MyRefC build guide

[linuxguru]

Originally Posted by wrankin

One component in the delay circuit does differ from the value printed on the PCB and that is R21. Siva specs a 100k and the PCB (vers 1.3) lists a 220k. I haven't payed too much attention to it, but from a quick glance I would hesitate a guess that increasing R21 would increase the delay time.

Yup, there was a discussion about a year or so ago by AndrewT and BillP, among others, about the default values in the protection circuit, and the occasional failure to turn on. I found that R14=180R and R21=100k gave more reliable turn on, without loss of protection capability, than the original values, for both the Omron and Goodsky sugarcubes.

It may cause a brief turn-on/turn-off thump, but that's mostly curable either by decreasing the value of C13 or altering the power-on sequence (e.g. Source - MyRef or vice versa).

[bcmbob]

This subject may not be fully appropriate on this thread, but please bear with me for one more question (lots of knowledgeable folks around here for brain picking)

I have a Denon receiver that has a long mute (~2 sec) while the LED readout shows several things happening. I suspect that delay is a programmed process as opposed to simple relay and resistor design.. Does anyone have knowledge and or experience with the program/IC approach?

Thanks

[bAD kLOPFER]

There are so many threads about the My_RefC that it was hard to decide where to post a "FINISHED..." (As you see I decided to post it here ).

I had it running in mono-configuration a couple of weeks ago and I finally assembled the second channel yesterday (I got the kit from Siva). The amps have a DC-current of 3.5-5 mV (left channel) and 4-7 mV (right channel) - my multimeter isn't so good so the result did some "changing" while measuring. After half an hour of "slightly louder than normal" playing the LM3886 measures at 39°C and I have around 45°C in the area of the zener-diodes (is this normal?).

I still have to improve the wiring but I was eager to test the amp with the volume control and input switcher. There is nearly no hum (if muted all there is is silence ! ). I got some hum when I completely disconnected the input wires but as I said this issue will be addressed the next few days with the wiring (I guess this is the main problem). I attached some pictures of the amp running.

To say something about the sound: My Needle RS show bass and punch they never showed with my old Sony Receiver (you might see it in the pictures). I'm very pleased with the performance of the amp. As it is the first amp I assembled on my own, I think I'll have a good glass of wine after lunch .

Many thanks to Siva for the support and all of the people who invested so much time in this amp and posting their ideas/questions/answers in this forum.

Best regards
Sven

[bcmbob]

BK - Welcome aboard. The amps just keep getting better sounding with time. Let me suggest the Mundorf power caps and siva's LFO1 as items to consider if and when you want to bump it up a bit. Even a stock MyRef though, is indeed an amazing little amp.

[udailey]

Goood job Sven! Hey, dont let that big film cap get in the way of best sound. Either remove or use something better.

[bAD kLOPFER]

Thanks a lot . But I enjoy listening at the moment and have some parallel projects running. So, I'm happy that it works. If I come to think about "pimping" the My_RefC I think there are so much ideas here in this forum that I'll have enough to read and to try out.
But first I want to enjoy the amp as it is and probably give it a nice enclosure.

Best regards
Sven

[udailey]

Right on. Have fun

[ClaveFremen]

Originally Posted by bcmbob

Let me suggest the Mundorf power caps and siva's LFO1 as items to consider if and when you want to bump it up a bit.

Originally Posted by udailey

Goood job Sven! Hey, dont let that big film cap get in the way of best sound. Either remove or use something better.

Two spot-on suggestions.

I know you're enjoying your brand new My_Ref and with Siva's premium BOM you're starting from a very good point...

... but one thing, IMHO, you should consider to do before casing it.

Replace R13 with a Mundorf Zn 1.2uF 250V, you won't regret.

Or at least search on eBay a much chepear NOS Vishay MKC1862 1.5uF 63V, not as detailed and transparent as the Zn but delicious.

[bAD kLOPFER]

Hello, I already asked Siva for LFO1 PCBs. Maybe I'll have some free time in the future.
All of your suggestions are welcome. I think they're the most important tuning tipps of hundreds of posts in this thread.

Thanks a lot

[Milos P.]

Hi
do I still need input cap(c13), my tube preamp have output cap with 10K resistor to ground.
Cheers