Is the GAT / ET5 hard on tubes?

[microstrip]

I would be very interested in knowing the differences between the LP275m and the new ART amplifiers - except for the type of input tube and driver they look very similar.

[ronenash]

They have identical output topologies. The input and driver stages are different. In the ART CJ moved to a very simple and basic input stage that includes one triode M8080 for input gain stage and one 6H30 used as a phase splitter. They use the same topology in all their current amplifiers (Classic, LP125 and ART).
The LP275 used parallel triode sections for gain and phase splitter. Apparently this design was dumped by CJ because it resulted in losing some of the purity of the sound and made the amplifiers sensitive to tubes that have un-matched triode sections.

I think over the years CJ has made the power supply sections of their amps more sophisticated and simplified the actual amplification circuits to the bare minimum. Today ~80% of the parts in the their amplifiers are in the power supply. This is very noticeable in their preamps, even more so than the power amps.

[Myles B. Astor]

Originally Posted by microstrip

I would be very interested in knowing the differences between the LP275m and the new ART amplifiers - except for the type of input tube and driver they look very similar.

The only difference between the two amplifiers is the driver stage. But apparently the change in impedance makes for a big sonic difference

[microstrip]

Thanks. I could see that the LP275 used three 6922. This means that cj abandoned the 6h30 in the gain section for the GAT, replacing it with a 6922 and started using it in the driver section of the ART. All in the name of better sounding music.

[plurn]

Originally Posted by turntable

One more cj 6922 has just gone noisy. This one barely lasted 2 months:tears:

Any ideas guys? Fwiw - my unit is 220-240 export unit and Australia is 240 vlts sometimes up to 250vlts

If this does not improve, I will be forced to look at other pre amp alternatives.

Cheers

Hi Turntable,

Did you ever find a way to resolve this issue - or are you still going through tubes like tic tacs?

I am also in Sydney with the same high mains voltage levels and was considering getting one of the current cj preamps but this is quite a worry.

Some ideas:

I have seen some cj equipment that says 240v (not gat) and others (like your gat) that says 220-240v. Perhaps with the export gat they are wiring them up for 220v instead of 240v? cj might be able to advise on this - though I expect they would have mentioned something about this last time you contacted them if there was anything to it. I understand on some of the other cj devices this is easily changeable by a technician by changing where some of the wires are soldered in the power supply. I don't know if the power transformers in the gat support this.

Not sure if it would change the sound quality, but it might be worth trying a 240v to 220v step down transformer (which drops 240v to about 220v and so would drop 250v down to about 230v). Don't know if I am allowed to link to one but they are sold in Australia by a respected company - search for european step down 240-220V. Various wattages available. Would be a shame if something like this is needed for a device that retails and is supported in Australia though.

Were you ever able to measure the tube heater voltage? I am somewhat handy with a multimeter if you would like some assistance with this.

Anthony

[ronenash]

Anthony,

The heater voltage supply in the GAT/ET5 is regulated so a change in line voltage will not effect it. If the line voltage will be a bit higher it will only cause the regulator to dissipate a bit more heat.

I suspect the actual tubes were at fault in this case. EH had a whole manufacturing series that turned noisy after a few hundred hours of use.

It would be good to hear form turntable how this turned out.

Ron

[plurn]

Hi Ron,

Good to know about the regulator - thanks.

Regarding the EH tubes, I got the impression it was an issue for any of the tubes Turntable tried - though not sure if he tried anything other than EH tubes. This is a long thread so I don't quite remember.

Hoping to hear from Turntable too. Would be good if the issue is resolved.

Anthony

[turntable]

Hi Guys

Did the noise issue with the GAT get resolved - well no.

Just tonight another EH 6922 went noisy. I am now down to my last 2 cj EH 6922's.

I have gone through I think about 12.

I was thinking about getting a pair of Telefunken E88CC/6922's but with several months per set, probably not great value.

How does Cryo treatment on the tubes do for reliability and sound?


BTW, Lew did tell me a while back that the plate voltage should be around 85 Volts (say + or - 5 Volts), and the cathode very close to 2.1 volts. If the voltages are right, then the tubes are operating correctly.

I do need to take my GAT to the the tech to get this measured now that I am down to my last two tubes.

cheers

[Myles B. Astor]

Originally Posted by turntable

Hi Guys Did the noise issue with the GAT get resolved - well no. Just tonight another EH 6922 went noisy. I am now down to my last 2 cj EH 6922's. I have gone through I think about 12. I was thinking about getting a pair of Telefunken E88CC/6922's but with several months per set, probably not great value. How does Cryo treatment on the tubes do for reliability and sound? BTW, Lew did tell me a while back that the plate voltage should be around 85 Volts (say + or - 5 Volts), and the cathode very close to 2.1 volts. If the voltages are right, then the tubes are operating correctly. I do need to take my GAT to the the tech to get this measured now that I am down to my last two tubes. cheers

My first two tubes lasted forever. Second pair, not so long before went hissy. New pair's been just fine. I think the issue was with the Ruskie tubes not cj gear. I think they were selling crap. Have you bought a pair recently?

[turntable]

Originally Posted by Myles B. Astor

My first two tubes lasted forever. Second pair, not so long before went hissy. New pair's been just fine. I think the issue was with the Ruskie tubes not cj gear. I think they were selling crap. Have you bought a pair recently?

Hi Myles

I have been living off my spare set of ART tubes as I had 10.

Have you bought the new ones from cj or just garden variety from tube store or similar?

Cheers