The importance of a Phono Pre-Amp

So Gents,

I only have been in the Vinyl Hobby seriously for the past couple of years. I got myself a Clear Audio Concept to begin with, and at first used the Phono Pre-Amp inside of the Roksan K3 Integrated amplifier, and it sounded weak and lacking in any real weight. I upgraded and got an external Pro-Ject MM Phono Pre-AMP. Unfortunately it sounded worse!

So after much searching I read that the Rega Fono MM MK3 was a good starting kit, so went for that and was immediately impressed, and have been right up until now. The sound was much better than the prior options and the overall presentation was far better.

Fast forward to this week, I took delivery of the MyTek Brooklyn Bridge. Which has it's own MC / MM Phono Stage.. crikey I am absolutely flabbergasted at the difference. I am not sure what is making it sound so different but the overall presentation is far more articulate and clear, and the bite of the high-end is far more perceivable.

Since I am relatively new to this, what are the determining factors in a good phono pre-amp? I need to understand why one is better than the other.. I am relatively happy for now. But when the upgrade bug bites again in a couple of years time, I'd like to understand what I need to look out for.

 

What makes for a good phono preamp -- RIAA circuit accuracy; sufficient and appropriate options for gain, resistance loading and capacitance loading to suit whatever cartridges you want to pair it with (a lot of what you are going to hear that makes one phono preamp sound different from another relates to these parameters, and how they suit the particular output level, impedance and inductance of each different phono cartrdige); low noise.

Beyond that people will tell you about potential subjective sonic differences in tone character that may (or may not) result from certain kinds of circuit differences, you probably won't find any consensus on these things, just as many different opinions as there are audiophiles and circuit designers. These things include the different types of capacitors and resistors used in the signal path; the speed of the amplification devices used; the tonal character of the amplification devices used -- op amps vs. discrete transistors vs. tubes; the type of RIAA circuit used (fully passive, fully active, split); etc.

I don't know what cartridge you got with your Concept turntable, but proper mating of cart to pre (sufficient gain for the cart's output, appropriate resistance and capacitance setting), not just the sound character of the pre itself, will play a large role in what you hear.

 

What he said. Hope you have a lot of time to devote to meticulously examining each aspect what contributes to the overall sound. Isn't vinyl great.

I am slightly kidding. Slightly. It's kind of cool to start changing up different things and seeing what happens. Until it is a beating and you are never ever satisfied because you have found something else you want to swap out or tweak. Then you have spent a lot of money and have a bunch of stuff lying around not being used LOL. Or maybe you hit everything right the first time around and never change a thing and are happy with what you have. Yeah right.

 

Every piece of audio equipment is important. And, system synergy plays a role too. Tricky business to say the least.

 

Amazing the difference that can be heard with a simple circuit that does the same thing as another. Once heard, cannot go backward!

 

Ears are by far most sensitive sense. An example I read was if eyes were as sensitive as ears, you could see a 60 watt bulb 2500 miles away in outer space (no interfering atmosphere).

 

I needed a new phono pre, so I just ordered the Art Pro II.
Read all the review good and bad, this one seems to come up pretty good in the scheme of things.
It was about 54 dollars US including delivery.
Only wanted a 'cheapie'.

 

What unit do you recommend that can handle most types of MM carts?
Wanting to try more carts in the future.

 

It depends on how these things are measured. At the eye/ear limit of sensitivity you need to allow adaption time. If you were to sit in an anechoic chamber completely isolated from outside sounds for an hour, and compare that to the threshold for pain, the ear's dynamic range is about 13 orders of magnitude. Similarly, allowing the eye to dark adapt and comparing that to a camera flashlight, the eye dynamic range is about 12 orders of magnitude. So in principle the total range is about ten times higher in the ear than the eye.

However that is not really a meaningful comparison, because of a kind of automatic gain control. In a typical environment, both the ear and the eye can deal with about five orders of magnitude.

So could the dark adapted eye see a 60W light bulb at 2,500 miles (4,000 km)? Without going into the maths (I'm a Brit, so we add an s. We don't just do one math, we do lots of them), the answer is no. The limit of visibility for a star is magnitude 6.5, which is 8.5 x 10^-11 Watts per square metre. The 60W light bulb will convert 2.2% of the input power into visible light, and it works out that it produces 6.6 x 10^15 Watts per square metre, and is therefore 13,000 times too dim to see.

Could you *hear* that intensity? Well the threshold of hearing for a quiet-adapted ear is about 10^-12 Watts per square metre, so you could not hear it either - it would be 150 times below the quietest sounds you could hear.

But is the ear more sensitive than the eye? Yes, the ear is 8.5 x 10^11/10^12 = 85 times more sensitive than the eye.

 

A few factors:

-Does it meet my budget?

-Does it match well with my cartridge (loading capacitance + resistance + gain)?

-Does it have an appropriate overload margin for my cartridge?

-Is it sensitive to RFI/EMI?

-Will it work well with my existing equipment?

-Is the amount of noise it creates below my threshold of tolerance?

-Does it accentuate surface noise, clicks, pops, etc.?

-Is the RIAA EQ accurate enough? If I need archival EQ options, are they included?

-If I really need a subsonic filter does it include one? (Note that one can always be added later separately at additional cost).

-If I really need a mono switch does it include one? (Note that one can always be added later separately at additional cost).

-Do I have the ability somehow to audition the equipment or use a return window to try it out in my home with my system?

 

Your original amp phono gain was likely around 35db. The Rega is near 42. What is the gain on this latest piece?

 

Around 56dB from Stereophile ...

When I set the analog input to MM Phono, the input impedance was close to 47k ohms across the audioband, the output was still inverted, and the gain at 1kHz was now 55.6dB—on the high side for moving-magnet cartridges. Even so, the overload margin was very good, at 16.5dB at low and middle frequencies, dropping slightly to 13.6dB at 20kHz; the wideband, unweighted signal/noise ratio was also excellent, at 72.5dB ref. 1kHz at 5mV.

I then set the input to MC Phono: the gain at 1kHz increased to 72.6dB, the input impedance dropped to 990 ohms, and the overload margin was close to 20dB across the audioband. The unweighted S/N ratio (ref. 1kHz at 500µV) was now 58.6dB, which is still good, especially when you consider the very high gain and the presence of much digital circuitry in close proximity.

 

That about covers it.

What I bet the OP is really noticing is the increased gain.

 

That is a BOATLOAD of gain. My original point was that someone might confuse louder with better, that is why SPL matching is so important when comparing gear.

But I just cannot get over that amount of gain for a MM input, holy smokes!

At what point do we worry about overloading the input on a preamp? Or is this intended as a preamp replacement?

 

I'm not qualified to make specific recommendations. I haven't heard what's out there to be able to tell anyone what specific unit to buy, just what features to look for. If you want to handle most types of MM carts in the future, you aren't going to need much in the way of features -- most MM carts are loaded at 47kOhms and most MM phono stages have a provision for that. You might want a phono stage with adjustable levels of gain to cover MMs which might have 3 mV outputs or 6 mV outputs so maybe adjustable gain from like 35 dB to 46 dB, or maybe fixed gain in that range will be OK. And adjustable capacitance, or at least sufficiently low input capacitance to control any problems with RF at the input but to allow you wind up with the total capacitance load recommended by the cart manufacturer (likely to be in the 150-300 total pF range, total meaning phono stage input plus cable capacitance). If you have 100-150 pF of capacitance in your phono cable and plugs (not atypical, if you 3-foot cables of 33 pF/ft capacitance), you'll need no more than 100-150 pF of capacitance at the phono input to be able to make the capacitance load conform to recommendations, and the lower the input capacitance is the more leeway you'll have.

 

In terms of the Art Pro II, has anybody made any mod's to the ridiculous LED?
Thinking of trying to add a resistor to it to minimize it's brightness.....
Has anybody tried adding a power On/Off switch?

 

Your experience doesn't surprise me. I used a Brooklyn as a pre-amp and phono-pre with a Denon 103 and really liked the sound. Thought it was great and could see myself doing that again in the future. I currently have a Fono MM like you had and also think it's pretty good with the Exact I'm running. I would imagine there's a lot of synergy that happens between a cartridge and a phono pre, in tonality and technical compatibility, but I haven't been through enough carts/phono stages to understand the magic formula.

 

A lot of people just put black electrical tape over it.

 

Brooklyn Bridge

From the pics looks like a preamp replacement meant to be hooked directly to a power amp...

 

An odd factoid addendum to that earlier post. Deep space spacecraft, such as the NASA New Horizons probe that sent stunning pictures of Pluto last year communicates using microwaves generated by a TWT (Travelling Wave Tube). That generates 60W of S-band microwaves which carry the image and scientific data. And we pick that up from 4.7 billion miles away.

Now of course the spacecraft has a high gain antenna dish pointed right at Earth. An on Earth we have very large radio dishes with exceptionally sensitive detectors.

But nevertheless it is a staggering thing to consider, that we can detect these exceptionally faint radio signals here on earth - from a 60W transmitter 4.7 billion miles away.

 

Just imagine how much better those images would be, with an upgraded cable or two.

 

Ive been listening to phono stages at home recently -- very easy to hear differences!

With my RP-8/Apheta2, I've been using the Rega Aria. It gets good reviews. I bought a used Naim Superline (new its about 2x the price of the Aria), and it was as if the proverbial veil was lifted.

A local forum friend was kind enough this past weekend to let me borrow his Rega Aura, a $6000 phono stage. It was a bit more revealing than the Superline, but while I preferred it slightly my wife thought it was too 'in your face' and preferred the Superline.

So yeah...these little boxes are quite important to the overall sound of your vinyl playback!

 

They make a standard and a low gain ("E") version of the Naim Superline, do you know which one you have?

 

I'm pretty sure mine is the standard version. It seems pretty happy with the Apheta2 output, and I use the settings Rega recommend; 1000 pF and 100 ohms.

 

Yeah, seems the simple logical thing to do...
It just looks, err 'tacky' (pun intended)
The thing could light up a stadium.