I read from audioreview.com a certain Mike had this to share in his review. "When I first took the PA-5 home I thought it airy and very nice..until I played Judy Collins and other high-pitched singers. They sounded truly bad,like early solid-state recievers. I put the amp on the test bench and found that it easily met all its specs. So what was wrong? Well,when I put square waves into the amp (a way of testing the transient and phase behavior of an amplifier)they did not come out the way they went in...this is never a good thing. Upon analysis I found that the feed-back loop was not configured to properly address the low midrange/upper bass. Attempting to find out what was up I called Nakamichi. Everyone I spoke to refused to talk to me about it...until I got to one brave tech who told me he knew what I was talking about but would be fired if he said anything!
Well,it turned out the solution was to examine a REAL Stasis amp and incorporate the componant feedback values into the PA-5. What a difference! The amp was warmer with better dynamics and the voices were now coherent. It seems that Nakamichi set the feedback values to make the amp look good on paper at the sacrifice of its real world
performance! At any rate the total cost of parts was $5.00
so I would not hesitate to buy this amp on the used market.
Now to the sound...The PA-5 has a warm softly detailed quality,never bright, and is very gentle on the ears. It produces a COHERENT soundstage." You can find this here:Nakamichi PA-5 Videos and Related Media
My question is does this make sense? Can anyone share their thoughts on this? Does anybody know the feedback value of the Stasis amp? Does all the Stasis amps have the same feedback value? I have a PA 5-A and wouldn't mind spending $5 investment for such great improvement. It will also help others have the PA-5 or help others maybe get one and do the cheap upgrade.
Your help will be greatly APPRECIATED!!!
Well,it turned out the solution was to examine a REAL Stasis amp and incorporate the componant feedback values into the PA-5. What a difference! The amp was warmer with better dynamics and the voices were now coherent. It seems that Nakamichi set the feedback values to make the amp look good on paper at the sacrifice of its real world
performance! At any rate the total cost of parts was $5.00
so I would not hesitate to buy this amp on the used market.
Now to the sound...The PA-5 has a warm softly detailed quality,never bright, and is very gentle on the ears. It produces a COHERENT soundstage." You can find this here:Nakamichi PA-5 Videos and Related Media
My question is does this make sense? Can anyone share their thoughts on this? Does anybody know the feedback value of the Stasis amp? Does all the Stasis amps have the same feedback value? I have a PA 5-A and wouldn't mind spending $5 investment for such great improvement. It will also help others have the PA-5 or help others maybe get one and do the cheap upgrade.
Your help will be greatly APPRECIATED!!!
Sorry I am not a tech guy and I am wondering if what he said makes sense. Does it makes sense to you? thanks for the reply.
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Just took a look at the schematics for the PA-5, PA-7 and several Stasis amplifiers.
The PA-5 and PA-7 have a 10uF (C102) in the feedback loop, giving a low frequency roll off at ~ 50Hz.
The Stasis amplifiers have a 470uF capacitor, giving a low frequency roll off at ~ 2Hz.
Even so, I have never noticed my PA-7 being deficient in bass response.
The PA-5 and PA-7 have a 10uF (C102) in the feedback loop, giving a low frequency roll off at ~ 50Hz.
The Stasis amplifiers have a 470uF capacitor, giving a low frequency roll off at ~ 2Hz.
Even so, I have never noticed my PA-7 being deficient in bass response.
Thanks again for the reply. Based on what he said...
"Well,it turned out the solution was to examine a REAL Stasis amp and incorporate the componant feedback values into the PA-5. What a difference! The amp was warmer with better dynamics and the voices were now coherent. It seems that Nakamichi set the feedback values to make the amp look good on paper at the sacrifice of its real world performance! At any rate the total cost of parts was $5.00 so I would not hesitate to buy this amp on the used market. Now to the sound...The PA-5 has a warm softly detailed quality,never bright, and is very gentle on the ears. It produces a COHERENT soundstage."
...is it possible that what he was driving at could be to change the 10uF (C102) in the feedback loop of the PA-5 that was giving 50Hz to whatever was needed (can be the same value of 470uF capacitor) to reach 2Hz then things will improve?
"Well,it turned out the solution was to examine a REAL Stasis amp and incorporate the componant feedback values into the PA-5. What a difference! The amp was warmer with better dynamics and the voices were now coherent. It seems that Nakamichi set the feedback values to make the amp look good on paper at the sacrifice of its real world performance! At any rate the total cost of parts was $5.00 so I would not hesitate to buy this amp on the used market. Now to the sound...The PA-5 has a warm softly detailed quality,never bright, and is very gentle on the ears. It produces a COHERENT soundstage."
...is it possible that what he was driving at could be to change the 10uF (C102) in the feedback loop of the PA-5 that was giving 50Hz to whatever was needed (can be the same value of 470uF capacitor) to reach 2Hz then things will improve?
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Thank you for the help. I have to find time as well as ask somebody to help me do this. Will get back to you as soon as I get to try it.
A little knowledge can be dangerous. Do you actually believe the Nak engineers are that stupid?
The PA-5 circuit appears virtually identical to the Threshold circuits. After staring at it for a while the only topological difference i can spot is the VAS which is a cascode in the Threshold amps. No idea if this alone can bring such a substantial difference in sound but with some imagination i can see it being transplanted dead-bug style on the Nak board - it's just a single transistor and biasing. Then there is the slightly different compensation, the protection relay and obviously all the different parts. Nothing looks in any way inferior than the Threshold amps. I suspect ** in the audioreview quote.
My experience is that bias values are the most likely issue.
Nak's circuits seem to be intelligently done as a rule, but
the circuit does depend on a healthy output stage bias -
something that doesn't reflect in the curves.
If you can adjust the bias so that the long term heat sink
figures are 50 deg C (cover on, 2 hours later, etc.) then you
may experience an improvement.
😎
Nak's circuits seem to be intelligently done as a rule, but
the circuit does depend on a healthy output stage bias -
something that doesn't reflect in the curves.
If you can adjust the bias so that the long term heat sink
figures are 50 deg C (cover on, 2 hours later, etc.) then you
may experience an improvement.
😎
nak stasis
The answer to that question might be yes and that nak sacrificed sonics for a higher power bandwidth specification and learned from their mistake. Found this in wikipedia. Its about the hta amplifier they designed following stasis.The time alignment of an amplified music signal and its distortion components has a profound effect on perceived sound quality. Nakamichi researchers discovered that the human ear is much more tolerant of harmonic distortion if the distortion components are time-aligned with respect to the primary signal. Nakamichi Harmonic Time Alignment (HTA) amplifiers adopt a wideband, low open-loop gain design. A MINIMAL AMOUNT OF NEGATIVE FEEDBACK IS USED BUT MORE IMPORTANTLY IT IS KEPT CONSTANT OVER THE ENTIRE AUDIO SPECTRUM This assures the proper timing between the primary signal and any amplifier distortion components. The sonic benefits of this design include powerful, high-resolution bass, a natural, richly detailed midrange, and smooth, clear highs. [citation needed]
Ha ha! Great advice from the man who knows best. I was looking at buying a nak pa5. I will have to do that after reading these posts.
I agree with OP, PA5 too bright
NRG2009, I'm also in Detroit. I'm interested in what could be done to bring out more base and reduce the PA5's brightness. Are you aware of what needs to be done?
NRG2009, I'm also in Detroit. I'm interested in what could be done to bring out more base and reduce the PA5's brightness. Are you aware of what needs to be done?
Look again at post #4 of this thread.
Low frequency gain is set by capacitance C102 in feedback loop.
PA-5 has 10uF, strangely rated at an excessively high 200V. It is not bi-polar.
PA-5 II has 220uF, rated at 15V and it is bi-polar.
Changing C102 from 10uF to 220uF will increase low frequency gain.
At 1000Hz, gain will increase from 27.1 dB to 27.2 dB.
At 50 Hz, gain will increase from 26.1 dB to 27.1 dB.
At 7 Hz, gain will increase from 21.5 dB to 26.8 dB.
At 2 Hz, gain will increase from 15.3 dB to 25.9 dB.
It is also possible that the 10uF, 200V non-bipolar capacitor is adding to the brightness by changing it's capacitance as voltage across it changes from positive to negative. This capacitor should be bi-polar.
Low frequency gain is set by capacitance C102 in feedback loop.
PA-5 has 10uF, strangely rated at an excessively high 200V. It is not bi-polar.
PA-5 II has 220uF, rated at 15V and it is bi-polar.
Changing C102 from 10uF to 220uF will increase low frequency gain.
At 1000Hz, gain will increase from 27.1 dB to 27.2 dB.
At 50 Hz, gain will increase from 26.1 dB to 27.1 dB.
At 7 Hz, gain will increase from 21.5 dB to 26.8 dB.
At 2 Hz, gain will increase from 15.3 dB to 25.9 dB.
It is also possible that the 10uF, 200V non-bipolar capacitor is adding to the brightness by changing it's capacitance as voltage across it changes from positive to negative. This capacitor should be bi-polar.
Would these calculations apply to a PA7 Mk I, and would you therefore recommend the same mod? And should it be a MUSE or SILMIC II?
A couple of off-topic PA7 questions: what would be the electrical and package specs for the PA7 bridge rectifiers, and what are the physical dimensions of the 4 33,000µF PS caps?
Thank you very much.
Nak PA 7 filter cap and bridge
Greetings!
I have been rebuilding a PA 7. It has been rewarding but frustrating since the info is scattered about. I am considering starting a PA 7 update page so that we can bring our collective knowledge together. I totally missed this PA 5 page and for a long time didn't have some key information.
Regarding the main cans, I was not completly satisfied with the sound even after recaping the boards with wima, muse, and cerifine caps. The amp still sounded rather closed in with soft bass and poor high end extension.
I have recaped many vintage recievers and have heard many of them sound really sub-par with the old cans. It is amazing what a difference they can make! Sometimes the old ones will reform and sound really good. I am using a HK 930 that sounds great with the origional cans! Often though, they will sound awful at first listen, really dynamicly constipated. Try turning up the volume and it's like running into a wall. Then after a few days the sound really loosens up. It seemed the same thing was going on with the NAK.
Replacement cap options are rather limited. Specs are: 33kuf @ 100v, 2.5in (64mm) dia, 6"h If you look at what's available, the Nicicons and most others are 3" dia. They will NOT fit! That leaves Rubicon Digikey: Not stocked minimum order of 10. $59.71 each. If someone can find them stocked Please let me know!
I ended up going with the TCI caps from an ebay seller. Very little info on them. They are US made and appear to be very rugged. TCI makes industrial power products and these are apearantly surplus. 2pcs TCI 100V 33000uF Computer Grade 105C Bus Capacitors New | eBay Less than $150 for 4. I took the plunge (out of options at this point) and have been very satisfied. You have to drill out the holes on the buss plate and use larger crimped rings since the screws are HUGE. The improvement in sound is really substantial. Much more linear. Tighter bass, better dynamics, much better on the highs.
Greetings!
I have been rebuilding a PA 7. It has been rewarding but frustrating since the info is scattered about. I am considering starting a PA 7 update page so that we can bring our collective knowledge together. I totally missed this PA 5 page and for a long time didn't have some key information.
Regarding the main cans, I was not completly satisfied with the sound even after recaping the boards with wima, muse, and cerifine caps. The amp still sounded rather closed in with soft bass and poor high end extension.
I have recaped many vintage recievers and have heard many of them sound really sub-par with the old cans. It is amazing what a difference they can make! Sometimes the old ones will reform and sound really good. I am using a HK 930 that sounds great with the origional cans! Often though, they will sound awful at first listen, really dynamicly constipated. Try turning up the volume and it's like running into a wall. Then after a few days the sound really loosens up. It seemed the same thing was going on with the NAK.
Replacement cap options are rather limited. Specs are: 33kuf @ 100v, 2.5in (64mm) dia, 6"h If you look at what's available, the Nicicons and most others are 3" dia. They will NOT fit! That leaves Rubicon Digikey: Not stocked minimum order of 10. $59.71 each. If someone can find them stocked Please let me know!
I ended up going with the TCI caps from an ebay seller. Very little info on them. They are US made and appear to be very rugged. TCI makes industrial power products and these are apearantly surplus. 2pcs TCI 100V 33000uF Computer Grade 105C Bus Capacitors New | eBay Less than $150 for 4. I took the plunge (out of options at this point) and have been very satisfied. You have to drill out the holes on the buss plate and use larger crimped rings since the screws are HUGE. The improvement in sound is really substantial. Much more linear. Tighter bass, better dynamics, much better on the highs.
I wanted to clarify that these are the caps that fit the PA 7. I have no experience with the PA 5.
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