Recap

[vinsnobben]

Hi!

My CJ amps (P11a and P8a) are well over 20 years old. The last year or so I've noticed that the amps do not sound as they used to. I suspect that it's time for a recap, but I'm not sure. I e-mailed Jeff at CJ, and his response was that capacitors in CJ amps do not deteriorate over time.

But I'm not sure if that is true. In your experience, what are the audible signs of caps that need to be changed?

regards,

Vinsnobben

[AnotherJohnson]

That does not sound like Jeff.

It’s fairly true for the CJD proprietary Teflon caps. They will last the lifetime of most who buy them.

But the other polymer caps that they’ve used have a lifetime of about 20 years, and the electrolytic caps maybe 10 years.

Maybe your units were recapped with Teflon earlier, or maybe you misunderstood.

I won’t speak for Jeff, and would accept his correction ... but the idea that caps degrade over time dependent on their construction is not controversial.

[admin]

I agree with AnotherJohsnon. Caps do fail. I have had them fail in multiple electronics components (none were CJ however). But I have replaced faulty caps in my computer monitor, speaker crossover (which I posted about recently), and did a replacement for my home theater receiver when a cap failed for it's front display (I made a post about that too). So, yeah,... caps definitely fail although teflon should last very long and time does not guarantee a failure, just makes it more likely. Or at least that has been my personal experience.

[AnotherJohnson]

I would defer to JF. Maybe he was saying that the caps may not be the problem for these units. Perhaps there is some other issue. The lowest hanging fruit is to try new tubes. You can do that without sending it in.

I would not second guess JF on what’s going on in vintage CJ gear. But I still wonder if perhaps his advice was not fully understood.

As good as polymer caps are, age changes them eventually.

[Big Dog RJ]

G'day Vins,

That's probably true regarding the caps, especially in CJ amplifiers, they are built to last with high standards. Jeff knows about the quality of their parts, and this is basically what we pay for. Caps deteriorating or not, what actually happens over time is they lose their full capacitance to hold high levels of current. Slowly losing their current capacity, so not really deteriorating rather losing their grip...
Replacing the caps will no doubt restore the current capacity as new, and also replacing with Teflons improves not only current but also sonic performance.

When you mentioned the amplfiers aren't sounding like they used to, what are the symptoms?
1. Low dull sound
2. Transients not having their flare
3. Speed and power drive lacking
4. Lack of extended airy highs and low tight bass
5. Lack of sparkle in the midrange, not full and lush

If any of the above are what you're experiencing then it's time for a full tube replacement set. It's not the caps.

Caps going bad are different symptoms, usually distorted noises, lack of drive and early onset of clipping, that is harsh sound, simply because they have lost weakened their storage capacity. However, this is very rare with CJ amplifiers, most caps would just fail, causing loud pop / static bangs when the mute is depressed on the preamp, indicating a leaky cap, which is emanating DC off-set. This is a more serious issue and will not make the amplifiers operate normally. If these caps are knocked out, the amplifiers will be unlistenable.

However, if they're working but with the symptoms as listed above in 5 points, this is a weak output tube/s. Might as well do a full replacement on both amplifiers.

BTW, when did you carry out a full tube replacement?
Usually fresh tubes will last typically 2000 - 3000 hours, on average listening sessions that's about within 2-3 years. Therefore, if you haven't changed tubes since the last 3 - 4 years, it's definitely high time you did!

BTW, I've owned both the Prem11 & 8a monoblock amplifiers, they are very fine amplifiers in every regard.

Cheers, and let us know how it goes.
Best, RJ

[vinsnobben]

Thank you all for your advice.

Here is what Jeff wrote to me in september last year:
"The audio capacitors in the PREM11 do not degrade over time , but replacing these capacitors with our CJD TEFLON caps will definitely improve the sound quality."

The amps were retubed two years ago, but as I play with the Premier 11a in summertime, and the 8a's in the wintertime, I estimate that both amplifiers have run approximately 500 hours since retubing. So in my opinion it's not the tubes. Output tubes are PM Guitar tubes which is the same tubes as Golden Dragon 6550. Input tubes are NOS QTL 5751 (East german Telefunken) and NOS Westinghouse 6fq7.

Of the five points you mention RJ, the symptoms are in the direction of 5. Lack of sparks in the midrange, not full and lush. I would describe the sound of the 8a's as excellent in soundstaging, transients and a full bodied bass. No problems. But voices appear a bit harsh, especially female vocals, but even some male vocals on some CD's sound harsh, but not as much on vinyl.

I would like to do the C1 upgrade, first with the Premier 11a, but as I live in Norway, the cost of shipping to USA and back will be costly. I've also talked to the distributor of CJ in Norway, and he says a set of teflon caps for the Preier 11a will be $2000 + I will have to pay for labour. I suspect the local distributor is trying to make an extra profit as I've learned that the C1 upgrade including labour at CJ is about $17-1800.

Cheers!
Vinsnobben

[Big Dog RJ]

Lack of midrange sparkle and lushness, could also mean the input and driver/phase inverter tubes, not necessarily output tubes. These small signal tubes can go bad even within a few months, so perhaps changing them may improve things, you'll have to try it.

As for the cost in the upgrade, that's about right. $2000 should include the KT120 tubes, Teflon caps (about 4 - 5 Teflons) and Vishay resistors. Check with CJ that they are including the Vishays and not just metal foil resistors. These are still pretty good but not as premier quality when compared to Vishays. The Vishays are in a class of their own, they're truly remarkable.

If the local CJ authorised tech / service centre can carry out the job then I'd stick with them, since shipping all the way to VA in the US will be far more costly.

See how it goes. Cheers RJ

[vinsnobben]

Well, the $2000 price tag was only for the teflon capacitors, I think + shipping.

[petertg]

The fact that both amps started to sound bad at roughly the same time makes it unlikely that they have a problem. It is likely that the problem resides elsewhere in your system such as ac power or in another component. It could be as simple as cleaning your cable terminals. I would suggest that you use a place process of the elimination to find the cause.

[Big Dog RJ]

That's a very good point by Peter.

Infact, I didn't think of that. Since both sets of amplifiers went a bit dull around the same time, could well be the connections. Makes perfect sense.

Also was wondering, what's the preamp?

Maybe the preamp needs re-tubing, and that's if it uses tubes in the first place.

Then again Vins reckons there's no dull sound, both amplfiers play fine, power, drive, transient control are all fine, except a lack of sparkle and lushness in the midrange. To me, that's within one of the tubes, most probably the smaller signal tubes...

However, as Peter mentioned, I reckon a complete disconnection of the entire system, with a full clean up using de-oxit or contact cleaner, plus a full wipe down of all cables with the Eco3 solution from Nordost or similar. Basically a full clean up of all contact points, including components connections, speaker terminals and tube pins. With tube pins, be careful though, don't damage the pins, just a light dab of contact cleaner with a cotton swab will be sufficient.

Once all done and reconnected, slowly powering up each component, and bring the tubes back to life, this should add that sparkle and lushness. If not then some other thing is definitely off.

I generally do a full disconnection and clean up every 6 months, and things sound mighty fine, crystal clear!

Was also wondering if your preamp is phase inverting? Remember that CJ's preamps are phase inverting, therefore in order to achieve absolute phase, you must reverse the polarity (+ & -) at the speakers terminals. Remember to reverse both channels L & R speakers, not just one speaker otherwise your system will remain in relative phase / partial phase and not absolute phase. This could also explain the lack of sparkle and lushness...

See how it goes and let us know what you find. Always good to learn from these things, can be very helpful to others.

Cheers, RJ

[Toberius]

But I'm not sure if that is true

Hi sir.
Could you tell me what makes you hesitate ?

In your experience, what are the audible signs of caps that need to be changed?

Measurement instruments.

The ear is the best instrument, but that instrument does not work in my case. I use another one that does work for that purpose: DER EE DE-5000 a LCR Meter from DER EE ELECTRICAL INSTRUMENT.

My best.