Heavy Metal Amplifier

[Ray P]

I collected the andised internal U channel sections of my SissySIT chassis on Friday and have started assembly of the amp.

First up is the power supply, all integrated onto the rear U channel section. 500VA (2 x 18V secondary) Toroidy transformer and a soft start-up control board on one side and two bipolar CRC supplies on the other.

Lots of work to do!

[Ray P]

I've been working on the SissySIT amplifier again today - I left off for a while after injuring my shoulder in a fall and didn't feel comfortable doing the metalwork that was required. Anyway, I've now completed the metalwork for the chassis and the main sections are assembled.



The chassis is ready for the PCB to be installed and hooked up.



and the top-plate is ready to bolt in place - it will hold the power switch, input sockets and volume attenuator.

[Ray P]

A little more assembly today - now ready to start installing the amp board.

[Ray P]

Yay! I've installed the amplifier board and have the first channel of my SissySIT set up and playing music!

I'm only using my mobile phone as a source and a bare test/sacrificial speaker so far but it sounds nice and clean sounding if a little quiet - I guess it needs a bit more drive on the input.

Set up was easier than I expected thanks to the comprehensive instructions from Zen Mod on DIY Audio.

I won't push my luck so I think I'll leave it there and get some fresh air.

[Ray P]

Hmmm. I'm wondering if I've made an eror by having the two autoformers too close together - what do you guys think?

Could I mitigate the proximity with some grounded copper shielding, or perhaps a small piece of mumetal sheet?

[ed]

Hmmm. I'm wondering if I've made an eror by having the two autoformers too close together - what do you guys think?

Could I mitigate the proximity with some grounded copper shielding, or perhaps a small piece of mumetal sheet?

wait and see...otherwise there's no way of knowing the answer to that one.
afaik you're the only person in this parish that's been financially foolhardy enough to build a SIT...respect!
I do hope you bring it to the next owston as MZM has been biggin it up for long enough now....nothing like a good bit of hype to preclude a spectacular disappointment......
no but seriously I reckon it will be awesome.

well fugly to quote ZM

[Nick]

Cant see it being a problem. the flux will keep to the cores.

[Ray P]

Thanks Nick.

afaik you're the only person in this parish that's been financially foolhardy enough to build a SIT...respect!

Ed, if you want to be second I have a pair of Tokin SITs I can equip you with? Very reasonabe guv, honest!

[Ray P]

I've just been setting up the second channel of the amplifier and all good so far. Taking a break for lunch before I hook up a speaker and source.

[Ray P]

I have set up the second channel of my SissySIT, which went swimmingly, and have been listening to music in stereo through some proper speakers, albeit a pair of old Mission floorstanders and via dubious temporary hookup wire/connections. I'm using a headphone amp as a preamp as the source is currently just my smartphone (playing FLAC media files) - the 6dB gain of the HPA is just right. I can already hear how good this amplifier is!



The only minor issue is a tiny bit of transformer buzz that I'll need to check out, though it is inaudible unless you're within a metre of the amp.

All I need to do to finish the project is to fabricate front and rear panels and hook-up the socketry.

[JamesD]

Hi Ray,

I've been admiring your different builds - I've got a few Sony V-fets in my stash along with a couple of 0.8C/W heatsinks for a V-FET build but can't decide on a circuit for them - it will be an adaption of one of the PASS or ZM circuits with a bit of my spin on it .. one day....

Hope we get to hear this one day as it should really good! Very impressed on the mechanicals too!

ciao

James

[Ray P]

Thanks James. I can already tell that this is going to be an excellent amplifier with just my 'test arrangement' so I'm glad I decided to take the pluge with it. It's using Tokin THF-51S SIT devices, just one per channel.

I'm also working on a choke-loaded Follower using the same devices that I plan to use for the full-range drivers in an open baffle build.

All being well I'll bring these (plus the OBs and my DSD DACs) to the next Owston meet-up.

I also have the LU1014D parts and PCBs for a Pass F3, a couple of 2SK60s that I would like to try in a pre-amp and I also have two pairs of Tokin 2SK180 SITs that I need to find a home for.

What Sony FETs do you have? DIY Audio will soon have available boards/kits for Nelson Pass's latest VFET amp.

[JamesD]

I have 8 2SK82 and 8 2SJ28 and a selection of toshiba and linear sk170 and sj74

but I fancy using the V-Fets in a CFP with the V-FET AS THE CONTROLLING DEVICE AND BEEFY TOSHIBA BIPOLARS AS THE SECOND DEVICE RUN AT A GAIN OF 3-5 (sorry for the caps! finger trouble and no energy to correct... No brain power to work through the design - I will sim in LTspice one day...

Really looking forward to hearing these and discussing these designs...

ciao

James

[Ray P]

You might want to check out the Luminaria pre-amp James. If I had a pair of 2SK82 devices I would certainly build one but those devices are unobtanium now. I'm waiting patiently to see if the designer will deliver a 'lite' version using 2SK60s.

[iansr]

Ray, where did you get that U channel - Ive never seen any that wide before.