Class A hybrid power amp up and running

The unit I've mentioned here and there over the past few weeks as being a WIP is playing in the background as I type this

For now it's powered by two bench PSU's, a large commercially built unit (physically large anyway but only 2 x 30V @2A output. Used here in parallel to get 4A max @ 30V), and my DIY valve hybrid variable regulated PSU giving 250V and 6.3V for the valve stage. The 30V max of the bench PSU limits output to 12.5WPC for the moment but that's no real issue for me as my Leak Stereo 20 is adequate in terms of power. I have a large toroidal transformer ready for it which should give 18WPC (higher powers can be obtained with larger heatsinks and higher PSU volts obviously) and 176,000uF of smoothing capacitance waiting in the wings.

It passed all bench tests this afternoon including the important square waves into reactive load. A 10KHz squarewave looks really nice!

Only been on for half hour and new components running in etc so early days to give any idea of the sound but certainly not bad so far

 

Any photos?

S.

 

No.I have learnt from bitter experience after posting photos of prototypes in the past that those who may be interested in such photos generally have one of two motives:

1/ To try and reverse engineer your new baby, if photos are detailed enough. I consider everything I design proprietary and whilst I'll probably never sell any or make a penny from it I'm damn sure no one else is going to!

2/ People who don't know their arse from their elbow criticise it because they haven't a clue what good engineering practice actually is and think all components should be laid out symmetrically, in perfectly parallel rows, and with tightly bundled wiring looms all bent at precisely 90 degrees..... even on a one off prototype! (as an aside here, I've noticed loads of equipment these days where the innards have obviously been designed to look nice to the non technical [with compromised performance because of this], as many different brightly coloured capacitors as possible, red, blue or black PCBs and everything laid out completely symmetrically even when by doing so they've had to run the tracks from the transformer, carrying huge current spikes, for 10" in order to get the smoothing caps in a nice neat row down the middle etc! Oh then there's the "go faster" legends like "super linear sound transformer" written on top of said article)

Oh and to add a third one, people who don't know a resistor from a radish but have drank the hi fi kool aid will start criticising/offering advice based entirely on what brand of capacitors or wire you have used!


Must be just me but I can't see any point in photos of hi fi gear on forums in general unless they illustrate a particular point ie show someone which gear wheel in a cassette mech to replace. I find it bizarre that people seem to want to look at simply a pic of an amplifier sat on a table etc

 

In my case, just interested. I know what my rat's nest prototypes look like, and get a mild kick seeing others'.

As to components, indeed!

By the way, I loved the resistor and radish. I'll definitely use that one myself.

S.

 

Was going to post pics of the DIY variable regulated supply for valve kit as I'm quite chuffed with it but it seems one must use an image hosting service. It's "finished" and anything I want kept out of public view is inside... It's also hybrid and has a 6550 output valve driven by an ECC81. High voltages and solid state will usually end in tears with something like a bench PSU where shorts can and will occur eventually, hence the valved output and driver stages.
It is built "old school" on an aly chassis, neon power light, Elstone transformer etc but inside it is SS and precision. 100 - 350V in 3 ranges with 100mA max output, very low output Z and noise, output voltage is set by a 10 turn vernier dial and you can dial in lets say 312V and this is what it will output to within around +/- 20mV... yes that took some doing!
Heater supply is regulated by a very low drop-out discrete regulator of my own design and can give 3.5A. Getting 6.3V regulated DC from a 6.3V AC winding was erm... "fun". All SS power electronics are inside the unit so from outside it looks like a 50's - 60's all valve bench PSU.... well if you ignore the modern smoothing caps anyway!