How to Pass a little time ...cont

Got in on the ACA mini clone board buy and Nelson was a legend as always and provided the Harris output devices. If an amp can be cute, it's this one. Perfect desktop size at roughly 5 inches square. My desktop setup is not for critical listening so this is not a review. I'll just say it sounds wonderful. Perfect project for someone wanting to get into DIY whenever it makes it to the DIY store. Parts cost was ~$200 so I assume that's how much the kit will end up being.

Using a WHAMMY as preamp.

 

I wanted to take the speaker wire and RCA cable strain off the ACA mini circuit board and also wanted some minimal protection from accidental bumps. And needed to keep the whole thing well ventilated since the heatsinks are internally mounted. And I didn't want to put too much effort into it. Also added a P089ZB SMPS filter. Got some makerbeams and precut aluminum squares from Amazon and ended up with this

 

Hi
One question, based on the early M2x prototype, post #1 picture https://www.flickr.com/photos/15794984@N02/44156803184/
Would the author say the thermal were OK with those heatsinks ? (for like 2h listenning session in a 21 degrees C environment)
Thanks a lot if the author has an answer
Have a nice day

 

It gets hot and as I keep it inside a shelf, I use a base with a fan in it. I have used it without a fan too but it gets to 50deg C

 

Nelson Pass' temp scale (hand on heatsink):

"Blimey hot is 10 seconds hands on = 45 deg C.
Crikey hot is 5 seconds = 50 deg C.
Bloody hot is 2 seconds = 55 deg C.
X*?@! is 60 deg C.

All of these are within an acceptable range, although X*?@! is reserved for the more mature constructor."

 

then this is at least 60 deg

 

Thanks! Nice to know you used a fan under it when inside a shelf. I am debatting a chassis for an M2x. Size wise, i would like a Mini Dissipante 3U (from Moduloshop / Hifi2000). I thought your initial built might be a good comparison.
Given what you mention, Mini Dissipante 3U might be too little dissipation for passive cooling.
Have a nice day

 

For a desktop solution it doesn't make sense to use a preamp so I've added a passive pot. I suppose I might as well throw the guts of a Modi in there and make it a full fledged integrated lol.

 

I wonder if I should add a couple of small (10uf?) caps at the pot. Any thoughts?

 

It looks like the amp has an input cap on the schematic, that should block DC from getting through

 

Doh! You're so right.

 

Just found this thread!

I'm in the process of completing my SissySIT R.3 monoblocks and I must say that these are shaping up to be the best amp I've heard to date... So long as you're not chasing after the 0.0001% THD figures anyways.

It's just so organic. It's like combining the best qualities of the tube and SS amps I've heard.

I've also read that these Tokin VFETs, while used in a lot of industrial applications like mentioned on the first page, were also used in radar power amps -- and, those who have heard both the SIT-3 & and the Tokin version ended up preferring the Tokins. Take that with a grain of salt, of course.

I'll have to share more impressions in the future once the monoblock conversion is 100% complete, but these are shaping up nicely.

 

@sp33ls and pictures please - would also love to see what the rest of your system looks like. I couldn't agree more that this is a very special amp..dB

 

My setup is relatively humble at the moment due to my temporary apartment situation. I'll be moving soon and will likely end up looking between the Spatial Audio X4's or Zu Union 6 Supremes. Currently using GR Research modded RP600M's for the space-saving aspects. They don't sound bad by any means, but they're the weakest link in my setup.

Here's my SissySIT monos:



Took advantage of Tom's Neurochrome boards for soft-start and speaker protection. Using a "Smooth Like Butter PSU":


Ended up adding some bulk capacitance and could really only fit them underneath the PSU PCB lol:



I'm also currently using a Pioneer Exclusive C3 for the preamp (as in my profile pic):



Tho, I may end up replacing this with a Yamaha C-1 so I may have a full VFET chain.

I only just completed the monoblock conversion for the SissySIT, but man... am I impressed. Such an organic sound. And, not at the expense of anything else. It's not like it's "tubey" in the potentially negative ways that tubes are described. It's like it takes the pleasing distortion profile of triodes and combines it with your Pass Labs flavor of speed, dynamics, and transparency. It's only 25-30WPC, but boy does it have composure over my inefficient RP600Ms. I gave it a quick test at painfully loud levels and it doesn't sound stressed at all.

I hope many other friends here get the chance to hear one for themselves someday.

 

Are those the new Modushop mono enclosures?

 

They are indeed! Worked out nicely.

 

not that I need to build more stuff but as I may have mentioned in the past, Nelson is my therapist and keeps me distracted and out of trouble

I had been reading about cap multipliers and Patrick in DIYA posted a simplified version of the M2 output stage and this got me thinking of a good use for some large heatsinks and SMPS supplies that had somehow appeared in my workspace

Not done, but I figured a few pics to provide context of what is to come

The Capacitance Multiplier is a venture on DIYA and gerbers were available, so I had a few PCBs made



as you may notice, I messed up on the pin spacing of some of the smaller caps and thus installed them on little extenders which then necessitated a little stabilization and hot glue.

capmx test - 24V out from a 28V supply




M2OPS - this is the M2 output stage - opto biased but also has an opamp on the front end as a buffered input ( this is unity stable or can add gain )




all boards in stages of assembly



I finally tapped the heatsinks and mounted the MOSFETs and set it up ready for final hook up and testing.



the end point is a balanced output amp , hopefully there is enough metal there to handle the necessary heat , if not, a fan or 2 will be added to this little experiment.

..dB

 

I am also working on a Patrick project... or staring at the chassis and pcbs anyhow. I wish I had split up my orders more, I am just sitting around waiting until mouser has my entire order in stock. Honestly I am livid with how mouser has handled my order. I would suggest NEVER using their ship when everything is ready option. They sell out the items you have already paid for that were in stock so you have to wait longer for them to ship. Their cs rep told me they don't do that, but clearly they do... like 15 times to a single order.

Oh well, back to my regularly scheduled lurking ;/

 

Yeah, I have learned the hard way too. I now order if there is enough to justify shipping. So many projects have had to be stalled because of parts availability.

On happier things, I wired up one of the channels and it all fires up, voltages from the capmx stable and both boards bias up to about 1.2A with offset zeroed

.. dB

 

and it lives

M2OPS making music

after hooking up without a load, I let it cook for about an hour nudging the offset to zero ever so often - it was at 10mV at initial start , so no major adjustments needed.

attached the test bed speakers - some donated Bose 201's from the 2000s , no start up thump , absolutely dead silent at the speaker cone, music - well it makes it and sounds as good as it can in this environment - so promising for things to come

I am using an SE/BAL input card from XRK audio

..dB