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Thursday, April 8, 2021

Making of a 10Y Line Preamplifier


Here some photos of a recently finished 10Y line preamp and it's assembly steps.

This preamp is equipped with ELROG ER801A tubes which are compatible with the 10Y family.

As always the power supply is external and uses a full wave bridge with 4 6AX4 tubes for the rectification of the high voltage.

Above all the metal plates for the preamp section. And for the power supply below.

Installing the oil capacitors and filament chokes:

The underside:

Trabsformers and B+ chokes are mounted on a separate plate:

This plate is mounted to the underside of the top plate and wired to the rest of the circuit:

This preamp uses Lundahl output transformers and Intactaudio AVCs. Optionally the preamp can also be built with Tribute OPTVCs.

The AVC is wired with teflon insulated solid core silver wire to the switch.

Finished preamp section:

The power supply:

Almost finished PSU:

Finished power supply:

The finished preamp, tested, and ready to ship:

Power supply and preamp are packed in separate wooden shipping crates. This unit ships to the US.

Drop me an email if you want me to build your very own 10Y preamplifier for you.

Best regards



  1. Do you still do these with the oval NOS paper-in-oil capacitors..?

    1. Yes I can use them on request. Still have some

  2. Thomas, is there any symptoms that indicate the tube is weak? I have old type 10 which behave outside the load line (I used Ale's Gyrator and Coleman Reg for Filament bias. Both tubes are set on same values (plate voltage & Filament Bias). However there's one tube draws current more than data sheet while the other draws less current.

    1. Especially with filament bias it is crucial to test the tubes. I always use a curve tracer. Old globe tubes can vary wildly in bias current and often have misaligned electrodes