[Daedalus Audio]

I'm very seriously considering adding a new product line... Daedalus Audio Passive Pre

The concept is a simple but VERY high quality ladder style volume for high end (and high gain) source components that don't really 'need' an active preamp. This would be a purist approach with the initial model being one input/ two outputs and of course housed in the signature dovetail case.

What I am seeing is many systems that are now based on a stand alone DAC and many of these have very good gain, but even those with a volume control simply don't have a good enough quality control to compete with a top end preamp.

any thoughts????

thanks,
lou

[Mike B.]

My two cents. I have owned discrete resistor passives, two transformer based passives, and a LDR based passive. The LDR passive is the only one that had the dynamics I associate with a good active. The other two types were not as engaging. Disclaimer- I have no financial interest in any type preamp.   

[david12]

 Hi Lou,
 I use a transformer based passive pre, a clone of the Music First audio baby reference, with an Audio Research ref 75 power amp and I have to say, I am more than happy with it. I compared it with an ARC Ref 3 pre and they were different rather than 1 better than the other. The Passive having a more detailed, refined, neutral sound, the ARC a bit more slam and dynamics. I don't think you can easily get away from the accusation that Passive Pre's lack some slam, but you make up in other areas, including price.

 I have read lot's of arguments for and against, transformer based and resistor ladder approaches. The latter is the cheaper option I believe. Top quality transformers from Stephens and Billington, are'nt cheap

[Early B.]

My two cents. I have owned discrete resistor passives, two transformer based passives, and a LDR based passive. The LDR passive is the only one that had the dynamics I associate with a good active. The other two types were not as engaging.

That's been my experience, as well. Even with the LDR passive I used to own, it doesn't compare to the dynamics of an active pre. I don't see any point trying another passive pre. You should consider partnering with a tube amp manufacturer to make amps designed for your speakers.

[aldcoll]

While I am very new to this higher quality audio world I did make my first correct venture into the equipment and purchased a pair of Lou's new Pan's.

When I first came across this posting I had to look up passive preamp.  So after some reading and a email from Lou I did a little rework with my limited equipment and can't believe the difference.

Speakers PAN
Integrated Amp NAD 7400  (pawn shop $200 twenty years ago) and a leader in it's class at the time and long on power but a class D.
Squeezebox 3  Craig's list $100
ZDAC  New full price //www.audiocircle.com/Smileys/audiocircle/icon_rolleyes.gif She said I could by something that day.
Daedalus Boulder Speaker Cables This web site from Australia @ $475 and I am still working out the Southern orientation of the Polarity.
The rest of the cables radio shack and B stock crap.
Did I mention I have Champagne taste and a Water Budget.

So just by adding the Speaker cables I was stocked and the sound came alive and I started to hear a real Sound stage.   Granted there is still some rotten planking on the stage.

So Today I pulled the jumpers off the back of the amp and ran toe Squeezebox to DAC to Amp only using the volume control of the Squeezer.  Just think what some real cables will do.

I will also note that it is dead quiet.  And while my ears may not be attuned as some I don't hear a thing unless you hit play.  The base stepped up was very pleasing.  The fact that I took out of the circuit a 25+ year old preamp has to help something. The whole listening  experience has presented it's self a new playing field for my self.  And still far to go.

Did I mention I have Champagne taste and a Water Budget.

And so as Lou was saying this would be a budget way or should I say affordable way to listen with out a Preamp I can also see the light that with a better DAC and Amp one will also be listening to what was recorded and not what was processed to the color of your chosen equipment.   ( I am sure you will let me know if I get this wrong)

Now I am off to collect more can's and bottles since all those nickles add up. 

[barrows]

" I have read lot's of arguments for and against, transformer based and resistor ladder approaches. The latter is the cheaper option I believe. Top quality transformers from Stephens and Billington, are'nt cheap"

Not so fast there...  The best quality resistor ladder VC control would require the best quality resistors, and that means TX-2575s from Texas Components (@ around $10 each for .1%) and the best quality switches, Shallcos with silver on gold contacts.  And then, of course for balanced signals one would need twice as many resistors and switches...  While I agree that good transfomer based VCs are expensive, so are the best resistor ladders.
I do not think it is really worth the effort to just make a passive.  A buffered passive would be my choice.  This way one does not add any uneeded voltage gain, but still has the dynamics of an active device.  A discrete MOSFET output buffer with shunt regulated power supply would be my suggestion.  Get the output Z down in the 15-20 ohm range with a nice large current headroom for top level dynamic performance into any load.

[aldcoll]

Thanks for the reply.   While most of what you wrote is above my pay grade as they say.  But as read it through a few times I get it and will look into.
What I personally have to weigh the whole thing on is Cost for sound.
I also want to minimize the equipment and it color it brings to the party.

I always thought Blue lights were on top of the car behind me.

[Daedalus Audio]

I think I would agree with Barrows, I have not fully explored the transformer option but have found that I had to add a buffer unit to get top notch sound.  Oh well .....

[jtwrace]

I don't understand why you would want to even get into this type of thing.  You're partnered with Modwright...let him build whatever you want in an optional wood case if that's the way you want it built.  It sounds as though you stay plenty busy building speakers. 

[paul79]

The resolution of a quality tube preamp is tough to beat. This would be my pick. TVC can be great, but if the DAC does not have enough drive capability, this won't work. Bass and dynamics will suffer big time. I have never liked passive preamps either. They can sound very amazing at one point of the volume control, then a minor adjustment and they become lifeless. Just my experience.

[Daedalus Audio]

The reason I wanted to do this was because the direct output from Dan's new DAC (Elyse) is so good and I hoped this would work so people could get world class sound without breaking the bank.
I will say that the passive I did put together here when coupled with a tube buffer gets you in the ball field with $5k -$10k preamps,  doesn't do it all but is still in that range....

[bonsai]

I built a preamp that was a Khozmo attenuator into a DCB1 buffer. 

The DCB1 is a Pass B1 buffer with some solid regulated power supply.  I did the DCB1 Hot Rod build.  I built with 99.9 silver wire in teflon tube.  The preamp being just an attenuator into this buffer was exceptional.  I like the sound of this combo when you have a source with a solid output stage with a good gain from a quaility source.

Right not I run a LED attenuator passive into a Purity Audio Harmony buffer. 

I've done real preamps and prefer this route... 

This DCB1 thread is located at:
http://www.diyaudio.com/forums/analog-line-level/171715-salas-hotrodded-blue-dcb1-build-new-post.html

[paul79]

What are the output specs of the Elyse DAC? If it is a fully discrete output stage (no opamps) and has plenty of drive current on tap, then a TVC would do the trick. However, it must be a very high quality TVC to pull it off transparently.

I can vouch for this kit:
http://www.ebay.com/itm/Teramoto-FINEMET-Premium-Transformer-Volume-Control-TVC-with-Seiden-Switch-/200870484580?pt=Vintage_Electronics_R2&hash=item2ec4d05a64

This is a TVC like NO other, no joke. The only one I have heard that does no wrong, as long as the DAC has sufficient drive.

Not exactly cheap, but in the right setup, you'd have a damn hard time finding an active pre that will touch it. IMO, this kit is an absolute bargain.

Edit: I just read that the output is transformer coupled.... A TVC won't be the best solution here then. 2 transformers in the signal path will more than likely, be a bad thing.