Heat Dissapation Problem LME49720/OPA1632 Preamp

[alexw88]

Results looks good! I am sure it sounds good as well.

During my testing, I tried with different soundcard output level and soundcard input gain and the result THD would be different.

I did a loopback test to get the best THD setting for my soundcard. What I did is to set the soundcard output level to a few dB lower than the default value, and adjust the soundcard gain so that the THD reach a low value. When you reduce the test signal level, the noise level will increase, but THD will be lowered.

 

[artquake]

to get the best THD setting for my soundcard

Just have a look on this:

An externally hosted image should be here but it was not working when we last tested it.

I made 10 measurments (while increasing the Main output pot and lowering the input pot setting) with 10 different settings with the E-MU0404 by loopback.

Conclusion: The lower the signal volume setting on the input pot, the better the results.

For Info to reading the exceldiagramm :

Pot Markers (looking clockwise)

For X = Marker of  Pot „Line in“ 
For Y = Marker of  Pot „Main Out“

Settings 
Nr.	1	2	3	4	5	6	7	8	9	10	
X  	8	5.8	4	3	2.5	2.2	2	1.5	0.6	-1	
Y	1	2	3	4	5	6.2	7	7.2	8.5	9

What i found very interesting was, that using the setting 6 gives bad results. It's somehow an unstable area of pot setting with this soundcard.

I made more measrements on this issue, and i can say that :
Input settings of 1.7 ... 2.3 and while using an setting of the output volume of approx. 5.7 ... 6.2 should be avoided. I'll check this with arta too.

Anyway Setting 9: 0.6 / 8.5 works best for me ...

Talking about measurement software: Bear in mind that every software while using the same setting of the soundcard (for example with Steinberg cubase, ProTools, Wavelab, arta, and many others don't give the same results ... there are sporadic big differences between them ... but maybe you have knewn this allready.

 

[flshzug]

hi , Artquake , what kind of a remote controlled discrete attenuator you goin to have?

 

[artquake]

I tend on This (1)
or maybee this (2) or maybee this (3) one.

Depends on which gives me best sound and performance ...

(1) I need to assemble that first (hope for best results)
(2) I allready used that in my preamp, (Sounds very good. (Could sell it if somebody wants it - but without DACT CT-4 - only control unit including remote control and steppermotor)
(3) I use actualy this one since one year in my diy tube preamp, it's cheap and worth every cent ... no problems.

artQuake

 

[flshzug]

wow , the first link is very cool indeed, ill look after it thanks for the hint !!

 

[artquake]

This Company did not get good feedback in the past when you search in the net. Not because quality of his products, but because of the handling shipping ...

So check / contact him before you make an order. That, to be sure all products are currently available before you do some purchase. The only problem I had so far was, that 4 out of 5 pcb boards where missing when I recently got he kits… but he sent them later … You need also some great patience until he's answering your mails … But, very good manual indeed. In comparison to the problems other had, mine isn't worth to tell even ... To bear in mind, i currently did not assemble it yet ... but i'm confident it will work well ...

my2cents: The caddock upgrade is definetly to expensive … get them elsewhere and you can buy quite a few more for the equivalent value and matching result will even be better … especially when the usage of the remote is for a balanced operation ...

artQuake