kchapdaily
100+ Head-Fier
- Joined
- Apr 19, 2011
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sounds good! if i ever get around to it ill be sure to let you know how it sounds
i am a tube newbie, want to build this as a first tube project. whats a good source for these tubes. which tubes are good, I see russian, chinese etc on ebay. any recommendations? dont want to spend too much though. any particular brand i should be looking at.
I'll asume you're talking about 12AU7 tubes. An ultra quick Google search yielded this. It also gave links to www.tubeworld.com, www.thetubestore.com and www.tubedepot.com. Remember, Google is your friend.
As to brands, pretty much any 12A_7 you get from those places will do. My own 12AU7 build was done with a couple of JJ tubes from tubedepot.com. I also tried a couple of new 'Mullard' (Russian made) and Sovtek 12AX7 tubes.
Your local musical instrument shop might also carry the Sovtkek 12A_7 tubes as they're popular for guitar amplifiers.
Good luck with your build.
cheers!
Actually I am not sure which tube i should go for, as long as its low voltage. I will go with whatever recommendations I get here as I am a total tube newbie. Yes, google is a friend as long as you know what you are looking for.
The amp design is low voltage, and there are several tube options to implement it:
- 19J6 - (if you can find any) this is the tube used in the original design by Mr Millett
- 12SR7 - details posted by user Logistic in this same thread
- 12A_7 (usually 12AU7) - details start with this post.
- 17EW8 - same pinout as the 12AU7 build, only a couple resistor values change.
Any of them will do nicely, I recommend you pick the one that is the easiest/cheapest for you to get.
cheers!
@the_equalizer: quick question. im putting together my bom for a ccs for my 19j6 ssmh. would a value of 1.2Kohm for RA8 and a value of 12Kohm for RA9 be alright? that should give me a current of about .542mA through the 19j6. also, is it ok to use the same transistor you selected? or will any pnp bjt transistor with the right tolerances be ok?
also, what value trimmer would be good for adjusting the bias of the tubes?
i am also concerned that this will constrict the use of my volume pot. with a stock build and my hifiman he-4's, i already have limited use of the volume pot. should i put some additional resistance between the pot and the input for each channel? if so, how would i go about calculating these values?
so i opened up my amp today to measure the cathode bias resistor current, resistors 5 and 11. one channel reads about 2mA, the other reads 1.21mA. now i am a bit worried that the values are not closer to the .5mA. are there any other values i can measure to check if it is functioning correctly? could this be because i used .22uF caps at C2 and C4 and 220uF caps at C1 C3 and C5?