i`ve been think about building a tube power amp lately, i`ve decided on a 6L6 since i`m looking for punch bass and nice mids (for me to further apreciate dire straits and eddie van halen)
i`ve seen alot of circuits for the 6L6 but most of them being designed for guitar use.
whats a good circuit you guys recommend? i`m hoping for about 20watts.
Thanks in advance
i`ve seen alot of circuits for the 6L6 but most of them being designed for guitar use.
whats a good circuit you guys recommend? i`m hoping for about 20watts.
Thanks in advance
hacknet said:
Depends on the output configuration. I don't have my RCA tube manual at hand, but I think you could get 40-50W in pentode. If someone else doesn't chime in with the number, I'll find it sometime today.
A Williamson with 6L6s and a 6600 ohm plate-plate output transformer would make a very nice 18 watt triode amp.
UL-triode switch
You can, but think VERY carefully about insulation requirements in the event of switch failure and the stray reactances in wiring it up. I'd recommend doing it as a hardwired option, moving a wire or a jumper on a terminal strip. You can't do a rapid A-B test, but you can still change it over in a few minutes and you avoid a lot of complication.
If you're new to the tube thing (and even if you're not!), do think about safety when probing around an amp that's been switched on in the recent past- capacitors can hold a lethal charge for hours after the unit is switched off.
You can, but think VERY carefully about insulation requirements in the event of switch failure and the stray reactances in wiring it up. I'd recommend doing it as a hardwired option, moving a wire or a jumper on a terminal strip. You can't do a rapid A-B test, but you can still change it over in a few minutes and you avoid a lot of complication.
If you're new to the tube thing (and even if you're not!), do think about safety when probing around an amp that's been switched on in the recent past- capacitors can hold a lethal charge for hours after the unit is switched off.
The output transformer as designed and specified by Williamson was superb. The questionable LF stability was mainly due to an oversight on Williamson's part (he couldn't be perfect everywhere). David Hafler fixed the LF problem by increasing the value of the coupling capacitors to the output valves.
If you look at the thread on Leak Stereo 20 there should be my circuit for EL84s. I also use this identical circuit for 6L6 in UL PP on a pair of Leak TL25 chassis, except I'm currently using a 500 ohm cathode resistor on each 6L6 which is loafing along, but I have a small room. It's a simple circuit with few parts and it sounds very nice. This will get you going with very little effort. SY's comments about safety are, as always, worth reading carefully.
Andy, IIRC, the TL25 was a Williamson but with a pentode input?
What are you getting for power out of that?>
Hi there SY - Well, this pair of monobloks started off as rusty chassis with no transformers so the TL25 is rather nominal, although they do look quite nice now. I used a 6.6KOPT from Danbury with the beefy core (ex-Maplin part) which is quite good. I have about 20v on the grids of the 6L6s and 500 ohms cathode resistor so about 40mA. Loafing along. Sounded nice so I didn't carry on changing values. My idea was to use a quad of 7519, which I have ready. I got sidetracked into testing out loads of 6J5s and 6C5s in the front end, which has been good fun. Nice tubes in the archives of the 6J5, and much cheaper than 1940s 6SN7s for sure - plus you get the round plates if you like. Just listening to some Brimar ST shape 6J5 round plates as we speak. Nice! That old '40s smooth silky sound. Before those I was groovin' to some RCA metal 6C5s - surprisingly nice too. I've gone single triode for the front end - these old tubes are just too much fun.
What are you getting for power out of that?>
Hi there SY - Well, this pair of monobloks started off as rusty chassis with no transformers so the TL25 is rather nominal, although they do look quite nice now. I used a 6.6KOPT from Danbury with the beefy core (ex-Maplin part) which is quite good. I have about 20v on the grids of the 6L6s and 500 ohms cathode resistor so about 40mA. Loafing along. Sounded nice so I didn't carry on changing values. My idea was to use a quad of 7519, which I have ready. I got sidetracked into testing out loads of 6J5s and 6C5s in the front end, which has been good fun. Nice tubes in the archives of the 6J5, and much cheaper than 1940s 6SN7s for sure - plus you get the round plates if you like. Just listening to some Brimar ST shape 6J5 round plates as we speak. Nice! That old '40s smooth silky sound. Before those I was groovin' to some RCA metal 6C5s - surprisingly nice too. I've gone single triode for the front end - these old tubes are just too much fun.
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