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snakeybyrne
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Joined: Feb 14 2011 - 12:14pm
Tube pre solid State power impedance issues

Anybody got suggestions on a Tube pre to match my soon to be delivered Electocompaniet Nemo's. They will be running B&W 801d's from a Orbe TT origin Live tonearm and Lyra Delos cart. I am after a more engaging sound, not fatiguing. Warm but with enough detail and transparency to be able to hear right into the recording. Must be able to be comfortable with a wide range of genres, expressly Classical and Jazz. What Comes to mind are preamps from PrimaLuna, Cary etc.

Any thoughts/suggestions would be much appreciated.

jgossman
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Joined: Aug 18 2011 - 6:21am
This is an old post...

But I think it's worth a bump. It's not going to be a problem. There is some issue with these combinations being bass shy, but that's usually because the designer uses too high a value coupling cap on the output. This leaves a tube preamp sounding more detailed while still sounding pleasant because it will sound "solid state" without the edge of some bright solid state gear. This is usually easy to get around, see how much DC is on the output at the input lead of the coupling cap and if it isn't more than a few volts, look for an input cap on the amp. If the amp is capacitor coupled, get rid of the output cap on the preamp. Just be ready to put it back in when you sell it. Caps are a high pass filter, that's why many of the most detailed monitors just have one cap on the tweeter.

SAS Audio
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Joined: Jun 6 2007 - 6:56am
Lack of Bass, Corrections

The preamp output coupling capacitor and amplifier input impedance (Z) form a high pass circuit.

The smaller the preamps output coupling capacitor, the less bass. The larger the output coupling capacitor value, the more bass, up to a pre-determined design criteria response.

To OP: The vast vast majority of amplifier designs do NOT have an input capacitor, so please do not assume it has one, actually check. If a mistake is made, ridding the preamplifier's output capacitor places a high DC voltage on its output, on the interconnect cable (ic), which could kill you, and on the amplifier's input. Not good.

Another consideration is the amplifier's input impedance (Z) vs the preamplifier's output coupling capacitor value. As the amplifier's input Z lowers, the preamp's output capacitor value must increase for the same bass response.

As an example, a 10k ohm amp input Z requires a much higher value preamp output capacitor than an amp with a 100k input Z. (Z is considered midband.)

General consumption: A caveat, nearly all film capacitors are not accurate, so be careful of the brand.

With that in mind, capacitor comparison articles one sees on forums etc are not only worthless, but detrimental and misleading.
Simply installing a capacitor in a circuit/component and listening is Not the proper way to test a capacitor.

1. The circuit design itself has not be specially listening tested for accuracy. Virtually none are accurate, thus biasing the results.

2. Every singe part in a correct design has to be specially listening tested for accuracy.

2. The value of the capacitor needs to be the proper size for the particular task in the circuit. Too large or too small will completely invalidate the results.

Simply installing different capacitors, of the wrong size, in a questionable circuit will not lead to the most accurate capacitor in absolute terms.

cheers

steve

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