Would anyone be interested in a relatively high end portable?

[Garbz]

I was just about to add often the motherboards also have filtering on them to supply the PCI bus. The switching supplys will generate noise, and that is something that needs to be filtered. I wouldn't run it into the amp without a highpass filter.

Furthermore, and this really is a weak arguement but just something to consider none the less, just looking at regulated equipment all (that i know of) audiophile equipment (shanling naim electrocompaniet musicfidelity just to name a few) have linear regulation in their power stages. The only ones I can think of for switchers are the consumer grade crapness like yamaha sony pioneer toshiba, and even then toshiba and sony's better equipment is linearly regulated.

What i'm trying to say is that very often we rely on hard measurable evidence to show something can not have an effect such as switching noise in the >50khz band but differences are still audible.

 

[nleahcim]

Just thought I'd drop in and say that a small, high end, low power portable amp would be AWESOME.

I must admit I don't know enough to help out with the analog stuff though...

 

[Jazper]

Quote:

Originally Posted by Garbz What i'm trying to say is that very often we rely on hard measurable evidence to show something can not have an effect such as switching noise in the >50khz band but differences are still audible.

well, based on that, how would you suggest this amp be powered?

 

[peranders]

Interesting thread.

First put up specifications like current consumption, weight, size, performance etc.

Then start to design. Soon you will discover that this is not a trivial task. There are many small things which need to be taken care of. Soon you will also have to compromise, you can't get everything.

Am I boring or what?

 

[Jazper]

Quote:

Originally Posted by peranders Interesting thread. First put up specifications like current consumption, weight, size, performance etc. Then start to design. Soon you will discover that this is not a trivial task. There are many small things which need to be taken care of. Soon you will also have to compromise, you can't get everything. Am I boring or what?

hehe definately boring


well I'm assuming the opamps are only going to draw about 10mA (max) each, and the tpa is going to draw 30mA. Based on that I'm trying to work out a power circuit for it that is useful for at least 10 hours run time.

 

[DaKi][er]

May I suggest trying to run it at a low a voltage as possible here,
the tpa6120 can go down to +/-5V and from playing around here I found that around +/- 5.5-6V was enough to run my ER4P's at more than enough volume you'll ever need before clipping of the amp, though this was on a mint amp here

Getting that as low as you can will help greatly in efficiency, +/-12 or 15v is just wasted power for portables

 

[guzzler]

Incidentally, I've been dabbling with a similar idea recently as well. The switching supply is an absolute must, if portability is the main concern here. I was looking at monolithic types so you just have one component, no need to worry about layout of inductors etc. Follow that with a small CLC filter, and you've got a nice power supply.

Next up, ground channel is run through an LM6171 to provide sufficient current. Discrete diamond buffers are looking ok at the moment, layouts a little tricky around them, especially with board mounted jacks. I've attached a picture of the layout, I'm afraid you'll have to follow it yourself. I've used SOT-23s all over, found some nice 600mW jobs for the driver transistors with high enough gain and current

Regards the current drawn, with 4xAA 2000mAhNiMH batteries and a current draw of, say, 50mA (fairly high), it comes out at around 14hrs, at an efficieny of 80% for the monolithic DC-DC convertors at 12V output (ie, +/-6V, more than enough considering most portable phones will be low impedance, you don't need a particularly large voltage swing).

I'm looking at this on and off, not really put much effort in to it. It's a bit of a luxury as far as I'm concerned. You'll need to use SMDs (0805 or smaller preferably) if you want to get anywhere, and I fully agree with 'killer in that people find SMDs scary because they've never tried them. A pair of sharp tweezers, and small solder will pay dividends in this instance.

Interesting to see how this works out....

g

 

[guzzler]

Meant to add, I also had a look and Li-Ion batteries. Quite interesting, but a little on the pricey side at the moment.

www.varta.com

g

 

[greyhorse]

This was a while ago, but Kevin Gilmore's personal portable amplifier ran off of a Cosel DC-DC (12V=> +/-15V) converter. From what I could tell, post conversion filtering was also very minimal with just a single tantalum capacitor per rail.

 

[Jaypetermen]

Quote:

Originally Posted by Jazper Would anyone be interested in a relatively high end portable?

How would this amp rank in size and quality compared to other DIY portable amps (cMoy, Meta, Pimeta)?

If similar or better then the Pimeta, I would be interested in the high end DIY portable amp.

I recently purchased a cMoy, which has a PCB mounted 10k Volume Control Potentiometers with built-in power switch. Having the power switch included in the Volume Control Potentiometers in a nice touch for a small portable amp. Maybe this could be incorporated? Unfortunately I do not know the vendor, supplier or part number for this pot.

 

[mono]

Quote:

Originally Posted by DaKi][er May I suggest trying to run it at a low a voltage as possible here, the tpa6120 can go down to +/-5V and from playing around here I found that around +/- 5.5-6V was enough to run my ER4P's at more than enough volume you'll ever need before clipping of the amp, though this was on a mint amp here Getting that as low as you can will help greatly in efficiency, +/-12 or 15v is just wasted power for portables

This is very interesting info. Is that +- 5.5-6V figure only with AD8610 or other opamps too?

That puts this within reach with only 5-6 AAA cells, would allow doing without the SMPS, and even with a then-generous 60mA consumption would allow over ~12 hours operation which meets my target of a "day" runtime. 5-6 AAA is still requiring a larger amp than I'd want though BUT considering case availability, the case might not be any larger than if 2 AA were used.

Anyone know of good quality tiny cases that don't waste a lot of space? The extruded Hammonds are pretty wasteful IMO, having the ribbed sides is just unnecessary on such a small thicker-walled metal casing and many of Hammond's smaller plastic cases seem to have a rather poor stud spacing that takes away a lot of available space the smaller the case gets.

Given such poor case options (IMO), I may ultimately just hack out some crude aluminum sheeting soldered together and buffed out. Anyone know if aluminum solder can be anodized, and if so would it come anywhere near matching anodized Al sheeting it joins?

 

[Jazper]

Quote:

Originally Posted by mono This is very interesting info. Is that +- 5.5-6V figure only with AD8610 or other opamps too?

understand that's +- 6 v (12v swing)

 

[Jazper]

Quote:

Originally Posted by Jaypetermen How would this amp rank in size and quality compared to other DIY portable amps (cMoy, Meta, Pimeta)? If similar or better then the Pimeta, I would be interested in the high end DIY portable amp. .

Here's the kicker, I have a dtpakiller amp, and I'd say it's pretty damn good, it's a different type of amp to the m3, but it holds its own against it (without the lushness that is mosfets).

 

[mono]

Quote:

Originally Posted by Jazper understand that's +- 6 v (12v swing)

LOL, I should think about sleeping this month.