Premier 275 Crackling

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decofan
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Premier 275 Crackling

Post by decofan »

I just bought a pair of Premier 275 tube mono blocks. One of the amps "pops" while warming up and makes crackling noises. I have no idea what this is. The only things I could think of were perhaps biasing and seating. The tubes were new from CJ. Also, the amps came with extra fuses and these little rubber rings. What are the rings for?
System 1: CJ 17LS, CJ Premier 280 monos, MIT Shotgun 2, Rega RP6, Talon Ravens
System 2: Jolida JDT5, Quicksilver Silver 60 monos, Quicksilver Mid 40 monos, MIT AVT1, audioengine D1, Mourdant Short Performance 6
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Re: Premier 275 Crackling

Post by admin »

First, congratulations on the purchase. Very nice equipment.

As for the pops,... do you mean one speaker is making pops or there are actually pops coming from the Premier itself? Could it be just some heat expansion? If so, some tightening of the screws holding the boards and making sure the tubes a seated well may fix the problem.

As for the rings, can you post a picture?
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Main stereo: ART Amplifier and ET7s2. 2nd stereo: PV-14L and MV-55. Previously Owned: PF2 preamp, Evolution 2000 Amp, PV-12AL preamp, D/A-2b Vacuum-Tube Digital Processor.
jeffreybehr
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Re: Premier 275 Crackling

Post by jeffreybehr »

decofan wrote: Also, the amps came with extra fuses and these little rubber rings. What are the rings for?


The rubber rings probably are O-rings intended as dampers for the small frontend tubes, like these.
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Ian Millar
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Re: Premier 275 Crackling

Post by Ian Millar »

What are "Premier 275s"? Do you mean Premier 8s?

I am in the process of rebuilding my Premier 8-XS monoblocks. The right channel has crackling noises which emanate from the connected speaker. It sounds like frying bacon. The amplifiers are in my opinion VERY poorly constructed junk piles housed in expensive and fancy boxes. There has it seems to me been no proper attention given to thermal management and they are getting cooling fans to compensate for it.

The power supplies and output stage bias adjustment/indication circuits are in my opinion hideously complex and ridiculous. Many under-rated parts have been removed and replaced already with more suitably rated components. Fifty 1/2W zener diodes in 12 and 13-long strings for example! Once I have the answer I shall post a link to a blog page that I am dedicating to the rebuild (not yet on-line). It will not go down well with C-J.

The crackle is coming from somewhere either in the 390V B1 supply to the input stage plates, or at the 5751 plate resistors. It's around 5mV on the scope. It appears identically at around 50mV at the phase splitter plates. Temporarily shunting the 1M resistor of the LTP eliminated the noise by applying it equally to the grids at both sides of the phase splitter.

This week I am replacing the four paralleled and absurd 1W Vishay Bulk Metal Foil plate resistors to the 5751 plates (in unobtanium 162K values) with regular 3W metal oxide film parts of 150K and 180K to make up approx. the correct value. I am hoping that these are the problem.

Forget dredging through forums. When I have the answer I will link to it here. So far it has been a 4-month nightmare of trying. A valve amplifier technician with over 40 years of experience could not diagnose these amplifiers.

The input stage and phase splitter stages are direct coupled and in order to isolate stages tracks must be cut! The amplifiers were not designed to be serviced IMO.

If your servicing skills do not extend beyond cleaning sockets, are limited to swapping valves and playing around with O-rings which could have been sourced from an O-ring supplier at 1/100th the price, but which do nothing except potentially overheat the valves by depriving the vertical glass envelope of convective flow, swapping interconnects for expensive ones that sound identical etc., then don't even try to repair these amps.

BTW, if you ever change the 6CG7s (phase splitter valves) or even swap them from one socket to another you MUST adjust the AC balance pot and to do that you need a tone generator, a high-power dummy load and a 2-channel oscilloscope! Else you will have high distortion unless you happen to be lucky. People who swear that their phase splitter valve choices are the best have lucked it and it is very unlikely that they are even aware of the AC balance pot.
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Re: Premier 275 Crackling

Post by Ian Millar »

OK seems I can't help you really. I had never heard of a Premier 280 or a Premier 275. Now I see that it was advertised as a "Premier 280" on Audiogon and it looks very suspicious. If it really was a one-off that never went into production, why would it be on the market?

Clearly from the Audiogon photos it is not anywhere near as complex as a Premier Eight so its circuit will be different. It looks like a stereo Premier 140 with the "140" screen printing rubbed off with acetone. If it really was a C-J experiment, only C-J or you will know what's inside it. Perhaps there was a good reason that it never went into production. I wouldn't be at all surprised if it has a Premier 140 PCB with track cuts done by a third party and jumper wires to convert it to mono. I would not believe anything that the dealer had to say about it. Email Lew Johnson and ask him.

My problem with the Premier Eight was the 1W Vishay Bulk Metal Foil resistors at the input stage plates. IMO, poor layout and thermal mismanagement by design and lazy/thoughtless construction were at fault. 230V dc across these in a hot chassis caused them to eventually "go high" and additional shot noise was the result.

My overhaul is here: http://ianamillar.com/blog/ridiculous-v ... -overhaul/

As soon as I have the permission of a couple of people mentioned on the page, I will remove the password protection. If they don't agree then I'll edit them out and remove the protection anyway. Give me a week or two (= say end of July 2013).

I do not envy you your adventure with those things. I hope you got them a LOT cheaper than the asking price because they are worthless. Good luck.
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