I have recently traded for an Amp3. It uses two output inductors (apparently, both "sides" of each channel share one inductor), but has Black Gate caps.
So, what do I do with it?I would like to use the amp in a small aluminum box, with a 14.4v (regulated to 12v) lithium-ion pack and some small portable speakers. (I've been spending a crapload of time on my GC design, and having some environmentally-friendly amp that costs almost nothing to build be my main amplifier would just be humiliating).
I have some 4-pole 12-throw rotary switches ( http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=200042633506&fromMakeTrack=true ) en route, so I figure I'll make up a small ladder attenuator. (3" long, or 2" without the shaft!). Should I use a buffer (op-amp?), or just the passive pre?
Also, what would you reccomend for regulation? It seems counterintuitive to use a regulator AND a battery, but lithium-ion cells are, if you can deal with the risk of explosion, much more convienent than SLA batteries.
So, what do I do with it?I would like to use the amp in a small aluminum box, with a 14.4v (regulated to 12v) lithium-ion pack and some small portable speakers. (I've been spending a crapload of time on my GC design, and having some environmentally-friendly amp that costs almost nothing to build be my main amplifier would just be humiliating).
I have some 4-pole 12-throw rotary switches ( http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=200042633506&fromMakeTrack=true ) en route, so I figure I'll make up a small ladder attenuator. (3" long, or 2" without the shaft!). Should I use a buffer (op-amp?), or just the passive pre?
Also, what would you reccomend for regulation? It seems counterintuitive to use a regulator AND a battery, but lithium-ion cells are, if you can deal with the risk of explosion, much more convienent than SLA batteries.
Hi teapot.
You can actually use the amp3 with a 14.4V rail (14.6V is the absolute max, 14.2V is the max recommended by Tripath), but it will get hotter than usual so be sure to have a good heatsink.
You can use the in your main system while your gainclone is being built
That's what I used it for when I was building my other amps, and it's well broken in. I hope I didn't mislead you to think it has Black Gate caps because it doesn't. It has the standard Panasonic FM supply caps and Panasonic FC input coupling caps. You can easily desolder the small FCs and put in whatever you'd like though. I've never heard Black Gate caps so I can't comment about them, but I have used Auricaps and found them to be very good. There are lots of opinions about what cap is best and it isn't really worth it to get all caught up in figuring out which cap is best. I actually have some small film caps that I used with my Ref-T amp (Tripath TA2021B based) that sounded fine, and I'd be happy to send a couple to you to try with the amp. Let me know if you're interested.
I also prefer linear regulation over a switch mode supply. I should note that my linear supply is just a tad overbuilt, very well filtered, and tightly regulated. A quiet SMPS will most likely sound better than linear supply that isn't well filtered or regulated. I believe that's what most people are hearing and is why they prefer switch mode supplies over linear ones. SMPSs are usually smaller and cheaper too, so those are some plusses.
You can actually use the amp3 with a 14.4V rail (14.6V is the absolute max, 14.2V is the max recommended by Tripath), but it will get hotter than usual so be sure to have a good heatsink.
You can use the in your main system while your gainclone is being built
That's what I used it for when I was building my other amps, and it's well broken in. I hope I didn't mislead you to think it has Black Gate caps because it doesn't. It has the standard Panasonic FM supply caps and Panasonic FC input coupling caps. You can easily desolder the small FCs and put in whatever you'd like though. I've never heard Black Gate caps so I can't comment about them, but I have used Auricaps and found them to be very good. There are lots of opinions about what cap is best and it isn't really worth it to get all caught up in figuring out which cap is best. I actually have some small film caps that I used with my Ref-T amp (Tripath TA2021B based) that sounded fine, and I'd be happy to send a couple to you to try with the amp. Let me know if you're interested.I also prefer linear regulation over a switch mode supply. I should note that my linear supply is just a tad overbuilt, very well filtered, and tightly regulated. A quiet SMPS will most likely sound better than linear supply that isn't well filtered or regulated. I believe that's what most people are hearing and is why they prefer switch mode supplies over linear ones. SMPSs are usually smaller and cheaper too, so those are some plusses.
BWRX said:Hi teapot.
You can use the in your main system while your gainclone is being built
Sorry about the shipping delay. It's getting UPS'd tomorrow. (End of quarter = half-day! Woot!)
You're right - they are Panasonic FC's. (D'oh!) Not necessarily a bad thing, and nice and small to boot.
Out of curiousity, can I just used a stepped attenuator with this amp, or do I need some sort of buffer or preamp with gain? And what values of pot does it "like"?
Finally, I was thinking of using a switching DC-DC regulator to step the 14.4v down to a nice, neat regulated 12v. This is going to be a portable amplifier, and I want to keep it nice and small. (An 8-cell battery pack of the standard-sized "18650" lithium-ion cells will only be about 2.7" x 2.7" x 2.7", and should result in 65 watt-hours of power, enough to run the amp at full blast for an hour.)
A stepped attenuator will work fine. Buffering it would be even better, in my opinion, but it isn't necessary. If you buffer the pot the value doesn't matter as long as your source can handle it.
You can use a DC-DC converter to get 12V but make sure the battery can provide enough input voltage for the DC-DC converter. The voltage will sag over time and can cause the output voltage to drop before the battery is fully drained.
If you think you need to regulate the battery volatge, why not just a standard regulator?
You could build your own circuit - simple - or get a kit like the TREAD regulator kit.
You could build your own circuit - simple - or get a kit like the TREAD regulator kit.
Spasticteapot said:
A switching regulator. But don't worry about it. Any normal "3 leg" linear regulator will be good enough for this use. Any losses in the regulator will be overwhelmed by the draw of the amp itself. A "low drop out" (LDO) type is what you want, because you need a small voltage drop. A 3 amp regulator is a good choice.
If the fresh charge is 16V, then you certainly need the regulator.
BWRX said:
Something like these?
http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&rd=1&item=7590457256&ssPageName=STRK:MEWN:IT
Yes, they look like those caps but aren't as large. Those are larger because they're rated at 250V.
Check out these 50V and 63V rated caps from Epcos:
http://www.epcos.com/inf/20/20/db/fc_05/MKT_B32520_29.pdf
I've used the 2.2uF 63V.
Check out these 50V and 63V rated caps from Epcos:
http://www.epcos.com/inf/20/20/db/fc_05/MKT_B32520_29.pdf
I've used the 2.2uF 63V.
panomaniac said:
http://www.national.com/pf/LM/LM2670.html
This looks pretty sweet. As an added bonus, I can just use five cells in series - assuming I use inexpensive 2200mah cells (about 5$ each), that leaves a reasonable 40 watt-hours. Even if I run the amp at 20 watts per channel (and I doubt I'll be using more than ten), that's still a full hour of battery life.
Another possibly more affordable option is to use an old laptop battery, chock full 'o cells.
http://www.pcsurplusonline.com/viewprod.cfm?ID=6884
I'm pretty sure that it's six cells in three series-wired sets of two in paralell. Efficiency is still pretty good from said regulator even if the batteries were to be wired in series.
Oops! I was thinking of the 5A version.
http://www.national.com/pf/LM/LM2677.html
This should allow a healthy 2.5A @ 12v per channel, for a grand total of 30 watts. So long as I stay below 30 WPC, I should have no trouble.
Just curious, though - what would be causing the clipping with this regulator?
http://www.national.com/pf/LM/LM2677.html
This should allow a healthy 2.5A @ 12v per channel, for a grand total of 30 watts. So long as I stay below 30 WPC, I should have no trouble.
Just curious, though - what would be causing the clipping with this regulator?
Hi SpasticteapotSpasticteapot said:
If believe that this preamp kit will match an Amp3, very well.
Have a look at it. Its very reasonably priced, well cheap really.
Especially as it can be powered by a wall wart. The wall wart can output anywhere from 9V to 17V, have a 17-0 or 17-0-17 configuration, and 300mA/3.6VA (or higher) AC current ... http://www.diyhifi.org/amplifierguru/guru_008.htm
KL
Spasticteapot said:
It ain't the regulator my friend, it's the amp. If the amp is giving you 20 watts per channel, then it's clipping like a mother.
The SMD Tripath chips I've worked with never seem to get any closer than 2V to the rail before clipping. The TA2020 gets within a volt. So you are clipping at about 10V peak with the small chips. You can figure about 12 WPC RMS into 4 ohms before bad clipping. You will probabaly run the amp into clipping, but won't notice it until you push it too far.
So count about 15 WPC into 4 ohms before things really fall apart.
A 3A regulator works just fine in practice. But a 5A won't hurt, especially if you have a 4 ohm load. But don't expect a lot of power out of the AMP3, it just won't do it.
I'll measure one again to be certain, but that's been my experience with a rather large number of T-Amps.
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