Interesting new Moondrop product- DSP equipped IEM cable

[IAtaman]

I got a pair some time ago, wanted to try them but was not able to find the iOS app easily so left them in the box. I remembered I had them today but still can not find an iOS app from the QR code link - are these strictly Android?

 

[jae]

Is the cdsp just a less "premium" variant? Same specs?

 

[CedarX]

The Moondrop “Link” app exists on iOS—just search for “Moondrop” in the AppStore (for iPhone). However, with my iPhone, and a lightning to USB adapter, the app does not “see” the FreeDSP, and does not work. The FreeDSP is UAC 1/2 compliant, meaning it is seen as an audio device from iOS—you can play music, no issue. However, the communication between the app and the FreeDSP chip to upload PEQ’s is most likely base on a proprietary protocol. Apple has some very specific requirements for an app to directly interface with a Lightning-connected device. I believe Android doesn’t care much… and that’s why the app works. I don’t know about iPads or iPhone 15 and their USB-C connector.

 

[Blorg]

Is the cdsp just a less "premium" variant? Same specs?

No, it's also a different DAC.

Free DSP: up to 384/32, 9 band PEQ, only integer gain
CDSP: up to 96/24, 5 band PEQ, allows fractional gain

I get the impression CDSP is likely the same chip, same limitations as the Tanchjim One DSP cable, that is also 96/24, 5 band PEQ, allows fractional gain.

I think there also may be some other limitations that vary between them, like I think one has a max 3dB gain, the other disallows filters over 10kHz. I haven't gone through and checked which is which. But they are definitely two different platforms.

Moondrop also made claims of 0.0008% THD+N (102dB SINAD), 120dB dynamic range and fully balanced output on the FreeDSP, and backed these up with AP555 screenshots, they made no such claims for the CDSP. CDSP sounds "fine" with no hiss or obvious problem, but it's possible the DAC on the FreeDSP is of higher quality, with better measurements.

I haven't checked the power, will have to do that, see if they are the same or different.

The physical cable on the Free DSP is also quite a bit nicer, it's very like the TACables Obsidian which goes for $30 on its own (a bit cheaper here in Asia- but it is a "nice" cable).

 

[CedarX]

No, it's also a different DAC.

Free DSP: up to 384/32, 9 band PEQ, only integer gain
CDSP: up to 96/24, 5 band PEQ, allows fractional gain

Only integer gain: this one puzzles me… The number of filters is definitely a DSP chip characteristic, but the other limitations—integer gain, only peak filters, 10k max frequency—are more likely an app thing. Generally, DSP chips only need the biquad coefficients of each filter, but don’t care how these coefficients are generated.

BTW, if 5 filters (10 total for L+R) is relatively common, 9 filters is an odd number… Haven’t found an obvious USB-Codec / DSP / HPA chip that matches the description. I guess I’ll have to butcher my FreeDSP to find out… (not quite ready)!

 

[Blorg]

Only integer gain: this one puzzles me… The number of filters is definitely a DSP chip characteristic, but the other limitations—integer gain, only peak filters, 10k max frequency—are more likely an app thing. Generally, DSP chips only need the biquad coefficients of each filter, but don’t care how these coefficients are generated.

I suspect it's a chip issue, as it's the same Moondrop Link app being used for both the Free DSP and CDSP, but the CDSP has the exact same limitations and the Tanchjim One, using a different app, does (but doesn't have the integer gain limitation that the Free DSP has). 9 is odd, I thought it was 10, but no, it's 9.

 

[jae]

No, it's also a different DAC.

Free DSP: up to 384/32, 9 band PEQ, only integer gain
CDSP: up to 96/24, 5 band PEQ, allows fractional gain

I get the impression CDSP is likely the same chip, same limitations as the Tanchjim One DSP cable, that is also 96/24, 5 band PEQ, allows fractional gain.

I think there also may be some other limitations that vary between them, like I think one has a max 3dB gain, the other disallows filters over 10kHz. I haven't gone through and checked which is which. But they are definitely two different platforms.

Moondrop also made claims of 0.0008% THD+N (102dB SINAD), 120dB dynamic range and fully balanced output on the FreeDSP, and backed these up with AP555 screenshots, they made no such claims for the CDSP. CDSP sounds "fine" with no hiss or obvious problem, but it's possible the DAC on the FreeDSP is of higher quality, with better measurements.

I haven't checked the power, will have to do that, see if they are the same or different.

The physical cable on the Free DSP is also quite a bit nicer, it's very like the TACables Obsidian which goes for $30 on its own (a bit cheaper here in Asia- but it is a "nice" cable).

Thank you for the detailed explanation. Seems like there is still a little while to go before I buy one of these cable dsp dacs then. Each are decent, but both versions have obvious flaws/annoyances.

 

[Blorg]

Thank you for the detailed explanation. Seems like there is still a little while to go before I buy one of these cable dsp dacs then. Each are decent, but both versions have obvious flaws/annoyances.

The FreeDSP sounds very good both subjectively and Moondrop have measurements to back it up. The CDSP sounds fine as well, subjectively maybe I have a sense it's not quite as good but that could be my imagination/bias. It's unfortunate that the PEQs have the limitations they have but I was still able to do very satisfactory EQs with them. Most IEMs don't need extremely detailed correction, it's usually more about "a bit more bass" or "smooth out this bit".

Tanchjim cable 5-band EQ (same as the CDSP), to me this sounds much better after:

 

[jae]

The FreeDSP sounds very good both subjectively and Moondrop have measurements to back it up. The CDSP sounds fine as well, subjectively maybe I have a sense it's not quite as good but that could be my imagination/bias. It's unfortunate that the PEQs have the limitations they have but I was still able to do very satisfactory EQs with them. Most IEMs don't need extremely detailed correction, it's usually more about "a bit more bass" or "smooth out this bit".

Tanchjim cable 5-band EQ (same as the CDSP), to me this sounds much better after:
View attachment 322914

If the base IEM already has a good magnitude response, 3dB is not so bad. The issue is in this case need to apply EQ to a target but also to compensate for some hearing loss, so either a max of 3 dB or 10kHz limit is not going to cut it. I need to get a Qudelix-5k, although I've been holding out on that purchase anticipating a new version/hardware revision.

 

[Blorg]

If the base IEM already has a good magnitude response, 3dB is not so bad. The issue is in this case need to apply EQ to a target but also to compensate for some hearing loss, so either a max of 3 dB or 10kHz limit is not going to cut it. I need to get a Qudelix-5k, although I've been holding out on that purchase anticipating a new version/hardware revision.

Bear in mind you can rejig your EQ so it cuts rather than boosts. Like, if you need +6dB to correct a dip, you can cut the peaks either side instead. It's a pain if you are doing it fully manually, just in terms of thinking about it, but it's possible.

If you are using AutoEQ, you can tell it, peak filters only, no more than 3dB gain, under 10kHz, 9 bands, and it will give you the EQ with those criteria. You can always tweak manually from there.

A broad Q peak filter at 10kHz will affect up to 20kHz, you just need to bear in mind it affects below 10kHz as well- but you can compensate for that with another filter below. But you can certainly tweak the high treble up or down a bit... besides which, if you have hearing loss I doubt much over 10kHz matters that much anyway.

Qudelix 5K is certainly more flexible, but these are nice for much cheaper cables you just leave on an IEM, even the going into the menu of the Qudelix to pick the EQ is an additional hassle.

 

[CedarX]

Some (small) progress about figuring out what chip (USB bridge / DSP / DAC / HPA) is used in these DSP cables/IEMs:

• The Tanchjim Zero-DSP, One-DSP (detachable cable), Tanya-DSP IEMs, the Moondrop CDSP cable, the Fiio LS-TC1 cable, and the TRN TE DAC AMP dongle, all use a KTMicro KT02xx chip. TRN is the only one indicating what chip it is: a KT02F20, which is UAC-2 compatible, up to 24/192 and DSD-capable (unlike the Tanchjim's, CDSP, and Fiio cable). The TRN TE dongle is higher end.
• The Moondrop Quarks-DSP and 'The Droplet' IEMs appear to use the same chip, at least viewed from the USB side. Not KTMicro, limited to 16/48, and with no app support.
• The Moondrop JIU appears to use another chip, different from the Quarks and Droplet and it is supported by the Moondrop app.
• The Moondrop FreeDSP uses yet another chip...

With the Monndrop Link-II app, you have to select the device you want to configure first. I believe that the point where the proprietary communication between the App and the device starts. The Tanchjim app works a little differently: it always tries to communicate with whatever USB device is connected. The Tanchjim app appears to recognize any KTMicro device. So, the Moondrop CDSP, Fiio LS-TC1, and TRN TE are all identified correctly by the Tanchjim app--even if the app does not let you do anything with these.
The interesting point is that the Fiio cable and TRN dongle DSPs should be configurable (to-do: USB sniffing, spoofing the Tanchjim app ), unless Fiio and TRN locked them down...

I have yet to check whether the FreeDSP output is differential (balanced), whether it is unique among these, and get some measurements (more to-do's... )
I also have a Ugreen KT0210-based dongle on order.

Why am I interested in all that stuff? Because, as @Blorg said above, they are cheap enough to leave on an IEM permanently (and USB-C is becoming quite ubiquitous), and because they are probably right around the "audibly transparent" threshold (likely lower: I suspect they ain't gonna break any SINAD record on ASR wall of fame). I am curious how good an entry-level IEM could become with the help of a fine-tuned, personalized EQ. I see the fun potential... and hope to learn more on a dime!

 

[otseiTiesto]

@CedarX

Great idea!
Would be great if we could find a datasheet. I have tried my usual site to get datasheets, but it does not work.
If it is written in Chinese, this site may help, but sometimes it works well, sometimes not.

 

[MCH]

Seems that this might get ca. 25eur shipped next week, according to Shenzhen audio AliExpress store, low enough to give it a try given that the only headphones I have compatible with its connectors don't need much EQ...
Anyways, my silly question is: can you set the EQ using the app and then use the dongle with the uploaded eq with any other USB source? I guess and hope this is how it works, but wanted to make sure.
Thanks!

 

[staticV3]

Anyways, my silly question is: can you set the EQ using the app and then use the dongle with the uploaded eq with any other USB source?

Yes. The EQ is stored on the cable.

 

[MCH]

Seems that this might get ca. 25eur shipped next week, according to Shenzhen audio AliExpress store, low enough to give it a try given that the only headphones I have compatible with its connectors don't need much EQ...
Anyways, my silly question is: can you set the EQ using the app and then use the dongle with the uploaded eq with any other USB source? I guess and hope this is how it works, but wanted to make sure.
Thanks!

Ok, ordered one (final price 21.98 eur, part of a larger order). What do you think guys, is it worth starting to search adaptors for my not compatible headphones (hd600 and etymotic er2se) or better not bother for some reason (i.e. it can't drive them etc).
Notes: I don't listen at high volumes. This is mostly to play/experiment, I am not trying to solve any issue.
Thanks!

 

[Jeromeof]

So my Moondrop FreeDSP finally arrived and that Moondrop Link App is terrible.

Obviously Moondrop are an audio engineering company and not a software engineering company (like say Wiim / LinkPlay that provide an excellent App for their products).

My plan was / is to setup PEQ I want on my old Android phone and then use the FreeDSP on my new usb-c enabled iPhone to basically give me system wide EQ, but their Android app is putting me off (and the IOS doesn't work at all with it). On Android sometimes it connects then other times I have to restart the app, the UI is terrible (though probably functional as far as the PEQ is concerned).

Obviously this is a Moondrop product and I do see 'profiles' where you tell the app what Moondrop IEM you are using and then what sound signature you would like but I do think they should use AutoEQ - to download the FR of your current IEM (no matter what the brand i.e. source IEM ) and then select a new Target IEM Frequency response. This could have been the 'pleasure' of a cable like this - tell it what you have and then what you want !!!

But I do see some third parties profiles (e.g. searching for example 'Truthear Zero' there are at least some 'community' PEQ uploaded).

 

[Matias]

Measurements below, kind of disappointing jitter performance.

Moondrop FREE DSP Review & Measurements

[TableOfContents] Introduction Video Review Design Software Measurements [End] Introduction The Moondrop FREE DSP is a cable that features an inbuilt DAC and amp to directly power IEMs without the need for a separate dongle, but most importantly, it offers the ability to load EQ profiles...

headphones.com

 

[Jimbob54]

Measurements below, kind of disappointing jitter performance.

Moondrop FREE DSP Review & Measurements

[TableOfContents] Introduction Video Review Design Software Measurements [End] Introduction The Moondrop FREE DSP is a cable that features an inbuilt DAC and amp to directly power IEMs without the need for a separate dongle, but most importantly, it offers the ability to load EQ profiles...

headphones.com

Cant argue with any of his assessment including the functionality side of things . Got a couple of FreeDSP today and its a decent cable, even better that it has a DAC attached, but the DSP side is a bit lacking for the reasons he states.

Better software would help.

Get them for convenience of not needing a dongle but not as a replacement for proper EQ for eg via uapp on Android.

 

[CedarX]

Jitter is certainly disappointing, but is it “good-enough”? Audible? Worth the tradeoff of having a convenient—if not perfect—built-in DSP?
The App is certainly not perfect (I prefer the Tanchjim App), but I see the FreeDSP as something you tinker once and forget for a given IEM, so to me, the limitations/tradeoffs are acceptable.
I may be wrong, but I don’t recall the app asking for full access to all files. What Android clearly asks each time is to grant the app permission to access the USB device (FreeDSP), but I believe it’s an Android default (good!) protection.
As for the 10kHz limit: if the DSP filters are biquads-based, it may be Moondrop limiting the EQ range l, to avoid the issue of a Fs-dependent EQ response above ~10kHz.

 

[Jeromeof]

The App is terrible - I did contact Moondrop about the App, specifically if an IOS app might appear but also about the various bugs and they indicated an IOS app was in development but no timeframe.