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Title: OTS with KT88? Post by: JD0x0 on March 31, 2009, 10:38:44 PM Can an OTS use KT88 power tubes? With biasing ofcourse.
Are there any simple mods to makes this work? Title: Re: OTS with KT88? Post by: JohnE on March 31, 2009, 11:55:37 PM I don't think it would be a good idea. The KT88 is designed to operate with a plate voltage of 600-800 max. I believe the OTS is 425-450. The current output transformer, etc. would not support KT88s.
Also my personal experience is that there is little reason, other than to satisfy your curiosity, to do a conversion. Several years ago, I did a fairly major overhaul of a '66 Super Reverb (this is before I knew that they would be such a collectors item). Since I was replacing most of the components I decided to upgrade the output transformer (50W vs. 40W), etc. to support EL34s. The net result was a much louder amp, that still sounded like a Super Reverb. Contrary to what most people think, output tubes do not change the tone of an amp that much. On the Super Reverb, changing brands (e.g., JJ to Sovtek) seems to change the tone as much as 6L6 to EL34. Title: Re: OTS with KT88? Post by: JD0x0 on April 02, 2009, 04:41:04 AM hmm i was just thinking the added headroom would be nice plus KT-88s get awesome bass response.
How about 6550's or other higher headroom tubes? Title: Re: OTS with KT88? Post by: JohnE on April 02, 2009, 09:32:13 PM hmm i was just thinking the added headroom would be nice plus KT-88s get awesome bass response. 6550s and KT88s are equivalent. Also after sending the post above I read the link for Eurotubes in one of Hywel's posts on biasing. In there, Bob was talking about substituting 4 KT88s for 6L6s in a Twin and how good it sounds. I think if you email Bob at Eurotubes and give him the amp specs he can probably provide some valuable guidance on this subject.How about 6550's or other higher headroom tubes? I think I mentioned that I set up my super reverb to run EL34s. If I want clean headroom at high volume with that amp I use JJ KT77s (amazing tubes) and a 12AT7 in the PI. The amp breaks up at about 4 with a 12AX7 and humbuckers, but stays clean up to 8 with the AT7. Title: Re: OTS with KT88? Post by: JD0x0 on April 04, 2009, 02:57:47 AM I found this on the webber site
6550 - 35W Hot (70%) Avg (60%) Cool (50%) 400V 61mA 53mA 44mA 425V 58mA 49mA 41mA 450V 54mA 47mA 39mA 475V 52mA 44mA 37mA 500V 49mA 42mA 35mA 525V 47mA 40mA 33mA 550V 45mA 38mA 32mA 575V 43mA 37mA 30mA 600V 41mA 35mA 29mA for reference heres EL34 and 6L6 EL34 - 25W Hot (70%) Avg (60%) Cool (50%) 300V 58mA 50mA 42mA 325V 54mA 46mA 38mA 350V 50mA 43mA 36mA 375V 47mA 40mA 33mA 400V 44mA 38mA 31mA 425V 41mA 35mA 29mA 450V 39mA 33mA 28mA 475V 37mA 32mA 26mA 500V 35mA 30mA 25mA -------------------------------------------------------------------------------- 6L6GC - 30W Hot (70%) Avg (60%) Cool (50%) 300V 70mA 60mA 50mA 325V 65mA 55mA 46mA 350V 60mA 51mA 43mA 375V 56mA 48mA 40mA 400V 53mA 45mA 38mA 425V 49mA 42mA 35mA 450V 47mA 40mA 33mA 475V 44mA 38mA 32mA 500V 42mA 36mA 30mA Title: Re: OTS with KT88? Post by: JohnE on April 04, 2009, 03:57:33 AM I am familiar with that chart. I built a Weber Bassman kit about 3 years ago. I would still check with someone knowledgeable before I started running KT88s in my OTS.
Title: Re: OTS with KT88? Post by: JD0x0 on April 04, 2009, 05:54:09 AM i'll probably bring it to a tech when i get my hiwatt recapped
Title: Re: OTS with KT88? Post by: hywelg on April 04, 2009, 09:58:42 AM I found this on the webber site Immensely useful thanks. |