[dlaloum]

Hi Folks
 
I am interested in the Cute Curve amp http://www.firestoneaudio.com.au/index.php/cute-curve-headphone-amplifier.
 
I have heard that it is the same as the amp in the Fubar IV without the DAC.
 
Would like to know about peoples experiences with it - particularly with hard to drive headphones such as the Beyer DT880/990-600ohm
 
I am considering purchasing one, they also have an optional power supply upgrade - 24V.
 
I do however have a spare Creek OBH2 psu lying around - would this work with the Cute Curve?
 
thanks
 
David

 

[dlaloum]

Further news
 
I purchased one - it arrived today, I have yet to try it...... (over the weekend)
 
The included specifications leaflet in the box tells me that it is a Class A design using the OPA2604
 
The Specifications online say that it is Class B
 
To the best of my knowledge the OPA2604 is normally a Class AB design, and by raising the biasing current one can increase the proportion of Class A to Class B operation.
 
Anyone out there had a look at the Cute Curve to determine what kind of circuit it uses?
Is it as advertised online - a pure class B?
 
Or is it in fact a Class AB (and therefore both) - resulting in the confusion all over the place!
 
I am also keen to find out from the online brain trust - whether it would be safe to increase the power supply voltage...
 
The 2604 opamp is reputed to be particularly good at higher voltages (+/- 18V to 24V) - the Cute Curve receives 24V which probably results in the opamp being fed +/- 12V - or well outside this chips optimum supply power.
Question is though what would be the impact on the rest of the circuitry of upping the voltage from 24V to circa 40V (as an example) - to allow for +/- 20V - or maybe just 30V to achieve +/- 15V and maximum opamp compatibility (ie look at rolling )
 
Comments / thoughts  welcome
 
David
 
 

 

[dlaloum]

Just got word from Firestone Audio (Kerry.ko)
 
1) Confirming that the Cute Curve is a Class AB amp (A up to a certain level before switching to B)
2) With regards to PSU Voltage the answer I received was: [size=10.0pt].        There is part of Virtual Ground in the circuit and there is a chip as TL071 that will limit the increasing of the voltage.[/size][size=10.0pt]  No matter TL071 or TL072, we do not suggest to usage the voltage to +/-18V. The highest level will just reach +/-15V. [/size]Therefore, it is ok that the curve can be used with 30VDC adapter.
 
So my laymans interpretation
 
1) Sound is likely to be improved by using an appropriate (clean, filtered, etc...) 30V PSU, which would then run the main opamp at +/- 15V rather than +/- 12V - this should put a bunch of the better opamps closer to their optimum environment. (unfortunately rare as off the shelf items..... and $300 lab PSU's would defeat the purpose of an economy setup like this one!)
 
2) As delivered the amp runs in Class AB and could therefore potentially be modded to bias it further into Class A via 2 resistors (as per Purrin's mod on the Matrix M-Stage)... I am looking for some confirmation on this second assumption, as this would still be class AB just more heavily biased into A. (ie it is possible albeit unlikely that the amp is already using this method)
 
I will post further information if/when I receive it