I remember my first time witness to a DIY shoot out session very well. It was a cordial event held at a senior DIY-er's home whose system was deemed most suitable to host, i.e. system sonics has to of rather high standards and allow easy access to plug and unplug components for the shoot out.

The star of the shoot out was 3 versions of the much loved Marantz 7 pre amp. All three pre amps are built based on the very same schematic that is legendary in sound quality, but each version had different parts on it and various degrees of circuitry tweaks to reflect the builder's musical taste and personalised work signature.

I remember vividly that each version of the Marantz 7 sounding very different from one another. However, with great show of respect for each other and the subjective truth, all three of the builders gentlemanly settle the score and concluded, based on what they heard and elected the best sounding pre amp of the day. Four of us sat down for a cuppa after the shoot out where everyone shared their build experience. It was a great day for a DIY student like me, to be in the company of experienced old timers.
MKIII Boards

Today, I am just as excited as I am posting out a batch of PCBs(Printed Circuit Board)to a group of DIY-ers, where I am about to meet again in 3 months time, to hopefully witness another great and cordial DIY shoot out session.
MKIII Test Board

This time round, the star of the shoot out would be Carlos's implementation of the AD815 chip pre amp. For more info go to http://www.diyaudio.com/, do a search for Carlos or AD815. The AD815 chip is a telecommunications chips designed by Analog Device to handle high band width A/V applications. However, in the late 1990s, the high end marquee, Jeff Rowland was pairing this chip with the Crystal CS3310 volume chip for use on their flagship Coherence pre amp( see review on http://www.stereophile.com/) which was battery powered. Carlos's implementation of the AD815 is rather simplified to make this project very cost effective to build but yet have very musical sound.
The AD815 Chip

The local designer whom helped to make to project possible had retained Carlos's audio signal section of the schematic (on the left hand side of the MKIII board), but choose to use a class A power supply section instead(about 60% from the right side of the MKIII board). I had an AD815 built earlier based on the MKI version boards, which to me sounds musically satisfying when partnered to my LM3886 chip power amp(that will be another story in another time), driving a pair of Epos ES11 then. The bass was tightly controlled and extended very low, the mids had tube like quality and the highs airy. My only gripe was the highs could at times sound a tad grainy. Not bad for a budget build.
My version built on MKI board

The pictures that you see now are the MKIII boards. The improvements of the MKIII boards over the previous versions are, shorter signal paths, improved grounding and a more stable power supply re-design. According to the local project designer, whom wishes to remain anonymous, the MKIII boards in theory should sound better than previous versions, again depending on the builder's tweaks and skills.

So, it's ready, get set, build!

And wishing all those building the project "Have an enjoyable musical time!"


Anonymous said...

Panzer, don't forget about the 2 boards I'll need if you have any leftovers. :) You know who I am. Hee Hee. Very exciting and anxious to get my hands on them.

Panzer said...

anonymous 12.59am,

Sure I have 2 boards here waiting for you to stake your claim on it!

Happy building.

abes99 said...

hi panzer,
could you help me find a pcb for thead815 carlos project preamp