CAL Sigma II DAC - tube rolling experience - 12ax7

Posted by Gofast (A) on April 19, 2007 at 07:12:19

Not much in the archives about tubes for this DAC, so thought I'd post this. This is the older version, non 24/96.

I was going to sell the CAL Sigma II DAC, so before I closed the box, I decided to go through all my tubes to find the best sounding inexpensive tube to include with the unit for the next owner. I had rolled this unit in the past, and ended up using the Telefunken 12ax7, but I was not about to sell it with the TFK - I need that for my phono stages.

I'll break these into 3 groups.

Group 1: Great sounding - huge bass, extended and delicate treble, huge soundstage. You cant believe you are listening to a $300 DAC. I'd be indifferent between any of these. I may need to do a second round to decide between these.

- old Telefunken 12ax7 (w/ diamond)- push/shove I'd choose this one.
- Telefunken 12ax7, made in germany, no diamond, taller than 1st one, has a backwards L in circle between pins. Siemens? As good as other tfk. Maybe a touch more forward
- Mullard 12ax7a/ecc83 (outline like alien face, no eyes) - very close to the TFK. slightly warmer.
- RCA 12ax7 58-17 black plate. A touch cooler than the TFK and Mullard. super bass.
- Siemens 12ax7 - very good too, a touch more nasal than the 2 tfk tubes.

Group 2: natural sounding with decent bass and treble that is not harsh. Either liveable, or really good at something.
- Shuguang 12ax7c - borderline Group 1. Great bass, teeny bit harsher in treble than the old tubes in group1. May not be burned in enough tho.
- Sylvania 5751, gold pins. Great bass. touch nasal
- Amperex 12ax7a/ecc83 75-41 orange print- great bass. Less forward than group 1. More fuzzy images. Good LT listening potential.
- Mullard Ecc83 I63 B9a delta, x between pins - Nice tone, low bass
- Philips Miniwatt ecc83- medium bass, nice tone, nice treble. kindof a baseline tube that is liveable
- EH 12ax7eh - nice sounding, good treble, limited low end. Very similar to the miniwatt.

Group 3: Tubes with no bass. No point listening for other characteristics.
- Marconi ECC83 B339 British Made I61 B91. 0 between pins. I did not test this to see how strong it is. Very thin sounding. No bass
- Teslovak E83CCS 9825(I think this was the tube that came with the CAL). Slightly better bass than the Marconi, but not by much.

I was going to sell the CAL Sigma, but have now decided to keep in. In fact I may chase down an Alpha.

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Topic - CAL Sigma II DAC - tube rolling experience - 12ax7 - Gofast 07:12:19 04/19/07 (3)

Re: CAL Sigma II DAC - tube rolling experience - 12ax7 - MJL 11:00:38 04/21/07 (1)

Re: CAL Sigma II DAC - tube rolling experience - 12ax7 - Gofast 12:29:26 04/21/07 (0)

2 more I forgot - Gofast 07:21:13 04/19/07 (0)

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