I do find no small irony that Nelson designed this amp to be a great performing, SIMPLE design, delivered same and yet folks just can't resist "messing" with the amp.
Seems to me that if you want more you ought to be building an F5 Turbo.
I resemble that remark
My query about the PC power supply was prompted more by a desire to save a few pennies by using what's on hand - if possible. Also have a chassis design that would aesthetically benefit from not using a brick. The only way I know how to get an answer is to ask a question. I would suspect any designer would allow some tweaking. If not - we wouldn't see version numbers on PCBs.
In my case, the ACA is an introduction to something other than LM3886 based amps. It's a journey I've been contemplating for about three years. With that in mind, I have ordered and am expecting delivery on a F5 design based kit as a next step. Had a couple nice phone conversations with the folks at PassDiy and 6L6 about where to go after that - if necessary.
So I'm looking forward to this new adventure and am already thrilled at the quick and informative responses found in the "House Heater"
community.P.S. I do have two 18.5V laptop bricks I will use for the initial build. Plus - the Peter Daniels PCBs are on the way. If not here, they will be put to good use with other projects.
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OOps! I didn't order any mica pads as I'm used to the insulated LM3886TF chips. I do have a supply of thermal insulating tape left over from some computer projects. Will that be sufficient? It's 10 mils - maybe two layers?
BTW: Has anyone pointed a laser thermometer at the ACA when in full operation?
BTW: Has anyone pointed a laser thermometer at the ACA when in full operation?
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Using an 8x3" heatsink similar to the one in the diy store, I found that it runs pretty hot. It was 48 deg C on the chip and around 35 deg on the sink after about a couple of hours. Wonder what it will be like in the summer. I would suggest using a bigger sink for this.
I think it's just great t hat people mess with this amp. They might learn some stuff. My only concern would be that people might assume that it NEEDS to be modified, and that's not true at all. Just build it stock and you'll be amazed. Mess with it and you'll have some fun and it might sound even better to you..
Oh yes, exactly! Stock just as it comes is really wonderful.
As soon as I finish putting it together I will get some more parts and start to play with it. There lots of good ideas in this thread. Plus I will have something to listen to while I experiment!
I do not think it needs to be modified in terms of sound. I am very impressed. Not really pretty sitting in my office. I thought up putting it in a nice chassis, PSU board and transformer, etc. Started adding up the costs and thought it would be better to invest in an F5 build. This amp did stoke my obsessive compulsive behavior and it got me hooked on a new hobby! The UPS man keeps coming and wife keeps asking "How much is this all going to cost?"
and it got me hooked on a new hobby! The UPS man keeps coming and wife keeps asking "How much is this all going to cost?"
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Initial impressions after a week or so of playing it through a full range speaker(Alpair 7.3 in a BIB). The sound is closer to my Aleph 3 than the F5. Warmer, better mid-range etc. But ultimately it did not measure up to my SET2A3 into the same speaker. The SET actually had better extension -both upper and lower- than this amp which was surprising.
But it is a great little amp and dead quiet. It is going to be the center piece of a smaller system that I plan to put together for near field listening. And off course I have to try a non-smps to see what that sounds like.
I think that is one of he charming things about this amp. I slapped it together in a couple of hours once I had the boards from parts I had lying around including heat sinks and laptop power supplies. It is a nice little diversion from the all the other bigger projects that await me in various stages of incompletion - speakers, amps, dacs, cd players, turntables and I don't know what else. So many things to build, so little time!!!
Shucks. I ordered 0.68 ohms @ 2 watts instead of 3 watts for R3-4. Can I use them till I get the proper pieces.
Don't like green smoke !!
They should work fine.
We got light and music.
Built a chassis or stand (your choice) from pieces from other projects. Using four CPU coolers and the bulk of the aluminum angle the temp stays just above room temperature.
The power transistors are insulated with heat transfer tape instead of mica and seem to work as required. I'll keep my eye on them.
The level is very low, but high quality with my test speakers and the amps being fed with a Walkman. After safety burn-in bigger speakers and a pre will be tested.
Still have to devise a cover - maybe plexiglass - and some nice wood trim.
So my introduction to "The World Of Pass" has been fun and productive.
P.S. One of my 18.5 V bricks has a plug that's too big for the sockets I bought so I haven't had stereo yet - but they both sound great. A trip to RS tomorrow will take care of that.
Built a chassis or stand (your choice) from pieces from other projects. Using four CPU coolers and the bulk of the aluminum angle the temp stays just above room temperature.
The power transistors are insulated with heat transfer tape instead of mica and seem to work as required. I'll keep my eye on them.
The level is very low, but high quality with my test speakers and the amps being fed with a Walkman. After safety burn-in bigger speakers and a pre will be tested.
Still have to devise a cover - maybe plexiglass - and some nice wood trim.
So my introduction to "The World Of Pass" has been fun and productive.
P.S. One of my 18.5 V bricks has a plug that's too big for the sockets I bought so I haven't had stereo yet - but they both sound great. A trip to RS tomorrow will take care of that.
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You don't have to break it down, just make sure the interface between the angle bracket and copper needs to be as smooth as possible and have a bit of heatsink grease on the interface. That will increase the heatsink efficiency and likely take the case temp down.
Thanks guys, but I guess I used the wrong words. By "break down" I meant removing the one or two mils from the copper plug, not removing it. That would add the full surface of the aluminum part of the heat sink.
I use a series of emery papers glued to a piece of granite, ending with 1600 grit so the contact surfaces are almost mirror like when finished. The copper plug does have Arctic Silver applied now, but I'll eventually use the full face. For subsequent projects I do have access to a surface grinder but this one was small enough to do by hand.
Hope to hook up the ACAs to big speakers and a pre later today.
I use a series of emery papers glued to a piece of granite, ending with 1600 grit so the contact surfaces are almost mirror like when finished. The copper plug does have Arctic Silver applied now, but I'll eventually use the full face. For subsequent projects I do have access to a surface grinder but this one was small enough to do by hand.
Hope to hook up the ACAs to big speakers and a pre later today.
Maybe a little trivial, but do you feel a compound like the white grease might be more effective than the CPU stuff I'm using. I'm aware there are proponents of both, but personally haven't noticed a lot of difference in the computer cooling projects. I'm going to order some mica pads to replace the heat transfer tape and can add what's recommended to the order.