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'70s Ampeg V4B questions

Discussion in 'Amps and Cabs [BG]' started by Osobass, Nov 16, 2003.


  1. I'm in the process of picking up a vintage early 70's Ampeg V4B through a reseller that knows very little about the amp other than the fact that it has recently been re-tubed. The power section tubes are 7027s that look new so I'm pretty psyched. The amp sounds good, but I didn't get to play it long enough to figured out all of the beta.

    The channel 1 input and channel 2 input are apparently designed to get different sounds. Does anyone know what the different inputs are for? I've looked up the pre-amp schematics on the web, but I don't really understand the schematic enough to figure out the intended purpose of the two inputs. Any info on these amps would be helpful.

    Also, any suggested power amps to run as a slave for more power?
     
  2. Don't neuter the tone with a power amp. Mic it with a D112 or a 421 and keep all the tone you deserve.
     
  3. Rockbobmel

    Rockbobmel Supporting Member

    I have the V-4 model and the channels are normal and bright. The V-4B is the same amp, except it uses different tone filters voiced for bass. I use the normal channel but if it was the V-4B, I prolly would use the normal also. The bass is huge on these amps and too much IMO. They were made when speakers were trial and error engineered and if the speaker was enimic you could EQ it easy. I don't know by definition the differences in channel voicings. Just screw around with the tone till you like it.
    My 70s V-4 is my favorite sounding amp. Next is my Sunn 2000s, Then the Mesa 400+ Then my Bassman 135.
    Get it if it is in good shape. It's prolly worth $400. to $450. You may want to talk him down a$100. because generally these amps need a cap job. The tubes are likely to be fine. Check out the threads on tube replacement. There's a lot of discussion on it.
     
  4. Can't wait to pick this baby up! I put money down today, but can't get it till it comes off police hold on 12/5.

    Is channel #1 normal and #2 bright?

    What's the story on a cap job?

    What cab do you use for your 100W all tube head(s) to harvest the tone? Plan A for me is an SWR WM15T, but 10s seem more appropriate.
     
  5. The 0x

    The 0x

    Aug 24, 2003
    Timonium, MD
    [​IMG]
    Or Silverface if you like:
    [​IMG]
     
  6. Rockbobmel

    Rockbobmel Supporting Member

    Cap jobs are done because electrolytic caps dry out over the years. There are several caps in the amp. Dried out caps are bad for tone.
    The cab - or cabs of choice are effecient ones. Look for High DB rating like 100db or higher. This amp is LOUD and you may not need a slave amp as you mentioned. Mesa Boogie and Eden cabs are efficient. I'll bet the new Bergantino NV series cabs would be killer.
     
  7. That Bergi NV610 looks awesome! Back to reality though for a bit...

    I have a 4 ohm cab and a 2 ohm cab. The combined impedance would be something like 2.67 ohm. This amp has a selector for 2/4/8 Ohm load. I'd like to use both cabs, but don't want to damage the amp. Can I run the head at the 2 Ohm setting when it's really driving a 2.67 Ohm load? What will be the effect on the amp???
     
  8. Rockbobmel

    Rockbobmel Supporting Member

    Yes. I do it all the time, and there is extensive info on this in the archives here. Daisy the 2 cabs together.
     
  9. Rockbobmel

    Rockbobmel Supporting Member

    Oh, I think Psycho said it is better to go to the next HIGHER imp. on a tube amp. But a small mismatch does not matter much.
     
  10. After reading the web link, I'm not sure that I want to risk damaging the amp by using any load other than exactly 2,4 or 8 Ohms to match the amp selector switch options.

    Does anyone have long term experience running a vintage ampeg tube amp into a lower ohm load than the head is set up for. The web link suggests that it would be ok, but not great.
     
  11. Running into a lower load isn't going to do damage. Tube amps are different than solid state amps; lower output impedance is OK; it's higher than expected output impedance that's damaging. You will lose some power (probably 20-25 watts maximum) by running into a lower load, but unless you sustain extreme high current low notes through a minscule load, you don't generally risk damage to a tube amp. What web link are you referring to?
     
  12. This was posted under the Tube Amps heading:

    "Tube Amps
    Tube amps do not directly drive speakers. They use a transformer instead. To make a long story short, a tube amp won't be harmed (much) if the impedance of the speaker cab(s) connected is too low, but it won't work well or may even die on you if the impedance of the speaker cab(s) is too high. The worst you can do is to connect no speakers at all. Modern amps have additional circuits to prevent damage. Don't count on it. Some tube power amps can be switched/adjusted to different impedances. Make sure they match."
     
  13. The channels are NOT normal and bright on the V4. Both channels are the same. Look at the schematics, same tube, same caps, same resistors.

    What can be done easily, though: two guitars could be used (though I wouldm't recommend simultaneously), each with different sensitivity or volume.

    Or one guitar/bass could be plugged into an A/B selector box, which then plugs into each input. Different sensitivity and/or volume could be set for the two channels. Select Channel A, plugged into Channel 1 for example, and have quieter rhythym, or select Channel B plugged into Channel 2 with the sensitivity set more sensitive and have more volume/distortion for lead.

    On somebody's particular amp, Channels 1 and 2 may sound different--one brighter than the other--if one of the preamp tubes for a particular channel is getting soft, or maybe somebody has done a mod.....But according to the schematic on the lid of my V4 and the schematics drawn by Joe Piazzi (don't remember his spelling) either channel is the same.
     
  14. Rockbobmel

    Rockbobmel Supporting Member

    Sorry, I forgot. I didn't mean to be misleading.