[Rocaerix]

OK I decided a few weeks ago I would make a MINT headphone amp. I finished (basically) last night but when I went to test there was a small problem. I had no right channel

.

After much worrying i got out my multimeter (sp?) today and took some measurements. I had no idea what I was doing so i didnt get very far using that method

. However I did manage (somehow) to work out that it was the input connectors fault (I was wrong).

So i connected some alligator clips from the male jack (output) and connected them directly to the input cables bypassing the input connector. I then moved it round on input wires from the left to right channel but they both came out of the left channel no matter wether it was going through left or right input wires. I think the problem MAY be some bridged pads... i'm not sure so I quickly took some pictures:

Amp chip

Left Buffer

Right Buffer

Input solder pads

Output solder pads

Like I said I quickly took the pictures

. This was also one of the first times I have soldered as you can see and I kept stuffing up the Right Buffer before getting thinner solder which explains the flux/scorchmarks near it.

What seems to be the reason for only having left channel?

I can also take more proper pictures if needed.


Thanks
Rocaerix

 

[Rocaerix]

OK please ignore that problem for the moment I think i just worked out my problem

I soldered the wire to the wrong pins on the connector so it was only ever going to output to left channel because right wasn't connected....

Just going to go change pin now

 

[MisterX]

eww.. flux everywhere.

[size=xx-small]CLEAN IT![/size]
[size=x-small]CLEAN IT![/size]
[size=small]CLEAN IT![/size]
[size=medium]CLEAN IT![/size]
[size=large]CLEAN IT![/size]
[size=x-large]CLEAN IT![/size]
[size=xx-large]CLEAN IT![/size]

 

[MisterX]

Sorry, I just have a thing about flux.

 

[Rocaerix]

Quote:

Originally Posted by MisterX Sorry, I just have a thing about flux.

Yeah I intend to clean it tomorrow when i get some alcohol.

OK it all works and got testing with my DT440s

.

I think it may be biasing one headphone with more bass because in Pantera (anything) the singer sounds like he is only from the right unlike usual where its like hes inside my head, also the bass drums sound louder from the left.

Also in Ions by Tool (the thunderstorm one) you can usually here a "charge" go from left ear over your head and terminates in the other ear. Now it goes from left ear (like it should) up to the top of my head then slides down to behind my head.

I think it sounds as though there is more bass on the left....

Any idea how to fix this?


Thanks again
Rocaerix

Back to Testing

 

[Rocaerix]

OK right channel is fine from what I can tell.

More examples of the previous problem.

The left channel however seems very "echoy" for vocals, doesn't do bass at all really (Forty Six & 2 can only hear guitar from left no bass guitar at all really). I think this is the same cause but this screws over everything especially soundstage.

I cannot hear the solo from Floods (Pantera) in the left channel (the really high pitch part) also the drums can only be heard from the right (toms I think) during the regular pitch part. There is also a part in Domination (also Pantera) where it alternates totally (seems like it) from left to right and back again over and over; it seems like it goes from left to behind centre instead of left to right.

Still can only hear singer from Pantera from right (highish pitch voice) in some songs and Ions still doesn't go over my head properly. I am really bad at explaining but I hope you guys can get what I mean.

Any Idea how I could fix this?

Thanks.

 

[Pars]

Clean the board, as so eloquently pointed out by MisterX

.

Then, take a magnifying glass and look EVERYTHING over for bridges, bad solder joints, etc. Recheck ALL connections.

 

[tangent]

Quote:

The left channel however seems very "echoy" for vocals,

That indicates more connection problems. The "echoes" are part of the stereo information, which you're missing due to the bad connections.

Step back and work out the proper pinout of your jacks before doing anything else. From what I can tell, you've just been guessing. Stop guessing and find out!

Desolder one of the jacks from the wires, if you don't have a spare. Then take a mini-to-mini cable, plug it into the jack, and measure ohms to find out which contact on the end of the cable goes to which lug on the jack. (You'll get 0 ohms or near to it when you have found the right path.) The "tip" of the plug is the left channel, the "ring" is right, and the long "sleeve" is the ground. (These are called TRS plugs for reasons that should now be obvious.)

 

[leftbldg]

If your jack is a Switchcraft 3.5mm, its schematic is probably here:
Switchcraft mini pdf
But do as tangent suggests and you can't go wrong.

BTW tangent, I'm about to start building a MINT now--what are the small through-holes near the BUF and OPA pads, and also near R4 on one of the channels--test points? I scoured your MINT guide but didn't find an explanation. Thanks.

 

[tangent]

Quote:

what are the small through-holes

Vias.

 

[Rocaerix]

Quote:

Originally Posted by tangent That indicates more connection problems. The "echoes" are part of the stereo information, which you're missing due to the bad connections. Step back and work out the proper pinout of your jacks before doing anything else. From what I can tell, you've just been guessing. Stop guessing and find out! Desolder one of the jacks from the wires, if you don't have a spare. Then take a mini-to-mini cable, plug it into the jack, and measure ohms to find out which contact on the end of the cable goes to which lug on the jack. (You'll get 0 ohms or near to it when you have found the right path.) The "tip" of the plug is the left channel, the "ring" is right, and the long "sleeve" is the ground. (These are called TRS plugs for reasons that should now be obvious.)

I found out and resoldered them last night. I checked with the multimeter with one on the ground one on what I knew was the left channel and the mV jumped around like they had from other connectors. I then connected it to ground and then to what i thought was right channel (oringinal problem) and it had nothing but then i did it to the connector next to it and it was jumping around like the working one was.

Going to clean the board today and fix up all joins.

 

[Rocaerix]

Cleaned up PCB, added more solder where needed, etc.

After more testing I think I have narrowed down the problem but it is kind of confusing. I decided to check what was happening with the channels to when I was testing my interconnect and other cables.

I set it to left- Sound Comes out left like mono perfect

I set it to stereo - Came out of both wierd like I had listed above except the soundstage doesn't sound right; some things only come out on the right, other things sounds louder from the left.

I set it to right- This is the wierd one. I set it to right and it comes out of both channels but its mono; but sound is good, no soundstage though.

So to sum it up as stereo some things (vocals mainly) only come out on right but other things (such as deeper drums) are more on the left but this may just be due to a lack of focals. Things that are on the left sound like they are on the left, but deep things that are on the right seem as though they come from the middle unless and higher pitch things from the middle seem as though they are coming from the right...

EDIT: channels edited using Winamp 5 EQ (usually use Foobar but couldn't find how to change channels using it)

 

[MisterX]

Care to post some new picts?
Hopefully of the whole thing....... that way we can see how your jacks are connected.

 

[Rocaerix]

OK got some more pictures; higher res as well.

Top of the PCB
Top of the PCB again
Input Connector
Output Connector
Bottom of the PCB
Bottom of the PCB again

As you can see I screwed up a bit on connectors and melted bits of plastic because I ould be able to solder and the connector ould roll over

.

 

[Earwax]

If I'm intrepeting those images correctly, you need to check the output jack wiring. It looks like at the board end, you used green for ground, yet on the jack itself, the green wire isn't connected to ground. (the ground lug is the one nearest the threaded part) But with the heatshrink, I can't see all that's going on at that jack.

and the link is misspelled in your post, it should be output jack