Hello All,
I have come into possession of 2 late model Counterpoint/EASE NPS-400 amps. The back panel is labeled Counterpoint NPS-40 while the front panel calls them EASE Signature Series Fidelis-400. They work fine but sound a bit dull and uninvolving. I am planning to check out the tubes, electrolytics, and voltages to see if anything has gone awry over the last 30 years. I do have a couple questions for you all:
From what I have found on this site the person to get service manuals from is Mrs. Weber. Does anybody know if that is still the case?
I've heard that these can be run bridged/mono. I can't find a switch labeled "Stereo/Mono" or anything to that effect. Is this something that needs to be done internally?
Has anybody worked on these amps and found if cap or tube replacements will make any difference in the sound?
Thanks in advance!
TKO
I have come into possession of 2 late model Counterpoint/EASE NPS-400 amps. The back panel is labeled Counterpoint NPS-40 while the front panel calls them EASE Signature Series Fidelis-400. They work fine but sound a bit dull and uninvolving. I am planning to check out the tubes, electrolytics, and voltages to see if anything has gone awry over the last 30 years. I do have a couple questions for you all:
From what I have found on this site the person to get service manuals from is Mrs. Weber. Does anybody know if that is still the case?
I've heard that these can be run bridged/mono. I can't find a switch labeled "Stereo/Mono" or anything to that effect. Is this something that needs to be done internally?
Has anybody worked on these amps and found if cap or tube replacements will make any difference in the sound?
Thanks in advance!
TKO
I have a pair of NPS400 and NPS200
Yes the 400 is dull compared to the 200.
The back panel should have a bridge flip switch for bridging but unless you have 2 of them or want to play mono dont bother
Also the old bridging wiring involves BOTH tubesinstead of really using the long tail pair of one tube. The resulting sound is pretty terrible.
The fidelis takes out the constant current source and sink that sandwiches the tube in earlier units making it more tube-like and transparent already.
If you want to make modsMAKE VERY SURE you knowhow to remove the electrolytics without damaging the traces. The B+ regulator has 1 cap that has a vry thin trace on top (right under the cap).
Use Nichicon KX and use a smaller value like 56uF for the cap on the base of the regulator transistor
Use a Nichicon KZ 1000uF or 2200uF for the B- regulator.
A pair of Mundorf coupling caps will brightne the sound a wee bit.
Yes the 400 is dull compared to the 200.
The back panel should have a bridge flip switch for bridging but unless you have 2 of them or want to play mono dont bother
Also the old bridging wiring involves BOTH tubesinstead of really using the long tail pair of one tube. The resulting sound is pretty terrible.
The fidelis takes out the constant current source and sink that sandwiches the tube in earlier units making it more tube-like and transparent already.
If you want to make modsMAKE VERY SURE you knowhow to remove the electrolytics without damaging the traces. The B+ regulator has 1 cap that has a vry thin trace on top (right under the cap).
Use Nichicon KX and use a smaller value like 56uF for the cap on the base of the regulator transistor
Use a Nichicon KZ 1000uF or 2200uF for the B- regulator.
A pair of Mundorf coupling caps will brightne the sound a wee bit.
Thanks for the reply.
I was able to get 2 of these amps
The amps are at my office so I can't check for the bridge switch tonight. I'll get it next time I go in. If bridging is as bad as you say then I guess it doesn't matter if it there or not...
Thanks for the info on the caps. I'll have to take a really good look before pulling out my iron. Have you had any issues with the power supply caps?
Also, any recommendations on tube rolling?
I was able to get 2 of these amps
The amps are at my office so I can't check for the bridge switch tonight. I'll get it next time I go in. If bridging is as bad as you say then I guess it doesn't matter if it there or not...
Thanks for the info on the caps. I'll have to take a really good look before pulling out my iron. Have you had any issues with the power supply caps?
Also, any recommendations on tube rolling?
Make sure the2 units look the same
The NPS400 vs mkii/fidelis have completely different gain.
Different production batches are also voiced differently with a combination of 3 resistors.
Tubes.... it's all your personal preference. I changed my units to use a 8.2k Cathode resistor and 33k plate and use a 6FQ7, so I cant comment on 6922.
if you want a crisper sound you can certainly use film caps 500V 55uF for the final bypass for the B+ (a 220uf 400V cap next to the 6922).
The NPS400 vs mkii/fidelis have completely different gain.
Different production batches are also voiced differently with a combination of 3 resistors.
Tubes.... it's all your personal preference. I changed my units to use a 8.2k Cathode resistor and 33k plate and use a 6FQ7, so I cant comment on 6922.
if you want a crisper sound you can certainly use film caps 500V 55uF for the final bypass for the B+ (a 220uf 400V cap next to the 6922).