VASE: Bassman 100 amplifier

I ended up selling this one before doing any real work on it, as I decided that I have enough projects on the go right now, and I couldn't decide if I wanted to leave it stock, or mod it to suit my tastes.  Probably a bit bigger than what I currently want to work on as well - I think I prefer the idea of lower wattage, probably single ended combos.  So if you find this, good luck Mike...   

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Despite the name, it's not a Fender Bassman clone, however there is a clear resemblance in many areas.

VASE AMPLIFIERS

Victory Audiophonic Sound Equipment, better known as Vase, is a brand of amplifiers from my hometown, Brisbane, Australia.  They were handmade by a small team, often custom-built for customers. Vase was active from the late fifties through to the early seventies. They were very popular at the time, given the high tariffs and expensive shipping costs for imports into Australia.

Not so fun fact:  the founder of Vase, Tony Troughton died from a jellyfish sting in the mid seventies - welcome to Australia.  

I remember back in the 1980's, Vase was popular with the more indie crowd and anyone who wanted a decent amp but couldn't afford a Fender Twin or JCM (including the first band I ever did live sound for - yes, I'm a former Sound Engineer if I never mentioned this).  I would say that they were considered a great clean pedal platform before the term was coined.

I think they only had a few models with minor variations on each one - no practice amps or budget models; these were all very well-built, powerful amps.  The Vase Trendsetter is easily the most well known version, and it came in a variety of wattages, from 40w to 120w.  Generally they lacked reverb, and some had vibrato. It was quite common for amps to have multiple inputs, with just bass, treble, and volume controls.

Vase speaker cabinets are quite diverse - heads could have been matched with any number of options.  Unusually, standard quad boxes were not there thing.   12” two and three speaker cabs were common.  I believe they made quite a few column speakers too, for large venues.  Alnico MSP speakers were commonly used, as was Etone and Celestion in later years.

VASE BASSMAN 100

So, onto my project.  I believe the amp is from the late sixties, as the power transformer has a 1966 date code.  It features inputs for guitar, bass, and organ, with two channels, each equipped with bass and treble controls (more on that later).  It is somewhat like a 1965 Fender Bassman, but there are also some clear difference, especially the input options.  

Cosmetically, it's challenging to determine exactly how much is original, as they apparently offered custom builds.  I'm pretty sure the black carpet is not from the sixties; however, the green fabric is similar to another Vase I've seen in black, so this may be original.  Either way, I like the green, so it's staying.  I doubt the knobs are original, but I'm not certain, as they show a lot of age - they look as old as the amp itself.  I'll probably leave on them as a result of this.

• Serial number 2529   
• 2 x 12AX7, and a phase splitter
• 4 x KT88 output valves 
• Silicon rectifier
• PVD110 transformer for power
• OPM21A transformer for output (my best guess anyway)

Lights on the front panel are red for standby and green for on

August 1966 date code on the output transformer 

This amp generates bias voltage via a transformer fed from the heater circuit - it has Vase 7000B handwritten on it. 

Construction is a mix of matrix board and point to point.  Carbon film resistors and mustard caps. Insulated wiring to get signal to and from the pots, which is nice.   Pots are Ducon.

Someone has recapped most if not all of the filter caps, a valve base has been replaced and there's a random carbon comp resistor sitting amongst the carbon film resistors.  That mess of silicon and caps in the top left is clearly not original.  There should be a couple of caps sticking up through the chassis there.

The inputs and channel arrangement is unusual.  Interestingly they placed the preamp valves directly between the jacks and the matrix board, for the shortest possible cable runs - clever.  

One preamp triode shares the bass and guitar inputs, the other is for organ.  This is how the two channels are split.  The bass and organ inputs are grounded when not in use.  

The inputs aren't all the same, and each channel has slightly different EQ section, both have a mid-scoop.

• Organ input:    straight to the grid, nice and simple, earthed when not connected
• Guitar:             1n cap & 270k resistor in parallel 
• Bass:                47k resistor in series, earthed when not connected

The two volume controls are post eq, and before a gain recover stage, which feeds the phase splitter.  The phase splitter and power amp stage is fairly standard from what I can tell.  Quite close to Fender, but without negative feedback.

• The Guitar / Bass side could be jumped into the organ side via a path lead - could be interesting  
• Depending on how it sounds, I may jumper the 1n / 270k on the guitar input and possibly play with the bass input as well, as they interact directly with one another.

ADDITIONAL VASE RESOURCES

Oz valve amps Vase link

Reverb Vase amp background

TECH DATA - SCHEMATIC

These are really notes for my own benefit, or perhaps another Bassman 100 owner may stumble across this and find it beneficial.  The schematic is mostly correct - I have not fully traced the transformers and power / standby switch etc.  

The grid leak resistors are very low compared to most amps.  I'm hardly an expert on valve amps, but I've never seen anything this low.

The connections with bass and guitar interact a bit more than I like.  The bass input is grounded when not in use, meaning the guitar input has even more of a voltage divider in place than it already has.  Not sure what the thinking was here.     

POWER TRANSFORMER - FERGUSON PVD110

Combines with diodes to provide 500V B+

OUTPUT TRANSFORMER - FERGUSON OPM21A

My guess it as the time, this may have been the only 100w output transformer that Vase had access to, even if it had a slightly weird output impedance.