One [channel] sounds kind of like a "bright" channel and one sounds regular Two 6CA7/EL34 power tubes, three or four 12ax7s, solid state rectifier; hand wired, very high quality work, simple easy-to-modify circuit; larger [than the ones used in the Bass-Master YBA-1] 50-watt Hammond transformer (7 lbs.); Often operated with 4 ohm loads; best used with an eight ohms cab Runs on 540 volts, weights 54 pounds - bigger transformers [than the YBA-1] Dimensions: 8"x18"x10" (HWD); weight: 40 lbs.? (source: Catalog) Early [Bass-Master] Mark IIs have the (noisy) fan mounted on the end [in the cabinet side], later [Bass-Master] Mark IIs (with lift-off top, and the reflector 'Traynor' logo) have it mounted in the back [center]; Silvery grey grille cloth; Can exceed 600 volts on plate; expect about 550 volts, if you're lucky (one has eported 537 volts on plate) Early models are identical in appearance to the Voice Master/Signature.
I have swapped out the 4M volume pots for 1M, and put a 47K resistor in the NFB loop.
I've used it regularily throughout the years, gigging throughout the Detroit area, and later in the E. A plate load of 6K8 would have essentially zero gain and probably lots of other problems.
That part of the hand-drawn schematic from 6/1971-1974 is smudged and hard to read, but it's definitely 68K.
The used tubes are, as indicated in the amp: Two 6CA7s (replaceable by EL34s) and three 12AX7As (also called 7025s or ECC83s); plate voltages have always been a question on these units, but I think this may be largely because of confusion with the YBA-1A models that run VERY high plate voltages; most of the YBA-1 models probably come in somewhere /-450 volts (one has reported 425 volts on plate, another one ca.
I have swapped out the 4M volume pots for 1M, and put a 47K resistor in the NFB loop. Professional repairman required, although schematic is included, weird defects possible. The YBA-1 serial number is 8011108 the YT-15 serial number is 7125596.
These mods are worth doing to any Signature/Bass-Master, IMO. CAD 3 used, bad price, amp in average (5/10) condition, Song Bird Music, Ottawa, Canada, summer 1998 US 5 [used], needed a little work but playable, cheap buy US 9.99 [used], seen at September 1998 CAD 9 [used], good condition, seen at Used Music, Ottawa, September 1998 CAD 0 [used], shabby condition, very early (pre October 1966) wrap-around type case model with tube rectifier, seen at Used Music, Ottawa, September 1998 CAD 5 [used], ca.
These mods are worth doing to any Signature/Bass-Master, IMO.
Sound Just like a plexi 50 watt Marshall (when used for guitar); Punk or loud rock (or with channel bridging Entwistle's bass sound) (when used for bass) Better sound as a Fender Bassman (bass and guitar); lower powered, would work just fine in a blues or lower volume setting (?