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Old 25th June 2011, 02:22 PM   #11
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Default nak stasis

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Originally Posted by analog_sa View Post
A little knowledge can be dangerous. Do you actually believe the Nak engineers are that stupid?
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]
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Old 15th August 2011, 02:43 AM   #12
nrg2009 is offline nrg2009  United States
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Location: Detroit, born and raised in the netherlands.
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.
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Old 3rd November 2011, 12:02 AM   #13
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So... what is it, that needs to be done, in order to obtain better sound like OP asked!??
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Old 13th March 2013, 05:55 PM   #14
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Default 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?
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Old 15th March 2013, 12:05 AM   #15
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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.
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Old 18th March 2013, 01:00 AM   #16
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Thanks James Brennan. I'm looking into electrical engineers around here which could do this.
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Old 3rd August 2014, 04:00 PM   #17
ci11 is offline ci11  United States
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Quote:
Originally Posted by JamesBrennan4 View Post
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.
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 33,000F PS caps?

Thank you very much.
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Old 22nd August 2014, 03:53 PM   #18
dbear44 is offline dbear44  United States
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Default Nak PA 7 filter cap and bridge

Quote:
Originally Posted by ci11 View Post
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 33,000F PS caps?

Thank you very much.
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.
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Old 22nd August 2014, 08:08 PM   #19
dbear44 is offline dbear44  United States
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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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Old 23rd August 2014, 01:45 PM   #20
dbear44 is offline dbear44  United States
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I am posting all followups on the Nakamichi PA 5 Upgrades page in the Pass Labs forum
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