Group Buy: Mauro Penasa MyRef Rev C kit

[Audiodoc]

Thats what needs to be checked. Though rev E has a forward sound stage there is some harshness (with more measured THD than the Rev C) which on my 6 ohm loads produces screeching sounds at higher volumes. Earlier I thought it to be an assembly issue but after checking different opamps as well as changing a few resistors (the previous ones being fine on measuring after disassembly) I came to the conclusion that the Rev E might be very particular about the impedance of speakers. However this needs to be proven with an 8 ohm drive unit.
In my opinion it is better to stick with rev C till more testing is done.

Although stability increases with a 100pF capacitor at C34 sonics are always better with a lower value of the same as pointed out on DIYA.

 

[gopib]

I have been running my Rev C for some months now. After seeing these posts I ran a check since I have both 8ohms and 6ohms.

With 6ohms: My DC output at the transformer is 25-0-25, I find that the IC as well as the heatsink gets pretty hot after about an hour. I have played it beyond an hour also and did not find any degradation in sonics.

With 8ohms: All conditions similar, I found that the IC and heatsinks were barely warm.

So I guess the output load has a role and it increases dissipation with lower R of
speakers.

 

[quad]

With 8ohms: All conditions similar, I found that the IC and heatsinks were barely warm.

That's my experience too - MyRef Rev C, 8 ohms load, heatsink is
barely warm even after an hour.

 

[hemanth.hg]

I connected the Channel 1 to a different set of speaker which has an impedance of around 7.8 ohms, the result is the same, that is when the volume is increased above 50% on my ipod touch, it makes screeching sound.

What are the other components failure could cause the above issue?

 

[Audiodoc]

Do one thing to check whether the screeching is due to DC. Connect the pods of mm to speaker terminals after disconnected speakers and check if the dc offset increases with increasing volume and by how much. If it doesn't increase above 100mV then the screeching should be some sort of distortion. Check with 310 as well as tlo71.

 

[hemanth.hg]

Yesterday I had been to Siva's place along with both the MyRef boards. He has been very helpful in debugging and fixing the issue. He spent around three hours verifying all the components, connectivity and finally reflowed the soldering(I was just watching, trying to understand the way he does debugging). The reflowing resolved the issues on both the channels. There is a little bit of buzz on one of the channel(but it is very feeble), I think if I reflow it again, it will get resolved.
Today I hooked up the amplifier to my speakers and has been running it for almost 10 hours and the heatsinks are hardly getting hot.

As far as the music is concerned it is sounding very detailed and bass is really good and I think it needs around 50 to 100 hours of burning before I can make any review comments on that.

I'm very thankful to Audiodoc in making me understand the various issues I faced.

 

[Audiodoc]

It's nice to hear that. Dry joints can be really bad. It is always advisable to use a copious amount of flux. Though messy but it helps to remove any oxide formation while soldering and gives nice sparkling joints. Later you can use isopropyl alcohol to clean it off.
Mine also dont get hot and sound good at normal listening levels. It is only when the input signal level / volume is louder do I hear some clipping. Still to get my LF01s working with this though. Will trouble Siva next weekend.

 

[hemanth.hg]

Thanks Syed, even Siva suggested to use Isopropyl alcohol.

The screeching has stopped even at very high volume levels and there is absolutely no screeching at all.

One more thing we did was that we tried both the LM318 and TL071. We found the sound to be very detailed with LM318 than the TL071 (we were able to clearly notice that difference).

 

[naren2512]

Hey Linuxguru and others,

Are these kits still available? and also is the complete amp also available ?

and has anybody tried this kit with speakers that have minimum impedence of 4 ohms ?

Regards,
Naren

 

[linuxguru]

Hey Linuxguru and others,

Are these kits still available? and also is the complete amp also available ?

and has anybody tried this kit with speakers that have minimum impedence of 4 ohms ?

Yes, regarding kits - I just replied to your PM. Complete amps: only prototypes, none for sale.

It will work with 4-ohm speakers if the rail voltages are reduced to +/- 28V or lower. In practice, the trafo needs to be 20-0-20 or 22-0-22 VAC. For even lower voltage trafos, changes are needed to R1, R4 on the boards.

For optimal sonics, stick with 8-ohm speakers and a 24-0-24 VAC trafo.

 

[naren2512]

Friends,

Has anybody tried to compare the my ref stereo amp with Topping TP20 tripath 2020 ? It will be interesting to know how they both compare to each other and what are the differences and which one stands out.

If anyone has been able to listen to both of these then please do share your thoughts/ experiance

Thanks and have a great day ahead

Regards,
Naren

 

[omishra]

I am waiting for my heatsink cabs from Magma. Once I get it my amp will be built. These kits are laying with me from long time since Aug last year IMO. I have TA2022 based amp though not exact TP20 but sonically equal.

 

[naren2512]

That would be awesome I will wait to hear from you about the comparision between the My ref and TP2020 amps.

Also did you procure all the parts other than the my ref kits from Magma only or just the cabinets and heat sinks?

Btw - Magma ( Ali ) is a wonderful guy and at the same time pretty knowledgible.. I had bought speaker stands from them and they were great.

Regards,
Naren

I am waiting for my heatsink cabs from Magma. Once I get it my amp will be built. These kits are laying with me from long time since Aug last year IMO. I have TA2022 based amp though not exact TP20 but sonically equal.

 

[jai1611]

I have TA2022 based amp though not exact TP20 but sonically equal.

I have owned both TA2020 and TA2022 amps in the past. IMHO, they are tonally very different.

 

[omishra]

I have owned both TA2020 and TA2022 amps in the past. IMHO, they are tonally very different.

Actually I was referring this where all knowledgeable people put there summary. And on this page it mentions 25 Microchips That Shook the World - IEEE Spectrum which includes TA2020 over which TP20 based.

 

[omishra]

That would be awesome I will wait to hear from you about the comparision between the My ref and TP2020 amps.

Also did you procure all the parts other than the my ref kits from Magma only or just the cabinets and heat sinks?

Btw - Magma ( Ali ) is a wonderful guy and at the same time pretty knowledgible.. I had bought speaker stands from them and they were great.

Regards,
Naren

I have everything except cabinet. I bought kit from linuxguru, toroidal from miracle, banana post & RCA sockets online. I have all sundry screw spacers handy, now waiting for chassis only.

 

[jai1611]

Actually I was referring this where all knowledgeable people put there summary. And on this page it mentions 25 Microchips That Shook the World - IEEE Spectrum which includes TA2020 over which TP20 based.

Sorry, I did not get your point.

I thought you were responding to the query about comparison to a Topping amp, hence replied and pointed out that in my view the two Tripath chips (TA2020 and TA2022) sound quite different.

 

[omishra]

Sorry, I did not get your point.

I thought you were responding to the query about comparison to a Topping amp, hence replied and pointed out that in my view the two Tripath chips (TA2020 and TA2022) sound quite different.

The first link I was pointing out, mentions both are same, only wattage differ. That means THD, noise differ at different level of power rating.

 

[Audiodoc]

My myref sounds pretty good when compared to the other amps I have heard. Unfortunately my speakers have 4 to 6 ohms impedance while my myref has a power supply tailored for an 8 ohm load so have to play at normal listening levels. Have heard a t amp a few years back so can't compare.

 

[jai1611]

The first link I was pointing out, mentions both are same, only wattage differ. That means THD, noise differ at different level of power rating.

I suspect their damping factors also differ, which leads to a difference in tonality with some speakers.