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6L6 or KT66 valves.

awkwardbydesign

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I wasn't sure where to post this, so please move it if necessary.

I would like to borrow a pair of 6L6 or KT66 tubes to try in my little "SET of Death" power amp.

I've done the safety mods, and replaced the 6N1 with a Sovtek 6N1P. That was worthwhile, and cheap, so I was wondering if replacing the 6P3P valves would improve it even more. Unfortunately they would cost considerably more than the 6N1P, so if I can try a pair before spending it would be good.

The amp only cost about £180 inc. postage, and is only 5-8 watts, but it sounds quite nice.

I will be at Scalford (easy to spot, eyepatch, cane, and skateboard!), and of course would post them back afterwards.

Can anyone help?

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Jazid

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I can lend you a pair of 6L6 or 6P3C-E. PM me and we can sort summat out, I have quite a few and would also be happy to do a sell or return on a pair if an indication of budget were to be given :)

 

Valvebloke

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Did you have any particular KT66s in mind ? IME the very reasonably priced Sovteks (£20 apiece from HotRox although I see they're currently out of stock) are perfectly serviceable. I usually buy them when I need them but I may have a couple of low-mileage few-year-old ones somewhere if you want to try them ?

VB

 

awkwardbydesign

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Did you have any particular KT66s in mind ? IME the very reasonably priced Sovteks (£20 apiece from HotRox although I see they're currently out of stock) are perfectly serviceable. I usually buy them when I need them but I may have a couple of low-mileage few-year-old ones somewhere if you want to try them ?VB
Thanks, can I pick them up at Scalford? Matt (AGrail) has lent me some GEC KT66s from a Quad 2, but they are probably outside my price range as keepers!

 

Valvebloke

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Yup. I've probably got some 'GEC look-alike' Shuguangs too. I'll try to remember to bring them as well. They're a bit fierce on the heater current. Like all 'proper' KT66s Matt's GECs will pull 40% more than a 6L6, but the Shuguangs might be another 10% hungrier. If your power transformer is very marginal you might want to bear that in mind.

VB

 

old_school

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I tried a bunch in my Leak Stereo 50, including grey glass GECs and Tung Sol 5881s, but ended up with the Russian 6p3s-e coin-based valves in the end. The KT66s drew a bit more current, and I found the Russian jobbies seemed to handle the bass a bit better. Still worth trying though, as your amp may handle them differently, but the Russian valve have real VFM.

 

awkwardbydesign

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Yup. I've probably got some 'GEC look-alike' Shuguangs too. I'll try to remember to bring them as well. They're a bit fierce on the heater current. Like all 'proper' KT66s Matt's GECs will pull 40% more than a 6L6, but the Shuguangs might be another 10% hungrier. If your power transformer is very marginal you might want to bear that in mind.VB
Ah, I should have checked that! I suspect everything is marginal in this amp. The case had no bottom (for better ventilation!) and it wasn't earthed! Which is why I call it the SET of Death. I changed the look of it, and it's intended for computer duties eventually, so vast expense is foolish. Extra current drain would be a bad idea, I suspect.



 

awkwardbydesign

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Thanks to everyone for their help. I will PM those I haven't got to yet. :notworthy:

I also realised that the Sovtek 5AR4 from the Cyber 222 pre (replaced by a Mullard GZ34) will fit in place of the 5Z4P. At least it hasn't blown up yet!

So I've replaced the wood sides, all the sockets, Alps pot, changed all the valves, made a bucking transformer, and will try reducing the NFB. Still the same amp, of course! Just need to get the triode schematic now. Lol. Transformers next?

Seriously though, it's a great little toy to play with, and cost less than £200 all in. So far. :nerves:

Sound wise, it doesn't major on bass slam (surprise!), and the treble is a little down, but less NFB apparently helps with that. It can get a bit confused with complex music, and won't go loud, but it has a taste of that SE magic.

I started on motorbike mechanics like this, learnt on an old Moto Guzzi, and ended up building a complete bike (CB250 K4 classic racer).

 

awkwardbydesign

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If you're a good boy I will let you have alook at the wiring in mine, running 6l6 in triode mode, see you at scalford
I have been a good boy, Santa. Just not all year.

​Thanks.

 

Valvebloke

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Ah, I should have checked that! I suspect everything is marginal in this amp. The case had no bottom (for better ventilation!) and it wasn't earthed! Which is why I call it the SET of Death. I changed the look of it, and it's intended for computer duties eventually, so vast expense is foolish. Extra current drain would be a bad idea, I suspect.
Quite a few modern 'KT66s', including the Sovteks IIRC, actually have 0.9A heaters, which is the spec for the 6L6. I guess it's then a matter of opinion whether they are really KT66s or are sheep in wolves' clothing, so to speak.

VB

 

awkwardbydesign

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I'll have to stick a meter on it and see if the voltages are holding up. I use computer fans to cool everything, so the transformer isn't hot, but checking would be good!

The GEC KT66s are definitely better than the stock 6p3ps (surprise!), but they are huge! Need bigger handles.

 

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