Pros - A very integrated package. SQ's highly detailed with decent bass and great treble extensions.
Cons - Battery life short, jacket suited only for the iPhone 4/4S, aluminium back scratches easily
Go-DAP 4.0 OpAmp Comparison Review
For the past few weeks I've had a couple of Go-DAP 4.0s on loan for a review. Some of you may know that in the past 6-7 months I've had bought a couple of Go-DAPs, upgraded them, then got rid of one. I started off with the Muses 8820E first back in early October and very soon after the BurrBrown OPA2134. Then VentureCraft announced they were providing upgrades to the OpAmps offering 3 versions, OP-275, AD8397, and OPA-2604. I upgraded one Go-DAP to the OP-275, and another to the AD8397.
Since then, VentureCraft has offered another OpAmp, not as an upgrade but as it's own Unit 4.0 - the OPA1612.
I kept my AD8397, sold the OP-275 to a friend and for the past few months the Go-DAP 4.0 AD8397 has been my favourite portable DAP.
Current Go-DAP Comparisons
I've talked about my AD8397 in the past in some Go-DAP threads so I won't be talking about this OpAmp. However I have managed to secure the original Muses 8820 & the OPA1612 on loan from VentureCraft and this review is specifically about these two models.
Aside from the aforementioned Go-DAPs, my tests involve using the Ultrasone Edition 8's , Unique Melody Merlin's, and V-Moda M-80's. My audio files are a mixture of 256k AAC, 320k AAC, ALAC, and FLAC (via FLACPlayer). My tracks used are Phantom of the Opera, Gerry Mulligan's Night Lights, Paul Desmond's Bossa Antigua, Black Eyed Peas' E.N.D., & Michael Buble's Call Me Irresponsible.
Note that all the Unit 4.0 Go-DAPs use the AKM AK4353 DAC so the comparison is primarily on the OpAmp.
In general, if one is looking for a completely integrated DAC/Amp to the iPhone 4S, in my humble opinion, nothing beats the Go-DAP. I know many Head-fiers have concerns that the integrated iPhone 4(S) jacket is limiting especially Apple comes up with new iPhone models annually. However if most people buy the iPhones on contract, usually the contract is 2 years so one could get a 2 yrs life out of the Go-DAP. In addition, one could always buy a iPod extended cable and hook up any iDevice to the Go-DAP.
Here are the notes I've written up when comparingthe OPA1612 with the Muses 8820E
Probably the most prominent difference between the two is the 1612 seem to have more depth and more full bodied (apologies if I'm using wine jargon in my comparisons here)
The 1612 also lean towards a more 3-dimensional soundstage over the 8820E. That's not to say that the 8820E doesn't have much soundstage as it's reasonably wide however the 1612 seems to add depth to the width. The 8820E seems more "flat".
Across the frequency range, the 1612 seems to have more impact. It's not necessarily "in your face" but whether it's primary vocals, or instruments seem to have more distinction.
Along with the impact (and probably the cause of the impact) is the 1612 is somewhat more detailed and clear
Both the 1612 and the 8820E have a wide soundstage however the 1612 has a slight edge over the 8820E.
The 1612 also has (ever so slightly) an edge over the 8820 in terms of treble extension. At times the 1612 could sound more "bright" and for headphones like the Ultrasone Edition 8's, one may find it fatiguing. The 8820 may be better for such headphones for extended play.
The 1612's mid bass seems seems more forward too than the 8820. In terms of bass extension though, I think both are the same. At least to me they are full enough with the Merlins and with the M-80's.
Overall, I feel that the 8820E is fine for extended listening to music and seems suited across all genre. Whereas the 1612, I find myself immersed into the music.
Other Aspects of the Go-DAP
I found the gain settings on the Muses 8820E to have a bigger difference (between low and high) than the OPA1612.
The 1580mAh battery charges a dead iPhone 4(s) up to about 54% before it kaputs. But very strangely the 2000mAh (the one that comes with the OPA1612) doesn't charge the iPhone 4(s) fully either. I got as high as 68% before the 2000mAh battery went flat. The charging is probably a little too quick...both cases of the 1580mAh and the 2000mAh, it drains in less than 1 hr. This is without using the Go-DAP for music.
The Go-DAP is reasonably pocketable...it is large however, it is integrated. Carrying something like the HP-P1, or CLAS+Amp is definitely less pocketable.
The brushed aluminium back scratches very easily. So one has to be very careful with it.
The Go-DAP can be used as a transport too with an optical out. I've chained up the Go-DAP to my Benchmark DAC1 Pre but to me it sounds flat in comparison to optical out from my iMac or iBasso DX100. Talking to the makers, the Go-DAP apparently up-samples from 44.1kHz to 48kHz and this is a side-effect of the up-sampling. I have not yet tried loading up a 48kHz ALAC/AAC to see if this flatness disappears since no up-sampling is required then. I'll try that later.
Go-DAP vs other iDevice DAC/Amps
I have actually owned the Fostex HP-P1, CLAS, Pico Slim, and RSA SR-71B. In my honest opinion, the Go-DAP is up there with the rest of them and in my personal opinion I'd lean towards the Go-DAP even for SQ alone. I feel it has a slight edge over both the HP-P1 and the CLAS in terms of detail and whichever OpAmp is chosen they seem to provide a decent amount of bass and treble extension.
NB: Based on memory from last year, the OP-275 on the other hand doesn't seem to have the same treble extension as the AD8397, or OPA1612.
As a complete integrated DAC/Amp package for the iPhone 4(s), the Go-DAP 4.0 is the only product I know. All others are either separate component attachments, or Amp-only integrated package (iFuzen for example).
Venturecraft does ship the basic Go-DAP 4.0 model overseas from their online site :-
However if you're looking at the customised versions like the ones mentioned above, the details are at the bottom of the home page and you'll need to mail VentureCraft on the customisations you require. They will have to give you a mail quote.