Sony CDP790 and KSS240 Restoration Project

Have a pair of LME49990s on an adapter which I installed in the output stage of my CDP-X111ES along with the ADA4627-1s, giving a bit of improvement in clarity over the OPA211s (LME49990s used for final buffer, ADA4627-1s in differential amplification stage).

My old CDP-65 had a power switch which cut power right at the mains; off was totally disconnected from the wall. However, the power switch on the X111ES is on the low voltage side, meaning that the unit is always drawing power, even when off; I measured 4W with my EM100 Energy Meter, which is a significant amount of vampire power. Given that the unit has no power on by remote function and no apparent stand-by mode, does anyone know why Sony employed such an energy inefficient wiring scheme for the power switch, other than to save a little money on manufacturing costs?
 
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In the UK 4 watts over a year would typically cost around £6.00

As with everything, manufacturers employed standby switching rather than true on/off function on the grounds of cost. The safety requirements will be far more relaxed for low voltage circuitry and case work that can not contact live mains.

You might find a simple power monitor is less than accurate at very low current draws and also may not account very accurately for the poor power factor of an inductive load such as a very lightly loaded transformer.
 
I have found that AC power monitors are typically quite inaccurate at very low power draw.

Looking at the PSU I would be surprised if that draws more than 0.5W in standby.

Also - unless you've already modded the muting circuit, I would remove the various transistors (as highlighted in the attached schematic) and replace them with a relay. Additionally, the combination of resistors (required for the transistor muting circuit) push the output impedance up to around 1k ohm which is rather high.

So in addition to a muting relay, I would bypass the 220 ohm resistors, and then change the 560 ohm to 56 ohm.

Finally, the original NE5532 output OPAMPs are more than adequate for this application, and I suggest you try blind tests to verify you really are hearing differences when substituting those expensive OPAMPS...
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Also - unless you've already modded the muting circuit, I would remove the various transistors (as highlighted in the attached schematic) and replace them with a relay. Additionally, the combination of resistors (required for the transistor muting circuit) push the output impedance up to around 1k ohm which is rather high.

So in addition to a muting relay, I would bypass the 220 ohm resistors, and then change the 560 ohm to 56 ohm.

Finally, the original NE5532 output OPAMPs are more than adequate for this application, and I suggest you try blind tests to verify you really are hearing differences when substituting those expensive OPAMPS...

Hi, audio_tony,

What sort of difference should be expected from removing the muting transistors? I've seen this mentioned before, but haven't attempted it yet. What would you suggest for a muting relay, and how would it be wired in?

As for the op amps, over the years, I've spent many hours auditioning various op amps, swapping back and forth to ensure I'm reliably hearing what I think I'm hearing. Usually, the differences are fairly subtle, but they're there.... I've been a musician for decades and have mixed a few projects, so I have pretty good ears and am able to pick out subtle difference that most people would miss. I'm also well aware of various forms of cognitive and perceptual biases, so I make a concerted effort to double/triple/quadruple check what I'm hearing. Sometimes an expected improvement isn't there, so I know it isn't just a matter of confirmation bias.

The ADA4627-1 and LME49990 are the best sounding op amps I've found thus far and I don't have another use for them at the moment. FWIW, I'd say that the ADA4627-1 is a bit more euphonic sounding, with a nice warmth, yet still quite open, whilst the LME49990 might be characterized as more transparent, without much obvious color. I quite like the tonality of the ADA4627-1. Both are better than an NE5532, and much better than the TL082 that was in the differential stage.
 
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These kind of mute transistors are rather unique in that they will operate (at low voltages anyway) without regard to C-E polarity. They have 'gain' with either polarity configuration... so never swap them for ordinary small signal types as they won't work as well.

What to do as an alternative? Well years ago I came across this thread (look at post #9 and onward) and can confirm that using suitable JFET's as a direct replacement works well in most cases.

Marantz SA8001 Modification to Eliminate Distortion
 
When one reads Self's research on muting transistors (even FETs) one wonders why anyone would bother with them.

I would only ever use a relay.

@Mooly - the transistors used for the actual muting are standard 2SCxxxx types. They in turn are switched by those special transistors with built in resistors.

That they have used three transistors per channel with appropriate limiting resistors suggests they had issues getting the mute silent enough. A relay would likely have been cheaper!

@12Bass If you're not sure how to bypass the muting circuit and fit a relay then perhaps this is not the task for you.

But in basic terms, the muting is controlled by Q341, Q342, Q343.

You only need to make use of one of those - and use it to drive a another transistor (pref. darlington) to switch the relay, which you would place in series with the output. You could also place it in parallel, but then you would need to retain the series resistors which would defeat the object to some degree.

You need a low output impedance here.

The current high(ish) output impedance might be why you are hearing differences between opamps (depending on the capacitance of your interconnect as well).
 
FWIW, if I were to make such a modification, I'd likely go with a relay rather than FETs, as that seems to be the least likely to introduce any distortion into the signal. That said, CD players like the X111ES already have vanishingly low distortion, so I'm not sure how much there is to be gained by such a modification, though I have found that changes to the analog output stage seem to make the largest difference in my experience. Still, I'm curious to read what Self found in his research, so a link would be appreciated. A simple way to find out would be to temporarily bypass the muting transistors and see if the difference is audible. I understand the basics of wiring up a relay but am unsure of the potential benefit and tend toward the maxim of "if it ain't broke, don't fix it"... as I've damaged various devices in the past with questionable modifications, and the player is sounding subjectively pretty good at the moment.

The op amp discussion is somewhat of a side topic... however, I've reliably heard differences between op amps in all kinds of circuits, and have tried, many, many different parts... which is what has led me to the ADA4627-1 and LME49990, which are the best of the bunch that I've tried. Others that I've auditioned include: LM4562, AD825, OPA275, OPA2604, OPA2132, OPA2134, OPA211/2211, OPA1612, OPA1642, OPA2107, OPA249, NE5532, LM6171, TL072, AD797, OPA827, and several more....
 
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@Mooly - the transistors used for the actual muting are standard 2SCxxxx types. They in turn are switched by those special transistors with built in resistors.

The transistors used in the CDP790 are these which were rather special (although common enough in this type of application):

Muting Transistors



They have a high hFE of around 150 when reverse biased at -2 volts.

It looks like the ones in audio_tony's player are more general purpose devices.
 

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Listening trials revealed what I would describe as a typically bright and somewhat "thin" sounding player. It was up against stiff competition though in the form of my old Micromega Stage 2 and the Stages' successor, a Marantz Pearl-Lite SA-CD.

... The Sony "Pulse" dacs, which are indeed their version of bitstream(could even be relabeled chips from Crystal Semi or etc.) sounded uniformly weak-bass'd and overall thin, but did get better by the time the CDP-XA7ES & later top models came out. Still prefer ladder dac Sony's by far, myself, versus their 1bit units, although players like the DVP-S9000ES can be made to sound really, really good with upgrading. The dac used in that 790 is not in that league, though.

After modifying my CDP-X111ES, I've come to a strong opinion that (generally speaking) the analog stage is most responsible for holding back the sound potential of a DAC, and not the DAC chip (CXD2552 in this particular case). I say this in part because I have compared my modded X111ES with newer DACs that use AK4393 (modded Echo Gina24) and AK4620B (modded TC Impact Twin), both with ADA4627-1s in output stages, and the modded Sony CXD2552 DAC sounds subjectively better to me, though that may be in part due to other aspects of the analog section in each unit.

When a friend was over recently, we briefly A/Bed the modded X111ES with my unmodded Luxman DZ-112 (PCM1701P, one of the "best" R-2R DACs) through my Rotel RB-870BX and Energy Reference 22 speakers (each CD player direct into power amp via variable output, no preamp used), and the Luxman was noticeably less detailed and resolving, though it had a sort of "smooth" character that I liked. We both preferred the modded X111ES.

Yesterday I replaced the LME49990s in the output stage of my CDP-X111ES with a pair of ADA4627-1s, making it ADA4627-1 in both differential and output buffer stages. Although the LME49990 is an extremely low distortion op amp, it still seems to retain some of the "cold" thinness of chips like the LM4562/LME49710, though with plenty of detail.

I was amazed at how much better it sounded with ADA4627-1s! Still lots of detail, but bass, dynamics, and especially midrange to die for, just very musical to my ears. I spent several hours listening to the player with my K702s, enjoying every moment. With the LME49990s, I liked how it sounded, notably the clarity and detail, but it wasn't as engaging and sounded a tad "cold and analytical" and was more fatiguing over longer listening sessions. I'm not sure if the ADA4627-1 is transparent (i.e. like a piece of wire with gain) or colored, but it sure sounds excellent to me. I didn't expect that replacing LME49990s with ADA4627-1s would make such a difference, but it was subjectively huge. And the original TLO82/NE5532 op amps are nowhere near as good as the LME49990.

Switching to 1000µF (instead of stock 47µF) in the output coupling capacitors eliminated the thinness in the lows noted above, and adding a pair of 1µF polyester and 0.01µF polypropylenes brought out more treble and midrange clarity. At this point, I would love to A/B the modded X111ES with a variety of high end DACs and see if they sound noticeably better.

Additionally, a couple months on, the X111ES transport started to have issues with skipping and eventually failing to read and displaying "No Disc", usually toward the end of the disc, perhaps past the 50 minute mark. Some lubrication of the pickup assembly seems to have remedied this issue. Seems like there were some sections where there was no grease on the gears, making it difficult for the motor to overcome the load toward the end of a lengthy disc, causing the transport and disc to stop moving.
 
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There is certainly plenty of scope for tweaking and experimentation in the analogue stages of players like these.

One of my favourite opamps from some years ago was the old OPA604/2604 which to me suitable fits your descriptive line of:

I'm not sure if the ADA4627-1 is transparent (i.e. like a piece of wire with gain) or colored, but it sure sounds excellent to me.

That is how the OPA's always came across to me.

Sometimes things just seem to work well together, better than the sum of their parts.
 
There is certainly plenty of scope for tweaking and experimentation in the analogue stages of players like these.

One of my favourite opamps from some years ago was the old OPA604/2604 which to me suitable fits your descriptive line of:

That is how the OPA's always came across to me.

Sometimes things just seem to work well together, better than the sum of their parts.

Guessing you're talking about the OPA604/2604 here? I've tried it in a few applications, but it has been surpassed sonically by a variety of newer chips, IME (e.g. OPA827, OPA1642, ADA4627-1). Testing I've seen showed that the OPA2604 is also quite dirty, producing a surprising amount of distortion. However, it does allow much higher voltage rails than many others, which can make it suitable for circuits where others are voltage limited. Thus, it has been used in certain pro audio application with high voltage rails.

OPA2604 results on page 388: https://www.nanovolt.ch/resources/ic_opamps/pdf/opamp_distortion.pdf

I realize that it is somewhat expensive, but I'd suggest anyone interested in sound quality give ADA4627-1 a listen, as it definitely sounds a notch above other op amps in my experience, though some claim that discrete modules are even better (which I've yet to try).

At some point I'd like to mod the analog stage in the DZ-112 and see if it is able to surpass the X111ES. Perhaps those PCM1701P R-2R DACs really are better but are being held back by the output section? Unfortunately, the DZ-112's transport needs calibration, or perhaps a new laser, making it a bit more of a project than I'm willing to take on at the moment.
 
Electronics Today Magazine, October 1990, has some technical details and measurements for the CXD1244/CXD2552 Sony Pulse DAC: https://www.americanradiohistory.com/Archive-Electronics-Today/90s/Electronics-Today-1990-10.pdf

Any suggestions for +/-8 or 9V LDO regulators for the analog output stage?

Although I haven't looked extensively, the CXD2552 and later Sony DACs seem to do well in review test measurements. I'm wondering how much of the notion that R-2R DACs are superior is similar to the claim that vinyl is superior, as in based on some sort of sentimental idea that old technology was better? In the case of R-2R DACs, the underlying principle certainly seems easier to understand than 1-bit, as is the basic technology used for playing a vinyl record versus the LSI circuit complexity required for CD playback. But simplicity or ease of comprehensibility are by no means a good way to judge the objective superiority of one piece of technology over another.
 
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Hi 12Bass,
Switching to 1000µF (instead of stock 47µF) in the output coupling capacitors eliminated the thinness in the lows noted above, and adding a pair of 1µF polyester and 0.01µF polypropylenes brought out more treble and midrange clarity.
Expectation bias is at work here. The larger capacitors did not extend the range of the output in the audible range at all. Bypassing the larger electrolytic likewise didn't do anything to help you either. I'm sorry, but it's true.

Basically, if it makes you feel better, then fine. Just don't encourage others to mess up their machines like this. Your capacitors don't fit where the originals did and you stand to pop the pads and traces off the PCB - if you haven't already.

Some op amp changes can make a difference in the sound of an analogue stage. But again, I think there is more expectation bias going on here than is factual. Again, if it makes you happy - great. Just as long as your soldering skills are up to the level required so you don't damage the circuit board.

Why do I care? Because I still repair this equipment and I'm pretty tired fixing the problems, or having to tell a customer the CD Player he just bought is a write-off due to someone else's "work". Without some knowledge and common sense, people are apt to do all kinds of things to their equipment.

Now, if you value your CD player, have an experienced technician look at it to correct your skipping problem. You can get an amazing improvement in sound quality (for real) by having the machine properly adjusted and cleaned / lubricated. That's because although it appears to track and not skip, the error rate will be greatly increased due to any type of transport problem that affects reading the CD. Believe it or not, real audio technicians with experience are highly trained and have the proper test equipment to do a far better job than someone without formal training and service experience. No matter how good you think you are and who's advice you follow on the internet.

Not trying to rain on your parade, but there should be a reality check now and again.

-Chris
 
Hi 12Bass,

Expectation bias is at work here. The larger capacitors did not extend the range of the output in the audible range at all. Bypassing the larger electrolytic likewise didn't do anything to help you either. I'm sorry, but it's true.

Basically, if it makes you feel better, then fine. Just don't encourage others to mess up their machines like this. Your capacitors don't fit where the originals did and you stand to pop the pads and traces off the PCB - if you haven't already.

Some op amp changes can make a difference in the sound of an analogue stage. But again, I think there is more expectation bias going on here than is factual. Again, if it makes you happy - great. Just as long as your soldering skills are up to the level required so you don't damage the circuit board.

Why do I care? Because I still repair this equipment and I'm pretty tired fixing the problems, or having to tell a customer the CD Player he just bought is a write-off due to someone else's "work". Without some knowledge and common sense, people are apt to do all kinds of things to their equipment.

Now, if you value your CD player, have an experienced technician look at it to correct your skipping problem. You can get an amazing improvement in sound quality (for real) by having the machine properly adjusted and cleaned / lubricated. That's because although it appears to track and not skip, the error rate will be greatly increased due to any type of transport problem that affects reading the CD. Believe it or not, real audio technicians with experience are highly trained and have the proper test equipment to do a far better job than someone without formal training and service experience. No matter how good you think you are and who's advice you follow on the internet.

Not trying to rain on your parade, but there should be a reality check now and again.

-Chris

Hi Chris,

Perhaps this won't come across as intended, and I'm sure you mean well, but I think you're off base here.

I have an MA in philosophy, with several undergraduate classes in physics and psychology, including sensation and perception, neuroscience, etc..., and I'm quite familiar with the literature of cognitive bias and how to recognize it. I also have a particular interest in epistemology and the philosophy of science and am a staunch advocate of the scientific method. Snake oil holds no interest to me.

I have no intention to sell my X111ES. I paid $20 for it and it has over double that in ADA4627-1s. I modified it for my own enjoyment, so that it sounds as good as possible. Nor was I suggesting that anyone make the same modifications I have.

However, when I made the various modifications, I took a fairly scientific approach. I spent many hours critically auditioning and comparing the various parts.

With the coupling capacitors, I spent hours trying various combinations, with varying expectations. For example, I tried using 0.1µF polypropylenes and found that it made the sound somewhat more harsh in the treble. I did not expect this. However, switching to 0.01µF polypropylenes made an immediately audible improvement. I went through a similar process with the electrolytics. For one, I figured that 1000µF must be total overkill, so I tried 220µF, fully expecting that it would be more than sufficient, or possibly even better. But 220µF sounded noticeably worse, despite the fact that I expected it to sound the same or even better. In other words, these values were determined through hours of focused critical listening, and trial and error, with some steps forward, and some steps back, and are not the result of some sort of blind expectation and/or confirmation bias after soldering in random parts because I have no clue what I'm doing.

FWIW, over the years making modifications, I've quite easily heard an audible improvement after adding polypropylene bypass capacitors where electrolytics are employed for AC coupling. It's not something I would describe as subtle. I generally critically listen with my K702 headphones which are quite revealing of such details.

Similarly, I expected that the LME49990s must sound excellent, and at least as good as the ADA4627-1s. Yet, when I replaced the LME49990s with ADA4627-1s, the sound immediately improved. I didn't want it to. I was just trying the ADA4627-1s in the buffer stage as an experiment to see if it sounded different. Yes, it did... and subjectively much better. And now I have a bass amp missing its input op amps, which sucks.

Also, I've been a musician for decades and have recorded and mixed various music projects, so I have a better understanding of sound and how to listen critically than average. I'm able to more reliably identify nuances in sound, plus I've always been a very discerning person by nature.

In an earlier post I mentioned that I fixed the skipping problem by lubricating the transport. It plays fine now.
 
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Expectation bias is at work here. The larger capacitors did not extend the range of the output in the audible range at all. Bypassing the larger electrolytic likewise didn't do anything to help you either. I'm sorry, but it's true.

Basically, if it makes you feel better, then fine. Just don't encourage others to mess up their machines like this. Your capacitors don't fit where the originals did and you stand to pop the pads and traces off the PCB - if you haven't already.

Some op amp changes can make a difference in the sound of an analogue stage. But again, I think there is more expectation bias going on here than is factual. Again, if it makes you happy - great. Just as long as your soldering skills are up to the level required so you don't damage the circuit board.

Why do I care? Because I still repair this equipment and I'm pretty tired fixing the problems, or having to tell a customer the CD Player he just bought is a write-off due to someone else's "work". Without some knowledge and common sense, people are apt to do all kinds of things to their equipment.
If we're going to discuss cognitive bias, it should be mentioned that there is clear evidence of motivated reasoning in the above post. Further, I'd like to know what qualifications you have in psychology that give you the authority to make such a diagnosis? What is evident is someone who has a bias against people who tinker with their own electronic equipment, perhaps due to frustration in having to repair others' "improvements". I understand why someone might feel that way, but that bias gets in the way of objectively pursuing and assessing the truth of this particular situation and it is not at all helpful.

As a philosopher, I care very deeply about the truth and sound doxastic methodology. I am aware of a large variety of cognitive and perceptual biases and, though I must admit that as a human I am susceptible, I do my best to recognize and mitigate their effects. That's why I spend hours critical listening and testing, making comparisons. More often than you seem to assume, I have found that my expectations were thwarted, that a particular modification or component substitution was a step backward. I refuse to allow myself to believe that any change I might make is automatically beneficial, because a great deal of experience has told me otherwise. If a given change sounds subjectively worse, I simply accept it, and step back, or try another approach.

Further, doxastic voluntarism is an epistemic view which I find highly troubling, perhaps incoherent. I cannot, and will not, believe something to be true simply because I want it to be true. If I have come to certain conclusions through my various experimental modifications, it is not because I "wanted to believe", but because I have done many, many, experiments, and that's what the evidence has led me to believe.

If you, or anyone else, wants to subject my X111ES to an extensive battery of tests with an Audio Precision APx555 B, I'm all for it. I would love to see some objective data showing how my modified X111ES compares with a stock unit, and if what I hear subjectively can be correlated with the measurements. I'm also open to group ABX testing if anyone happens to have another unmodified X111ES. That would be an interesting excercise, and one which could potentially falsify my claims that I can hear significant differences.

I have been building and modifying electronic circuits for four decades and have a decent grasp of basic electronics (and mechanics, I've also rebuilt ICEs), so it not as if I have no clue what I'm doing or why I'm doing it. And, finally, this is diyAudio, where people ought to be encouraged to DIY, which is exactly what I intend to continue doing, with the gracious assistance of the people on this forum.
 
... Switching to 1000µF (instead of stock 47µF) in the output coupling capacitors eliminated the thinness in the lows noted above, and adding a pair of 1µF polyester and 0.01µF polypropylenes brought out more treble and midrange clarity.
Wanted to elaborate on this...

With regard to the output AC coupling capacitors, I settled on 1000µF, a pair of 1µF polyester films and 0.01µF polypropylenes, all determined through careful listening and trial and error using my K702s and Energy Reference 22s (I am also open to reevaluating this if/when I get more capacitors to play with). As mentioned previously, I tried reducing the electroytics to 220µF and the subterranean lows seemed to be affected, even though I figured that, on paper, 220µF should be far more than sufficient within the audio passband. 47µF sounded thin, no matter what the combination of film bypass caps.

I also tried removing the 1µF polyester caps, under the notion that bypassing makes no difference in the midrange (and that confirmation bias was confounding my results); however, that resulted in a subtle but audible hole in the midrange. My expectation was that the 0.01µF polypropylenes were sufficient, and that the 1µF polyesters were superfluous, but that was not borne out under critical evaluation, and the sound improved once I resoldered the 1µF caps. I'd rather not use extra capacitors and would gladly remove them if doing so made no difference to the sound.

In short, I arrived at those particular values through very careful critical listening using a process of trial and error, during which my expectations were often thwarted. What I wanted to sound "better" often did not, so I kept trying different values until the sound was closer to what I wanted to hear. Thus, this is obviously not a clear case of expectation or confirmation bias.

Some time ago I came across a link which showed the differences in signal transfer between the various dielectric materials used for capacitor construction. Electrolytics were among the very worst, with fairly high distortion; however, I'm unable to find it at the moment. Given my experience, I'm going to guess that anyone who says that bypassing electrolytic AC coupling capacitors makes absolutely no difference to the sound either a) has not tried it, b) has not used bypass capacitors with appropriate dielectric/values, c) does not have monitoring equipment which is sufficient for resolving the differences, or perhaps d) lacks the critical listening skills necessary to hear the differences.

I'll also add that schematics readily show that Sony and many other audio manufacturers routinely add film bypass capacitors to AC coupling electrolytics. Perhaps they merely do this for show. However, unless they advertising this fact for "audiophools", maybe they are actually included because Sony engineers found that they make a real difference to the sound. Otherwise, Sony and others are simply wasting money by adding useless components which they even don't mention in the marketing literature, which would make very little sense because they are cutting into their own profit for no sound technical or financial reason.

Note that my K702s reproduce 30Hz fundamentals better than most headphones (as do my Reference 22s, which are rated down to 28Hz), that I'm a bassist who appreciates deep fundamentals, and that the improved depth in the low end from using larger bypass capacitors may not be readily apparent through transducers which are unable to reproduce the bottom octave.
 
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Hi 12Bass,
I have the best of intentions here, and I am well positioned to make the statements regarding your attempts to improve the sound quality of your equipment. I do applaud the efforts you have made, but you haven't had the benefit of proper instrumentation and training to guide your choices. It is unfortunate because you are trying to do the best you can with the information at your disposal. I feel that most of the information you have may have been gleaned from posts on the internet and a couple of web sites I won't mention where they are truly misguided. Reading whitepapers, if you have, also can seriously misguide your intentions.

I do not have an AP anything, but what I do have is an RTX 6001 which is more than good enough to show advantages and miscues on upgrading equipment to the point where I can normally predict how that piece of equipment will be reviewed.

The rest of my test bench consists of mostly Hewlett Packard / Agilent / Keysight equipment with a few other brands thrown in for specialized test equipment that my preferred vendor does not produce. For spectrum / network analyzers, I use the following (Keysight or its predecessors): 3580A, 35665A, 3585A, 4195A. Oscilloscopes include an Agilent 54642D and a Tektronix 2465B CT. DVMs from Keysight or its predecessors: 3465A, 3457A, 34401A, 34465A. Reactance measuring HP 4263A and ESI VideoBridge 2150 plus some older Tektronix and Genrad gear. For distortion analysers I still use my HP 339A and 334A, along with the RTX-6000 with Virtins M.I. and ARTA (Both paid for). I even have an HP 5372A for time/jitter/Allan Deviation measurements, a 5335A Universal Counter (a frequency counter that does math and statistics) and the entire bench is synced to a common 10 MHz frequency source locked to the GPS network with two backup GPS receivers, distributed by an HP 5087A Distribution Amplifier. It's nice when all the numbers agree exactly. :) There is a ton of other equipment and custom made jigs and instruments. That's a lot of stuff and you don't want to know what it costs.

Okay, so that is a list of the primary instruments that are used, along with current sources and power supplies that are used for equipment upgrades that I have been doing for over 35 years. I have been a professional technician for over 40 years and also have a formal education in addition to specific trade training. I'm reasonably well known for CD service (along with all other audio equipment). I'm also an old fart.

-Chris