Hi Billabong:
I completelly agree with all your comments
I didn't mention them before not to sound pedantic...
It's nice to see we can discuss these topics.
I used to have a Mosfet Class A pair of monoblocks that sounded its best after several hours. I couldn't maintain permanent power-on because of heat and fear of failure plus $$ on electric bill
Appart that, hookup wire can have a big influence in sound: I used Kookaburra as stand alone preamp before I connected to My-ref. I found it sounded very detailed and clean but I missed some colour/warmth on midrange. I am using OCC copper (Ohno continious cast copper wire) 3 strands of solid 24AWG wire, braided, per each lead (+ and return). Actually I made 1 meter interconnects attached to Kooka's PCB. When I built the integrated amp (still untested) I cut these IC's (+/-75cm) and used them on my other system: I did find the same sonic presentation, very clean and detailed but lacking warmth!
When I power-on My-ref, hopefully tomorrow, I will try not to be influenced by this experience.
Best regards.
M
I completelly agree with all your comments
I didn't mention them before not to sound pedantic...
It's nice to see we can discuss these topics.
I used to have a Mosfet Class A pair of monoblocks that sounded its best after several hours. I couldn't maintain permanent power-on because of heat and fear of failure plus $$ on electric bill
Appart that, hookup wire can have a big influence in sound: I used Kookaburra as stand alone preamp before I connected to My-ref. I found it sounded very detailed and clean but I missed some colour/warmth on midrange. I am using OCC copper (Ohno continious cast copper wire) 3 strands of solid 24AWG wire, braided, per each lead (+ and return). Actually I made 1 meter interconnects attached to Kooka's PCB. When I built the integrated amp (still untested) I cut these IC's (+/-75cm) and used them on my other system: I did find the same sonic presentation, very clean and detailed but lacking warmth!
When I power-on My-ref, hopefully tomorrow, I will try not to be influenced by this experience.
Best regards.
M
Hi maxlorenz,
Re. warming up:
Warm up time seems to vary for different components. I have a ss preamp that is intended to be left powered up. I have found that it just needs an overnight warmup if it has been unused for an extended period. After that I power it up for at least a half hour before each use. My valve amps and valve preamps also get at least a half hour warmup before listening. After that routine I find that after about the second or third record the sound improves, sometimes quite dramatically.
I hope you enjoy your new My ref as much as I have mine. You can expect the sound to improve over the first 40-60 hours. I burnt mine in with Dummy loads for 40 hours. The next time it will be 60 hours.
Re. colour/warmth;
coupling caps can impose their signature on the sound. You might try a different output coupling cap on the Kooka. If you are going to use the Kooka with your new My Ref, I suppose you will omit the input cap. I will do the same on my next amp.
I recently changed to Auricap coupling caps on the valve preamp I use with the My Ref and am happy with them. They took about 30 hours to run in.
My Rev C sounds a lot like a modern valve amp. It has colour, warmth and body. At times I think it may have a touch too much midrange warmth and body. I expect my next Rev C will sound different without input coupling caps, and discrete schottky rectify diodes.
Regards,
Audie.
Re. warming up:
Warm up time seems to vary for different components. I have a ss preamp that is intended to be left powered up. I have found that it just needs an overnight warmup if it has been unused for an extended period. After that I power it up for at least a half hour before each use. My valve amps and valve preamps also get at least a half hour warmup before listening. After that routine I find that after about the second or third record the sound improves, sometimes quite dramatically.
I hope you enjoy your new My ref as much as I have mine. You can expect the sound to improve over the first 40-60 hours. I burnt mine in with Dummy loads for 40 hours. The next time it will be 60 hours.
Re. colour/warmth;
coupling caps can impose their signature on the sound. You might try a different output coupling cap on the Kooka. If you are going to use the Kooka with your new My Ref, I suppose you will omit the input cap. I will do the same on my next amp.
I recently changed to Auricap coupling caps on the valve preamp I use with the My Ref and am happy with them. They took about 30 hours to run in.
My Rev C sounds a lot like a modern valve amp. It has colour, warmth and body. At times I think it may have a touch too much midrange warmth and body. I expect my next Rev C will sound different without input coupling caps, and discrete schottky rectify diodes.
Regards,
Audie.
Another RevC born
Dear Mauro, Rudi, Russ and all other diyaudio members,
Thanks for your wonderful contribution! I finished the amplifier today and it still sits on my testboard but a new chassis is already waiting for him:
I used Rudi's PCB design but modified it a little for me since I had the big B250 rectifiers in my drawer:
http://www.diyaudio.com/forums/showthread.php?postid=738877#post738877
I didn't use any esotheric parts, just standard 1% metallfilm resistors and caps from my supplier (film caps are wima though). The input cap is a plain Teapo MPP, but it sounds very nice. The amp worked from the first time I powered it up which made me very happy
There is no hum at all (I cared about a central star ground as you can see on the pic).
The sound is just great!!!!!!!!!! First I recognized compared to my basic nigc gainclone is that it has by far more bass, well who wonders with this filtering
I agree with the statement above, the sound tends to be warm. I rather have untrained amateur ears (don't have audiophile experience) and from that standpoint I can say this amplifier sounds the best what I heard until now which is not much to be honest but at least I heard my own basic NIGC, a Cambridge 640a and my Denon AVR-1803. This amp beats them all. It sounds MUCH better and MUCH stronger and detailed than my stock Denon AVR-1803 receiver. The difference between these amps is gigantic, EVEN my wife recognized a much more improved sound
As you can see the other PCB is already waiting and nearly filled, this amp will drive my home theater. I will reuse my AVR-1803 receiver by buffering the inner signals and feeding them directly to the RevC.
Now the next step is to play with something discrete, I will try the symasym and compare these two amps. Unfortunately I don't have a scope (yet) so I am a little afraid of building something discrete, but I will give it a try.
But for now there will be a long listening sunday session
Best regards and THANKS,
Serge
Dear Mauro, Rudi, Russ and all other diyaudio members,
Thanks for your wonderful contribution! I finished the amplifier today and it still sits on my testboard but a new chassis is already waiting for him:
An externally hosted image should be here but it was not working when we last tested it.
I used Rudi's PCB design but modified it a little for me since I had the big B250 rectifiers in my drawer:
http://www.diyaudio.com/forums/showthread.php?postid=738877#post738877
I didn't use any esotheric parts, just standard 1% metallfilm resistors and caps from my supplier (film caps are wima though). The input cap is a plain Teapo MPP, but it sounds very nice. The amp worked from the first time I powered it up which made me very happy
There is no hum at all (I cared about a central star ground as you can see on the pic).The sound is just great!!!!!!!!!! First I recognized compared to my basic nigc gainclone is that it has by far more bass, well who wonders with this filtering
I agree with the statement above, the sound tends to be warm. I rather have untrained amateur ears (don't have audiophile experience) and from that standpoint I can say this amplifier sounds the best what I heard until now which is not much to be honest but at least I heard my own basic NIGC, a Cambridge 640a and my Denon AVR-1803. This amp beats them all. It sounds MUCH better and MUCH stronger and detailed than my stock Denon AVR-1803 receiver. The difference between these amps is gigantic, EVEN my wife recognized a much more improved sound
As you can see the other PCB is already waiting and nearly filled, this amp will drive my home theater. I will reuse my AVR-1803 receiver by buffering the inner signals and feeding them directly to the RevC.
Now the next step is to play with something discrete, I will try the symasym and compare these two amps. Unfortunately I don't have a scope (yet) so I am a little afraid of building something discrete, but I will give it a try.
But for now there will be a long listening sunday session
Best regards and THANKS,
Serge
Russ,
I was considering going to 18V zeners and class A bias for the LM318, for my second Rev C. Rudi and Dr H were enthusiastic about it, as were you after you tried it.
I noticed that later at page 151 you mentioned that you went back to 12V zeners and 35V rails.
Would you mind letting me in on your reason for your return to 12V zeners?
Did you also abandon the use of class A (7ma) bias for the LM318, and the reason for it?
I would parallel R1 and R4 with resistors to maintain the standard amps supply ma headroom.
serqiusz,
Glad you are enjoying your amp. I think you will find the amp will improve for the next 60 hours and beyond, as others and myself have found. One thing for sure - you won't be bored!
Regards,
Audie.
I was considering going to 18V zeners and class A bias for the LM318, for my second Rev C. Rudi and Dr H were enthusiastic about it, as were you after you tried it.
I noticed that later at page 151 you mentioned that you went back to 12V zeners and 35V rails.
Would you mind letting me in on your reason for your return to 12V zeners?
Did you also abandon the use of class A (7ma) bias for the LM318, and the reason for it?
I would parallel R1 and R4 with resistors to maintain the standard amps supply ma headroom.
serqiusz,
Glad you are enjoying your amp. I think you will find the amp will improve for the next 60 hours and beyond, as others and myself have found. One thing for sure - you won't be bored!
Regards,
Audie.
billabong said:
Hi Audie,
One of the cool things about building lots of these things is you have plenty of opportunity for A/B tests, and having a cooperative wife who can help swap cables for blind A/B tests is also helpful.
The reason for all of the changes back were that they simply sounded better to me that way.
Now, biasing the LM318 for some reason seemed to add a lot of distortion. Even at low currents like 3-4ma. At first I thout it sounded cool, but quickly missed the old setup.
The Shunt reg voltage is largely a question of current. If you don't mind wasting a bit more current through the shunt then higher values for the zeners will work. Also just make sure you have a large enough drop accross the zener to get good regulation.
Give it a go, you may like it better you may not. But it will be fun to test. I can tell you it is a fairly safe change to make so long as you calcualte the resistors for the voltage drop and keep the current available equivalent to what it was.
I would definitely not bother with biasing the LM318 class A. I think because of this circuits particular feedback technique it had a very negative effect.
Cheers!
Russ
KOHTOPA said:Solid state MyRev in my solid state media PC
Hey man that is very very cool.
I looks like there is a trafo in the metal box just behind the LCD. It is well hidden.
Very celever.
How does it work? Sound OK? No issues we all those digital signals and such?
Thanks for sharing!
Cheers!
Russ
Thank you guys!
> Do you use a switched power supply?
> If yes, what voltage do you use?
Yes I do, but only for computer and monitor. Both of them are 12V.
See two connectors on the right side (new attachment). Analog
part has a dedicated power. First I used just one 12V brick for
computer and monitor but power was so noisy that I "saw" 60Hz
on the screen Even now when I use separate power supply (with
separate ground) for monitor it's noisy because power wires go
through the whole box. I should use shielded twisted pair.
Hopefully that should help.
> I looks like there is a trafo in the metal box just behind the LCD.
> It is well hidden.
To be honest, I borrowed that idea here:
http://users.podolsk.ru/boga/DAC.html
The box becomes a little bit warm. Probably I have to drill some holes on the top
> How does it work? Sound OK? No issues we all those digital
> signals and such?
This is still work-in-progress. Right now I can get audio output
only from the computer's LineOut, which is not a good source just
because it has a common ground with computer and it has some
kind of internal amplification already. That's why it's hard to
estimate RevC - garbage in-garbage out
Right now I'm trying to design a unit which will be a combination
of USB DAC and preamp for volume control (remote). Preamp will
be almost the same as your Kookaburra just without output
buffer because it will go directly to RevC. That empty perforated
cage in the middle is intended for that device.
Noise is the main problem in this design. That's why I've
isolate computer and audio grounds. They don't have common
power supplies and audio will be supplied through USB which is
digital differential signal and that's why noise should not come
through this way. I also won't use USB power from computer.
Perforated screens and shielded cables should help to prevent
EM crosstalk. We will see.
> Do you use a switched power supply?
> If yes, what voltage do you use?
Yes I do, but only for computer and monitor. Both of them are 12V.
See two connectors on the right side (new attachment). Analog
part has a dedicated power. First I used just one 12V brick for
computer and monitor but power was so noisy that I "saw" 60Hz
on the screen
Even now when I use separate power supply (withseparate ground) for monitor it's noisy because power wires go
through the whole box. I should use shielded twisted pair.
Hopefully that should help.
> I looks like there is a trafo in the metal box just behind the LCD.
> It is well hidden.
To be honest, I borrowed that idea here:
http://users.podolsk.ru/boga/DAC.html
The box becomes a little bit warm. Probably I have to drill some holes on the top
> How does it work? Sound OK? No issues we all those digital
> signals and such?
This is still work-in-progress. Right now I can get audio output
only from the computer's LineOut, which is not a good source just
because it has a common ground with computer and it has some
kind of internal amplification already. That's why it's hard to
estimate RevC - garbage in-garbage out
Right now I'm trying to design a unit which will be a combination
of USB DAC and preamp for volume control (remote). Preamp will
be almost the same as your Kookaburra
just without outputbuffer because it will go directly to RevC. That empty perforated
cage in the middle is intended for that device.
Noise is the main problem in this design. That's why I've
isolate computer and audio grounds. They don't have common
power supplies and audio will be supplied through USB which is
digital differential signal and that's why noise should not come
through this way. I also won't use USB power from computer.
Perforated screens and shielded cables should help to prevent
EM crosstalk. We will see.
Attachments
Member
Joined 2003
That is quite an interesting project you have there. However it's not the first place I would choose to put the Mauro amp. It seems like such a noisy environment for such a nice amp. I would have chose to have the amplifier in a separate case from the computer. If an amp were needed inside a computer, I would probably choose some type of Class D amp, for two reasons. First is the it will be more efficient so it will add less heat to the amount already generated by the computer. Second is that they have a much better immunity to the high frequency noise generated by switching power supplies and cumputer parts.
You did do a very good job at cramming a lot of action into a small space
You did do a very good job at cramming a lot of action into a small space
> I would have chose to have the amplifier in a separate case from
> the computer.
Actually there will be a way to use only amp without
computer.
> I would probably choose some type of Class D amp...
I considered Tripath based AMP1-AMP6 amplifier as a first candidate
for this project but stopped on RevC because IMHO it's better
> noise generated by switching power supplies...
All switching power supplies are outside of the box.
> the computer.
Actually there will be a way to use only amp
withoutcomputer.
> I would probably choose some type of Class D amp...
I considered Tripath based AMP1-AMP6 amplifier as a first candidate
for this project but stopped on RevC because IMHO it's better
> noise generated by switching power supplies...
All switching power supplies are outside of the box.
Hi everybody:
I report that another My-reference amp saw the light yesterday
It shamelly waited for more than a week untested. The problem was that those other, long awaited, carton boxes arrived to my door while building the amp.
It worked at first shot. Voltmeter read 2mV DC at ouput! Can this be real??
Although this is my fourth pair of DIY amps (the other being modular) the success is all due to Mauro, Russ and Brian expertise.
The DIY heatsinks are cool
I only had time to listen through my test speakers( because my children wanted to see some DVDs with it) , but I can say it sounded detailed and had elegance and coherence in his performance.
I'll report back after brake-in and test with better speakers.
Audie:
Any advices?
Cheers
Mauricio
I report that another My-reference amp saw the light yesterday
It shamelly waited for more than a week untested. The problem was that those other, long awaited, carton boxes arrived to my door while building the amp.
It worked at first shot. Voltmeter read 2mV DC at ouput! Can this be real??
Although this is my fourth pair of DIY amps (the other being modular) the success is all due to Mauro, Russ and Brian expertise.
The DIY heatsinks are cool
I only had time to listen through my test speakers( because my children wanted to see some DVDs with it) , but I can say it sounded detailed and had elegance and coherence in his performance.
I'll report back after brake-in and test with better speakers.
Audie:
I know everything matters on signal path but I wanted quickly a working amp so I built it with all the parts, even when my digital sources are DC free. I can later mod it. In fact I will have to study the configuration of the Kooka concerning input and output buffers, wich are stuffed. Maybe I'll remove both.
Any advices?
Cheers
Mauricio
maxlorenz said:Hi everybody:
I know everything matters on signal path but I wanted quickly a working amp so I built it with all the parts, even when my digital sources are DC free. I can later mod it. In fact I will have to study the configuration of the Kooka concerning input and output buffers, wich are stuffed. Maybe I'll remove both.
Any advices?
Cheers
Mauricio
Mauricio,
Congrats, and Thanks!
To your question if your source to the kooka has no DC I would do this. Leave the input buffer (It improves input impedance) and omit the ouput buffer. Then remove the input caps on the REVC. I think you will be happy with the result.
The output buffer on the kooka is there mainly to support headphone use. As a preamp into anything more than 1K load the kooka does not need the output buffer at all.
Cheers!
Russ