I had tried a passive pre before and it seemed to suck the life out of the music.
I then went to a simple two tube pre I found in an old Glass Audio article and have been very happy.
I'd like to try the passive pre again. Is there a trick to keeping the life in the music?
Just some thoughts here about tone issues that could arise from using a passive unbuffered level controller like this with gear that might not have really great buffering built in:
Is there a trick to keeping the life in the music? Yes. the trick is impedance matching (for tone and noise levels) and presenting some type of buffer so the source and destination devices can't adversely affect each other's performance (also for tone and noise levels).
If that isn't taken into account (using transformers or maybe something else in a fully passive design) then you have to hope that your source gear and power amp are well buffered at their relevant connectors.
This is why this thread's volume attenutator project (I wouldn't call it a preamp, it's not amplifying anything
, while ridiculously easy and certainly a purist approach, may actually be lacking a couple of buffering circuits.
Without buffering the unit might perform just great with some gear and be very lifeless with (hopefully rarely) other gear.
The result of bad impedance matching and/or gear interacting incorrectly with each other tends to be lifeless unmusical sound as perceived by our ears, and in some cases dramatically increased hiss and even loss of signal quality (increased distortion) and level - it all depends on the other gear in your chain and how well it works with each other with only a pot/resistor between the two pieces.
There are certainly some very effective devices out there that are, while more complex than yours, similarly designed without true input and output buffers, and I have a feeling that in many cases this thread's volume attenuator would sound just great!
For further research to those involved, there are some inexpensive semi-pro-audio devices for use in recording that do the same thing, although in most cases with a slightly different purpose in mind, that you can buy for something crazy like $70 or $80 bucks. One of the better while still inexpensive fully passive level attenuators/monitor switchers is by SMPro and I recommend it to this thread's readers as a research project to see if there are useful things it contains that you might want to add to your own.
I haven't looked inside one for a long time though and fully admit that it might just be a simple pot and resistor and switching system without buffers, just like yours. However definitely would be worth checking out since electrically speaking it does exactly the same thing in the same places in the circuit that your box does, just with different switching options (and in fact could be purchased and used exactly how you're using your DIY level controller/switcher, although obviously it wouldn't be DIY any longer so not nearly as fun LoL)
I have used the SMPro box though for passive control of multiple amplifiers/speakers from my mixing board in my recording studio with very good results.
Hopefully that's a little bit of info that might be helpful to those curious about this stuff.
By the way, great work on the project, I love the look and way it works, I love the purist attitude and inexpensive plus simple build.
Very cool!
I'm just trying to add a bit of info for those curious. Maybe looking at the SMPro box or similar will result in some further ideas?
