• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

Peavey USB-P DAC Teardown

martijn86

Active Member
Joined
Aug 30, 2019
Messages
271
Likes
975
Location
The Netherlands
…only use this device if you have to and performance is not critical.

It's a weird day when someone holds you at gunpoint and forces you to use a sh#tty DAC but if that day ever comes, I'll remember your advice.
 

pma

Major Contributor
Joined
Feb 23, 2019
Messages
4,591
Likes
10,727
Location
Prague
kopczas, did you see Audio Precision trafo-feedback patent? They still use that as an output for their analog generator.

Attached. Excellent due to FB related design.
I have a good line trafo here as well and get below 0.001% (without FB of feedforward circuit) starting from some 400Hz and above.
AP_trafo.jpg
 

Labjr

Major Contributor
Joined
Dec 14, 2018
Messages
1,051
Likes
949
Not all transformers are created equal and good transformers cost real money. This is a US$50 item.

Consider all balanced gear from the distant past used 600 ohm transformers. I have CD players and DACs with transformers for the balanced outputs and the performance is very close to the RCA line outs.

Many classic tube mics have output transformers.
 

YSC

Major Contributor
Joined
Dec 31, 2019
Messages
3,194
Likes
2,570
it actually looks not badly designed with the components it used and the convenient of not requiring external power supply yet providing XLR out
 

Vasr

Major Contributor
Joined
Jun 27, 2020
Messages
1,409
Likes
1,923
Similarly, if you have all your gear thrown in the back of your station wagon, driving to the gig in order to set up your Peavey Audio Performer Pack (on sale now for $500!) ;), you might wish that you could bring your better equipped home studio with you, but this will do the job.

Instead of taking the Peavey out of its ball park to measure, you can take the SINAD leaders to Peavey ball park and measure.

Dump this one and the top dozen SINAD leaders into a gig bag without any packing, throw the bag into your trunk, drive 30 miles and then measure the SINAD of each. ;)

And then people can debate whether the presence or lack of output transformers led to the "poor SINAD" of some of them and whether you should buy those only if you have to.
 

LTig

Master Contributor
Forum Donor
Joined
Feb 27, 2019
Messages
5,760
Likes
9,442
Location
Europe
Hardly, sunshine. Transformers in this reviewed product are there for one very valid reason, just as the lack of similar devices in the Carver implementation were implemented for another, perfectly valid, but equally misguided reason.

Just because silicon derived line drivers have become reasonably silent and offer great on-paper specs, doesn't mean that in certain situations, an isolated, transformer driven solution, cannot provide a better overall performance.

As they say, there are many ways to skin a cat.
Yeah, FWIW: the analogue input of my K&H O300D uses an audio transformer.:eek: Can't blame bad sound yet. No hum and hiss.:)
 

Digital Mastering System

Active Member
Joined
Jan 3, 2020
Messages
142
Likes
170
Location
MN
One thing that could have improved this design would have been a buffer between the transformer and DAC. The DAC can only source quite low current. Adding a driver with a good low impedance output can significantly improve the low frequency performance of a transformer, and might pull 10dB of distortion out of it. I really expected to see some such driver. Disappointed it isn't there. I guess the feeble output swing was a clue.
The 2705 is a vernerable part. Treated nicely it was a competent DAC. Nothing compared to modern devices, but TI were rightfully proud of it when it first came out. However that was nearly 2 decades ago. It is now listed as not recommended for new designs. One suspects this Peavey DAC has been around for a while. Which might not be a surprise.
BOM is going to be roughly $5 for the DAC and $5 each for the transformers in quantity. Add a nice case, connectors and PCB. Really this is a fair price. Upgrading it significantly would well over double the price. More like quadruple. The next step up in transformers gets you to $20 parts, better DAC, proper power management, driver stage. Think well north of $200. Good transformers start at $100 each.
Galvanic isolation, affordable, audio quality: pick any two.

see: https://www.jensen-transformers.com/transformers/line-output/
 

Nango

Major Contributor
Joined
Aug 6, 2018
Messages
1,463
Likes
985
Location
D:\EU\GER\Rheinhessen
This is a teardown of the recently reviewed Peavey USB-P transformer coupled DAC. The internals are simple enough:

View attachment 96713

Data and power are provided via the USB bus. The core of the system is a on-chip USB DAC, the TI/BurBrown PCM2705. This is a low performance DAC designed for quick implementations. Here are the TI measurements for it:

View attachment 96714

I have converted the THD+N percentages to SINAD (in red). As you see, there are two implementations: one with USB power with worse results (left) and the other with stand-alone power supply (right). Neither is much to write home about. Ours is the one on the left which best case has a SINAD of 78 dB. In the review I got around 74 dB. The reduction is due to use of transformers on the output to provide isolated/balanced output (the main reason for this device's existence).

Transformers can generate a lot of distortions especially in lower frequencies. Let's go ahead and measure that using USB-P:

View attachment 96715

At 20 Hz and full digital level input, distortion shoots up to nearly 2% for a SINAD of around 35 dB! Most of our measurements are at 1 kHz which gives these a ton of benefit of doubt.

Lowering the output signal level improves transformer distortion but then signal to noise ratio worsens so there is not a lot of gain to be had as you see in the green and blue lines above.

I suspect this level of distortion is very much audible. So only use this device if you have to and performance is not critical.

------------
As always, questions, comments, recommendations, etc. are welcome.

Any donations are appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
More teardowns, quick and dirty!!
 
OP
amirm

amirm

Founder/Admin
Staff Member
CFO (Chief Fun Officer)
Joined
Feb 13, 2016
Messages
44,374
Likes
234,475
Location
Seattle Area
Dump this one and the top dozen SINAD leaders into a gig bag without any packing, throw the bag into your trunk, drive 30 miles and then measure the SINAD of each. ;)
There is no provisions in this DAC to make it shockproof more than any other DAC. Yes, if you have a display and volume control on a DAC, you have more exposure but there are balanced DACs without it. An example is Grace Design Balanced DAC: https://www.audiosciencereview.com/...asurements-of-grace-design-balanced-dac.8201/

index.php


And it has excellent measurements:

index.php


And plenty of output.

Notice how there is no trace of mains spike in its FFT output at 60 Hz and multiples.
 

Vasr

Major Contributor
Joined
Jun 27, 2020
Messages
1,409
Likes
1,923
There is no provisions in this DAC to make it shockproof more than any other DAC. Yes, if you have a display and volume control on a DAC, you have more exposure but there are balanced DACs without it. An example is Grace Design Balanced DAC: https://www.audiosciencereview.com/...asurements-of-grace-design-balanced-dac.8201/

At 3 times the price (and not through a retail chain with those margins added). That front knob is not going to survive gig bag excursions.

The point was it makes as little sense to judge (or have expectations on) this DAC as required in a home audio configuration as it does to judge the survivability of the home audio SINAD leaders in a gig bag. Especially if the SINAD measurement is going to make no audible difference in its intended application. Just different ball games.

That includes not just perturbing the electronics but also the ability of their cases to withstand abuse - of things knocking against it, of being dropped from a mixing console while trying to connect it in low stage lighting...

How many of the high SINAD flyers have had vibration or drop testing done on them? :)

Don't have experience with this particular DAC but I will bet that there are intentional design features in the case itself for the intended use. No dainty feet that can come off or sharp corners that scratch or put a dent in other equipment it comes in contact with. Non-slippery resting surfaces. Dent/drop resistant casing and rim offsets, etc.

One thing Peavey knows a lot better than building low-noise electronics (which they have not had to do in their application domain) is ruggedness to survive "field use". That is their business not high SINAD.
 
OP
amirm

amirm

Founder/Admin
Staff Member
CFO (Chief Fun Officer)
Joined
Feb 13, 2016
Messages
44,374
Likes
234,475
Location
Seattle Area
At 3 times the price (and not through a retail chain with those margins added). That front knob is not going to survive gig bag excursions.
Price wasn't your point. As to the second part, you just don't know. This is not a high-reliability product. You are just assuming so based on its simplicity but that is not data. It is assumption. Here are some negative reviews from Amazon:

1606855713821.png


1606855738572.png


1606855777770.png


1606855810464.png


And issues with volume being too low:
1606855857938.png


1606855911863.png


Really, there is nothing more to the device than it is. A cheap DAC with a pair of transformers on the output, degrading level and audio performance fair bit. If you are using it for work, I suggest looking for something more proper like I post before resorting to this. A pro interface with balanced out would certainly be an upgrade if you don't want to use a consumer DAC.
 
OP
amirm

amirm

Founder/Admin
Staff Member
CFO (Chief Fun Officer)
Joined
Feb 13, 2016
Messages
44,374
Likes
234,475
Location
Seattle Area
One thing Peavey knows a lot better than building low-noise electronics (which they have not had to do in their application domain) is ruggedness to survive "field use". That is their business not high SINAD.
This is a PCB in a "bog standard" hobbyist case. There is absolutely nothing special about its build to make it more reliable than it would be otherwise. You don't know if that DAC chip is designed to last longer and tolerate heat build-up and shock more than any other. It is not like it has rubber shock absorbers and such like a meter would:

4EB18_AS01


A Fluke meter has much rougher life than this device will ever have but keeps ticking because it is designed to be rugged. The Peavey is not so. A simple static shock through its USB port will send the Peavey to its grave as there are no protections on its input.

If you have one, I would carry it with care and not throw it in a bag to rattle around. If you do, then it may fail you when you need it....
 

Vasr

Major Contributor
Joined
Jun 27, 2020
Messages
1,409
Likes
1,923
As to the second part, you just don't know. This is not a high-reliability product.

You are saying things I didn't claim. Ruggedness and reliability aren't the same thing. Without ruggedness, this would be useless for its intended purpose. Reliability would be commensurate with the price. Not sure why you are conflating the two.

I am going by experience with Peavey products.

Look at any electronics device reviews on Amazon especially at this price level and you will see positive and negative reviews, so I am not sure what point you are trying to prove by cherry-picking.

If I can cherry-pick also

Screen Shot 2020-12-01 at 1.23.13 PM.png
 

Vasr

Major Contributor
Joined
Jun 27, 2020
Messages
1,409
Likes
1,923
A Fluke meter has much rougher life than this device will ever have but keeps ticking because it is designed to be rugged. The Peavey is not so.

This is getting silly. How much does the Fluke meter cost?

So, you want to use the Nirvana fallacy. Absolute high-performance design or it has nothing, reality be damned. For a $25 wholesale device which is more rugged than the $1000 products at the top of your SINAD list. :rolleyes:
 

Veri

Master Contributor
Joined
Feb 6, 2018
Messages
9,596
Likes
12,036
You are saying things I didn't claim. Ruggedness and reliability aren't the same thing. Without ruggedness, this would be useless for its intended purpose. Reliability would be commensurate with the price. Not sure why you are conflating the two.

I am going by experience with Peavey products.

Look at any electronics device reviews on Amazon especially at this price level and you will see positive and negative reviews, so I am not sure what point you are trying to prove by cherry-picking.

If I can cherry-pick also

View attachment 96795

Excellent for worship slides, doesn't get any better than that ;) ..
 
OP
amirm

amirm

Founder/Admin
Staff Member
CFO (Chief Fun Officer)
Joined
Feb 13, 2016
Messages
44,374
Likes
234,475
Location
Seattle Area
This is getting silly. How much does the Fluke meter cost?
Silliness is trying to be a salesman for Peavey. I don't understand your motivation to do any and all things to promote this product. The device was properly evaluated and its features and advantages stated clearly. Going above and beyond puts you on a plank going into the drink on a boat. Don't do that.
 

Vasr

Major Contributor
Joined
Jun 27, 2020
Messages
1,409
Likes
1,923
Silliness is trying to be a salesman for Peavey. I don't understand your motivation to do any and all things to promote this product.

What I said in the previous measurement thread
I am not sure this should even be reviewed here.

For those not familiar with Peavey, they are a low-mid end music instrument, amps and stage pro-audio equipment much below Marshall and Fender and I don't think they have ever built a low distortion product. :)

A lot of tweener budding guitarists start with a Peavey amp especially if into metal thrashing. They are cheap, loud and provide the needed distortion.
Does that sound like a salesman for Peavey?
I also said
Low distortion products are not what anybody designs to build in that business. Peavey is at low-mid end of that business.
Does that sound like what a Peavey salesman would say?

And then I was accused of this
I get it, you have an issue with Peavey for some reason, but you've really added no "context" as you like to put it. More like a bias and expectations not comensurate with price, utility, and the device actually in question.

I think being accused of being biased on opposite ends is a sign of being balanced and neutral. :) As I said in that other thread
I started my music playing many decades ago with Peavey which is all I could afford at the time and have fond memories. But I am not going to romanticize what it is not. It has its place and utility.

But what is unsavory is you using an ad hominem fallacy to disagree by characterizing me as a salesman for Peavey to imply that the points not valid/objective. Seems like I am making you too defensive to be objective. Not sure why.

The points I am making in this and the measurement thread are simple:
1. Peavey is in the music and public PA type of audio equipment business. This equipment is not known have or designed to be low-noise products.
2. Within the industry Peavey falls at the low-middle-end of the manufacturers. Creating low-noise equipment is not their business, their expertise nor are they going to be swayed by audiophile measurements to change that.
3. The typical use cases of this require some level of ruggedness and less SINAD requirements than typical home audio equipment. The flip side is that home audio equipment does not require the same level of ruggedness.
4. For this reason, it makes as much sense for this DAC to measured and judged in the standards of home audio equipment as it does for the home audio equipment to be judged for use where this would be deployed and the conditions under which it would be deployed.

I have been consistent with the above in both threads. You can disagree with it but using ad hominems like "determined to leave a sour taste", "don't act like a salesman for Peavey" etc to disagree is not intellectually honest.

I am getting myself out of this thread before you issue a thread ban or more. :D
 

MDAguy

Senior Member
Forum Donor
Joined
Nov 26, 2020
Messages
404
Likes
405
Location
San Francisco Bay Area
Transformer are apparently An Equal Opportunity Destroyer when it comes to DAC performance, whether it's this relatively cheap Peavey or an absurdly overpriced "high-end" unit from PS Audio.

Part of me can't help but feel that PS Audio is nothing more than "pretend" audiophile stuff.... It does't sound bad per say, it just doesn't sound as good as the price, and worse yet the build quality is bordering on crappy.

On the topic of Peavy... as a bass player, and someone who's bought and sold musical instruments in that domain for 3 decades, Peavy has never had a reputation for doing anything well, the closest they ever got is with their PA systems for budget conscious users... but in the end, they're a shockingly poor example of music products that makes Beringer seem premium by comparison.
 
Last edited:

Francis Vaughan

Addicted to Fun and Learning
Forum Donor
Joined
Dec 6, 2018
Messages
933
Likes
4,697
Location
Adelaide Australia
Perhaps the answer is simply that you can't make a better galvanically isolated DAC for this use case for the money.
No doubt, this is a bottom of the line solution. Cheapest possible USB DAC, cheap transformers, cheapest PCB and connectors, cheap generic case. But it isn't poor value for money.
To do better would cost at least double. There will always be a market for the cheap and cheerful product, and this unit fits that niche.

I would generally prefer to go for a two box solution. Just use an off-the-shelf isolation/DI box to isolate anything that needs it. Much more flexible, and you can use the box in many places, whereas the DAC is a one trick device.

Instead of transformer coupled output, it is possible to isolate the USB input. This requires transformer USB power isolation and a switching PS to get the power across. Then some form of data coupling - optical usually. The down side is that the output legs are not independently isolated. I notice that iFi makes such a DAC for about 400 euros. Has a stupid switch sticking out from the case, but otherwise looks rugged enough. They went with a proprietary isolation solution, which almost certainly adds to the cost as well as having their own woo factor adding to the price premium.

Or use a USB over fibre connection. Sadly again not price competative with such a simple DAC.
 
Top Bottom