Experiment conducted. It seems, Ray, you were correct. I have learnt something. I tried making a single turn loop of different sizes using the scope leads and could see a difference in noise measurement. Conclusion there is still noise but not as much as I thought.
While I was at it I decided to complete the component changes detailed on your PDF. Now I'm ready to start creating and adding regulators. Was thinking that the DAC should get 4 LT317 based regs and the Opamps get 2 LT317 + 2 LT337 based regs as well. The rest of the CD player will get LM317 regs.
Just remembered that I built one of these (see schematic) just to see if I could. Have never used it ad had forgotten about it. Have tested it with 12v and it drops it nicely to 5.5v. However if you take your power for the regs from C814 (I think from memory) it only gives just over 10v, fine for a 7805, but not for this application. I suspect that with a change of resistor it could be made to fit.
An externally hosted image should be here but it was not working when we last tested it.
The schematic says min of 9v, so will try a 9v battery to see what output is.
What you have to realise is that I am now blind and stupid through years of solder sniffingNow I know why I could not get a reading off the resistors (even when off the board) using 20k setting!!!
Ah well.....more regs to go
Rob.
Yes, that's because it's a very low value
No, the whole thing is running on 5V. The resistors are in series with the 5V supply to each IC, dropping only very little voltage because their value is so low, and the current is not very high.
The resistor + the capacitor behind it act as a low-pass RC-filter that blocks HF noise and thus provides some separation of the various circuits. The resistor also acts as a fuse, it is a special non-flammable type that will burn out in case of a defective IC without setting the player on fire
.Ray
I see, the output of 5.5V is too high actually. That's because the output voltage is set by the LEDs, and in practise they give almost 4V the two, instead of 3.8V. Changing the resistor won't help, but using one red and one green LED will
If it says 'minimum 9V' at the input, why do you think it won't work on the 10V from C813?
Ray
Yes, that's because it's a very low value
No, the whole thing is running on 5V. The resistors are in series with the 5V supply to each IC, dropping only very little voltage because their value is so low, and the current is not very high.
The resistor + the capacitor behind it act as a low-pass RC-filter that blocks HF noise and thus provides some separation of the various circuits. The resistor also acts as a fuse, it is a special non-flammable type that will burn out in case of a defective IC without setting the player on fire
Ray
Thanks very much for the info and sharing your knowledge.
Rob.
I see, the output of 5.5V is too high actually. That's because the output voltage is set by the LEDs, and in practise they give almost 4V the two, instead of 3.8V. Changing the resistor won't help, but using one red and one green LED will
If it says 'minimum 9V' at the input, why do you think it won't work on the 10V from C813?
Ray
Once again thanks for your reply. I had assumed that as I had 5.5v from 12v I would get less output from 10v.
Noooo..... the circuit is a regulator, not something that just drops some voltage .
It's not like a resistor, that drops a fixed amount of voltage, depending on the current that runs through it, and the value of the resistor itself. That is called Ohm's Law, and it is V = I x R for a fixed value resistor.
The regulator circuit, on the other hand, holds the output voltage constant, independent of the input voltage or the load current. It compares the output voltage to a fixed reference voltage, and regulates the output voltage back to the desired value if the load or input voltage changes.
The reference voltage is usually an internal source, like an integrated zener. With the 7805 for example, the output voltage is pre-set to a fixed value and it's ready to use. The LM317 has an adjust pin, which gives access to some of the internals of the IC and that allows you to set the output voltage yourself. Usually this is done by two resistors, but you can also use an external zener, or some LED's to set the output voltage.
So, in short, if you connect this circuit to any voltage from 9V to 35V, it will give 5V output. Great, eh?
Ray
.It's not like a resistor, that drops a fixed amount of voltage, depending on the current that runs through it, and the value of the resistor itself. That is called Ohm's Law, and it is V = I x R for a fixed value resistor.
The regulator circuit, on the other hand, holds the output voltage constant, independent of the input voltage or the load current. It compares the output voltage to a fixed reference voltage, and regulates the output voltage back to the desired value if the load or input voltage changes.
The reference voltage is usually an internal source, like an integrated zener. With the 7805 for example, the output voltage is pre-set to a fixed value and it's ready to use. The LM317 has an adjust pin, which gives access to some of the internals of the IC and that allows you to set the output voltage yourself. Usually this is done by two resistors, but you can also use an external zener, or some LED's to set the output voltage.
So, in short, if you connect this circuit to any voltage from 9V to 35V, it will give 5V output. Great, eh?
Ray
Oh, yes, no problem, i'm not married yet! Sounds good, Rob and Ray. But only on the forum, ok?
5.5V is a bit too high for most IC's, it is the maximum supply voltage for some types. It's better to go for a 5V nominal voltage, that way there wil be some room for component tolerances.
The problem with using LEDs is that you have to find the right combination to get the desired output voltage. You need about 3.75V across the LEDs for a 5V output. A red LED has a 1.6V drop, a green one 2V, a yellow one 2.2V. But it can vary a little between brands and the current through them is also a factor of influence. So you can tweak the 220 ohm a little to get what you want.
Ray
5.5V is a bit too high for most IC's, it is the maximum supply voltage for some types. It's better to go for a 5V nominal voltage, that way there wil be some room for component tolerances.
The problem with using LEDs is that you have to find the right combination to get the desired output voltage. You need about 3.75V across the LEDs for a 5V output. A red LED has a 1.6V drop, a green one 2V, a yellow one 2.2V. But it can vary a little between brands and the current through them is also a factor of influence. So you can tweak the 220 ohm a little to get what you want.
Ray
Hi Rob,
A standard 7805 does it's job, it keeps the voltage constant and rejects incoming 100/120Hz ripple quite well. But in audio, high frequency noise is also an issue, and the standard regs don't perform very well here.
Read the Acoustica article. Part two is about noise rejection.
Ray
A standard 7805 does it's job, it keeps the voltage constant and rejects incoming 100/120Hz ripple quite well. But in audio, high frequency noise is also an issue, and the standard regs don't perform very well here.
Read the Acoustica article. Part two is about noise rejection.
Ray
Just adding a dab of RC filtering ahead of such things is always worthwhile though. Quite small values are effective, 4.7R and 10-100uF, say - if there's enough voltage headroom to stand dropping an extra volt or two.
All the resistor, cap and transistor do is allow you to use much larger resistors and smaller (film) caps, with the transistor providing buffering for useful amount of current output as Ray said. You have to pick a suitable transistor to suit the load current. For currents over say 50mA it will work better to use smaller resistors, say 1-2Kohm - and larger capacitors - say 10uF - for a couple of reasons. Mainly becasue you'll find the voltage drop becomes quite large as the transistor needs more and more base drive current - and higher current transistors generally have less current gain, needing more base drive... (and no, mosfets are not a panacea)
(Just catching up on this thread - I've no idea who added that 10K resistor to the 7812 schematic on the previous page !)
All the resistor, cap and transistor do is allow you to use much larger resistors and smaller (film) caps, with the transistor providing buffering for useful amount of current output as Ray said. You have to pick a suitable transistor to suit the load current. For currents over say 50mA it will work better to use smaller resistors, say 1-2Kohm - and larger capacitors - say 10uF - for a couple of reasons. Mainly becasue you'll find the voltage drop becomes quite large as the transistor needs more and more base drive current - and higher current transistors generally have less current gain, needing more base drive... (and no, mosfets are not a panacea)
(Just catching up on this thread - I've no idea who added that 10K resistor to the 7812 schematic on the previous page !)
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Actually at best they don't do anything that is useful where we are interested -in the audio band and maybe a decade or so above. In any case the noise from the reg is probably rather smaller than the noise created by the load...
The key things remain the circuit being fed must have a tight decoupling layout for the circuit served*, and then preferably a very low impedance feed - regulation.
* fancy decoupling caps on the output of voltage regs, esp aftermarket boards = exactly no use to the load; simply too far away. HF decoupling always, always they belongs right at the load, as tight as can be arranged.
The key things remain the circuit being fed must have a tight decoupling layout for the circuit served*, and then preferably a very low impedance feed - regulation.
* fancy decoupling caps on the output of voltage regs, esp aftermarket boards = exactly no use to the load; simply too far away. HF decoupling always, always they belongs right at the load, as tight as can be arranged.
Hi Badri,
All the mods for the 63 can be applied to the 53. Look on my website for more recent modslist. The one for the 63-KI is the most fancy one.
You should start by upgrading the capacitors and rectifier diodes in the power supply. Then upgrade the capacitors around the IC's. Remove the muting transistors and the output capacitors. Add a decent clock. For the 53, add some low-drop 8V regulators for the +/- 10V driver voltage and increase the capacitors for those voltages, or add an extra transformer for the driver section. Upgrade the filter components around the opamps and the opamps too. Or go fancy right away and add a DOS output stage that replaces all the opamp circuitry.
It will already be a completely different player after this, in a positive sense
Regards,
Ray
Thanks Ray. Can we use 3300uF/63Vdc in place of C803/804 and c814, 4700uF/40V in place of C813 and c815, and in C611..C614 can I replace 220u/25v caps or Can i go higher values like 470uF? And regarding bitumen sheet. I dont have access here in my place. But I have access to Stinger RoadKil sound deadening sheets but cost around 40$. Is it worth to buy? How much bitumen will cost per sheet?
Thanks
Badri
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