Working on my Premier 8XS Amps.

[BobWilson84]

Hey everyone, long story short these Premier 8XS amps are new to me but I've been lusting after them for many years.

I'm an audio tech with zero CJ experience, but I know my way around a work bench (and always learning). Here's my plan

#1 They need a good cleaning with bits of broken tubes in the chassis. Everything needs a good scrub.
#2 Replace 9 electrolytic capacitors for peace of mind.
#3 Clean and lubricate the bias pots
#4 Document circuit topography compared to the schematics available on this site.
#5 Install a simple IEC connector to replace the bulky power cord.
#6 Perform load testing and measure THD & Freq Response. I would also like to chart inrush currents at start up and idle wattage for the fun of it.

Regarding the power cord, CJ used a dual conductor #14 CU which explains it's stiffness and bulk. It's a personal preference for me to use a IEC. I'm not going through the trouble for audio quality or sonics, I just want to make my installation easier and neater. I feel like simple 12AWG cord with the short length to my power supply with perform adequately in my case.

If anybody has service experience with the Premier 8 amps please let me know. I'm certain it would be helpful for current and future owners to have reference information.

Thanks!

[admin]

Welcome to CJO, great to have you with us.

Looks like a fun project. That's a great amp and looks like it's in very good condition so hopefully not too many problems along the way. Keep us updated.

[Big Dog RJ]

Oh! Nice one on the Prem8- XS version mate.
These are really tops, especially with the EL34 config in Triode mode. CJ's XS versions were always something quite special, and superb soundstage depth.

We ordered three versions of these Prem8's back in the day; Prem8xs, Prem8 and Prem8A, all of them were just superb! If memory serves correct, I think CJ supplied us with the Mullards EL34 and on the standard Pentode version, they came fitted with 6550C tubes from SED (Svetlana Electron Devices) made in Russia. There was a time when after the very last pair of Prem8's we sold to a customer, he had changed those output tubes to KT90 EI, and experienced an even further level of performance. I think the speakers being used at the time were the Maggie's MG20's, however in our own system the Prem8A's were used to drive Apogee Diva's partnered with the ART preamp. Fantastico!

I'm sure you'll be able to fully resurrect these beauties and achieve that legendary sound! Simply marvellous!
All the best and do keep us posted along the project.

Oh! One thing I forgot to mention, another customer of ours kept his Prem8A's to this day but upgrades were done along the way. These included Teflon caps and Vishay resistors, plus IEC type power sockets and ceramic tube sockets. I heard these upgrades done and they didn't sound anything like the original at all, rather an elevated standard of the LP275M's. Those upgrades did cost him a pretty penny for each monoblock but I guess it was worth every penny, since he has a very strong attachment to these amplifiers and says there was nothing quite like them ever made! I agree.
He's now using big Wilson's, effortless dynamics.

Cheers mate, and enjoy those finest tunes!
Woof! RJ

[zermatt]

Bob;

I have the same amp and its been updated by the legend Bill Thalmann of Music Technology. I have the Prem8XS rev A. Bill updated the input cap and driver stage caps with VH Audio copper Teflon's. He also replaced the rectifier diodes, this was a major effort. This really transforms the imput in to a very transparent amp. The input cable was replaced with a Siltech royal signature princess. The AC cable was replaces with furutech 20 amp outlet. All fuses were replaced with HI FI tuning Supremes.

Areas that could also be improved. The resistors in the driver stage. The pwr supply transistors are bipolars, fets would by a big improvement (this is what CJ is using now).

Please note: CJ will not repair units that have been modified by thirds parties. This will be a issue when you resell the amps. The one exception was Bill T of Music Tech, but bill is working on systems in heaven now! So he not available! If you have any more questions let me know!

[BobWilson84]

Edit: there may be other schematic changes from a typical 8A, so please take all of this with a grain of salt. I don't have an 8A to compare, and the schematics available are too blurry to make out detail. Determining bias and power supply changes without a good schematic is too hard for someone like me with limited CJ experience.

For those who are interested, the 8XS version uses these connections for triode operation.

Screenshot 2024-02-24 at 9.47.17 AM.png (68.17 KiB) Viewed 342 times

Also, there are 7x electrolytic capacitors. I didn't bother testing, but I replaced them with fresh Nichicon for good measure.

Screenshot 2024-02-24 at 9.40.20 AM.png (42.95 KiB) Viewed 342 times

The IEC connectors are a good fit for the factory chassis hole. The original power cord is #14 triple for L & N and #14 double for ground. They are not braided, but rather twisted around a nylon core. Very interesting. The large iron snuffer and the RF filter will suffice for my application with a typical #14 braided IEC cord (nothing fancy here). I will post results as I use a Bluetooth streamer in proximity.


I hope these pictures and notes help anybody who is considering this modification. The are no tricks to working on these amps, they are big and heavy. The main board is stuck in the chassis which makes servicing very fun.

[Big Dog RJ]

Really nice one matey
That's a very intense project... I would've blown the house down by now, not very good with intricate stuff like this, hell no!

Do let us know when it all comes together, those Prem8A's will always have a legendary sound, and now that you've got the XS- EL34 version, that's one mighty fine thing indeed!

Cheers and all the best, great stuff.
WOOF! RJ

[BobWilson84]

I'm posting this incase somebody else has similar problems. These amps sat idle for most of their life. I've probably cycled their power more times in the last 2 weeks compared to the last 30 years. I know the previous owner had issues with bias adjustments and he tripped the breaker a few times. I tripped the breaker as well, and this stress probably failed a few components. I think the 20ohm cathode suppressor resistors should be replaced as preventative maintenance. One of mine failed catastrophically and one was cracked. The values were nearly correct, but I didn't check drift with heat. Additionally, the op-amps that control the LEDs and trip the breaker can be prone to failure. One of mine blew in spectacular fashion. The Op-amps are energized whenever the amp is plugged in which probably contributes to their life span. The material costs for the resistors and op-amps is like $20 per amp plus another $15 for the 7 electrolytic caps that should be replaced if they are original. This repair project was more of a mechanical and technical endeavor compared to a monetary output, although purchasing the amps was the latter! -Bob

[admin]

Nice repair work. Some components definitely do age out. Not only by use but storage conditions as well. You mention that the unit may not have had a lot of hours of use, but if not stored in proper temperature/humidity conditions, I've seen that do a fair amount of damage to electronics over decades. I've seen significant corrosion on some units just by being in a humid environment.

PS- in the third picture, I see what looks to be cap bulging on the top right cap, that probably should be replaced.

[AnotherJohnson]

PS- in the third picture, I see what looks to be cap bulging on the top right cap, that probably should be replaced.

It’s not an electrolytic, but it’s old enough that even the non-electrolytic caps could be approaching end of life. At least it shouldn’t make a mess.

[SolderSlinger]

Thank you for posting great pictures. I never realized that the Premier 8 mounted the output tube sockets different than other amp offerings. Whenever I put an output tube in other CJ amps, I think "why didn't CJ leave enough room so that the tube will sit flush in the socket?". Seems goofy to not have full pin engagement.

[BobWilson84]

PS- in the third picture, I see what looks to be cap bulging on the top right cap, that probably should be replaced.

Yep good eye, pictures were from various stages of the project.