A Review of “The Restoration Preamp”TM
by Don Walizer, Conway, Arkansas
April 18, 2008
Hats off to TDL Technology for developing the 4010 audio restoration preamp. For the past fifteen years I have been searching in vain for a modern replacement for the venerable OWL Audio Restoration Module that would incorporate the OWL's functionality with updated electronics and more refined filter design. During that time I looked at the half dozen or so available alternatives that have come and gone, most of which were grossly overpriced, and none of which offered the intelligent design choices of the OWL for people genuinely interested in doing audio restoration. I was really excited when I heard about the 4010 because it seemed to incorporate everything that I had been hoping for in an audio restoration preamp. Having owned another TDL Technology preamp, I was pretty sure that the 4010 would have good sonic qualities; but would it really live up to my expectations?
I have been using my 4010 for two months now and can say that it is everything that I ever wanted in an audio restoration preamp. The 4010 makes it easy to restore even the most challenging recordings. I can quickly check the left and right groove walls for excessive distortion and blend them for best overall result. The L-R (vertical) setting lets me check for low frequency noise and set the rumble filter correctly. (Turntable rumble isn't an issue with my KAB Broadcast Standard turntable, but it is amazing how much low frequency noise is present on some recordings as a result of the cutting, mastering, and pressing operations.)
The most important equalization setting is finding the correct turnover. This is what really brings a recording to life, and the 4010 excels in it's ability to bring the sonic field into correct focus. For example, I recently made a CD of jazz recordings from the mid-30s to the mid 40's. Two of the tracks from a 1937 Coleman Hawkins recording just didn't sound right in comparison with the other tracks I'd restored. They were sort of dull and lifeless. I'd used a 300hz turnover without experimenting because it was the "correct" setting for that label and year. After wondering why these tracks just sounded ok while the other tracks sounded great, I checked the record label - it had been recorded in England! Well, that probably meant that I should have set my turnover to a lower setting. When I played the record back using a 250hz turnover it jumped to life. Everything sounded right, and did it swing!
Who would ever think that going from a turnover of 300hz to 250hz would make such a dramatic difference? Since I never owned a restoration preamp like the 4010 I was not able to make a comparison like this before. In fact, as far as I know, and I've done a lot of research on this, you can't buy another preamp that will give you this capability. I don't want to downplay the importance of accurate rolloff equalization and the usefulness of a properly designed lowpass filter. The 4010 excels in these areas as well and, again, offers more settings than any other product you can buy.
Other things I like about the 4010 are characteristics that it shares with other products from TDL Technology. First, like me, they are fanatics about noise. Consequently, the 4010 is dead quiet. If there is hum, buzzing, RFI, or EMI in your system, look elsewhere for its cause. Second, build quality is second to none. High quality components are used throughout and the 4010 has a solid feel about it. Each unit is hand assembled and undergoes a 100 hour burn in test. The user manual contains complete block and circuit diagrams, useful information about how to use the product, and a full parts list. If you have a question, you get a prompt, courteous reply. Who says that good customer service doesn't exist anymore in the audio industry?
I sold my OWL two weeks ago. The 4010 does everything the OWL did, only better. The king is dead, long live the king.