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136.1.1.103
In Reply to: RE: 6AH4 tube for DIY Preamp posted by Freo-1 on March 31, 2014 at 17:40:08
good to hear of their sonics. I have underway a balanced output pre built around them. LTP with SE input to drive an active cross over. high voltage, and high current and a lot of heat made from nearly 20 Watts dissipated in their resistive loads. AC heaters to start with, but room and voltage to try an L-C filtered DC supply...:)
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
Follow Ups:
Lots of good feedback.
The 6CK4 is another good candidate for a line stage. I just really liked the specs of the 6AH4, and the sonic results were even better than I was hoping for.
The 26 tube looks interesting. May have to look int that. For now, will be anxiously awaiting the high end finished 6AH4 preamp.
"What this country needs is a good 5 watt amplifier!" (Paul Klipsch)
You're right about the 6CK4...but its heater current is a wee bit higher. I don't recall if its base is the same as the 6AH4, but it can't be a very big job to change it so as to try the 6CK4 in a 6AH4 circuit( and what I have in mind will be able to accomodate that ).
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
I've used the 6AH4 in a couple of builds - a great tube!
It sounds best at higher currents...but, it was too noisy with AC on the filaments.
Have never tried the 6CK4 - anyone have some recommended op points?
Jim
I'm running a pair of 6ck4s as output tubes (SE) in a junk-box amp. They sound pretty good, and are very simple to implement and drive. I'm running them at about 250v and 40ma, they bias up similar to a 46. Somewhere i read that they can take higher voltages easily, but I have yet to try this.
Jim, could you define, 'higher current' please?
depending on the response, it may be I will go towards an OPT design from Intact. The little LTP 6S4P-EV rig I have built around BOH-2's is quite nice, but with 6AH4's I would not need the step-down. Using an OPT would also make the B+ significantly lower; right now I have in mind B+ OTO 3x idling plate voltage with resistive loads. With the prototype circuit, it was more like 4x with 12B4's.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
180 vpk, drawing approx 24 mA - bias -15 v.
Each plate loaded with paralleled pair of 5k6 12 W Mills resistors.Cap-coupled output using a pair of nickel grid chokes...input uses 50k Goldpoint attenuators.
Edits: 04/02/14 04/03/14
That is do-able..:) I had in mind 10k late loads, and about 30 mA current and comparable plate voltage. Takes a near 500V supply( I have an L-C set up that delivers about 480 so I think I'll keep using it ). Will likely run the heaters on DC between ground and -6.3 negative and use that for the tail CCS as well. That will keep CCS dissipation manageable...:)
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
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