Group Buy: Mauro Penasa MyRef Rev C kit

[dances_with_wolves]

hi Siva,

I am an electronics engineer living in Bangalore. If you need any help with testing, I may be able to help out on weekends. I have a Marantz PM 7001 amp, and don't plan to buy this one right now though.

Like another member, I would be interested in a good DAC group buy though.

regds,
dww

 

[captrajesh]

:yahoo:Hi guys,

I take the honour to be the first HFV member (after Shiva and his parents) to listen to his prototype.

I'm too happy:cheers: right now to write a review. Hope you guys understand.

Will post my impressions tomorrow.

Suspense to continue.hyeah:

Rajesh

 

[madvenu]

Hello LinuxGuru

Hope I can still place a request ?

I'll take one pair of monoblock kits. How do I make the payments ?

Thanks.

 

[linuxguru]

Captain, thanks for your kind hospitality and indulgence in allowing me to consume the greater part of your quality holiday time yesterday - for me, just listening to Santana on your Kenwood drivers in Viren Bakshi's cabinets was a huge revelation.

GB updates: There is no deadline now for the entering the Group Buy - actually, it hasn't formally begun yet. DIYers are welcome to post a follow-up expressing their interest to join the Group Buy.

I have received the version 1.3 PCBs, and I will populate and test a pair of them within a few days. I'll send out PMs for the contact details of all interested Group Buyers as soon as that validation concludes.

 

[madvenu]

...

I have received the version 1.3 PCBs, and I will populate and test a pair of them within a few days. I'll send out PMs for the contact details of all interested Group Buyers as soon as that validation concludes.

Linuxguru

I am in Bangalore - can I meet up with you and take part in this activity ?

Venu

 

[captrajesh]

Hi guys,

Day before yesterday, a got a PM from Shiva (linuxguru) inviting me over to his parents' place (in Chennai) to listen to his prototype along with my AP bookshelfs. I jumped at the idea and called him immediately.

I suggested that I have tower speakers in addition to the bookshelfs which he might like to listen and suggested that he bring his amp over instead as carrying the towers & bookshelfs is quite an effort.

Since his car battery was down, I offered to pick him up.

Yesterday morning I got a call from him that he is ready. Got ready in a jiffy and was at his place by appointed time.

We drove to my home and I started the proceedings by showing him my setup consisting of Marantz CD 6003, Class D Amp CDA 254 from Class D Audio, which was connected to AP Bookshelfs.

After playing a few tracks, we decided to connect his amp with the same source and speakers but the said speakers were having two pairs of cables per speaker; one connecting to the woofer directly and one to the tweeter through the x-over. I was hesitant to remove all those connections and hence offered him to hook up his amp to my Towers having kenwood drivers.

His amp was housed inside a beautifully lacquered wooden cabinet which I'm told was some old german amp of which, he has removed the amplifier circuit but retained the Tone controls. It had individual volume controls for both channels.

When compared to the sound of my Class D amp, the sound is quite different.
Class D sound was more tube like with lush sounding mids especially the guitars, the sax / trumpets and

 

[captrajesh]

Hi guys,

Day before yesterday, a got a PM from Shiva (linuxguru) inviting me over to his parents' place (in Chennai) to listen to his prototype along with my AP bookshelfs. I jumped at the idea and called him immediately.

I suggested that I have tower speakers in addition to the bookshelfs which he might like to listen and suggested that he bring his amp over instead as carrying the towers & bookshelfs is quite an effort.

Since his car battery was down, I offered to pick him up.

Yesterday morning I got a call from him that he is ready. Got ready in a jiffy and was at his place by appointed time.

We drove to my home and I started the proceedings by showing him my setup consisting of Marantz CD 6003, Class D Amp CDA 254 from Class D Audio, which was connected to AP Bookshelfs.

After playing a few tracks, we decided to connect his amp with the same source and speakers but the said speakers were having two pairs of cables per speaker; one connecting to the woofer directly and one to the tweeter through the x-over. I was hesitant to remove all those connections and hence offered him to hook up his amp to my Towers having kenwood drivers.

His amp was housed inside a beautifully lacquered wooden cabinet which I'm told was some old german amp of which, he has removed the amplifier circuit but retained the Tone controls. It had individual volume controls for both channels.

When compared to the sound of my Class D amp, the sound is quite different.
Class D sound is more tube like with lush sounding mids especially the guitars, the sax / trumpets and percussion instruments that really stand out, whereas, the overall sound is quite warm and detailed.

Having said that, the amp does not mask the deficiencies of recording, which we have noticed on a particular track of Led Zeppelin. It sounds like an expensive amplifier, take a walk marantzs, nads and the likes. It beats them by miles.

I'm told that the tone controls need to be worked on as they are from an amp of 50s vintage.

I wanted Shiva to listen to my AP Bookshelfs so pulled out all the cables and hooked it up to his prototype.

We have noticed the differences instantly. Bass extension was not that deep (unfair comparison and understandable) but the mids were much more lush and vocals had more body on the Towers.

Guys, trust me, for 5k, you will be laying your hands on a very special amplifier. A commercial amp with equivalent SQ will definitely cost you at least 5 times if not more.

I'm going for this. PERIOD.

 

[denom]

Thanks for the brief review capn. Did you play any rock tracks??? How will the amp sound for rock/metal music??? Judging by your review, I'm sure the amp will have no issues handling this genre of music as well.... Also, did Siva share any info on the tranny used (type/ratings etc..)??? Did you take any pics?

Cannot wait to get my hands on one now

Siva,
Thanks for letting Capn. have a listen.
Hope we can make some swift progress now with all the allied components to go with the amp.

Regards

 

[captrajesh]

Thanks for the brief review capn. Did you play any rock tracks??? How will the amp sound for rock/metal music??? Judging by your review, I'm sure the amp will have no issues handling this genre of music as well.... Also, did Siva share any info on the tranny used (type/ratings etc..)??? Did you take any pics?

Cannot wait to get my hands on one now

Hi Denom,

Sorry, forgot to add. We have not had much time for extended listening. We listened to a few tracks of Santana (Best of Santana), Led Zeppelin (Dont know the tracks), Pink Floyd - (Hey You) and Eagles Hell Freezes over (Hotel California)

I'm told by Shiva that the Trafo is less than optimum 100VA. He said the Amp would really sing and dynamics would improve greatly if a 200 VA Trafo is used. Anything more is an overkill he said.

Rgds


Rajesh

 

[linuxguru]

His amp was housed inside a beautifully lacquered wooden cabinet which I'm told was some old german amp of which, he has removed the amplifier circuit but retained the Tone controls. It had individual volume controls for both channels.
...
I'm told that the tone controls need to be worked on as they are from an amp of 50s vintage.

Thanks, Captain. It's a mid-1970s Germanium-based local model actually, the Bevox BE5500. I gutted the power amp section and replaced it with two MyRef monoblocks. I also bypassed the input selector and preamp sections. The volume controls and Baxendall tone controls are retained, which have some Mylar/polyester caps which I need to replace with a bit more premium caps, but it does not hurt the sonics too much.

We have noticed the differences instantly. Bass extension was not that deep (unfair comparison and understandable) but the mids were much more lush and vocals had more body on the Towers.

Yup, no comparison between the AP-101s and the Kenwood towers. The vocals on the AP-101s are somewhat flat, one-dimensional and disconnected. The Kenwoods, by contrast, are fuller, deeper and coherent on the vocals. The soundstage on the Kenwoods is almost like a concert hall - wide and deep.

The matching between the MyRefs and the Kenwoods is almost magical - even with a seemingly puny 100VA transformer for both channels of the MyRef. I would suggest that a 200VA - 240VA trafo would be more than adequate for just about any genre of music, and any reasonable speaker load on the MyRef.

 

[captrajesh]

The matching between the MyRefs and the Kenwoods is almost magical - even with a seemingly puny 100VA transformer for both channels of the MyRef. I would suggest that a 200VA - 240VA trafo would be more than adequate for just about any genre of music, and any reasonable speaker load on the MyRef.

Hi Shiva,

They shine irrespective of what I throw at them.

I'm not sure of the load of my towers or for that matter any other characteristics. I'm now curious and want to derive all the parameters. How do I go about?

 

[linuxguru]

.
His amp was housed inside a beautifully lacquered wooden cabinet ...

OK, here are the pics of the MyRef installed inside the Bevox cabinet - it's a bit of a kludge, but works surprisingly well within its limitations (the chassis is the heatsink, the transformer is puny, and the 30+ year old pots are noisy and scratchy).

This is exactly the same amp that was auditioned by Capt. Rajesh on his Kenwoods as well as Acoustic Portrait 101s.

If anybody has any pointer(s) to cabinet builder(s) who can build similar lacquered wooden amplifier cabinets at Bangalore or Chennai, please post or PM me.

 

[linuxguru]

Here is a pic of the Version 1.3 PCB (the PCB that will be provided in the kit) with most of the components installed (the filter caps haven't been installed yet). The kit is very similar, though some of the passives may differ in value, brand or colour depending on availability. This board has not yet been powered up and tested, which will happen today or tomorrow if all goes well on the assembly.

Some notes:

1) All parts fit exactly with plenty of space in the drilled pads. There's no need to force anything in, which was a problem in the Version 1.2 Twisted Pear boards, where even the LM3886TF chipamp had to be forced in.

2) There is ample space for physically larger components at many locations, including C1, C2, C3, C8, C9, R7 and many others.

3) Locally available lug/tag/fast-on connectors fit exactly in the metric-sized drill locations - again a problem in Version 1.2.

4) Many component locations allow the use of alternate lead pitch components, allowing more flexibility in component sourcing.

5) 35mm diameter caps can be used at C3 and C8, and these include many premium and high-capacitance options, like the 18,000 or 22,000uF/50V Panasonic TS-UP.

6) Individual discrete rectifiers can be used instead of the bridge rectifier shown - the layout allows both options.

7) The red box-type film caps are Wima MKP/MKS. The blue box-type caps are Evox/Rifa or Pilkor (Philips) polypropylene caps. All electrolytics are Panasonic, Elna or Nippon-Chemicon. All the 0.25W metal-film resistors are Watts brand or similar, with non-magnetic leads.

8) The feedback resistor is a Mitsubishi-branded KOA-Speer 2W metal-film, which IMHO is a higher quality option than the resistor provided in the DIYaudio Ultimate BoM. Two of the small caps are Silver Mica, better than the Ultimate BoM. The rectifiers for the protection circuit are fast-soft BYV95C, better than the 1N4001s in the Ultimate BoM.

9) The protection relay is a Goodsky (instead of Omron on the Ultimate BoM), along with a few small modifications to the protection circuit. The modified circuit turns on more reliably than the Ultimate BoM circuit, even with variations in component values.

10) A premium input-coupling cap like a Solen, Mundorf, Obbligato or similar can be used off-board instead of, or as a bypass to, the blue box-type Pilkor X2 shown in the picture.

11) Some component locations will not be populated and the corresponding parts will be omitted in the kit.

12) The safety-ground lug is not populated in this board, but will be included in the kit.

I'll post other addenda or alterations later.

 

[jatinsoni200654]

Hi linuxguru,
can we connect it directly to PC or we need a DAC.

 

[linuxguru]

can we connect it directly to PC or we need a DAC.

You can connect it directly to the analog sound output (either line or headphone out) of a PC, but you will need a premium sound card (like a Creative Audigy 2 or one of the Auzentech cards) to get the full benefit of the sonics of the MyRef. The best match will be an Auzentech with the front-channel op-amps rolled with LME49720 or 49722, or an Audigy 2 with a similar op-amp mod.

 

[gobble]

So where can we get Solen, Mundorf, Obbligato etc ... for those with itchy fingers ... :licklips:

I dont think the local vegetable vendor by the roadside will have it ...

it will be good to swap after a few months and note the effect caps have ...

What are the ratings for the caps we need to look out for?

Regards

 

[linuxguru]

So where can we get Solen, Mundorf, Obbligato etc ... for those with itchy fingers ... What are the ratings for the caps we need to look out for?

For the moment, the only sources would be EBay (US), various online component outlets like Farnell, Digikey, etc. and specialist audio suppliers like Parts Connexion, Apex Jr., Madisound, HiFi Collective, etc.

Materials: Polypropylene, Teflon, Paper-Oil or Polycarbonate. Values: 0.47uF to 4.7uF, depending on what kind of low-frequency response you're looking for. Voltages from 100V to 630V (the higher voltage caps will be more linear, but also bulkier and more expensive).

 

[Hiten]

Thanks Linuxguru

5) 35mm diameter caps can be used at C3 and C8, and these include many premium and high-capacitance options, like the 18,000 or 22,000uF/50V Panasonic TS-UP.

Are these caps included in the kit or one has to buy them.

11) Some component locations will not be populated and the corresponding parts will be omitted in the kit.

You mean they are not necessary. Right ? Less parts the better. I like minimalist approach. Will save solder time also.
Regards

 

[linuxguru]

Are these caps included in the kit or one has to buy them.
...
You mean they are not necessary. Right ?

The two filter caps C3 and C8 are Panasonic 6800uF in the kit, and these are exactly what were used in the unit auditioned by Capt. Rajesh last week. However, those DIYers who want to change this can source larger or better caps at their own expense, and the PCB layout supports the use of 35mm diameter caps. In Chennai, Nippon Chemi-con 12,000uF/71V caps are available at Suraj Radio. In Bangalore, various large electrolytics are available from Arihant, Chetan and Advanced Micro Components, all at or near S.P.Road. The prices of these caps generally run in the range of Rs.100 to Rs.200 each, depending on the brand, value and quantity.

The parts that are omitted are either redundant/unnecessary and/or were omitted in the earlier Ultimate BoM group buy at diyAudio also. These are mostly bypass caps (3).

 

[stereorules]

I'm a relatively newbie..So pl excuse me for what I'm asking.
What will the difference be between the Panasonic 6800uF in the kit and premium high-capacitance options, like the 18,000 or 22,000uF/50V Panasonic TS-UP ?