CJ Announces GAT Series 2

LL21

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Although there is a lot of mystery around this change, the performance of the 7DJ8 is exactly the same as the 6DJ8. It is the same tube, only the filament voltage, that has no influence at all in tube operation, is changed. Its temperature is exactly the same. However, as there are many 7DJ8 of good quality flying around people will probably have the opportunity of listening to better quality tubes. In order to use the 7DJ8 the resistor that adjusts the voltage of the filament supply must be changed to change it from 6.3V DC to 7V DC. As the UK mains is on the high side (240V) it should be possible to do it without risking to introduce ripple noise. IMHO the change will be of the same type as putting an ultra expensive 6dj8 Telefunken or similar tube.

Most probably the changes in the GAT series 2 are small, however as it obliges to change the PCB it is labor intensive - they can migrate most of the more expensive capacitors the new board, but probably most other components can not be moved and must be new. But we still do not have the details about it.

thanks and good to know.
 

plurn

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... In order to use the 7DJ8 the resistor that adjusts the voltage of the filament supply must be changed to change it from 6.3V DC to 7V DC. ...

From the information that I have been able to gather, I would suggest that this resister change is not required for original GAT in order to use 7DJ8/PCC88. Not that it is not a good idea, I am just suggesting that it is not strictly required.

Not changing the heater voltage and using PCC88 will not hurt the GAT. In most cases it will be fine for the tube, though there is a chance that for some PCC88 you will not be running the tube optimally, and it could reduce its life. On the other hand, in some cases it might increase its life.

I have read that Conrad Johnson has been supplying Philips PCC88 to GAT owners even before the GAT series 2 was announced. PCC88 is equivalent to 7DJ8, with the same heater voltage specifications.

Also with my ET5, in relation to a problem I have been having, Conrad Johnson support suggested that I might want to experiment with some NOS tubes including Philips, PCC88.

If the GAT is set up like my ET5, the heater voltage is set too high at about 6.58V (rather than 6.3V) which is right near the upper limit of the acceptable range for 6922 (according to the electro harmonix 6922 data sheet - max 6.6V). I think 6.58V is at the lower end of the acceptable range for 7DJ8/PCC88, though I have not found a datasheet that confirms this. It is 6% below 7V.

I have not read about any GAT owners measuring the heater voltage. If anyone has done that, I would be very interested to know the results. My expectation is that it would at about 6.58V like my ET5.

Anyway if people with original GAT would like to try PCC88 without any modifications, rather than pay attention to me, best to get advice from Conrad Johnson directly.

Anthony
 

microstrip

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From the information that I have been able to gather, I would suggest that this resister change is not required for original GAT in order to use 7DJ8/PCC88. Not that it is not a good idea, I am just suggesting that it is not strictly required. (...)

Surely it will not hurt immediately, but we will be operating the tube out of specification. Although data-sheets of the PCC88 are scarce, the Phillips one and information on line suggests that filament voltage should be between 7 and 7.6V. These tubes were thought to be used with filaments operated in series, with a current of 300 mA. Operating the tube at lower cathode temperature can reduce its lifetime and increase noise.

I will look for some PCC88s I have in my tube stock and will measure the transconductance at 7.5 and 6.3V filament voltage - Hicock testers have these two settings.
 

XV-1

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From the information that I have been able to gather, I would suggest that this resister change is not required for original GAT in order to use 7DJ8/PCC88. Not that it is not a good idea, I am just suggesting that it is not strictly required.

Not changing the heater voltage and using PCC88 will not hurt the GAT. In most cases it will be fine for the tube, though there is a chance that for some PCC88 you will not be running the tube optimally, and it could reduce its life. On the other hand, in some cases it might increase its life.

I have read that Conrad Johnson has been supplying Philips PCC88 to GAT owners even before the GAT series 2 was announced. PCC88 is equivalent to 7DJ8, with the same heater voltage specifications.

Also with my ET5, in relation to a problem I have been having, Conrad Johnson support suggested that I might want to experiment with some NOS tubes including Philips, PCC88.

If the GAT is set up like my ET5, the heater voltage is set too high at about 6.58V (rather than 6.3V) which is right near the upper limit of the acceptable range for 6922 (according to the electro harmonix 6922 data sheet - max 6.6V). I think 6.58V is at the lower end of the acceptable range for 7DJ8/PCC88, though I have not found a datasheet that confirms this. It is 6% below 7V.

I have not read about any GAT owners measuring the heater voltage. If anyone has done that, I would be very interested to know the results. My expectation is that it would at about 6.58V like my ET5.

Anyway if people with original GAT would like to try PCC88 without any modifications, rather than pay attention to me, best to get advice from Conrad Johnson directly.

Anthony

I have spoken to Lew Johnson on this aspect several times as i have complained about the GAT being hard on 6922 tubes - especially the cj EH tubes.

You can use the PC88/7DJ8 no problems however the GAT was designed to use 6922's and it has better performance.

I have a few PC88's including Pope and telecfunken. They sound good, but not preferable to the EH 6922's imo.

I then got 2 telefunken E88EC/6922's. End game - they sound absolutely superb and have lasted for over 2 years without failure.

cheers
 

plurn

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May 13, 2016
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Surely it will not hurt immediately, but we will be operating the tube out of specification. Although data-sheets of the PCC88 are scarce, the Phillips one and information on line suggests that filament voltage should be between 7 and 7.6V. These tubes were thought to be used with filaments operated in series, with a current of 300 mA. Operating the tube at lower cathode temperature can reduce its lifetime and increase noise.

I will look for some PCC88s I have in my tube stock and will measure the transconductance at 7.5 and 6.3V filament voltage - Hicock testers have these two settings.

It will be interesting to find out the results.

Regarding "filament voltage should be between 7 and 7.6V", I have been investigating further and it seems that for early Philips PCC88 the heater voltage was nominally specified at 7V (datasheets up to 1958), and later the specification changed to 7.6V (datasheets 1962 and onwards). So I don't think the range is 7 to 7.6, but rather the early ones were 7V (plus or minus some unknown percentage) and later ones were 7.6V (plus or minus some unknown percentage).

They don't make it easy do they?

Anecdotally, people have been using PCC88 in devices designed for 6922 with good results and low noise and long life. In my ET5 they typically stay quiet _much_ longer than 6922, though that is only based on limited samples.

Of the 4 PCC88 I have used, one used tube (purchased as used, not new) went noisy after 1.5 hours, 2 have lasted 1000 hours or a little more and are still good and quiet - just swapped them to try other tubes. The current one is a Philips PCC88 (produced by Electronska Industria in the 60's I think) that is low noise and sounds good and has done 130 hours so far.

The various 6922 tubes I have used have mostly gotten noisy at around 250 to 350 hours. Some at less than 100 hours. Some were used only for a short time because I did not want to damage them due to the cost so it is unknown how long they would last. Taking that into consideration, none have lasted longer than 350 hours for me. Like I said this is just anecdotal, and the amount of tubes is not statistically significant. I could have just had bad luck with the 6922 tubes I used.

What would be interesting to find out is if Conrad Johnson is making any changes to the heater voltage between the original GAT and GAT series 2. I am sure some people that are upgrading would like to use their stock of 6922. If they don't increase the heater voltage, it would allow people to continue to use both types of tube.

Anthony
 

Big Dog RJ

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hey Microstrip,
sorry for the late reply, was still dazed after the several auditions and experiencing the awesome pre-power combo that I certainly find to be the ultimate for me.
The components I'm referring to are the ARTSA (stereo version) and the GATS2. This particular pre-power driving my Quads (very similar series 2912 vs 2905) was sounding absolutely marvellous! Compared to what I was previously using (ACTS2 and Classic 60SE) obviously the ART+GAT match up would be beaten... The ACT2 & Classic 60SE were superb sounding instruments and ample power for me. However, after I actually sat down for lengthy periods and did some dedicated listening to nearly all my favourite LP's and CD's, it was quite clear what this new combination delivers- a remarkable level of realism.

Quad stats are very well known for accurate timbre of instruments and its sound-staging. The depth,soundstage, timbre, imaging and presence can be felt even more at a higher level of resolution and inner detail that I had not experienced with my Quads before. The only amplifiers that I had tried so far to get my hands on, that can match up to the midrange and better it were the Lamm's- ML2 series. I'm not sure if these were the ML3 series but they didn't have dual chassis for that matter nor separate power supplies, just the monoblocks on their own. I do know that they are not new, rather nearly 10 years old, somewhere around the 04/05 models thereabouts, so I was told. They're only rated at something like 8-10 or perhaps 20 the most but full Class A and SET's. They weigh a bloody ton and match quite well with the GATS2. Of course the ARTSA had more power and drive, plus ample headroom but the Quads don't need it. They can be driven too loud in the first place hence the Lamm's were the ideal amps for my listening levels. In the long run these are no longer made, and a new pair would cost a fortune. Therefore, a few years from now I can see myself having the ART + GAT, and so I have embarked on that road... it's a long one but I will get there! Oh good, I have now saved close to a grand... that's a great start isn't it?
Cheers and have a good one, RJ
 

Sunnyboy1956

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hey Microstrip,
sorry for the late reply, was still dazed after the several auditions and experiencing the awesome pre-power combo that I certainly find to be the ultimate for me.
The components I'm referring to are the ARTSA (stereo version) and the GATS2. This particular pre-power driving my Quads (very similar series 2912 vs 2905) was sounding absolutely marvellous! Compared to what I was previously using (ACTS2 and Classic 60SE) obviously the ART+GAT match up would be beaten... The ACT2 & Classic 60SE were superb sounding instruments and ample power for me. However, after I actually sat down for lengthy periods and did some dedicated listening to nearly all my favourite LP's and CD's, it was quite clear what this new combination delivers- a remarkable level of realism.

Quad stats are very well known for accurate timbre of instruments and its sound-staging. The depth,soundstage, timbre, imaging and presence can be felt even more at a higher level of resolution and inner detail that I had not experienced with my Quads before. The only amplifiers that I had tried so far to get my hands on, that can match up to the midrange and better it were the Lamm's- ML2 series. I'm not sure if these were the ML3 series but they didn't have dual chassis for that matter nor separate power supplies, just the monoblocks on their own. I do know that they are not new, rather nearly 10 years old, somewhere around the 04/05 models thereabouts, so I was told. They're only rated at something like 8-10 or perhaps 20 the most but full Class A and SET's. They weigh a bloody ton and match quite well with the GATS2. Of course the ARTSA had more power and drive, plus ample headroom but the Quads don't need it. They can be driven too loud in the first place hence the Lamm's were the ideal amps for my listening levels. In the long run these are no longer made, and a new pair would cost a fortune. Therefore, a few years from now I can see myself having the ART + GAT, and so I have embarked on that road... it's a long one but I will get there! Oh good, I have now saved close to a grand... that's a great start isn't it?
Cheers and have a good one, RJ
RJ
My experience of Quads and CJ is similar. For 7+years I had a CJ pre/power combo driving my 2905s. The results were most impressive with a LP70S and CT5. The CT5 made way for a GAT in 2013. I have a pair of NOS Telefunken CcAs in the GAT and it appears that the tubes CJ uses in GAT2 are not in the same league, at least in terms of cost. I suspect, and this is guess work on my part, the major upgrade in GAT2 over GAT is the NOS tube which is a big leap over the EH 6922.
Cheers
Pradeep
 

microstrip

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RJ
My experience of Quads and CJ is similar. For 7+years I had a CJ pre/power combo driving my 2905s. The results were most impressive with a LP70S and CT5. The CT5 made way for a GAT in 2013. I have a pair of NOS Telefunken CcAs in the GAT and it appears that the tubes CJ uses in GAT2 are not in the same league, at least in terms of cost. I suspect, and this is guess work on my part, the major upgrade in GAT2 over GAT is the NOS tube which is a big leap over the EH 6922.
Cheers
Pradeep

As all cj admirers I would love to know in more detail about the differences between the GAT and GAT2 - considering the upgrade price we can be sure they are a lot more than the tube!

I owned an ACT and later I got the ACT series 2. Great preamplfiers. The differences were mainly in the power supply, but reducing the number of components. The cj upgrade was mainly changing the power transformer and migrating all the expensive components - capacitors and vishay resistors to a new PCB, changing a couple of small capacitors to the teflon type. It was mainly a simplification converting a two stage series supply in a one stage series supply, keeping the same overall capacitance.

Long ago I read cj had the project to develop a GAT amplifier, using a similar topology as the GAT preamplifier (tube + SS buffer). Did you hear anything about it?
 

microstrip

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hey Microstrip,
sorry for the late reply, was still dazed after the several auditions and experiencing the awesome pre-power combo that I certainly find to be the ultimate for me.
The components I'm referring to are the ARTSA (stereo version) and the GATS2. This particular pre-power driving my Quads (very similar series 2912 vs 2905) was sounding absolutely marvellous! Compared to what I was previously using (ACTS2 and Classic 60SE) obviously the ART+GAT match up would be beaten... The ACT2 & Classic 60SE were superb sounding instruments and ample power for me. However, after I actually sat down for lengthy periods and did some dedicated listening to nearly all my favourite LP's and CD's, it was quite clear what this new combination delivers- a remarkable level of realism.

Quad stats are very well known for accurate timbre of instruments and its sound-staging. The depth,soundstage, timbre, imaging and presence can be felt even more at a higher level of resolution and inner detail that I had not experienced with my Quads before. The only amplifiers that I had tried so far to get my hands on, that can match up to the midrange and better it were the Lamm's- ML2 series. I'm not sure if these were the ML3 series but they didn't have dual chassis for that matter nor separate power supplies, just the monoblocks on their own. I do know that they are not new, rather nearly 10 years old, somewhere around the 04/05 models thereabouts, so I was told. They're only rated at something like 8-10 or perhaps 20 the most but full Class A and SET's. They weigh a bloody ton and match quite well with the GATS2. Of course the ARTSA had more power and drive, plus ample headroom but the Quads don't need it. They can be driven too loud in the first place hence the Lamm's were the ideal amps for my listening levels. In the long run these are no longer made, and a new pair would cost a fortune. Therefore, a few years from now I can see myself having the ART + GAT, and so I have embarked on that road... it's a long one but I will get there! Oh good, I have now saved close to a grand... that's a great start isn't it?
Cheers and have a good one, RJ

Thanks. Do you know of anyone mixing cj and Lamm? The topology of the Lamm top preamplifier is similar the topology of the old ART preamplfier.
 

plurn

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May 13, 2016
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...
Long ago I read cj had the project to develop a GAT amplifier, using a similar topology as the GAT preamplifier (tube + SS buffer). Did you hear anything about it?

http://www.audioaficionado.org/conrad-johnson/9814-please-post-some-conrad-johnson-audio-porn-here-12.html#post211054

turntable wrote:
"Remember this from CES 2003. Apparently cj have enough parts to make several pairs.

conrad-johnson GAT Amplifier ($38,000) is the company's first venture into 300B tube amplification. This is the only 300B amplifier that outputs 1,000 watts (not a typo). A low ratio transformer is coupled to a push-pull buffer. This keeps the voltage gain characteristics of a 300B but the current gain of the output buffer stage.
"

conrad-johnson-gat-amplifier.jpg

http://www.audioaficionado.org/conrad-johnson/18863-ces-2013-a-2.html#post439608

Tonepub wrote:
"They couldn't get a reliable supply of the tubes that they wanted to use in the design...

And that's straight from Lew Johnson."
 

LL21

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I remember starting a thread about this legend about the CJ GAT amp...thanks for that...would certainly have been great fun to hear!!!
 

microstrip

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(...)
"Remember this from CES 2003. Apparently cj have enough parts to make several pairs.

conrad-johnson GAT Amplifier ($38,000) is the company's first venture into 300B tube amplification. This is the only 300B amplifier that outputs 1,000 watts (not a typo). A low ratio transformer is coupled to a push-pull buffer. This keeps the voltage gain characteristics of a 300B but the current gain of the output buffer stage.
"
(...)

It is a topology similar to the Ypsilon SET100 amplier - an hybrid with an old Siemens triode at the input coupled to a MosFET buffer using an interstage transformer. However, as long as I remember the solid state buffer of the SET100 was single ended, not push-pull.
 

Big Dog RJ

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ah! that one... yes, have seen it during my travels but never heard it. in fact when I did see this monster before, I thought it was some spare parts from a tank! didn't take much notice at the time.
speaking of cj + Lamm, I do know very few who have this combination but always seem to partner with components alike. I certainly do like the combination VERY much, and that is exactly why I have ventured off into 300B's once again. currently using an integrated of just 8w/ch SE class A from Jas Audio. through the Quads, sounds bloody marvelous! doesn't quite have the extended reach of cj gear overall but my golly that midrange is absolutely captivating to the core! I have set my plans on for an Art but now I exploring new experiences...
The GatS2 no doubt in my opinion is superb as it gets. I still strongly feel sometimes cj power amplification could do with a tad more oomph. The little 8watter puts out drum whacks and strings like the performers are right in front of you. and because most of my listening is near field, I beginning to think that perhaps this output is plenty. will take my time in the long run, no rush whatsoever.
It would certainly be an experience to encounter a cj design with 300B's. now that would get my hands all sweaty.
Cheers to those who are using 300B or SE types, I do understand the joy!
RJ
 

XV-1

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ah! that one... yes, have seen it during my travels but never heard it. in fact when I did see this monster before, I thought it was some spare parts from a tank! didn't take much notice at the time.
speaking of cj + Lamm, I do know very few who have this combination but always seem to partner with components alike. I certainly do like the combination VERY much, and that is exactly why I have ventured off into 300B's once again. currently using an integrated of just 8w/ch SE class A from Jas Audio. through the Quads, sounds bloody marvelous! doesn't quite have the extended reach of cj gear overall but my golly that midrange is absolutely captivating to the core! I have set my plans on for an Art but now I exploring new experiences...
The GatS2 no doubt in my opinion is superb as it gets. I still strongly feel sometimes cj power amplification could do with a tad more oomph. The little 8watter puts out drum whacks and strings like the performers are right in front of you. and because most of my listening is near field, I beginning to think that perhaps this output is plenty. will take my time in the long run, no rush whatsoever.
It would certainly be an experience to encounter a cj design with 300B's. now that would get my hands all sweaty.
Cheers to those who are using 300B or SE types, I do understand the joy!
RJ

Hey Big Dog

easily solved. prem8a's, LP275's or ART have plenty of oomph :D:D
 

Big Dog RJ

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Hey mate, yes that's a definite!
I've heard all of these amps either with an ART pre, ACT2, or GAT- super impressive I must say.

What I was referring to "oomph" perhaps was not the right word/phrase. Sorry about that; infact, as you all are well aware cj amplification whether 45 or 300 watts, all have plenty of oomph. What I'm referring to and is quite hard to explain is this: when I listen to the system at very low to moderate levels, the cj sound is very relaxing and just pure bliss for endless hours- not too bright, nor too harsh, just the perfect sort of balance all round, I guess you could claim "just sounds right!"
I have noticed quite significantly, as you increase levels, this all round balance still remains, virtually no distortion, again very smooth and captivating presence (life-like) and has a superb control of the entire soundstage from top-bottom & sideways with a highly accurate scale. Plus of course that total musicality factor that cj is known for.
All summed up, cj is basically true high-end gear that does come at a cost.

On the other side of the planet, somewhere in China or Hong Kong I think, at a fraction of the cost- we have Jas Audio. Very clever design, superb execution of parts and good workmanship (always improving) but does not have a rich audio design history such as cj, ARC, VTL and the like. However, in terms of value for money- is right up their amongst the top contenders such as Prima Luna, Cayin and other top value brands that are starting to emerge. So what I noticed on my Quads is that in order to get the cj in full action, I do have too turn it up a couple notches on the pre to get the heart pumping, and of course the dynamics are superb along with the details, nuances and layering of everything possible, cj doesn't seem to miss a thing.

On the other spectrum, with the little Jas Bravo 2.2 SE 300B, I noticed once again very significantly that impact on the notes are more prominent even at low volumes. I don't have to turn it up at all, and this suits me just fine since I don't listen to loud at all. Soft to moderate is my preference. On the negative side, when I do turn up the level on the JasA, it starts to get all mushy and not as well layered as the cj gear at all. The bass becomes flabby and the highs not so focused, perhaps it's clipping, running out of steam or just the trait of the 300B don't know...
Overall, I am enjoying this wonderful little amp with the stats and it does something magical with the midband. It can scale up to size and does deliver what I'm after. However, at the end of the day, comparing side by side, forget it, you just cannot compare the JasA with cj- hell no! Therefore, the combination that has given me 110% satisfaction to the fullest from the Quads has been with the ARTsa amp and GAT. Of course to top that off, the GATs2 delivers everything else at even a higher level of what was thought final from just the GAT. To me it's really mind boggling exactly what the GATs2 is doing, whatever it's capable of is astonishing! You really have to experience it to understand its capabilities.

I really don't know whether I would ever be able to afford a GATs2 or even a standard GAT for that matter. However, in terms of power amplification, I do know the ARTsa is definitely worthy and is pretty good value as well, not overly priced in my opinion. Just the right amount of power to drive virtually anything- 140 watts of pure push-pull on tubes I sincerely think is more than adequate for normal listening levels... At the end of the day, who knows I might just stick to the JasA 300B and end up with another 60 watter from cj similar to the Classic 60SE which I just sold. I'm actually waiting to see if cj would ever put out a 300B design- that would probably be my primary choice.
Trust this clears the "oomph" part, and JasA really does not have much oomph at all, rather a more prominent note on the midrange that is delivered well within a small amount of level input, if that makes sense- this is Class A power I guess.
Cheers, RJ
 

microstrip

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Does any one know what brand of the PCC88 conrad johnson are shipping in the CAT2?
 

LL21

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Does any one know what brand of the PCC88 conrad johnson are shipping in the CAT2?

Quote from Myles who has just put his in yesterday after reviewing the Kondo pre: "Looks like the new tubes conrad-johnson are using the GAT Series 2 are NOS Phillips PC88s..."
 

microstrip

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Quote from Myles who has just put his in yesterday after reviewing the Kondo pre: "Looks like the new tubes conrad-johnson are using the GAT Series 2 are NOS Phillips PC88s..."

Thanks for the clue - just bough a few sleeved boxes from Langrex UK. The Telefunken PCC88s from Germany are all gone now - I could only get one last pair a few days ago!
 

rayooo

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I'm new here, but while searching around for info on GAT V2 I found What's Best!

My GAT is out for the update, I'm hoping it'll show up back home later this week! :D
 

LL21

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I'm new here, but while searching around for info on GAT V2 I found What's Best!

My GAT is out for the update, I'm hoping it'll show up back home later this week! :D

congrats and look forward to reading about your thoughts when you get it back!
 

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