![]() Holy freaking crap! Now I have had some decent preamps: Spectral DMC-5, Spectral DMC-6A, Spectral DMC-15, Threshold FET 2, Threshold FET 1, Threshold FET 10HE, Moore Franklin Magnus, XiangSheng 728A, PrimaLuna Prologue Premium, Crown PLS-2, PS Audio 4.6, PS Audio 5.0. I just got a Mod Squad Deluxe Line Drive. IMO it does a superb job in my high resolution system. I am currently and have for several years been using a DIY HI-FI SUPPLY Django with super-permalloy trannies. Tube amps, in general, have much higher input sensitivity than solid state.īest case scenario is an output source with well about the industry standard 2v (mine are about 3.5-4v) a tube amp with input sensitivity of 1.5v or less (mine 1.25v), and speakers 90db efficient or better. Higher sensitivity speakers makes a big difference also. The output of the source must be high enough to easily drive the amp to full output. There may be others but IMO these are the main ones. Output level of the source (as well as output impedance in cases of unbuffered passive) To successfully use a passive one must take a “system approach.”Ĭonsiderations starting with the source include:ġ. I’ve tried many different ones and all different types settling on transformer or autoformer based units long ago for their purity of sound and lack of some of the problems possessed by other types. I’ve been using passive controllers almost exclusively now for the last 20-25 years. I did modify my amp for higher input sensitivity which helped. Shortly thereafter then came out with their own version. The guy at DB told me it wouldn’t work well and was not a good idea. You may like/prefer it or may not.Built my own “passive pre” in 1985 using a DB Systems switch box and a blue Alps attenuator. 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. 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. 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.
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