Hi devilboy,
No Lundahl modification. I just had a local tech replace the stock
output coupling caps (which are very good) with the Duelund CAST copper foil capacitors. This was done quite some time ago (6 years or so) and the CAST pair cost about 450.00 at that time. . Worth every penny IMHO.
Absolutely agree with your listening impressions. Beautifully natural, instruments and voices just sound right. Yamamoto has not modified or changed anything with this DAC since its introduction more than 10 years ago. When the sound is pure and natural there's no need to tamper with the product.
I've had mind for probably 8 or 9 years (maybe even longer). I was very happy with the stock DAC and only changed the caps due to my success /happiness with the CAST caps placed in my speaker's crossover done about a year prior. I've heard quite a few very well regarded DACs through the years but not one of them has given me the urge to replace the simple Yamamoto YDA-01. It has stood the test of time. It just flies under the radar.
Charles