[AllanS]

This just popped up on USAM yesterday.  It looks like a first generation model.
I imagine it’ll go pretty quickly.  Should someone interested is something like this jump at the chance? I’ve only ever seen one other offered and it was an OLED model for local pickup only for $100 less.  I do like the separate L/R gain.
https://www.usaudiomart.com/details/650216126-don-sachs-model-2-linestage-preamplifier/images/5671385/

[FullRangeMan]

Dont walk run from any tube equip that use PCB at any price, I would look a Chinese 6SN7 preamp with point to point hard wiring, not stranded. As always IMO.

[Tyson]

Don makes one of the best preamps in the world.  I'd jump on it.

[mresseguie]

I had one of these (wood case/silver-colored faceplate) for years until about two years ago. I loved the L and R gain control dials. I only sold it because I had bought Don’s newest model, and because my wife was beginning to complain that I had too much gear. I really loved that preamp.

[AllanS]

Many thanks guys.  I've got some soul searching to do.  I've pulled some errant triggers the past couple of years (much of it boxed up under the desk I'm sitting at waiting for new homes) and this feels like committing to a path that I'm all of a sudden unsure of.
I've been off the merry go round for a few years, but I don't remember the next stop on the motorcycle journey ever being so conflicting.
Anyway I very much appreciate your thoughts and comments.

[genjamon]

I've owned one from this generation since 2018.  What amp(s) would you be mating it with?  And speakers?

[AllanS]

I've owned one from this generation since 2018.  What amp(s) would you be mating it with?  And speakers?

Thanks for asking.  The amp for the foreseeable future is a Schiit Aegir I, which is part of the conflict.  I like the amp but suspect it would hold a DS2 back (or equally intriguing Cary Audio SLP 98, Supratek Chardonnay).
Speakers are Spatial M4 Sapphires.

[Tyson]

A tubed preamp with an SS amp like the Aegir can really elevate the sound in unexpected ways.  I wouldn't let the Aegir hold you back from the DS2.  Tubed preamps with SS amps almost always have real synergy. 

[genjamon]

Interesting. What’s your current preamp? I’ve mainly used my Don Sachs with an Odyssey Kismet SS amp, but also a few other SS and tubed amps.

Looks like the listed DS pre has Milfex copper foil caps on one set of outputs and some kind of Audyn on the other. I have Miflex on one of my outputs and VCAP ODAM with Duelund bypass caps on the board where those Audyns are on the listed pre. The Miflex are warmer, while the ODAM are crystal clear, but leaner. Good to have both options for matching for system synergy. The caps are really easy to swap out if you want to experiment.  Miflex with a SS amp is a good start though.

Swapping the rectifier between different brands is also a really good way to hunt for system synergy. They’re not very expensive compared with the signal tubes and can have just as large an impact on the tone and character of the sound.

It would take some fiddling to get the most out of the Aegir pairing, so this would possibly put you back into the rabbit hole. But you might not have to go very deep to find a sound you like.

[Rusty Jefferson]

Thanks for asking.  The amp for the foreseeable future is a Schiit Aegir I, which is part of the conflict.....

That amplifier has 22k ohms of input impedance (single ended) and 44k ohms (balanced). In that linked ad it says the preamp will drive an amplifier with a minimum of 30k ohms input impedance. You'll want to run it balanced. Many tube preamps have fairly high output impedance (2k-3k ohms) and shouldn't be paired with amplifiers with low input impedance (10k-22k ohms) as it just won't 'drive' the music well. Tends to sound kind of 'blah'.

[genjamon]

The Odyssey Kismet is a 20k input impedance, and the drive from my DS pre is just fine. Though the Kismet was designed to be driven by the Odyssey Candela, another tube pre. Not sure what else is going on with the Odyssey design, but impedance matching is not the full story there.

Bass roll off is a key problem with an impedance mismatch and coupling capacitors not properly sized. When Don Sachs says that pre is good down to a 30k input impedance amp, that’s based on the size of the Miflex coupling caps being 2.2uF, but also some assumptions about what’s ideal. I’m confident you won’t get bass roll off with 2.2uF caps until much lower than 30k ohms amp input impedance. What you might get below 30k ohms is some phase issues in the deep bass frequencies. But, depending on your speaker bass extension, these phase issues may be lower than the speaker frequency response.

[AllanS]

Tyson, thank you for the reassurance. I’m seemingly insensitive to what a lot of folks around here find obvious - another hesitation for getting too carried away. But I think I'm catching a bit of tube vibe with the Schiit Lyr+ that’s been driving the Aegir for 18 months while I putzed around trying to sort this out.  All I’m really looking for is more of that tube thing and better sound stage layering.

Rusty,  thank you for catching the impedance mismatch.  I checked the Aegir spec after apparently misreading/misunderstanding the 30K ohm comment and thought all was good.  Unfortunately balanced is only an option for the Aegir when running mono.

genjamon,  thanks much for the evaluation and discussion.  You’ve taught me more about impedance in 2 paragraphs than I’ve picked up in 2 years.  I need to pay more attention if it’s getting any regular discussion here.  All I’ve ever heard with respect to impedances is damping factor > 10.  For whatever it’s worth, the Odyssey Candela preamp output impedance is listed as < 2K ohms.
As mentioned I’ve been running a Lyr+ headphone amp.  It was repurposed from a decommissioned desktop setup.  It’s limited to SE only @ 75 ohm output impedance.  The Schiit Freya+ is also 75 ohm SE and 600 balanced.
The speakers are about -3db @ 40 HZ.
What I’m hearing is the impedance characteristics of the advertised DS and Aegir present something of a relatively minor risk but you’ve had good success.
Given all that I’ll proceed with some caution.  Thanks again! This has been very helpful.

[AllanS]

Since we were on the subject I wanted to ask about the gain level adjustment but forgot.
On his site Don said the gain level adjustment wasn’t necessary if the image is centered.
I’d read elsewhere that gain level adjustment separate from the main volume is helpful for matching the pre to power amp gain.  For high gain amps my understanding is limiting overall preamp gain provides greater volume control resolution.
Is this incorrect?

[JackD]

You might want to ask Don directly, but based on his description they sound like individual channel volume controls ahead of the master volume controls rather than a true gain control.  A true gain control like on the Supratek preamps lets you adjust the gain provided to the amps as a whole and then they provide a separate balance control to adjust center image. I have used two different Supratek preamps with amps ranging from .65 volts to 2.5 volts using the gain control to suppress tube noise.

[mresseguie]

Allan,

I found the adjustable gain especially useful in a past listening room where there was no wall on the right side and a full wall on the left. By turning one dial to the ~10:30 position, I was able to keep the 3D image centered between the speakers.

[genjamon]

I have always used the gain controls for overall gain adjustment of the preamp, not for left/right balance. If the gain controls weren’t there, the preamp would be unusable with my 26db and 32db gain amps into my 96 db sensitivity speakers. With speakers in the 80’s of sensitivity, I’m sure it would work great at full tilt, but on high efficiency speakers I would only have a very limited range of the volume control that was usable, and the steps between settings on the Khozmo volume control would be far too large to allow me to find the right volume level.  By dialing back the gain, I can find the right balance of full dynamics of the system while preserving useful volume control with a wide variety of amps and speakers.

[AllanS]

Thanks much all.  It may not make a practical difference but I did send a note to Don asking about what he refers to as channel level attenuators.  I'll let you know what he has to say if he's able to respond.

[AllanS]

Don responded quickly.  He basically said to use the level controls to manage gain.  So basically validating whatever y’all have been doing.
genjamon, he confirmed your evaluation of the impedance match and went one further saying the 2.2 uF caps would drive the 22K ohm without any problems.

[genjamon]

Yes, my understanding of these things has been shaped largely be conversations with Don himself. Glad to hear I haven’t misremembered anything.

[RDavidson]

You might ask Don where you can get it serviced if/when the time comes. It is my understanding that Don is, at least, semi-retired. I’m sure he has a legacy plan for this stuff, but it’s good to know when you’re looking to drop a substantial amount of cash on a rather bespoke / boutique piece of gear.