[LP1]

I recently purchased this exceptionally nice condition Art Audio PX25, but discovered that it has too much gain for my 108db bi-amped horn system, so I am selling it on. This amp would be an excellent sonic match for speakers with a sensitivity of 90db and above (e.g., Daedalus, Tekton, Zu, Omega). It's also very quiet.

Specs:

Power Output: 6 wpc

THD: less than 1%

S/N Ratio: >85 dB

Input Sensitivity : 400mV

Input Impedance: 180 kOhm

Frequency Response: 10 Hz to 20 kHz +/- 0.5 dB

Weight : 60 lbs.

There are plenty of very favorable reviews of this amp online. The new version of this amp currently sells for $17,995.

Includes original manual, double box and packing materials, AC power cord; KR PX-25 tubes, Valve Art 274B tubes, Amperex Bugle Boy 6922 and Sylvania 12BH7 tubes.









Asking $3,800 to cover my costs. Prefer local pickup due to weight, but will ship at buyer's expense. Paypal fees responsibility of buyer.

[oskar]

Wow! Art is the word.

[NoDisco]

You might to see if you can use a preamp tube with lower gain. Been there.

[poseidonsvoice]

LP1,

It might be useful in the specifications section to inform the buyer of what the overall gain of the amplifier is since you are stating that it has too much gain for your 108dB horn system.

The specs state a power output of 6 watts. I am going to assume that this is RMS and also that it is at an impedance of 8 ohms. The specs also state a 400mV input sensitivity. I am going to assume that this input sensitivity is what is needed to pump out 6 watts RMS (clipping).

So let's do the math.

Using P=V (squared)/R; where P is wattage and R is impedance. V then works out to 6.93 Vrms.

If the maximum output power is 6.93 Vrms and to reach that maximum power you need to input 400mV rms (or 0.4V rms), then gain is calculated by:

gain = 20 *dB log (X) where log X is equal to log (6.92/0.4) or 1.24.

gain = 20*1.24 = 24 to 25 dB.

So gain works out to be 25 dB, which indeed might be too much for a 108dB horn system (power being a separate issue of course). I would aim for 12 to 16dB of overall gain in a system that is that sensitive.  This is of course relative to what your source (dac, vinyl, others) is producing and if you have a preamp in the system as well. It requires a careful balance.

Pretty amps though! GLWS!

Best,
Anand.

[LP1]

Thank you for the explanation. Since my system is bi-amped, it requires that I carefully match the levels of the horn section with the folded baffle bass cabinets that are separately driven by a Crown amp. I purchased an inexpensive volume attenuator to better match the levels, but it wasn’t perfect and overly complicates things. Needless to say, I’m disappointed by the outcome as I’ve heard the PX25 in other systems and it’s an incredible sounding amplifier. Quiet to boot. But, as you say, system matching is paramount.

[LP1]

Bump

[LP1]

Price reduced to $3800.

[LP1]

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[LP1]

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[LP1]

SOLD.