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DIY amp full kit recommendations: <$120, max 60 watts per channel - Page 2

post #16 of 22
Thread Starter 
But with this particular dac, i still need line stage volume control unless I want to set every individual application to -24db gain.
post #17 of 22

'Later Windoz'? Which versions are those?

 

I have a couple of unused installations of XP, I shan't be buying any 'later Windoz' if I can possibly avoid it. Then there's a Raspberry Pi coming.  

 

Given the variety of Windows versions and the difficulty of being sure exactly what processing is taking place before the DAC, I prefer to leave the OS volume controls set to maximum and deal with any level control externally.

 

It's a simple, low-effort (no-effort) procedure that leaves no room for lingering doubts.

 

Maybe I'll think differently when Windoz goes open source.

 

Even with a mixer in between the soundcard and the amp (with it's own volume control) hiss is inaudible. You can adjust the controls so that it becomes audible, but why would you do that?

 

Digital volume control may, in theory, leave any analog control in the dust, but inaudible is inaudible is inaudible. Unicorns notwithstanding.

 

w

post #18 of 22
Quote:
Originally Posted by shrimants View Post

But with this particular dac, i still need line stage volume control unless I want to set every individual application to -24db gain.

thats unusual, consumer audio DAC are mostly 2 Vrms, its a rare high sensitivity power amp that clips on 500 mVrms input - only 12 dB - you can use fixed R dividers if you don't want to/can't fix the system gain structure in the amps or DAC


Edited by jcx - 6/16/12 at 11:55am
post #19 of 22
Thread Starter 
I feel like fixed R dividers are the simplest and cheapest way to go, but isnt that like saying "i want my headphones to have higher impedance so i'm just going to shove a resistor in the signal path"? I dont think that is the right way to go about fixing this problem. Then again, it is a passive component and i dont think it does anything. Plus, if I dont stick my headphones directly into it, im still only dealing with DAC output impedance going into amp input impedance (infinite), so i guess that shouldnt make a huge change. Only problem is, there is 0 possibility for volume control and that completely and utterly defeats the purpose of the entire exercise. I'd have to make a trip aroudn the room and level match everything or i'd have to stick to lowering application volume.

Can someone comment on the multi-CMOY array with unity gain or a gain of 2 idea? I feel like that might be a winner, and sounds kind of fun to boot. Especially if i manage to source my parts from a single supplier and dont go crazy with the opamps.
post #20 of 22
Thread Starter 
UPDATE:

I borrowed the preamp/stereo poweramp combo from my gf's dad today. it is a Toshiba C15 preamp with a Toshiba M15 power amp. About 40 watts per channel. It has 2 pre-outs, so it should work perfectly fine for everything. I will go preamp outputs to power amp and to active speakers, and probably the other output from DAC directly to subwoofer, as it will preserve the most low end and the subwoofer is the least difficult to control in terms of volume. I'll probably post a thing up later asking for advice on it too to see what people think.

I also figured that there were basically 2 ways to go about this. In summary, i could either get a receiver with a power amp built in, or I could get a power amp for now and build myself a preamp. Either way it will cost me about 250 bucks, so while I have this thing i'm just going to use it until I save up about 250 and then buy the dang 5.1 receiver with a single pre-out and sub out. It will give me the most flexibility in future upgrades too and if I HAVE to spend that money, i'd rather do it there and get a warrantied product (possibly for free for my birthday) than to build something that only kind of sort of works.

However, i'm still pretty interested in building a single CMOY with a constant wall power supply. The audioengines need some kind of headphone amp before them in order to control sound, and I figure the CMOY with a gain of 1 or 2 is the best bet to do this. That way I can easily dial down line level voltages while keeping the audioengine's built in power amp at 50% or so, maximum efficiency according to audioengine themselves.
post #21 of 22


Do you think you could buy the pre/power amp off of him?

Quote:
Originally Posted by shrimants View Post

However, i'm still pretty interested in building a single CMOY with a constant wall power supply. The audioengines need some kind of headphone amp before them in order to control sound, and I figure the CMOY with a gain of 1 or 2 is the best bet to do this. That way I can easily dial down line level voltages while keeping the audioengine's built in power amp at 50% or so, maximum efficiency according to audioengine themselves.

If you do this, you should build the feedback loop so the gain is as close to 1 as possible. And check the input sensitivity of Audioengines, you don't want to destroy them by double amping the line signal.

post #22 of 22
Thread Starter 
I cant buy the pre/power amp off of him because it is technically his mom's equipment. He has a ton of garage/barn space so he kept it for her and she "upgraded" to a bose system anyways. However, she randomly calls now and again and says "hey, do you still have my XYZ" and technically this wasnt his property to let him let me borrow. I went through and cleaned the crap out of it though and it works PERFECTLY.

It controls the audioengines' volume absolutely brilliantly. They are at just about exactly 50% right now. The subwoofer needed a tiny bit of a boost, it is past the 50% gain mark, but that is OK. I might need to tweak the crossover setting on the sub a bit because there are places where the HPM's woofers do a fine and dandy job of hitting notes, and I dont need the sub to interject at those frequencies. I might need to play with some damping material panels here and there to take care of a bit of sibilance/harshness issues, but it doesnt get too bad unless you accidentally walk RIGHT in front of the tweeters on the HPMs.

It turns out the audioengines dont need the CMOY thingy at all, and with the preamp at about 20-30% volume and A5's at just short of 50%, everything is just about perfectly volume matched, if just a tad bit bass heavy.

There is no stereo image to speak of, but that is to be expected considering my room is 10x10 and doesnt have any sort of room for such huge speakers anyways lol.

When I get done with these other purchases, I think a proper pioneer 5.1 receiver or something will be the best route to take. Depending on how long i can borrow this pre/amp I might be able to spend a bit more than 250 on the receiver and eliminate some wires here or there. I'm considering an el-cheapo sound card like the Xonar DG or something just for the sake of optical or coax output going to the gamma 2, which I can then feed into the receiver's AUX. The amp itself in the receiver is not something i'm terribly worried or finicky about, as my budget constraints and speakers dont really call for that kind of precision. If I had a set of B&W 800 diamonds though i'd be pretty concerned with the amp i'd be using lol.

Ive made a note about the cmoy thing though. I might let my GF keep the audioengiens at her dorm, and she'll DEFINITELY need something like that to control the volume if she uses them, assuming she uses proper optical or digital output to a DAC of some sort. I'll let her use them out of vanilla headphone output initially just so that when she gets a DAC like the Fiio D3 or D5 she will literaly be able to taste the difference.
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