Hi. Looking to upgrade the caps in the signal line of a Conrad Johnson PV5. Thinking of combining C29/30, C22/23 into a 5uF each, and replacing C20, 25, 26. Any other caps look like good prospects for an upgrade, or are any of the ones mentioned unnecessary?
What brands/types of cap would be desirable in this application? Been looking into Auricaps and Dynamics, and Janztens.
The preamp is used with a Sun Audio SV-2A3 (mods: removed 1st bypass cap, electrolytics replaced w/ film, GE/Ultrapath).
Thank you for looking!
-Gabe
What brands/types of cap would be desirable in this application? Been looking into Auricaps and Dynamics, and Janztens.
The preamp is used with a Sun Audio SV-2A3 (mods: removed 1st bypass cap, electrolytics replaced w/ film, GE/Ultrapath).
Thank you for looking!
-Gabe
For coupling caps, I'd use SoniCap Platinums by themselves if you can afflord it (IYCAI) or combinations of MultiCap RTXs and Platinums for the section-output caps. For PS-bypass caps, Platinums and Jupiter HTs.
In the PS, replace at least C3 with BlackGates IYCAI or maybe a Solen 400VDC 'propylene.
Said another way, replace ALL the original film-type coupling and PS-bypass caps, and repalce as many of the high-Voltage 'lytics as you can afford.
I've got pics of a PV5 rebuild I did many years ago; e-mail me at jeffreybehr(at)cox(dot)net and I'll send 'em, as long as you realize I wouldn't do it again that way.
Here's one.
Quite visible are the Solen replacements of the HV 'lytics.
In the PS, replace at least C3 with BlackGates IYCAI or maybe a Solen 400VDC 'propylene.
Said another way, replace ALL the original film-type coupling and PS-bypass caps, and repalce as many of the high-Voltage 'lytics as you can afford.
I've got pics of a PV5 rebuild I did many years ago; e-mail me at jeffreybehr(at)cox(dot)net and I'll send 'em, as long as you realize I wouldn't do it again that way.
Here's one.
An externally hosted image should be here but it was not working when we last tested it.
Quite visible are the Solen replacements of the HV 'lytics.
I would not recommend replacing any of the capacitors in the phone stage. Unless you have a reverse RIAA network and plan to frequency sweep the stage afterwards. For which you'll need an audio generator with a flat output and the reverse RIAA network must match the characteristic output impedance of the generator to maintain accuracy. Usually 50 or 600 ohms. Even if you use the exact same value caps, changing the dielectric will affect the response curve to some small degree. This also applies to replacing resistors from one type to another. This is the voice of experience.
Thanks, Jeffrey. Email sent.
I see now...the pic shows Multicaps. I like how you replaced the whole line of 2.2uf power caps.
I already installed Jensen electrolytics in the PS of my PV5, I'm happy with those for now.
I like your bypassing idea. I wonder though if bypassing would sound better than throwing in a Mundorf Supreme or Auricap.
I see now...the pic shows Multicaps. I like how you replaced the whole line of 2.2uf power caps.
I already installed Jensen electrolytics in the PS of my PV5, I'm happy with those for now.
I like your bypassing idea. I wonder though if bypassing would sound better than throwing in a Mundorf Supreme or Auricap.
Phono stage?
I certainly didn't suggest he replace any RIAA-eq. caps in the fono stage. The couplers, yes.
Frankly, the film caps that CJ use are good. If you want to do better you need to invest in seriously good caps like V-cap, RTX or some of the Mundorfs (choice here depends on your taste). If you choose to go with any of these, I would not bother bypassing them with smaller value caps. I hate the results of bypassing (though for some reason CJ seem to have got it right). If you change the stock caps then simply omit bypasses. Listen to the amp without the bypass caps. You can always add the bypass caps later if you must.
No, Jeff, you didn't, and I did not mean to say that you did. I only wanted to make that point. But you did say:
I was thinking this could be interpreted to include the phono stage. Replacing (upgrading) capacitors in a power amp or line stage is no problem-o. But all the parts in a phone stage, which is a tuned frequency sensitive network, work together in synergy as a whole. It is not just the EQ componets alone. In fact, one could extend this reasoning to include the entire preamp since measurments are usually taken at the final output.
Assuming a manufacturer has done the job correctly (and I give CJ the benefit of any doubt biased on their experience). when an audiophile or technical person modifies a preamp with a tuned circuit to get a "better sound", what have they actually accomplished? A more euphonically pleasing sound, but one that is no longer sonically correct?
Part of my electronic background is test equipment and calibration which tends to affect how I think about things, for better or for worse.
Thank you for all of the advice, everyone.
I primarily use the phono section.
The problem is that this unit has had some hard failures in the past; it sounded awful and was very unstable when I first got it. I've had problems with the transistors burning out every few months, but am now finishing the PS rebuild.
It's starting to sound pretty good. It went from no bass to flabby bass, and now good bass, and a loss of glare.
I certainly want to use a light touch when improving. Thought I would start with the coupling caps, but there's such a vast array of available caps and huge differences in price, I wanted to seek advice before I risk spending on something that sounds thin and edgy.
Would like to hear more clarity and depth.
Thanks again.
-Gabe
I primarily use the phono section.
The problem is that this unit has had some hard failures in the past; it sounded awful and was very unstable when I first got it. I've had problems with the transistors burning out every few months, but am now finishing the PS rebuild.
It's starting to sound pretty good. It went from no bass to flabby bass, and now good bass, and a loss of glare.
I certainly want to use a light touch when improving. Thought I would start with the coupling caps, but there's such a vast array of available caps and huge differences in price, I wanted to seek advice before I risk spending on something that sounds thin and edgy.
Would like to hear more clarity and depth.
Thanks again.
-Gabe
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As I mentioned, the signal coupling caps that CJ uses are good. Also please don't bypass coupling caps in the signal path (or replace any bypasses that CJ has in place). If you really want to do a few more mods, I would suggest that you look at replacing the stock volume pot with something much better - a stepped ladder attenuator and bypass the balance control.
No. If you are using a "better" cap, you do not have to use a bigger value to account for the value of the bypass. Remember that in the day, bypass caps were used to improve the high-frequency response of a capacitor. Modern caps, electrolytics included, have very good hf characteristics. Adding bypasses to these more often than not create a less than natural sound.
Huh? This thing was designed and built 35 years ago! The section-output couplers are even c-j's own 'propylenes.
Your advice MIGHT be applicable to a medium-price c-j preamp from, say 5 years ago, but caps have gotten lots better sounding in 35 years. I've replaced the front-L/R c-j-'propylene-and-'styrene-combo output couplers (total of 4.15uF) in my 6-channel c-j MET1 with SoniCap Platinums. The music is audibly cleaner, airier, more transparent than before, and I didn't think there was anything wrong to begin with.
I have found invariably that adding a higher-quality, smaller bypass cap to couplers or PS-bypasses improves the sound, and I've evolved to ever-more-expensive hi-end caps as I've gotten more experienced with listening to music, including LOTS of real...not reproduced...music and improving various pieces of audio gear. My MET1 uses SoniCap Platinum couplers (2uF) and Jupiter HT and Platinum PS-bypass caps, and my system has never sounded better.
I now choose to perceive MultiCap RTXs as entry-level hi-end caps, with SoniCap Platinums as the best sounding. Mundorf Silver/oils, Cardas GRs, and Jupiter HTs are also at least very good.
Isn't it great that we have SO many choices?
Thanks ihear21khrz,your description makes perfect sense.
I agree that there is ample opportunity in improvement by substituting at least, the output caps at first. i also agree that if I were to replace any of the caps that they would have to be very good caps. Unfortunately, there are budgetary restraints.
Been looking at Mundorf Supremes and/or Russian Teflons as bypass caps.
What about PIO?
I agree that there is ample opportunity in improvement by substituting at least, the output caps at first. i also agree that if I were to replace any of the caps that they would have to be very good caps. Unfortunately, there are budgetary restraints.
Been looking at Mundorf Supremes and/or Russian Teflons as bypass caps.
What about PIO?
I throw my lot in with "ihear21khz." The problem with this whole idea of "upgrading" with improved caps is that ALL caps sound different; a modern cap will definitely sound different from what is in there now, and it may even sound better in some ways such as inner detail and imaging, but that doesn't mean it will sound better overall. Quite often a modern film cap will skew the tonal balance towards the "lean and bright" sound that many people like today. Someone who favors a warmer, rich and smooth sound will not consider the lean and bright sound an improvement. Quite the opposite.
Bypass caps are another example of this. A small bypass cap in my experience provides extra excitement in the highs with heightened detail and imaging, but at a cost---the highs have an unnatural emphasis, and usually the bass becomes lean. Some would consider a bypass cap to be an improvement. Others such as myself can't stand them.
CJ has a good reputation for choosing components in their products that produce the sound they are looking for----the CJ house sound. If you have a CJ preamp from the 1980s and like its overall tonal balance, there is a very good chance that you will upset its tonal balance by replacing its coupling caps with modern caps. You might like it, but then you might not. You just have to try it and find out for yourself.
Bypass caps are another example of this. A small bypass cap in my experience provides extra excitement in the highs with heightened detail and imaging, but at a cost---the highs have an unnatural emphasis, and usually the bass becomes lean. Some would consider a bypass cap to be an improvement. Others such as myself can't stand them.
CJ has a good reputation for choosing components in their products that produce the sound they are looking for----the CJ house sound. If you have a CJ preamp from the 1980s and like its overall tonal balance, there is a very good chance that you will upset its tonal balance by replacing its coupling caps with modern caps. You might like it, but then you might not. You just have to try it and find out for yourself.
Thanks for the input. All of these are considerations that made me bring this to this forum.
Besides, it's fun!
SY--No need to feel defensive. What 'I want to hear' is the glorious mid range that these PV5s others report them to have, any tips on how to achieve this are appreciated.
I am rebuilding and improving the PS. As far as circuit changes, I have heard of some who have had success in elevating the performance of these preamps, but unlike the ST-70, how one might do this is not exactly ubiquitous info on the web. Any ideas?
Besides, it's fun!
SY--No need to feel defensive. What 'I want to hear' is the glorious mid range that these PV5s others report them to have, any tips on how to achieve this are appreciated.
I am rebuilding and improving the PS. As far as circuit changes, I have heard of some who have had success in elevating the performance of these preamps, but unlike the ST-70, how one might do this is not exactly ubiquitous info on the web. Any ideas?
I've rebuilt several of these. An active reg (i.e., not a cap multiplier) is a good start. You can use a simple two transistor regulator (see Morgan Jones "Valve Amplifiers") or even better, a Maida type reg.
Look at what gain you really need out of the line stage. For most setups, unity gain is good enough and you can eliminate most of the circuitry (nothing sounds better than nothing!). Either go passive or use a cathode follower- using a better tube for that purpose than 5751. The phono stage can be upgraded by removing the feedback, increasing the gain (LED bias instead of resistor, CCS plate loads), and putting a passive RIAA network between the two stages.
Look at what gain you really need out of the line stage. For most setups, unity gain is good enough and you can eliminate most of the circuitry (nothing sounds better than nothing!). Either go passive or use a cathode follower- using a better tube for that purpose than 5751. The phono stage can be upgraded by removing the feedback, increasing the gain (LED bias instead of resistor, CCS plate loads), and putting a passive RIAA network between the two stages.
SY's suggestions are great but what you will end up with is something very different that sits in the casework of a PV5. If you are considering such a major rework of the circuit, I suggest that you build a preamp from scratch - something like the Vacuum State FVP5A. Keep your CJ as is and enjoy it for what it is. It will probably be worth more without your hacking it.
Jeffreybehr,
Many modern film caps would be superior from a technical point of view (to CJs selection 35 years ago in the PV5) . However there are just too many variables to suggest that one brand/type of cap will sound "better" than another in the CJ or indeed in any other amp circuit.
There are many who swear that good old oil filled caps are the ONLY choice for tube circuits. You yourself like the Jupiter cap. I'd like to know how a Jupiter cap measures in terns of dielectric absorption. Probably not very good - and worse than CJs 35 year old props. CJ's "glorious mid-range" isn't an accident and I am certain that the choice of cap (and the bypass) has much to do with this. My point is that changing these will greatly affect the voicing of the amp.
Cheers
Jeffreybehr,
Many modern film caps would be superior from a technical point of view (to CJs selection 35 years ago in the PV5) . However there are just too many variables to suggest that one brand/type of cap will sound "better" than another in the CJ or indeed in any other amp circuit.
There are many who swear that good old oil filled caps are the ONLY choice for tube circuits. You yourself like the Jupiter cap. I'd like to know how a Jupiter cap measures in terns of dielectric absorption. Probably not very good - and worse than CJs 35 year old props. CJ's "glorious mid-range" isn't an accident and I am certain that the choice of cap (and the bypass) has much to do with this. My point is that changing these will greatly affect the voicing of the amp.
Cheers
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