active or passive preamp for active speakers

the measured input resistance (DC) for the Dynaudio BM5A was 100Kohms.

While for my taste a passive like the Lightspeed Attenuator (I have tried many others) is better than any active, as Al says it has to be in the right system. It seems that you system may not be ideal, not only because of cable lenghts, but I suspect the SS amp in your speakers are low input impedance. I also think that passives work better with tube amps in general in terms of impedance and sonic character. As you point out, you will certainly have more flexibility using an active preamp - with you current equipment and down the road.

Pick the lowest hanging fruit first...

Passives are pretty cheap and if your system likes it, almost unbeatable.

IME, it is extremely difficult to find a transparent active preamp, I have tried a lot and they all add to the sound too much, or take too much away from the music.

If you want to go active be prepared to spend a lot of money to get a transparent design.

A couple of suggestions: I have a B1 active no gain preamp from First watt, I cannot tell the difference with a passive preamp, which says a lot! No gain, but high output impedance so it turns out it has less drive than a passive...

Placette Active and passives are great.

The Best active preamps I have listened to are The Essential, and the top of the line Metaxas preamp. Amazing both of them and they clearly beat a passive in most ways, including transparency.

I'm in the same boat. I have a pair of active Dynaudio BM5a monitors that I use for Home Audio. I've tried several active pres it seems to affect the signal in a negative way (less clear, thinner, hazy). Using a Digital Link III balanced straight into the Dyns is magic, now just to get the same thing with my analog signals with some volume control (Phono and Analog out SACD) into the Dyns. Im thinking of using a Passive Pre on those two channels. I just need to control the volume and be transparent. No gain needed. Any thoughts or suggestions welcome....

Theron

thanks again for the responses.

almarg, i really appreciate your detailed reply. based on your reply i think it's safest to go with a non-passive preamp, especially if i want to use it in a different system down the line.

now over to the preamp 'for sale' section...

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Can you solder? You can build a passive preamp for about $10-20 worth of parts from Radio Shack.

Google "passive preamp diy" for info.

Build a cheap one and if it meets your needs you can obsess about buying expensive parts for your next one.

Pay no attention to the naysayers. Passives ARE ideal for some systems. ALL volume controls are passive so if it suits the criteria as Almarg laid out it may be all you need.

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i guess i don't understand the purpose of the preamp. since my active speakers don't have volume control, it seems the only thing i need a 'preamp' for is volume control, assuming at least that the signal coming for the cd player is strong enough. and if i hook a tuner up too, then it would need to switch between sources.

so why not a passive preamp to do those simple jobs?

For a passive preamp to provide good results:

1)It has to be driven by components having low output impedances. That is probably not a problem here if the cdp and tuner have solid state output stages, although it could be a problem if either component has a coupling capacitor at its output, which most tube source components and some solid state components have.

2)The amp or active speaker that it drives has to have an input impedance which is high in relation to the passive preamp's output impedance (which will be much higher than the output impedance of a typical active preamp, and will also vary with volume control setting). This might be a problem here -- the input impedance of the BM5AMkII doesn't appear to be specified.

3)The passive preamp has to be connected with short lengths of low capacitance cabling, especially on its output side, but the input side can be important as well. That may also be a problem here, depending on your setup and on no. 5 below (which determines how much capacitance is acceptable).

4)The gains and sensitivities of the components in the system have to be such that the preamp does not have to provide any gain (i.e., any gain greater than 1). That is probably not a problem here. With the tuner, and perhaps also with the cdp, you will probably not be able to drive the speakers to their maximum possible output level with a passive preamp, but you probably wouldn't want to.

5)The architecture and resistance value of the passive preamp have to be carefully chosen in relation to the impedances of the components it is connected to.

The bottom line: I would not proceed in that direction without first somehow determining the input impedance of the active speakers.

Regards,
-- Al

It's not a simple job. The aspect you're forgetting is control in the electrical sense. Impedance, cables, that sort of stuff. The other thing is that you will likely have to convert from RCA inputs to XLR outputs.

I generally don't like passives, but both of my present amps have passive pre amp sections and I've yet to find an active that improves upon their sound. Yesterday a shindo was a disappointment with my torii.

That said, I'm still looking.

thanks for the responses.

i guess i don't understand the purpose of the preamp. since my active speakers don't have volume control, it seems the only thing i need a 'preamp' for is volume control, assuming at least that the signal coming for the cd player is strong enough. and if i hook a tuner up too, then it would need to switch between sources.

so why not a passive preamp to do those simple jobs?

Active is not ideal and never will be. Sorry, had to say it.

Passives are system dependent. Some people select surrounding components around them wisely. Some get lucky. Some, usually the most vocal about it, don't get lucky. Although, if you've seen the length of the Lightspeed thread, passive fanboys aren't exactly passive either. Don't get me wrong, passives are designed to be compatible in most systems. Very basically, the source has to drive the amps with a passive volume control.

With your long XLR's and limited flexibility, you're chance of luck is less than average. Off the top of my head, I can only think of Bent, Goldpoint and Promitheus offering balanced passive models and only one of those has remote control.

BTW, saw a PS Audio PCA-2, one of my favorites, for $800 on the listings.

Passive is not ideal and never will be.