Aleph J - Recommended Preamplifier? (2025)

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!