Just got my passive preamp from Khozmo, I have to say the preliminary experience can only be said to be fantastic, build quality wise very good, and main thing is for a pure preamp it seems very good to be literally a wire with a knob, considering the modern speaker efficiency and the great power amps, it seems that passive preamps are a great budget choice for great volume control range?
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Passive Preamp
- Thread starter YSC
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Do you have any updates or comparisons about Hattor/Khozmo?
I'm thinking about some passive input selector/stepped attenuator with remote. Looks like Schiit Freya SS might be good option while Hattor Big looks too expensive.
What about impedance matching in passive mode? No sound degradation?
I'm thinking about some passive input selector/stepped attenuator with remote. Looks like Schiit Freya SS might be good option while Hattor Big looks too expensive.
What about impedance matching in passive mode? No sound degradation?
- Thread Starter
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I don't feel sound degradation in passive mode, the series 10k ohm one works fine and the channel balance is perfect, price wise is pretty ok for Khozmo version, Hattor is too expensive though
MRC01
Major Contributor
As long as you have at least 10:1 on both sides of the attenuator, impedance matching should not be an issue. The max output impedance will be 1/4 of the rated value, so a 10k attenuator (like the Freya) will have 2500 ohm output impedance. That makes impedance matching fairly easy. Most sources have output impedances of 100 ohms or less, and most amps have input impedances of 25 kOhm or more. There are some devices that don't match well, but they are the exception, not the norm.
While 10k is a common standard for passives, 5k is worth considering as it has slightly lower noise and would be easily compatible with most solid state devices.
I really wouldn't call those devices 'preamps', since they contain no amplifying devices. "Adjustable attenuator" would be a better moniker for them. Since they occupy the position of 'preamp' in an audio system, I guess they could be called preamps (as preamp position holder) for just that reason.
MRC01
Major Contributor
If it quacks, flies and swims it must be a duck, right?
If, in addition to the volume control, it accepts multiple inputs and has a selector, then "duck-typing" says it's a preamp.
If, in addition to the volume control, it accepts multiple inputs and has a selector, then "duck-typing" says it's a preamp.
It's a preamp that doesn't amplify anything. It definitely can be used in place of a preamp that does have amplifying devices in it, though. It's still no more than a switchable attenuator. Colloquially, I'll accept the term preamp fo it. The attenuator does not quack the way a real preamp can, if called upon to do so.
MRC01
Major Contributor
Technically speaking, most people don't actually amplify with their preamp. The preamp drives the downstream amp or headphones into clipping long before reaching unity gain. Thus they are only attenuating. Some people might benefit from the preamp's buffering, if the devices connected to it have unusually high output impedances or unusually low input impedances. But that is also uncommon.
Agreed. Yet it is rare for anyone to call upon it to quack in that manner.
True, most of the time, the preamp is reducing the signal source level rather than boosting it. Difference is that the active preamp provides a lower source impedance than the attenuator does, so HF rolloff does not vary with volume setting. That's a benefit. As for those birds: they're all crazy-every last one. Did you ever meet a sane bird? I haven't. Thing is, if you can fly (bodily, not in an airplane), who cares if you're crazy.Technically speaking, most people don't actually amplify with their preamp. The preamp drives the downstream amp or headphones into clipping long before reaching unity gain. Thus they are only attenuating. Some people might benefit from the preamp's buffering, if the devices connected to it have unusually high output impedances or unusually low input impedances. But that is also uncommon.
Agreed. Yet it is rare for anyone to call upon it to quack in that manner.
MRC01
Major Contributor
With normal solid state devices, there's no benefit to an active preamp. Most solid state devices have an output impedance < 200 ohms, and input impedance > 10 kOhm. In this case you have a 10:1 or better impedance ratio on each side of the attenuator. Also, the attenuator's worst-case output impedance is 1/4 its nominal value, for example 2500 Ohm for a 10k attenuator. With common normal cables and devices, this will give flat frequency response well beyond audio frequencies at every volume level (a -3 dB point into the MHz range).
Passive attenuators aren't for every system. Maybe you have devices with unusual input or output impedances, or you need lots of gain. In that case get an active preamp. But passives do fit well in most normal systems having solid state devices.
This has been very good, but I only have a single source [turntable] and it just sits between phono stage and power amps so didn't need anything more [balance is obviously controllable here and needed in my room to some extent; and it was part of a completely dual mono / dual chassis set up from cartridge out to speakers latterly]. Good quality stepped resistors and well made. They do a variety of combinations of input/output.
