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Ampeg positioned the V-4B-U as a reissue of the original 1971 V-4B, a 100-watt all-tube bass amplifier head. The reissue was designed to reproduce the tube tone and character associated with the original model while incorporating a more compact form factor suited to contemporary use.
The amplifier runs a full tube complement: two 12AX7s in the preamp stage, a 12AX7 and 12AU7 as driver tubes, and four 6L6GC output tubes delivering 100 watts RMS. A three-band tone stack is supplemented by a three-position mid rocker switch, giving the player discrete mid-frequency options rather than a continuous sweep. Ultra Hi and Ultra Lo voicing switches are present, along with a -15 dB input pad for high-output instruments. The rear panel provides a balanced line out, preamp out and power amp in jacks for signal routing flexibility, and a slave output. Speaker outputs cover 2-ohm, 4-ohm, and 8-ohm loads. The cabinet measures 24 × 11 × 11 inches and weighs 41 pounds.
Owners requiring tube replacement, output-transformer service, or bias adjustment should consult a qualified amplifier technician familiar with high-voltage tube equipment.
Nothing in The Vault is for sale. These records exist so the instruments stay documented after the manufacturer moves on — and the most useful part of that record is what owners add to it.
The catalog shot showed one finish, under one light, a long time ago. Yours has been played. Photos from owners are what the next person finds when they are trying to identify a part, match a finish, or work out whether the one they just bought is really what the seller said it was.
Specs only go so far. What actually fits, what breaks first, what the factory got right and what everyone ends up changing — that lives with the people who own them, not in a datasheet. Post what you know and it stays on this page for whoever comes looking next.
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From spec questions to full builds — players who have lived this gear since 2007.
Since 2007
