40w @ 8ohm/60w @ 4ohm pure Class A build:

hydrovac

Well-Known Member
Joined
Jan 10, 2007
Messages
1,226
Points
113
Location
Hyderabad
Trying a 40w @ 8ohm/60w @ 4ohm pure Class A power amp... got the prototype modules for evaluation from a friend who designed them.

1725937608425.jpeg


1725937629843.jpeg

Building mono blocks... trafo 0-24-0-24 secondaries @ 7amps, PSU with 15000uf x 6 filter/smoothing caps and large heat sink weighing 7.3kgs for each channel.
1725937732577.jpeg

Holes drilled for securing the module on heat sink.
1725937698146.jpeg

...
 
Module clamped and secured to heat sink...
1725967546069.jpeg

Wired up... DC offset reads 97mV... need to set it close to zero.
1725967725302.jpeg

Bias reads 170mV across R38, 5watt resistor 0R22... will set it to 200mV (that amounts to 800mA) and check the heat sink temperature.
1725967838447.jpeg

Both the channels ready for test...
1725968687387.jpeg

Radiator placed vertically....heat is gradually building up.
1725967941484.jpeg

...
 
Last edited:
Thanks all,
Been playing the amps for a while and the heat is pretty much stabilized at 60 to 65 deg C... made couple of prototype chassis to make sure the assembly, workability and serviceability are addressed, before ordering the pro enclosures from Nishant.

As the heat sink is 250mm tall, planning to restrict the width to minimum possible and make slim front towers...

1726452863049.jpeg


1726452884044.jpeg


1726452924432.jpeg


1726452986666.jpeg


1726453025115.jpeg


1726453049493.jpeg


Though a tight pack, everything seems ok... Nishant shared the below design of enclosures which he ordered for fabrication.
1726453279774.jpeg


1726453334645.jpeg


1726453348468.jpeg

...
 
Sorry for posting trifle late. I've had the privilege of listening to these beauties driving the B&W DM602s last week. Even with the lossy Logitech Bluetooth interface, the glorious Class A sound was presented in all its glory, source being Tidal, Qobuz and Spotify. We played a variety of test tracks, many of which, I had taken from an FM from Mumbai, whose name is Nilesh, a great guy with an impressive pair of DIY speakers and a carefully curated hifi system. @hydrovac is old school and is clinging onto his CD Player; even using it to play WAV/ FLAC files copied to a pen drive. Having experienced the likes of Qobuz and Tidal from my Paradigm PW Link and smitten by the convenience they offer, I have coaxed him to convert as well, to buy a same Streamer that had incidentally come up for sale in his circles. By the time I made my third visit in as many days, the Paradigm had arrived.

(I have pestered him and got his help in building a Class A Single-ended amp, of which, I had got two fully populated and tested modules. That's for a another thread. Hence the third visit in quick succession).

After setting up the Paradigm, rather than pairing up my phone which has all the streaming services, I had suggested that he download Spotify which he did diligently. We played one of his favorite tracks, 'Endaro Mhanubhavulu' a Carnatic music track by Uttara & Unnikrishnan. The crystal-clear notes of the dense music along with the sweet vocals of Uttara came out beautifully. He was bowled over. I asked him to reserve his opinion till he subscribes for Tidal, which he took no time in subscribing. I'll try to post a detailed review whenever I visit him next.
 
Get the Wharfedale EVO 4.2 3-Way Standmount Speakers at a Special Offer Price.
Back
Top