KT77 vs 6550 tubes

[witeter]

So...looking to revalve my JSX soon-i always like trying different stuff out so thought about either going with KT77s or 6550s-my local tech can fit me with either-so thoughts? pluses? minuses? cheers!

[darkbluemurder]

Pursuant to the schematic, the JSX comes with EL34 tubes. This is good news for your intended tube swaps as both the KT77 and the 6550 have the same heater current as the EL34. A swap to KT77 should be straightforward - only a bias adjustment should be needed. For 6550, some minor circuitry changes are recommendable as to not exceed the maximum g1 resistance published in the data sheet (exceeding maximum g1 resistance can shorten the useful tube life).

I cannot comment on the sound as I have never played KT77s, and it is too long ago now that I had an amp to which I had 6550s fitted.

Cheers Stephan 

[witeter]

Thanks Stephan, yes the tech would make the adjustments necessary to install 6550s if needbe. Just hoping to get peoples experiences of the tubes to help me decide :-)

[HTH AMPS]

I've listened to your music and 6550s all the way, tighter bottom end and loads of chunk.

[jpfamps]

I was initially quite excited when JJ started making KT77s (I expect I should get out more.....) as I thought this would be an interesting valve to build an amp around.

However, I've been quite disappointed with the results we got from using the JJ-KT77; we never got the amp we were using it in to sound quite right (although this could be incompetence in our behalf).

We weren't sure whether it simply that the JJ-KT77 didn't sound good, or that the KT77 wasn't a great valve for guitar amps. Up to this point the only other amp I'd heard KT77s in was a 70s Hiwatt, and much as I admire the build quality of Hiwatts, I've never really been bowled over by the sound of them.

Golden Lion now make a KT77 in addition to JJ, but I've not had a chance to A/B. I've only heard the GLs in a Burman amp; again not an amp whose sound I particularly like (sorry HTH!!).

On the other hand there are a ton of amps with 6550s in that really like, so I would endorse HTHs recommendations.

[Dmoney]

I can't remember fully, but I think when I looked at the JJ KT77 datasheet and compared it with the EL34 and 6L6GC it seemed to have a lot in common with the 6L6GC (apart from heater current draw) as apposed to the EL34. I might be wrong though.

[HTH AMPS]

I was initially quite excited when JJ started making KT77s (I expect I should get out more.....) as I thought this would be an interesting valve to build an amp around.

However, I've been quite disappointed with the results we got from using the JJ-KT77; we never got the amp we were using it in to sound quite right (although this could be incompetence in our behalf).

We weren't sure whether it simply that the JJ-KT77 didn't sound good, or that the KT77 wasn't a great valve for guitar amps. Up to this point the only other amp I'd heard KT77s in was a 70s Hiwatt, and much as I admire the build quality of Hiwatts, I've never really been bowled over by the sound of them.

Golden Lion now make a KT77 in addition to JJ, but I've not had a chance to A/B. I've only heard the GLs in a Burman amp; again not an amp whose sound I particularly like (sorry HTH!!).

On the other hand there are a ton of amps with 6550s in that really like, so I would endorse HTHs recommendations.

No needs to apologise to me Frank, Burman are Newcastle based (i.e. local to me for those who don't know), but I'm not particuarly fond of them either.  Hiwatts are definitely acquired taste too, I do like them however but you need to pair them up with Fanes and also crank the hell out of them, imo.

[witeter]

Sorry for the late reply guys-ive already ordered a quad of KT77s, to be installed next week, I will report back on my impressions! :-) thanks for your help and advice