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doobooloo's TPA6120-based balanced headphone amp - Page 7

post #91 of 199
8/22/06 at 6:50am
Thread Starter 
Quote:
Originally Posted by n_maher
I believe that at least one of the amps that I'm building will be a in a larger case
There are no mounting holes on the board - how do you plan to secure the board in a larger enclosure? I came up with a few alternatives myself but would like to know what others are thinking.
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post #92 of 199
8/22/06 at 1:15pm
Quote:
Originally Posted by doobooloo
There are no mounting holes on the board - how do you plan to secure the board in a larger enclosure? I came up with a few alternatives myself but would like to know what others are thinking.
Based on a quick look at the boards it would appear that there is plenty of room at the corners to create mounting holes, especially since I do not plan on board mounting any of the rear panel components. That's where I'm starting anyway, we'll see how it goes during actual construction.

I'll take plenty of pictures.

Nate
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post #93 of 199
8/22/06 at 1:23pm
*sniff sniff*

Smells like the curse is strong within this thread...

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post #94 of 199
8/23/06 at 1:41am
Thread Starter 
Quote:
Originally Posted by n_maher
Based on a quick look at the boards it would appear that there is plenty of room at the corners to create mounting holes, especially since I do not plan on board mounting any of the rear panel components. That's where I'm starting anyway, we'll see how it goes during actual construction.

I'll take plenty of pictures.

Nate
I should have just added some pads for standard 0.1" spacing Molex KK connectors over the current space for all the I/O and power/volume connectors. I actually HAD them in place at a certain point of time and got rid of them. Should have just left them in there...

Holes - I guess I can put them over or overlapping with the component footprint since it's going to be either or... Didn't think of this before.

Anyway - good luck with prototyping everyone... hopefully it works and sounds great on the first try!
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post #95 of 199
8/29/06 at 12:50pm
Quote:
Originally Posted by doobooloo
Anyway - good luck with prototyping everyone... hopefully it works and sounds great on the first try!
Parts ordered! DigiKey/Mouser are definitely out of some of the "stock" parts, here's to hoping that I picked the correct alternates! With a little luck I'll start building this weekend.

Nate
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post #96 of 199
8/29/06 at 9:01pm
My order for the couple of parts I was missing is due to be delivered today according to fedex tracking.. Can't wait!
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post #97 of 199
8/30/06 at 9:29pm
It works!!!

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post #98 of 199
8/30/06 at 9:33pm
Pictures and impressions ASAP!
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post #99 of 199
8/30/06 at 10:43pm
I will try to get some decent pictures very soon.. my camera is crap!
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post #100 of 199
8/30/06 at 11:29pm
Quote:
Originally Posted by Thaddy
Pictures and impressions ASAP!
What are you so anxious about???

Mike,

That's very cool! Any hints or tips you care to pass along to the rest of us? Looking forward to seeing the pics and of course hearing what you think of the balanced drive.

Nate
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post #101 of 199
8/31/06 at 1:36am
I don't really have many tips, I just assembled it, and it worked first time!





I've been listening for a little while now with my grado's. It is easily capable of driving them to insane levels.

One thing I've noticed is that it's very easy to clip the input with a strong signal. If I connect it right to my CD player, it makes the nastiest clicking noise. If I attenuate the signal from the CD player, or use my MP3 player, it's not a problem. The horrible clicking noise seems to lessen when increasing the volume, must be something to do with the digital pot.
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post #102 of 199
8/31/06 at 5:55am
Thread Starter 
Quote:
Originally Posted by mikemacwillie
I don't really have many tips, I just assembled it, and it worked first time!





I've been listening for a little while now with my grado's. It is easily capable of driving them to insane levels.

One thing I've noticed is that it's very easy to clip the input with a strong signal. If I connect it right to my CD player, it makes the nastiest clicking noise. If I attenuate the signal from the CD player, or use my MP3 player, it's not a problem. The horrible clicking noise seems to lessen when increasing the volume, must be something to do with the digital pot.
Awesome to know that it works! What was your specific configuration (gain, opamps, etc.?)

Regarding the clipping - as you pointed out it's an inherent problem with the DS1802 digital pot. Currently it is running at +/- 2.5V - and if the source signal goes beyond that it clips and distorts nastily.

What you can do is have a voltage divider cable (or adapter) for your high signal source - not very convenient, but I don't think there's a simple solution to this given the chip's limitations. I still thought the better sound quality and channel matching of the chip compared to small analog pots was worth the tradeoff (and it's way cooler to begin with).

One thing several people voiced concerns about was if the Alpha rotary switch would actually work well with the DS1802. Any problems so far? (i.e. when rotating fast or slow, does volume go up and down proportionately, etc.?)

Anyway, for more info on the digital pot and it's clipping characteristics check out Pedja Rogic's page on the digital pot: http://www.pedjarogic.com/spot/index.html

Congrats on the successful build - keep the impressions coming please!
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post #103 of 199
8/31/06 at 5:57am
Thread Starter 
Oh, also - are you using your grados in a balanced configuration? If not, are there any sonic differences between the regular and inverted channels?

And if you're using them balanced - how is it different from single ended? (I hope it's better!)

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post #104 of 199
8/31/06 at 6:55am
This thread is useless without pictures!!!
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post #105 of 199
8/31/06 at 8:46am
im really wanting to know what peole think of this project, Iv been following it. so we need pics and impressions!
-greg
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