Sorry to disagree with Atmasphere, but the Quicksilver Full preamp does not suffer the usaul rise in impedance at low frequencies. The output coupling cap is 160 mfd and there is 18 db of feedback from the totem pole cathode follower to the preceding gain stage. Yes, yes that evil feedback! But in this case it is around a single gain stage and it is not limited in the low frequency range given the large value coupling cap. All I know is that it works and works well. The imaging of the preamp is phenomenal, which I attribute, in part, to the -3db point being well below .1 HZ. A very stiff power supply and high quality parts also contribute to the result.
Tube preamp output impedance at low frequencies
I'm looking to use a tube preamp with an active crossover (so as to send low frequencies to a sub), and unfortunately, most active crossovers have rather low input impedances (10k-20k). The only exception seems to be the Pass Labs XVR1, which unfortunately is out of my price range.
This being the case, I want to get a preamp with sufficiently low output impedance, to preserve the bass in my system. I know most manufacturers quote a single number for the output impedance, often at 1000 Hz, and this can differ greatly from the output impedance at 20 Hz. An example is this unit, which has Zout of 415 ohms at 1000 Hz, and 4.8k ohms at 20 Hz.
http://www.stereophile.com/tubepreamps/208bat/index4.html
I assume it would be a very bad idea to use this tube pre with one of the crossovers I'm considering. Other than Stereophile, is there any other source for tube preamp output impedances across the whole frequency domain? If I email a manufacturer directly, do they usually have this info on hand (and if so, do they have it for discontinued models)?
Has anyone else also faced this problem? If so, I'd love to hear about your experiences.
This being the case, I want to get a preamp with sufficiently low output impedance, to preserve the bass in my system. I know most manufacturers quote a single number for the output impedance, often at 1000 Hz, and this can differ greatly from the output impedance at 20 Hz. An example is this unit, which has Zout of 415 ohms at 1000 Hz, and 4.8k ohms at 20 Hz.
http://www.stereophile.com/tubepreamps/208bat/index4.html
I assume it would be a very bad idea to use this tube pre with one of the crossovers I'm considering. Other than Stereophile, is there any other source for tube preamp output impedances across the whole frequency domain? If I email a manufacturer directly, do they usually have this info on hand (and if so, do they have it for discontinued models)?
Has anyone else also faced this problem? If so, I'd love to hear about your experiences.
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- 18 posts total
- 18 posts total