UPDATED 2/22 REVIEW 13 USB DAC amp - Predator, Pico, 2/3MOVE, D10 D3 D2 Viper/Boa D1, Lyrix,... - Page 18

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Are these ones that are available a special high gain version or special OEM order?

The D2 Viper with LM6172 in the main amp and THS4032 is fantastic with my 47 ohm Altec Lansing IM716 (sibling to the ER4) and adds great bass and warmth to these IEM without needing to be switched into high gain, so I suspect that would be #1 with the ER4. http://www.head-fi.org/forums/f103/s...ess-up-338443/

However, in my testing above, while the modded Viper was best I still thought the IM716 had good sound quality with ALL of the amps I tried. I had the Headsix in low gain for my testing and it really needs to be in high gain with those IEM, but I didn't want to open it up to change the gain. SO, for that reason I think the Boa is probably a better choice than Headsix, because the Boa gain switch is on the outside and since the Boa is warmer than the stock D2 Viper.

I have read that the ER4P are hard to drive, which you seem to confirm, so even one of the high gain Vipers out there should be able to drive the ER4P without concern about hiss (which with very sensitive IEM like Shure SE530 or Livewires or Freq customs hiss can often be a problem). But if you did get hiss you could always get a P-S adapter for the ER4P.

There is a "high gain Viper that was ordered as an OEM project and a few accidentally shipped to people with pre-orders of the Viper - this had lo/hi gain switch, but both settings multiplied the gain more than a typical viper (good for people with a very quiet or low output source). Very few people have these, and I don't know who is selling the high gain model for sure.

As for warm vs thin or cold - I think warm and liquid midrange also depends on the headphones being used, not just the amp (remember synergy). With my Proline 2500 or AKG K240M 600 ohm, I find the Predator, D2 viper w/rolled opamps, 2MOVE and Headsix are more neutral than warm - but with other headphones the amps are warm. Then you pair a Pico or stock D2 with those same headphones above and it sounds a little thin (the RS-1 are kinda in between, straddling the fence). But use a Yamaha HP-1 ortho, Denon D2000, HD600 or Edition 9 with the Pico or stock D2 or Micro Amp and you get warm again. And being "warm" doesn't always mean "forward" sounding too, because I find the D2000 and RS-1 with the right amp to be warm but not too forward, while the HD600 and Edition 9 and others are warm and often more forward sounding with those same amps.

When I used the SA6 in my IEM/Amp synergy impressions thread, I did find them warm with Predator, Headsix, Headstage, TTVJ or D2 with certain opamps - but with the Pico or D2 with THS4032 or LMH6622 in the main amp the SA6 were closer to neutral.

Going back to the D2000 "warm but not forward", another example (although unrelated) of warm but not forward sounding is my Stax SR-Lambda or Lambda Signature (with 3 out of 4 amps), while the Stax SR-5NB are both warm and forward regardless of the amp. But if use a Sennheiser HEV70 amp it will make the Lambdas sound forward because it is more midrange oriented - that freq response suits the Senn HE60 better, while the Stax SRM-1 amp makes the HE60 sound thin and more distant (Woo GES or SRD-7 pro fixes that) it makes the Lambdas sound just right. So, again it is all about synergy or lack thereof.

Anyway, I think I tend to focus on the 250-1000Hz range lower mids when discussing warm vs thin - I can't recall a headphone that is full in that frequency range that also lacks mid-bass bass yet (although the K240M 600 ohm are close). I suppose some people would call it thin if the bass was lacking but the mids were still full, but I just call that bass-lite or lacking impact (depending on what is missing).

I will be getting a review sample of the Vivid Technologies V1 USB headphone amp soon. It may end up being the best bang for the buck USB DAC amp at $99 + $7 S&H, so I am eager to review it after I burn it in. (Basic Lyrix with DAC is $129 + S&H)

I am in the information gathering stage right now, but I will post more when it comes time to post the review. Similar to the Headstage it uses an AD8397 opamp, and it uses the PCM2704 DAC chip, automatically switches between DAC input & analog when you plug something into it, charges via USB and also has an optional rapid charger that speed up the 5v charging by a factor of 3, is a small 2.6" square by 1.1" tall, and gain of 14db I think is close to a gain of between 5-6x, and has a 1yr warrantee.

vividaudiotech.com - Headphone Amplifiers

Not sure I understand - you've heard it and they sound alike, or the specs are similar?

I thought the bithead uses AAA battery without charging, and has crossfeed, and a funky case.

The Lyrix specs are similar as well, in that regard.

The DAC does not hold the 2MOVE back, it may not be as sophisticated as the Pico DAC but it does a good job of detail extraction without much negatives - the slightly smaller and more intimate soundstage of the 2MOVE vs the Pico is just as much a function of the 2MOVE amp as it is the DAC section. It retains much of that flavor even when fed an analog source into the 3.5 mm input.

I am not an EE so I am explaining this as basic as I can and may still only be 90% right - an opamp in the ground channel is referring a 4-channel architecture in the amplifier where there is both an opamp in the main amp section and one in the ground - instead of other amps that might use a different ground railsplitter design (like using a TLE2624 chip for the ground reference that can't pass as much current as the 4-channel design.

I don't know much of anything about the design of the 2MOVE and what is inside, sorry.