MyRefC build guide

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#861
bcmbob said:
Honestly, I haven't a clue about the final build/appearance of this project other than my desire to do a vertical/tower arrangement just for the sake of doing something different and unique.

Again, Thanks All.
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What ever it ends up looking like, I'm sure it'll be good!!

I have had all 4 of my amps running now and they are working fine at 40V (Make that 39.5V)

I can't really comment yet about the sound quality (driver is mounted in a cardboard box 😀 ) but these things have no on/off thump and are completely silent. No hiss at all with my ear a couple of inches from the driver.

I'm also quite surprised how cool they run. I just have them bolted to a piece of aluminium square tube, and the LM3886 only seems to get a little warm. R1 & R4 on the other hand do get quite toasty 😱
 
#862
HYPERTUNE said:
I'm also quite surprised how cool they run. I just have them bolted to a piece of aluminium square tube, and the LM3886 only seems to get a little warm. R1 & R4 on the other hand do get quite toasty 😱
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Congrats on your build - your LM3886s are definitely authentic. The fakes won't survive 40V for long, and the fakes are probably more prone to oscillations (if you put about 47nF of capacitance across the speaker terminals, even the authentic LM3886s will break into oscillation and heat up very quickly).

R1/R4 are rated at 2W each, which is fine for 32V rails and 12V for the LM318, which allows 20V/1k = 20 mA (max) into the zener shunts, and the dissipation is only about 20*20*10e-3 = 0.4W in each of R1/R4 (and about 0.25W (max) in each Zener).

However, at 40V rails, the quiescent current through R1/R4 increases to 28 mA each, which implies a dissipation of 28*28*10e-3 = 0.784W in each of R1/R4 - almost double that at 32V rails. That's why they're toasty, though there is still sufficient design margin left. The Zeners will also be a bit toastier at ~0.33W (max) each.
 
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#863
Thanks Siva.

Yeah, I bought the LM3886s from RS Components so I'd expect they'd be genuine.

I have to say these amps were extremely easy to put together. If any fellow amateurs out there are considering building them I'd highly recommend it.

With SO MUCH info here it might seem a little overwhelming at first, but in reality it's quite simple and the results are first class. Having the PS and protection circuit on board will make for a very clean and reliable build.

I purchased the V1.4 premium kit from linuxguru and the boards are beautiful 😎
They look so good I really don't want to put them in a case. 🙂

I also have to say thank you to Mauro. We are all very lucky that he decided to share this design, and I can only hope that he decides to come back and contribute again one day....
 
#866
Cersepn: Yup, I have both kits and bare boards available. Please send me a PM if there's interest.

Mark: Thanks, and the V1.4 gold-plated boards are indeed beautiful. I need to thank Wenhe (Kenneth) Ding at FlyPCB for that quality. Others may have had issues with the FlyPCB process earlier, but I only have praise for his prompt response and superb quality control. Just ensure adequate (say 12 to 16 mil) pad-pad, pad-track and pad-polygon (ground-plane) clearance, and all will be fine with the FlyPCB process.
 
#871
linuxguru said:
I notice that you've upgraded R1/R4 to Kiwame/Koa Speer CFR - is there a perceptible improvement in sonics?
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Sorry Siva, I forgot to answer your question. This was actually not an intentional upgrade as this build was not from a group buy or kit. I got four rev 1,2 boards from Uriah and did my own sourcing (yea - that sound is me pulling my hair out).
That is the part specified in Dario's latest Ultimate BOM. I think there are too many differences between this build and the rev 1.3 kits I got from you to make a direct comparison. Maybe Dario can/will add some info.
 
#873
Here's a quick pic of the part I received in the 1.3 kit. Don't know if it's the same in Siva's current offerings. This was from last December. I have absolutely no complaints as I added the Sonicap and Black Gate mods to this build and they sound great.

 
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#874
bcmbob said:
Here's a quick pic of the part I received in the 1.3 kit. Don't know if it's the same in Siva's current offerings. This was from last December. I have absolutely no complaints as I added the Sonicap and Black Gate mods to this build and they sound great.
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Cool - I noticed that your other boards were V1.2 Twisted Pear (red) boards from the last GB, but I did not recollect if R1, R4 were Kiwames on that BoM. With your clarification that you sourced the parts separately, everything is clear.

For improving the sound on the V1.2 board, there are numerous suggestions from Tom, Dario and others on various threads, and I'll add my 2c (which may include some of their suggestions):

C1, C2: Nichicon Muse KZ (100uF/50V will fit)
C6, C11: Black Gate PK, Elna Cerafine/Silmic II, Nichicon Muse KZ
C7: 10 or 22nF/63V Wima FKP2 or Evox PFR
C10, C34: Silver Mica (Sangoma, CDE, El Menco or similar) or C0G ceramic
C4: 100-150nF Wima MKP2
R10, R11, R13: Carbon film resistors
R7: Kiwame 12k/0.5W CFR (for warmth) or Holco H4 12k/0.5W MFR (for a more analytical presentation). Both will need to be mounted vertically or have their leads bent underneath to fit into a V1.2 board.
ZD1, ZD2: On Semi 1N5349B 12V/5W Zener (tight or vertical fit)
 
#875
Siva,
Am I correct in assuming you are the only current source for MyRef-C PCBs and those are V1.3 and V1.4? I've had a couple people ask what is available and who has it. I did some source helpers for new builders back on post #1245 on the other thread and those were based on Dario's BOM for V1.2.
I really like your kits but some might want to strike out on their own in an attempt to combine all or some of the published mods and recommendations.

http://www.diyaudio.com/forums/chip-amps/134726-new-my-ref-rev-c-thread-125.html
 
#876
bcmbob said:
Siva,
Am I correct in assuming you are the only current source for MyRef-C PCBs and those are V1.3 and V1.4? I've had a couple people ask what is available and who has it.
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Bob, I do have V1.3 and V1.4 PCBs, for which I did the layout modifications using the Twisted Pear V1.2 as the baseline. It's entirely possible that there are others with small caches of unpopulated V1.2 boards from the previous GBs.

The current kits are V1.4, but with slight alterations I can create kits for V1.2/V1.3 if somebody already has PCBs and specifically wants a kit tailored for it. The changes are almost entirely related to the physical size of the components, and the schematics are all functionally equivalent (give or take a few bypass caps).
 
#878
Unfortunately I did both the Blackgate and the Sonicaps at the same time and cant say which did what. I can say that the combination opened a wider and much clearer window that filled the whole room. The impression of depth of stage was amazing. Even after several months the amps continue to improve at every use.,

In my case, it's very important to let the amps warm up for at least 30 to 45 minutes before any serious listening.
 
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#879
For comparisons of specific components used in building this amp, I suggest you go to the New MYREF C thread. Discussing such topics here has been frowned upon.

The quick story: I contend the BG is by far the best cap in this position. Dario maintained for a long time that the Silmic was superior, but I'm not sure how he feels now that he has lived with the BG for a while. I did not like anything about the Silmic, especially the way it killed resolution, putting high frequencies under a blanket, preferring even a Panny FM to it. I gave mine away.

Please let us know what you think, but it would be best to post in the other thread.

Peace,
Tom E
 
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