iBasso OEM Project - Page 2

Discrete calls for more implementation area to make fine sound.
Simply buffers with 2SD882/2SB772 in P2 can't give us enough sound resolution, I think.
Therefore, the new P3 have buffer sockets to use 634s (I heard).

A feature of our amp is selectability of parts.
We want to change OPAMPs, CAPs, GAIN....etc

http://photo4.avi.jp/photo/7/396928/...-140049-pc.jpg
For instance, I suggested them to adopt this pattern under buffers.
Not to use only 634s, also followers (can be parallel-connected).

As default, one 634 will be loaded on each channel DIP8-socket.
Additionally I asked them to give Single/Dual-OPAMP compatibility to our amps like SM4s.

Just for our/your favorite sounds.....

Will P3 have no charging circuit? hmm...

Ok, but a socket for a resistor to bias the buffer also? Sockets to change caps, which would be easy to do as long as someone doesn't reverse polarity if using polar caps. Half the amp could be sockets but then you have a problem with correct operating points and the circuit being stable. More implementation and experiementing. The D1 case (size) without the dac section would all for more movement of parts but it could also get complicated. Sometimes the keeping it simple is the best for use and sound. High quality DC and a direct simple path.

Oh, you want some dynamic good sound? Use some small inductors on the opamps. You now have a better voltage and current demand being met.

As an alternative idea for power, how about a 18650 lithium ion battery (3.7V @ ~2600mAh) that can be either charged in the unit, or swapped out for a cell that was charged in an external charger.

These give you the benefits of lithium ion in terms of power density and good recharging characteristics in a nice 'cell' style form factor and reasonable cost for the user.

The key thing would be to make sure the battery door is sturdy enough and easy to operate.

Optimally the unit would employ a USB connection for in-unit charging. This would give a lot of flexibility. Personally I have been trying to standardize my charging capabilities, with USB power sources for the car, wall outlet and even battery backup. This provides a standard power system that can power both my iPod and my phone.

If needed, a DC to DC converter could be employed.

Personally (while I have a iBasso P2), I'd like to see a future version based on something like the D1 to add SPDIF and USB input.

Here is a (cheezy) photo picturing an 18650, AA and 123A cells, with iBasso P2 and charger.

-john


[FULL SIZE]

>jamato8
Resistor value for 634's WB-mode (btw 1-4 pin) is going to be 470 ohms. If need, you have to re-solder it.
And we don't consider sockets for caps. Because not to err polarity like you concern about.
Because this amp's concept is for mod-lovers who has techniques to solder.

To make room for choosing fine parts, I suggested them to use D1's enclosure.
I love simple circuit like P2 and agreeing to you. Then base of this circuit is P2's.
But, obtaining high quality DC doesn't mean omitting circuit to charge.
Actually P2 uses charge pump to raise voltage for supplying 8.2V, but giving slightly ripples too.
We wanna obtain high quality stabilized DC with using FINE & LARGE-VALUE CAPs (as I mod & gave 6600uF to my P2).
The reason for necessity of charging unit, we hate troublesome swapping 6 AAAs (as P3 will be).
And we need to easily recover short-standability by using 634s (connecting charger makes it easier).

>ccfoodog
But this amp I suggest requires more than 18V to charge.
USB-input is lower than it.
I proposed them to test with using 400mAh powerizer 006Ps in series.
The 18650 cells make this amp more expensive....(requires 4 at least)

Socketed caps isn't something I would do but since you were going over details of socketing I thought it was something that was being considered.

You should also ask for much larger than normal value for the wattage of the resistors as this will sound better. I would put in as large a wattage resistor that will fit. I would also explore the different resistors available. There are some carbon surface mount. Sure there are some nice caps made now. The Panasonic FC series is very good as are some others.

I don't like swapping batteries either.

Socketing point for OPAMPs will be 2 for Dual-OPAMPs (L/R, GND) same as P2's,
and maybe added 2 more for Single-OPAMPs (in L/R section).
For buffers, 3 points (L, R, and GND) with pattern I mentioned.

About higher wattage resistor, that's interesting for me.
I'll suggest it to them.

Caps, I'll adopt UTSJ's 4700uF/16V as default.
http://www.toshinkk.co.jp/goods/sound/pdf/UTSJ.pdf

You can choose and load 16mm diameter cap as one's favorite.
Like Blackgates, Silmics, Muses, OS-Cons, and Panasonic's....

Sure there are many nice caps depending upon a person's desire. The resistors are something they know about as I have mentioned it to them and they used larger values in the Boa, which worked well for its sound quality. I would go as large as possible. I stress this because I have experimented with it for a number of years and even using a 2 watt when 1/8 watt is all that is needed yields better results. I realize that size would not fit in amp you are talking about but large caps (edit: Resistors not caps) would work in the signal path when found there.

I confirmed them about your proposal.
They'll accept it and already understood.

http://photo4.avi.jp/photo/7/396928/...-140133-pc.jpg

Pattern for single/dual OPAMPs in L/R section.

Very nice. Should be interesting.

Are you getting in on this Jam?

BTW, here is a thought I had. I do not know much about amp design, but what about integrating a switch that would allow the end user to by-pass the internal battery and power it with a wall-wart? It would make it more of a true home/transportable hybrid.

Are you requiring accessability for swapping 006Ps?

I am not sure what that means Like I said, I do not know what changes my suggestion would detail. I do know that to my ears, it seems that the biggest difference with portable versus home amps is the power supply. A constant larger power supply means things can be biased into class A and and not have to worry about battery size and battery life.

It isn't just power supply but how the power is used. You can run off of the battery, a fairly pure DC source and get excellent home sound. It is all about implementation. The Woo 6 is a home amp but I showed and have proved how implementing a good change in the power supply totally changed the amp. It can be done with a battery supply in the OEM being discussed. A wall wart isn't really a good source of power, imo.