Change in amp is - changing R15 from 75 ohm to 50-46 ohm for increasing charging current from 16mA to 25-27mA. This is closer to C/10 charging formula for 250-280mAh batteries. cj experiments also show - 12V PS must be at least 1-1.5A, 0.5A used in the beginning not work.
Chris, how about your 9.6V batteries? Is it possible to charge with amp's charger?
33% plying time difference between just different opamps looks little unlikely. Probably there is other aspects like different phones, little different volume, even music style (amount of bass). Maybe even battery "break in" or just fuller charge. I don't think on the same load in the same schematic difference between opamps can be too large.
Firstly the 9.6v batts were chargeable with the LED shorted, achieving the same charge as an external charger, though less than the more standard batts as the mAh rating is lower (230 as apposed to 280).
The increase in running time brought by the 2134 opamp was confirmed by going back to LM4562 as run time reverted to as known before.
As for method of charging and playback, I tried to keep both as consistent as possible. i.e. charging was always started at midnight and finished at midday. Test playback was always with the same headphones and the same folder of music always started from the beginning, making load and programme equal.
The only difference was that the 2134 required the volume control to be slightly higher than on the 4562 to achieve the same perceived volume but the 2134 had the longer running time despite that.
All of this is rather mute as the 4562 is allowed to really shows off its superiority in this design.
The LM4562HA offers another flavour again, a shift in tonal balance and I think on balance is down to personal preference.
The likelihood of me needing more than 10 hours playtime in a single day is very remote but if anyone else does exceed this then maybe some 9.6v 300mAh batts would get you there?
Whatever the details, I am very happy with the amp.
Alps volume pot, PanasonicFM 1000uf 35V power and output caps, polypropylene input caps, 1% metal film resistors. At power input is CRC filter, last RC separate for each channel. Inside photo is from previous built with inputs only, in new built are additional RCA pair for lin out, can be used as preamp too.
Small piece of protoboard with two wires are test points for tube biasing. For every new tube need to adjust with trimmers 15V on test points for each channel.
Yes, schematic is about the same (I haven't exactly Bravo/Indeed schematic), just better implementation, better parts, like low ESR Panasonic FM power and output caps, polypropylene input caps. I reed here in forum, cheap amps sound not bad and dying after year or so. My guess is, it is because cheap electrolytic caps near the hot heatsinks. In my amp whole surface of aluminum enclosure act like heatsink, it is warm, but not too much. El caps (105 degrees C, b.t.w.) are in good ventilated space. You know, often in China made cheap and downgraded copy of good things, I go just opposite route make things as best as I can.
Thanks for idea about IRL530, I may try it, however output stage is really powerful already. I use simple 24V 1A SMPS and it work surprisingly good.
I had another little play with the 3x9 amp today as I wanted to try the LM4562HA in it.
It reacts well to this, adding a very noticeable amount dynamism and punch. I also popped in the Sun OPA out of interest, this reacted differently to other amps I've tried it in, here it was delivering some serious wallop. Other parts of the FR were a little recessed and generally it sounded a tad slower but it was a lot of fun! The LM4562HA is the keeper here though.
Apologies that I didn't read the whole thread, but the little boxy (wood?) amp looks very cool, then there's this 3x9. I dread trying to read the whole thread because there are several ugly trolls coming after me with whips in hand, so gotta run.... Oh, does the 3x9 relate to the little wood amp?
The wooden valve hybrid in a desktop mains driven (via adaptor) jobby, the 3x9 is a portable using 3 x PP3s for higher power. It was an experimental design that had a few teething problems but got there in the end. There were only a handful made but I really like mine. I've had the chance to compare it to a Voyager and one of the Neco portables (MKII I think), it was both more authoritative and more detailed than either.
Thanks - I know that a lot of guys don't mention things about their designs that aren't complimentary, but the explanation of the use of better parts and keeping them away from extreme heat was a confidence-builder on that little wood amp.