This review may not be a fair one.Soley based review with the preamp completely re-capped by me.I used nothing but good quality capacitors.In original form it was too dry sounding with not much dynamics.This applies to most commercial offerings in my opinion--they tend to have great designs but use crappy capacitors to cut cost.This in turn holds back the true potential of sound a lot of this equipment is capable of.
I purchased it in absolute mint condition.I re-capped all 3 main boards(power supply,flat amp,and eq board).Now,this preamp is showing some potential.It does not excel in any particular area.It's very quiet and smooth sounding.Neutral to the core in my opinion.Bass is now fast and tight with no overlays in sound.
The mids are not as forward as I would like but very acceptable and smooth.The treble is not elevated..in fact a little bit recessed and not so bright,however,the preamp is still able to retrieve detail in music which is always a good thing.
I'm not sure what year mine is from.I imagine somewhere between 1986-1992.I could be off by a few years.Upon,taking it apart I noticed it used nothing but Nichicon vx series capacitors.The entire circuit and design was thoughtfully laid out and professional.I used Panasonic fc,Rubycon zl,Blackgate,Elna Cerafine,and Elna Silmic II capacitors with some bypassed with polypropylenes.By doing this myself it brought out the detail that was normally suppressed in it's original form.
Now,it can breathe and perform as it should.Simply sounds much better and glad I am now the proud owner.I'm not one for neutral sound but this preamp changed my mind on that assupmption.It's very quiet and lets the music flow freely without and overload of coloration.
I brought this thing home on a whim, and after dusting it off, I can tell that it was hardly used. This P-304 blew away my Bi-fet pre-amps that I had modified for a pretty penny. A true no frills line level pre-amp, w/MC input for all you vintage guys. The tone control can be defeated, but they are actually usable, due to their unusual contour. The manual explains this feature thoroughly. If someone can modify mine to be rackmounted in a 19" inch EIA audio rack, call me today. 812-466-5952
Truly, sound as it was meant to be heard. Before purchasing the 304, I had been using a $2000 plus preamp. After hearing my friends system, we swapped preamps. The 304 blew my amp away. I made him a swap offer which he refused.
After a short search, I located a 304 for sale and jumped at the $300 ticket. Now, I experience sound - as it was meant to be heard.
The operative phrase here is "Quality where it counts most." ...You will not find more bang-for-the-buck,which seems pretty typical of Onkyo and Integra product lines,all in all. Articulate,warm-but-not-soggy,tuneful,integrated flat response,tight-not-boomy,extended highs,black-silent,inner detail,fast transients,tracks the decay of notes way across and down,and more..,yes,yes,yes,yes,yes,yes,yes,yes,yes,yes! !! I bought this preamp primarily as a headphone-amp of sorts with the unusual advantage of numerous inputs for all needs inclusive. And boy,the jack on this baby really does deliver music that is clean and quiet and just...WOW! For Grado headphones I only need about 8 O'clock volume (about 30 ohms),and about 10 O'clock for my AKG K-501's (about 130 ohms),and I'll bet this preamp-jack has enough power to run Sennheiser 600's (about 300 ohms),although I have not tried this. The dead-quiet characteristics of this preamp make it ideal for headphone use. I plan to one day match it up with a tube-amp one day for speaker use,and I am sure I will be just as happy with the results then as I am now.
I have used many High-end preamps over the years,some sounded great most only so-so.Almost all of them were a pain in the rear to use;they either had no phono (rip off),no tape outs(contaminates the sound don't ya know,I guess buffers are beyond them),no switching to speak of,no tone controls (sacrilege!),are poor in reliablity (NAD and most tube preamps) or have horrible human engineering (twin volume controls ,weird box shapes so that no way can they fit on a shelf).Of all the High-enders that I have used, only the Spectral was worth the pain it put me thru. Its sound was truly first rate into almost any amp. Alas at the end of the speaker project it had to go home...
Then along comes this little Onkyo P-304. I have long known of Onkyo's rep in the Audio field (owned one of their better cd players,it was built like a tank and sounded fine). Circuit city had just put their demo unit up on the clearence rack for $129...no one there even knew what it was. So thinking what the heck,it can be a backup,I purchased it. Second best buy I ever made (got the Threshold for $30.
I set it up,turned it on,and went out to eat. After getting home I put on some music,it sounded nice but a smidgeon grainy like the Van Alstine pre-amp (bad tubes). I left it to cook for the night and came back to it the next day. Now it was singing! Bass was very deep,giving the subs something to work with. Bass attack was quite nice tho not in the Spectral's league ($5000). The suprise was in how good the bass decay was,the overtones were very natural and blended with the rest of the music beautifully. This was not one-note bass,it was very tuneful ,had really good pace and rythym and really made me want to dance (too bad I cant). The mids were very nice with voices layering nicely,male voices sounded real with an honest low frequency foundation. Female voices sounded a little harsh on the very top,sort of mid fi, compared to the Threshold but still had nuance and subtlety. All in all very enjoyable.
The switching was silent and,amazingly,had no audible crosstalk between input;ie,I could have a CD playing on one input and have absolute silence on the one next to it. There was no hiss or hum,not even on the phono stage. And the tone controls! They actually work where they are supposed to! Amazing! I spent 20+ years living a hair-shirt existence of having to listen to badly recorded music on flat pre-amps because tone controls were only for the great unwashed masses...and yet, only the Spectral was good enough to justify their absence.
I opened the box and was very impressed. Mind you I saw no gold traces or wondercaps or unobtanium wire. What I did see was a massive power supply (It alone was worth more than I paid),neat wire layout,and nice, tho not audiophile grade,controls and switches. And I saw great engineering for the price point (the original $700+ one). I have no idea how they did it.
And then I tried the Onkyo with the Van Alstine Fet-Valve 300i....magic! Every good thing about the Onkyo got better,and the mid-fi harshness on the top vanished. Completely. The Threshold could still beat it on top,in terms of detail and ambiance,but the grit was gone. What was left was a sweet presentation of sound,involving to both the body and the mind,the sort of thing that I would have paid plenty for if any of the high-end stuff delivered. In fact it beat the Threshold rather badly in this department. The Phono stage was very quiet and seemed to love my audio-technica moving magnet cartridge,presenting good dynamic contrasts and excellent harmonic structure and ambiance with no trace of dryness...good enough at least to demonstrate the superiority of (some) analog over (some)digital. Sweet!
Now what was happening is that the Onkyo,in order to get those great specs does use pretty high negative feedback (by high end standards),which is one of the reasons for its absolute silence. This can react with the input of most solid-state amps,often producing that mid-fi sound (at least it was very slight on the Onkyo).But the Van Alstine presented an almost perfect resistive load,allowing the preamp to think it was on the test bench feeding a simple resistor.
Someday I will get around to modifying this preamp...but not anytime soon...The Onkyo P-304 has great sound,great flexibility,is pretty, and is a joy to use. Which is exactly what a lot of high-end pre-amps arent.