Who needs a Preamp??

Ralph (Atma-Sphere) i got great sound with a Townshend Allegri+ with a pair of your mono's, one of the best sounds i have heard.

The Townsend is a Transformer Volume Control rather than a simple passive (potentiometer)- a bit different in principle than what has been discussed here so far.

If the output of the source is direct coupled then passive controls have a better chance of working. This is one of the reasons you see so much variation in user experiences.

My amps sit by my speakers allowing for short speaker cables. I find with shorter speaker cables the system has greater resolution.

But I also find that having the front end of the system in an adjacent room also helps as there is less vibration (despite a custom stand and platforms)- which makes a difference to things like CD transports (less errors) and turntables (less coloration).


So my interconnect cables are 30 feet long. Obviously a passive can't do the job. I have tried them (in fact we used to make one 30 years ago) because it would be nice if things were simpler; more compact (although I'd have to have the system sitting between the speakers, which I don't like). But I find that there are colorations that don't exist when using the preamp. Particularly disturbing for me is the reduction in bass impact and dynamic contrast, a bit like a tone control. I don't get this effect with my preamp. I've played bass since the 7th grade so this bit has to be right for me or I'm unconvinced. People that don't like bass may find a passive to their liking.

I suppose if I had to floor the accelerator to drive 55 mph, maybe I’d think the life was being sucked out of my driving. Then again, maybe I like 55. Nice and safe, good gas mileage…

Is impedance matching an issue? Passive volume controls do have to make a trade-off between input impedance and output impedance. If the input impedance is high, making the input to the volume control easy for the source to drive, then the output impedance is also high, possibly creating difficulty with the input impedance of the power amplifier. And vice versa: If your amplifier prefers low source impedance, then your signal source might have to look at low impedance in the volume control.

Immediately following the text George quoted above from Nelson Pass is the text above.

The reason an active line section can sound better than a passive has a lot to do with interconnect cables. Passive controls have poor output impedance- usually quite high, which allows the interconnect cable to do its worst mathematically speaking- and this is audible as others on this thread have already pointed out.


If the line section has a low output impedance it can swamp the characteristics of the cable- in other words its output impedance dominates that math I mentioned. So less effect. If you've ever had to audition interconnect cables to pick the one that sounded right then you know exactly what I'm talking about.


Now this problem was identified and dealt with by the recording industry decades ago and resulted in what we know as the balanced line standard (AES48). If you equipment conforms to this standard you'll find very little difference between cables. Most high end audio products do not, but if you have one that does, interceding it between your sources and amps can easily increase transparency if you keep the connections to your sources short. 

Now of course such a line section could be built into a DAC- but then you have the issue of if you ever want to improve the DAC or the line section, you have to replace both (and its often not a good idea to have a DAC and line section run off of the same power supply). DACs are notorious for going out of date; this is a very real issue.