So, the Objective2 headphone amp - designed entirely around the measurements? (PLEASE READ RULES BEFORE POSTING)

[kwkarth]

Quote:

The amp shouldn't "sound" like anything.

Please, let us not quibble over farkles 'n' fairy dust.
 

 

[The Monkey]

Everyone relax and just build the gotdam thing.  Children.

 

[c61746961]

Maybe you should wonder why.

You know what?, I question your motives and attacks more than his*, and you should wonder why, since you have a social responsibility here, and he doesn't.

* You keep openly judging people and locking threads whenever someone questions the forum's policies, you also pass your opinions as facts as much as anyone else, I know this is a big place, it's free, and there's lots of work to do, but power comes with responsibility, and a forum is nothing without its audience.

Back on topic, I don't know how can some people still be weary about this, there is already a product, there's absolutely no point in speculating anymore.

 

[BobSaysHi]

subscribed. I'll wait for others to get this amp and give it a once over before I buy anything though.

 

[qusp]

Quote:

 

Words of wisdom! A perfect amp does not draw attention to itself.

 
you didnt seriously just open up a can of wisdom on his ass did you? it really isnt the time or place for portable audiophile hiaku 

 

[nikongod]

Serious thoughts:
 
In the schematics posted on the first page:
u2b (one of the op amps used as a voltage source in the PS) does not have a 270Kohm resistor on it like U2a. These resistors and the0.22uf caps block anything but DC from reaching the mosfets. 
 
Why arent the mosfets Q1/Q2 in the feedback loops of the opamps? It would reduce the output impedance of the power supply which would probably drop the crosstalk of the amp. 60db is "good" not "excellent" if we are talking about measurements without reference of audibility. 
 
R25 could be exchanged for a JFET CCS or a CRD. CCS's are pimp. 
 
The bandwidth limiting resistors and caps before the opamps is a nice addition. I hope this catches on in other amps. 
 
Im 50/50 on the idea of the "opamp before the volume control" thing. Its not conventional, but has been done before. It solves the problem of noise from the opamp elegantly, BUT the gain stage is prone to overloading with excessive input voltage. This is noted on the schematic - its worth noting if you hook up to pro-level outputs. The fist kid who figures out how to set the gain to 10 (because 10 is more and more is better :facepalm: ) is going to have a wild ride. 
 
The selected gains of 3 and 7 are pretty tasteful. Id lean towards just one. 3 or 4 covers you for 99% of all headphones, people just like switches.
 
I think the 0.8db channel matching quoted in the test data may be misleading. Channel matching is primarily a function of the channel matching of the volume control, which is not generally great in those little pots. Maybe they all line up nicely at maximum volume, but at real levels Id bet on worse. Not really a fault of the designer just saying...
 
Coupling caps, UGGGGGGH. UGGGh, uggggh. Thats the kind of stuff you'd expect to see in the kind of tube amp a guy like nikongod would design. Why not DC couple it? Ugggggh. At the very least put them in front of the pot where the signal is larger. Uggh, really? And just no. I guess they will save the headphones (sort of, but no) if the gain opamp goes all funky with excessive input signal. 
 
I like the option of an output resistor outside of the feedback loop for the output op amps even though nobody will use it. I wonder if this admits the importance of subjective quality in spite of "knowing" how to do it right. heh. Id put a switch across this one so the user can switch on the fly like on the XIN amps. Its a good spot for ferrites or hand wound inductors should the need arise in actual use. 

 

[c61746961]

That's interesting. You should question those design decisions in one of the places he can get into, though. The diy audio thread would be a great place.

 

[nikongod]

Quote:

it really isnt the time or place for portable audiophile hiaku 

you called?
 
wow this amp is great
it fits nicely in my hand
but it sounds like trash
 
Not directed at any amp in specific.
 

 

[maverickronin]

Quote:

I like the option of an output resistor outside of the feedback loop for the output op amps even though nobody will use it. I wonder if this admits the importance of subjective quality in spite of "knowing" how to do it right. heh. Id put a switch across this one so the user can switch on the fly like on the XIN amps. Its a good spot for ferrites or hand wound inductors should the need arise in actual use. 

Well a few headphones here and there are supposedly designed for non-zero output impedance.

 

[nikongod]

Quote:

Well a few headphones here and there are supposedly designed for non-zero output impedance.

I know, Im all about it (listening to HD800 from an amp with 450ohm Zo and loving it) jsut that its a monor thing that I like. Im mostly bummed so few people try it. 
 

 

[ujamerstand]

Quote:

you called?
 
wow this amp is great
it fits nicely in my hand
but it sounds like trash
 
Not directed at any amp in specific.
 

 
 
 
now that's signature worthy material.
 
 

 

[maverickronin]

Quote:

I know, Im all about it (listening to HD800 from an amp with 450ohm Zo and loving it) jsut that its a monor thing that I like. Im mostly bummed so few people try it. 

Did Senn specifically design them for that or did you just play around with different resistors until you found something you liked?

 

[digger945]

Quote:

I know, Im all about it (listening to HD800 from an amp with 450ohm Zo and loving it) jsut that its a monor thing that I like. Im mostly bummed so few people try it. 
 

I'm gonna try it.
 


Quote:

 
 
 I guess they will save the headphones (sort of, but no) if the gain opamp goes all funky with excessive input signal. 
 
 

heh, or a cold or forgot-to-solder feedback resistor. Rail slam + parallel buffer = magic smoke.
 
 
 

 

[nikongod]

 
Quote:

Did Senn specifically design them for that or did you just play around with different resistors until you found something you liked?
 

There is an optional standard for 120 ohms that it "feels" like they follow. 
 
The amp has this output impedance by chance. I got the HD800, plugged them in, and was like whoa! 
 
I know a few people who own 800s and B22's who dont like the amp. Maybe its what Im used to, but I like how it calms down the highs just a touch. 

 

[DingoSmuggler]

 
 
Quote:

heh, or a cold or forgot-to-solder feedback resistor. Rail slam + parallel buffer = magic smoke

 
Ha ha - but with $0.70 opamps, the magic smoke has a less pleasing aroma than most magic smoke.