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Old 05-08-2016, 12:12 PM
microstrip microstrip is offline
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Default LP275M teflon capacitors

When thinking about any upgrades for my cj LP275m's I was very pleased to find that my units include the famous CJD teflon capacitors in all signal and decoupling position.

Besides the input and driver tube types, do you know what are the main differences between the 275m and the ART?
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Old 05-08-2016, 04:38 PM
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Others will comment with more but I believe the input circuits and tubes were upgraded and a big difference between them are the ultra wide band output transformers in the ART monos. That said, not wanting to spend the money to go to the ART monos, I asked c-j if in made sense for me to move up to the ART stereo from my LP140 monos and the answer was no it did not.
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Old 05-08-2016, 04:58 PM
mfoley3 mfoley3 is offline
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I was given similar advice by my local dealer when choosing between an NOS pair of LP140Ms and a new ARTSA. His thought was that the SA would offer a bit more finesse, but that the LP140Ms were simply "more of an amplifier" and it's dynamics, power reserve, etc. made it the better choice. I've had the LP140Ms for two years now and love them. When inquiring about the ART Monos, I was advised that I would be better off putting the price differential into other upgrades such as a Rubidium clock for my Esoteric K03 CDP.
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Old 05-08-2016, 05:08 PM
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I've been told and am now convinced that monoblock amps are just better than stereo amps. The channel separation is obviously better but having individual, unique power supplies for each channel is just huge when it comes to the work of driving speakers.
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Old 05-09-2016, 04:16 AM
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Briz Vegaas Briz Vegaas is offline
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The regular 125m does not have Teflon. The OP must have the SE version. I have contemplated the pair of 125m that my dealer has but figured that my LP70s with Teflon would have more finesse.

There is also the issue of power cable investment. I use Nordost Valhalla that i gradually accumulated over many years of audio addiction and i use one in series which runs the DAC and amps. i found this was better than a shorter run, believe it or not ( i think this says something about how they do what they do). So, yes i could configure a monoblock based system so everything had its own fancy power cable, but the run would be shorter and everything would suffer as a result. Give with one hand, take with the other.

If the 125ms were teflon, or if it didn't cost over $5k Australian to upgrade, then i might even consider the 125M. Its probably just as well, i'm supposed to be rebalancing my finances, get the mortgage out the way, that sort of thing. I just need to behave myself for a couple more years.

Last edited by Briz Vegaas; 05-09-2016 at 04:27 AM.
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Old 05-31-2016, 10:57 AM
stereoquest stereoquest is offline
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Microstrip,

It is my understanding that the, Lp275 and Art Mono share the same ultra wide bandwidth Output transformers. The lower powered models, LP140 and Lp70 share a different output transformer which does not have the same bandwidth. The leap in performance from an LP140 to LP275 is considerable and the output transformers accounts for a part of this.

The major change from Premier 8 to Lp275 was in the input circuit and a refined board layout with of course the use of Teflon capacitors. The change from LP 275 to ART is mainly the input circuit and a few refinements in output stage that changed. For the whole the 8 – 275 – and ART mono’s all share the same basic output design….with the ART and 275 being the most similar overall.

As for modification to the Lp275 Amplifier ….. Progress slowly, evaluate each step on its own and allow at least 50 hours of play in-between changes ---It is all very personal at this point------pre ‘burn in’ of new components is recommended using a signal generator or other source ( a cheap receiver playing 24/7 with components wired in series to the speaker works well .
All signal series resistors –Vishay vsh1 ( yellow ) can be systematically exchanged for Vishay Z foil 2575/Charcroft. The grid resistors in the input stage are also worth looking at.

As good as the CJ Teflon capacitors are– I have used Dueland Cast to very good effect in the coupling capacitor position and prefer it . Thankfully the coupling cap sizes in the power amps are low value compared to the pre amplifiers and cost considerably less.

There is more scope for improvement with the older pre amplifiers – Premier 16 and ART than on the power Amplifiers.
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Old 06-07-2016, 09:47 AM
microstrip microstrip is offline
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Quote:
Originally Posted by stereoquest View Post
Microstrip,

It is my understanding that the, Lp275 and Art Mono share the same ultra wide bandwidth Output transformers. The lower powered models, LP140 and Lp70 share a different output transformer which does not have the same bandwidth. The leap in performance from an LP140 to LP275 is considerable and the output transformers accounts for a part of this.

The major change from Premier 8 to Lp275 was in the input circuit and a refined board layout with of course the use of Teflon capacitors. The change from LP 275 to ART is mainly the input circuit and a few refinements in output stage that changed. For the whole the 8 – 275 – and ART mono’s all share the same basic output design….with the ART and 275 being the most similar overall.

As for modification to the Lp275 Amplifier ….. Progress slowly, evaluate each step on its own and allow at least 50 hours of play in-between changes ---It is all very personal at this point------pre ‘burn in’ of new components is recommended using a signal generator or other source ( a cheap receiver playing 24/7 with components wired in series to the speaker works well .
All signal series resistors –Vishay vsh1 ( yellow ) can be systematically exchanged for Vishay Z foil 2575/Charcroft. The grid resistors in the input stage are also worth looking at.

As good as the CJ Teflon capacitors are– I have used Dueland Cast to very good effect in the coupling capacitor position and prefer it . Thankfully the coupling cap sizes in the power amps are low value compared to the pre amplifiers and cost considerably less.

There is more scope for improvement with the older pre amplifiers – Premier 16 and ART than on the power Amplifiers.
Thanks for your information. I will however keep the cj capacitors in my units - I love the way they sound and my other cj units have now this type of capacitor - changing it could unbalance the whole system.

Do you know what type of refinements were carried in the output stage? I could not imagine any - it is already very simple. Curiously the cj schematic shows 6h30's in the driver position.
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Old 06-07-2016, 12:49 PM
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If I remember a conversation from a few years ago with c-j management correctly, the input circuit of the ART amp family was redesigned along with more teflon inside. Also, I recall that the output transformers of the ART amps were special, of upgraded bandwidth. The LP275 output trannies were more substantial than the lesser LP models as more power allowed them to drive bigger iron, so to speak. They made special mention of the custom wound, broad spectrum output trannies in the ART amps.
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Old 06-07-2016, 04:24 PM
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I'm now remembering that the LP275 trannies have to be bigger as they have to service twice as many output tubes. Each output tube needs it's own winding for input, thus twice as many input windings for the LP275 as the LP140. I assume the output windings must be larger to accept the signal from more on the input side. These big transformers where there are eight output tubes are complex beasts.
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Old 06-08-2016, 08:14 AM
stereoquest stereoquest is offline
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From what I have seen the output transformers in the Larger 275 watt amps are completely different to the smaller series and need to be to cope with the extra output devices. Not only do they have a different turns ratio to account for the additional output devices but they also use a large gauge wire on the winding's to account for the increased load. Both of these qualities will extend the bandwidth and damping factor of the larger amplifiers beyond that of the smaller series. The big CJ’s all use these ‘special custom high bandwidth’ transformers and is why a smaller cj amp will never sound better than a larger one in the same system.
The smaller stereo and mono amps generally share the same transformers which is why they are practically doubles of each other----(the mono version being a double of the stereo version). With the smaller Mono blocks you instantly receive a doubling of power supply but not the larger ‘custom full bandwidth ’ transformers.

Through the years CJ have used a very similar recipe for their amps – P12 is ‘basically’ two P11’s – Lp140 is basically two LP70’s and so forth – The basic output circuits are for all intents the same -- it makes perfect sense to refine an excellent base product, after all the basics of tube amplification have not changed in 60 years—it has just been gradually refined.
Conrad Johnson probably has one of, if not the best and most expensive commercially viable parts bins in the business and they need to make the best use of it and do---this is why we can see many of the same parts being used throughout the range for nearly 20 years .

Changing coupling capacitors with like for like values is no different from changing interconnects…..at this point you are playing with the flavour of the amplifier. Teflon capacitors came in for one reason – CJ could no longer reliably source any more polystyrene and would not sacrifice on quality. The next stop as we all know was Teflon ----- but it is by no means the end of the road and other options are available but may not be commercially viable. Imagine the retail cost of the GAT if all the Teflon caps were replaced for something costing twice as much and marginally ‘better’ . Number one you would sell less pre amps number two they would cost more to make – in the end it is not viable but this does not mean that there are no other options out there. There is always scope for improvement –be that cars-boats- computers you name it ….hifi is no different---especially when the products are a few years old.
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