[hopeless]

Quote:

Originally Posted by maddman79 /img/forum/go_quote.gif Sure, you're welcome to test one. I'll pay for your shipping each way. Keep in mind, this prototype is meant to be a drop-in replacement for a dual opamp in SIP-8 package. The driving force behind this project is to upgrade my turntable Down the road, I may build a 4 or 6 layer version in DIP-8 package... majkel and hopeless, would either of you have any interest in testing one? I have enough parts for four. -Brian

That's interesting. Unfortunately the Super Pro has a very small enclosure and at the moment it's the only place where I could try it (aside from my CMOYs).

 

[majkel]

Yes, sounds very promising but it's unstable in my circuit. Unfortunately it might be compensated for lower gains in inverting configuration only. So I'll try it as a headphone amp with a decent DIY PSU and we'll see.

On the other hand OPA211ID gained lots of points in my DAC after rebuilding the headphone amp a bit. It's a tough choice between the OPA228P and the OPA211ID. Probably the latter is more linear and the first unity gain stable op-amp without more or less corrupted imaging. What I mean is that on all compensated op-amps I know there is an effect that correct imaging happens in limited area only. On the extremes, or in the middle, things get flat, or there is an impression of a barrier limiting the soundstage. In the OPA211ID there is none. On a pair of AD797BRZ it is very slight. The OPA Sun v.2 seems to work on it's own rules, bringing something new to the op-amp world - fluent transition between sound sources and feeling of free music flow. I'm not sure it's realistic but at least interesting.

 

[maddman79]

Well, I've successfully built-out my first prototype OPA-E, using surface mount parts. I did a quick test with it in my Auzen X-Fi Prelude 7.1, and it does seem to be working!

I ran it without the ground plane attached, and it seems to exhibit strangled mids and an annoying over-emphasis in the timbre with the highs. I don't have any other discrete opamps to compare this with. But, it seems consistent with majkel's description of the ungrounded OPA-E.

I want to run some more tests with the thing grounded. I also want to throw some caps in there for decoupling.

Pics soon to come...

-Brian

 

[fzman]

Brian,

I've done some DIY stuff recently where the grounding made enormous sonic differences, not just i terms of noise, rf, hum type stuff. Having continuity between all of the ground points in the circuit is not enough.

before you mess with other things, experiment with where things are grounded-- and make sure they are really good connections. star ground wherever possible!!!!!

Prps to you for the surface mouont diy!!!!


Mark


Quote:

Originally Posted by maddman79 /img/forum/go_quote.gif Well, I've successfully built-out my first prototype OPA-E, using surface mount parts. I did a quick test with it in my Auzen X-Fi Prelude 7.1, and it does seem to be working! I ran it without the ground plane attached, and it seems to exhibit strangled mids and an annoying over-emphasis in the timbre with the highs. I don't have any other discrete opamps to compare this with. But, it seems consistent with majkel's description of the ungrounded OPA-E. I want to run some more tests with the thing grounded. I also want to throw some caps in there for decoupling. Pics soon to come... -Brian

 

[maddman79]

Thumbnail:

Full size:
http://img199.imageshack.us/img199/431/opamp027.jpg

 

[maddman79]

Vias make star contact with ground plane. However, positive and negative supplies only have traces at the moment. It's only a 2-layer board after all

After I get all the gremlins out, I'll use either a 4 or 6-layer PCB. That way, my supplies can each have their own plane. I also plan on using 0603 passives, as opposed to the 1206 in the first version. I'm thinking that next time around, I can reduce board size by 50%.

Today, I'll try attaching the ground plane and see if that impacts audio quality.

-Brian

 

[exhausted]

The look of it is great.

Does it sound exactly like the Earth once grounded?

 

[ROBSCIX]

Quote:

Originally Posted by maddman79 /img/forum/go_quote.gif Vias make star contact with ground plane. However, positive and negative supplies only have traces at the moment. It's only a 2-layer board after all After I get all the gremlins out, I'll use either a 4 or 6-layer PCB. That way, my supplies can each have their own plane. I also plan on using 0603 passives, as opposed to the 1206 in the first version. I'm thinking that next time around, I can reduce board size by 50%. Today, I'll try attaching the ground plane and see if that impacts audio quality. -Brian

Wow. I am very impressed. That is some fine work.

 

[maddman79]

I did some quick tests with grounding; and so far, it seems to be helping with that annoying distortion in the high-end timbre.

-Brian

 

[ROBSCIX]

Are you considering turning this into a commerical product?

 

[maddman79]

Quote:

Originally Posted by ROBSCIX /img/forum/go_quote.gif Are you considering turning this into a commerical product?

It wasn't my original intent to make this into a commercial product. But, if people are interested, I'll make extras.

Since I'm planning to make the next revision a 4-layer PCB, it would help me a great deal with reducing costs if I was making more than just what I needed. Plus, it would give me more purchasing power in sourcing parts. Some of these components are really hard to find.

FYI, next version will be DIP-8...

-Brian

 

[ROBSCIX]

Great, well if the test goes good I will take a few off you.

The DIP8 socket seems to still be the most common among a great deal of audio gear.

Given the tools and prices avialable now it is easy to make your own PCB's when you need them.
I can still remembe etching my own PCB's in the basment.

 

[maddman79]

Grounding made a significant difference. I'm anxious for you to review a prototype.

-Brian

 

[ROBSCIX]

Send it over and I will give you my impressions.

 

[n_maher]

maddman, please check your PM's.