OPA549 Gainclone Layout

[n00beR]

Thanks for the advice, and the eagle files Alcaid

Now its time to look at the preamp

 

[Alcaid]

Alcaid

on the datasheet(Open-loop gain and phase vs frequency)It looks like for a gain of 30 its flat up to 60k is that right?

Nope.
The y-scale on that diagram is dB gain, so a voltage gain of 30 = approx. 29.4 dB gain. If you see in the diagram the x-scale is logarithmic, which means it's flat up to about 27k or there about. (The log scale is weird in the diagram)

edit:
Used SplTrace to get a more accurate reading. Voltage gain of 30 gives approx 30k freq. With the recommended 1k-10k combo which gives a voltage gain of 11, the freq. is 100k.

Some here at the forum has said the graph is even worse in real life. (don't remember who)

 

[jaudio]

Ok For a 26db gain frequency is flat to about 42k?

 

[Alcaid]

Ok For a 26db gain frequency is flat to about 42k?

SplTrace tells me it's then flat to 50k. It's hard to read accurate this diagram without "cheating" with SplTrace.
26dB gain = 20 voltage gain

 

[jaudio]

If its not to much trouble,what gain would I need to get me to 80k


Thanks

 

[Alcaid]

According to my calculations, you'd reach 80k with a voltage gain of 13. --> 1k and 12k resistors.

 

[jaudio]

Again Thanks alot

 

[Alcaid]

Glad to help.

 

[n00beR]

Lets us know how they look and sound once your trasnformer arrives

Keep up the good work Alcaid.

 

[sidd_raj2002]

hey i am a hobbyist i have the opa549. could u please send me a pcb layout diagram in black and white (jpg) and also the parts list and part names.

i am an extreme amateur i cant design my own circuits yet.

can u also tell me the specs of the is circuit

 

[Alcaid]

Lets us know how they look and sound once your trasnformer arrives

Keep up the good work Alcaid.

Well, the trafo arrived, and I've been listening to it for a couple of days.... SWEET! Love the sound of the amp+pre combo.

Onkyo amp for sale

 

[n00beR]

Any pics yet, glad you are enjoying your amp

 

[soundNERD]

also the gain is too high for the OPA549.
You have a voltage gain of (22/1+1=) 23.
Try something like 11. (1k and 10k resistors.)

I've been reading this post, and want to build a 549 amp. I don't know why the gain matters though. Why can't I use a 22k resistor to not have a need for a preamp?

If I can't use the 22k resistor, I don't have a 10k resistor. I do have a 22k and a 1.8k or a 2.2k resistor. That would make either a gain of 13.2 or 11. Will that be the same as using a 10k and a 1k?

 

[jleaman]

I've made a opa627 + buf634 pre, and I made it like this:
(The giant pot is a Noble, and the spacing around the BUF634 is because of the clip-on heatsink.)

Can i have this layout and Schematic please ?

 

[steenoe]

Alcaid, is there any chance you could post your pcb layouts to scale and in black&white?
That would be cool Great work.

Steen.

 

[Alcaid]

I've been reading this post, and want to build a 549 amp. I don't know why the gain matters though. Why can't I use a 22k resistor to not have a need for a preamp?

If I can't use the 22k resistor, I don't have a 10k resistor. I do have a 22k and a 1.8k or a 2.2k resistor. That would make either a gain of 13.2 or 11. Will that be the same as using a 10k and a 1k?

If you use a higher gain the frequency response would roll off too early, and you would loose the top, and also people reports distortion in the midrange as a result.

I would use the 2k2 - 22k combo.

Can i have this layout and Schematic please ?

Attached the Eagle files. Enjoy!

 

[Alcaid]

Alcaid, is there any chance you could post your pcb layouts to scale and in black&white?
That would be cool Great work.

Steen.

OPA549 amps or the pre?

 

[Alcaid]

pdf files of the pre.

I made the top layer by just taping the layer before etching and used a 4mm drillbit to isolate the pins NOT going to the ground plane.

 

[Alcaid]

bottom layer

 

[Alcaid]

top layer