finally, a vintage V4B!

Discussion in 'Amps and Cabs [BG]' started by nil, May 2, 2001.

  1. Man oh man, have I been searching for a while for one of these!
    Here's the fun part; I haven't even seen the amp in person or even played it! Don't even know when i'll be able to get it home to play it (i'm in NZ, the amp's in the US)...aarrgghh! I want it now! :( :D

    Not a bad price, $250 and it looks pretty good for it! Now, I wonder how long this amp will last before I need an SVT?

    Chris - are there any tricks/gotchas/etc I should look out for (seeing that it's the same vintage as your V4B)?
  2. Congratulations on the amp! When I bought my vintage V-4B it needed new capacitors; the originals were shot. It also received a tube conversion to 6550's. My tech did a lot of little things to make it perfect (and bring it back to life--it had been neglected by the previous owner). I'd get it looked at by a pro to make sure its functioning at 100%.

    I really love my V-4B. I have pondered getting an old SVT but haven't done it yet.

    Tell us how it sounds when you get it.
  3. Pretty much what Sapo said covers it.

    You could use good quality 6L6GC's if you desired, but when my 7027A's finally die (they haven't in about 10 years!) I'll probably put in some Russian 6550A's.

    You'll need new filter caps if they are original, which they probably are, and they are multi-section can type (=expensive). You could very easily build the equivalent capacitance using individual caps in some of the open area of the chassis. This would require a few extra terminal strips, but would probably be cheaper. I did this on my Ampeg B25, which is like a 50 Watt version of the V4B. Get a schematic for the V4B here and memorize it:

    The amp uses the normal 12AX7a's, 12AU7a, but it also has the oddball 12DW7 and 6K11, in addition to the 7027A's. You can still get 12DW7's and 6K11's pretty cheap, though.

    It will probably play pretty good with the original filter caps, but to bring it up to original specs, you'll definitely want new power supply filter caps. They're the 70 uF/450V, 40 uF/450V, 40uF/500V caps in the power supply.

    The bias is fixed to one voltage, so it will need to be made adjustable to sub in other tubes. This just requires a 50K linear potentiometer and 33K resistor ingeniously soldered in place of the 56K bias network resistor.

    Make sure you always set the impedance selector correctly. It's good for 2, 4, or 8 ohms. 100 Watts in any position. That's one good thing about tube amps, is the fact that they'll do full power into more than one impedance. I'd try and use the highest impedance possible, so that you're getting your power from higher voltage instead of higher current. (Current heats up the windings, voltage doesn't, that's why power is transmitted over hi-voltage wires.)

    That's all I can think about. Mine is still stock, and sounds great. Heavy as lead, but great sounding. The input circuit on a V4B is different from most amps, and it results in a really cool sound. On my Fender Jazz, the tone control acts differently when plugged into my V4B. Turning down the knob cuts the tone, but the treble edge and bite is still there. It's weird at first when compared to what you're used to when turning down the tone on a bass, but you'll see that it's a better sound than anything else you've played. That's its secret, I think, that 5.6Meg input resistor, no grid block resistor, a 390K load resistor, and an unbypassed 3.3K cathode resistor. Unbeatable. I'm gonna copy that channel into my Bassman and see how it does.