Audio Research PH5 Phono Preamplifier Input Clipping Problem


I have an ARC PH5 phono preamplifier and most of the time it sounds fine.  But on a few of my favorite LP's with wide dynamic range, it will clip and distort on loud sections, especially those with lots of bass content.  This only happens with use of a step-up transformer, without the SUT in line, there is no clipping. I do prefer to use the SUT, as without it I have to turn the volume setting on my ARC REF 3 preamp to a very high level.   I have to conclude that the PH5 is distorting because of high input signal levels, due to the gain of the SUT.   I have tried two SUT's, one with 13:1 and the other at 7:1, both exhibit the same problem (although the lower gain SUT is much better).  The cartridge is Ortofon A90 with .27 mv output.  Given this, would you expect clipping or do you think there is something wrong with the PH5?  I have talked to ARC about this issue, and they seem to think that there is a chance the PH5's maximum input of 70 mv is being reached on these loud sections.  Would appreciate opinions from those that have experience with a similar setup.  Thanks.
scottwsmith
Using a step up transformer of 1:20 will give you an output from the cartridge of 5.2mV, about the same as that of a MM cartridge.  The PH5 overloads at 70mV and typically if you allow for about 10x the input voltage for peak overloads, you have enough headroom.  I would not recommend using an input of over 7mV into it.  If you use a step up of 1:13, as you have described, the effective output from the SUT would be 3.5mV, less than if you used a MM cartridge.  So, something is not right here. 
So, it would seem there is something wrong with the PH5, in your opinion?
Are you sure it is the phono stage that is overloading?  Your Ref3 preamp has a specified maximum input level of 10 volts for its unbalanced inputs (which I presume you are using, since the phono stage provides only unbalanced outputs). 

The 57.5 db specified gain of the PH5 corresponds to a voltage multiplication of 750x.  Therefore: 

The preamp input that will occur when the cartridge is providing its rated output into the 7:1 SUT: 

0.27 mv x 7 x 750 = 1.42 volts

The preamp input that will occur when the cartridge is providing its rated output into the 13:1 SUT: 

0.27 mv x 13 x 750 = 2.63 volts

With respect to the Ref3's maximum rated input neither of those numbers allows for the cartridge to exceed its rated output by the factor of 10 that Bob suggested. 

Also, I note that the PH5's maximum rated output (50 volts) is far greater than the Ref3's maximum rated input (10 volts), which also reinforces the possibility that it is the Ref3 that is overloading.

On the other hand, though, if you have somehow determined that it is in fact the phono stage that is overloading, then as Bob said it would appear that something is wrong.

Good luck.  Regards,
-- Al
 
Thanks for the responses.  Perhaps my logic is faulty, but I suspect it is the PH-5 simply because the clipping disappears when I remove the SUT.  Without it, and with the REF 3 cranked up to a fairly high volume (about 2/3rds of maximum) there is sweet sound with no clipping.  Now, perhaps I am being paranoid, but I don't particularly like running the REF3 at that high a volume.  So I prefer to use the SUT. 
almarg, I see your point.  It could be the mismatch between the PH-5 and the REF 3 output/input.  Is there an easy solution if this is the case?
My suspicion is that the REF 3 design includes active circuitry that is "ahead" of the volume control in its internal signal path. If so, the fact that the volume can be cranked up to high levels without clipping when a SUT is not being used would still be consistent with the clipping occurring in the REF 3 rather than in the phono stage.

IMO there is no reason to be concerned about using the volume control at 2/3 max or other relatively high settings within its range. In fact that is considered by some to be generally preferable, as in some designs it might minimize whatever sonic side-effects may be introduced by the volume control mechanism itself.

So I would simply go without the SUTs. Keep in mind, of course, that without the SUTs the resistive load setting in the phono stage that is sonically optimal stands a good chance of being lower than the setting(s) you use with them.

Regards,
-- Al
Agree with Al 100%. As long as you can get it to play as loud as you want without excessive noise you are fine. It doesn't really matter where the volume control is. 2/3 of max is fine. You are not going to hurt anything. Generally speaking the more wide open the volume control the better it will sound' There is no need to be paranoid about the volume control. Lose the SUT.
So i have been happily listening without the SUT for several days, no clipping.  Been through several albums that used to clip, no problems now.  Given that this cartridge at .27 mv. is pretty typical MC output, and the PH5 at 57.5 dB is mid-range gain for a phono preamp (many have gain settings that exceed this), why would anyone use a SUT with modern equipment?  I know the SUT's historically have been used when you have a phono preamp which is designed for MM cartridges only.  But now, with so many phono preamps designed for MC and lower outputs, are they really necessary at all?  Does anyone perceive value in the use of a SUT when the gain of the phone preamps is such that it is really not necessary?  In other words, is the gain provided by the SUT "better gain" than the phono preamp's gain?  Or is gain just gain, regardless of its source?
All gains are of course not created equal, even if they are numerically equal. Noise performance and consequently hiss levels can certainly differ among different phono stages that provide similar amounts of gain, with that being likeliest to be an issue if an LOMC cartridge having particularly low output is used. Also, in some cases the sonics provided by the moving coil circuitry in phono stages having both MM and MC capability might not be as good as the sonics that would be provided by the combination of a good SUT and the MM section of the same phono stage.

Enjoy! Regards,
-- Al


Dear @scottwsmith : """   I know the SUT's historically have been used when you have a phono preamp which is designed for MM cartridges only. """

With all respect that statement is a misunderstood. In the old times active high gain phono stages designs were almost non-existent and almost all the phonolinepreamps were designed for LOMC cartridges using SUTs internally and the external SUT option were used with Phonolinepreamps or phono stages with no internal SUT.

A well designed today SS active high gain phono stage or phonolinepreamp performs with a higher quality that a phono stage with external SUT.

Normally all SUTs has " problems " at both frequencies range extremes. Has inherent limitations at low bass and high frequency against a well designed SS active high gain phono stage. 

Regards and enjoy the music,
R.








Post removed 
It seems to me that the ARC PH-5 is less flexible than some other phono stages, because it has fixed gain.  This might be more of an issue if the cartridge is MM has high output.  For example, if the cartridge's output is 4 mv, almarg's math gives me:

4 mv x 750 = 3 volts.

Only a 3X factor for headroom during loud passages, seems likely the 10 volt limit of the REF 3 would be reached often, and hello clipping!  Is my logic faulty, or this combination of components just a bad idea for MM cartridges with higher output?

So a PH-5 and REF 3 are really only good for LOMC?  Yipes. 
Yes, under most circumstances 57.5 db is considerably too much phono stage gain for use with a MM or other high output cartridge. Typically MM phono stages provide gain that is in the area of 40 db or so.

In addition to the possibility of clipping, another downside that can occur in many applications would be having to operate the volume control undesirably close to the bottom of its range. As you may have seen in other threads it is not uncommon for that problem to occur with digital sources having **maximum** outputs in the area of 2 volts.

That much gain would often be suitable, though, for use with MM cartridges in systems employing passive preamps, to cite one example.

In your particular case, given the very high overload margin of the phono stage itself a means of utilizing a high output cartridge without overloading the preamp would be to insert a Rothwell in-line attenuator, or something similar, between the two components. Although reports I have seen over the years on the sonic effects of those devices have been mixed, with some (including me) having found them to be quite transparent, and others reporting significant adverse effects on dynamics or other sonic characteristics.

Rothwell attenuators are available in both balanced and unbalanced configurations, and in 10 db, 15 db, and 20 db versions. I believe that most and probably all of those versions would be suitable with respect to ARC’s loading recommendations for the outputs of your phono stage (quoted below from www.arcdb.ws), and certainly with respect to the 10K minimum requirement. But I know that some similar devices from other manufacturers would not meet that requirement.
ARC PH5: Recommended load 50K-100K ohms and 100pF. (10K ohms minimum and 2000pF maximum.)
Regards,
-- Al

I am learning some good stuff here.  Switching gears a little, I also have an ARC DAC7 (which I use in balanced mode) with these analog specs:

OUTPUTS, ANALOG: (Stereo)1. Balanced XLR 5.2V RMS (+14.3dBv) max.2. Single-Ended RCA 2.6V RMS (+8.3dBv) max

And yes, I do operate the REF3 at rather low volumes (maybe 20%) when using the DAC.  Is there any possible benefit in using an attenuator?
In many designs low settings of the volume control may result in an inability to adjust volume in fine enough increments. I see that your REF3, however, provides 104 steps of volume adjustment, so I suspect that is not an issue in your case.

Also, in some designs channel imbalances can occur at low settings of the volume control. But again I would suspect that is not an issue with the REF3.

Finally, it is conceivable that in some designs having to operate the volume control at low settings may result in whatever sonic side-effects may be introduced by the volume control mechanism itself being worse than at higher settings. I have no knowledge, though, as to whether or not that possibility may have any applicability to the REF3. And even if it does, it would be anyone’s guess as to whether or not the possible sonic side-effects of an in-line attenuator, used with these particular components, would outweigh the possible benefit.

Best regards,
-- Al

almarg, I'd be interested in knowing if you have any favorites in the phono preamp category, care to comment?
Scott, yes, inspired by a great many overwhelmingly positive comments I've seen here and elsewhere, late last year I purchased a Herron VTPH-2 phono stage ($3650).  It is beautiful sounding, versatile, very intelligently engineered, absolutely quiet at any volume setting in my system in both LOMC and MM modes, and as many others have commented Keith Herron is a treasure to deal with.

It is offered in a choice of two gain configurations.  For the majority of applications, including mine, the lower gain version is preferable.  It provides gains of 43 db in MM mode and 64 db in MC mode.

The one slight caveat I would cite is that like your PH5 it does not provide balanced outputs, and John Atkinson's measurements of the REF3 indicate somewhat better measured performance in balanced mode than in unbalanced mode.  But even if those measured differences have any audible significance, which I doubt, I would suspect they are mainly attributable to JA having used the preamp's unbalanced outputs for the unbalanced measurements, not just the unbalanced inputs.  And I note the following statement in the body of the review:
ARC states that the long-tailed pair used in the Ref.3's input stage provides identical performance (save for the amount of gain) using either the balanced or the single-ended inputs.
Good luck.  Best regards,
-- Al
 
Yes I have noticed that one is recommended a lot.  Looks like a move from PH-5 to Herron could cost about $ 2K.  Will have to consider whether that is "reasonable" or not.  But for me, swapping gear and upgrading is part of the fun.  It seems that used versions of the Herron are hard to find.  I guess those who have them, keep them.  Did you purchase yours new?
Yes, I purchased my VTPH-2 new, directly from Keith after speaking with him on the phone. You would want to confirm with him that the lower gain version is the optimal choice for use with a 0.27 mv cartridge. I suspect that it will be, though, in part because he recommended that version for use with a 0.3 mv cartridge I was considering at the time. I ended up going with an Audio Technica AT-ART9, though, which is rated at 0.5 mv.

Best regards,
-- Al

This has two gain settings. Take a look, it just might fit the bill !
https://www.youtube.com/watch?v=RfpJYJv3ddo
I have had no luck with using a SUT with the ARC-5.  The gain of 57.5 is difficult to work with.  Almarg is correct.  However, if you look at the signal to noise ratios of active MC/MM phono stages, you will find that the signal to noise ratio using MM is higher than the signal to noise ratio using MC.  Additionally, increased distortion results from using the MC active stage.  That is why many manufacturers using SUTs in their phono preamps to accomodate MC cartridges.  The challenge is making different gain adjustments to accomodate different cartridges. ARC makes this easy by only offering one option and designing the phono preamp for only one gain setting.  It is great for a cartridge of about .5-.6 mV, but lower output cartridges don't work as well.
In the ARC world, you can move to the Reference product line, which does offer different gain levels, but they are pricey, I don't think I am too interested in that solution.   For those phono preamps that really do have an MM/MC switch -- I think you are saying using the MM setting with an SUT, instead of the MC setting might yield better results for a MC cartridge with output in the .25 range, such as mine.

For example, on the Manley Chinook, there is an internal setting to set the gain at around 45 dB, " for MM cartridges".  With my SUT's of 1:13 and 1:7 and that gain setting, what would be the input levels to the REF3, and given your suggestion of possible lower noise and distortion, is this a good upgrade?  Same set of questions for the Herron, if you would indulge me?? 
Hi Scott,

In the specific case of the Herron I would not expect using a SUT into its MM input to be preferable to going directly into its MC input. I say that in part because of the great results many have obtained using LOMC’s directly into the VTPH-2; in part because as I had mentioned I have found the VTPH-2 to be absolutely quiet at any volume setting (even when using my Stax electrostatic headphones, with the volume control at max); and in part because using a SUT into a 47K MM input will result in the cartridge seeing a much heavier load (i.e., a **much** lower number of ohms) than seems to usually be necessary with the Herron. (Keith recommends that with the VTPH-2 it is often preferable to apply no loading at all, with the input impedance of its LOMC input being almost infinite. And as Atmasphere and others have pointed out in past threads here, optimal loading of an LOMC is primarily dependent on the design of the phono stage, not on the cartridge).

To answer your question about gain, based on the relation db = 20 x logarithm(Vout/Vin) it can be calculated that for a 45 db gain setting of the Chinook the corresponding voltage multiplication is 178x, and the 43 db MM gain of the Herron corresponds to a voltage multiplication of 141x.

0.27 mv x 7 x 141 = 266 mv
0.27 mv x 13 x 141 = 495 mv

0.27 mv x 7 x 178 = 336 mv
0.27 mv x 13 x 178 = 625 mv

All of those alternatives would provide the 10x headroom factor Bob recommended, relative to the max input spec of the REF3.

Regards,
-- Al

Dear @bobsdevices  :   """  That is why many manufacturers using SUTs in their phono preamps to accomodate MC cartridges. """

Not really and not exactly as you posted. Yes, S/N is higher in MC active high gain devices than the same S/N figure in MM mode but this is just a number and if we know " to read " those numbers then it does not matters and does not goes against a SS active high gain designs.

The phono stages/phonolinepreamps that needs and use SUTs are the all tube designs because tubes are " noisy ".

AR, Herron and other tube designers instead of SUTs use SS devices at the input gain stage trying to lower noise and distortion levels.

The other designers that use SUTs are not because SUTs are better than SS active high gain designs ( that are not. ) but because is a lot more easy to design that " elussive " active high gain knowledge levels to do it.

A good SS active high gain design always beats to a design using SUTs.

What makes the real differences?: knowledge and skills level of the designers, nothing else.

In the other side here are 3 precise examples ( there are many more. Name of the game is in the design and implementation of that design. ) of SS active high gain designs where you can't detect that difference in S/N ratio between MC stage and MM one or even if the phono stage does not handle MM cartridges the S/N is so low in the MC stage that's imposible to detect any sign of noise or distortion levels:

http://www.stereophile.com/content/bmc-phono-mcci-phono-preamplifier-specifications#TWPUCjhcM5muLLb2...

http://www.stereophile.com/content/liberty-audio-b2b-1-phono-preamplifier#zP3dCRyDuo1Zyzoi.97

http://www.stereophile.com/content/parasound-halo-jc-3-phono-preamplifier-measurements#sEEGXPqsWEtwr...

As I said there are many other SS designs that are less affordable $$$  for almost any one.


Regards and enjoy the music,
R.


Dear @scottwsmith : I owned the A-90 that's one of the finest ( still ) today cartridge performers and I can tell you that for the cartridge can shows at its best  it needs a very good matching tonearm and the finest phono stage/phonolinepreamp we can get and with all respect your PH5 can't do it.

The gentlemans that posted in your thread are not a little " concerned " on the  A-90 cartridge needs and IMHO this must be the first " parameter/premise " to judge what to do.

Regards and enjoy the music,
R.
you can destroy phonostage by overloading it. input devices weather transistors or tubes are very easy to ruin by overloading.

the simplest solution is to use cartridge with sufficient enough output to use it without SUT.
many above had mentioned that.
using low-out cartridge just because it has great parameters, but requires extra gain, won't bring performance up.

I refuse to get into a pissing contest with a skunk.  Done here.
Dear @bobsdevices : Well, I understand feelings when some person has no facts in a discussion. I posted facts that goes per se against your opinion and that’s all.

Maybe you think that in audio SUTs are a perfect device and I think diferent: that in audio nothing is perfect not even near the perfection, all in audio has its own trade offs.

Regards and enjoy the music,
R.
Scott ...

" So a PH-5 and REF 3 are really only good for LOMC?  Yipes."

I've owned the ARC phono stages from the PH-5, PH-7, PH-7se and now the PH-8. I use a REF-3 preamp also.  

According to the techs at ARC, their phono stages, including your PH-5 are designed to operate best with a cartridge output of between .4 to .8 ... with .5 being the ideal. Get the cartridge right, and these phono stages really sing. 

 Instead of investing in a new preamp, why not take a look at a new cartridge?  The Audio Technica ART-9 is a wonderful cartridge and works perfectly with your preamp. The ART-9 has an output of .5. Its available from LP Tunes at the moment for $1197 with free shipping. Here's the link:

http://www.lptunes.com/Audio-technica-AT-ART9-MC-phono-cartridge-p/atart09.htm

The ART-9 is a true over achiever competing with cartridges in the 3-5k price range. Here's an entire thread on the ART-9:

https://forum.audiogon.com/discussions/audio-technica-at-art9-phono-cartridge

Hope this helps.

OP
Scott ...

Here's another thread on the AT ART-9:

https://forum.audiogon.com/discussions/pani-new-art-9-up-and-running
Oregonpapa, I agree with you. If I were the OP I would get a different cartridge. The Denon is a great price performer, but in most cases needs to be used with a SUT to perform at its best. Audio-Technica,  Shelter as well as others make cartridges with more compatible output.
Dear @oregonpapa : Did you listen in your system the Ortofon A-90 and then compared against the ART-9?

I did it vs ART 7 and 9 ( both from an audio friend. ) and even that the AT are very good performers IMHO the A-90 is better.

Now, if you did not listening yet the A-90 then make no sense to me your advise.

Anyway, the ball is in the OP field.

regards and enjoy the music,
R.
raul,
no matter how sooper-dooper-good Ortofon A-90 sings, the PH5 ain't enough. 
oregonpapa offers the most reasonable solution to preserve the best sound of whole system. 
forget about your little piece, it's too small no matter how good it is compared to the whole system synergy.

Dear @czarivey : I don't know @scottwsmith  thinking but if I own an Ortofon A-90 I will make my best effort for this little gem can shows at it best even if some one gave me the A-90 as a gift and if I can't because I don't know how to do it or have no money for make changes in my system then I will put the cartridge on sale for it can find out a better place to " sing ".


Regards and enjoy the music,
R.




Hi Scott!

The main reason for a SUT is to give the preamp enough voltage. It sounds like both are already too much, so technically you don't seem to require one.

If you just like the sound, to warm up what you hear, you may want to use a 1:1 isolation transformer.  Jensen makes some of the best. 

You could also build an L Pad attenuator. after the transformer. Even using the most expensive "naked" Vishay resistors you could do it under $50.

Best,

Erik
rauliruegas ...

With all due respect, I think we may have a language problem here. I wasn't commenting on whether the A90 is a better cartridge than the ART-9. My comments were directed at which cartridge is a better match for the ARC PH-5. True that I haven't heard the A-90 in my system. It may or may not be a superior cartridge, but if it doesn't work with the pre-amp,  what good is it? 

Take care ...

OP
Not particularly motivated to swap cartridges.  The A-90 is the best I have heard.  Was considering an upgrade in the ARC line to a reference series phone preamp.  any thoughts on that?  
And to follow up, my thinking now is NOT to use an external SUT.  I am getting good results with the PH-5, without it.  
Anybody have an opinion on the ARC Phono Reference Mark 1 that has just shown up on Audiogon?  Those gain numbers appear to be in the sweet spot for my A90 cartridge.