Piezo blindtest..

[Claus H]

I have designed and build a Piezo DI, to match some Hansen Powerbridge equipped tele's unfortunately we have had a lot of problems with the powerbridge, and the artist we build this for had a another guy build his take on a piezo preamp into them, I had a chance to test drive them with my piezo DI and with his preamp..

Tell me what you think!

http://www.pedalsite.dk/media/Piezotest.mp3

Recordet DI to Reaper same low cut filter on bouth plus a little ambiance..

[SJE]

I have designed and build a Piezo DI, to match some Hansen Powerbridge equipped tele's unfortunately we have had a lot of problems with the powerbridge, and the artist we build this for had a another guy build his take on a piezo preamp into them, I had a chance to test drive them with my piezo DI and with his preamp..

Tell me what you think!

http://www.pedalsite.dk/media/Piezotest.mp3

Recordet DI to Reaper same low cut filter on bouth plus a little ambiance..

It might be an idea to explain what the 2 clips in the MP3 are! I just heard 2 similar Piezo sounding clips . . but I have no idea which is what!

[Claus H]

What you can't hear a difference? To my ears they are radical different?
I would not be a blind test if you knew what was what, One is a simple FET preamp, other is the DI I designed.
Witch one do people like!

[SJE]

One is a simple FET preamp, other is the DI I designed.

So why didn't you say that in the first place!? I know it's a blind test but your initial post didn't exactly make it clear what the 2 clips were of.

I preferred the 2nd from first listen. The 1st sounds a bit nasally and the 2nd is generally brighter and crisper sounding.

[Chadheckler1]

So why didn't you say that in the first place!? I know it's a blind test but your initial post didn't exactly make it clear what the 2 clips were of.

I preferred the 2nd from first listen. The 1st sounds a bit nasally and the 2nd is generally brighter and crisper sounding.

Personally I hear the opposite... I liked the first one better. Sounds more real to me with better defined highs and a more full low end. But I am listening to it on my laptop though so that could be a factor.

[David Schwab]

So why didn't you say that in the first place!? I know it's a blind test but your initial post didn't exactly make it clear what the 2 clips were of.

If he told which was which, it wouldn't be a blind test.

He did say:

another guy build his take on a piezo preamp into them, I had a chance to test drive them with my piezo DI and with his preamp..

I think they are similar in tone, that is they sound like a piezo bridge, but the EQ is different. The first clip is thinner with more upper mids, and less low end, and the second clip is softer sounding with more lows and less mids.

If the attempt is to simulate an acoustic instrument, then the second clip might be closer, though I also like the crispness of the first clip better, but it needs EQ. I also like the attack better on the first clip, as the softness of the second clip sounds dull in comparison. But it does make it sound less like a solid body with a piezo.

Does the second one have vacuum tubes? It has that kind of vacuum tube mushiness.

Apples and oranges.

[cbarrow7625]

I listened through a pair of decent headphones. The first clip sounds full & mid-rangey but lacks top end crispness and pick attack.

The second clip sounds more like an acoustic guitar; a less artificially accentuated bottom end and better top end attack than the first clip. The midrange on this clip is more laid back than on the first clip, lending to a more natural acoustic sound but, on the down side, it sounds to me like the mid range may be pulled back too far. It does not sound like it would cut through a live mix the way it would need to, the midrange is too subdued, there is not enough "body" or "presence". It is not that far off though but enough that I would not be happy playing through it personally.

Overall, I think the second clip has a better chance of sounding more acoustic-accurate with some modification to the equalization (if that is even the goal with this preamp, I don't know but assume it is).

Without modification to either preamp, I would actually want to use (buy) the first one at this point because it would be easier for me to EQ it the way I want with basic equipment. A little bass roll off, bring the mids down little and bring up the top end a bit and I think I would have it. On the second one I would feel the need to boost the mids, and I know that is not going to sound good with most gear.

[David Schwab]

Hearing can be very subjective. The first clip actually has almost no low end information in it under about 70k Hz.

The second one has a lot more bass. I'm listening with a pair of Sennheiser 'phones attached to a Behringer Eurorack MX 1604A being fed from my M-Audio Audiophile 2496 sound card. The EQ on the board is flat.

The first clip seems brighter, but the reduced mids in the second clip lets you hear the top end more, along with the bass boost, which gives a larger tone.

The way to really here the difference is side-by-side, not one after the other. So I took the MP3 file and saved it as an AIFF file, and then imported it into TC Works SparkXL, which is a stereo audio editor. Then I took the first strum from each test, and copy and pasted them next to each other, and then repeated that twice. Then on the second half of the comparison, I applied a low pass filter to remove all high end above 75 Hz.

So here is the first strum of each, looped, and then run through a low pass filter to remove everything over 75 Hz, and then normalized to be the same level as the unfiltered clip.

Also you can see in the waveform (first picture below) that the second test clip is much louder when the highs are removed. That shows it has more information under 75 Hz.

Piezo test/low pass

So clearly the second clip has a lot more bass frequencies.

The first clip might be lacking low end because the input impedance of the preamp was be too low, or it had too small a coupling cap. That tends to make piezos thin and scratchy sounding. And they always need some EQ to sound natural, IMO.

Now as far as the highs, here's the same two strums run though a high pass filter to remove all audio under 8k Hz. You can hear that the first clip has a bit more upper extension going on, and once again, the waveforms (second picture) show its louder on the attacks. But they are very close.

Piezo test- high pass

So that shows that the first clip has a lot less low end, while the second clip has much more low end and less upper mids. The highs are almost the same, but the peak on the first clip sounds higher.

[cbarrow7625]

David,

Excellent! I love to see (hear) actual quantitative analyses of audio like this. It does remove a lot of the subjective nature of the listening. It also make sure that we are all talking about the same frequencies and ranges when we say "high","low", and "mid". Honestly, I wasn't even thinking about low end below 75 Hz in my listening, since that is underneath most of the fundamental tones on a guitar. The "low" I was focused on was the low end of the guitar in the fundamental range, 80-300Hz or so. Can you perform a bandpass analysis of these two clips in the ranges of 100-1000Hz and 1000-8000Hz as well? That would be really interesting to hear to help characterize the rest of the lower and upper mid range (as we must now define it, thanks to your analysis).

I agree that it is clear that the first unit lacks low end below 75 Hz after listening to those sound clips. Maybe it's just a combination of my Bose QC3 headphones and stock audio card, but I am having trouble hearing a significant difference between the high clips. That's probably OK though because it can be debated whether or not the highest frequencies belong in there at all (at equal amplitude) if we are trying to reproduce an accurate acoustic guitar sound. Most piezos have way too much artificial top end for my liking.

I would love to hear samples of the other frequency ranges if you have the time. Thanks!

[David Schwab]

I made an error in my low pass image file, I labeled the second clip as 1 and vive versa.

The high pass image is correct.

Sure I can do a band pass. I'm doing too many things at once though, so that has to wait a bit.

[Claus H]

I made an error in my low pass image file, I labeled the second clip as 1 and vive versa.

The high pass image is correct.

Sure I can do a band pass. I'm doing too many things at once though, so that has to wait a bit.

Hey thanks everybody, My DI is the second clip. They bouth have a very flat frequency response, The impedance of the first FET preamp is around 2.2M Ohm and my DI has above 5M Ohm. no tubes in it just bipolar transistors I love the way it sounds, sounds very natural to me. I will post the non edited clip to I cut a bit low end, below 75Hz same filter used on bouth clips..