I would not recommend them for most people unless you know for sure that your source has enough output to properly drive your amp even with some attenuation. Passive preamps are mainly for those who have a source with a strong output and prefer an absolute minimalist setup with as little between the source and the amp as possible. You can't do any of that with a passive preamp. It also includes features such as inverted pre-outs, which I make extensive use of to bridge some of my amps, as well as invert one channel on my others that aren't bridged (fixed by inverting the speaker wires on that same channel), which helps squeeze a bit more power out of the amps by having the bass signals on each channel hit opposite voltage rails instead of the same rails at the same time. This is before considering boost versus cut only with the tone knobs. In other words the realtive strength of signal appears strong across the frequency spectrum with an onboard pre. Active pres bring the sound 'flat and forward' if that makes any sense. My Yamaha C-80 preamp has an output impedance of 47 ohms and enough power to easily power all 6 of my amps. To my ear a fully passive bass still has a more organic sound. Suffice it to say, you don't usually see phono inputs on passive preamps. You may like/prefer it or may not.A passive preamp has limitations, such as requiring a strong signal from the source, since a passive preamp can only attenuate the signal, it can not do anything else. Active Reamp The Radial X-Amp is a dual output class-A active Reamper that lets you take a pre-recorded track and send it through amps and pedals without noise. It's a choice everyone should make for themselves. You may be looking for 'effect boxes' (the preamps that are said to be more musical to some) that may have tube amplification or LDR volume control. There are also passive amplifiers (so there is some gain) but this requires extra care with the connected loads. In all other circumstances a good active one is preferred for reasons already stated by others. When you don't need more gain and don't need to switch between XLR and RCA then a passive one might be a solution. In both cases one can choose between stepped (or relay) or stepless. If yes consider: A good pre-amp is better than a passive one.Ī passive (volume control + input selector) can be better than a mediocre or poor pre-amp.Īn active pre-amp and some passives require mains voltage. If you can answer with at least one yes you do need a pre-amp. And most analog pots, even the good ones, have some degree of channel imbalance at low volume settings, and are noisier than metal film resistors of equivalent resistance.ĭo you need more gain than just 1x ? (power amp/speakers not reaching clipping levels as it is)ĭo you need / want a physical volume control ?ĭo you need balance and tone control (on more than 1 input) ?ĭo you have a mix of RCA and XLR inputs / outputs ?ĭo you want to add 'effects' (think tubes, LDR volume control etc.) ? A passive attenuator can give you that 30 dB reduction with a smaller drop in SNR. If your listening level is 30 dB below max, the SNR might only be 80 dB. The preamp spec might say for example 110 dB SNR but that is at max volume which nobody uses. So when you turn down the volume, the SNR drops with it. Most active preamps have an analog stage that has a fixed gain ratio with attenuation. The nicer more expensive ones have 48 or more steps with finer spacing.Īs I see it, the most relevant benefit of the passive is that it preserves SNR and perfect channel balance even as you turn down the volume. The volume you want may be between steps. The cheap ones have 24 steps which are typically 2 dB apart which is a lot. Also, a passive using stepped attenuators only gives you discrete volume levels. An active preamp is more flexible and buffers the devices from each other, so you don't have to worry so much about impedance matching. A passive that doesn't meet the above conditions can be worse than an active. All the advantages of passive, and more, without the down side. The best of tube preamps beat almost everything. Tubes are a different matter all together. IF all of your upstream devices (sources) have low output impedances, all your downstream devices have high input impedances, unity gain is more than you need, the attenuator's resistance is as low as possible but not too low (10k works in most cases), and you can use short cables. The benefits of greater resolution and smooth sweet sound are offset by a certain loss of liveliness and air. I'll bet you can find it with search.Ī passive using stepped attenuators of metal film resistors can be more transparent than an active preamp, under certain conditions. There's another recent thread on this same topic with lots of opinions & advice for you.
0 Comments
Leave a Reply. |