the bias, and failing tubes can take other more expensive parts with it.
Of course, attenuators don't do your tubes any favors either.

Or see if Kevin O'Connor at London Power can hook you up with a Power Scaling kit that will handle an SVT.

But, I've always thought that tubes were "wear items" anyway, like replacing the brake pads in your car... :rolleyes:
 
#110
i hate replacing brake pads in my car and try to keep them as long as possible. same for tubes. but in this case, i think fu22 is going to have to suck it up. if not the voltage reduction, cranking it so loud will make sure it happens. doesn't sound like he's sweating it like i do, though.
 
#111
fu22ba55 said:
-Gibson RD Artist without the Moog preamp. Just the stock pickups rewired like a jazz bass. Tone rolled all the way off, neck pickup only.
-V9 Head (Magnavox-era SVT) Volume at about 2:30.
-TL606s loaded with EV15Bs
-EV RE-20 dynamic mic to digital recorder.
Click to expand...

Send me a pic of your amp settings and ill do a little experiment for fun and maybe to help you. I have a 73ish magnavox SVT, a 115 loaded with a carvin eminence speak and a slew of basses and weird fuzzes (see me profile) and ill try to recreate that tone you posted using a ped and volume at about half or less. I got a cheap On Stage condenser into an E-MU 0404 and garage band for recording. Let me know what you think i can do it sat when the wife is at work if your interested.
 
#112
johnk_10 said:
while i've done it many times in the past, the only problem with a variac is that the filament voltage drops along with everything else (not good for the tubes).

a low power (plate voltage reducing circuit) should yield everything that you're looking for. done right, it could make it into a 200 watt SVT and break up the same way as it does at 300 watts, only at a lower volume.
Click to expand...

I don't think the svt preamp circuit would take to kindly to running on lower voltages, you'd lower the headroom to much
 
#113
ampegfuzz said:
Send me a pic of your amp settings and ill do a little experiment for fun and maybe to help you.
Click to expand...

Here are the amp settings I used in the above clip, and for the last 14 years. (hence the tape).

I replace the power tubes and the speakers about once every three years with average use, every two years with heavy use.

IMG_2541.jpg


I'm boosting 300Hz +4

IMG_2543.jpg


The mid rocker switch is different on the V9. The SVT uses 220Hz, 800Hz and 3kHz. The V9 uses 300, 1k and 3k. Also, no ultra-low on the V9.

But you should be able to get the identical sound out of the SVT. I can get the same sound out of a B15 or a V4B. Once you're pushing the power tubes that hard, the EQ only slightly colors the intensity and shape of the fuzz. The power tubes are doing all the work re: the tone.

Here's a beauty shot of the V9 head just because:

IMG_2542.jpg


Note that the top edge does not "break" back like an SVT. It's a big 'ol rectangle.

I'm shooting an email to my amp tech right now with some of these crazy suggestions. Will follow up.
 
#114
I've been wracking my brains trying to think of ways that you can lower the wattage of the amp with minimal effect on the tonality and powersection saturation characteristics.

It just hit me that I've been thinking harder, rather than thinking smarter. Any mod that changes the original spec of the amp will change it's sound.

If the goal is powersection saturation at reasonable volume while maintaining the 100% true original spec svt sound then the simplest solution I can think of isn't in modding the head.

That being said, I would now like to throw the suggestion of an isolation box for your cab into the ring. If you can find the rig specs for a lot of major touring acts just about everything on stage is just for show, the real rig is screaming with the volume at "10" under stage in the tech area in an internally mic'd iso. box.
 
#115
that would be a good idea if there's room at the club to iso a giant bass rig offstage, but i don't think that's in his paradigm. he wants to hear it from the amp. very picky guy, this fu22ba55 ;)
 
#118
fu22ba55 said:
Here are the amp settings I used in the above clip, and for the last 14 years. (hence the tape).

I replace the power tubes and the speakers about once every three years with average use, every two years with heavy use.

IMG_2541.jpg


I'm boosting 300Hz +4

IMG_2543.jpg


The mid rocker switch is different on the V9. The SVT uses 220Hz, 800Hz and 3kHz. The V9 uses 300, 1k and 3k. Also, no ultra-low on the V9.

But you should be able to get the identical sound out of the SVT. I can get the same sound out of a B15 or a V4B. Once you're pushing the power tubes that hard, the EQ only slightly colors the intensity and shape of the fuzz. The power tubes are doing all the work re: the tone.

Here's a beauty shot of the V9 head just because:

IMG_2542.jpg


Note that the top edge does not "break" back like an SVT. It's a big 'ol rectangle.

I'm shooting an email to my amp tech right now with some of these crazy suggestions. Will follow up.
Click to expand...

thats hot
 
#120
MAMMOTHvolume said:
preamp supply comes from the plate supply
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do you really think that i didn't know that?
you can still lower the output tube plate voltage without lowering the preamp tube voltage, however, lowering it to the preamp a little probably wouldn't hurt either, it would be similar to running it on a variac but maintaining the filament voltages.
 

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