[estreeter]

Quote:

Epiphany Acoustics in the UK are taking preorders for their first batch of O2 amps now. £100 plus shipping, fully built with a properly finished/labelled casing.

Wiggy, did they give you any details about opamps, (individual) measurements etc for your amp ? I appreciate that its not a custom order amp, but something beyond 'thanks for your deposit' would be nice.
 

 

[Hi-fi Wigwammer]

 
Quote:

Wiggy, did they give you any details about opamps, (individual) measurements etc for your amp ? I appreciate that its not a custom order amp, but something beyond 'thanks for your deposit' would be nice.
 

Just had a reply from Oliver at Epiphany Acoustics:
 
 
The Opamps are the NJM2068D and the NJM4556AD. The gain settings 3.1x low gain and 6.5x high gain.
 
Measurements etc.

1. THD @ 1kHz: 0.0017%
2. Noise level (ref 400mV): -105dB
3. IMD: 0.001%
4. Power output @ 33Ω : 641mW
5. Crosstalk: 65dB
6. Channel balance 0.6dB
7. Battery life: 8 hours

 
 
 
I hope thats helps a bit?
 
 

 

[limpidglitch]

Do you know if other gain settings can be requested, or if the gain resistors are socketed?
3.1X is rather a lot when using IEMs and a 2V source.

 

[Hi-fi Wigwammer]

Sorry, but I really don't know. You can e-mail Oliver at oliver@epiphany-acoustics.co.uk for more info.

 

[micmacmo]

Quote:

Do you know if other gain settings can be requested, or if the gain resistors are socketed?
3.1X is rather a lot when using IEMs and a 2V source.

According to the O2 site, "Gain Switch – The out position is Low Gain (2.5X or 8 dB) and the in position is High Gain (6.5X or 16 dB)." Interesting that Oliver went with a slightly higher low-gain setting.
 
The BOM includes an optional socket for the resistors, so it's certainly possible to get a socketed version. It could be just a matter of asking. 
 

 

[estreeter]

Thanks for the feedback Wiggy - I'm hoping that your good self or one of the other 'early adopters' of the EPH-02 will start a separate impressions thread when you receive your amp - I ordered mine at least a week after you. Sure, its a 'stock' Objective2 implementation, but I think others may be interested as (afaik) its the only commercial offering of the amp atm - not sure if MrSlim has started on another batch.
 
As far as the gain goes, I mainly use fullsize cans with my amps so I'm not particularly concerned about those settings. I admit that I have some misgivings about a design that is intended to be 'all things to all people' up to 600 ohms - my experience with Rev 1 of the uHA-120 was that it wasn't a good fit for IEMs, and Justin subsequently revisited his gain settings and recommended the stock pot over the optional Vishay for IEM users. 

 

[estreeter]

I hope my photos turn out as well as this HK DiYers did:
 

 

[limpidglitch]

Looking good, but I hope he's not planning to recharge those batteries like that.
 

 

[estreeter]

I think its a work-in-progress, but it goes a long way to explaining why the footprint of the amp is more 'transportable' than 'portable' -  for my purposes, this IS the 'desktop version' !

 

[limpidglitch]

I was thinking more that if he were to plug in the AC, those batteries would explode.

 

[estreeter]

All part of the reason why I'm having a professional assemble mine. At least he became a professional the day he start accepting deposits to build the Objective2 ! 

 

[shadow419]

Quote:

I was thinking more that if he were to plug in the AC, those batteries would explode.

Actually, the design charges NiMH batteries when it's connected to AC.  A nice feature in my book.
 
err. ninja edit:  just noticed those are li d'oh

 

[mikeaj]

Quote:

Do you know if other gain settings can be requested, or if the gain resistors are socketed?
3.1X is rather a lot when using IEMs and a 2V source.

Good question.  I know MrSlim was building them with socketed resistors.  Or at least he said so earlier.  Fortunately, if you want 1x gain, all you need to do is remove the resistor for each channel (snip snip).  I think I'll be leaving out those resistors to have 1X gain be the low setting.
 
 
Quote:

Quote:

According to the O2 site, "Gain Switch – The out position is Low Gain (2.5X or 8 dB) and the in position is High Gain (6.5X or 16 dB)." Interesting that Oliver went with a slightly higher low-gain setting.
 
The BOM includes an optional socket for the resistors, so it's certainly possible to get a socketed version. It could be just a matter of asking. 
 
Mo

As I recall, originally the low gain was 3.1X.  Later revision changed the default to 2.5X.  Maybe Oliver didn't catch that?  If so, there are a few other changes since the original revision, that reduce turn on/turn off transients (I think) and reduce hum while charging batteries.  Maybe Oliver made a mistake in saying what it was, since I don't think he would have missed all the later revisions.  After all, he ordered the PCBs based on the latest O2 revision.
 
Actually, changing the default low gain was in response to input clipping concerns, though personally I think 2.5X or even 2X is a more appropriate choice in general for low gain because of IEMs and other more sensitive headphones.  With 3.1X gain and some really hot source with no volume control and full scale output above 2.25V (rms), the amp will clip the input (regardless of the amp's volume control setting), even on AC power.  Then again, this wouldn't be the only amp to clip with really high input levels.

 

[normalwrong]

Are these the best opamp??
Should i get them from ebay..? Is it likely to be fake?

 



Just had a reply from Oliver at Epiphany Acoustics:


The Opamps are the NJM2068D and the NJM4556AD. The gain settings 3.1x low gain and 6.5x high gain.

Measurements etc.

• THD @ 1kHz: 0.0017%
• Noise level (ref 400mV): -105dB
• IMD: 0.001%
• Power output @ 33Ω : 641mW
• Crosstalk: 65dB
• Channel balance 0.6dB
• Battery life: 8 hours

I hope thats helps a bit?

 

[estreeter]

Quote:

As I recall, originally the low gain was 3.1X.  Later revision changed the default to 2.5X.  Maybe Oliver didn't catch that?  If

Oliver is building mine with gain set at 2x and 5x - that should be fine for my undemanding can collection. Thanks for the info though - nwavguy has written so much on his blog that it can be hard to keep on top of it all.