Its taken me a while but I finally finished my BHL build..
I ordered the 2 x std MM boards before I found out he had a deluxe dual-mono phono project in the wings and I thought do a "OTT" build. I really wanted to use this as a test-bed as follows
As I had 2 boards with 2 channels I thought I use the opportunity to make 2 separate dual-mono builds one pair using RUS PIO caps in the RIAA network and the other pair using high quality RUS MIL SPEC polystryenes. Both pairs will use polystyrenes in the O/P coupling hence any difference heard would be due only to the RIAA networks.
All components were hand matched between channels and polystyrene trim caps added where needed. Resistors are all DALE (except for the cart loading as I ran out of stock..)
I wanted to also to listen for differences between battery and low-noise active power supplies. This would require the use of a dual DPDT relay board.
In the NC (resting) state the external active PS is connected to the boards keeping them warm 24/7 as I believe thermal stability does have an important part to play in high performance electronics.
The front panel switch/LED is powered from the ext PS and is used to activate the twin 24V battery packs for true dual-mono operation.
The power rails from the relay board are then feed in to 15 Ohm and 20 x 220uF (4,500uF measured) ELNA RC stack per channel, the resistors primary function is to limit current spikes when stitching between ext and battery power as most of the time they will not be at the same voltage.
All PS caps are bypassed directly at the pins with 0.1uF WIMAs to decoupled or reduce parasitics as much as reasonably possible.
I also wanted to test differing cartridge R-C loading so made up a pair of 16pin DIL IC skts and glued them to rear panel immediately next to the RCA TT skts.
I have to say this build sounds very very good, its crystal clear quiet and the sound-staging is open and wide, very listenable... Im waiting for a month or two for burn-in to settle-down and I will do more detailed listening, and when Ive got a weekend free Im also going to do technical testing with my TEK 501A distn analyser and test jig etc etc..
I ordered the 2 x std MM boards before I found out he had a deluxe dual-mono phono project in the wings and I thought do a "OTT" build. I really wanted to use this as a test-bed as follows
As I had 2 boards with 2 channels I thought I use the opportunity to make 2 separate dual-mono builds one pair using RUS PIO caps in the RIAA network and the other pair using high quality RUS MIL SPEC polystryenes. Both pairs will use polystyrenes in the O/P coupling hence any difference heard would be due only to the RIAA networks.
All components were hand matched between channels and polystyrene trim caps added where needed. Resistors are all DALE (except for the cart loading as I ran out of stock..)
I wanted to also to listen for differences between battery and low-noise active power supplies. This would require the use of a dual DPDT relay board.
In the NC (resting) state the external active PS is connected to the boards keeping them warm 24/7 as I believe thermal stability does have an important part to play in high performance electronics.
The front panel switch/LED is powered from the ext PS and is used to activate the twin 24V battery packs for true dual-mono operation.
The power rails from the relay board are then feed in to 15 Ohm and 20 x 220uF (4,500uF measured) ELNA RC stack per channel, the resistors primary function is to limit current spikes when stitching between ext and battery power as most of the time they will not be at the same voltage.
All PS caps are bypassed directly at the pins with 0.1uF WIMAs to decoupled or reduce parasitics as much as reasonably possible.
I also wanted to test differing cartridge R-C loading so made up a pair of 16pin DIL IC skts and glued them to rear panel immediately next to the RCA TT skts.
I have to say this build sounds very very good, its crystal clear quiet and the sound-staging is open and wide, very listenable... Im waiting for a month or two for burn-in to settle-down and I will do more detailed listening, and when Ive got a weekend free Im also going to do technical testing with my TEK 501A distn analyser and test jig etc etc..