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Help to alleviate high volume distortion on cmoy.

post #1 of 17
Thread Starter 

First post!

 

So I finished my first cmoy and it sounds pretty good! When I try it loud (pot about halfway maybe), the bass seems to level out and everything starts to distort. I know it's not the headphones (ATH M50) because they crank as loud with my fiio e5 without distorting. I'm guessing (I have no clue) that it is due to the TLE2426's inability to keep things stable at higher currents? Maybe this is normal...Or maybe something else?

 

Here are some details on my cmoy:

Radio Shack board

OPA2132

Gain of 6

TLE2426 3 pin

Single 470uf PS cap (per tangent's recommendation)

1uf input caps

9V battery powered

bass boost

 

I can't go to 18v due to my enclosure size...I already had to modify the layout to get it all to fit.

 

I know there is the possibility of putting caps on the output of the rail splitter. I have 2 questions about this:

 

1) Will adding 2 220uf caps to the rail splitter's output help with distortion?

 

2) Will it matter if I leave my 470uf cap out in front of the rail splitter (while simultaneously using caps on the output)?

 

Any other ideas?

 

Thanks!

 

post #2 of 17
Quote:
Originally Posted by nutt7 View Post
 

First post!

 

So I finished my first cmoy and it sounds pretty good! When I try it loud (pot about halfway maybe), the bass seems to level out and everything starts to distort. I know it's not the headphones (ATH M50) because they crank as loud with my fiio e5 without distorting. I'm guessing (I have no clue) that it is due to the TLE2426's inability to keep things stable at higher currents? Maybe this is normal...Or maybe something else?

 

Here are some details on my cmoy:

Radio Shack board

OPA2132

Gain of 6

TLE2426 3 pin

Single 470uf PS cap (per tangent's recommendation)

1uf input caps

9V battery powered

bass boost

 

I can't go to 18v due to my enclosure size...I already had to modify the layout to get it all to fit.

 

I know there is the possibility of putting caps on the output of the rail splitter. I have 2 questions about this:

 

1) Will adding 2 220uf caps to the rail splitter's output help with distortion?

 

2) Will it matter if I leave my 470uf cap out in front of the rail splitter (while simultaneously using caps on the output)?

 

Any other ideas?

 

Thanks!

 


If you're using the bass boost, you could simply be clipping the amplifier.  I can send almost any amplifier I have into clipping if a bass boost is used.  It's very easy to do.  Just a thought.

post #3 of 17
Thread Starter 
Thanks. It does it with the bass boost off too. If I turn down the source and turn up the amp, it will have some of that distortion at a lower volume...if that makes sense.
post #4 of 17
Quote:
Originally Posted by nutt7 View Post

Thanks. It does it with the bass boost off too. If I turn down the source and turn up the amp, it will have some of that distortion at a lower volume...if that makes sense.


Well, as I said - it was just a thought.  You may want to try to take some pics and post them, along with the schematic you used (bass boost and TLE are non-standard).  I'm not sure anyone can tell you much with just your description.

post #5 of 17
Thread Starter 
Thanks, I will get some pics soon.
post #6 of 17
Thread Starter 

Ok, so here are some pics of my schematic and board. Pardon the hand drawn pic, I don't know of any programs to use (that are free). Overall I used Tangent's tutorial. On the left of the board is C1 and below it the tle2426. I used a wire to tie down the cap until I get some hot glue. If you can identify R4 (the only laid-flat resistor) I put an insulated jumper under it to feed back to the output of the amp from the bass boost switch. I used a jumper for the bass boost "switch". I think everything else is evident in the pics. If not so evident, let me know I can clarify. Also, any helpful criticism is appreciated. (Sorry, can't post pics yet...can't seem to directly post pics from photobucket either) 

 

http://i48.photobucket.com/albums/f225/nutt7/forums/EB6A446F-24FF-47C1-A2F2-246E628A5A47_zpsyy8ocvol.jpg

 

http://i48.photobucket.com/albums/f225/nutt7/forums/9BA24E60-1376-4FD0-9066-FD202446AAF1_zps4kegvguu.jpg

 

http://i48.photobucket.com/albums/f225/nutt7/forums/397AA80F-AE8B-4905-8020-1D2B516DAF01_zpsfmfyvjik.jpg

 

http://i48.photobucket.com/albums/f225/nutt7/forums/64A818C0-8F90-416C-955E-0D388FA75D8A_zpsx2vgvesq.jpg

 

http://i48.photobucket.com/albums/f225/nutt7/forums/C149D673-78AC-4279-A37E-3CB35DAF9922_zpsmikct3za.jpg

 

http://i48.photobucket.com/albums/f225/nutt7/forums/A655486A-193C-412D-AF1B-1E81C7051E2E_zpsfdgxpmcb.jpg

post #7 of 17

 

Do you have a volt meter?

post #8 of 17
Thread Starter 
Quote:
Originally Posted by Avro_Arrow View Post

Do you have a volt meter?

I do. I did measure dc offset. It's around 3-4mV. With no load, the rails are less than a tenth of a volt off in magnitude. What else can I check?
post #9 of 17

 

Monitor your battery voltage under load.

Monitor the rail splitter...does it try

to pull to one of the  rails when the amp

is distorting?

post #10 of 17

@nutt7 

Your drawn schematic for the power supply is wrong*. 

You are using a TLE2426 on the circuit board, but no schematic of the same is there. 

 

Also, i think it s a power issue.  Are you sure you are using a new battery? and old battery could be the issue. Even though you are sure this is a new one, I would suggest getting another and trying. The thing is, even if it is not fully dead, a not fully used battery can develop and show 9V on its terminals. Where it cannot provide is the current. So even if you have 8.4V on the multimeter with such a battery, it wont be able to deliver the same current a new one can. 

 

Regards

 

Edit: Wrong as in, it does not match the circuit you have built.


Edited by psgarcha92 - 1/31/14 at 10:13am
post #11 of 17
Thread Starter 
Quote:
Originally Posted by psgarcha92 View Post

@nutt7
 
Your drawn schematic for the power supply is wrong*. 
You are using a TLE2426 on the circuit board, but no schematic of the same is there. 

Also, i think it s a power issue.  Are you sure you are using a new battery? and old battery could be the issue. Even though you are sure this is a new one, I would suggest getting another and trying. The thing is, even if it is not fully dead, a not fully used battery can develop and show 9V on its terminals. Where it cannot provide is the current. So even if you have 8.4V on the multimeter with such a battery, it wont be able to deliver the same current a new one can. 

Regards

Edit: Wrong as in, it does not match the circuit you have built.

You are right. v+ to in, v- to common, virtual ground to out. Stressful work day! :/
The battery is new, but has been in a drawer for awhile...I can see what other batteries to try. I will also verify voltage under load.
post #12 of 17
Thread Starter 
So I measured the rails under load. With my m50s, it pulls a tad to the negative rail, -4.2 and 4.1. With my vintage pioneers (8 ohm) it distorts like mad at lower volumes. When I measure then, the rails read about -4.3 and 3.85 as opposed to -4.17 and 4.16 with no load. I also rechecked my dc offset and get 3mV at the left and 0.5mV at the right. Not quite sure what any of this means...whatcha think?
post #13 of 17

 

It's not surprising it distorts at 8 ohms...

 

I don't think there is anything fundamentally wrong with it.

Try adding some capacitance after the rail splitter and see

if that helps.

 

Most of the CMoys I've done had something like 470uF

up to 820uF after the TLE.

post #14 of 17

8 ohms?  Oh my gosh.

post #15 of 17
Thread Starter 
I rigged up an 18v supply and it performed better, especially with the pioneers. The amp handled higher volume better...too bad I don't have enough room for the second battery.

I have a 470uf before the splitter, I have won't have room for more of them...too tall. I can try a pair of 220uF unless you think it's too low.
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