peranders said:Good job and the soldering doesn't look so bad.
I think have made the right decision to include a buffer because of the large input bias currents of the TPA6120. With this bufer you can connect any source without having problems with offset voltage.
What supplyvoltage do you use? How hot does the IC get?
soldering would look better if I use liquid flux - I havent any yet...
supply voltage +/- 15V is taken from main PSU on may EP90ES AC3 decoder - in fact this is a headphone amp for this device - LMs produce +/- 11,66V (120Ohm/1kOhm)
chip is quite warm (buffers are hotter) - but so far I didt put much load on it - still testing (ear & osciloscope) - I can say - bass sounds "deeper" than from my STR930 amp...
I use plain 60/40 tin 0.7 mm. Works perfect for me.
An externally hosted image should be here but it was not working when we last tested it.
Indeed, not very hard if you know the tricks and it didn't take so much time other.
Soldering iron
Tweezers. This pair of tweezers is just fantastic, perfect balance
I have two soldering irons when I solder all 0805 parts.
Some day I will descibe my tricks in more detail and with pictures also.
Soldering iron
An externally hosted image should be here but it was not working when we last tested it.
Tweezers. This pair of tweezers is just fantastic, perfect balance
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
I have two soldering irons when I solder all 0805 parts.
Some day I will descibe my tricks in more detail and with pictures also.
OK. Let's see:
1) The solder pen I have: Hako 936. What temperature and tip?
2) The tweezers I have are good but might not be adequate for the job.
3) What is that template? What material?
On one article I read it said that using super-glue to fix the part before soldering it was a good trick. Do you think so?
How to fix the part and the heat are my main worries.
Apparently you need to use solder with some silver on it.
The next thing is how to do my prototype pcbs for SMD, which is not easy.
Carlos
1) The solder pen I have: Hako 936. What temperature and tip?
2) The tweezers I have are good but might not be adequate for the job.
3) What is that template? What material?
On one article I read it said that using super-glue to fix the part before soldering it was a good trick. Do you think so?
How to fix the part and the heat are my main worries.
Apparently you need to use solder with some silver on it.
The next thing is how to do my prototype pcbs for SMD, which is not easy.
Carlos
To put it short:
1 Put tin on both pads.
2 Place the part with a pair of tweezers
3 Take two irons and warm for a second or two. The part sucks into palce. Boom finished.
Version two with only one iron:
1 Put tin on only one pad
2 Place the part and warm the tinned pad and adjust the placement with the tweezer.
3 Solder the other pad.
You don't have to glue the parts.
1 Put tin on both pads.
2 Place the part with a pair of tweezers
3 Take two irons and warm for a second or two. The part sucks into palce. Boom finished.
Version two with only one iron:
1 Put tin on only one pad
2 Place the part and warm the tinned pad and adjust the placement with the tweezer.
3 Solder the other pad.
You don't have to glue the parts.
Upupa Epops said:I have another question ( for good judging of sound is one day too little) : Have you any control of this amp by high speed scope ? I am asking about stability, 'cos in dataseeet is many warnings about this
.
so far no problems with stability (geez I have 14 caps in decoupling ) - I can see 50Hz however when the input floats in the air
Hold on your horses...
...it's gettin' better.
It's been
in'-in for some days.
Today, arriving home, I've been listening and comparing with my pre.
My pre seams more open on the midband and treble, more detailed, smooth but "open".
The TPA was smooth but a little shut-in, lacking some harmonics and directness.
It was better than some days ago, but not convincing.
As I don't trust my test pot, I picked another (better) one I have here for some time and didn't use yet.
It's a log. 10k carbon pot, all metal (including metal shaft), smooth and silent operator and good looking indeed.
I bought some of these some 6 months ago but haven't tried yet.
They were only available in 10k...
I made a passive "pre" in a very small box, with single RCA inputs and outputs.
I've just connected it half an hour ago.
And...
The deam thing oppened up, much more detail, much more "alive".
It doesn't give me sleep now.
Gonna wait some days more, no hurries.
I'm going to be busy the next days, so let it.
This sound now reminds me the best pre I've heard in my life, an unforgivable experience: the Jeff Rowland Coherence.
I still have to try the AD815, I'm just curious. The Jeff Rowland uses this one.
...it's gettin' better.
It's been
in'-in for some days.Today, arriving home, I've been listening and comparing with my pre.
My pre seams more open on the midband and treble, more detailed, smooth but "open".
The TPA was smooth but a little shut-in, lacking some harmonics and directness.
It was better than some days ago, but not convincing.
As I don't trust my test pot, I picked another (better) one I have here for some time and didn't use yet.
It's a log. 10k carbon pot, all metal (including metal shaft), smooth and silent operator and good looking indeed.
I bought some of these some 6 months ago but haven't tried yet.
They were only available in 10k...
I made a passive "pre" in a very small box, with single RCA inputs and outputs.
I've just connected it half an hour ago.
And...
The deam thing oppened up, much more detail, much more "alive".
It doesn't give me sleep now.
Gonna wait some days more, no hurries.
I'm going to be busy the next days, so let it
.This sound now reminds me the best pre I've heard in my life, an unforgivable experience: the Jeff Rowland Coherence.
I still have to try the AD815, I'm just curious. The Jeff Rowland uses this one.
carlosfm said:
Of course.
The evaluation board doesn't have an input buffer.
If you connect a pot there you will have DC.
The source may not have a variable output, you need a pot.
I also don't want to use a buffer because I want to evaluate the chip by itself, to see how it sounds alone.
How did you solve the DC problem - did the 4.02k resistors make a difference, or is there another way without resorting to a buffer?
Also, to use as a pre-amp, is the value of the feedback resistor the only change needed?
I'm making the board for the AD815 now.
This chip has much more logical pinout and allows for a very good layout.
Anyway, comparisons only in the end, I have some more plans.
Meanwhile, here's another "good-looking" current-feedback PowerPad device:
Single:
http://focus.ti.com/docs/prod/folders/print/ths3061.html
Dual:
http://focus.ti.com/docs/prod/folders/print/ths3062.html
Advantage: only 8 pins.
7000 V/us
This chip has much more logical pinout and allows for a very good layout.
Anyway, comparisons only in the end, I have some more plans.
Meanwhile, here's another "good-looking" current-feedback PowerPad device:
Single:
http://focus.ti.com/docs/prod/folders/print/ths3061.html
Dual:
http://focus.ti.com/docs/prod/folders/print/ths3062.html
Advantage: only 8 pins.
7000 V/us
The AD815 is already singin' on my main system.
I could only get my hands on the SMD version.
This thing needs to be properly heatsinked, it gets .
No DC-offset on the input (~0.2mv).
Around 33mv DC on the output.
Starts with around 16mv, and goes slowly increasing to stabilize at around 33mv.
I won't use input caps, here, but maby I will use output caps.
Each current-feedback chip is a different animal...
Gonna let it-in.
I could only get my hands on the SMD version.
This thing needs to be properly heatsinked, it gets
.No DC-offset on the input (~0.2mv).
Around 33mv DC on the output.
Starts with around 16mv, and goes slowly increasing to stabilize at around 33mv.
I won't use input caps, here, but maby I will use output caps.
Each current-feedback chip is a different animal...
Gonna let it
-in.Take it easy, I'm reading some threads...
It's late now, tomorrow when I arrive home I'll take a listen to the AD815.
But real comparisons only in a week or so, I have much to do now.
I'm making some "improvements" in the house, I have no kitchen right now, this seams like camping!
Tomorrow night gotta do some wall painting...
It's late now, tomorrow when I arrive home I'll take a listen to the AD815.
But real comparisons only in a week or so, I have much to do now.
I'm making some "improvements" in the house, I have no kitchen right now, this seams like camping!
Tomorrow night gotta do some wall painting...
After some painting...
This thing seams really special, but some issues still to solve.
To match impedances and lower input/output DC I used 220R from +IN to ground.
But this attenuates the signal too much.
I removed the resistors and I have ~1V at the output.
With a 10k pot connected, I have no DC at low volumes, but it increases with the volume.
Of course, to lower DC to "normal" levels I really need 220R (after the input caps).
I need the gain I have (2.8x), and I can't change the feedback resistor to a much higher value...
I tested signal trafos at the output and 0mv DC.
What's more, these little things cost me pennies and are very transparent, much better than most caps.
I only have two, tomorrow morning gotta go buy some more, if they still have them.
The plan is to make something a la Jeff Rowland Coherence: input and output trafos.
So... out with the input caps, in with the trafos.
Without an input buffer, this seams the most rational approach.
Wait some days, my wife wants the kitchen ready before the pre.
Well... so do I...
This thing seams really special, but some issues still to solve.
To match impedances and lower input/output DC I used 220R from +IN to ground.
But this attenuates the signal too much.
I removed the resistors and I have ~1V at the output.
With a 10k pot connected, I have no DC at low volumes, but it increases with the volume.
Of course, to lower DC to "normal" levels I really need 220R (after the input caps).
I need the gain I have (2.8x), and I can't change the feedback resistor to a much higher value...
I tested signal trafos at the output and
0mv DC.What's more, these little things cost me pennies and are very transparent, much better than most caps.
I only have two, tomorrow morning gotta go buy some more, if they still have them.
The plan is to make something a la Jeff Rowland Coherence: input and output trafos.
So... out with the input caps, in with the trafos.
Without an input buffer, this seams the most rational approach.
Wait some days, my wife wants the kitchen ready before the pre.
Well... so do I...
analog_sa said:
Do you recommend using them only in the input?
I may use caps at the output.
At the input I have around 15mv DC with a 10k pot at max volume. At minimum I have 0.
What type?
Now someone's gonna laugh...
I made tests with some "ground loop isolators" and found some that I can't detect any difference in sound when they are inserted on a circuit.
Curiously, this type I'm talking about is made for car audio and costs... 5.5 Euros.
I bought another one today.
I tested some that cost more than double the price and didn't like.
This thing has no brand, it just says "High quality ground loop isolation", and it's a cylinder. Female RCA inputs, male outputs.
I scavenge it and take the trafos.
You'll have to measure the dc with the secondaries in circuit. It will probably be very low. In any case if you don't notice appreciable reduction in bass the cores are not saturated. Is the pot connected directly to the primaries? This may be less than optimal as at low volume settings the primaries will be seeing higher driving impedance and as these transformers likely have lowish primary inductance there will be less bass and higher distortion at low volumes. Ideally you should drive the primary directly from an opamp output but this effectively means an extra stage.
How big/heavy are the cores?
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