Premier 12 Cover Modification

[goonybird]

Since fitting KT90's the top of the "Cage" has been very close to the tubes.
I had the Cages sitting on the amp top using small rubber stick-on feet to raise it slightly.
Had the idea to fit speaker spikes.
So Tapped the holes with M6 tap, metal is just thick enough
This allows me to screw spikes in. The spikes tips align and fit into the tops of the Hex bolts screwed into the chassis.
I am not convinced by the slightly awkward appearence, but does allow for higher still, using longer spikes to clear KT120s
Also not limited to just the Premier 12.

[AnotherJohnson]

Very nice, simple, nondestructive mod. Thanks for sharing!

[admin]

That's really great. It actually makes it look more modern in my opinion. Maybe even better for heat dissipation as the airflow may be improved.

[Big Dog RJ]

Nice one gb, a job well done!

I was intrigued to learn that you're using the KT90 tubes... are you using the EI branded version or something else?
How do you find the sound and overall performance?

Going back quite a while, when I had two versions of Manley Labs monoblocks, which are still in production btw, Eve Anne Manley highly recommended that I try these KT90ei tubes that they also use in top of the line Neo 500's. So for the first time, I tried them out, changed from the 6550's, and wow, it was a remarkable change!

From that point onwards, I just stuck with the KT series tubes. Manley Labs uses the EL34's in their Neo 250's, which are rated at 250w solid tube power, and I really loved those amps. However, the moment I experienced the Neo 500's based on the KT90's, I knew straight away why they chose this tube.

On your Prem12's, they must be sounding tops! Excellent preamp choice as well, the Prem17LS, that's a really fine combination
Cheers, RJ

[goonybird]

It had GE 6550s but had two fail. The KT90s are Electro Harmonix. They make the amps a bit sound solid state and "upfront" so more modern twist?.
Have got used to it.

[Joe Appierto]

You've hit the nail on the head with describing the KT90 tube-type sound. My conclusion, using both Ei and Electro-Harmonix KT90s in two different CJ amps was that they were the most solid state sounding of any tube I ever used. And I tried just about every "flavor" available at the time.

[AnotherJohnson]

You've hit the nail on the head with describing the KT90 tube-type sound. My conclusion, using both Ei and Electro-Harmonix KT90s in two different CJ amps was that they were the most solid state sounding of any tube I ever used. And I tried just about every "flavor" available at the time.

Joe, you are a good, gifted listener.

Do you sense that all of the modern Kinkless Triodes have this tendency toward SS sound? KT120 or KT150, for example.

I seem to prefer them… and I have also often found myself enjoying good SS implementations like from Levinson or Krell. Or even from CJ in the form of the 2550SE or P350.

RJ has also expressed positive thoughts on some of the high end SS offerings.

[Joe Appierto]

I'm glad you used the word "modern" because I thought that the KT88, especially the original Genalex wasn't solid-state sounding. I've also never heard the KT-150 so I can't express an opinion on them.

Good equipment, and that certainly (understatement) describes what you, Roberto and RJ have is simply enjoyable be it solid state or tubed.

The KT-90 was developed I think by the Manley family for their amps at the time. They were fast, accurate, and very good in telling the musical truth. I used them and enjoyed them but given my druthers I preferred an old-fashioned Tung-Sol and its kin.

I know I'm not answering your question and sorry not to do so but the closest I can come is to say that while the KT-120 doesn't sound as sold state as the KT-90, it does sound less tubey to me than traditional 6550 and their variants.

[Wildcat]

Nice mod! I have a Premier 11 running KT120s and while I don't really want to cover up the tubes with the cage, a change in my rack might be necessary since I need a little more space.

I'm thinking of using threaded circuit board standoffs (or a similar threaded collar), painted black, provided I find some that fit the C-J's threads.

[Big Dog RJ]

Hey Wildcat mate, how's it going...

I completely missed the fact that you are now using KT120's in your Prem11. That's really interesting, how's it sounding?

Did you notice better control in the bass, and drive factor of the amp... mids & highs sound fuller. However, some still prefer that lush midrange found in the 6550C type. Going from 6550's to KT120's, what are your thoughts and overall was it a worthwhile option for you?

There's a chap here who wants to do the same but I mentioned to first try out the 6550C tubes. Now he's in a dilemma.

Also, were you able to bias ok according to spec?

Cheers, RJ

[Wildcat]

RJ!

I've had KT120s since I purchased it. I think the amp might have had the original factory tubes when I picked it up, as it did not sound very good (it sounded tired if that makes sense). Seeing how the KT120s were described (especially being more solid in bass), I decided on those. I haven't felt a need to roll tubes since I like how it is sounding. When I sent it in for service, Bill suggested I change the 6FQ7s to NOS RCA vs the Brimars I was using. I don't hear a difference to be honest, but it's good to have spares.

[Big Dog RJ]

Ah! I see. So you've used the amplifier fitted with KT120's from the start. Excellent to hear that you like the KT120's and the Prem11A is sounding fab!
Cheers mate, enjoy those fine tunes.
RJ

[WGS57]

GB, I followed your mod with the cages of my P12’s and my KT120 replacements and it looks great. Thanks so much for sharing with us! Bill

[roberto]

Hola Chicos,
Nice job Bill!...

Regarding using the KT'150s replacing the KT'120s, Mr Jeff Fischel does not recommend it. Talking about it with him, my conclusion is that the voltage regulators for the filaments of the tubes are very specific for the current that the KT120s drain, the KT150s drain more current, so my guess is that this is the main reason why not to use them as a direct replacement. The regulator might drive one KT'50, but four or eight tubes?

Happy listening!

[Wildcat]

Hola Roberto!

I never considered using KT150s as I felt it would be a waste of money due to these amps not making full use of their power. Even the KT120 is underutilized but I am hoping that not pushing these to their maximum will help extend their lives.

I almost considered having my Premier 11 modified to output more power, but it would lose a lot of value. I imagine someone could similarly modify Premier 11s or 12s to use KT150s but again, the lost value would not make this attractive.

The only modifications I had Bill Thalmann make to my Premier 11 were to add an IEC socket for power (the power cord's jacket was damaged when I bought the amp several years ago), and had him bring the 11 up to date and make it an 11A (according to schematics, it was nothing more than adding a bypass capacitor in the LED circuit to reduce noise).

[roberto]

Hola Wildcat, it is a pleasure to be in contact with you.

I just wanted all to know the reason why we should not use the KT-150s as a direct replacement for the KT-120s.
OTOH, I did some tube rolling with my amp. My findings was that I should stick with the KT-120s. I did find more organic sound, more music info, more bass control, more stage stability and super clear highs with them than any other tube (6550s family). You can't go wrong with it. I use less bias polarization with my KT120s. What I do is, once the LED bias goes off, I kept turning the bias screw a little bit further...and that's all.

Happy listening!

[Wildcat]

I have similarly found that I like the KT120 over the 6550 tubes that were in the amp when I purchased it. I find that with all of my other system improvements, I can now just sit and enjoy music and not worry about the equipment.

[Big Dog RJ]

Nice one maties, that's a fine combination!

In fact, I've brought down a few KT150 based power amps on trial. Although I must say they drove the ML CLX's very well indeed! They also needed more room to really open up. The KT150 is definitely a power house, no doubt!

It can very easily propel large amounts of power more efficiently and effortlessly compared to the others. And once it gets going, it really gets going! It's nearly close to SS power and closer to SS design bass. It has that low end grunt and sudden burst of energy that comes with great speed and acceleration. Basically very effortless dynamics.

Now comparing that with the KT120, this is where the beauty lies. Having a bank of KT120's offers exactly that! They can perform almost on the same parameters, and also deliver effortless dynamics, without a doubt! What I found to be most significant was the low volume levels. Listening at low levels on late night sessions for endless hours is something that I've always found with EL34's, KT88's, and KT120's. All the fine details of the full audio spectrum is right there in front of you, there's simply nothing more needed to enjoy pure music.

However, with the KT150 topology, I've found the best performance comes with higher playback levels on very high performance speakers. For example the ART300's or the ART150, when driven at high levels don't flinch one bit... as long as the speakers are capable of such high Input power. Listening to a system based on the KT150 topology at lower levels is do-able but having much more power on tap, makes you want to turn things up. And Listening at high levels is not my thing. That's why I prefer KT120's.

Then comes CJ's ART108A and the ART27A, which uses the KT88's. This is a FAR cry from the norm of KT88 based systems, where they used to be very seductive and relaxing or laid back type of sound. JF has taken a radical approach to the Classic Class A bias circuit and turned out the KT88 design to be all a KT88 can be but with all the pure finesse of Class A power, and it's truly awesome! Now that's very different and it comes with a price!

As for now, the KT120's are my all time favourite pentodes and I've been using these since 2009. So cheers to all those KT120 fans, and do enjoy those fine tunes!
Woof! RJ

[Wildcat]

I can't listen at high levels anymore myself, so I appreciate the sound I get from my KT120s. With tinnitus, actually, listening at higher volumes only causes the ringing in the ears to pulse loudly with the music, so it's too uncomfortable to turn it up. Some days are worse than others.

I'm pretty sure that I read somewhere in these forums that C-J now recommends KT120s for the older amps. I had someone on another forum tell me that C-J doesn't know what they're doing and that KT120s can't be substituted for 6550s without damaging the circuit and/or tubes...but he also owns an amplifier company himself (tubed, DIY kits, been around a few decades...probably obvious who it is) so I naturally told him that I trust C-J's word over some random person on the Internet.

[Big Dog RJ]

Haaaa! Nice one WC!

Oh, sorry to hear about your hearing issues... at least with CJ gear, those tunes are fine even at low levels. That's why the majority of my listening sessions are way past 10pm into the wee hours of the morning. Dead silent and I can hear every detail on quality recordings.

Cheers mate, and enjoy those fine tunes!
RJ