Ampeg V4B

[dadagoboi]

V-4 and V4-B, close enough for rock and roll.  And 3 caps away from being the same tonally except for the 'Ultra Low' switch according to this guy.

http://stonemarmot.com/rants/?p=38

[Stjofön Big]

You guys never stop to amaze me! This is absolutely something I'm gonna dig deeper into! Thanks again!

[Basvarken]

http://www.ebay.com/itm/Ampeg-V4-Guitar-Bass-Tube-Amp-/220880390289?pt=LH_DefaultDomain_0&hash=item336d7f4891

http://www.ebay.com/itm/Ampeg-V4-Guitar-Amplifier-Excellent-Condition-/180744411645?pt=LH_DefaultDomain_0&hash=item2a1534d9fd

http://www.ebay.com/itm/Ampeg-V-4-Tube-Amplifier-80s-Vintage-/120799605193?pt=LH_DefaultDomain_0&hash=item1c2037b1c9

http://www.ebay.com/itm/Ampeg-V-4B-vintage-/260880331558?pt=LH_DefaultDomain_0&hash=item3cbdadf326

http://www.ebay.com/itm/Ampeg-V4-100-Watts-Bass-QOTSA-Guitar-Amp-Baby-SVT-/190592070671?pt=LH_DefaultDomain_0&hash=item2c602c340f


Get it back in shape or build your own:
http://www.fliptops.net/catalog/index.php

[lowend1]

I've seen one of the 7027A/6550 labeled amps - it was a MV-equipped VT40 (the later front panel variety) at a guitar show years ago. The note was silk screened onto the rear panel with all the other stuff.

From Ned Carlson's (Triode Electronics) FAQ page:
>>Some models of Ampeg V-series specifically say on the cabinet schematic that 6550 (or KT88 or KT90, they are all interchangeable) can be used directly in place of the 7027's. Others don't...there's several varieties of all these amplifiers, since changes were made through the years of production. There's probably a few odd variations floating around that even serious Ampeg experts haven't seen! At any rate, if you want to make darn sure your 'Peg 'll handle the extra current draw of 6550's, plug 'em in and check the voltage across the filament lines (pins 2 & 7) of the output tube sockets. If you're getting much less than 6.3V AC, then it's no go.If that checks out OK, then let the amp run for awhile, and check how hot power transformer is getting. If it's getting too hot (it'll get warm but shouldn't burn your fingers), you've either got to go back to 6L6's or change the negative bias so the 6550's aren't drawing as much idle current.

Note that a lot of folks have used 6550's in these model Ampegs for years..but there's always that odd exception, and we don't want you blowing up a power transformer, so we strongly suggest checking this stuff out as noted above.

Q.So where's the bias adjustment?

A. Ain't none.Some folks with the knowhow can install a bias control adjustment in an Ampeg,and it's a neat idea, since some folks might like the sound of tubes biased hotter (higher than the 25-35 ma you'll typically see), and tubes like 6550 can certainly handle a bit more current. But I would note that because of the high (over max published ratings) screen voltages, I'd play safe and not bias tubes for more than 75% of rated dissipation (plate current X plate voltage): eg: for a 6550, not more than 30 watts, for EL34 or 6L6, not more than 18..tho some 6L6 and large bulb 6CA7 might be able to handle 25.

Q. Are you sure about that 6550 thing in the bigger Ampegs?

A. Yep. Here's a couple of pertinent comments...

Lord Valve Stateth:

Some of the later ones, the master-vol types made while Ampeg was still Ampeg, say right on the schematic that you can plug 6550s in with no mods at all. It's down in the really small print with the 'notes'. LV

Bluemuse wrote:

Ampeg literature from the mid-70s for the VT-22 and VT-40 at least, say there was a Performance Kit available consisting of four 6550 output tubes and tube retainers, yielding 130 watts from the normally 100-watt VT-22, and 80 watts from the normally 60-watt VT-40. I don't know if there is anything else besides the tubes that was included in the kit.

[Psycho Bass Guy]

I don't care how the amps were labelled. 6550's won't work safely without having the bias circuit modified, period.  The "upgrade kit" was Ampeg's way of selling off excess stock SVT power tubes and was supposed to be installed by an Ampeg service center, and the bias adjustment would have been done at the same time. Like the "requirement" of two cabinets for the SVT, it was a marketing ploy and nothing more. I don't have a problem with using 6550's in the V-series Ampegs, but it's not the end-all be-all magical sound change it is often made out to be. I do prefer the sound of 6550's in them, but for the average musician who will have to find and pay a good tech to do the work, it's an unneeded extravagance.

Also note that in regards to modern tube types and makes discussed in the link that I posted and lowend quoted, the information is fifteen years old and some of it is now outdated and incorrect.

[rahock]

The date on that information really could be a big deal. Several years back, the best techs around were all jumping on the 6550 swap as being the best bang for buck mod out there for anything that ran 6L6 tubes.  A few years later the same guys were changing their opinions to it's good on some and dangerous on others.
I'm no tech and I am somewhat talking through my ass here, but I am one of the guys who did get away with the swap on a cheapo Airline amp . A few years ago I went back to the 6L6 tubes anyway based on the advice from PBG.
Rick

[Psycho Bass Guy]

There was a long period of time in the 90's through the early 2000's where it was pretty hard to get decent 6L6's. Mesa and most dealers were either selling crooked-glass Chinese junk or Sovtek 5881's. New Sensor hadn't started making true 6L6GC's yet and Svetlana's production and QC was very irregular, as was EI's. There was no JJ Electronics.  Even crappy Chinese 6550's would work fine in circuits designed for 6L6GC's as long as their heater current draw didn't kill the filament windings in the amps' power trannies; that's also discussed on Ned's page. The outdated info is in regards to the then-current 7027's; AFAIK, all the ones being made now meet the actual 7027A/6L6GC specs.

[lowend1]

PBG, in your experience, do the current 6L6s produce full power in something like a V4/V4B? What are your personal faves (that are available now) in terms of performance/reliability?

[Psycho Bass Guy]

I'd trust the JJ 6L6GC's, KT66's, and the New Sensor "Tungsol" 6L6GC, "Electro Harmonix" 6L6EH, "Svetlana" (NOT Flying C) 6L6GCSV, and Sovtek 6L6WXT+. I've had positive experience with older examples of  Svetlana/Flying C 6L6GC's, but they've been having lots of problems lately. I've also not had much trouble finding old stock US made 6L6GC's, but I realized that I may have just lucked out. 

[stiles72]

I've had good luck with the Sovtek 6L6WXT+ in my B15 and V4BH.  They seemed to have a little more output than the JJ's I had been running, and I don't notice any real difference in the tone.

[rahock]

I've got a set of JJ 6L6s in an old Gibson Atlas and they provide a cleaner sound with a little more headroom before breakup than most tubes, and I have a set of Winged C 6L6 tubes in an old Airline/Dano which have a much earlier break up and sound identical to the old Motorola tubes that  originally were in the Atlas.
Rick

[bobyoung]

I had a V4-B head years ago with RCA 7027A's, it was a nice sounding head but lacked for headroom. I used to use it for rehearsal. SVT's always sounded better to me, the ultra lo was voiced a little different I think.

[Psycho Bass Guy]

6550-based output sections have an inherently stronger sub-bass extension because the 6550 has over twice the peak current capability of the 6L6GC and current=bass.

[SGD Lutherie]

Used a vintage V4B in the mid 90s. Didn't have enough headroom for a loud rock band.

I had the same experience back in the 70s with one. Nice sounding, but not loud enough unless you want full blown Felix Pappalardi.

But then Everett Hull didn't like loud music. 

[Stjofön Big]

All right, you guys. I followed your lead, and got me V4. Bought it from a well known Swedish organist/bassist who had two of them. Told me it'd been in for service half a year ago (when new end-tubes (?) were installed), which I find believeable, as the guys a professional musician. The V4 seems to have been taken care of very gently. The end tubes
The sound is, as you guys above told me earlier on, great. I don't regret one bit buying the V4 instead of a V4B, though that would have been great, also. I guess my amp is from around -76, as it don't have the distortion knob. 2 channels, bass, mid, treble, the (for me) unnecessary reverb, and master volume.
I've only tried the V4 out in my rehearsal place, but I can compare it to my Fender Dual Showman, and know that it, concerning volume prestanda, will do anywhere in the places I'm used to gig. I've placed in on top of my 1x15, and 4x10 Ampeg cabinets, and I really enjoy the feeling of a small earth quake that I get in company with my G-n Ripper with T-bird pup.
I haven't decided yet whether to go with your thought of changes, Dadagoboi, but I might in a while. Just for the joy of it.
Again, a big Thank's for you helping me in my desicions, fellows!