hi everyone, does anybody have service manual of PA 7000?
I got this clone preamp of 7000 and have distortion problem on one channel and bad quality on other.
removed "keys part" from circuit (SC I mean), quality of right is fine but still have huge distortion on left output of first opamp.
here some pics I downloaded:
I got this clone preamp of 7000 and have distortion problem on one channel and bad quality on other.
removed "keys part" from circuit (SC I mean), quality of right is fine but still have huge distortion on left output of first opamp.
here some pics I downloaded:
Attachments
pcb is realy bad quality one, and had several disconnections.
I think the distortion was for filter cap went out of circuit
but theres a question, why output of device has smaller signal than opamps output,
is this natural?
output of opamps are very loud with headphone and another question,
can I use opamps output for headphone?
I think the distortion was for filter cap went out of circuit
but theres a question, why output of device has smaller signal than opamps output,
is this natural?
output of opamps are very loud with headphone and another question,
can I use opamps output for headphone?
tnx for the answer
hence there is a dc protection circuit can I remove coupling caps?
I suppose not right??
The 3-band (Bass, Middle, Treble) EQ _is_ active. 3 bands is about all this type of EQ can manage.
Why?
If the capacitor is bad, replace it with a good capacitor.
There is no large DC here, but small DC will increase (what Samsara calls) "plop". I am *sure* Gemini did not spend 5 cents for a cap without a reason. In PA mixers, caps are often wanted to reduce scratch and plot when controls are moved during the show. It is a fine design but not a "super hi-fi" design and I do not think random part changes will make it "better".
first of all tnx again for your time and answer.
whats the difference between 10uf coupling cap and 4.7uf? I have seen different caps for coupling. which is better? bigger or smaller?
I simulated this circuit and coupling 4.7uf at the output made huge differences. but I didn't get how muting section works
what about another opamp like opa27 or so? in simulation opa27 was about 40ms faster!
can you give me some guidance on hi-fi designs?
Impossible. (A 40 milli-Second delay requires an actual Delay Line; tape, BBD, 40 feet of pipe, or digital storage.) Re-read what the sim is telling you.
Anyway pure delay is not a problem. When I listen to an LP there is a 30-40 YEAR delay from recording to playback.
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