difference between an active and a passive preamp?

King Rex preamp under $400. As transparent as a passive with tube like mids and deep bass of the solid state pre it is. I believe it has 15 db of gain. A real fine sounding unit the sounds well above its price.

There are a lot of caveats when using a passive preamp. As Elizabeth said, you have to make sure your source component has a very robust analogue output section with low output impedance. In addition, your interconnect lengths from source to preamp to amp (short as possible) and capacitance of the interconnects (lower the better) and the input impedance of the amplifier (higher the better) are critical as well. There are passive preamps made of pots, stepped resistors, LDRs, transformers, and autoformers. I prefer the latter three. If all of these are taken into consideration and executed correctly, a passive preamp is better sounding than any active preamp I have ever heard. But I have not heard the mega expensive $15k+ preamps like darTZeel, Atma-Sphere MP-1 with upgrades, etc.

Very nice clear responses...the way they build upon one another...nice to see someone get a direct answer(s) to their questions. Educational too....One for the archives!

The input impedance of your amp is 20k ohms. IMO this is not a great match for a passive preamp. There could be exceptions, but I am not aware of any.

On the other hand you could use a buffered preamp. This uses active circuitry with no gain. The active circuitry greatly minimizes the risk of impedance mismatches. There are tube buffers and solid state buffers. A few solid state options that come to mind are the Pass B-1, Burson Audio, and Horn Shoppe Truth. The latter of which I own and can state that it is extremely fast, detailed, and transparent. It gets out of the way which is what I believe a preamp should do. However, I would not classify it, as well as other solid state buffers, as having a tube like sound.

Also note, not all buffers have a volume control. If you desire something "tubey" you should probably stick to an active tube preamp or a tube buffer with volume control.

Should I be depressed that I am tempted to recycle posts I wrote 7 years ago, and that I remember them? 'Cause I am....

In any event, from the way-back machine in '04:

Just to add a couple more simplistic thoughts to the already excellent discussion from an absolute layman’s perspective, "volume control" generally can be achieved by two basic means, either attenuating (that is reducing) the signal that comes into the control or by amplifying it (which I have understood as adding gain). An active preamp is called that because the volume control can do both of these things--it can both reduce the signal from the input level towards zero and it can (because it has an amplification stage) amplify the signal above the input level. A "passive" preamp, on the other hand, is passive because it can only reduce the input level -- it will not have an amplification stage at all.

For most sources, the output level of the signal (which is the input at the preamp) is relatively high. Which is to say that at zero gain at the preamp (no attenuation or amplification of the signal) the volume level will be relatively loud. (Which is how passive preamps/volume controls can work -- based on the assumption that the volume associated with zero gain will be louder than you ever want or need, therefore attenuation or reduction of the signal level can provide all of the volume control range you would ever want).

Compared to just about every other source out there, however, the output signal that comes off of a vibrating pin scratching across a rotating platter of vinyl is tiny. So tiny that, without additional amplification, the signal would be too weak for a volume control designed to provide a useful range for things such as CD players to do much anything useful with at all. Thus, in order to jack the tiny output from a typical phono cartridge up into the range the your average preamp volume control was designed to operate in, you need some additional amplification. This is why a phono preamp is a separate or additional piece of equipment (or stage in your existing preamp) from your plain vanilla preamp -- it independently amplifies the signal coming from the cartridge up into a range useful for your average volume control. The gain level of the cartridge dictates how much more work the phono stage will have to do to get the signal up into this useful range. Did my layman’s understanding screw that all up horribly?