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HE-500, LCD2, D5000, DT770, SR80, on a speaker amp (Emotiva mini-X A-100) Project - Page 219

post #3271 of 3639
Quote:
Originally Posted by daerron View Post
 

 

Exactly. I would like to pair the Mini-X with something like an Emotiva DC-1 using the volume controls on the DAC. Second prize would be to upgrade the circuit on the preamp to have a cleaner output.


Oh! I do like where your heads at... That is a good thought. Hmmm.... I know it SOUNDS crazy, BUT I was actually thinking of emailing Emotiva and asking for the schematic for the mini-X. I have been surprised in the past and some companies just dont care because they know how much MORE work would be involved in "copying" a product and they have given them to me. Maybe give them a try and see what they say. Worst case, you might learn a really nice way to say "no". :)

post #3272 of 3639
Quote:
Originally Posted by daerron View Post
 

Okay, so I kind of knackered my Mini-X this evening and stripped the bugger open. I'm still amazed that they are able to assemble this bit of kit for the price. Unfortunately you can see where some corners were cut with the build quality.

 

The preamp and power amp is connected via wire connectors. I tried bypassing the preamp circuit by hooking up the input directly to the power amplifier section, but it also appears to bypass the startup protection circuit, resulting in a disconcerting popping noise. I had an external preamp hooked up to the Mini-X. The popping noise wouldbe very dangerous to headphones and fortunately my cheap guinea pig speakers didn't seem to have come to any harm, but not going to try that again.

 

Going to explore options to see whether I can bypass the volume pot in the preamp circuit. Has anyone considered replacing the TL072CP on the preamp board with a TLE2072? Should result in a nice upgrade in sound quality without too much effort? The preamp circuit is definitely cheap as chips...

 

Good lord, I did not notice that.  TL072 is from like 1978, could they go any cheaper?  I'm going to have to roll in dual OPA627AUs or maybe some LME49990MAs.

post #3273 of 3639
Quote:
Originally Posted by blasjw View Post
 

 

Good lord, I did not notice that.  TL072 is from like 1978, could they go any cheaper?  I'm going to have to roll in dual OPA627AUs or maybe some LME49990MAs.

Or even OPA227 series should work too.

post #3274 of 3639

Putting in a pair of 627's is almost a third of the cost of the entire amp :blink:

post #3275 of 3639
Quote:
Originally Posted by Armaegis View Post
 

Putting in a pair of 627's is almost a third of the cost of the entire amp :blink:

 

Good point, I did not realize they were that expensive.  Heck, you could probably get a Muses01 or even 02 off of Ebay for less.

post #3276 of 3639

The opamp circuit is basic unity-gain buffer with an impedance matching circuit. The negative input and output are directly coupled which I'm not sure how many other opamps would like. I'd definitely be careful with bi-polar opamps and stick to JFET input opamps.

 

I tried swapping in the OPA2134 but it didn't work, it probably needs resistors in the feedback loop, but that means cutting tracks on the PCB. If I had an oscilloscope handy it would have been interesting to see what it was doing, but all I was hearing was just noise. At this stage I was worried that I damaged the amplifier by bypassing the volume pot, but soldering the TL072 back in fortunately fixed it immediately, so the amp is still fine.

 

So not much to show after taking the amp apart! Welcome to some other suggestions, I'm sure the audio quality could be improved by getting rid of that TL072.


Edited by daerron - 2/22/14 at 10:50am
post #3277 of 3639
You could alter the gain a little..?
post #3278 of 3639

Anyone using bookshelf or more desktop oriented with these? Any pairing that doesn't sound bright?

post #3279 of 3639
Quote:
Originally Posted by Zoom25 View Post
 

Anyone using bookshelf or more desktop oriented with these? Any pairing that doesn't sound bright?


I am listening to a pair of Definitive Technology ProMonitor 1000's with my mini-X right now as I type this. Certainly not bright.

post #3280 of 3639

I have this Stax adapter box connected to my mini-x in parallel with my headphones.. It's like 9-10 ohm impedance when 'earspeakers' turned on, around 320 kilo ohm when 'speakers' turned on. Just want to share that I can't hear any difference between the 'speakers' on or 'earspeakers' on per se. Even tried turning on/off while playing music. Not that I expected to hear a difference either..

post #3281 of 3639

Selling my Mini-x. Thought of letting you guys know in advance to give people that I know from here the first chance over regular forum folks. Also saves me time from putting up an ad. Anyways, if you're in GTA and want to save money on perfect condition mini, you know who to contact.;) 

 

EDIT: It's up


Edited by Zoom25 - 2/25/14 at 10:55am
post #3282 of 3639
Has anyone used a decent AVR in comparison to the emotiva mini-x? Just wondering if a dedicated amp would have much advantage over a home theater reciever in sq on headphones. I'm using a Yamaha RX-V373 which is one of the best sub-500 avr's available (excluding vintage). Sounds great with my he-400, hd700, and he-500 through speaker taps with absolutely no hiss on any, including the hd700. Just curious if anyone has any experiance comparing simiar avr's with the emotiva?
post #3283 of 3639
Quote:
Originally Posted by kernel8888 View Post

Has anyone used a decent AVR in comparison to the emotiva mini-x? Just wondering if a dedicated amp would have much advantage over a home theater reciever in sq on headphones. I'm using a Yamaha RX-V373 which is one of the best sub-500 avr's available (excluding vintage). Sounds great with my he-400, hd700, and he-500 through speaker taps with absolutely no hiss on any, including the hd700. Just curious if anyone has any experiance comparing simiar avr's with the emotiva?

I used my Denon 3300 with the LCD-2 and this AVR is hissy, noisy, and thin sounding compared to the Mini-X.  

post #3284 of 3639
Quote:
Originally Posted by kernel8888 View Post

Has anyone used a decent AVR in comparison to the emotiva mini-x? Just wondering if a dedicated amp would have much advantage over a home theater reciever in sq on headphones. I'm using a Yamaha RX-V373 which is one of the best sub-500 avr's available (excluding vintage). Sounds great with my he-400, hd700, and he-500 through speaker taps with absolutely no hiss on any, including the hd700. Just curious if anyone has any experiance comparing simiar avr's with the emotiva?


I prefer dedicated setups personally. But as it is there are a million headphones amps out there and adding to that query a million more AVRs youre pickings get quite slim.

post #3285 of 3639
I've used a demon avr2808ci and it sounds great. Somewhat warm sound.
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