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Digital1955

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Darlington Labs MM-6 then upgraded to MP-7. This was an expensive experiment. ASR on the MM-6 didn't recommend it due to noise issues and the MP-7 didn't really improve on it. While the MP-7 did some things really well, like instrument separation in the sound stage, I just could't get past the high noise floor. Sold it.

"ASR on the MM-6 didn't recommend it due to noise issues" - where did you read this and what do you mean by noise issues?
 

deniall83

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"ASR on the MM-6 didn't recommend it due to noise issues" - where did you read this and what do you mean by noise issues?
Possibly meant the MM-5.

 

krichard2496

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Possibly meant the MM-5.

Most clients have significantly praised the nearly-silent background noise floor of our units, even with the typical highly-inductive Moving Magnet style cartridge -- where most BJT designs fall down significantly -- and this aspect is not tested in ASR's methodology.

Most other units -- whether discrete and therefore utilizing a single stand-alone BJT transistor or a pair -- or op-amp-based with an internal BJT differential pair -- result in a 'hissy' character to their noise floor (concentrated towards the upper octaves) with the majority of cartridges in use. Ours, rather, using a carefully-selected High-Voltage J-FET with nearly unmeasurable current noise, remains both very low in overall level, and quite flat in the residual noise spectra, more akin to the sound of high-speed open-reel tape with Dolby-A or SR noise reduction.

For further discussion, see (for example) “Noise of Sources”, National Semiconductor Application Note, John Maxwell, February 1977, or the even-more-math-intensive analysis of a Shure V15-III in National Semi’s application note AN-104 from May 1974.

Regarding low frequency noise, it has been our experience that careful dressing of the AC inlet cable, relative to the audio input cable, and proper positioning of the unit, reduces any residual hum that is induced by the physical installation to below audibility. Our noise specifications are intentionally very conservative, partially to account for variabilities in an individual installation. Of course, tastes in sound can differ, and overall system matching remains important in generating a satisfactory auditory result.
 
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Digital1955

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Most clients have significantly praised the nearly-silent background noise floor of our units, even with the typical highly-inductive Moving Magnet style cartridge -- where most BJT designs fall down significantly -- and this aspect is not tested in ASR's methodology. Most other units, when they are discrete, utilize a discrete BJT transistor on the input stage and this results in a 'hissy' character to the noise floor, biased towards the upper octaves. Ours, using a carefully selected High-Voltage J-FET with nearly unmeasurable current noise, remains both very low in level, and relatively flat in the residual noise spectra.

For further discussion, see (for example) “Noise of Sources”, National Semiconductor Application Note, John Maxwell, February 1977, or the even-more-math-intensive analysis of a Shure V15-III in National Semi’s application note AN-104 from May 1974.

Regarding low frequency noise, it has been our experience that careful dressing of the AC inlet cable, relative to the audio input cable, and proper positioning of the unit, reduces any residual hum that is induced by the physical installation to below audibility. Our noise specifications are intentionally very conservative, partially to account for variabilities in an individual installation. Of course, tastes in sound can differ, and overall system matching remains important in generating a satisfactory auditory result.

The original poster didn't come back and answer my question. But I think he was simply repeating that (the MM-5) SINAD was limited by "noise" (Amir's word).
Surely high frequency "hiss" would show up clearly in the FFT plot of the 1Khz test signal if it were there. In the MM-5 case, I think SINAD was limited solely by the the 2nd harmonic. I guess that is the "noise"?
 

krichard2496

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The original poster didn't come back and answer my question. But I think he was simply repeating that (the MM-5) SINAD was limited by "noise" (Amir's word).
Surely high frequency "hiss" would show up clearly in the FFT plot of the 1Khz test signal if it were there. In the MM-5 case, I think SINAD was limited solely by the the 2nd harmonic. I guess that is the "noise"?
Yes. Inaudible though the 2nd harmonic is believed to be, in the small proportion that it exists in our products due to the response of the human ear, it dominated his SINAD measurement which is "flat" and unweighted. We have requested that ASR provide a test output conforming to the D. L. Shorter / BBC Research Department proposed methodology of October 1949, with N^4 harmonic weighting, or any other similarly-supported acoustically-weighted real-world tailoring, seemingly with no response or interest.

We are reminded of that ASR thread regularly when listening to music on local FM broadcast, from what are very clearly needle-drops of original 1970s and 1980s LP pressings, and our earlier comments about how broadcasters can "see" tune-outs and audience interest on a cut-by-cut basis.

If you are using your phono preamp solely to amplify the output from a medical transducer or in a similar laboratory application, and looking at the result on a spectrum analyzer -- rather than listening to music on an audio system -- then perhaps a simple low-cost, high-feedback or differential design might be preferable to our units. Our understanding is that most EKG units generate primarily low-frequency output and so any TIM or slew-rate limiting on musical peaks and surface noise that would affect your music enjoyment won't even come into play.

Amir's test setup also appears to have induced a slight amount of LF mains noise into his input cabling which can be seen in the LF spectrum residual in the review. We addressed this in the sections above.
 
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Cwopete5

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Possibly meant the MM-5.

Yes, thank you for the correction.
 

valrak66

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Is a unit from 1974 going to be in spec? Maybe it would be fine if serviced, doubt it is as good as the Cambridge units.

The Cambridge Solo sounds, essentially, inaudibly different from the Duo. The ART DJ Pre II found to be slightly less impressive in the bass (has some phase issues going on from measurements) than the Solo.
I happened to record the same track through DJ Art and Cambridge Duo preamps. To my ears, if there is a difference, it's very subtle.
 

Digby

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To my ears, if there is a difference, it's very subtle.
I agree it is a mild difference - if one only has money for the DJ Pre II, they'll likely miss nothing. Do you find that the DJ Pre II sounds different depending on where you set the input knob - this was something I thought I perceived, but couldn't be sure. Also, the different settings (Hi-pass) seemed to sound vaguely different from each other. What do you think?

Personally, I think the Solo is best of the three and the extra money one would spend on a Duo can be spent on a better cartridge instead, presuming you only need MM loading.
 
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mike70

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Well, is a basic cartridge with a conical stylus, maybe something more refined shows a bigger difference. Generally, a good elliptical like Ortofon Blue or Audio Technica vm95en sounds better.
 

rongon

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I don't think a schematic of the RIAA preamp circuit in the Kenwood receiver was ever posted, so who knows what the answer is to the OP's question.

The Audio Technica cartridges mentioned are moving magnet types, so will be affected by any capacitance load presented by tonearm cable and preamplifier input stage. The optimal loading will be dictated by the output impedance of the MM coil and its inductance, with the added capacitance from tonearm and interconnect cabling. The AT carts are made in such a way that they should not be loaded with any more than 250pF total parallel capacitance. Keep in mind that the tonearm wiring may have 30pF capacitance, and the interconnect cable 100pF to 150pF (sometimes more). That leaves only about 100pF maximum input capacitance allowed from the RIAA preamp. An FET input discrete RIAA preamp may have higher input capacitance than this. A 12AX7 based tube RIAA preamp is practically guaranteed to have input capacitance of >150pF, which will cause a resonant peak centered around 8kHz in the cartridge's electrical output. This can be perceived as overly aggressive sounding upper-mid and/or treble response and/or exaggerated surface noise. Opamp based RIAA preamps will have extremely low input capacitance, which is a good thing in the case of these AT MM cartridges.

However, some opamp-based RIAA preamp designs have additional parallel capacitance added for 'tuning'. If this additional capacitive 'loading' can't be defeated, then that could be a downside for these AT MM cartridges that work best into a low capacitance load of 100pF to 200pF total.
 

mhardy6647

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I don't think a schematic of the RIAA preamp circuit in the Kenwood receiver was ever posted, so who knows what the answer is to the OP's question.
KR-5400 schematic available from hifiengine (although at the moment their d/l function is down, so I can't vouch for how legible it is).


Apropos of almost nothing: years back, I had a KR-4200 for a while. It was on the average side of unremarkable. ;)

1666043860201.jpeg


EDIT: in fairness... the KR-5200 was one model further up the lab.

1666044285245.png

source: https://worldradiohistory.com/Archive-Catalogs/Consumer/Burstein-Applebee-1973.pdf
 
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Timcognito

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Amir tested this one, with lots of setting options, and liked it. For $81 you buy it, and compare it to that Kenwood then use the better one knowing that its good. Bet it beats the Kenwood.
 

rongon

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KR-5400 schematic available from hifiengine (although at the moment their d/l function is down, so I can't vouch for how legible it is).


Maybe you can access this?

I've attached the RIAA section of the KR-5200 schematic.
It looks like it's a classic two BJT negative feedback RIAA. (And why not?) At least the input capacitance should be fairly low (using BJTs, not JFETs).
It looks quite basic.
Instead of the usual 47k load resistor (input BJT base to ground) there's a resistive voltage divider of 2.2k series, 82k to ground. Then a capacitance-resistance filter (high-pass) to the input transistor's base.
 

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skhan007

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Great thread and I'm also interested in buying my first phono stage. Based on what I'm reading on ASR and other sources:

ifi Zen- Sounds like a great option and a great price-point.

Cambridge Duo- I have zero need headphone amp or MC features, but the specs and reviews state it's markedly better than the Cambridge Solo.

Parasound Zphone- Great brand, but I've heard there's WAY TOO MUCH gain coming out of this unit and don't want to overload my tube amp, which I understand might be likely.
 

rongon

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I just read the ASR review/measurements of the Parasound Zphono.

It seems it is pretty much as good as it could possibly be except for a slightly higher noise floor than some other competing phono preamps. However, its SINAD suffered because of 75dB SNR. As Amir pointed out, that puts it in the middle of the pack regarding SINAD. However, is SINAD the one and only most important determinant of an RIAA stage's quality?

What about distortion? In that regard, the Zphono is very good. 0.017% THD at an output of 1.1V rms is quite good enough.

In my opinion, the overload behavior and headroom of an RIAA stage are extremely important. If the RIAA stage overloads on every tick and pop, it will exaggerate those noises and 'sound bad'. That would not be good. In this regard, the Zphono looks good too. Amir found the headroom to be better than other budget preamps, and it is not frequency dependent. It didn't approach overload until 44mV rms input at 1kHz (with 47dB gain that would be 8.8V rms out, which is pretty impressive!). That means the THD will be low in all normal usage situations, including hitting most clicks and pops. I rate that as a very good thing.

Finally, there's this question of gain. I like my music sources to all play at a similar enough volume level that I don't have to adjust the volume control when I change sources from LP to digital to TV, etc. The 'standard' max output level for digital sources is 2V rms signal output at 0dBFS (full scale). That's actually quite 'hot' compared to vintage analog sources like FM tuners and older RIAA preamps.

I've found that if I'm using a typical 'hi-fi' (not DJ) moving magnet (MM) cartridge like the Audio Technica AT-VM95ML with about 3.5mV nominal output, it takes about 42 to 45dB of gain to bring the volume level from LP up to about the same level as from either of my two DACs or my CD player (all rated at about 2V rms out at 0dBFS). If I use an RIAA stage with 35dB gain, I find myself turning the volume control up almost a quarter-turn to get LP playback up to the same level as digital source playback. It's a minor concern for many, but I don't like being forced to fiddle with controls all the time.

The Zphono's gain at 1kHz is shown to be 47dB. That is on the high side, but if you're using a cartridge with fairly low output, like a Denon DL110 (2.5mV), a Grado (4mV), or some Audio Technica MM cartridges (3.5mV), that extra gain will be welcome. If you use a DJ cartridge like the Shure M44X then it will probably not work well at all (too much gain).

Will gain of 47dB from your RIAA preamp overload your amplifier's input? Well, that depends on how your system is configured. Do you use a line preamp with gain? What is the input sensitivity of your amplifier? Does your system overload from digital sources now? Remember that after the RIAA stage comes the input selector and volume control (usually a resistive voltage divider). If you need to reduce the signal level from the RIAA stage you turn down the volume control. If the system isn't already prone to overload, I don't see how a 'hotter' signal from the RIAA stage would cause it to overload.

The iFi Zen has 36.5dB of gain at 1kHz, which is a whopping 10dB less than the Zphono. You will hear that difference. You will need to turn the volume control up quite a bit to match levels between LP and digital sources. Will that matter in your system? Even though the iFi Zen has very low power supply noise, its SINAD comes out 8 dB worse than the Zphono's, in part due to its low gain.

Also in the iFi Zen review, you can see that its THD rises and headroom decreases with increasing frequency. I wonder if this means its overload behavior from clicks and pops will be noticeably worse than from other preamps with more headroom up there.

The Cambridge Duo measures best, but its gain is 39dB at 1kHz. That's probably a good compromise but still on the low side for me. It also looks like the Cambridge Duo has good headroom. Amir states that he didn't see THD spike upwards until the preamp was putting out 6V rms. That's quite good for a solid state preamp, although many tube preamps can swing more volts than this (they work at high B+ voltages, so that's their strong suit). However, unless I'm reading Amir's measurements wrong, it looks like the Zphono has significantly higher headroom than the Cambridge Duo. Am I figuring that wrong?
 

Sputnik

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The Parks Puffin is a very interesting phono pre, it has the most accurate RIAA eq of all the pre's tested, and it filters cracks and pops better than any other. Those 2 things will make for more audible improvement than any analog phono pre.

I wouldn't worry too much about sinad, any one on Amirs recommended list will be fine. I'm quite happy with my Ifi Zen, I sometimes think about getting the Puffin, but I don't play records enough to justify the cost.
 

Bob from Florida

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The iFi Zen has 36.5dB of gain at 1kHz, which is a whopping 10dB less than the Zphono. You will hear that difference. You will need to turn the volume control up quite a bit to match levels between LP and digital sources. Will that matter in your system? Even though the iFi Zen has very low power supply noise, its SINAD comes out 8 dB worse than the Zphono's, in part due to its low gain.

Also in the iFi Zen review, you can see that its THD rises and headroom decreases with increasing frequency. I wonder if this means its overload behavior from clicks and pops will be noticeably worse than from other preamps with more headroom up there.
The Zen switch 1 and 2 are both 47K load with 36 and 48 db respectively. Positions 3 and 4 are 60 db @ 1000 ohms and 72 db @ 130 ohms. These are unbalanced gains. If you use the balanced outputs, add 6 db gain to each setting.
I have not noticed any bad pops or clips in my system. I am using a Hana SL at switch setting 3 utilizing balanced outputs.
Use switch position 1 or 2 for your moving magnet cartridges and if more gain is needed use the balanced outputs if your line stage supports it.
 

rongon

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I'd submit that ultimate RIAA EQ accuracy is not the most important characteristic of a phono preamp. Nobody is going to notice errors of +/-0.5dB is they're not super-abrupt in slope or form a very wide shelf. Even then I don't know if a 0.5dB shelf or spike can really destroy anyone's enjoyment of records. I mean, the whole LP playback system has resonances, the cartridge has its own frequency response anomalies, etc. But channel-to-channel matching of the EQ is likely to be very important. And of course overload characteristics (you don't want every little tick or pop to explode into a jarring crack).

So yes, I agree. Pick any one of the <$500 RIAA preamps on Amir's recommended list and I'm sure it will work fine. If you know you value a particular characteristic then choose the preamp that most closely matches your desired characteristics. I prefer gain around 45dB at 1kHz and graceful overload behavior, and I can tolerate a bit of hiss. You might prefer super low noise and super-accurate RIAA adherence over that. It really all depends. The thing to do is know what it is that you value, and go from there.

Good luck!
 

rongon

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The Zen switch 1 and 2 are both 47K load with 36 and 48 db respectively. Positions 3 and 4 are 60 db @ 1000 ohms and 72 db @ 130 ohms. These are unbalanced gains. If you use the balanced outputs, add 6 db gain to each setting.
I have not noticed any bad pops or clips in my system. I am using a Hana SL at switch setting 3 utilizing balanced outputs.
Use switch position 1 or 2 for your moving magnet cartridges and if more gain is needed use the balanced outputs if your line stage supports it.

Ah, I missed that the gains are adjustable. Thanks.
That's pretty smart, actually (Thorsten's a smart dude).
A 1000 ohm load with 60dB of gain is aimed right at the DL103 crowd. :)
 
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