Modern Day SVT?
Moderators: rickenbrother, ajish4
The retubing "issue" is way overblown, I've had the same tubes in all three of my heads now for over 5 years and I bought two of three 6550 sets second hand on ebay although they seemed pretty new. I use Svetlanas and JJ's.
Now the hauling issue is not overblown however, but that's what my hotrod Roadmaster wagon is for. People are afraid of tubes for some reason nowadays and they last much longer and are more reliable than most people think, especially in bass amps where they are not constantly overdriven like in a guitar amp, and most modern guitar amps over drive a little 10 dollar 12AXY instead of the power tubes although power tube distortion sounds much better to my ears, preamp distortion sounds "buzzy" to me.
I have some 60-70 year old tubes in antique radios that still work believe it or not although the voltages were usually lower in them than in modern stuff which would make them last longer.
There was a period where the tubes being made were subpar but I think that is pretty much over, the new tubes seem to have been pretty good over the past 5-10 years and there are still many NOS tubes left.
Now the hauling issue is not overblown however, but that's what my hotrod Roadmaster wagon is for. People are afraid of tubes for some reason nowadays and they last much longer and are more reliable than most people think, especially in bass amps where they are not constantly overdriven like in a guitar amp, and most modern guitar amps over drive a little 10 dollar 12AXY instead of the power tubes although power tube distortion sounds much better to my ears, preamp distortion sounds "buzzy" to me.
I have some 60-70 year old tubes in antique radios that still work believe it or not although the voltages were usually lower in them than in modern stuff which would make them last longer.
There was a period where the tubes being made were subpar but I think that is pretty much over, the new tubes seem to have been pretty good over the past 5-10 years and there are still many NOS tubes left.
Dunno about reliability, both my 1969 blue-line SVT heads use 6146A radio tubes, not the later 6550s. They are not very long-lived, despite fairly regular bias checks and shock-free handling in transit (in Anvil flight cases with lots of foam rubber around them). But that sweet fat power tube distortion, rich in 2nd-order harmonics without the sharp raspiness associated with solid-state finals, is unattainable with any other amp I have ever tried, old or new. Even other later Ampeg amps don't have it, and neither do the reissue CL attempts from whomever bought out the various Ampeg brands from Dennis Kager and Unimusic over the years since 1969, from Magnavox to Fender to whomever. The original Ampeg SVTs from Linden, New Jersey just seem to have something special in the sound.
The first SVT head that is hooked up to the two original 1969 8x10 CTS stacks (with the original factory four-pin XLR jacks in the back) seems to fail a 6146A a little more often than the second SVT head hooked up to the two V4-B folded W-horn cabinets, each loaded with twin 15 Altec white-frames. Maybe it is impedance to the cabinets? I run the stereo Rick 4001 horseshoe PUP to the 8x10s and the toaster PUP to the 2x15s.
My other cabinets, used mainly with the Alembic Series II basses, are twin EV 18s in two custom folded-horn W-cabinets (huge) and they are powered with a pair of Macintosh MC-2500s strapped to 1000w mono each, like the Dead used to use. Clean and deadly powerful, lots of headroom. But too clean, compared to the two 1969 blue-line SVTs.
The first SVT head that is hooked up to the two original 1969 8x10 CTS stacks (with the original factory four-pin XLR jacks in the back) seems to fail a 6146A a little more often than the second SVT head hooked up to the two V4-B folded W-horn cabinets, each loaded with twin 15 Altec white-frames. Maybe it is impedance to the cabinets? I run the stereo Rick 4001 horseshoe PUP to the 8x10s and the toaster PUP to the 2x15s.
My other cabinets, used mainly with the Alembic Series II basses, are twin EV 18s in two custom folded-horn W-cabinets (huge) and they are powered with a pair of Macintosh MC-2500s strapped to 1000w mono each, like the Dead used to use. Clean and deadly powerful, lots of headroom. But too clean, compared to the two 1969 blue-line SVTs.
Do unto others as you would have them do unto you, and sit in with the band whenever you can, to keep your chops up!
That is why they switched early on to 6550's the 6146's couldn't take sustained distortion, you should use 6146B tubes BTW, they would last longer and are the specified tube for the heads, they are transmitter tubes and are stilled used today by many hams. I'm surprised that the head hooked to two SVT cabs fails more often than one hooked to two V4-B cabs, any open speakers by any chance in either cab, it's very easy to play with a blown speaker in an 8 x 10 and not notice it. I had a 1970 blueline Linden 6550 head and my late 70's heads sound just as good if not better.
Yes, I do run soviet-made 6146B with the bias fix on a regular basis, and keep the original set of RCA 6146A safely tucked away at home. Never wanted to destroy the collector value of the 1969 run by having the heads refitted to use 6550s, as Ampeg pushed for in the service bulletin they sent out in late 1970 to me.
As for speakers, well, you probably know a lot more about it than me, but my understanding is that the overall impedance of the 8x10 cab rises with each blown driver, since all 8 drivers are connected in parallel, and a rise in impedance causes lower power output from the head. So if anything, the lower plate current should extend the life of the tube, all other things considered. You will get more heating of the output transformer per amp of plate current, but that beast can take it because there are less amps at higher impedance, and the sheer weight of the head is largely due to the degree of overdesign for the transformer mass and windings.
I suspect that the true impedance of the 4 EV drivers are a little higher than their 8-ohm spec, resulting in an overall impedance for the 2 cabs in parallel of more than 2 ohms. By contrast, the manufacturing run of CTS 32-ohmers that month probably ran a little lower than 32 ohms, resulting in a paralleled overall impedance of a bit less than 4 ohms per cabinet, or less than 2 ohms for the pair of cabinets. All the CTS and Altecs are original drivers, never blew one in 37 years. The EVs are less than five years old
They've been blown more than once by the Macs....
As for speakers, well, you probably know a lot more about it than me, but my understanding is that the overall impedance of the 8x10 cab rises with each blown driver, since all 8 drivers are connected in parallel, and a rise in impedance causes lower power output from the head. So if anything, the lower plate current should extend the life of the tube, all other things considered. You will get more heating of the output transformer per amp of plate current, but that beast can take it because there are less amps at higher impedance, and the sheer weight of the head is largely due to the degree of overdesign for the transformer mass and windings.
I suspect that the true impedance of the 4 EV drivers are a little higher than their 8-ohm spec, resulting in an overall impedance for the 2 cabs in parallel of more than 2 ohms. By contrast, the manufacturing run of CTS 32-ohmers that month probably ran a little lower than 32 ohms, resulting in a paralleled overall impedance of a bit less than 4 ohms per cabinet, or less than 2 ohms for the pair of cabinets. All the CTS and Altecs are original drivers, never blew one in 37 years. The EVs are less than five years old
They've been blown more than once by the Macs....Do unto others as you would have them do unto you, and sit in with the band whenever you can, to keep your chops up!
Yes, that was a wise decision to keep them original, those heads are worth big bucks now. I've never heard one. I'm not an expert either but one thing I do know is that a tube amp will actually run better at too low of an impedance than too high. I also think they will drop off in power at both too high and too low impedances, they like to be matched. They are also forgiving in that you can run them a little too low or high and not have a problem usually. I have two early to mid seventies square back cabs with all original speakers also. Don't know whether they are CTS or Eminence but they sound damn good. (never took one out to accurately date them)
V4-B's are nice cabs I haven't played through one of those for probably thirty years.
V4-B's are nice cabs I haven't played through one of those for probably thirty years.
Bob and Elys, you're braver men than me. We play and rehearse in quite a few places that are up 2 or 3 flights of stairs (and I mean NARROW stairs), with no lifts. Even assuming my poor back was up to it, I'd hate the thought of carting an 8X10 up (or down for that matter) those stairs. I used to have enough fun with my 4x10....
"Be kind, for everyone you meet is fighting a hard battle."
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rhampshire
- Veteran RRF member
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- Joined: Fri Sep 22, 2000 2:47 pm
I think 8x10's are WAY easier to move than 4x10's. I used two Eden 410XLT's for a while - they're so awkwardly sized and STILL weighed 100 pounds a piece. Trying to get one up a narrow flight of stairs was a pain even with two people. With the 8x10 - tilt her back, one man on bottom, one on top, up you go!
Same with loading in and out of the back of my truck. It's MUCH easier for me to load an 8x10 by myself than a 4x10 just because you never have to lift the whole cab all at once.
Now the heads, they're another story - mine ride in flight cases and with the case it weighs 125 pounds or so...
Same with loading in and out of the back of my truck. It's MUCH easier for me to load an 8x10 by myself than a 4x10 just because you never have to lift the whole cab all at once.
Now the heads, they're another story - mine ride in flight cases and with the case it weighs 125 pounds or so...
I am paying dearly with a bad back for all those years in my twenties when I would slide the Tolex slipcover over an 8x10, then would grab it by the side strap-handle alone and carry it up or down stairs, or lift it up into my 1969 Dodge van. The cabs were lighter then, with the original CTS speakers circa 1969. These days, with the heavier ones that take more power and have much heavier drivers, I could never do it!
Do unto others as you would have them do unto you, and sit in with the band whenever you can, to keep your chops up!
I have slid them down stairs a few times and once rolled one end over end to get it up a flight of stairs (I'll never do that again, haha!) but have never carried them with the (useless) handles, I'm only 5'6". Up and down stairs are the only place I ever need help and I always get help, I'll stand there until someone from the band goes by. I mean a flight, 3 or 4 stairs are a piece of cake. I ripped the tolex off of mine and painted them black years ago.
The new ones are made of particle board, that is partially why they are so heavy. I put the heads on my shoulder if I have any distance to walk with them at all. I don't trust people to help with the heads, they always seem to slam them down.
The new ones are made of particle board, that is partially why they are so heavy. I put the heads on my shoulder if I have any distance to walk with them at all. I don't trust people to help with the heads, they always seem to slam them down.
It is only a LITTLE easier if you are 6'4" and beefy 
Still very heavy, despite the fact that the cabinets were made of seven-ply plywood and were loads lighter than today's particle board.
I remember how badly we ragged Hartley Peavey for starting off building his cabs out of particle board in the early 1970s. Cheap maybe, but way too heavy.
Still very heavy, despite the fact that the cabinets were made of seven-ply plywood and were loads lighter than today's particle board. I remember how badly we ragged Hartley Peavey for starting off building his cabs out of particle board in the early 1970s. Cheap maybe, but way too heavy.
Do unto others as you would have them do unto you, and sit in with the band whenever you can, to keep your chops up!