Restoration and Upgrade of a Late Production C26

[Leestereo]

...and lock in the accuracy of the phono equalization...

Yes, I concur, the accuracy of the RIAA feedback loop is of very important. It is particularly in this application where polyester capacitors should be upgraded to higher performance film types; note that some early production C26 used ceramic and tantalum capacitors in the RIAA (these should be definitely be replaced).


In RIAA equalization, the capacitor has by definition a large signal voltage across it at defined frequencies and Douglas Self has stated that the use of polyester dielectric capacitors in this context "can generate quite large amounts of distortion" (Small Signal Audio Design, p53). AK member @ConradH has an excellent page (http://conradhoffman.com/cap_measurements_100606.html) discussing capacitor distortion and concluded that "polyester (Mylar) ranges from bad to terrible and is to be avoided unless you like the sound".

With ConradH's permission, here are some oscilloscope pictures of his Bridge Residual Test (360Hz, 3rd harmonic residual) for polystyrene, polypropylene and polyester film capacitors with ~3.6Vrms across them
(note that the dominant distortion for film capacitors is the 3rd harmonic). Although, as ConradH specifies on his page, this is not a traditional THD distortion test, it "may have some relation to perceived sound, at least in the case of polyester (Mylar)".

 

[leftside]

Looks like you do great work. I like that you are in Canada, but I wish you were a little closer to us out West

 

[BilboBaggins]

Looks like you do great work. I like that you are in Canada, but I wish you were a little closer to us out West

No way! He's ours!

 

[Leestereo]

... I like that you are in Canada, but I wish you were a little closer to us out West

I sometimes also wish I was closer to the west coast; that feeling is particularly acute in January and February. I do however sometimes get "visitors" from out west, like this Sansui AU-919 from Vancouver: http://audiokarma.org/forums/index....ration-and-upgrade-of-a-sansui-au-919.698011/

 

[Leestereo]

Listening Impressions:

Before starting the restoration/upgrade, the C26 was auditioned for a couple of days; it was compared to a restored/upgraded Hafler DH-110 solid state preamplifier as well as a restored tube Conrad Johnson PV-8 (in two separate systems). Selected tracks from recordings (listed below) that I'm very familiar with were used to evaluate the C26 as received and post restoration/upgrade. Listening notes were kept during these sessions (to avoid relying an imperfect sonic memory).

As received, the C26 had a non-fatiguing, laid back presentation; it exhibited "sins of omission" rather than "sins of commission": there is a lack of detail and dynamics compared to either the Hafler or the CJ. The bass range was warm/full sounding, what some would characterize as somewhat "loose/underdamped" quality; more akin to the CJ than the Hafler in this area. The midrange had a smooth quality, with vocals further back in the soundstage as compared to both the Halfer and the CJ. Similarly, the treble range could be characterized as smooth or soft, but it did not seem particularly extended (i.e., rolled off); both the Hafler and the CJ bettered the C26 in this area. Also, with the C26 there was a noticeable background white noise/hiss at the listening position (particularly with the phono input); the CJ also exhibited this trait, but at lower levels, whereas it was not noticeable with the Hafler. The C26 had a good stereo/spatial presentation, but the CJ produced a wider soundstage with better image depth/height and the Hafler offered a more distinct localization of instruments in the soundstage.

Following the restoration/upgrade, I was able to evaluate the C26 for 5 days before it was returned to its owner. Overall, the sonic presentation of the restored/upgraded C26 was more lively/dynamic than before; improvements were readily noticeable across the audible range. The most obvious change was the reduction in the background white noise/hiss: it is now barely noticeable from the listening position and is typically masked by the noise present in the source recording. An improvement in the sound of the upper midrange and treble range was also evident. Whereas before the restoration/upgrade this area was somewhat "soft" and diffuse, it was now subjectively more extended and natural sounding (e.g., the different percussion timbres are easily discerned in Steely Dan's "Aja" and Brubeck's "Take Five"). In the midrange, the sound of brass, violins/violas and acoustic guitars had more "bite", making them sound much more "real" following the restoration (e.g., Ellington's "Cottontail"; Beethoven Violin Sonatas; Clapton's "Hey Hey", respectively). Vocals were also rendered with improved clarity allowing lyrics to be more easily understood (e.g., Elton John's "Love Lies Bleeding") or just more prominent (e.g., Sarah McLachlan's "I Love You"). The change in the sound of the bass range (<240Hz) was more subtle than that observed in the mid and treble ranges: it too was now subjectively more extended and "tighter" sounding (the 2009 remaster of Beatles "Come Together" sounded particularly good). Another example of such was observed with "Aja", where there were gains in the clarity of the drums and bass. In terms of stereo/spatial presentation, the restored C26 produced a wider soundstage and with improved image depth/height as compared to the stock version (e.g., Böhm/Beethoven symphonies).

Some of the recordings (CD and LP) used during the listening sessions (in no particular order): Lindsey Buckingham/Law and Order; Charlie Watts Quintet/Warm & Tender; Steely Dan/Aja; Miles Davis/Kind of Blue; Eagles/Hell Freezes Over; DMP Big Band/Carved In Stone; Elton John/Goodbye Yellow Brick Road; Jacques Loussier/Plays Bach; Dire Straits/Love Over Gold; Eric Clapton/Unplugged; Beatles/Abbey Road; Sarah McLachlan/Surfacing; Beethoven (Nishizaki and Jando)/Violin Sonatas No.5 and No. 9; Dave Brubeck/Time Out; ECO (Leppard)/Bach Brandenburg Ctos; Duke Ellington Orchestra/Digital Duke; VPO (Böhm, 1972) Beethoven Symphonies no. 6 & no. 9.

 

[c_dk]

Reading your posts caused me to make two Wikipedia searches, Patent medicine and the scientific method, I was curious what the general public's perception is of the definition and lastly the concept.

I do not doubt that those possessing golden ears might hear things that others might miss, what I have a problem with is the patent medicine like advertising claims without exercising any respect for empirical scientific evidence or fact.

Newton created a whole school of scientific thought by observing a apple falling and hearing the thunk as it hit the ground.......Einstein took it to a whole new level, but in either case backed it up with scientifically duplicatable experiments, that, most importantly, exposed discrepancies that opened up whole new areas of questioning and understanding.

Your claims sound like patent medicine advertising and Lumlely like audio claims that defy scientific reason. More reasoned reviewers, those with a more scientific education, have tried to find scientific reasons for what they heard.

How about some scientific testing results, not papers written by a guy justifying his life's work as a capacitor designer.......

As I have posted before I have hosted a A/B/X comparison test between amplifers. My interest in hosting such a event was quite different than the presenter Mr. Clark.

Mr. Clark was interested in proving how much smarter he was than all the audio fools who thought they could hear differences in amp's sound.......I was more interested in what they could hear and why.

I hope the moderators do not pull your advertising like posts, I do also hope you will show some science or experimental data that can be peer reviewed and truly reveal what you claim to be hearing.

 

[Leestereo]

....what I have a problem with is the patent medicine like advertising claims without exercising any respect for empirical scientific evidence or fact.
Newton created a whole school of scientific thought by observing a apple falling and hearing the thunk as it hit the ground.......Einstein took it to a whole new level, but in either case backed it up with scientifically duplicatable experiments, that, most importantly, exposed discrepancies that opened up whole new areas of questioning and understanding.
Your claims sound like patent medicine advertising and Lumlely like audio claims that defy scientific reason...I hope the moderators do not pull your advertising like posts, I do also hope you will show some science or experimental data that can be peer reviewed and truly reveal what you claim to be hearing.

I have tremendous respect for the scientific method and peer reviewed data (see below); however my post was my subjective listening impressions of the C26 and did not claim otherwise.

Recommendations for the Bioanalytical Method Validation of Ligand-binding Assays to Support Pharmacokinetic Assessments of Macromolecules. B. DeSilva, W. Smith, R Weiner, M. Kelley, J. Smolec, B. Lee, M. Khan, R. Tacey, H. Hill and A. Celniker (2003). Pharm. Res. 20(11): 1885-1900,

An Improved Chromogenic Assay For Quantification of Heparin Anti-Factor Xa Activity. B. Lee, S. Tofts, K. Chen, G. Scott and L. Di Donato. (2002). American Association of Pharmaceutical Scientists (AAPS) Annual Meeting and Exposition. Toronto, ON, Canada.

An Improved Chromogenic Assay For Quantification of Heparin Anti-Factor IIa Activity. S. Tofts, B. Lee, K. Chen, G. Scott and L. Di Donato. (2002). American Association of Pharmaceutical Scientists (AAPS) Annual Meeting and Exposition. Toronto, ON, Canada.

A Validation of a Method for the Quantification of Neopterin by ELISA. M. Colarusso, S. Corbeil, B. Lee, S. Tofts, G. Scott and L. Di Donato. (2002). American Association of Pharmaceutical Scientists (AAPS) Annual Meeting and Exposition. Toronto, ON, Canada.

A Validation of a Method for the Quantification of Tumor Necrosis Factor by ELISA. G. Scott, S. Tofts, M. Colarusso, B. Lee and L. Di Donato. (2002). American Association of Pharmaceutical Scientists (AAPS) Annual Meeting and Exposition. Toronto, ON, Canada.

An Improved Chromogenic Assay for Quantification of Anti-Factor Xa Activity in Human Plasma. B. Lee, R. Paulussen, A. Ng, K. Chen, and J.S. Barrett.(1999). American Association of Pharmaceutical Scientists (AAPS) Annual Meeting and Exposition. New Orleans, LA.

Development and Validation of an Electrochemiluminescence (ECL) Immunoassay for the Quantification of RWJ 47428-021 in Rat, Mouse, Rabbit and Monkey Serum Samples. K. Pham, B. Lee, M. Kelley and M. N. Khan. (1997). The Eighth International Symposium on Pharmaceutical and Biomedical Analysis. Orlando, FL.

Quantification of Metroxyprogesterone Acetate in Human Serum: Improvement in the Sensitivity and Selectivity of the Assay by Liquid-Liquid Extraction of Samples. K. Pham, B. Lee, M. N. Khan, C. Brule and N. K. Hopkins. (1997). The Eighth International Symposium on Pharmaceutical and Biomedical Analysis. Orlando, FL.

The Quantification of RWJ 47428-021 in human serum comparison of RIA and electrochemiluminescence (ECL) immunoassays. R. J. A. Paulussen, B. Lee, K. Pham, S. Liao and M. Kelley. (1997). American Association of Pharmaceutical Scientists (AAPS) Annual Meeting and Exposition. Boston, MA.

An Electrochemiluminescence (ECL) Immunoassay for the Quantification of RWJ 47408-021 in Human Serum: Improvement in Sample Throughput and Validation of the Method. K. Pham, B. Lee, M. Kelley and M. N. Khan. (1997). The Eighth International Symposium on Pharmaceutical and Biomedical Analysis. Orlando, FL.

Ultrasonography and Endocrinology of Ovarian Dysfunctions Induced in Heifers with Estradiol Valerate. P.D. Carriere, D. Amaya and B. Lee. (1995). Theriogenology. 43:1061-1076.

Croissance Folliculaire et Ovulations Spontanées Chez Deux Vaches Présentant des Structures Ovariennes Kystiques. P.D. Carriere, D. Harvey, B. Lee and C.A. Price. (1994). Le Médecin Vétérinaire du Québec 24:166-170.

Direct Radioimmunoassay of Progesterone in Bovine Plasma Using Danazol (17-alpha-2,4-pregnadien-20-yno(2,3-d)isoxazol-17-ol) as a Displacing Agent. P.D. Carriere and B. Lee. (1994). Can. J. Vet. Res. 58(3): 230-3.

 

[c_dk]

I would be much more impressed with some screen shots of the before and after affects of your time consuming, therefore expensive, modifications or updates of this budget Mac preamp.......

As my sons have told me as they have advanced their education, earning a PHD is all about teaching the candidate how to think through the problem, to establish the methods to prove or disprove the thesis.....it appears you have received similar discipline.....

So to quote a old paradigm of the advertising industry......."Where's the beef?"

 

[Hipocrates]

I would be much more impressed with some screen shots of the before and after affects of your time consuming, therefore expensive, modifications or updates of this budget Mac preamp

All due respect... Get over it, the involved parts think that ''this budget Mac" worth the time and effort to improve and are very happy with the results. You disagree? Irrelevant.
Ben write ups are great and some (include me) took them as guide to improve our units with happy endings, just take a look on the Marantz, Sansui and Pioneer forums. Of course, been a bunch of enthusiasts and hobbyist, I don't think that many will be able to ''impress you" with numbers and cold data (which probably you won't accept anyway).
The good thing is that the write ups are there for anyone to grab, just in case you want to dispute the results that some of us happily claims, if you want to.

 

[BilboBaggins]

Wow!

What ever happened to all audio, no attitude?

I don't have a phd, an ma, or a ba, and frankly I don't need one to know what I like. Bonus is that the people who I care about also seem to hear similarly to me, so we can enjoy similar things. I read specifications that look impressive, but that means very little. I also read about how great certain audio gear is and when I got it home and heard it for myself, I was quite disappointed. In fact, I really don't think we know what to measure in order to objectively tell someone if something sounds good or not. So I'm really not interested in graphs or distortion measurements, and while measurements tell me a little bit about what is going on and helps me to match it, it really means nothing in the end. As has been said many times here on AK, go and hear it for yourself and make up your own mind. I will give certain members opinions more weight than others, but that is because I have had the same impressions as they have when talking about certain gear.

I don't think Leestereo needs to drum up any business. His queue is quite full and about 4 months deep. And he does this work as a hobby. The fact he gets some money for it is just a bonus. We have talked together for many hours about audio. He has a similar philosophy as I have in terms of how he enjoys audio and the process of restoring and improving on vintage gear in a good way. He is very analytical and does things for a reason, otherwise, he leaves it alone. His rates are very reasonable in my eyes, and he gives excellent value for the money.

Frankly, I'm very surprised at how few comments there have been on this thread. He has done a superb job at this restoration. Maybe everyone is on vacation? I don't know. I just don't get it. This is the first time I've had my C26 called a budget preamp, but I guess in relation to many other McIntosh preamps, it is a budget preamp. In the real world, it is called a real beauty. Who would have thunk?

 

[c_dk]

Some of us do try to document our work other than engaging in theurgy and the sometimes overwhelming mysticism of "high end audio".

Three screen shots of a C26 via the aux input path before, partway thru and final recap of the power supply and electrolytics on the preamp boards. The first screen shot does not have a 1000 Hz marker to establish 0dB as a reference.



So it is possible to establish some discipline of the "scientific method" to updating vintage hifi equipment you just need to take the time and show the intellectual curiosity to ask "Why, why does this sound different?" Better will come out in the wash later......

 

[Hipocrates]

Some of us do try to document our work other than engaging in theurgy and the sometimes overwhelming mysticism of "high end audio".

That's cool, now you can upgrade the rest of caps and show us the result!

 

[c_dk]

Being a skeptic is a healthy additude often in the world of audio.

I have been documenting those areas of audio that have the greatest areas of error, turntable setup and calibration as well as speaker/ room interactions for 4 decades.

The minutia of tenths of thousands of capacitor distortion differences raise my skeptic antenna, especially with the known inaccuracies of human hearing. I do assume something is happening however.....

Having set up pairs of before and after comparisons for locals of 2 C33s, 2 MAC4100s, 2 MC2100s as well as a before/after C30 with a done C35; I am well aware of the sonic differences possible between a stock 25 year old++ unit and a restored one.

My question is why? What is being heard and why are you hearing it.

How do you create a stereo sound image? What pyscho acoustic buttons do you have to push and how much to achieve such euphoric results? Are we talking spectral frequency response aberrations, or phase changes, or both, or more? Are these changes by accident or on purpose?

These are important questions and should intrigue those with a true scientific bent.

 

[Hipocrates]

The minutia of tenths of thousands of capacitor distortion differences raise my skeptic antenna, especially with the known inaccuracies of human hearing. I do assume something is happening however.....
Having set up pairs of before and after comparisons for locals of 2 C33s, 2 MAC4100s, 2 MC2100s as well as a before/after C30 with a done C35; I am well aware of the sonic differences possible between a stock 25 year old++ unit and a restored one.
My question is why? What is being heard and why are you hearing it.
How do you create a stereo sound image? What pyscho acoustic buttons do you have to push and how much to achieve such euphoric results? Are we talking spectral frequency response aberrations, or phase changes, or both, or more? Are these changes by accident or on purpose?
These are important questions and should intrigue those with a true scientific bent.

Fair enough, and you have the knowledge and tools to investigate, replicate, corroborate, and verify whatever information you want.

For some of us.... just want to play a record and enjoy whatever unit is without worries and relax. Does not matter if is a ''budget Mac" a humble HK330B, a nice Western Electric or whatever piece of gear we can possibly own, and that's where info & work like leestereo and others provide is priceless IME.

The technical specifics are for someone else, some have enough stuff to deal with at work, and if someone like Conradh, leestereo and others share their findings and experiences, I tested and works... is good enough for me and I (and others) are appreciative to their point of view, why a C0g is better than Mylar? How the dielectric interacts and low distortion... Well, honestly don't care, I'd probably invest more time that I have trying to understand it and we just want the unit working and sounding nicely.

Remember this, for some of us is just a nice hobby and people have the prerogative to spend whatever resources they want without someone trying to disqualify ''ad portas" whatever information they are kind enough to share.

 

[Overundr1]

Until I acquire a good spectrum analyser (the only piece of test gear missing off an otherwise complete bench testing array) I rely on empirical findings from those that have invested in one, the St1701a distortion analyser in use now will not pull in the weeds harmonic data rather gives overall results. Instead I rely on findings posted by other techs that have both the time and inclination to pursue this performance modifier area of the hobby
Come to think of it, I am only able to test up to 200w output due to dummy load limitation, how do the MC techs verify rated output on the big output pieces reliably?
-Lee

 

[damacman]

Actually a lot of valuable information in this thread - both from Leestereo and c_dk. I've enjoyed the professional volleying and exchange.

Somewhere between their positions lies the answer we all seek.

 

[Archguy]

80 plus parts would put this type of rebuild beyond the budget of most everyone not a DIYer

Yes and no. Doubtless it would be costly. OTOH, this documentation probably doubled the value of the component.

I just wish there were expertise like this in my neck of the woods. Having 'varied' luck with shipping lately.

 

[c_dk]

I am not being facetious......I do really hope this can be proven empirically and easily demonstrated to all who wish to listen to a practical A/B comparison.

I believe it would truly revitalize the brick and motor audio business........

Imagine 120 or so full service department equipped audio demonstrating dealers in the top 75 American metro areas.

The ability to generate a multicolor computer generated report card showing the unrestored units failing to meet what is now the expected performance characteristics and the ability to upgrade this classic unit to met these modern norms....

A quick survey through Berner's site showed that just hitting the top notes Mac made over 120,000 amplifiers before the MC2255 was introduced in 1982. I am sure there is a like number of preamps from the stereo years.

Can you imagine a 1000 plus units showing up for restoration at these 120 brick and motor locations. Dealers would actually need to employ and train local service people, lead times for warranty work would shorten and audio people would be visiting showrooms to actually listen to the improvements available......and I am not even counting other brands that might warrant similar treatment.

I was there when David was pre mourning the ending of his beloved clinic program.....sat and listened to his "hurt" as dealers began to reject "his" program.

Instead of a Power Guard snap shot of what could only be heard at near ear bleeding volume levels these restorations should be audible at common volume levels, that all, even the greatest skeptic could hear.

I believe most of this capacitor upgrade concept is a result of Jung's and Marsh's rejected AES peer review paper based on a oral presentation they made to a AES group in 1977. That paper was printed in 1980 by Audio magazine but never went through the traditional electrical engineering peer review process.

I have no idea why the editors of the AES rejected the paper but it might have been a great shame.

I hope today, with possibly better computer based time domain sensitive testing equipment the concept, I believe they called it Slew Induced Distortion, might be further explored.......it will need a new acronym though......

http://www.waltjung.org/PDFs/Picking_Capacitors_1.pdf

http://www.waltjung.org/PDFs/Picking_Capacitors_2.pdf

 

[Overundr1]

I believe it would truly revitalize the brick and motor audio business........

Imagine 120 or so full service department equipped audio demonstrating dealers in the top 75 American metro areas.

Rebirth of an industry led by a U.S. manufacturer would be outstanding to experience sir. One does wonder given the dearth of audio engineering disciplines being taught today how a network of retail locations would find and retain quality service personnel. Very few point to point training board level troubleshooting and interpretive skill sets out there anymore.

-Lee

 

[c_dk]

The industry is not dead but it has been sidetracked into low profit television and hands on installation.

If you supplied enough folding pieces of paper with the vestige of a former postmaster general on it people would be found and trained.

If a few dozen McIntosh owners would show up at their local Mac dealers demanding this profitable restoration service monthly the dealers would find a way. Warranty service pays peanuts but 3-5 labor rate variable $350 to $500 restorations a week will get dealer attention. Plus the floor traffic added would be a boost for sales in general. Add Gordon Gow's favorite, turntable setup and calibration, and it's ability to attract the youths new found interest in vinyl, it could certainly be a industry shot in the arm.

AK is full of oral testimonies of vast improvements members have achieved by restoring their vintage audio equipment, myself included.

McIntosh as a ongoing concern going back to those seminal years is best positioned to again advance the industry.

I truly applaud the OPs effort to advance the state of restoration but without empirical documentation the concept of restoration will be but a passing fad I am afraid.