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What is the difference? And how can I tell if the phono section has either one?
Thanks
Follow Ups:
What passive phono preamp are you referring to that is causing you to ask this question?
I am using a Quicksiver phono preamp with a Quicksilver linestage preamp. I asked the question because I was not sure if the phono preamp was active or passive.
Active EQ has the equalization network in the feedback loop.
Passive equalization does not, being composed of filters made of passive components that are in series with the signal. This allows for a zero feedback design, although that gain blocks in the phono section may well employ feedback independently of the equalization.
Without a schematic of the circuit it can be tricky to tell which is which just by looking at them- you might have to ask the manufacturer in that case.
Passive Phono EQ networks usually get grounded; usually easily visibly recognizable or easily checked with an ohmmeter. Active (Feedback) Phono EQ networks are not usually grounded; but go from a later tube stage then fed back to an earlier tube stage with frequency selective networks.
The order of the active/feedback EQ filter networks, meaning which frequency range is affected first, the high cut EQ network or the bass boost EQ network, seems very important for a given design. Retaining the "timing of the music" is very critical. Most of the classic preamps with feedback phono EQ networks start the feedback path with the High Cut network then the Bass Boost network in series, with the bass boost nearest the earliest preamp stage. I like that almost standardized approach from the vintage era since the noisy highs get filtered first; then the bass boosted.
Passive EQ, using filter networks to ground, can also please the ears. Speed and articulation are common buzz words for progenitors of passive EQ phono stages. However, the original timing of the "hits as we remember them" might be "different" sounding...only sound testing can reassure. As many of the '60s and '70s hits were actually cut onto disc with an active feedback network within the cutting amp, using either RC networks or LCR networks, the esteemed LCR EQ network equipped Passive EQ preamps are gaining favor.
Of course, among veteran record collectors who happen to be audiophiles as well, the active feedback phono EQ has never lost it's favor...but that will probably be another thread...ENJOY !
If you look at the schematic, the passive EQ has no feedback loop.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
The other difference is that an active RIAA requires that the gain device be at the same gain for the curve to remain accurate, no so w/ a Passive EQ.
Happy Listening
Agreed. No gain in a passive pre-amp of any kind.
Transformer based passive preamps have gain.
My AudioZone has 6dB and 12dB gain settings, although 0 & 6dB are more common.
Don't think there are passive phono preamps. The purpose of a phono preamp is to provide gain, which a passive unit doesn't.
The purpose of the phono preamp is to provide a very precise filter, called RIAA equalization, to the signal from a phonograph record. The filter boosts the low frequencies and attentuate the high frequencies on a specific curve with points along the curve at 50Hz, 500Hz and 2122Hz.
This RIAA equalization can be passive or active meaning that the amplifiers used to drive the filter can have the passive components either between the stages of amplification as in passive or within the feedback network of the driving amplifiers which would denote active.
A passive filter can not boost anything above the input signal, only active circuitry can do that.
In order to get the RIAA curve an ideal passive filter leaves the lowest frequency alone and applies varying amounts of attenuation to all other frequencies.
You can probably use a transformer to boost voltage at the expense of current and vice versa.
"A passive filter can not boost anything above the input signal, only active circuitry can do that."
Read my post again:
"the amplifiers used to drive the filter can have the passive components either between the stages of amplification as in passive or within the feedback network of the driving amplifiers which would denote active."
It should be obvious that gain stages are required to drive the passive filter network.
By the way it can be both 1/2 active and 1/2 passive.
with a 1 mV input sensitivity. ;)
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