JANSEN: TR25 Solid State Guitar Amp from NZ

This is a fairly obscure solid-state guitar amplifier from New Zealand - I don’t know exactly when it was made, but it does scream the 1970s.   I bought it a few years back and have been using it as my test amp in the workshop/garage.

I haven't been able to track down a schematic, so this morning I pulled it apart to see if there was anything obviously wrong - there was a bit of corrosion, and some insects have been using it as a home at some stage (not uncommon in Australia for an old amp).  I gave the board a clean, and there was also a broken stabilising spring in the reverb tank, which I repaired.

It's rated at 25w, and it's very loud.  Single 12" speaker of an unknown brand - not sure if it's original.  Controls for volume, bass, middle & treble, tremolo and reverb.  It does have a really nice tremolo and combined with the reverb it can do a pretty cool vintage-sounding clean tone. 

JANSEN TR25 SOLID-STATE GUITAR AMPLIFIER

Looks like they used quality parts back in the day, with a couple of massive 3,300uf capacitors across the power supply

Sanyo STK029 Power Amplifier 

One very dirty circuit board - gave it a good clean before putting it back together.

Small Accutronics 2 spring reverb

Broken suspension spring

CROWTHER: 1977 Hotcake

 I probably said enough about the Crowther Hotcake (and New Zealanders) in the previous post - so I'll stop now.   Short story - it’s straight op amp clipping with some filtering.   

Although I should say that this has an unusual bypass system - it's not true bypass, note the switching.  I’ve included a modded layout for standard true bypass switching.    

CROWTHER 1977 HOTCAKE VERO LAYOUT

CROWTHER: Hotcake

Invented in the late seventies by Paul Crowther, the drummer from Split Enz (yes, the drummer).

As an Australian, I can only say that this was almost certainly invented by an Australian and then stolen by a crafty New Zealander - just like the Pavlova, ANZAC Biscuits, Lamingtons, the Flat White and Phar Lap.  But not Russell Crowe...  he's definitely one of yours.

It's an interesting design and sounds pretty good, with the drive running a decent amount (it definitely needs the reverse log pot).  One thing bothers me - while it runs from very clean through to a thick drive, almost fuzz, distortion artefacts can be faintly heard in the background when running clean.  Not a deal breaker by any means, as who wants to run a distortion pedal clean right?

CROWTHER HOTCAKE - VERO LAYOUT

A WORD FROM MR CROWTHER