This is another listening test (I hope your not all getting bored with these 🙂) and this is one where I would really value all your input. These particular tests are very applicable to the kind of small signal circuits we all build. I have another test too, that is perhaps even more applicable and I will post that one a little later. (Test now live and running HERE)
As before, just listen and see if you can tell any difference, and if you can perhaps try and describe what you hear. As you all got me into using foobar, well it would be great to see your results.
These are named after mountain ranges,
ATLAS
CASCADE
As before, just listen and see if you can tell any difference, and if you can perhaps try and describe what you hear. As you all got me into using foobar, well it would be great to see your results.
These are named after mountain ranges,
ATLAS
CASCADE
Should i describe the difference in this thread (without saying which is which)? I have just listened one file but i think i know because it is far below standard (the other one i believe will sound much better)
Interest seems to have waned somewhat so these are details of the two files,
ATLAS, was the LT1229 current feedback opamp dropped into Doug Selfs "Precision Preamp" tone control. The controls were centred first using a scope and generator to ensure flat response. Not all the opamps were replaced, just two key one that are 100% in the signal path with the controls flat (two because I have an inverting buffer to correct the 180 degree inversion the control produces)
CASCADE, was direct.
I have learnt much from all these tests, not least how to produce fairly decent files, and I suspect these were not two of the best because of the levels presented to the A/D convertor.
And thanks to all that have taken part in all of the recent tests... much has been learnt.
ATLAS, was the LT1229 current feedback opamp dropped into Doug Selfs "Precision Preamp" tone control. The controls were centred first using a scope and generator to ensure flat response. Not all the opamps were replaced, just two key one that are 100% in the signal path with the controls flat (two because I have an inverting buffer to correct the 180 degree inversion the control produces)
CASCADE, was direct.
I have learnt much from all these tests, not least how to produce fairly decent files, and I suspect these were not two of the best because of the levels presented to the A/D convertor.
And thanks to all that have taken part in all of the recent tests... much has been learnt.
Wow no wonder atlas was so terrible. I have tried many preamps and still cannot accep any. Opamps are even worse! Same with blameless stuff 😀
It seems dozens of opamps cannot justify another extra one? May be those good recordings that I like used no opamp? Some people like John Curl have done it I believe. BTW, why I have no info about recordings that are done without opamp?
Whats the conclusion? Just stumbled upon this, and spoilers ��
Is the conclusion that tone controls are bad? Just Self's circuit? Or current FB Opamps in these types of things?
Edit: I always preferred Scotch ��
Re-record, don't fade away
Is the conclusion that tone controls are bad? Just Self's circuit? Or current FB Opamps in these types of things?
Edit: I always preferred Scotch ��
Re-record, don't fade away
Last edited:
In term of fatigue, this atlas is the worst from all other test files. May be different opamps will be better/suitable but will not be much. Even Pavel's green was considered (by me) having HUGE difference with direct in fatigue. Just try another opamps, I believe I will prefer OPA2134 again like orange in the fruit test.
I have the highest praise for Dougs circuit tbh. As designed there is just one inverting opamp in the audio path when the controls are centred. I've been curious regarding the CFB opamps and their suitability to audio and still think they could have something to offer in the right application... this perhaps wasn't it, at least not without a serious redesign.
Not necessarily. A tone stage like Dougs precision preamp would be very complex going down the discrete route and not guaranteed to be better. Using CFB opamps probably wasn't a stellar choice for this one but the results and comments of the listening tests are worthwhile. Having second and third and fourth opinions of how something sounds is valuable information.
I have a but of an OT anecdote:
New to opamps really, i made a rectifier circuit for RMS to MAD ( in DC ) converter for data acquisition. Colleague suggested using the opamps he inherited and never uses...5532, 5534, 5539. Using 5532 and viewing the rectified AC at each valley between the 100hz half cycles, strange blurry 'spurs'.
Replaced the rectifier amp with LF353, problem solved. I'm going to check LME49720 just for giggles...
New to opamps really, i made a rectifier circuit for RMS to MAD ( in DC ) converter for data acquisition. Colleague suggested using the opamps he inherited and never uses...5532, 5534, 5539. Using 5532 and viewing the rectified AC at each valley between the 100hz half cycles, strange blurry 'spurs'.
Replaced the rectifier amp with LF353, problem solved. I'm going to check LME49720 just for giggles...
Blurry spurs 😀 you have to use 'em correctly. The 5532 should be docile enough though. Sounds like a touch of instability crept in.
http://www.diyaudio.com/forums/anal...u-have-checked-see-its-stable-havent-you.html
Fast opamp full wave precision rectifier (absolute value circuit) is extremely difficult to design and build!!! No way with slow part like 5532.
Well i just built one...
PMA i tried 5532 for the '5 equal R' diode circuit type. Mooly is correct, a touch of instability that showed itself thru extra oscillations nearing the Zero volts part of the rectifier wave, forming blurry lobes, or spurs lol. I have no idea why the jfet 353 worked so much better.
The following amp is a 5532, buffer then LPF. Seems accurate enough to me, will be calibrated in the coming weeks.
Its part of a board reading AC volts thru a 200:1 divider, via AD5B41 isolators RMS-DC (AD536), absolute (mean) volts to DC. 0-5VDC to logging.
PMA i tried 5532 for the '5 equal R' diode circuit type. Mooly is correct, a touch of instability that showed itself thru extra oscillations nearing the Zero volts part of the rectifier wave, forming blurry lobes, or spurs lol. I have no idea why the jfet 353 worked so much better.
The following amp is a 5532, buffer then LPF. Seems accurate enough to me, will be calibrated in the coming weeks.
Its part of a board reading AC volts thru a 200:1 divider, via AD5B41 isolators RMS-DC (AD536), absolute (mean) volts to DC. 0-5VDC to logging.
If you explore Bode plots of 5532 at unity gain you will find the answer for the small instability.
There is no problem with the following buffer and LPF. So i guess at unity, in differential operation its not quite the same. To be honest, they were just there. My collegue would never use them. He likes op07 for lots of things. Ill look at the datasheet closer, since in a filter or buffer they seem ok, i just thought id try lol. I switched with LF353 due to those being the only others i am familar*ish with with the same pinout.
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