The OPA627 really sings

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#101
Hi Carlos

I use now 2x10000uF and 2x2200uF per channel (in fact, just 6100uF per rail), following by 1uF, 0,1 uF foil and 0,1uF ceramics direct at the pins. Cheap electrolytics (Jamicon and Philips).

No C in the signal path, at all. No zobel, no LR network, nothing at all. 2x22VAC 225VA torroid.

Nothing inverted, no buffer, no cap between the inverted input and the ground. Just a resistor.

Franz
 
#102
And here are currents through upper and lower output transistor, and output voltage and output current. You can see that only the upper transistor conducts. Increasing input voltage for this load (1.6k) the lower transistor will start to conduct as well. for higher load resistance it will be true class A for all output voltages.
 

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#104
Franz G said:
I use now 2x10000uF and 2x2200uF per channel (in fact, just 6100uF per rail)...
Click to expand...

With one PSU for two channels that is 12,200uf per rail.
That doesn't sound good to me, but you may have other oppinion.
Don't take first impressions for granted, listen to the amps, compare.

Anyway, I'm not going to deeply discuss these matters anymore.
I opened this thread to share my experience with the OPA627.
I hope it's useful for someone.
 
#105
Franz G said:
Hi Carlos

I use now 2x10000uF and 2x2200uF per channel (in fact, just 6100uF per rail), following by 1uF, 0,1 uF foil and 0,1uF ceramics direct at the pins. Cheap electrolytics (Jamicon and Philips).

No C in the signal path, at all. No zobel, no LR network, nothing at all. 2x22VAC 225VA torroid.

Nothing inverted, no buffer, no cap between the inverted input and the ground. Just a resistor.

Franz
Click to expand...


Hi Franz!

Am contemplating to do just what you did, but I lacked the time, and instead made those that have been tested by carlosfm et. Al. Correct me if I am wrong on the impression I got from your post:

(1) you are using NIGC
(2) unregulated PSU
(3) no pre-amp (no buffer)
(4) 5 capacitors in the power rail
- 2x 10k uF
- 2x 2.2k uF
- foil 2x 1uF and 0.1uF
- ceramic 2x 0.1uF
(5) Your impression: this config is better than the buffered regulated IGC [or is it NIGC] (in your own assessment).

Thanks.
 
#106
Nuuk said:

I think you are referring to the album 'The Girl In The Other Room'! But on some of her other recordings, I have found that her voice is not precisely located and I have assumed this is due to her voice being picked up by both her mike and the mike in the piano.
Click to expand...
yes, that's the album i was referring to. her other recordings seem to have her located slightly to the right... at least that's what i feel.

carlosfm said:
Listen to Jacintha "Jacintha is her name" and in a while you'll be crying.:bawling:
😎
Click to expand...
hmm... not much news abt Jacintha locally though... she had a few albums that made it into the international audiophile reviews. was actually surprised that a Singapore album can achieve that.
 
#107
aHobitt:

Thats right, the configuration you write, I compare it to a buffered regulated IGC.

The above configuration is correct, but don't forget: just "normal" diodes, nothing ultrafast (they dont need any bridging with caps).

The result is very good and I need some more time to compare it to other solutions.

Carlos: 2x10000uF in series is 5000uF, 2x2200uF in series = 1100uF, this 5000uF and the 1100uF in parallel = 6100uF are working per rail.

All other calculations are just "marketing".

Franz
 
#108
yes, that's the album i was referring to. her other recordings seem to have her located slightly to the right... at least that's what i feel.
Click to expand...

Exactly what I find. On the 'A NIght in in Paris' CD, on track 10, at the beginning her voice seems to move more to the right and then back toward the centre. I played that track just after building my first GC and thought it was a problem with the amp!
 
#110
Franz G said:
Carlos: 2x10000uF in series is 5000uF, 2x2200uF in series = 1100uF, this 5000uF and the 1100uF in parallel = 6100uF are working per rail.
Click to expand...

In series?😕
In parallel?😕

If you are feeding two channels from one PSU aren't all the caps in one rail in parallel?
Maby if you post a schematic... I'm a little confused...

Franz G said:
All other calculations are just "marketing".
Click to expand...

Calculations are marketing?😕
 
#111
HI,Carlosfm

I had introduced your excellent experiences to my friends.But... two of them told me not to get the expected better results:dead:

sounds smoother,the bass better,but the definition worse,some weak sounds lost.

carlosfm said:
I must say that I don't have biasing into class-A on my OPA627+BUF634 pre
Click to expand...

Oh,my god!

I just read your post:bawling: :bawling:

their amps are OPA627+BUF634T!:cannotbe:


Nuuk said:
Slightly OT but can anyone identify this chip for me?

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


A search on Google doesn't bring anything up. I would guess it is a dual but I found three of them on the output of an old Pioneer CDP.
Click to expand...

Hi,Nuuk

The IC is M5238,produced by Japanese company(Misu????)which the Logo showed.

Here is one of the link I just searched

http://www.talkaudio.co.uk/vbb/showthread.php?t=59742
 
#114
I mean by "marketing calculation": just add all capacitance in an amp and write about the sum in the flyer :xeye:

Here is the PSU schematics:

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


The testamp looks like this:

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


It is important to say: this amp sounds different than the buffered version. I am sure, bass is better.

But I can not tell you up to now, wich amp I prefer. Give me one or two weeks of comparing them.

Carlos: please dont forget we use different speakers: I drive fullrange speakers in backloaded horns. I NEVER use more than 1W output!

Franz
 
#115
#116
Franz G said:
Carlos: please dont forget we use different speakers: I drive fullrange speakers in backloaded horns. I NEVER use more than 1W output!

Franz
Click to expand...

Ah, that's a completely different story.
With those easy to drive speakers you may not need to regulate.
The unregulated amp will give good results, although I like it with much less capacitance.
The capacitance you have gives better bass but affects midband and treble, it throws away the "magic" of these chips.
The unreg. amp will give very good results with your speakers, but if you test it with "normal" speakers you'll find out that the reg. amp will drive them much better. The result is tighter and better bass and you'll follow the music much better, everything is more defined.
You make the amp that you need. If unreg. gives better results for you, go for it.
BTW with those speakers you can even use the LM1875, wich is IMHO very good.
 
#120
I've soldered a 1.8K resistor on top of a "high leg" dip socket because I don't want to make further damage to the PCB "IF" this is no good. The pre-amp I am using is ML38S and the opamp in test is OPA627BP
An externally hosted image should be here but it was not working when we last tested it.


When I turned on the system right after the installation, I am really amazed to hear the system really sings. I used to test many systems with Maria Callas "La Mamma Morta" and her mouth, in the previous system, doesn't open wide enough. However, with the installation of resistors, her mouth is now wide open!! The base is deepened and the high is extended. I really like to see how it works after a day or two.

One question. The OPA627 was used to run at 37 degree C but now it sometimes goes up to 45 degree C. Do I need headsinks?

Sunny
 
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