Relaixed2 -- DIY Balanced Pre-Amp Build Report

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In the end, I did not try the LME49990. Further research suggested the LME49710 might be better in my application, so I gave them a try and didn't like them very much. Fairly thin sound, as I recall. I wish I had stay the path and tried the LME49990.

I also tried OPA1611, OPA1641, and OPA627 in the same setup. All were pretty nice. The 1641 had a little faster sound and a little more detail than the 1611, but both were good. In the end, I prefer the old standby, OPA627. It manages the best soundstage, very nice detail, and smooth, full sound that is hard to beat.
 
Built this about a year ago and it's been working great. Really pleased with it. However just lately it's developed a problem: The display keeps dimming untill it can hardly be seen. Sound's perfectly ok. Haven't opened it up yet, just wondered if anyone has had similar problems or what I should check first.
 
Here's a few pics of my Relaixed2 preamp build. I used the LME49720 and all the other recommended opamp upgrades. I think it sounds very good. Very transparent and quiet. I use a SDtrans 384 sd card player to a TPA Buffalo3 via I2S, a Pass Aleph 30 and Polk SDA 2.3 speakers. I finally finished the box for the Relaixed preamp but have been using it unchanged for about a year. I really like it. Instructions are very written. Thanks for the great kit.
 

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I only wish that Jos had made the pads work with 0805 resistors. The MELF resistors are fine, but I have come to appreciate Susumu SMD resistors for their very good specs, good sound, and low cost. I find them at Mouser (limited selection), Newark (Farnell), and Digikey for less than the Vishay MELFs. Unfortunately, Susumu doesn't build big size SMD resistors and the pads for the MELF are just a little too far apart. Theoretically, there might be an advantage of SMD over MELF because their lower profile would have a smaller inductance loop, but I'm guessing that can't be heard in audio.

Regular or surface mount, I'm enjoying the Relaixed 2. One of these days I need to build a case for it.
 
Relaixed2 .v. Lighter Note Comparison

You know the drill. We work away at our DIY projects while hoping/knowing that what we are doing is going to be better than some other choice. Thanks to the generosity of bcmbob, I was able to audition a Lighter Note in comparison to the Relaixed2.

Note, these are very different designs. As you know, the Relaixed2 is an active pre with some gain and opamps in the signal path. It is also a relay operated, stepped attenuator.

In contrast, for those of you not familiar, the Lighter Note is an attenuator that uses light sensitive resistors to attenuate the signal. There is little in the signal path beyond the resistors and some impedance compensation. Attenuation is controlled by controlling the brightness of an LED which changes the resistance of the light sensitive resistor.

The Lighter Note has a good reputation for sound quality and has been built by a good number of DIY audio folks. The purpose of this evaluation is not to declare one design sounds better than the other. In the end, that is down to your individual tastes and system. The purpose is to find out if a Relaixed2 sounds comparable to a well respected DIY project.

I should declare that my Relaixed2 is a stock build with OPA627 opamps on Brown Dog adapters in the signal opamp positions. I chose to use the single ended output of my Marantz CD6004 CD player to feed either the Relaixed2 or the Lighter Note. As you know, the output of the Relaixed2 is balanced, so a balanced line receiver (DIY) is used at the amplifier to convert the balanced signal back into single ended when using the Relaixed2. The Lighter Note that I borrowed is singled ended input and output.

The results are what all of you who have built a Relaixed2 were hoping for. Both the Relaixed2 and the Lighter Note are fine quality attenuators. There are small differences in the subjective sound between the two, but each would be a fine DIY attenuation solution. I can say that I am happy with my choice and don't feel any need to keep trying something else.

I hope this was useful.
 
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