MyRef rev C build

[har297]

Hi All,

After a long wait i was able to lay my hands on Linuxguru's MyRef Ver C Kits,Thanks Siva for the wonderful kits.

Also thanks to FM Goldyrathore who was willing to let go of a pair.

Pics to follow...

Parts List.
Things already procured
1. MyRef Rev C, 2 Monoblocks- Basic BOM
2. Toroidal Transformer 24-0-24 8A

Things pending.
1. Volume control Pot/Stepped attenuator
2. RCA sockets, speaker binding posts.
3. Cabinet

Need suggestions on the below..
1. What wires to use for wiring internally ? 1sq mm Finolex will be ok for power and Speaker cables ?
2. CAT 5E cables for signal cables?


Regards
Harsha

 

[linuxguru]

Need suggestions on the below..
1. What wires to use for wiring internally ? 1sq mm Finolex will be ok for power and Speaker cables ?
2. CAT 5E cables for signal cables?

1. Should be OK. For the speaker cables, you can consider Chetan 168/40 or similar OFC speaker cable (you can use a small section of the outside cable for the board to binding-post section also).

2. CAT 5E will work, but it's difficult to connect their foil shields. There are several kinds of shielded cables available which are easier to use, including some Microphone cables from vendors like Belden, Mogami, etc. I also found a good dual-wire (red and white) teflon-insulated OFC-shielded microphone cable from a company called Srexact, which is soft and flexible, and should work well also. It's only about Rs.20/metre.

When using dual-core cable, one possible connection arrangement is this:

1) Connect one core from signal ground at the board input connector block to the *isolated* RCA signal ground. It should not connect to Chassis ground.

2) Connect the second core from signal input to the RCA centre contact.

3) Connect the shield to the *chassis* ground near the RCA sockets, not the signal ground. Leave it unconnected at the other end near the boards, and trim it a little so that it doesn't touch the signal ground.

Repeat for the other channel also.

Related stuff: For C1, C2 several choices are possible now which are better than the Panasonic FCs I provided with the original standard kit - It's worth using Panasonic FM/FR, Elna RE2/RJH/RJJ/RJB or Rubycon ZL/ZLH/ZLG if available.

For C6, C11: Panasonic FM is better than Panasonic FC supplied then.

For C9, Nichicon UD is an excellent option with good sonics.

There are also several premium electrolytics (Silmic II, Cerafine, Muse FG/KG/KZ, Black Gates, etc.) usable at most of these locations.

 

[har297]

Thanks Siva for the suggestions..
I will try to get the Shielded cables for the Signal cables this weekend.

Any suggestions on Speaker Binding posts, and RCA sockets ? last time when i visited MX shop in SP road they only had full metal ones, (the type we push and insert the cable)
i would need the red/black insulated ones.

Here is the current test setup pic.

 

[linuxguru]

... Any suggestions on Speaker Binding posts, and RCA sockets ? last time when i visited MX shop in SP road they only had full metal ones, (the type we push and insert the cable)
i would need the red/black insulated ones.

I would suggest the ones used in the instrumentation and lab power supply industry with screw-down knobs, which are available at reasonable prices - the 30A-rated ones are Rs.20 or lower. The only downside is that the screw shaft is relatively narrow and the perpendicular hole for inserting the wire is too narrow for normal speaker-cable wires. However, it's not a show-stopper - you can still wind the wire around the shaft and tighten the knob down in the usual way.

For RCAs, the good ones are all imported and scarce. Cable Fort in Chennai has some gold-plated ones claimed to be Neutrik. I found some sockets sold by EBay vendors in China to be better and heavier-duty at almost the same price.

 

[quad]

MX does have binding posts.
If you can't find them, you could buy a
speaker connector cup (like MX No : 3352) and remove
the binding posts from it.

MX MDR ELECTRONICS & MX ELECTRONICS & HDMI & CCTV CAMERA & DVR & SDI ACCESSORIES & VGA ; DVI & APPLE ACCESSORIES & CABLES & CONNECTORS & HOME THEATER CABLES & PRO-AUDIO / STUDIO ACCESSORIES & FIBER OPTICS & CABLE MANAGEMENT & CABLE ORGANISER & VIDEO
MX MDR ELECTRONICS & MX ELECTRONICS & HDMI & CCTV CAMERA & DVR & SDI ACCESSORIES & VGA ; DVI & APPLE ACCESSORIES & CABLES & CONNECTORS & HOME THEATER CABLES & PRO-AUDIO / STUDIO ACCESSORIES & FIBER OPTICS & CABLE MANAGEMENT & CABLE ORGANISER & VIDEO

I am sure diyaudiocart will have suitable ones -

Connectors / Terminals

If you can only find the non-insulated type, then you have to cut a
bigger hole in your chassis, and mount a piece of switchboard bakelite
or bare PCB or 6 mm MDF, drill holes and mount the binding posts to that.
Or fix the whole round speaker connector cup.

 

[har297]

@Siva,

I measured the AC voltage out of the toroid, it was 25.6 V AC.

Will it be a problem ? Should i plan on changing the transformer or are there any alternatives ? Please suggest..


Regards
Harsha

 

[linuxguru]

@Siva,

I measured the AC voltage out of the toroid, it was 25.6 V AC.

Will it be a problem ? Should i plan on changing the transformer or are there any alternatives ? Please suggest..

It's OK, it will work - but you need to use only 8-ohm speaker loads, nothing lower or it will heat up and/or activate SPiKe protection. Also check (by touch) the heatsinks after about an hour of listening at normal volume - if it is too hot to touch, you'll have to upsize the heatsinks. Warm to moderately hot is OK.

 

[har297]

It's OK, it will work - but you need to use only 8-ohm speaker loads, nothing lower or it will heat up and/or activate SPiKe protection. Also check (by touch) the heatsinks after about an hour of listening at normal volume - if it is too hot to touch, you'll have to upsize the heatsinks. Warm to moderately hot is OK.

Thanks Siva,

I tried playing MyRef for a couple of hours in moderate to high volume with the load as Philips Hi-Q 8" drivers, with the measured DC resistance of 7.15 Ohms, and according to the spec sheet they are 8 Ohms.

The heat sinks were not too hot, and the Spike was not triggered even once during that window. But R1 and R4 were becoming hot, and i think it is normal.


Regards
Harsha

 

[tnvijay]

@Harsha.
Hi, I too have a similar combo. Philips hi q with miniref 1875. Have been using it for a couple of months. Can you share your review on the sonic quality of the myref?

Also, what is your cabinet plan for philips hi q. You use it as a crossoverless single full ranger Or a tweeter is there in addition?

 

[har297]

@Harsha.
Hi, I too have a similar combo. Philips hi q with miniref 1875. Have been using it for a couple of months. Can you share your review on the sonic quality of the myref?

Also, what is your cabinet plan for philips hi q. You use it as a crossoverless single full ranger Or a tweeter is there in addition?

Hi,

The current enclosure is around 30 Lts ported, originally i was using a second order passive crossover with crossover frequency of 4Khz, The high frequencies were handled by a Philips Silkdome tweeter.

For current testing with MyRef, i am only using the Hi-Q as a full ranger without any crossover. I might not be right person for seeking review, but for my taste i feel the combo of MyRef + Hi-Q seems to be too bright.But i was surprized about the Low frequency delivery of the combo in a few tracks. I will wait for some more time for the Burn in...

Thanks
Harsha

 

[linuxguru]

The current enclosure is around 30 Lts ported, originally i was using a second order passive crossover with crossover frequency of 4Khz, The high frequencies were handled by a Philips Silkdome tweeter.

For current testing with MyRef, i am only using the Hi-Q as a full ranger without any crossover. I might not be right person for seeking review, but for my taste i feel the combo of MyRef + Hi-Q seems to be too bright.But i was surprized about the Low frequency delivery of the combo in a few tracks. I will wait for some more time for the Burn in...

That Philips silk-dome tweeter is unobtainium now, I believe, though there are alternatives including Dainty and some Chinese ones.

That upper-mid brightness is a common feature in most of the earlier MyRef builds with Panasonic FC at various locations. It can be tamed by substituting other electrolytics at various locations, as mentioned earlier in the thread. Resistors R7, R10, R12 and R13 are also important - use the highest quality non-magnetic ones that you can find. Finally, film/foil caps like Wima FKP2 or ERO KP1830 will help at some locations. Check out the build threads at the chipamps forum of diyaudio.com for details and suggestions. Sonics can also be made a bit less edgy (smoother), by using my LF01 or LF07 hybrid/discrete Class-A opamp module - however, the impact is more audible on the premium build or after upgrading some passives. At the minimum, replace the Panasonic resistors at R7 and R10 with Dale, PRP or similar non-magnetic resistors - the boutique ones like Vishay Z-foil and Caddock MK132 are unobtainium locally, and in some cases can make the brightness worse. Takman REY25 and Holco H4 are also good choices.

Stability and temperature seem to be fine, so your trafo choice and the build itself are functioning perfectly.

 

[har297]

That Philips silk-dome tweeter is unobtainium now, I believe, though there are alternatives including Dainty and some Chinese ones.

That upper-mid brightness is a common feature in most of the earlier MyRef builds with Panasonic FC at various locations. It can be tamed by substituting other electrolytics at various locations, as mentioned earlier in the thread. Resistors R7, R10, R12 and R13 are also important - use the highest quality non-magnetic ones that you can find. Finally, film/foil caps like Wima FKP2 or ERO KP1830 will help at some locations. Check out the build threads at the chipamps forum of diyaudio.com for details and suggestions. Sonics can also be made a bit less edgy (smoother), by using my LF01 or LF07 hybrid/discrete Class-A opamp module - however, the impact is more audible on the premium build or after upgrading some passives. At the minimum, replace the Panasonic resistors at R7 and R10 with Dale, PRP or similar non-magnetic resistors - the boutique ones like Vishay Z-foil and Caddock MK132 are unobtainium locally, and in some cases can make the brightness worse. Takman REY25 and Holco H4 are also good choices.

Stability and temperature seem to be fine, so your trafo choice and the build itself are functioning perfectly.

Thanks Siva,

Yes, i do plan on upgrades mainly to reduce the Brightness in the High frequencies.
But i feel i will not be able to exploit the true potential of MyRef + LF01 combo. Because my current source is PC with Foobar. Speakers are Philips 8" Hi-Q full rangers.

I think upgrade of Source as well as speakers are essential here....:sad:

And is any soft start necessary for Toroid ? the toroid is rated at 24-0-24 VAC @ 8Amps.


Regards
Harsha

 

[quad]

You can use a NTC thermistor in the primary of your toroid.

Transformer Inrush Current Protection | Ametherm

http://www.amphenol-sensors.com/images/stories/temperature/ntc-inrush-1.jpg