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Conrad Johnston LP70s amp 6922 tube upgrades

Hello, I am looking for CJ LP70s owners out there that have experience with the above mentioned amp and upgrading the original 6922 tubes to say 7308's and PQ version tubes! Are there any issues with doing this as I have been told that the JAN spec tubes will not work in the amp??? But I thought the 7308 and the other JAN PQ versions etc would drop right in. Can anyone out there clarify this or tell me of there experience with doing so? many thanks D
fihihifi
mtdking
157 posts
 
There shouldn't be any problems at all. You can Ed at CJ and he will clear it up for you.
dvdhwk
10 posts
 
I use PQ's with no issues at all. Since the 70 is more neutral in its voicing than any cj I've ever heard they tend to have a warming effect in my system.
fihihifi OP
22 posts
 
Many thanks guys I didn't think there should be any issues but someone told me the 7308 wouldn't work that it had too much gain or something. I think it must of been something else other then gain as I thought the output was the same in all of them but some had different heater plate current or something, I haven't heard back from Conrad Johnson yet but I did email them as well.
don_rycroft
4 posts
 
As a corollary to this discussion that there are in fact issues with using at least certain 7308 tubes in the amp. As per Conrad Johnson, the amp was not designed to use those tubes and would cause problems. I have tried old stock Sylvania 7308s and did indeed have problems with them. Don't know the technical cause but be careful when tube swapping. The amps calls for 6922 & 6550's which I have alternated NOS tubes with success.
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