Which Audiologic dac was the first to go 24 bit?

Rx8man - Hello - your comment about "special tubes" caught my attention, as I have been wanting to try another set in my M34 dsm, purchased here used a couple years ago. We will be moving shortly; so, while the system is taken down, I thought it would be the opportune time to install new tubes, since I have no idea about the previous history of the stock unit. Also, my owner's manual apparently is missing the "tube placement diagram" page. I've never purchased a tube in my life, but figured I would contact Andy at Vintage Tube after reading about him here on the forum, and then at his website. Would you be willing to share your "special" ingredients.
Thanks very much for any suggestions you might care to provide.
Best regards,
Tom

Pat (Rx8man).....do you want to talk about tubes
in the M34, or do you want me to jump in at this
point?

Hey Jeffcott go for it, thanks for the offer !!

I thought that Jerry told me that the 24 chip was better when I was buying my used AL unit 34 that had the chip upgrade. I guess I was wrong. Hmmmm. I think I have some Amperex 6922 gold pins in the unit as well as some Amperex 7308s??? They sound much better then the stock tubes. Rcprince has much more experience then I do and I am not sure if the tubes I am quoting are the ones the unit has, if I get corrected then I'll have to check into it further.

Happy Listening.

Pat and I have spoken a number of times regarding tubes in the M34, but I didn't want to steal his thunder. I have an M34DSB which, like Pat, I love and enjoy.

As regards your question about tube placement in the 34, looking from the front, the 12AU7 pair is on the left side (in line) and the 6DJ8 is on the right side (also in line).

As regards tube rolling, I had the occasion to speak with Jerry Ozment a few months back and he (to my hearing) confirmed my perception that the DAC is significantly more sensitive to 12AU7 selection than to 6DJ8 selection. I would suggest that you start there. I am a long way from trying everything but I have tried a few inclusive of Sylvania yellow labels, RCA's Black Plate 12AU7s, 5814a's and 5963's, and Siemens Silver Plates. Pat has used Amperex Bugle Boys so he will need to chime in on his comparison there (sorry Pat, I still have not gotten that done.

Observations: in my experience, the LARGEST improvement with this DAC and tubes has been isolation. When I put a Townshend Seismic Sink under the DAC, all of the rules changed. I would encourage anyone with this DAC to start there. It really levels the playing field. Yes, better tubes are still better, but the spread is definitely reduced.

As regards tube dampers, I think they are mandatory and the Herbies Halo-9's are a nice damper. I use 'em.

Tube observations: IMO, one of the best "affordable" tubes is the 1950's production Black Plate RCA 12AU7. Without isolation, they can be a bit bright and shrill, but put a sink under them and they get magic. They do cymbals wonderfully. A tube with a softer top end sound is the Black Plate 5814A. This was my preferred tube for quite some period of time. If you feel that CD playback has just a bit of an edge, try this tube.

My tube of choice at the present (as I have been fortunate enough to find a pair) is the Siemens Silver Plate ECC82. These tubes are scarce, but I just love them. Some have described them as the pinnacle of the 12AU7 family. All I can say is that they do everything just right for my tastes.

In terms of the 6DJ8 slot, I have used both Bugle Boys and Amperex PQ's. The PQ's were an improvment, but it was a SMALL improvement. On my list of to try tubes in this position are Brimar, Siemens and Tungsram.

If anyone is interested, email me off-line and I will send you a copy of my notes on tubes that you are interested in, and a slough of links to entertain yourself with.

Tburn, if you wish to try any of the above RCA's or Sylvania's, let me know. I have extras and would sell you enough inexpensively to get a good taste. These are inexpensive tubes.