Recapping of Nytech CPA 602
- Thread starter NRWler04
- Start date
S-Man
StrivingON
Turn it off
Seriously:
Check for oscillation
Check the bias level
Check the thermal feedback loop (i.e as the temp goes up the Vbe circuit voltage should reduce).
S-Man
StrivingON
I would suggest the "capacitive finger probing" test:
Dab you finger around on the tracks near the output transistors and Vbe mult. If the "fuzz" gets worse or better you have oscillation. If/when you find a point or 2 that kills the oscillation solder a small cap across the 2 points e.g 100 or 220pF.
Never ever do this procedure with a valve amp and be careful with high power ss amps!
Dab you finger around on the tracks near the output transistors and Vbe mult. If the "fuzz" gets worse or better you have oscillation. If/when you find a point or 2 that kills the oscillation solder a small cap across the 2 points e.g 100 or 220pF.
Never ever do this procedure with a valve amp and be careful with high power ss amps!
Just dab with my fingers on the aluminium profile where the output transistors are mounted? They are isolated to the profile with a mounting set.
Will do it tomorrow morning.
And what if not?
Regards from Germany
Ingo
S-Man
StrivingON
No you need to touch the transistor pins, try B-E and B-C. Also try in parallel with the stability cap (on the VAS).
If not, then you need to find out where the "fuzz" on the waveforms is coming from. Seems odd that it's on the input as well as the output (may be noise pickup or poor grounding).
If not, then you need to find out where the "fuzz" on the waveforms is coming from. Seems odd that it's on the input as well as the output (may be noise pickup or poor grounding).
Root Cause for oscillation found. Power Transistors MJ15024/MJ15025 replaced by original MJ15003/MJ15004.
Oscillation escaped, no heating effect.
So we have to replace the MJ15024/25 .....
In our test equipment the MJ15003/MJ15004 is now running since 8hrs without getting warm.
I'll keep you updated.
Oscillation escaped, no heating effect.
So we have to replace the MJ15024/25 .....
In our test equipment the MJ15003/MJ15004 is now running since 8hrs without getting warm.
I'll keep you updated.
jonnoshore
physicist, engineer and healer
Interesting read... Are these the equivalent of Nexus amps then?
More or less ....
Nearly two NEXUS in one box.
The NEXUS 3 will be the next step. But build with MJ's instead of Darlington's ....
And a lot of capacities in the PSU and the Output-Caps ....
That's just the idea i will follow.
We found some Oscillations .....
The Oscillation starts already at Transistor 1. Seems that the Oscillation ist caused by C5 - 470uF 35V. In the original 602 the capacity is only 100uF. We did not change the value of the related resistor. It is 130R. Is it neccessary to change the value to 270R as in the NEXUS?
The Oscillation starts already at Transistor 1. Seems that the Oscillation ist caused by C5 - 470uF 35V. In the original 602 the capacity is only 100uF. We did not change the value of the related resistor. It is 130R. Is it neccessary to change the value to 270R as in the NEXUS?
A little while ago we enjoyed a first demonstration of the new NERO sound and were highly impressed. But let's say first a big THANK YOU to the NRWler for being an audiophile host. Second our respect goes to his attempt to renew the sound of the old Nytech devices even in a better way not cutting the roots of the great old design.
We have had the pleasure to be ear witness on the first day of a functional complete line from preamp, active diplexer and power amplifiers. Behind all his great efforts stands the idea (and a very special kind of loyalty and dedication) to bring the ARC050 speakers again on stage. They really sound great, presenting a sound pattern not bounded to the speakers itself, stage become visible in room. It was a pleasure to hear these 30 years old speakers (original status, not refurbished) with a absolute clear presentation of the musicians, with no dynamical limitations, they got really fast driven by the new NERO devices with enough power for dynamic and punch, and NERO didn't lost the control of the speakers.
In our listening session good music source material pleased our ears but also presented us with an obstacle the NRWler got challenged. Capacitor brand does matter and has a real impact on sound quality. Concert guitar can loose the wooden aspect, sounding more like a steel guitar with a fiber body. Saxophon looses the mellow tone. Resistor in diplexer also matters. Electricial layout and function concept is one part, picking the correct pieces to build up the device is the other.
NRWler did right in his attempt to build up several devices of each kind to proof such issues and get around these sticking points. 100k instead of 110k gave guitar the natural sound quality back.
Conclusion: still stunning today what the Nytech & ARC design delivers to high fidelity hungry ears. Best of all this great rebirth didn't spent tons of euros on the hardware to get a compelling result.
Our hope is that these great results become the basis for a small manufactory in future.
Thx a lot for all the effort and passion!!!!
Regards Moritz & Father
We have had the pleasure to be ear witness on the first day of a functional complete line from preamp, active diplexer and power amplifiers. Behind all his great efforts stands the idea (and a very special kind of loyalty and dedication) to bring the ARC050 speakers again on stage. They really sound great, presenting a sound pattern not bounded to the speakers itself, stage become visible in room. It was a pleasure to hear these 30 years old speakers (original status, not refurbished) with a absolute clear presentation of the musicians, with no dynamical limitations, they got really fast driven by the new NERO devices with enough power for dynamic and punch, and NERO didn't lost the control of the speakers.
In our listening session good music source material pleased our ears but also presented us with an obstacle the NRWler got challenged. Capacitor brand does matter and has a real impact on sound quality. Concert guitar can loose the wooden aspect, sounding more like a steel guitar with a fiber body. Saxophon looses the mellow tone. Resistor in diplexer also matters. Electricial layout and function concept is one part, picking the correct pieces to build up the device is the other.
NRWler did right in his attempt to build up several devices of each kind to proof such issues and get around these sticking points. 100k instead of 110k gave guitar the natural sound quality back.
Conclusion: still stunning today what the Nytech & ARC design delivers to high fidelity hungry ears. Best of all this great rebirth didn't spent tons of euros on the hardware to get a compelling result.
Our hope is that these great results become the basis for a small manufactory in future.
Thx a lot for all the effort and passion!!!!
Regards Moritz & Father
Gentlemen,
another update: NERO Setup nearly completed .....
From left to right:
NERO SA 1 - Power Amp in double Mono Design based on Nytech CPA 602s
NERO EXO 1 - Electronic CrossOver for ARC 050
NERO PRE 24.4 - Pre Amp based on NAIM NAC 42 with 4 Power Rails - 24.5V
NERO SP 1 - Power Supply for PRE and EXO with 500VA Toroid
The setup makes quite nice noise
another update: NERO Setup nearly completed .....
From left to right:
NERO SA 1 - Power Amp in double Mono Design based on Nytech CPA 602s
NERO EXO 1 - Electronic CrossOver for ARC 050
NERO PRE 24.4 - Pre Amp based on NAIM NAC 42 with 4 Power Rails - 24.5V
NERO SP 1 - Power Supply for PRE and EXO with 500VA Toroid
The setup makes quite nice noise
Gentlemen,
my NERO's are finished and ready for listening. Please see the pictures. To bad that you can't listen to them over the www.
Many many thanks to lohk from Austria and Nytecholdie from UK for the support they gave me.
Everybody who is interested is invited for a listening session.
Best regards from Germany
Ingo
my NERO's are finished and ready for listening. Please see the pictures. To bad that you can't listen to them over the www.
Many many thanks to lohk from Austria and Nytecholdie from UK for the support they gave me.
Everybody who is interested is invited for a listening session.
Best regards from Germany
Ingo