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Old 13th February 2016, 08:43 AM   #1
guidobullo is offline guidobullo  Italy
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Smile Elektor PA300

nel progetto di elektor del PA300 tra il piedino 5 ed 8 di IC1 viene collegato un condensatore da 33p denominato C9. qualcuno mi sa dire il motivo di questa scelta circuitale? vorrei realizzare il progetto sostituendo NE5534 con un OPA627 oppure con un OPA604 in quanto per le mie orecchie NE5534 Ŕ troppo freddo in termini di resa sonora. un grazie in anticipo a chi risponderÓ a questa mia domanda. ciao allego il circuito elettrico

in the draft elektor of PA300 between the leg 5 and 8 of IC1 it is connected to a capacitor 33p called C9. someone can tell me why this circuit choice? I would like to implement the project by replacing NE5534 with OPA627 or with a OPA604 as for my NE5534 ears is too cold in terms of sound. thanks in advance to those who will respond to my question. Hello Enclose the electrical circuit
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Old 13th February 2016, 04:38 PM   #2
pozo1992 is offline pozo1992  Germany
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The 5534 is not unity gain stable, therefore a pin for frequency compensation is provided. the OPA604 is unity stable and doesen`t neet this cap. The OPA627 is different again. It maybe possible that this cap is not only responsible for the compensation of the opamp but also for the compensation of the whole amp too. difficult to tell from the schematic.
Anyway, I think easiest would be to try a OPA604 as it is unproblematic, the OPA627 is very fast so more critical to compensation and stability.
Salve, JŘrgen
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Old 13th February 2016, 09:56 PM   #3
guidobullo is offline guidobullo  Italy
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Smile grazie

thank you!
you know a program to simulate the various components, it's free
hello guido
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Old 14th February 2016, 03:45 AM   #4
tomchr is offline tomchr  Canada
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You can simulate the circuit using simulators such as LTspice and TINA-TI. Both are free. LTspice is from Linear Technology. TINA-TI is from Texas Instruments (TI).

Tom
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Old 6th August 2019, 01:15 AM   #5
xavirom is offline xavirom  Argentina
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Hi. I built this amplifier, but it has problems when it reaches the clipping point.
Is this normal for this circuit?

Thank you
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Old 6th August 2019, 05:41 AM   #6
Bruce@bluff is offline Bruce@bluff  South Africa
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I built a lot of these amps. If you use 5534 then you need to have a 33pf cap between pin 6 and 2 otherwise it will oscillate and do weird stuff when clipping. I have never tried the opa604
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Old 6th August 2019, 05:44 AM   #7
Bruce@bluff is offline Bruce@bluff  South Africa
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After seeing your attached thumbnail that weird behavior is caused by the protection circuits T4 and T5 activating
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Old 6th August 2019, 12:00 PM   #8
xavirom is offline xavirom  Argentina
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Thanks Bruce.
The capacitor is placed. That waveform is no load, with load the effect is the same, nothing changes by disconnecting the transistors from the VI limiter.
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Old 8th August 2019, 01:02 PM   #9
Kay Pirinha is offline Kay Pirinha  Germany
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@xavirom: Didn't the answers you've yet been given on the same question in PA300 ELEKTOR, clipping problem. satisfy you enough?
Best regards!
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Old 9th August 2019, 03:11 AM   #10
xavirom is offline xavirom  Argentina
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Hi Kay Pirinha. No, the only response there was, does not apply in this case.
Thanks for the question.
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