Well I've come full circle now. My original post here was asking about a schematic for a Sunn Sceptre with mid boost. Now I need to buy a pair of 6550s for the Sceptre and would appreciate some recommendations on some decent current production tubes. The last I bought were GEs back in the '70s.
I have tried some 6550 recently in 4 different builds:
Plexi + Hoffman's hot switch, Orange 80 (using both P.I. - A.C. concertina and D.C. concertina), *umble style O.R., Hoffman AB763
I tried the following manufactures:
G.E. 6550A, Winged "C" 6550, China 6550A, sovtek 6550 metal base, JJ KT88/6550.
G.E. was used as reference for subjective listening test.
Between all them, G.E. was clearly the most clean tube, offered highest headroom and started showing PWR tube distortion when volume pots were really cranked, almost on max. setting..
Winged "C" was really clean sounding, but not so sterile for lack of better word.. showed PWR distortion earlier on dial. Had more sustain between the tested tubes and developed mids which cut thru the mix very efficiently. A real tone partner in the sense of playing along with you, not against....
China 6550A was a real deception, I got a 'good deal'
on a quad...they were supposed to be 'matched' and showed discrepancies solid enough , like 10% from one to the other, but figures went 40% within less then 24h of burning. White paint turned brown within less then 2 hr. Fortunately, seller refunded me and I got a pair of G.E. 6V6 GTA, 1 ECC83 from Philips - dutch made - and 3 5Y3WGTA blackplates from Philips too
... Tubes lacked punch, high freq. details and sustain...nothing good to say about it... and what made me interested on these tubes was the fact that ching-lings claimed to use G.E. original plans...
go figure...
Sovtek 6550 metal base hold strong on current tolerances, had a very strong punch, but lacked something... We thought it would stay too clean and when distortion showed, it was harsh and lifeless...
JJ KT88/6550 was another deception... a quad also... very strong bass content, nice treble response and just the right amount of mids... however, tube current went freak and all over the place within less then 4 hours of use..
it sounded fine, but went south just too soon and my pocket tells me that such a high price tag tube should at least last a month...
All tubes were tested on all the mentioned amps with 4 different guitars and 2 different cabs - loaded with different speakers -
Bias was corrected so that tubes stayed around 70% max condition, althought they seemed to handle it when bias was a bit hotter...
As far as I can tell, Winged "C" is the best sounding for the money and I have 5 amps running them for 3 years now without any negative feedback from users. They are handling the abuse just fine...
Of course plate voltages varied a bit, but not that much o become a real consideration.. lowest plate voltage was ~ 380VDC on plexi build and highest was on Orange 80 ~480VDC.. tubes showed the basic behavior and sound regardless of which amp was up for the test.
I would really like to try Tung Sol 6550 black plate coke bottle to know why people freak sooo much at them....
All I have typed here were impression we had and were written down. I had tested them with 2 guitar players I know and they play very fine. Of course we know it is all subjective but my intention is not to make your mind on a particular brand, just offer some perspective and share my impressions...
Hope this helps
Best regards
Rzenc
Topic: 6550 advise (Read 6416 times)