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Follow Up: Puffin Phono DSP Preamp

SIY

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1591040146903.png

Image shamelessly stolen from Amir



@JPJ kindly sent me his Puffin stage for some further measurements following the brief review by Amir. After an unconscionable delay, here we go.


First, the basics. First, I flashed the ROM with the latest firmware version (1.20), which got rid of some of the anomalies I'd seen in earlier measurements. This is done via a USB cable to a module on the circuit board. I set the gain to 40dB (since that's right for most MMs I have on hand), load to 47k (ditto). Input capacitance measured slightly over the 50pF spec, which is suitable, accounting for typical cable capacitances, for MMs like the Audio Technica I use. For other cartridges, either use higher capacitance cables or make use of the extensive EQ functions built into this unit.

Gain measured 40.1 dB, almost exactly as advertised.

Note that I used a 100:1 attenuator at the input to allow the generator to run closer to its sweet spot and to feed the unit from a 1k source resistance. So any place you see a Generator Voltage, divide it by 100. There’s probably a way to do this in the APx software, but I was too lazy to figure it out. Next time. The “A” reference in the graphs (as in “dBRA”) is the output with 5mV in at 1kHz (500 mV).

First up, the noise spectrum, generated with a Stanton 881 as the source:

1591040219274.png

As expected, it roughly corresponds to the RIAA curve. The 60Hz spike might be something I could get rid of with some fiddling with grounding, so don’t worry about it too much.

Next, RIAA conformance:
1591040255879.png


Note the expanded scale- the channel to channel match is superb, and the overall deviation above the bass region is less than 0.5dB. The low cut filter was off, so the 2dB bass rolloff at 20 Hz is a bit odd.

With 5mV in, the 1kHz distortion spectrum looks like this:
1591040297885.png


Nice and low, much better than any cartridge will give you. Now although I limited the measurements because of the literally hundreds of setting options on this unit, curiosity got the best of me, and I repeated this measurement with the “Tube FX” on (I displaced the frequencies slightly for better visibility of the changes):
1591040330061.png


Not my cup of tea, and if I built a tube stage that bad, I’d probably slit my wrists in anguish.

Overload was measured at four frequencies (and remember that the generator voltage needs to be divided by 100):

1591040367636.png


That’s not inspiring performance. I’d want to see things an order of magnitude better, but I’m spoiled by my current gear…

THD+N versus frequency at 5mV/1kHz and RIAA pre-equalized:

1591040412187.png


This appears to be noise-dominated, and again, lower than any actual cartridge could provide..

Impulse response gives a nice insight into how the digital processing works:

1591040475966.png


Finally, a pre-equalized multitone:

1591040506925.png



All in all, other than the mediocre overload performance, this seems like a very well-engineered unit for the money. The feature set can be overwhelming, and is probably worthy of an entire article rather than this brief measurement suite.
 

BDWoody

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Thanks for the review. Always appreciate seeing them.

@watchnerd is playing around with one, and has a thread going...trying to see what it can do without an SUT for his very low output cartridge.
Don't know if you'd have any insight on that as he messes around with it.
 

LTig

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[..] and I repeated this measurement with the “Tube FX” on (I displaced the frequencies slightly for better visibility of the changes):
View attachment 66656

Not my cup of tea, and if I built a tube stage that bad, I’d probably slit my wrists in anguish.
It's probably necessary to add that much distortion, to make it audible. Lower level distortion components might be swamped by those of real world records.
 
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SIY

SIY

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It's probably necessary to add that much distortion, to make it audible. Lower level distortion components might be swamped by those of real world records.
The interesting thing as well is the rather large amount of higher order distortion, mostly odd-order.
 

DDF

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The overload limit actually doesn't look too bad.

Not allot of info is out there on phono overload limits so I went and calculated it for my system. This data can be used for any phono, and since its so hard to find, thought I'd share it along (unfortunately the forum won't let me attach the excel file).

I'm using a phono pre-amp into an A/D with USB out into the PC. The PC then supports EAPO/DIRAC/favorite speaker+room EQ. The gain into the A/D needs to be kept in check, but it works and gives almost infinte eq flexibility.

The spreadsheet calculates maximum cartridge output, phono pre output and A/D input. It then back calculates the highest LP groove modulation the set up supports.

I'm lacking "a wee bit" of headroom right now, though it passes Shure's test record criteria:

1591059932866.png


Backup info: maximum groove velocities
http://www.pspatialaudio.com/max_velo.htm
From a Shure study: "The data confirm maximum velocity almost never exceeds 50cm/s, and that these maximum values do appear around 8kHz just as the theory predicts"
1591060112883.png

"Thus we can say, the maximum recorded velocity on a 33⅓ RPM LP will never exceed 50cm/s, and even this figure is only achievable on the outermost groove. We can apply this rule to other media too. Thus, a 12" 45 single can support a maximum recorded velocity of 68cm/s (although measurements frequently indicate that recorded levels on 12" singles are no greater than from LPs*). "

https://pubs.shure.com/guide/C-PEK-2/en-US
"A stereo pickup in good condition should be able to track Band 10 or 14 cm/sec at the median recommended force"
 
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watchnerd

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Thanks for the review. Always appreciate seeing them.

@watchnerd is playing around with one, and has a thread going...trying to see what it can do without an SUT for his very low output cartridge.
Don't know if you'd have any insight on that as he messes around with it.

For those on this thread:

I'm using it with a non-magnetic core Audio Technica ART-7:

Output: 0.12mV

I have it set to 68 dB gain (only one notch below max of 72 dB), 200 ohm resistance.

From there, the line-out goes into the Devialet, where I adjusted the input voltage down to 1.0V.

If I crank the master volume on the Devailet up to 0 dB with no music, there is some hiss and other cyclical funky noise that is audible if put my ears to the cones or touch them to feel it. Of course, this could be inside the Devialet.
 
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SIY

SIY

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Re: overloads, the issue isn't just recorded velocities, but also ticks and pops. Morgan Jones did some measurements to look at actual cartridge outputs, and he saw much bigger peaks from vinyl defects than from any signals. Now, if recovery from overload is essentially instantaneous, then no harm, no foul. But I'd rather have the headroom.

Re: clipping, look at the dominant second harmonic...
 

watchnerd

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Re: overloads, the issue isn't just recorded velocities, but also ticks and pops. Morgan Jones did some measurements to look at actual cartridge outputs, and he saw much bigger peaks from vinyl defects than from any signals. Now, if recovery from overload is essentially instantaneous, then no harm, no foul. But I'd rather have the headroom.

Re: clipping, look at the dominant second harmonic...

Speaking of pops and ticks, did you have you tried the 'Magic' feature of the Puffin that is supposed to mitigate them?

http://parksaudiollc.com/magic.jpg
 
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SIY

SIY

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watchnerd

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It looks intriguing. Unfortunately, I couldn’t do any listening because this preamp isn’t compatible with my phono system.

Does it show up on your menu?

It's not on mine, presumably because I didn't update the firmware.
 
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SIY

SIY

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Yes, it does.

Updating firmware is easy and fast. Just sayin’.
 

Joachim Herbert

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Too bad this does not come with USB output. Would be a perfect tool to digitize records. I am aware of the spdif option, but that spdif>usb conversion.
 
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SIY

SIY

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Too bad this does not come with USB output. Would be a perfect tool to digitize records. I am aware of the spdif option, but that spdif>usb conversion.
Of course, if you’re digitizing records, all you really need is an ADC, like a Scarlett 2i2. RIAA can then be done in the playback program.
 

Joachim Herbert

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Of course, if you’re digitizing records, all you really need is an ADC, like a Scarlett 2i2. RIAA can then be done in the playback program.

Got a Babyface pro fs plus software, but would love a more integrated solution.
 

watchnerd

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Of course, if you’re digitizing records, all you really need is an ADC, like a Scarlett 2i2. RIAA can then be done in the playback program.

I have an RME ADI-2 pro, but it's in my office mixing studio, not where my turntable is.

I could run the SPDIF into my Devialet and take the USB out of that, which is fine for small experiments, but, again, more complicated than I'd wish.
 
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