Noisy problem

[Kaz Kylheku]

But I think classD amp does not work well for this application. I have  to go back to AB amp.

Class D, and you still need all that heat sinkage?

In class D, the power transistors act as switches, just on and off. They should generate little heat.

Why do you think it does not work well?

And for speaker it is normal PA type,15" .

What is "PA type"? Is this an instrument speaker? (Make, model, ...) 15"? Is this for guitar or bass?

Why do you think class D won't work?

Evidently there are some bass guitar amplifiers out there using class D.

I have just reduce the gain of first OP-amp (Reversed circuit) . And leave the last OP-amp of tube simulation as buffer. So it seem OK for me now.

Good job! So too much front end gain was hissing out. No need to try different op-amps.

[Kaz Kylheku]

Here is an idea: replace your op-amp chip with an IC socket, so you can "plug and play" different chips that are pin-compatible. You can do an instant A-B listening comparison of different ones.

It was not without some reservations that I posted that, and I was originally going to put in a little cautionary note about considering the downsides of adding a bunch more electrical contacts to a circuit than it strictly needs.

Teemu's book has some good words about this:

Some IC sockets are extremely poor quality and develop intermittency or
high resistance after a very short period of time. Many high-speed OpAmps are also
very sensitive to stray capacitance the sockets introduce. Generally, decision whether
to use sockets or not is a compromise between easy serviceability and reliability.
Sockets should be used only with expensive ICs, ICs likely getting damaged (meaning
mainly those interfering with the outside world, i.e. the input and output stages) and
naturally for ICs that need to be upgraded now and then.

[teemuk]

I usually do use sockets but like implicated by the quoted stuff it's not a "high end" solution, rather a convenience: I like to recycle stuff from older projects and then there are times when one-off "prototypish" circuits go bad and kill the ICs. With this in mind its simply easier to live with sockets than without.

Indeed those sockets are also good for "OpAmp tasting" if you're into that type of thing.

[phatt]

Let's see it step by step


Dear nichapat: don't worry about this discussion among us, we love it, please show us what you did and we probably can suggest something useful for you.
That's what this Forum is about.
*Maybe* both projects together on full blast are too much , but at least each of them in its own should work properly.
Good luck.

Wow thanks Jaun, Though it will take me another week to decipher it all LOL. xP
Most of it I do grasp but sometimes the brain just frys with too much info.

I do in the end just breadboard stuff that I think will have merit and with the help of this site and some basic simulations I work out how to get the most out of circuits.

Though I cannot explain the maths involved I did learn a lot about inter-stage coupling and averting needless noise issues while building my Tone circuit, Which is of course why I mentioned it early on.

Phil.

[phatt]

I usually do use sockets but like implicated by the quoted stuff it's not a "high end" solution, rather a convenience: I like to recycle stuff from older projects and then there are times when one-off "prototypish" circuits go bad and kill the ICs. With this in mind its simply easier to live with sockets than without.

Indeed those sockets are also good for "OpAmp tasting" if you're into that type of thing.

Maybe if people applied a lot more patience with building stuff then on-board sockets would not be needed.
If it's just another stomp box then far better to just breadboard another circuit and save youself the pain.

Speaking from experience,,, try desoldering some of those sockets when they break,,not fun. :grr :loco
Faster if you just use a  chip.
My 2 cents worth.

[teemuk]

Speaking from experience,,, try desoldering some of those sockets when they break,,not fun. :grr :loco

Say no more. Been there, done that: The stuff is so flimsy it usually just disintegrates or melts. Personally, I hate trying to get anything with more than few leads off from a PC board when you're in a tough spot where you want to keep both the removed part and the PC board intact. Things don't usually seem to compute in that situation.

I guess the reason why I tend to use sockets is that I simply know myself too well in regard that every project will eventually again end up to the "surgical table" to be modified, used as a part of another project or simply stripped down for parts to recycle. If it was a "finish-and-forget" -type of commercial thing I wouldn't bother in socketing stuff. An average solderer can still replace a basic failed opamp or any other DIP-cased IC, even if the part wasn't socketed. If its failed to begin with you don't have to worry about clipping leads or keeping the part intact and the swap is a breeze.