Group Buy: Mauro Penasa MyRef Rev C kit

[gobble]

Bought PTFE (teflon) insulated 15AWG red, black and white wires for power and signal cabling. Didn't buy termination clips as they were available in packets of 500 pieces only!

Careful with the wires. Teflon is not a magic ingredient - I once got teflon dielectric insulated wires @300/- per mtr for my preamp and it sounded horrible. A 40/- per mtr pvc insulated shielded wire worked wonders providing a pitch black background and outstanding silence with neutral tone. 40-40 lapping is what the market called it and it was as soft as silky human hair.

Cheers

 

[stereorules]

Found time after 2 long weeks to order cabinet from Dinrack. It will be a 2U (meaning 3.5 inches height outer dimension), 19 inch wide, and the depth will be 200mm (a bit less than 8 inch).

Whats the cost like ?

 

[josephjohnt]

Careful with the wires. Teflon is not a magic ingredient - I once got teflon dielectric insulated wires @300/- per mtr for my preamp and it sounded horrible. A 40/- per mtr pvc insulated shielded wire worked wonders providing a pitch black background and outstanding silence with neutral tone. 40-40 lapping is what the market called it and it was as soft as silky human hair.

Cheers

Hi gobble, can you ley me know where you source the cable from?

Thanks

 

[sachu888]

Careful with the wires. Teflon is not a magic ingredient - I once got teflon dielectric insulated wires @300/- per mtr for my preamp and it sounded horrible. A 40/- per mtr pvc insulated shielded wire worked wonders providing a pitch black background and outstanding silence with neutral tone. 40-40 lapping is what the market called it and it was as soft as silky human hair.

Cheers

I have used twisted pair of CAT5 Ethernet cable in my DIY CNC phono.It has a good quality copper and very easy to solder.

Regards,
Sachin

 

[omishra]

I have used twisted pair of CAT5 Ethernet cable in my DIY CNC phono.It has a good quality copper and very easy to solder.

Sachin,CAT5 cables are okay for signal wires upto 10-15 cm.

He is talking about internal wires, power cables from PS-amp kit and speaker out jumpers between amp kit and output jacks. There I always used local finolex branded 3sq mm or 5 sqmm multi stranded fireproof cable. For less than 12", I see no issues. I never found any noise or coloration of audio.

Here shops have wire terminals sold by dozens rate. You can find it locally too.

 

[gobble]

Hi gobble, can you ley me know where you source the cable from?

Thanks

SP road, Chetan Cables I think.

HTH

 

[omishra]

SP road, Chetan Cables I think.

HTH

Are you talking about that transparent jacket silver stranded cable? I also bought 4 meter from Chetan Ele. way back in 2006, still using it piece by piece in amp board signal input.

 

[quad]

The "termination clips" are easily available in any scooter/car parts
shops. They are known as horn clips or battery clips.

I have used Cat 5 cable (coloured wires twisted together for positive,
and white wires twisted together for negative) even for the
speaker connections in my MyRef. You can use short lengths
of proper speaker cable, if you wish.
For the power wires, I also used Finolex wires from my local
electrical shop.

 

[jls001]

Careful with the wires. Teflon is not a magic ingredient - I once got teflon dielectric insulated wires @300/- per mtr for my preamp and it sounded horrible. A 40/- per mtr pvc insulated shielded wire worked wonders providing a pitch black background and outstanding silence with neutral tone. 40-40 lapping is what the market called it and it was as soft as silky human hair.

Cheers

I didn't set out specifically to buy teflon sheathed wires but as things turned out, it was the first thing I saw in the store-front display at the first store that I went to, and it looked good. So I asked how much it cost, and if it was available in retail (need to ask that question in Lamington Road as many of them are wholesalers and sell only full bundle or full packet). The seller immediately stripped the wire and showed me the goods inside (turned out to be copper strands plated with silver). So I just bought the two available colours (red and black) @ Rs 35/m for 15 AWG. There were thicker wires but I thought it would be overkill, and colour was limited to either black or red. Later I went to another shop and found the white coloured one (Rs 45/m, same gauge!).

Since I had bought it, let me try them out. If my experience is similar to your's may be I will change it in future.

 

[jls001]

Whats the cost like ?

1800something. Not at all costly, IMO. But I've made two trips to the Dinrack factory and that's adding up to a lot of my time. Hopefully the final product will be to my liking.

 

[jls001]

I have used twisted pair of CAT5 Ethernet cable in my DIY CNC phono.It has a good quality copper and very easy to solder.

Regards,
Sachin

I guess 24 AWG solid copper from CAT5/6 will do well for signal cables.

 

[gobble]

Are you talking about that transparent jacket silver stranded cable? I also bought 4 meter from Chetan Ele. way back in 2006, still using it piece by piece in amp board signal input.

No, it is dull Grey sheath outside with white sheath for the core inside.

cheers

 

[Audiodoc]

Am about to complete my My Ref. Wanted to know what the LED is for and the polarity of the same. Is it supposed to light up continuously or does it determine when the protection circuits are active.

 

[linuxguru]

The LED should light up when the relay is energized, i.e. in normal operation of the speakers. When the relay releases (i.e. speaker protect), the LED should be off.

I don't remember the polarity (the schematic is not with me here) of the LED, but it won't hurt if the LED is reverse polarized for a few seconds. You can also use a multimeter on the terminals to check the polarity.

 

[Audiodoc]

Connected everything but like every DIY project of mine no sound.

Will describe the flow of electrons. Wall socket>IEC with fuse (not blown)> power switch (phase)>toroid 22-0-22 160VA checked with DMM>spade connectors to AC1 AC2 PGND>Output speaker + terminal near LM3886 - terminal near relay.

When I power up nothing happpens when I power down the relay light comes up for a second.

Not understanding what has gone wrong.

 

[linuxguru]

OK, disconnect the speakers, power up and check rail voltages - depends on your trafo, but nominally +/- 32V. Then check the voltages on the opamp rails: +/- 12V. Finally check the output offset voltage between SPKR_OUT and PGND (assuming that the relay did not click on after power up). Check value of R11 (1 ohm) - if it is open (infinity), there is a fault - most probably in the PSU/rectifier circuitry.

I'm assuming that your LM3886TF is from a known good source, and authentic.

 

[Audiodoc]

I have a lot of DC at the output probably thats why the protection circuit has come up as soon as I turn on it is around 24V should be in millivolts.

The DC voltages are OK at the OPamp 24V between pins 4 & & (2X12V). Nothing has smoked. I always use cheapo speakers for testing.

 

[Audiodoc]

Checked again with a better multimeter. Across the speaker terminals the DC voltages are OK 0.05V. Between speaker+ and PGND it is 29V DC in both boards.

The DC voltages are normal across the OPamp.

 

[linuxguru]

I have a lot of DC at the output probably thats why the protection circuit has come up as soon as I turn on it is around 24V should be in millivolts.

OK, it's latching up high - the good news is that your protection circuit is probably working fine.

The bad news is that either the LM3886TF or the LM318 is marginal/bad. Check for solder bridges, shorts, opens etc. near the LM318 as well as the LM3886. Check that the opamp is correctly inserted - pin 1 nearer the PSU caps. Check for pin to PCB pad continuity on all 8 pins.

If all looks fine, swap the opamp from the other monoblock and test again.

 

[linuxguru]

Checked again with a better multimeter. Across the speaker terminals the DC voltages are OK 0.05V. Between speaker+ and PGND it is 29V DC in both boards.

Hmm - speaker output on both boards is latching up high. Maybe identical assembly error on both? Check everything I mentioned in the previous post, and post a pic of the LM3886TF chipamp.

If it's an LM3886T (metal tab), it should be isolated from the heatsink or it will probably get nuked if it shorts to ground.

Check that resistors 470k, 47R and 47k aren't accidentally interchanged.