Experiences of others who build the Euridice Preamp

Gary Bronner wrote to me....

I wrote to you a while back about my version of the Euridice preamp, which followed your version pretty closely. I took a few snap shots with my digital camera.

Here are shots of the preamp:

And here is a shot of the power supply

The preamp uses Bartolucci output transformers, WE417a tubes with 220 ohm cathode resistors bypassed with 2200uf Cerafine caps. The input attentuator is a 100K stepped attenuator. I found that putting a 220K resistor across the transformer primary improved the sound a bit.

The filaments are heated with current sources. Supply voltage is about 180v. Any higher B+ and I found that the preamp started to sound a bit harsh. The preamp is rather sensitive to residual ripple on the B+, so I used a C/L/C/L/C power supply.

First C is 10uf, then 5H, then 330uF, then 5H, then 100uF. The 10uf is an oil cap, the 330uf is an electrolytic, and the 100uf caps are polypro. Simulations show that the ripple is less than 1E-5v. I found that 1E-3 ripple was quite audible.

I played around with various HV rectifiers, comparing GZ37, 5U4, 5AR4, and 5Z4 and UF1007 diodes and I ended up preferring the UF1007 diodes. I use a snubber network before the diodes. The sound of the preamp is extremely good with extension at both ends and a clean effortless sound that is very appealing.