I'm of that oppinion that if you put your efforts into the circuit design and PCB-layout, you have gone 90% of the way.....
Think of old KRELL amplifiers etc. They still sound very good, even the fact that the caps used are 15+ years old, and should have been replaced 10 years ago......😉
Thanx Thomas for the enlightenment, one must learn something every day!
ACD, whil talking about opamps etc, is there table or list of the natural "speed" of instruments anywhere? For instance, the attack time of a piano, and what frequencies the attack contains?
Apart from the "colouration" of the sound etc by opamps (assuminging that newer, faster ones are better in that respect), is there any need to have opamps that are way faster than the instruments themselves?
ACD, have you replaced all caps in the Quad with 1% polyesters? Is there any improvements in changing all caps in the tone controls, RIIA etc for better ones (polyprops?)?
Cheers
ACD, whil talking about opamps etc, is there table or list of the natural "speed" of instruments anywhere? For instance, the attack time of a piano, and what frequencies the attack contains?
Apart from the "colouration" of the sound etc by opamps (assuminging that newer, faster ones are better in that respect), is there any need to have opamps that are way faster than the instruments themselves?
ACD, have you replaced all caps in the Quad with 1% polyesters? Is there any improvements in changing all caps in the tone controls, RIIA etc for better ones (polyprops?)?
Cheers
Tom
Quite a tricky question, however when speacking of amplifiers, you absolutelty need an Opamp/Circuit able to handle higher frequencies... The sonic in music is often caused by hormonic frequencies well above the human hearing. Therefore a faster opamp or circuit is necessary.
However... Radio-signals don't get above 18kHz and your CD-player cuts everything above 22kHz away, so........?????
Whats the idea???? But somehow it has some influence to get the hormonics amplified by amp. I normally uses 300kHz as upper limit (both for practical and economic reasons)
Quite a tricky question, however when speacking of amplifiers, you absolutelty need an Opamp/Circuit able to handle higher frequencies... The sonic in music is often caused by hormonic frequencies well above the human hearing. Therefore a faster opamp or circuit is necessary.
However... Radio-signals don't get above 18kHz and your CD-player cuts everything above 22kHz away, so........?????
Whats the idea???? But somehow it has some influence to get the hormonics amplified by amp. I normally uses 300kHz as upper limit (both for practical and economic reasons)
ACD, have you replaced all caps in the Quad with 1% polyesters? Is there any improvements in changing all caps in the tone controls, RIIA etc for better ones (polyprops?)?
tom
tom
Yes, I've changed all caps to newer and better types....
However the major improvement was the short circuiting of the DC-blocking caps, and replacement of Power Supply caps.
I really do not know how much the replacement of the remaining caps did for the sound, but as I was already in the process I changed all of them....🙂
However the major improvement was the short circuiting of the DC-blocking caps, and replacement of Power Supply caps.
I really do not know how much the replacement of the remaining caps did for the sound, but as I was already in the process I changed all of them....🙂
OK, sounds encouraging
I put Shottkys in the power supply, too, instead of the rectifying brigde.
I am aalso keeping an eye on the diodes on the psu board. Maybe there's an improvement to put Shottkys there, too?
Not even mentioning all the naked, unshielded signal cables everywhere...I have at least bypassed the psu board (the output signal goes from the tone control board, to the psu board and then to the outputs!)
I put Shottkys in the power supply, too, instead of the rectifying brigde.
I am aalso keeping an eye on the diodes on the psu board. Maybe there's an improvement to put Shottkys there, too?
Not even mentioning all the naked, unshielded signal cables everywhere...I have at least bypassed the psu board (the output signal goes from the tone control board, to the psu board and then to the outputs!)
Tom!
I didn't say that!!! It was "Analog_sa"!!!
However the inductors are a part of some kind of Low Pass filter
You can try to short circuiting them and see what happens... I think it's used to filter out the high frequency scratches from the record....🙂
I didn't say that!!! It was "Analog_sa"!!!
However the inductors are a part of some kind of Low Pass filter
You can try to short circuiting them and see what happens... I think it's used to filter out the high frequency scratches from the record....🙂Jan, I didn't say that you said that 😉 Just asked for a second opinion...sorry if I offended you, though
Is it more appropriate to break up the choke circuit, or is the 4k7 (R300) resistor useless unless I want to use the -ll- option on the phono input?
tom
btw, I can faintly hear radio? reception when I turn the volume to maximum using the radio input with 627s. The tuner is off, but the Cd is connected...might be the CD doubling as a receiver...
Is it more appropriate to break up the choke circuit, or is the 4k7 (R300) resistor useless unless I want to use the -ll- option on the phono input?
tom
btw, I can faintly hear radio? reception when I turn the volume to maximum using the radio input with 627s. The tuner is off, but the Cd is connected...might be the CD doubling as a receiver...
The R300 is in the circuit with the inductor, the 47pF and the 47K resistor.
My advise.....
Use it all or bypass the whole circuit🙂
My advise.....
Use it all or bypass the whole circuit🙂
Thank Jan, I'll bypass the whole shabang and see what happens
Guess I must lift out one leg of R302/3 and C302/3, too, right?
Sorry for taking so much of your time...
Btw, talking about circuit layout, that poor L channel 5mV signal has to travel a loooong way before it reaches its opamp...diagonally across the whole board...
tom
Guess I must lift out one leg of R302/3 and C302/3, too, right?
Sorry for taking so much of your time...
Btw, talking about circuit layout, that poor L channel 5mV signal has to travel a loooong way before it reaches its opamp...diagonally across the whole board...
tom
I think you should start keeping the R301 and R302 and also C302. This acts like low pass filter (R301/C302) preventing very high frequencies on the input, while R302 gives ref. to GND.
Let us know the results
Yes... QUAD have looooong signal paths around the PCB.
I think it's a product of paying bigger attention to the look of the PCB.
Let us know the results
Yes... QUAD have looooong signal paths around the PCB.
I think it's a product of paying bigger attention to the look of the PCB.
INCREDIBLE difference! Now the phono highs seem better than the CD (no news to vinyl freaks, of course)...
I lifted out R302/C302 and R303/C303, aren't R300 and 301 shorted already as they're paralell to the chokes?
I lifted out R302/C302 and R303/C303, aren't R300 and 301 shorted already as they're paralell to the chokes?
R300/301 are only shorted a lower frequencies by the inductor.
When frequency rices, the inductor starts to block these however some of the signal will pass through R300/301🙂
I've also experienced a much sound from the modified RIAA than I can get from my Lenco CD-player
When frequency rices, the inductor starts to block these however some of the signal will pass through R300/301🙂
I've also experienced a much sound from the modified RIAA than I can get from my Lenco CD-player
Yeah, the mod is done and after a couple of weeks one is already used to the better sound and the search for new improvements start, when will the curse end? 😉
No, I mean that since I put a shortcut (copper wire) from the input of choke 1 to the output of choke 2, R300/301 are shorted.
Is the low-pass filter to avoid RF to come in through the phono amp? (Remember there was smth like 1/RxC, using that I get 4,5 MHz)
tom
No, I mean that since I put a shortcut (copper wire) from the input of choke 1 to the output of choke 2, R300/301 are shorted.
Is the low-pass filter to avoid RF to come in through the phono amp? (Remember there was smth like 1/RxC, using that I get 4,5 MHz)
tom
Yes. This way R300/301 are are shorted.
However I think you keep a 4K7 resistor on the input of the opamp (of many reasons). You can easily do this just by removing your L300/L301 shortning and instead just cut the PCB connection between the L300 and L301.
The filter has many functions....
Both RF signals and other high frequencies picked up by your
pick-up are filtered away, and assures that your Opamp doesn't get frequencies that can get it to start oscillating.....
However I think you keep a 4K7 resistor on the input of the opamp (of many reasons). You can easily do this just by removing your L300/L301 shortning and instead just cut the PCB connection between the L300 and L301.
The filter has many functions....
Both RF signals and other high frequencies picked up by your
pick-up are filtered away, and assures that your Opamp doesn't get frequencies that can get it to start oscillating.....
Chokes
It depends on their A-rating.
I assume that they are very very small, but they could maybe be used in the supply lines for the RIAA opamps, combined with an extra cap........
It depends on their A-rating.
I assume that they are very very small, but they could maybe be used in the supply lines for the RIAA opamps, combined with an extra cap........
You may get incremental improvement with the Quad for a long time but does it make sense? It was, after all, a severely compromised design even in its heyday, let alone today. Unless you build a new PS, get rid of the analogue switches and all the junk parts it won't ever be really good. So, what's left? With about the same effort you can build something many times better. Or can you not make a box as ugly as a Quad? 🙂
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