Hi Guys,
After building a small HV power supply regulated power supply to eventually build a tube preamp chassis to couple to my Aleph J. I found out it might be a better idea to ask some questions before I move to a pre-amplifier circuit choice.
Currently, I drive my homebuilt Aleph J from an IPhone 5. I know its dated but it sounds good to me and seems to measure well into low impedance loads:
https://www.kenrockwell.com/apple/iphone-5/audio-quality.htm
Using high quality 320k mp3 I found that I need to keep the volume at 80-100% or a room filling sound with the Aleph J and generally its not really loud enough and a real Eureka moment came when a friend brought is Sony headphone amplifier over and plugged it in and WOW it really came alive.
I started looking into the specs of the Aleph J:
Input Impedance 242 Kohms (RCA input)
Input for 25 watts output 1.5 volts
Is that 1.5 volts RMS or peak-to-peak?
I already put some time to build up a chassis with R-CORE transformer with a HV and LV regulator board for this circuit thinking it would be appropriate but then I re-read Aleph J specs and its input impedance is over double of that stated by this design (100K vs 242K). What should I do now lol?
This was recommended in the RCA Radiotron design guide in the 60's as a 12AU7 preamp design. I wanted to use 12AU7 specifically for this because I was gifted about 30 NOS 6189W tubes from a retired military technician, all in original boxes. Is it still a viable design to use with the Aleph J or other amp designs? If not, what preamp design is best coupled with Aleph J? I already built the HV/LV power supply and really want to use the tubes I was gifted. Any suggestions or ideas is really appreciated!
After building a small HV power supply regulated power supply to eventually build a tube preamp chassis to couple to my Aleph J. I found out it might be a better idea to ask some questions before I move to a pre-amplifier circuit choice.
Currently, I drive my homebuilt Aleph J from an IPhone 5. I know its dated but it sounds good to me and seems to measure well into low impedance loads:
https://www.kenrockwell.com/apple/iphone-5/audio-quality.htm
Using high quality 320k mp3 I found that I need to keep the volume at 80-100% or a room filling sound with the Aleph J and generally its not really loud enough and a real Eureka moment came when a friend brought is Sony headphone amplifier over and plugged it in and WOW it really came alive.
I started looking into the specs of the Aleph J:
Input Impedance 242 Kohms (RCA input)
Input for 25 watts output 1.5 volts
Is that 1.5 volts RMS or peak-to-peak?
I already put some time to build up a chassis with R-CORE transformer with a HV and LV regulator board for this circuit thinking it would be appropriate but then I re-read Aleph J specs and its input impedance is over double of that stated by this design (100K vs 242K). What should I do now lol?
This was recommended in the RCA Radiotron design guide in the 60's as a 12AU7 preamp design. I wanted to use 12AU7 specifically for this because I was gifted about 30 NOS 6189W tubes from a retired military technician, all in original boxes. Is it still a viable design to use with the Aleph J or other amp designs? If not, what preamp design is best coupled with Aleph J? I already built the HV/LV power supply and really want to use the tubes I was gifted. Any suggestions or ideas is really appreciated!
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This might work for you...
https://diyaudioprojects.com/Tubes/ECC802S-ECC82-12AU7-Tube-SRPP-Preamp/
I want to try this one, posted recently....
https://www.diyaudio.com/community/...c85-6922-6dj8-etc-mu-follower-or-srpp.388295/
https://diyaudioprojects.com/Tubes/ECC802S-ECC82-12AU7-Tube-SRPP-Preamp/
I want to try this one, posted recently....
https://www.diyaudio.com/community/...c85-6922-6dj8-etc-mu-follower-or-srpp.388295/
Will you continue to use the iPhone as a source in front of a new pre, or would you invest in a DAC too? Knowing what your source’s voltage could help inform your decision.
If you want to stick with tubes, John Broskie has several great sounding designs/boards(SRPP w/ 12AU7 is my fav). If your source outputs the typical 2v RMS, you could really get by with a buffer, be it tube or solid state.
My vote is the Iron Pre that ZM linked above. Has options to set gain, and you could even run it as a buffer if you don’t need the gain.
If you want to stick with tubes, John Broskie has several great sounding designs/boards(SRPP w/ 12AU7 is my fav). If your source outputs the typical 2v RMS, you could really get by with a buffer, be it tube or solid state.
My vote is the Iron Pre that ZM linked above. Has options to set gain, and you could even run it as a buffer if you don’t need the gain.
I found that I needed a preamp with a decent amount of gain to drive my aleph j properly. Any of the afor mentioned recommendations would work very well.
So I knew I’d end up building an Aleph J at some point… 😀
Q. Preamp, buffer or DAC direct?
Source (DAC)
SE 1.4vrms out, 200ohms output impedance
Bal 2.8vrms out, 100ohms output impedance
Speakers at 8ohm, 93dB sensitivity.
I kinda like DAC direct, no preamp, but only if the gain structure lets me achieve 70-90dB over the top >70% of digital volume control. I never really exceed 90dB.
I would have thought DAC direct would work as the input impedance is almost 250kOhm on Aleph J, but other people suggest not?
Would welcome advice.
Q. Preamp, buffer or DAC direct?
Source (DAC)
SE 1.4vrms out, 200ohms output impedance
Bal 2.8vrms out, 100ohms output impedance
Speakers at 8ohm, 93dB sensitivity.
I kinda like DAC direct, no preamp, but only if the gain structure lets me achieve 70-90dB over the top >70% of digital volume control. I never really exceed 90dB.
I would have thought DAC direct would work as the input impedance is almost 250kOhm on Aleph J, but other people suggest not?
Would welcome advice.
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if source is having proper cojones and there is no puny volpot inserted, nothing wrong driving J directly
