Dirty Girl Coronado 1x15 Combo Amp - Used  From Other

At long last, the mighty Coronado!  In all actuality, I’m not really sure why the moniker “Coronado” has been ascribed to these amps, as the late 1950s catalogs always referred to them by their proper model numbers:  1690T w/ 2X10 speakers, 1695T or 1615T ‘Accordion’ w/ 1X15 speaker.  Regardless, it does sound a bit mysterious and potentially brutal, and this interpretation is certainly an apt description for these dirty beasts.

A Little History:

Often viewed as a bigger, badder 1624T, this is somewhat true as most of the late 1950s Valco amps had a very similar sound despite differing volume levels.  Here, the 1624T control layout (my ‘Heavy Hindenburg’) is mated to the increased channel-two gain of my ‘Plus’ variety, and the whole shebang is then fed into a dual 6L6 output section.  The original versions of the 1690T/1695T/1615T were based upon 6L6GB tubes (ca. 1957), a 5V4 rectifier and a good degree of screen constraint to keep the current in check and thus provide a truly beautiful “squish” when driven.  These are the dirtiest versions of these amps and are absolutely perfect for those who are rollin’ in it all the time!  

Sometime ca. mid to late 1958, the circuit was slightly modified to make use of 6L6GC or 7027 tubes (both can be found) and higher voltages; here we see much less screen constraint, a 5U4 rectifier and a larger output transformer, and so the amps became both louder and possessive - finally - of some noticeable clean headroom.  These can compete pretty closely in volume to a JTM45 combo although (as with most Supro-branded amps) the circuit is directly oriented toward a mid and upper-mid focus, and the smaller cabs help to retain some of the squawky, boxy nature of the 1624T that we all know and love.  They do not have the typical bass extension of the larger Marshall cabinets or dual 12” speakers.  

Fast forward:

I’ve put a great deal of thought into this particular model in order to capture exactly the essence and tone of the original amps while introducing an updated practicality.  The original amps were a split-chassis design (power amp chassis and preamp chassis) to fit the entire assembly into a very small box (given a dual 6L6 amp).  This layout creates a number of issues, multiple connecting cables carrying both line AC and high voltage DC foremost among such issues to my mind.  Furthermore, the AC line voltage running in the same cable as the preamp power feed introduces added noise.  Combining the split-chassis of the originals into a single chassis while using an improved grounding scheme drastically lowers the noise floor but has no effect upon the circuit or tone of the amp.  Like the vintage 1690T, I have taken pains to keep the cabinet comparatively small so as to retain portability and avoid alteration to the frequency response of the amp.  Finally, if requested, I can alter the tremolo to affect *both* channels via the output tube bias (as opposed to the preamp tube bias wiggle of the originals) in the same manner that the tremolo is modded in my ‘Hindenburg Plus.’ Either way, the final effect is the same swampy, primitive type of tremolo that one expects to hear in a Valco-made amp, but in my modified version, it is now usable on the brighter channel as well as the slightly lower-gain grid leak input channel.

Two versions are available, the earlier version (“Model 1”) or the later version (“Model 2”) as both are described above.  The earlier version can safely utilize 6L6GB/5881 or 6L6GC tubes, and is fitted with a n.o.s. 5V4 rectifier.  It can also use 6V6 tubes if a 5Y3 rectifier is used for slightly reduced volume.  The second version is designed around 6L6GC/7027A tubes ONLY and utilizes a n.o.s. 5U4 rectifier.  Additionally, either variation can be authentically supplied in a 2 X 10” speaker format or a 1 X 15” speaker within the same cabinet size.  The 2 X 10” 1690T style tends to maintain a faster, snappier response with a heavy emphasis on the upper mids (all mids, all the time), while the 1 X 15” 1695T/1615T style introduces a greater bass and treble response and overall a slightly more ‘scooped’ tone.