Amp-preamp mismatch?? result higher volume. What is rthe cause??


Several months ago, I changed amps from a BAT VK200  to a P.S. Audio S-300 amp. I also invested in a new interconnect, the Audience "Ono"  which replaced  a basic Harmonic Technology " Truth Link" which is used  now between the preamp and the CD player  The P.S. Audio amp is very dynamic  but also more forward, but not aggressive 


Pre-amp is a Conrad Johnson PV-14SE and which I like very much 9uses two tubes in the output stage.  The current combo of interconnects has sounded louder (and more forward in the midrange) at the same volume setting used before with the BAT amp  To its credit, the P.S, Audio provides better detail and depth in the midrange than former BAT amp  


So, is there an impedance mismatch between the power amp and pre-amp??   Or  is the increase in volume a consequence of a mismatch between the interconnects, either to the amp or the connection between the amp and pre-amp??


Please advise.

Thank you

S.J.

sunnyjim
Most likely a difference between the input sensitivity of each amp.  Check the manual


There’s no impedance mismatch as the P.S. Audio S-300 amp is 50k input impedance with 1v input sensitivity. Should not load down any preamp.
The problem could be the PS amp itself, if that pre was fine with the other amp, was it purchased new?

Cheers George
Its not a mismatch, nor is it a problem. Few things in audio are as irrelevant as the position of the volume knob. Unless for some odd reason you think it matters. Like this guy-  https://www.youtube.com/watch?v=4xgx4k83zzc
The PS amp’s sensitivity is lower (1.01 vs 1.6V) for it’s (higher) rated output/gain, compared to the BAT.             +1 (each for testpilot, millercarbon and twoleftears)
For amp designers volume knobs totally matter.   If you are running your volume control down around 9 o’clock, you are actually throwing away signal level so that a subsequent gain stage can make it back up.
If you are running your volume control down around 9 o’clock, you are actually throwing away signal level so that a subsequent gain stage can make it back up.
This is correct.  And there are actually some preamp that just don't give a good quality audio signal if the volume/gain is set so low.  They really work better and higher signal levels, so if your volume is not up in the 11 o'clock to 2 o'clock level, you may not be getting the most out of your preamp.


While a lot of power amplifiers do use a conventional amount of gain (23 dB? 28? something like that) it’s not a

requirement. Preamps tend to vary a lot more in the internal total gain, and for sure, you can’t compare volume knob direction between them, as nothing is standardized.

I do wish preamps had a lot less gain though. I’d like to have more control between off and 12 o’clock.
High gain preamp to high gain amp problem.
When so, best to have gain adjustability in either to ensure an optimal volume range (my pre’s at 10 - 2 o’clock).
Otherwise, you can get attenuator cable made (-6db or -12db) to go in between i/c from pre to amp.. Shaves off a bit of quality, but worthwhile (in my old case) than having system already playing too loudly with volume barely touching 9.
Sticking with my preamp, ever since, I’d only consider amp/s with gain adjust (or low gain ones, preferably below 20db).
I'm so confused now by all of these sensible and well-informed comments. 

because Einstein said:

Few things in audio are as irrelevant as the position of the volume knob.

How do we reconcile such disparity? lol  
While a lot of power amplifiers do use a conventional amount of gain (23 dB? 28? something like that) it’s not a

requirement. Preamps tend to vary a lot more in the internal total gain, and for sure, you can’t compare volume knob direction between them, as nothing is standardized.
Okay, you guys are confusing preamp gain with amplifier gain.  These are two completely different things.  First, the typical amplifier gain is somewhere between 28 db and 32 db for a normal amp.  This describes how much increase the amp naturally "amplifies" from the input voltage to the speaker output voltage.  Some amps are set at lower gain such as 23-24db and cater more towards extremely high efficient speakers.

Preamp gain is completely different.  You cannot say that the preamp is adding gain to the input signal.  For example, your DAC output is generation about 1.2 volts.  The preamp is not going to increase this on its output.  In reality, it typically outputs a much lower voltage (which depends on where you set your volume control).  It could potentially output 1.2 volts (that would be something like max volume) or even higher than the 1.2 volts it sees on the input.

That being said, preamp gain is an internal function of the audio stage / op amp.  It is almost always based on a negative feedback circuit.  The 1.2 volt input signal is actually de-tuned down to something like 0.05 volts by an input resistor (or whatever the engineer decided to de-tune).  Then the gain circuit re-amplifies the signal back up to normal levels.  This "re-amplification" audio stage helps with the current required to drive the input stage on amplifiers.  The "amount of gain" that actually occurs in the preamp is really dependent on how much "de-tuning" happens on the input signal.  This varies from preamp to preamp. 

There are two scenarios with volume control.  The volume/potentiometer could be an active element in the negative feedback which directly controls "how much gain" the audio circuit is re-amplifying.  Or the volume/potentiometer could be located after the gain circuit, in which case it is just reducing the voltage generated by the gain circuit itself.

It's also important to know that preamps with a "high gain" will usually have more hiss/noise in the background of the signal.  This hiss/noise is a byproduct of high gain circuits and there's really no way around this.  If you have extremely efficient speakers (such as 100db Tektons or something), then this hiss will really become apparent (even if you are not playing any music).

Thank you to all have responded  The P.S. Audio S-300 has no volume pots on the back; I think the S-700 does. Nevertheless, the comments are useful, even the humorous one.  For the record, the C.J preamp's remote is graded 1 though 99. and is very smooth acting. Generally with the  BAT amp, I set the volume  at  50 which was fairly loud ( my speakers are the Golden Ear Technology model 7 whose efficiency is about 88-89 db)  With the PS Audio amp, I use the volume at about 44-46 on the remote to get approximately the same volume as with the BAT amp, depending on the recording.   The "number 11" setting would not wake up a mouse in the  underground garage (LOL)


Cheers and Happy holidays to all...