IC6 replacement

[habitbraker]

Hello,

I wanted some experts opinion about this opamp - OPA699 http://focus.ti.com/lit/ds/symlink/opa699m.pdf
Will it give some improvement in operation?
AND ANOTHER QUESTION.
What if I use germanium diodes for D3 and D4?
thanks

[habitbraker]

Is there realy no opinnion?

[Reg]

Hi Habitbraker,

Personally, I would pick a different opamp than the one you mentioned if you want to try something else. However, the only way to satisfy your curiosity is to try the one you mentioned and see what happens. I suspect others haven't tried the one you mentioned and that is why there is no response. I know I haven't so I can't say just how it might work.

Over the years, several different op amps have been tried and even though the specs may seem impressive, few have worked out and most that did work didn't work without some help. A good example is the AD797. It works but really does need diode limiting across the feedback resistor to work correctly. Without the diodes, the amp stays in saturation too long. A lot of the other low noise op amps simply don't work when installed in place of the NE5534. Actually, some of the 5534's don't work as well as others, so even then, a person has to be careful.

Newer designs of PI's including the Hammerhead use a preamp with less gain than that found on the Hammerhead, which eliminates a lot of the problems. Then a second op amp is used to make up any gain difference. In other words, two amps are used instead of one at the input.

So, as an alternative, one could add an extra stage to the original HH with low gain before the first amp on the main pc board.

At least, that is a suggestion.

As for the diodes you mentioned, I suppose one could find some that work, but I doubt any improvement would be found. One has to be careful that any diode used will respond fast enough and not add any lag. So, the capacitance of the diode becomes an issue as does the current capability. So, once again, this is something you might want to try to find out for yourself and report back your findings. That is what a lot of people have done in the past.

Good luck.

Reg

[TRX]

Hello,

I need a substitute for 2N3906 (Q1, Q5, Q6, Q7), The place where I'm buying my parts has run out of them.


Also will be using 74HC123 instead of 74HC221. Hope that's ok.


Thank you.

[Qiaozhi]

Hello,

I need a substitute for 2N3906 (Q1, Q5, Q6, Q7), The place where I'm buying my parts has run out of them.


Also will be using 74HC123 instead of 74HC221. Hope that's ok.


Thank you.

It's difficult to believe they would be out of stock for very long. The 2N3906 is a general purpose PNP transistor and Farnell sell them in packs of 250. There are lots of possible alternatives, such as BC307A, EN3906 and BCY70.

[TRX]

2 days ago everything was in stock. Want to get all the components till Christmas.

Couldn't find any of those you specified. Maybe I'll wait a couple of days...

Thanks for the reply.

[chemelec]

It's difficult to believe they would be out of stock for very long. The 2N3906 is a general purpose PNP transistor and Farnell sell them in packs of 250. There are lots of possible alternatives, such as BC307A, EN3906 and BCY70.

Email me your Name and Address and I'll mail you "Four" of them for FREE.
[email protected]

PLEASE Put 2N3906 in the Subject Line.

Seasons Greetings
Gary

[TRX]

Very kind of you, but postage from Canada to Romania will take more thank 3 weeks. I'll order from another shop.


Thanks.

[TRX]

Just want to make sure that this components are correct, before soldering them


PN2222A instead of 2N3904
http://www.fairchildsemi.com/ds/PN/PN2222A.pdf
http://www.fairchildsemi.com/ds/2N/2N3904.pdf

BC327-16 instead of 2N3906
http://www.datasheetcatalog.org/data...or/BC327-D.PDF
http://www.fairchildsemi.com/ds/2N/2N3906.pdf

74HC123 instead of 74HC221
http://www.nxp.com/documents/data_sheet/74HC_HCT123.pdf
http://www.datasheetcatalog.org/data...T221_CNV_2.pdf

[cko47]

You wrote .......A lot of the other low noise op amps simply don't work when installed in place of the NE5534. Actually, some of the 5534's don't work as well as others, so even then, a person has to be careful.

I have this problem. Very low sensitivity. What You recommend?
Pin 3 (TP11) for IC7 not have any signal (view with oscilloscope). The change of second delay and sample width is ineffectual. Pin 2 have signal. But low.
The change of main delay or sample width change some TP10.

[Qiaozhi]

You wrote .......A lot of the other low noise op amps simply don't work when installed in place of the NE5534. Actually, some of the 5534's don't work as well as others, so even then, a person has to be careful.

I have this problem. Very low sensitivity. What You recommend?
Pin 3 (TP11) for IC7 not have any signal (view with oscilloscope). The change of second delay and sample width is ineffectual. Pin 2 have signal. But low.
The change of main delay or sample width change some TP10.

If there is no signal at TP11, then perhaps IC7b is not being switched. What signal do you have at TP7?

[cko47]

Signals on a TP6 and TP7 are identical but with different shift on time (delay).
When I try to detect metal changing of a second delay does not influence almost on audio signal.
Thank You for your reply.

[Qiaozhi]

Signals on a TP6 and TP7 are identical but with different shift on time (delay).
When I try to detect metal changing of a second delay does not influence almost on audio signal.
Thank You for your reply.

I am not sure I understand what you're saying. If you're asking whether adjusting the secondary delay time will have a major effect on the audio, then the answer is no. The purpose of the secondary delay is to provide a sample point further along the decay curve that is compared to the main sample. In this way any common signals will be eliminated. This is the purpose of the differential integrator.