Resistor in phono stage


Hi there,I have a audio research ph3se.I bought it of ebay,so i dont know if the correct resistor is in place.What would be the result of the wrong one fitted,thankyou.
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The wrong resistor will give you the incorrect loading for the phono cartridge you're using with the PH3SE.
Thanks,would that effect the sound as too bright,too flat,Im not sure.
What do you mean by "wrong resistor"?
What cartridge(s) are you using, and by what criterion do you think the load resistor is wrong?  If you have an ohmmeter, just stick one probe into the RCA phono input jack and place the other probe on the outer barrel of the RCA jack; the resistance thus measured will be the value of the load resistor, unless there is a SUT in the signal path.  I don't know what the value should be for the PH3se.  The standard for MM cartridges is 47K ohms.  MC cartridges typically are run with more of a load (meaning a lower value of load resistance, down to around 100 ohms in some cases).  
The ARC PH3SE in a MM only phono stage.  It has a factory set fixed output of 54db gain, 47Kohm impedance and 90pF of capacitance.

You can change only the capacitance by soldering in different values of resistors.  I would make sure if this has even been done.  I have owned several of the PH3 and PH3SE units and none of them had ever had a resistor soldered in.

Here is an excellent white paper on loading:

http://www.hagtech.com/loading.html

Mofi, baby.  Thanks for the info on the PH3SE. Of course you CAN change the 47K load resistor by directly de-soldering it, removing it from the circuit, and replacing it with another resistor of preferred value.  Many listeners prefer a 100K load resistor for most MM cartridges. (See the thread on MM cartridges.)  Anyway, I think you must have misspoke by suggesting you can change capacitance by changing the load resistor. No problemo.

Certainly, 47K cannot be regarded as the "wrong" resistor for an MM. We now need to know what cartridge the OP is using and whether he is using a SUT between the phono and the cartridge. Etc.
Page 2 of the PH3 owner's manual talks about changing Input Impedance and Input Capacitance:

http://www.audioresearch.com/ContentsFiles/PH3%20manual.pdf



Thanks, mofi. What I see is a description of how to wire resistors (and/or capacitors) so they end up in parallel with the input, which will effectively lower the input resistance (and/or raise the input capacitance).  Thus, the end user can achieve nearly any resistance desired, below 47K. (Resistors wired in parallel will always result in a net value lower than that of the highest value of any one of the resistors.)  Adding a capacitor in parallel, using those same binding posts provided, will raise the total capacitance, since capacitors in parallel are additive in value.  (Pardon me if you already know this.)

But meantime, the OP seems to have lost interest in his own question. Which is fine.
Lew, when you said "resistors wired in parallel will always result in a net value lower than that of the highest value of any one of the resistors," you probably meant to say "resistors wired in parallel will always result in a net value lower than that of the LOWEST value of any one of the resistors." Both statements are of course true, but the second one is more meaningful.

Also, Mofi, the manual you linked to talks about using the phono stage in conjunction with moving coil as well as moving magnet cartridges. While 54 db gain is of course too low for many LOMCs in many applications, depending on the noise performance of the phono stage and the gains and sensitivities in the rest of the signal path I suppose it could sometimes be suitable for use with cartridges having relatively high outputs within the LOMC category.

In any event, as Lew indicated further info from the OP is needed before his questions can be answered.

Best regards,
-- Al

Thankyou guys,Ive been a bit busy.Im running a supex 900 super mk2.I had it on a zeta tonearm on sota sapphire. Unpacked after 6 years in storage ive put the supex on a sumiko mdc 800 and a mk4 sota sapphire. Using a ar ph3se.Things seem a little brighter on some records.Awesome on some others.I was just wondering maybe the impedance had been changed by a resistor.Process of illumination, if you like,thanks again
Iam using a cosmos armboard.
It looks like that cartridge is an LOMC having a rated output of 0.2 mv. It’s surprising that 54 db of gain is adequate with such a cartridge, but on the other hand the noise specs on your phono stage seem quite good ("0.1µV equivalent input noise, IHF weighted, shorted input; 80 dB below 1mV 1kHz input"), which figures to be helping.

In any event, with a 0.2 mv cartridge it’s hard to predict how sonics would be affected by variations in load resistance, as it would be highly dependent on the design of the particular phono stage, and specifically on the sensitivity of the phono stage to RF frequencies. (The interaction of the relatively low inductance of such a cartridge with the capacitances of the phono cable and phono stage input will result in a resonant peak in frequency response somewhere in the RF region, whose amplitude will be affected by the load resistance).

So I suspect that the only way to determine an optimal load resistance would be to try a few different values, although it’s possible that you would find it to not be particularly critical. One thing I would make a point of doing, though, is opening up the unit and seeing if someone has put capacitors on the loading terminals that are indicated in the manual. That might have been done if the phono stage had been used with a moving magnet cartridge having a relatively high recommended load capacitance. If you find that capacitors have been added, it would be best to remove them given that an LOMC is being used.

Regards,
-- Al

Al, Thanks for the correction, my bad.  Thanks also for giving me the easy way out. I was plain wrong, but it was due to brain fart.

Misternice, there are some who say that any MC should work fine into a 47K ohm load, and there are others who load down MC cartridges (which is to say they load the cartridge with a lower resistance) and swear that their choice is superior.  In principle, there is no right or wrong.  I only recently experimented with 47K as a load on some very low output MC cartridges, and I find that I cannot go back to the 100 ohm load that I previously favored.  The sound is just more open and effortless, in my system, with my cartridges and phono stage.  Ralph Karsten has pointed out that the phono stage itself is most affected by the load resistance; the cartridge doesn't care much until you get down to very low resistance loads, where now you are losing signal voltage to ground.  That reduces gain, and to my ears seems to roll off treble, both of which phenomena make electrical sense.

A wild card in your equation is the fact that you stored the cartridge for 6 years.  That may have affected compliance.  Give the cartridge several dozens of hours to loosen up before making critical judgements.

Vinyl Engine says that your Sumiko has 11g effective mass, with the "L" weight.  I found some comments on the internet to the effect that the Supex "likes" a high mass tonearm, which the Sumiko is not.  (11g is in the low range of "medium" effective mass.) Maybe that is a source of your dissatisfaction.  But I would do nothing until the cartridge has had a chance to break in.
Ok,thanks for that.
Im using the H weight on the arm.Im thinking it could be a combination of several things,not necessarily the resistors.Ive used a spin cleaner on my records for the first time,and that has changed what im hearing too,for the better,room acoustics,hifi rack,speakers,powercords, interconnects,etc..I will give the supex more time to settle in.Not a bad little cartridge,i must say.Using the a supex step up transformer of course.cheers.
Using the a supex step up transformer of course.
Ah! Which of course explains how the 54 db gain of the phono stage suffices for use with a 0.2 mv cartridge.

But it also adds to the possibility that either resistors or capacitors a previous user might have installed in the phono stage could be an issue. For example, suppose a previous user had installed 1K resistors, for use with a cartridge having a rated output in the upper part of the LOMC range. And let’s assume that your SUT provides a gain of 10:1. That would mean your cartridge would be seeing a load of only 10 ohms, which stands a very good chance of being low enough to result in the adverse effects Lew referred to in his previous post that can occur when load resistance becomes excessively low.

From the perspective of the cartridge, use of a SUT also greatly increases the effects of any capacitors that might have been installed on the loading terminals within the phono stage. Which as I mentioned earlier could conceivably have been done to conform to the loading requirements of some moving magnet cartridges.

So I would definitely open up the unit and take a look at what if anything has been installed on those terminals.

Regards,
-- Al


With SUTs, it is the loading of the transformer to prevent ringing and also to allow it to express its turns ratio that is important.

If loaded with a value too low, the highs will be rolled off. If loaded with too high a value, there will be ringing, which is say distortion, most audible as being bright and in your face.

Low output cartridges by themselves are insensitive to loading. Its the SUT and and also the preamp where the loading becomes critical.
Awesome guys.You probably helped alot of us out.thanks
Hi,just letting you know.Everything under the hood appears to be standard.Over the last few weeks,ive weeded out 90 odd records.I now believe my problem was,,,with moving up the transparency ladder,my record collection needed adjustment.With a good recording Im very happy with what Im hearing.It is a little strange how a old new record has lost something.Anyway,I think im on the right track now.thanks
Good advice above. Also important is exactly which brand and type of resistor and capacitor you use. I prefer nude Vishay VAR resistors, available from Parts Connexion. For capacitors, styrene film and foil from Relcap, or just about any source, sound best to me (also available from Parts Connexion). Teflon caps can sound a bit hard, but not styrene.

I certainly agree about the (subtle) effects of resistors and capacitors, in any circuit, but in this case the issue of cartridge loading, if it were to be an issue, is dominant over parts quality, in my opinion.  Once you skew the frequency response, boutique parts are not going to fix that (unless you also change values to correct the frequency response).
misternice, I've left comments to those who know more about electronics than I do.  But now I must ask, have you experimented with VTA?  Some cartridges with some records can sound bright (as you reported) when set up with the standard parallel to the record alignment.  Lowering the tonearm a bit to tip the cartridge back can sometimes help.

I guess it depends if there was any music in those 90 records you'd like to retain.
Thanks,ill swing back and play with the VTA.Ive been running the arm horizontal to the record,and left it there. 
@lewm 

Agreed. But if you value the OP's time at minimum wage or higher, he might as well use the best. Just my view.