Onkyo Preamp P-303 may be as good as EW 700C

Well,having now had the Dynavector P-75 hooked-up to the Onkyo P-303 for a week and just two hours ago switched back to the Dynavector P-75/EW Kenwood 700C,I thought I'd drop a note on my impressions.
A brief recap,the Onkyo P-303 has the best onboard phono stage of all the moving coil-capable,full function phono stages I have(I can't test the Moving magnet stages).That's out of the EW 700C,Yamaha C2x and Kenwood Basic C2.Good news for vinyl lovers.
Switching back to the Dynavector P-75(stand-alone phono stage)though this time into the line inputs of the Onkyo P-303 instead of my usual EW 700C.There is a step forward in sound quality which indicates that the phono stage of the Dynavector is sufficiently better than the Phono stages of the Onkyo and the EW 700C,that I could get far more of an idea of the potential of either unit, by using the Dyna for a showdown of their respective linestages(the Dynavector having line level output).They have better linestages than phono stages.
The Onkyo with the Dynavector stage was awefully reminiscent of what I hear via the Dyna with the EW 700C.Huge gobs of detail coming through,almost the proverbial pin dropping during a thunderstorm retrieval of info levels.I could live with this happily.The real bummer about the P-303/Dyna phono combination is that it uses the Onkyo's only line input,so if you like to put your SACD/DVD-A/DVD-V listening into your main system,you have to swap the leads over with the Dynavector each time.I can't keep them simultaneously hooked-up the way I can with the 700C and the others.:thumbsdn:
I wanted to hear the P-303's capability with SACD into the line inputs.I happen to have Elton John's "Goodbye Yellow Brick Road" both on special edtion SACD,and on a special pressing made from a metal master cut at Strawberry Studios,where the album was recorded.I also have the UK mastered pressing.
The SACD of "GYBR" sounded very good.I'm quite taken by the sound of SACD.It's relaxing.The Onkyo was excellent here and I feel that it's one and only line input is a very good one.Switching back to the Dynavector phono stage feeding the very same one and only line input,this time using the Strawberry pressing of "GYBR".Wow.Not leaps and bounds better than the SACD,but more believable,convincing,involving,and quite frankly better detailed.:yes:
I could live with either,but I'd never swap vinyl as my primary source unless a better digital source comes along or they dramatically improve cheap SACD players.The Onkyo's line input is great with high rez digital then,also.
Now here in the present I switched-back to the Dynavector P-75 phono feeding the EW 700C.
Given about a hour and a half to settle and the EW 700C/Dyna combo is doing it's superhero thing again and I realise why I couldn't wait to get back to this point.In my system they are a magic combination and this is better than anything I've heard anywhere.Fullstop.:yes:
This combination places the individual contributions of individual sound sources on the recording in their own place in 3D.It also has that involvement level thing happening.The Onkyo and the EW 700C both have massive abilities musically and information-wise,the EW 700C seems to put it all to better use in 3 dimensions than the Onkyo.That appears to be the most obvious difference.
I'd like to hear the EW Onkyo P-303.
Leave it with me.:D
 
Hardrian333 said:
The P303 is literally a straight line preamp with a MC stage with gain.
...and the 700C is a long way from this (if Tom is suggesting a passive preamp). Even the most simple signal path travels through several amplification stages on the Kenwood, all of which may say a lot more about the 700C than the P-303.
 
EW,
I read your post the first time and understood it as a compliment to the 700C,i.e the signal traverses many stages in the 700C and can still nevertheless be compared to a straight-line(possibly passive)design.
Tres complimentery.Non?

Or

The second reading and my thought was;If passive=truth,then is the "superiority" of the 700C a euphonic colouration?A result of passing through numerous stages?
Do I love the lie more than the truth?What if the lie reveals more of relevance,in addition to all the information provided by the truth,about the subject under examination than the truth?Which then should be judged practically to be truth or lie?
These are questions,rhetorical questions which could be answered either way.
I can't answer the second interpretation.I will say that given what hadrian 333 said about the minimalism of the P-303,the 700C is extraordinary as a full featured(and then some)vintage pre.
I need at least 3 line inputs,no problem for the 700C.
I feel that I will keep the P-303.I'd love to send one to EW,I think he'd enjoy working on one.:scratch2:
 
Maybe the Onkyo U30 might help your needs.

Hi guys,

When the P303 was introduced, we had a lot of complaints that it lacked the I/O required for alot of audio enthusiasts. We subsequently introduced the E-30 equalizer and the U-30 I/O unit. The U-30 added more inputs and outputs to the P-303 plus a set of meters.

u30.jpg


If you can find one on Ebay, it might help your I/O needs. Cheers!

With warmest regards,

Tom Ishimoto
Northridge Electronics
 
Tom,
Thank you for your warm regards.
The U-30 would be the ideal partner for the P-303.If they're anywhere near as hard to find as the P-303,I'll be looking for one for the rest of the year.Good to know they're out there.
EchoWars put forward the possibility of a suggestion that the P-303's preamp might be passive.Tom,there is little more information available on the 'net,other than your comments, about this Onkyo preamp.Would there be anymore one could tell us about the unit?
The only other info I've got is this:


http://translate.google.com/transla...&hl=en&ie=UTF-8&oe=UTF-8&prev=/language_tools

Thanks all.
 
theophile said:
EW,
I read your post the first time and understood it as a compliment to the 700C,i.e the signal traverses many stages in the 700C and can still nevertheless be compared to a straight-line(possibly passive)design.
Tres complimentery.Non?
Yes...Kenwood's efforts and my subsequent restoration are aimed at as neutral a sound as possible. What goes in = What comes out.
 
theophile said:
Tom,
Thank you for your warm regards.
The U-30 would be the ideal partner for the P-303.If they're anywhere near as hard to find as the P-303,I'll be looking for one for the rest of the year.Good to know they're out there.
EchoWars put forward the possibility of a suggestion that the P-303's preamp might be passive.Tom,there is little more information available on the 'net,other than your comments, about this Onkyo preamp.Would there be anymore one could tell us about the unit?
The only other info I've got is this:


http://translate.google.com/transla...&hl=en&ie=UTF-8&oe=UTF-8&prev=/language_tools

Thanks all.

I should have used my wording more cautiously. What we tried to achieve with the P303 was to produce a preamp that was essentially a "straight wire with gain". I borrowed this phrase years ago when Sony used it one of their advertisement and it always stuck with me. The P303 has gain. The input sensitivity of the P303 are as follows:

MC input 100uV
MM input 2.5mV at 100hz
High level input 150mV

The rated output voltage is 1.5V. Using the standard gain formula (gain=20Xlog(output voltage/input voltage) this translates to approximately 84 dB, 55 dB, and 20 dB respectively through various inputs. I apologize for this confusion.

There's four gain blocks in the P303. The first gain stage is the MC amplifier which is a flat gain amplifier with approximately 28 dB of gain. This stage employs 6 (3 upper and 3 lower in parallel) transistors running in push-pull configuration. The second stage is the MM amplifier which compensates for the RIAA equalization and has a gain of approximately 36 dB at 1000hz. This circuit utilizes a 3 stage complementary push pull topology where even the the first stage differential amplifier is operating in push pull mode. The 3rd stage is the line preamplifier which has a gain of 20 dB and utilizes a 2 stage complementary push pull topology. Again a differential amplifier in push pull mode is used in the first stage. A unique volume control is employed in the line preamp whereby there's 2 sets of potentiometer (1 in front of the line preamp and 1 after) to lower residual noise. The 2 sets are ganged together in the volume potentiometer assembly to act in unison. The fourth stage is the push pull buffer amplifier which has no voltage gain but enough current gain to provide low output imipedance to drive any power amplifier.

I've been asked by many audiophiles why you need a preamp. Many audiophiles use a power amplifier with volume control and can feed their high level source directly into the power amplifier. In my opinion, I see no problem with this if the power amplifier has enough gain to attain sufficient volume level and if the output impedance of your source won't degrade the sound quality by directly driving the power amplifier.

Having a preamp provides the following functions:

1. Gain to play back moving coil cartridge.
2. Gain plus proper equalization to play back vinyl using a moving magnet cartridge.
3. Source selection.
4. Line level gain if required plus any attenuation using the volume control.
5. Proper output impedance using the buffer stage to drive any amplifier.

If none of these functions are required, bypassing the preamp is highly recommended.

Essentially a passive preamp has no gain and only attenuation. A passive preamp should introduce the least amount of nonlinearity because there's no gain stage in its path. I hope I didn't confuse you.

With warmest regards,

Tom Ishimoto
Nortrhidge Electronics
 
Tom,
Thanks for your contributions here.I found the description of the volume control especially interesting.The Onkyo designers clearly weren't afraid to be novel when inplementing their ideas.Very bold.
I've heard a couple of situations where I felt that the insertion of a preamp into the system improved the sound quality.You mentioned an often overlooked point about the ability of the source unit's output stage to actually drive a poweramp,the ability to deal properly with the impedance matching.
Most sources make a lousy job of the role,which is where a dedicated preamp steps in.
Thanks to all who bothered to consider this thread.:thmbsp:

I'm going to stop doing comparisons for a while,and just listen for a bit.:music: :D

Steve.
 
My main system has a later Onkyo P-3200 preamp that I am very happy with. It works from a variety of Onkyo remote controls (RC-329S, RC-330S, RC-269S, RC-296S, RC-294S, and a few others). I have it driving the Onkyo M-5140 power amp. Also an Onkyo Integra T-4500 tuner with filter mods, and DX-C380 CD changer. The only non-Onkyo component is the Technics turntable.

:D
 
Paul,
This isn't my only Onkyo.I've got an Onkyo DVD-A digital disc player(not working)in a cupboard.Great unit.
The P-303 is a very,very good preamp.That's undeniable.
I don't know how it compares to other's in Onkyo's line,but there is one other Onkyo preamp which has caught my attention in the last week(I'm not revealing the model number),it might be worth investigating.
I'm kind of intertested in the absolute ability of these vintage solid state gems.I mean just how well do they stand-up to the best today has to offer?
I have a feeling,that much to the embarassment of those who trumpet massive improvement in the absolute sound quality displayed by the latest item to hit the market,that there hasn't been a lot of progress at all in amplifiers.
Going to listen to a $93,000 Aus system comprised of Ayre digital disc player,ASL tube preamp,Krell Poweramp and JM Lab Alto Utopia Be(plus room treatments,mains conditioning,ultra-audiophile interconnects,speakercables,powercables etc),made me rethink just how capable a lot of this over-hyped stuff is,because the system was a distinct let-down on all fronts.To put it simply it was lifeless,boring and frankly I wouldn't swap it for what I have at home.NO WAY.
The only thing the above listed system had going for it was that it was smooth and inoffensive.
When all the interest and life are sucked out of the sound,smooth and inoffensive isn't a satisfying substitute.:thumbsdn:
I'm finding that there's more life to be found in the vintage arena.It seems that I'm making enemies by daring to speak out about the lack of talent in the new product arena.
Some don't want to hear that their expensive new plaything,much lauded by the high-end salesmen,I mean journalists,is actually the naked emperor exposed.
Poor deluded souls.
 
I believe you had some interest in the companion piece to the Onkyo P303. Here's a U30 for sale on ebay:

[ebay link edited out. bully]

With warmest regards,

Tom Ishimoto
Northridge Electronics
 
Last edited by a moderator:
This will (quite rightly)be bumped to the 'Dollars and Sense' forum.

Thanks Tom(Hadrian333).:thmbsp:
 
Another ten days of listening to the EW modded 700C,has increased the gap between this modified Kenwood preamp's performance and everything else I own.
I'm chuckling to myself because it's still improving.:scratch2:
Just listened to a Bach Cantata(BVW 131) on a German Electrola label record.I've owned it for 20 years and it's one of my references for combined massed voice,orchestra and organ.I thought I knew it like the back of my hand.
Not.
This might sound over the top,but it's like all I heard before the EW700C was an outline,or a rough sketch.I don't understand;first how some gear manages to act very well as a pleasant sounding filter,second how this particular unit manages(for the first time IME)to do something which sounds obviously basic and essential,that other units seem to struggle with and fail to attain.
It's like lesser preamps are editing the signal,and the level of detriment is so widespread that one can easily conclude that because most preamps do the same type of damage to the signal,the resulting "sound" is accepted as "normal" and therefore the preamp will be accepted as being a "good" sounding preamp.
The arrival of a reference-rethink like the EW 700C throws a new light on the compromise,endemic across the brands.The Kenwood Basic C2 doesn't even hint at what's possible from the EW 700C(why can't they incorporate what they learn,trickle-down?).It's really like someone,some design team got it seriously right,then they just walked away from the arena.
Given the level of sonics the 700C can attain(and was intitially designed for)it's a crying shame that they didn't sell a million of these,because people really would(I promise)have their life enriched by hearing this level of connection with recorded music.
It's really no longer merely listening.
When I was playing the Bach piece I mentioned before,there were such a wide range of feelings,emotions,responses that I was experiencing internally as the music took me,that I felt that the instrument that the composer was initially writing for when he composed the piece was this "feeling-instrument" that was being manipulated inside me.Stirring stuff.:tresbon:
I was awed on the sonic level by the sheer extra detail,but the reward was the amazing spectrum of internal responses that this preamp enables.
If there's a holy grail in audio,this has gotta be close(not the talking specifically about the EW 700C,but that emotional connection).
The Onkyo P-303 impressed me with it's ability to connect me.That's always impressive.The EW 700C however is extraordinary.:yes:
 
I have just joined this forum having discovered it by searching Google for Onkyo P 303. I have just acquired one of these which I am using to drive a pair of Croft-modified Quad IIs. It was especially pleasant first to hear all the praise and even more so to have input from the designer himself; a rare privilege indeed!

I am using the tape return input for my Sony CD player and would be pleased to hear any views on CD with the P 303.
 
Two points.
A good phono system with a stand-alone phono stage(which outputs a line level signal),will test a preamp's line stage more than a digital disc player.My SACD/DVD-A player doesn't have the capability to bring out the best in the P-303's linestage(still sounds nice however).
The Onkyo P303 has a very good line stage.
It has a very good inbuilt phono stage,but it's line-stage capabilities are better still.
I'm having too much fun with my modified Kenwood 700C,to be bothered to hook-up the P-303.Good though the Onkyo is.
 
QUOTE=hadrian333 ... The fourth stage is the push pull buffer amplifier which has no voltage gain but enough current gain to provide low output imipedance to drive any power amplifier.
I've been asked by many audiophiles why you need a preamp.
---
With warmest regards,
Tom Ishimoto
Nortrhidge Electronics


Dear Mr Ishimoto

I have read with the greatest interest your extremely valuable explanation of the P303 circuits.
I have a question.
Given that modern CD players usually do not need voltage gain at all to drive properly a power amp do you feel that a line stage based on an high quality attenuator followed by the P303's push pull buffer amplifier could result in a even better line stage of that one present in the original P303 ?
Do you think that, generally speaking, less can be more in terms of sound quality ?
I know of line stages that are just volume pot followed by high quality buffer so with no voltage gain at all.
Just another last question: do you trust measurements or think that listening tests are the only way to judge an audio equipment?

Thank you very much indeed again for your kind and valuable explanation.
Kind regards

beppe
 
I'm a bit disappointed that the Onkyo will only work with amplifiers that have an impedance of 50K ohms or above, leaving every solid state piece I own in the lurch. My tech thinks there's a workaround by adding capacitance to the outputs so the low frequencies won't be rolled off, so I'm not getting rid of the P-303. Still, why was it designed this way?
 
winters860 said:
I'm a bit disappointed that the Onkyo will only work with amplifiers that have an impedance of 50K ohms or above, leaving every solid state piece I own in the lurch.
My tech thinks there's a workaround by adding capacitance to the outputs so the low frequencies won't be rolled off, so I'm not getting rid of the P-303. Still, why was it designed this way?
winters860 said:
Dear Sir,

Thank you for posting the inside photos of the P-303 in another thread.
It looks very well built indeed.
I think that the output capacitor mod should be reasonably simple for your technician.
As I understand that the output impedance is of about 600 ohm ( and I suppose there is a output resistor of that value) I would also replace that with a let's say 50 ohm of very high quality (i.e. Holco, Dale) or I would even remove the output resistors completely.
This mod should lower the output impedance for a better (stronger) bass response.
I would be extremely interested in getting some more information about how the P303's output buffer is implemented.

Kind regards,

beppe
 
Explanation of P303 Circuitry

The P303 was designed to work specifically with the Onkyo M505 power amplifier. The M505 has a input sensitivity of 1.5V and an input impedance of 100K ohm. Basically what this means is that for the amp to reach full power, it requires 1.5V of input signal to drive the input load impedance of the power amplifier that is 100K ohms. The front end of the M505 power amp is loaded down with a 100K ohm volume pot which is followed by a differential FET transistor. Given this criteria, the P303 had to produce 1.5V output voltage at 600 ohms output impedance to achieve low loss in voltage transfer ratio. The input sensitivity of P303 through the high level inputs were set at 150mV at 50k ohms to match up with tape and tuner output of that era to reach 1.5V at the output of the preamp so the preamp has 20dB gain. If your CD player has output voltage of 1.5V volts with output impedance of 600 ohms or less at 0db output, a preamp is not necessary if used with the Onkyo M505 power amplifier. You can use the volume control of the M505 to control the volume. However, please note that most CD players will have enough output voltage but do not have low output impedance (typically about 50K ohms) to work well directly with a power amplifier. You can get sound with this method but the interaction of impedance will invariably cause erratic results.

As for modifying the P303 circuitry to change the output impedance and frequency response characteristics, please be aware of the followiing issues:

The final stage output current capability is dictated by output current limitation of the final stage transistors, 2SA850 and 2SC1735. If you're going to lower the output impedance, make sure that they can handle the higher current. If not, replace them with transistors with simiilar transfer characteristics. Also, the 2 coupling capacitors in series with the series resistors must be changed to preserve the frequency response characteristics. Finally, due to the greater current draw to lower the output impedance, verify that the regulator circuit driving the final stage can accomodate the extra current draw without increasing the supply noise voltage. If not, modify the regulator circuitry. Also, replace the parallel loading resistor in the final stage of the preamp to match with the rest of the circuitry.

In impedance matching, there are 2 issues: gain and frequency response.

If the input impedance of the amplifier is too low to work with the preamp, there are other options to negate the effect of impedance coupling for compensation of gain:

1. Calculate the loss in voltage transfer ratio and increase the gain of the preamp or power amp by the same amount.

2. Increase the input impedance of the power amplifier. This is typically alot easier to do than lowering the output impedance of the preamp.

If the problem is limitation of low frequency response, you can increase the value of the coupling capacitors in the final stage to increase the lower frequency response. However, before you do that, I would measure the frequency response between 5-100 Hz and verify that the change in capacitor is making any difference. As with any compromise, increasing the lower bandwidth will result in more noise.

In designing a preamp, there's definitely more dimensions to it than frequency response, distortion, s/n, and sensitivity. Once you design the framework of the circuitry, the final sonics of the unit is dictated by fine tuning various portions of the circuitry. This last bit of effort is where the audible differences define the tonal and transient characteristic of the unit. Specifications tell a good part of the story but it'll only define the framework of your design.

With warmest regards,

Tom Ishimoto
Northridge Electronics
 
Wow, Tom. Thank you for the considered and comprehensive response. Truly you've gone above and beyond. We're lucky to have you here.
 
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