New/old prospective DIYer Looking for plans/info/article on constructing a minimalist Mono preamp with PS for a single Dynaco Mk III (2 x 6550s, 5AR4, 6AN8 ) amplifier.
Ideally using 1 or 2 12Ax/u/t tubes and/or EF-86, and a 6X4 rectifier (I have a bunch of those).Phono preamp for magnetic cart, input for CD player, Volume pot. No tone or balance controls.
Not sure if this is adequate info, so please excuse my total lack of knowledge in this realm.. but I can solder! lol
Never built anything except a Heathkit kit amp a very long time ago, like to get back into it, with a simple project. Thanks!
Roger in NY
Ideally using 1 or 2 12Ax/u/t tubes and/or EF-86, and a 6X4 rectifier (I have a bunch of those).Phono preamp for magnetic cart, input for CD player, Volume pot. No tone or balance controls.
Not sure if this is adequate info, so please excuse my total lack of knowledge in this realm.. but I can solder! lol
Never built anything except a Heathkit kit amp a very long time ago, like to get back into it, with a simple project. Thanks!
Roger in NY
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How much gain do you need? A 12AX7 will have a tremendous amount of gain, and may not be needed. a 6SN7, 6CG6/6FQ7, or 12AU7 may be plenty.
He has a mono system. Why double the parts?
With a mono line input, use two series 10k resistors for summing the CD channels.
You can parallel the stereo cartridge outputs directly, using a 23.5k load resistor.
Yes, it's for using a Dyna Mk III as a center channel amp for a ADS 780 speaker, with ADS L-10s on each side with output from a Scott 222d pp EL84 stereo amp, CD player, and DuaI 1009 & Shure M95ed MM cart. I'd need to combine stereo inputs to the center channel
I could just buy a Dyna PAM-1 and be done with it, but this would be much more fun, being retired in my 70s I need a challenge! My last kit project was in 1964!
I have tons of 12AU7s, ATs, also 6SL7s, 6SN7s. For PS I have 6X4s, 5Y3GT, 5U4s. Sockets for the above and an unused Budd aluminium chassis, left to me with the tubes and sockets by my uncle an IBM EE and Ham guy, now a
silent key: W2DXJ.
Thanks for help!
Roger in NY
I could just buy a Dyna PAM-1 and be done with it, but this would be much more fun, being retired in my 70s I need a challenge! My last kit project was in 1964!
I have tons of 12AU7s, ATs, also 6SL7s, 6SN7s. For PS I have 6X4s, 5Y3GT, 5U4s. Sockets for the above and an unused Budd aluminium chassis, left to me with the tubes and sockets by my uncle an IBM EE and Ham guy, now a
silent key: W2DXJ.
Thanks for help!
Roger in NY
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However:
1) Each of the Shure coils should have 47k in parallel with it, plus the mfr spec load capacitance of 400pF - 500pF.
2) The Shure left coil has a ground tab on its negative (blue) pin. Make certain this pin is connected to ground.
3) Connect the Shure pins white and green together and nowhere else. Take the mono summed audio output from the red pin.
Here is a classic, updated RCA tube circuit. Highly recommended.
http://www.valvewizard.co.uk/phonopcb2.html
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Thanks is that in RCA Radiotron Designer's Handbook 4th Edition? I have that somewhere in the basement,
don't know why I didn't think to look there... well, actually I do: old age! lol
Roger in NY
(go Bills!)
don't know why I didn't think to look there... well, actually I do: old age! lol
Roger in NY
(go Bills!)
The original circuit is from one of the RCA tube manuals. Not sure if it's in the Radiotron.
I'd recommend the updated circuit if you don't mind the fet buffer, though you could also
use a cathode follower instead.
http://www.tubebooks.org/tubedata/rc30.pdf
I'd recommend the updated circuit if you don't mind the fet buffer, though you could also
use a cathode follower instead.
http://www.tubebooks.org/tubedata/rc30.pdf
I see that some of you have tried to steer away from the original poster's request.
Back to the original request:
It sounds like his system is already a Stereo system; now he wants to add a combined L + R center channel.
Can not parallel connect, and can not series connect the stereo cartridge, or you get 3 channels of mono (the L and R stereo channels are no longer stereo).
Just use resistors to combine L and R to get L + R for the 'mono' center channel preamp (The resistors to combine L and R signals have to be done after the phono preamp output).
Using resistors right at the cartridge output will ruin the channel separation of the cartridge.
Just my opinions.
Back to the original request:
It sounds like his system is already a Stereo system; now he wants to add a combined L + R center channel.
Can not parallel connect, and can not series connect the stereo cartridge, or you get 3 channels of mono (the L and R stereo channels are no longer stereo).
Just use resistors to combine L and R to get L + R for the 'mono' center channel preamp (The resistors to combine L and R signals have to be done after the phono preamp output).
Using resistors right at the cartridge output will ruin the channel separation of the cartridge.
Just my opinions.
rayma,
How much clarification do you need?
"Yes, it's for using a Dyna Mk III as a center channel amp for a ADS 780 speaker, with ADS L-10s on each side with output from a Scott 222d pp EL84 stereo amp, CD player, and DuaI 1009 & Shure M95ed MM cart. I'd need to combine stereo inputs to the center channel"
How much clarification do you need?
"Yes, it's for using a Dyna Mk III as a center channel amp for a ADS 780 speaker, with ADS L-10s on each side with output from a Scott 222d pp EL84 stereo amp, CD player, and DuaI 1009 & Shure M95ed MM cart. I'd need to combine stereo inputs to the center channel"
Use an op amp to sum the stereo channels to maintain stereo for the main amp and feed the summed mono to a 6922 or 12au7 tube that will be able to drive the amp. The op amp signal feeds the volume pot > tube > mk amp
Or, to keep it all hollow state, use a 12a*7 as a mixing cathode follower buffer instead of the op-amp.
The signal paths are common from source to volume control, then diverge.
Mono signal path would be: source > volume control > buffer > mono amp
Stereo signal path would be: source > volume control > stereo amp
You have to build a full stereo phono pre-amp anyway - treat that as just another source. In built format the phono pre-amp, volume control and buffer can be on a single chassis, or up to three separate chassis.
You got it... I've had several '58 DeSotos, hence the name. It works for tubes too!
I've got that pic somewhere in one of my Mopar books, thanks for posting!
I've got that pic somewhere in one of my Mopar books, thanks for posting!