Counterpoint NP220s

johnsonlwu

Well-Known Member
Apr 26, 2015
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STOP RIGHT THERE he likely DOESNT know what he's doing. I have HAD IT with those who claim to know how to service Counterpoint.
There is a combination of BIAS and DCO and predriver balance which requires 3 multimeters probing 3 things to adjust. He likely over-compensated the DCO pot causing your bias to run hot. You might end up frying your pre-drivers.
Buy 3 cheap multimeters and 3 pairs of cheap clip probes and check the darn thing yourself. Otherwise you will end up sending it to CA for me to repair!!!
Most people see the bias and DCO pots but fail to see the BAL pot (see 1st pic)
1.) hook 1 multimeter across speaker terminal, DCV. Goal is 0
2.) hook 2nd meter across bias test points (IMG_6227) on output driver card, DCV, goal is 50mV AFTER warm up for 10 min
3.) hook 3rd meter across TP1 and TP2 in first pic, goal is 650mV, this should be the same as TP3 and TP4 on motherboard next to TP1 andTP2, if not adjust BAL pot. Depending on your voicing resistors it may be anywhere from 580-750 but the goal is for the 2 phases 1/2 vs 3/4 to be balanced.

Adjust DCO to 0, you will see bias change
adjust bias accordingly. You may need to go back to DCO to tweak once you change bias.
Play safe and go for a LOW bias for starters, say fiddle with DCO and if you see bias shoot up back the hell off.

DO NOT over adjust, if you need to turn over 180 degress something is NOT right. Or you are reading something wrong.
It's a delicate balancing act.
 
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analyzer

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May 20, 2016
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Torino - Italy
I quite assure you that the technician worked carefully on my amp, he's reputated ("L'Audiotecnico" here in Torino).
http://www.audiotecnico.it/riparazioni.htm
I gave him the full instructions and service manual obtained by Mike Elliott for all NP-220 versions and the technician had already a long experience of Counterpoint's electronics.
He used three or four multimeters and he knows very well that any little change in one trimmer will interact with all lecture of values in all stages.
He finally told me that DCO has already some fluctuations, he consider it almost normal, mo more than 100mv; after warming the bias DCV value was around of 40 mv.
I don't know the lecture of multimeter of balance circuit .

In these days amp runs a little bit colder than in the first days; neverthless it's already more hot than in the 13 years of use in my home (Mike made the premium upgrade to me in 2006; it has the optional Plitron choke). Nothing excessive, I measured no more than 50 degrees Celsius in the heat sinks; the rest of the amp is almost cold.
I left the amp ON continously for four days without music; after that I started listening and after 25 hours listening it's opening with pleasure in the mids, now it has reached almost 30 hours listening and I'm satisfied with the sound; as Mike stated in his papers the adding of Plitron transformer and new Capacitors Nichicon Superthrough gave a better bass, more powerful and generally more dynamic overall and finally also a better detail retrieval.
I suppose that a little bit better sounds will arrive after 50-100 hours listening.
My further test will be to try a different tube than my beloved Sylvania VT-231 and maybe to try an EZ80 (the best provided by Mike) in place of 6BW4 I use now.
The technician examined the circuit and told me that it seems that pin 3 and 9 are connected in my amp so probably I can use both.

In any case maybe I'll follow your kindly and detailed alert and I'll take the amp in the next month to the technician for another check if values are correct.
My best best thanks and regards
Marco
 
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Barry

Member Sponsor
Jan 7, 2012
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Somewhere near Philadelphia, USA
Johnsonlwu thanks for the biasing/DC offset instructions!!! May have to check mine. too bad you don't live closer.... I'd have you do some other fine tuning.

Analyzer, try the RFT EZ80s. They're terrific, readily available, and are cheap on Ebay and elsewhere.
 
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E9Guy

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Jun 28, 2019
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Hello folks,

So glad to find a current board on counterpoint amps.

I'm new here and need some beginners advise. First up, I was given what I thought was an SA-20. Much to my surprise and delight, it's actually an NP220 "1999 upgrade" done by Alta Vista.
Unfortunately it's first run after letting it warm up yealded granny audio and hardly any volume gain.

I would really appreciate feedback on which 6SN7's to use (or otherwise) as well do I need to order a new rectifier ? (6CA4/EZ81).

My hope is drop in new tubes and off we go as opposed to finding someone who thinks they know what they're doing.

Thanks for any feedback.

Orion
 

E9Guy

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Jun 28, 2019
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Don't forget to check the fuses. There are 4 PS rail fuses on the main board, 1 each on the 4 ouput boards on the sides of the amp and there's also 1 line fuse behind the front panel.

Thanks Barry.
All the fuses are visibly intact. Would tired tubes cause what I described?

Thanks again
 

E9Guy

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Jun 28, 2019
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Does anyone have a recommendation on which brand of 6sn7 work best with this amp? Thanks in advance.
 

analyzer

VIP/Donor
May 20, 2016
315
137
220
Torino - Italy
I tried many tubes in my NP220 (2006 version). I finally ended with Sylvania VT-231 WWII version.
They are not the best of the best, Tungsol of the same era have slightly better extension at extremes, Ken-Rad VT-231 have more bass and so on... but the Sylvania in my opinion are very well balanced overall. Excellent detail; nice sound presentation, good focus; not harsh in the mid-highs... so I'm sure that they are a respectable choice.
About rectifiers my favourite are EZ80 or EZ81 German made RFT; they are also cheap on ebay.
I strongly recommend a technical check to your unit; you have surely read this thread so it will be better to verify set-up values of bias, channel balance and DCoffset in a laboratory
 
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E9Guy

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I tried many tubes in my NP220 (2006 version). I finally ended with Sylvania VT-231 WWII version.
They are not the best of the best, Tungsol of the same era have slightly better extension at extremes, Ken-Rad VT-231 have more bass and so on... but the Sylvania in my opinion are very well balanced overall. Excellent detail; nice sound presentation, good focus; not harsh in the mid-highs... so I'm sure that they are a respectable choice.
About rectifiers my favourite are EZ80 or EZ81 German made RFT; they are also cheap on ebay.
I strongly recommend a technical check to your unit; you have surely read this thread so it will be better to verify set-up values of bias, channel balance and DCoffset in a laboratory

Thanks for your reply. Yes, I do plan on having it checked out and bringing a fresh set of matched tubes to go with. And probably print out this thread for service reference as it's the most informative I've come upon in all my searching. Sorry folks, didn't mean hijack the thread.
 

johnsonlwu

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Apr 26, 2015
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If you happen to be in NorCal I can certainly help. I own many and have fixed many Counterpoint NPs.
 
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analyzer

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Torino - Italy
just a little update. since I find that my NP220 after the upgrade of a new Plitron custom transformer and new Nichicon superthrough condenser was running too hot (50 degrees celsius measured on heatsinks) I take the amp back to the technician, he decided for a more conservative low bias overall (among 38 mv), also DCO and balance predriver values are correct; now the amp running cooler.
Neverthless I find that now the sound is not so dynamic and prompt as before. It's a subtle difference, neverthless audible; I listenend to many discs and I feel that when the amp had a bias value higher (it was around 45 mv that is also far from the goal of 50 mv) it was better performing.
I'm asking if there's a relation in SS amps concerning sound performance and bias calibration...:rolleyes:
 

E9Guy

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Jun 28, 2019
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If you happen to be in NorCal I can certainly help. I own many and have fixed many Counterpoint NPs.[/QU

Was hopping someone could shed some light for me. I had the NP220, serviced recently including New tubes and rectifier. My issue is that while it sounds really great in the mid to upper frequencys it is lacking is bass control and regardless of how I connect it, RCA vs XLR I'm not getting what I feel is it full power capacity.

I'm using a B&K 507s2 for a pre amp. The B&K rated at 100 less watts per channel would be plenty loud at +5 (let's not go any further). By comparison used as a pre amp is easy to listen to and moderately "loud" with the volume maxed out at +15. ( -75 is the starting point.)

I'm not trying to recreate Woodstock by any means with volume level but occasionally I want just a little more and was curious why it (the NP 220) would be relatively quiet in comparison to a less powerful yet very good AV receiver? Does the AMP need further tuning ? The Tech had stated it was producing 230 at 8ohms what's a dummy load tester consistently.

I really enjoy how it sounds overall but still feeling missing the impact and bass drive the B&K delivered with ease.

The speakers are Wilson Audio Which are 89db so shouldn't be difficult for any modest amp to drive.

Any thoughts would be greatly appreciated.
 

johnsonlwu

Well-Known Member
Apr 26, 2015
27
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I take it your NP220 uses 6SN7 (not 6SL7) tubes? If so the gain is a mere 18dB and you need "old school" high gain preamps like Audio Research SP10 or MFA Lumi to wake it up otherwise it does sound sleepy. Also the design lacks NFB so bass control is expected to be a bit flabby.
 
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E9Guy

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I take it your NP220 uses 6SN7 (not 6SL7) tubes? If so the gain is a mere 18dB and you need "old school" high gain preamps like Audio Research SP10 or MFA Lumi to wake it up otherwise it does sound sleepy. Also the design lacks NFB so bass control is expected to be a bit flabby.

How would one know if a preamp is high gain? What's NFB? I'm hoping to make this amp sound as special as everyone claims. It's close I think except for the bass.

Thanks
 
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E9Guy

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Jun 28, 2019
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Does anyone have ideas on why the bass is so flabby? While the kids and high end of amazing? Would a different solve this?

Thanks

Also in the event that I do decide to sell it, what's a realistic asking price for a freshly tuned NP220?
 

DonH50

Member Sponsor & WBF Technical Expert
Jun 22, 2010
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just a little update. since I find that my NP220 after the upgrade of a new Plitron custom transformer and new Nichicon superthrough condenser was running too hot (50 degrees celsius measured on heatsinks) I take the amp back to the technician, he decided for a more conservative low bias overall (among 38 mv), also DCO and balance predriver values are correct; now the amp running cooler.
Neverthless I find that now the sound is not so dynamic and prompt as before. It's a subtle difference, neverthless audible; I listenend to many discs and I feel that when the amp had a bias value higher (it was around 45 mv that is also far from the goal of 50 mv) it was better performing.
I'm asking if there's a relation in SS amps concerning sound performance and bias calibration...:rolleyes:

Very much so but I have never seen a SS preamp or amp with user-adjustable bias settings, or at least not a long time. The gain of internal stages is higher, SS devices do not usually drift in performance over time as much as tubes, and generally more feedback is applied, so bias is more stable. There is also no visual warning if you overbias, they usually just quickly heat up and destroy themselves. Bias is usually fixed by design and thus is one of the myriad variables baked into the "secret sauce" of the design.

That said, those of us who have designed and built amps, even kits, will remember having to make various bias adjustments to dial them in (Ampzilla, anyone?)

HTH - Don
 

analyzer

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May 20, 2016
315
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Torino - Italy
Does anyone have ideas on why the bass is so flabby? While the kids and high end of amazing? Would a different solve this?

Thanks

Also in the event that I do decide to sell it, what's a realistic asking price for a freshly tuned NP220?


I must tell you that bass was flabby also in my NP220 (premium upgrade) until I've made a further upgrade with specifications near "premium gold" (changing the old electrolytic with new Nichicon superthrough AND new Plitron custom transformer) so this made a great step in better bass, more heavier and defined. Now is very competitive with modern products. The NP220 is still overall inferior to best power amps, that obviously cost much much more also in the second-hand market. Just for sharing I was impressed by Viola Bravo and Boulder 2060, but prices are very different also in used market. You must spend much much more in order to have better sound.
About evaluation I rarely have seen NP-220 for sale on the web in the last years; I remember a "basic" unit in US gone for about 1500 USD and another unit ("premium") in Australia two years ago sold for only 2000 USD.
Here in Europe they are unfindable. I suggest that 1500-1800 for a "basic upgraded" and 2200-3000 USD for a "premium" or "premium gold" would be a correct price. But this is just my opinion.
If you find one pay attention also to the sensitivity... there are two different version ("low" and "high"); the first one must be coupled to high gain preamps (at least 14-16 db gain and with an output level of more than 10Volts since the sensitivity of the circuit designed by Mike Elliott is VERY low..
My best
Marco
 
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E9Guy

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I need help guys,

Amp is now making a loud buzz through the speakers. No relationship to volume from the preamp. I had to immediately shut it off for fear of speaker damage. It was playing perfectly fine a moment before. Any ideas?

Ironically I was just about to list it for sale.
 

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