O2 amp CRC, diode, cap, and heatsink mods

[BlueRob]

Fortunately for me I haven't decided or bought the suggested B2-080 box so I will have extra room for accommodating the bass boost switch

On the other hand, may be a third DPDT Pushbutton Switch like the one listed in the BOM for the gain boost might fit the B2-080 box, and help to solve the clearance issue for the chaps like jschristian44 who are dealing with this mod...it seems to be under 0.4" and it could be placed over the original gain switch.... what I can see from the pics of the front plate there is enough room ¿?

[agdr]

BlueRob: Good thoughts, but that slider switch is PC board mount style. The switch for the boost would have to be panel mount with a threaded collar and nut.

One thing to watch out for with the B3-080 case - the B2-080 front panels won't fit (not tall enough). There were some B3 panels made during a group buy a few months ago, but I'm not sure if anyone is selling B3 front panels now. The case comes with blank panels though, so you could always drill it yourself if you have a drill press! The measurements RocketScientist gives on his blog for the panel should work as long as you measure from bottom-up.

[coolhead]

Originally Posted by qusp

sure you could bling it up with a mundorf SIO (i'd love to see RS's face) film cap and duelund carbon resistor (zfoil preferred but their advantage has basis in fact) but really it doesnt have to be a huge expensive film, just a panasonic pps, which i love, they are designed for exactly this purpose ie. analogue filters. here is the part i would use for $1.09 each, as its a 0.1uf +/-2% part, you can save 5c by getting the +/-5% or if it has to be a ceramic use an np0/c0g grade MLCC.

the part linked above is a 1210 size, which is pretty manageable, but you could go with a 1913 or even larger at the risk of losing the advantage and it may not be possible to fit the RC across the bottom of the resistor on top, but they turn out to be >30c more. i would go the 2% as this is direct signal path and at that price difference its hard to think of a reason why not.

if you want a bit fatter bass but not more volume of bass, just a wider bandwidth boost ie. you want the boost to include some of the lower mid-bass as well, you can choose a 0.22uf part, or lower cutoff you could use 0.047uf. they are available in through-hole as well, but they are a bit large and i would choose another part like a vishay polypropylene film and foil box cap.

the resistor i would go with is my favorite tight-ish tolerance thin film that doesnt break the bank, the susumu, now 3k0 isnt the most common value but they have one for $0.11 in 0.5% but its only available in 0805 size, which may or may not put some of you off. theres a panasonic 1210 size thin film in 3.3k but thats an odd size and they are 0.1% tolerance so are $1.10. stackpole 1% thin film 1206 size for $0.09 but if you can justify it and 0805 is too small, i would recommend the vishay 3k01 0.1% 25ppm 0.4W for $1.05 which are usually a pretty colour too =)

heres the pps film
its 1210 (3225 Metric) which means 0.126" L x 0.098" W (3.20mm x 2.50mm)

How about Polyethylene Naphthalate capacitor like this LDEDC3100KA5N00 - KEMET - CAPACITOR PEN FILM 0.1UF, 63V | element14 Malaysia in that position? I use to have 2 still seal in a plastic bag.

-coolhead

[BlueRob]

My Bass Boost mod will have to wait....looks like I got a faulty PCB, it seems that the path between R16 and U1 is faulty.

Frustrated!

[BlueRob]

AGDR is there any chance you update and upload the 02 schematic with the 3db bass boost including the switch?

I´m having trouble digesting the overall layout to proceed with this mod.

Thanks in advance!

Rob.

[BlueRob]

[DJNUBZ]

Could you tell me if your amp has better battery life on you 9.6v batteries? If not, did they change performance in any other way?

[agdr]

Originally Posted by DJNUBZ

Could you tell me if your amp has better battery life on you 9.6v batteries? If not, did they change performance in any other way?

I unfortunately haven't run the O2s on batteries enough to have any useful measured runtimes. Runtime would be related to the battery capacity though. The blue Tenergy 8.4Vdc "9V" cells are rated at 250mAhr vs. 230mAhr for the white MaHa 9.6Vdc "9V" cells, so in theory the two should give almost exactly the same runtimes for a given load. Battery mAhr ratings are well known to be inflated on many imported cells (NiMH and Lithium) so either or both battery mAhr ratings could be off in the night though.

The 9.6V cell just gives 9.6V - 8.4V = 1.2V, another single NiMH cell's worth, of voltage swing on each rail, raising the voltage level at which clipping would occur in the two O2 amp stages. For low impedance headphones (32R, 80R), requiring only small voltage swings, either battery voltage is probably fine. But with high impedance (600R, 250R) and low sensitivity cans that need large voltage swings, the extra 1.2V may make all the difference. Even at full charge of around 10.5Vdc that 9.6V(nominal) cell is still 1.5V below the AC rails of +/-12Vdc, which themselves are marginal for some 600R low efficiency cans.

But... that is all just theory. It would be interesting to hear from anyone using the blue "8.4V" Tenergy cells who have actually experienced clipping with the O2 using high impedance headphones. Also anyone who has done some real-world battery run time tests on the O2.

[DJNUBZ]

Considering the O2 is "transparent" is power output the only thing you are going to gain by using higher V batteries? Will it improve the sound at all in any way? I am waiting for some parts for mine so I have no experience with the amp yet.

[sofaspud]

Available gain and/or output voltage swing, yes. I'm not so sure about increased power output.
As agdr stated, that bit of extra voltage swing could possibly improve the sound from certain exotic cans.