MikeB:
I have completed my SYMASYM and connected it to my main stereo system and the result is no less than phenomenol. It beats my previous DOZ power amp in every aspect:
1. The mid range is noticebly better than the DOZ. It sounds more open, clearer, sweeter and more dynamic. I do have to run the output transistors at 725 ma bias to schieve the result. At 500 ma it did not sound quite as open or dynamic. I was not able to increase the bias beyond 725 ma with my current power supply and the 1000 Ohm trimmer.
2. The frequency response is very good. The highs and lows really shines.
3. The 60 Hz noise is very low.
4. I used a SCSI CROM, a soundcard and a California Audio DAC with the DOZ to achieve satifactory sound. With SYMASYM I only use a standalone SCSI CDROM drive.
5. I had to use a tube preamp for the DOZ to improve the sound and I am able to bypass with the SYMASYM.
I believe the SYMASYM is not only an excellent power amp, its voltage amplification stage also matches the performance of the best preamps available, supplying plenty of sweet second harmonics.
Thank you again for giving me a chance to own such a beautiful instrument without beaking the bank.
P.S. I used MJL0281/MJL0302 power transistors, Blackgates as input capacitors and some Cerafines and blackgates at power bypass.
I have completed my SYMASYM and connected it to my main stereo system and the result is no less than phenomenol. It beats my previous DOZ power amp in every aspect:
1. The mid range is noticebly better than the DOZ. It sounds more open, clearer, sweeter and more dynamic. I do have to run the output transistors at 725 ma bias to schieve the result. At 500 ma it did not sound quite as open or dynamic. I was not able to increase the bias beyond 725 ma with my current power supply and the 1000 Ohm trimmer.
2. The frequency response is very good. The highs and lows really shines.
3. The 60 Hz noise is very low.
4. I used a SCSI CROM, a soundcard and a California Audio DAC with the DOZ to achieve satifactory sound. With SYMASYM I only use a standalone SCSI CDROM drive.
5. I had to use a tube preamp for the DOZ to improve the sound and I am able to bypass with the SYMASYM.
I believe the SYMASYM is not only an excellent power amp, its voltage amplification stage also matches the performance of the best preamps available, supplying plenty of sweet second harmonics.
Thank you again for giving me a chance to own such a beautiful instrument without beaking the bank.
P.S. I used MJL0281/MJL0302 power transistors, Blackgates as input capacitors and some Cerafines and blackgates at power bypass.
DOZ, beeing a JLH design is only a reference, and a very good one.
Even Mr. Bittner used it to compare and observed how good was his design, as beated JLH in the early days.
When we evaluate something, we need a reference, at least the reference can "translate" to other fellows what the word "better" means.
In the language, we use better THAN this amplifier..... worst THAN that other amplifier..... almost the SAME as this one here....well, without some "audible" reference, you will have some problems to mention.
- "This amplifier response curve is better than MY reference amplifier"
- And you will need to explain how good is the reference amplifier.
- The guy will need to listen and to have your reference amplifier in his home to realise, to figure what you told.
- Also will need both curves, from the "A" amplifier and the "B" amplifier to observe the displacement, the diferences.
JLH and DOZ are not poor designs, observing their age.
When designed they were revoluctionary, at least the John Lindsey Hood design, and so good it was that enormous quantity of audiophiles respect them as a very good amplifier.
Well Epupa, i am still realising that you like to go kiding with us.... of course you cannot believe in some ideas you publish.
You are funny...attached, my smile to you...hehe
regards,
Carlos
Even Mr. Bittner used it to compare and observed how good was his design, as beated JLH in the early days.
When we evaluate something, we need a reference, at least the reference can "translate" to other fellows what the word "better" means.
In the language, we use better THAN this amplifier..... worst THAN that other amplifier..... almost the SAME as this one here....well, without some "audible" reference, you will have some problems to mention.
- "This amplifier response curve is better than MY reference amplifier"
- And you will need to explain how good is the reference amplifier.
- The guy will need to listen and to have your reference amplifier in his home to realise, to figure what you told.
- Also will need both curves, from the "A" amplifier and the "B" amplifier to observe the displacement, the diferences.
JLH and DOZ are not poor designs, observing their age.
When designed they were revoluctionary, at least the John Lindsey Hood design, and so good it was that enormous quantity of audiophiles respect them as a very good amplifier.
Well Epupa, i am still realising that you like to go kiding with us.... of course you cannot believe in some ideas you publish.
You are funny...attached, my smile to you...hehe
regards,
Carlos
Attachments
Hi Tim, thanks for the compliments !
Phew, 725ma, that's quite a heavy bias ! Have you also tried 113ma ?
If you use that "highend" elyts, you might be able to skip the 100nf bypass caps, except maybe the dc-blocking one.
One question, you said you use a standalone cdrom, does this mean you use the internal DAC of the drive ? But, of course, using less devices in the signal path is always recommendable...
The MJL0281/MJL0302 seem a good choice, they show good sound.
If you want to increase bias further, you need to decrease the 500ohms in series with the trimpot (R24), maybe 330ohms.
Nice to hear that you are very pleased !
Pavel, i also used the DoZ to compare, i think of this amplifier beeing a great one regarding its simplicity, i was stunned by its sound. But for my taste it was too colorized and had too low DF...
Mike
Phew, 725ma, that's quite a heavy bias ! Have you also tried 113ma ?
If you use that "highend" elyts, you might be able to skip the 100nf bypass caps, except maybe the dc-blocking one.
One question, you said you use a standalone cdrom, does this mean you use the internal DAC of the drive ? But, of course, using less devices in the signal path is always recommendable...
The MJL0281/MJL0302 seem a good choice, they show good sound.
If you want to increase bias further, you need to decrease the 500ohms in series with the trimpot (R24), maybe 330ohms.
Nice to hear that you are very pleased !
Pavel, i also used the DoZ to compare, i think of this amplifier beeing a great one regarding its simplicity, i was stunned by its sound. But for my taste it was too colorized and had too low DF...
Mike
Carlos, I don't like " funny " amps 
- JLH and DOZ are these ones.... I can't take enthusiasm to begginers, but with five transistors you can do any miracles.... Also I can't " beat " to someone... some of my design you can see at http:// margo.student.utwente.nl/el/ampz/dpa330.html - but they are rather old
- JLH and DOZ are these ones.... I can't take enthusiasm to begginers, but with five transistors you can do any miracles.... Also I can't " beat " to someone... some of my design you can see at http:// margo.student.utwente.nl/el/ampz/dpa330.html - but they are rather old
Hi MikeB:
I just tried 113 ma and found out that bias level is a matter of compromise and personal preference. I found that 113 ma level gives me a lot of sweet harmonics, a very dynamic sound and a deeper/wider sound stage, but it also gives me a slightly restricted middle, most noticeble in human voices. Now I am running at 236 ma without compromising much of the merits of 113 ma, but with a more open middle. I suppose that I went overboard a little at 500ma and 725ma, since I was so used to the pure class A sound of DOZ. Of course, this restricted middle may also due to that my Blackgates are not quite break-in yet. They are known to take at least 200 hours to form properly.
Yes, I am using the internal DAC of an external SCSI CDROM (Plexor PLEX12). I am quite surprised that it can sound so good with SYMASYM. As I mentioned before I had to use a M-Audio sound card, an external DAC and a Tube preamp to make the DOZ sound decent.
Hi Pavel:
Due to my personal preference of a clear and open sounding middle, I compromised on a class A DOZ with a lot of tweeking on my CD source and a tube preamp. I found it pretty listenable dispite its apparent draw backs in lack of dynamics, not much sound stage, weak bass and not quite satisfying highs. The SYMASYM is of course far superior but it was not available when I built the DOZ. Besides, due to my lack of in depth knowledge in electronics and lack of a reliable review source, I could not judge the quality of an amp before I build it and listen to it myself. I am really really happy that I found SYMASYM in this forum and built myself a top-notch amp.
I just tried 113 ma and found out that bias level is a matter of compromise and personal preference. I found that 113 ma level gives me a lot of sweet harmonics, a very dynamic sound and a deeper/wider sound stage, but it also gives me a slightly restricted middle, most noticeble in human voices. Now I am running at 236 ma without compromising much of the merits of 113 ma, but with a more open middle. I suppose that I went overboard a little at 500ma and 725ma, since I was so used to the pure class A sound of DOZ. Of course, this restricted middle may also due to that my Blackgates are not quite break-in yet. They are known to take at least 200 hours to form properly.
Yes, I am using the internal DAC of an external SCSI CDROM (Plexor PLEX12). I am quite surprised that it can sound so good with SYMASYM. As I mentioned before I had to use a M-Audio sound card, an external DAC and a Tube preamp to make the DOZ sound decent.
Hi Pavel:
Due to my personal preference of a clear and open sounding middle, I compromised on a class A DOZ with a lot of tweeking on my CD source and a tube preamp. I found it pretty listenable dispite its apparent draw backs in lack of dynamics, not much sound stage, weak bass and not quite satisfying highs. The SYMASYM is of course far superior but it was not available when I built the DOZ. Besides, due to my lack of in depth knowledge in electronics and lack of a reliable review source, I could not judge the quality of an amp before I build it and listen to it myself. I am really really happy that I found SYMASYM in this forum and built myself a top-notch amp.
MikeB said:Hi !
Here is a preview fresh out of sims for a high power version of symasym... ...
Some specs:
max power: 500watt rms into 4ohms,>250 watts into 8ohms
THD: <0.04% for 500watts (20khz), <0.0006% for 20watts (20khz into 4ohm)
Bodeplot and stepresponse look fine...
I am not sure if 3 output pairs are sufficient, i doubt it.
What do you think ?
Of course i have no idea yet if it sounds good... (it should)
Mike
I think you better go to MOSFET outputs. Bipolar outputs will have to be cascoded to work at these voltages, due to second breakdown limitations, and that doubles the cost, making MOSFETs a cheaper and more reliable solution. With fan cooling, this will barely work with 3 pairs of MOSFETS, depending on the outputs chosen.
See the Dynaco 400 and the Leach Super Amp for examples of cascoded bipolar outputs that work. The Hafler DH500 is a working example using thre output pairs and forced air cooling. At these power levels, cooling is a big challenge.
The infamous Phase Linear 400 was just this design, and earned Bob Carver the nickname Torch, and the company the name Phlame Linear.
Terry,
not only "anyone". There was a production series of the DPA amplifiers produced by Upupa Epops's former company here in the Czech Republic. Hundreds were produced by the company and hundreds by DIYers. There were BJT series without Hawksford correction and MOSFET series with Hawksford correction. The Mosfet series sounded even better. These amps had very low distortion and very very clean sound. In fact they were one of the best I ever heard. They served as a reference in many listening tests.
Regards,
Pavel
P.S. The very low distortion remained even some 1dB below limitation.
not only "anyone". There was a production series of the DPA amplifiers produced by Upupa Epops's former company here in the Czech Republic. Hundreds were produced by the company and hundreds by DIYers. There were BJT series without Hawksford correction and MOSFET series with Hawksford correction. The Mosfet series sounded even better. These amps had very low distortion and very very clean sound. In fact they were one of the best I ever heard. They served as a reference in many listening tests.
Regards,
Pavel
P.S. The very low distortion remained even some 1dB below limitation.
PMA said:
Pavel,
Yes, nice design, maybe a bit complex, but I believe if such
linearity is the goal then it is difficult to do with simple circuit.
It depends on the designers intent.
So - how would you compare something like the Symasym to
these Epop / hawksford EC amps sonically?
And for that matter what do you think is the ultimate embodiment
of a SS amp?
It appears that these Epop / EC amps are more linear than
just about anything done here, symasym and ska included.
Cheers,
Terry
Terry,
there is a lot of DPA amplifiers in use here even now. We have not made the direct comparison to SymaSym yet, but I believe it will be done.
You are right, regardind linearity specs the DPAs are second to none. They require very good audio chain to show their best abilities.
Regards,
Pavel
there is a lot of DPA amplifiers in use here even now. We have not made the direct comparison to SymaSym yet, but I believe it will be done.
You are right, regardind linearity specs the DPAs are second to none. They require very good audio chain to show their best abilities.
Regards,
Pavel