A60(+) Amplifier. Build this?

Hi folks. It’s good to see some activity here. i have been working on an A60++ for a while now. I got bogged down on the chassis build. After pricing 6061 at my local metal supplier I decided to build a chassis from bits of aluminum I had on hand. I would like your opinion on the 2 front panel options below. One option is to leave the bare aluminum and have 2 rectangular mounting holes for the meters. The other is to have the area blacked out with the meters installed and an acrylic cover over the entire area. In the photo below I cut out a piece of black plastic to size so I could see what it would look like. This is similar to what Accuphase and Luxman do on their amplifiers. There are pros and cons to both but I like the looks of the blacked out version better. The lower portion of the front panel is a 4 inch wide by 1/2” thick piece of 6061 that I had used in a tube amp I built almost 25 years ago. To replace that piece would be well over 100$ Ca. As scrap it is only worth 5$ so I decided to recycle it for this project. The 2 vertical pieces above and at the ends of the lower plate are about 8mm thick and the top frame piece between the 2 verticals is 10mm so I am going to bevel the edges to get a nicer look. The panel where the meters and indicator lights will mount is 1/8 inch 6061. If anybody has suggestions, comments or advice please let me know your thoughts.

I have a simple question. With the stock feedback resistors of 33 ohms and 1k what is the final gain folks have been getting with this amp? I’m not sure how the current feedback arrangement will impact the gain. It looks like 30 which is also close to 30db. Input sensitivity would be around 1volt. I have a single 35v 800va transformer. I’m going with fan cooling and bias around 100ma/ output trans pair so 800ma total. Supply voltage tested out to about 45-47 volts with a simulated load. I have an NTC surge suppressor setup to limit inrush current and then bypass the NTC.
Heatsink arrangement is below. The board mounts on top of the heatsink pair and transistors mount near the top of each heatsink. They are roughly 4 inches high and 12 long. The fan mounts on the front side and the back side of the heatsink is at the rear panel where there is a grill to let hot air exhaust out the back of the amp. Air will be drawn through filters on the bottom of the chassis to the sides near the front. I tested this setup by clamping 8 25 w aluminum power resistors to the heatsinks and using a DC power supply to get 100w of power into them. Temps stayed below 45c even with very low air flow so it should be fine for my planned 80 w/channel or so.


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Deleted member 543346

Is that Open Circuit Voltage or you have measured that voltage under full load?
Under load voltage will be lower, but good 63V vapacitor will survive.
No i have only the output boards right now , but i also plan to build Wolverine amplifier and was thinking to buy transformer i can swap from A60+.
If i am happy with the A60 then i will buy separate transformers for Wolverine.

I simply looked at A60 schematic and saw 50v and 18v (or was it 17?)
Net voltage is fairly stable around 230v
I am using Kemet ALC series 10000uf 63v , and rest is Nichicon gold tune.
For the smaller transistors (2240/970) i will use smd style...i think.

Edit: This is my first build
Sandt nok, men jeg kan ikke engang midlertidigt montere målerne på dette tidspunkt. Jeg gætter på, at det, jeg er ude efter, er meninger om den sorte baggrundstype målermontering, som bruges af Accuphase og Luxman for eksempel, versus den bare målermontering på frontpanelet, som bruges af de nye Technics- og Yamaha-forstærkere.
And.Dette websted oversæt fra engelsk til dansk og er umuligt at indføre
2sc2713 and 2sa1163 i bought at Digikey.
Also need adapter
Thanks, I already have adapters. I just have to order from Digikey.
I also have tried by substituting transistors with KSA992/KSC1845 but that substitution has made distortion worse.
Also, I must say thad CDIL and Chinese 2240/970 aren't bad at all. Here, on this forum, someone has published results confirming that these transistors are low noise. I have made measurements using transistor curve tracer and have confirmed adequacyof these transistors from these "untrustworthy" sources. I think it is about the time to gain more trust in these emerging manufacturers. By the way, China and India produce everything, we just purchase their products from "trustworthy" sources, and pay substantially more just for the "good name".
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Deleted member 543346

Yes i beliveve cdil is good. Reason i thought about the smd variants is that i allready have them since i do repair units where 2sc2240/2sa970 frequently appears.
I will mention that the smd variants are harder to match in my experience.
Will order the cdil's for future repairs and backup , and maby i end up using them in this application aswell.

Btw did you measure hom mutch watts yours deliver?
Read trough the whole thread , and happy to see others share their builds and experience
Btw did you measure hom mutch watts yours deliver?
Thanks for the information.
Honestly, this is the only amplifier I didn't bother measuring the maximum power. After I have seen the square wave response I said "That is enough. I doubt I will ever see something like this".
Its' limits are about +/-42V rails (in my case) so it can't deliver a lot into 8 ohms but with such a massive output devices it can deliver lots of power into low impedance speakers or even more if bridged. A60+ can deliver a lot of power, but I don't own disco club and some of my neighbours have sensitive ears. However, I have lots of headroom. Right now I'm building a 150 watts per channel into 8Ω Jeff Rowland model 10 clone, not because of power it may deliver but because of the headroom it has along with very low distortion.
Good luck with your projects!
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