Dating fender bassman head
I caraked open the top on my 1975 YBA-1 just to look, and sure enough it's a 68K.(Dave, Nov 11, 2014) - corrected version (Brian, Craig, Dan Lear, Dave Rutherford, DCloud1050, Eric Knudsen, Glen H., Greg, Jay Rogers, Jonathan Krogh, joth, Kraig Olmstead, Moon Keith, Ron Waters, Tim Casey, Tony Flagg, Vernon Fitch, viva Analog at bc.ca/~jc) Features Two channels (bass and guitar), two inputs for each channel, upper inputs are slightly attenuated; Treble and bass controls, a "tone expander" section with low and high knobs (according to Dan Torres, these are actually midrange and presence controls); there are two volume knobs that can be blended to get different sounds.
Sound - Reliability - Price CAD $395 [used], condition unknown, Scarborough, Ontario, Canada, February 7, 2001 Very hard to find. Dyna-Bass, front view, angle (apparently the same as the following) 1963 Dyna-Bass, serial number 0011, front view, angle Features Two channels, deep (bass), and bright (guitar); each has an attenuated and a normal gain input (like the old Marshalls); no reverb Volume control channel one, channel two; treble, bass, low range expander, high range expander (passive); the low range expander may sound like a mid-range, the hi range expander may sound like presence (on Marshalls or Fenders) to some (the section is a virtual clone of that of the Marshall JTM-45); standby switch; pilot light; ground and on/off switch; no fan One main speaker output, impedance is not indicated (runs fine using a cab of eight ohms, also often operated with four ohm loads), one "extension" speaker output also without indicated impedance.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 (?437 volts); this may have gotten higher after 1971, but into the summer of 1971 I'd expect the plate voltages on 6CA7s to be down substantially from the YBA-1A; have the chassis sliding-in ala Fender.Last versions have that easily identified rubber and 'chrome' molding running around each end of the head cabinet; mine is from 1971 and is this last version; 1972 models have no choke; [a 1978 is] black with the black plastic fabric and [has] the baby bumper trim, [it has] two 6CA7 and three 12AX7A tubes in it [and] no fuse holder, just a red reset button I put Mullard EL34s in my YBA-1.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 $253 used, bad price, amp in average (5/10) condition, Song Bird Music, Ottawa, Canada, summer 1998 US $125 [used], needed a little work but playable, cheap buy US $299.99 [used], seen at September 1998 CAD $189 [used], good condition, seen at Used Music, Ottawa, September 1998 CAD $150 [used], shabby condition, very early (pre October 1966) wrap-around type case model with tube rectifier, seen at Used Music, Ottawa, September 1998 CAD $115 [used], ca.
The 2nd one I bought [...] was totally moded for guitar with extra pots on the back and stock EL34s. I [...] have [an YBA-1A Mark II amp] that goes with [the YT-15 cabinet] and it's all sounds great. i believe, though i am not sure, that these 1a's operate in class "a". Other than the old no ground power cord and serious shocks and buzz it sounded better than what i was using.
i stuck a master volume on the back, jumped the channels, and cranked both channels to 7-8, plugged in my custom shop '61 reissue sg, and it kicks so much ass [through 4x12 25w greenbacks] its indescribable i bought both a 1971 yba-1 and a 1972(? [...] the yba-1a is currently beating the snot out of an old mesa 4x12 with 90 watters in it. this would make sense to me considering how very crushing it is and yet chimey. The only real problem was it seemed to be blowing fuses.
Reliability It's a risky proposition for repairs Old and still going strong Price I bought my YBA-1A [used] about 15 years ago for $62 USD.
[...] The 2nd [used] one I bought off ebay [for] $235 USD was totally moded for guitar with extra pots on the back [...].
The YRM-1 is good sounding, but not as responsive, raw, or soulful as my YBA-1. presently using the yba-1 through an old sound city 4x10 which i respeakered with 80 watters. breaks up like a champ when driven and sings sweetly when i turn down the pickup volume(s). It's a beautiful computer-drawn schematic, but an error was made in transcribing the previous schematic.