No need if I use link wires, the whole tone circuit is out of the signal path. Do you have the schematic, I cant remember if I sent you one or not. In the bypass trace there is a DC blocking cap (c:19,29) and a 150k resistor to ground (r:52,54). I know I dont need the cap as I have low enough DC offset at the input buffer output, and the power stage has a DC blocking cap before it too for good measure. Looking at the schematic I cant see that this resistor is part of an attenuation circuit, this is allready in place at the phono inputs and the input to the LM3886. Whay this extra resistor to ground in the tone bypass?
the resistor provides 'pop'-less switching.
If it wouldn't be there, the cap would be charged every time you switch to the path.
Switches and pots should be made DC-free by caps.
Personally, I think a few mV don't hurt and a small click or pop is tolerable.
You can try out yourself by shorting the cap. If you don't like it, you can remove the wire later without damaging anything.
The resistor can be left in place.
regards
If it wouldn't be there, the cap would be charged every time you switch to the path.
Switches and pots should be made DC-free by caps.
Personally, I think a few mV don't hurt and a small click or pop is tolerable.
You can try out yourself by shorting the cap. If you don't like it, you can remove the wire later without damaging anything.
The resistor can be left in place.
regards
Hello, Mike.
Some info about NFB.
http://www.diyaudio.com/forums/showthread.php?postid=1717818#post1717818
Don't You want to try?
Some info about NFB.
http://www.diyaudio.com/forums/showthread.php?postid=1717818#post1717818
Don't You want to try?
Thanks Stream.
So with a 100uF NFB cap (which I have at the moment - Rubycon ZL) I need probably 2 x 1.65uF DC blocking caps in the signal path? (1 at preamp input and one at Poweramp input)?
Obviously there is little chance of finding a cap at this value (1.65uF) so 2uf or 2.2 might be ok. My CDP has no DC blocking at the output due to the fantastically low DC offset of the LM4562 I am using.
Based on this I think I should put the 2.2uF Mundorf MKP's back in?
So with a 100uF NFB cap (which I have at the moment - Rubycon ZL) I need probably 2 x 1.65uF DC blocking caps in the signal path? (1 at preamp input and one at Poweramp input)?
Obviously there is little chance of finding a cap at this value (1.65uF) so 2uf or 2.2 might be ok. My CDP has no DC blocking at the output due to the fantastically low DC offset of the LM4562 I am using.
Based on this I think I should put the 2.2uF Mundorf MKP's back in?
Hi,
you don't need to block the DC at the input twice. Once is sufficient.
To allow for equipment swapping it is usually accepted that it is safer to block the DC at both the output of the source and at the input of the receiver.
If both DC blocking caps are fitted then the effective value of the capacitance is C1 * C2 / (C1 + C2).
If 4u7F were fitted at the source output and 2u2F were fitted at the receiver input then the effective capacitance is 1u5F.
Combine this with Zin=22k and the F-3dB ~4.8Hz, F-1dB~9Hz.
Now to your 4562 in the CDP.
Yes, very low input offset current and as a result very low output offset voltage.
Is it set up as an AC coupled amplifier or as a DC coupled amplifier?
It will make a very good job of amplifying any DC presented to it's input pins if it's a DC coupled amplifier.
Omitting DC blocking on the output will allow this amplified DC to be sent to the next stage. Very definitely refit the DC blocking at the power amp input.
The offset performance of the 4562 is completely irrelevant to this operational situation.
you don't need to block the DC at the input twice. Once is sufficient.
To allow for equipment swapping it is usually accepted that it is safer to block the DC at both the output of the source and at the input of the receiver.
If both DC blocking caps are fitted then the effective value of the capacitance is C1 * C2 / (C1 + C2).
If 4u7F were fitted at the source output and 2u2F were fitted at the receiver input then the effective capacitance is 1u5F.
Combine this with Zin=22k and the F-3dB ~4.8Hz, F-1dB~9Hz.
Now to your 4562 in the CDP.
Yes, very low input offset current and as a result very low output offset voltage.
Is it set up as an AC coupled amplifier or as a DC coupled amplifier?
It will make a very good job of amplifying any DC presented to it's input pins if it's a DC coupled amplifier.
Omitting DC blocking on the output will allow this amplified DC to be sent to the next stage. Very definitely refit the DC blocking at the power amp input.
The offset performance of the 4562 is completely irrelevant to this operational situation.
Hi Mike,
I have seen failures in equipment with no DC blocking capacitors that have caused grief down line in the system. You're always safer to use blocking capacitors at both ends.
Most preamps have an input impedance of approx. 50K. That is an industry standard. I have seen as low as 10 K used, buy that is rare.
Most amplifiers present a 50 ~ 100 K load, but there seems to be a trend towards lower values. Probably to reduce noise pickup. No required to reduce noise, but it is the easy way out.
-Chris
That's always a very good idea when asking advice.
I have seen failures in equipment with no DC blocking capacitors that have caused grief down line in the system. You're always safer to use blocking capacitors at both ends.
Most preamps have an input impedance of approx. 50K. That is an industry standard. I have seen as low as 10 K used, buy that is rare.
Most amplifiers present a 50 ~ 100 K load, but there seems to be a trend towards lower values. Probably to reduce noise pickup. No required to reduce noise, but it is the easy way out.
-Chris
Stream said:
So. First Expirience
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An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Just need to make holes... BUT... I made serios mistake - didn't mirored the layout
So it's just sample ))
Hi Stream,
Not bad. How are you laying these out?
The way I do single boards is to lay out the PCB on graph paper, 10 or 20 divisions to the inch. Then I drill out the holes and clean the PCBs while deburring the holes. Then I just "connect the dots" with a resist pen.
For surface mount, I'll have to learn how to use a schematic capture and layout program.
-Chris
Not bad. How are you laying these out?
The way I do single boards is to lay out the PCB on graph paper, 10 or 20 divisions to the inch. Then I drill out the holes and clean the PCBs while deburring the holes. Then I just "connect the dots" with a resist pen.
For surface mount, I'll have to learn how to use a schematic capture and layout program.
-Chris
Did a bit of work on the amp today.
Wima MKS2 caps are amazing! 22uF MKS2-XL feddback and 3.3uF MKS2 for DC blocking. Gone is the harsh treble and wooly bass. Much much better. PFM thread.
Mike
Wima MKS2 caps are amazing!
22uF MKS2-XL feddback and 3.3uF MKS2 for DC blocking. Gone is the harsh treble and wooly bass. Much much better. PFM thread. Mike
Sucess story.....
The most revealing indication of the improvements so far.
Had a listen to an album I got a while ago but didn't listen to it much....
'Newton Faulkner - Hand built by Robots'
Now this is an album that I initially thought was badly produced, it just didn't sound right and I couldn't bear to listen to it despite the great music.
So last night I got home and the GF had put it on and had it playing quite loud. It immediately got my attention so I got comfy on the sofa and had a listen. WOW! I hadn't realised just how good this album is! The well aired cover of Massive attacks 'Teardrop' was bordering on jaw dropping! The songs emotive qualities rally hitting hard and the mostly acoustic instruments each clearly definable and sounding as they should, acoustic. Sometimes acoustic instrument when poorly reproduced can have an almost artificial nature sounding like something generated by a computer. This wasn't the case and with closed eyes I was almost there with my own live performance in the lounge. It really was a special moment to experience this and was all the more satisfying to know that all the naive questions, their answers, all the help received on DIYA (and PFM), the trouble shooting, and research was worthwhile. To know that I had modified my system up to this level of enjoyment is immensely satisfying.
The fact that this previously un-listenable CD now sound's so good only indicates one thing: That my system really has stepped up a notch or two in sound quality. Its not over yet as more mods planned but I just want to thank all those who helped me so far, and everyone who posted on this thread.
The most revealing indication of the improvements so far.
Had a listen to an album I got a while ago but didn't listen to it much....
'Newton Faulkner - Hand built by Robots'
Now this is an album that I initially thought was badly produced, it just didn't sound right and I couldn't bear to listen to it despite the great music.
So last night I got home and the GF had put it on and had it playing quite loud. It immediately got my attention so I got comfy on the sofa and had a listen. WOW! I hadn't realised just how good this album is! The well aired cover of Massive attacks 'Teardrop' was bordering on jaw dropping! The songs emotive qualities rally hitting hard and the mostly acoustic instruments each clearly definable and sounding as they should, acoustic. Sometimes acoustic instrument when poorly reproduced can have an almost artificial nature sounding like something generated by a computer. This wasn't the case and with closed eyes I was almost there with my own live performance in the lounge. It really was a special moment to experience this and was all the more satisfying to know that all the naive questions, their answers, all the help received on DIYA (and PFM), the trouble shooting, and research was worthwhile. To know that I had modified my system up to this level of enjoyment is immensely satisfying.
The fact that this previously un-listenable CD now sound's so good only indicates one thing: That my system really has stepped up a notch or two in sound quality. Its not over yet as more mods planned but I just want to thank all those who helped me so far, and everyone who posted on this thread.
Hello. Just finished all tweaks...
Full list of changes:
Power Supply:
Main filter caps: CA 6800uF => CA 10000uF
Main diodes: 1N5402 => MUR860
15V diodes: 1N4002 => Shottki STPS2H100
+15V filter in cap(C45): 1000uF Fujicon => 1000uF Panasonic FC
+15V filter out cap (C49): 100uF lh.nova => 470uF Pana FC
-15V filter in cap (C46): 470uF Xunda => 1000uF Pana FC
-15V filter out cap (C50): 100uF lh.nova => 470uF Pana FC
+5V out cap (C47): 47uF Xunda => 47uF Pana FC
Input Selector:
CD, Aux DC blocking caps (C21,56,57,60,61,65): 10uF NP => wire link.
Other (C30,31,33,62,63,64): 10uF NP => 4.7F Elna Silmic II.
Input Buffer:
Opamp: NE5532 => Opa2134
Opamp decoupling (C7,8): 47nF mkt (?) => 33nF Wima FKP + 4.7uF Elna Silmic II
Input DC blocking cap (C14,25): 10uF lytic => 3.3 Wima MKS2
10pF ceramiq.(C58,59) => 10pF Silver Mica
22pF ceramiq. (C12,13)=> 22pF Silver Mica
Volume, Balance, Tone Control :
47uF lytics (C19,C20,C29,C32) => wire link
Treble tone 330pF poly (C1,C10) => 330pF Wima FKP
Opamp feedback cap (C9,C15): 10pF ceramiq. => 10pF Silver Mica
Supply decoupling caps(C16,C17):47nF mkt => 33nF Wima FKP
Power Amp :
Input DC blocking caps (C3,37): 10uF lytic => 3.3 uF Wima MKS2
Supply decoupling caps (C40,41,42,43): 100uF 50V RGTX (?) => 470uF 50V Pana FC + 150nF Wima MKS2
Feedback nfb caps (C22,38): 47uF 16V=> 100uF 25V Elna Silmic II
Feedback ceramiq. (C73,74): 10pF => 10pF Silver Mica
33pF ceramiq. (C71,C72) : => 33pF Silver Mica
Output filter cap (C2,C36): 100nF ceram. => 100nF Epcos MKT
Signal gnd to main gnd caps (C67-C70): 1nf ceram. => 1nf Wima FKP.
Photos:
Full list of changes:
Power Supply:
Main filter caps: CA 6800uF => CA 10000uF
Main diodes: 1N5402 => MUR860
15V diodes: 1N4002 => Shottki STPS2H100
+15V filter in cap(C45): 1000uF Fujicon => 1000uF Panasonic FC
+15V filter out cap (C49): 100uF lh.nova => 470uF Pana FC
-15V filter in cap (C46): 470uF Xunda => 1000uF Pana FC
-15V filter out cap (C50): 100uF lh.nova => 470uF Pana FC
+5V out cap (C47): 47uF Xunda => 47uF Pana FC
Input Selector:
CD, Aux DC blocking caps (C21,56,57,60,61,65): 10uF NP => wire link.
Other (C30,31,33,62,63,64): 10uF NP => 4.7F Elna Silmic II.
Input Buffer:
Opamp: NE5532 => Opa2134
Opamp decoupling (C7,8): 47nF mkt (?) => 33nF Wima FKP + 4.7uF Elna Silmic II
Input DC blocking cap (C14,25): 10uF lytic => 3.3 Wima MKS2
10pF ceramiq.(C58,59) => 10pF Silver Mica
22pF ceramiq. (C12,13)=> 22pF Silver Mica
Volume, Balance, Tone Control :
47uF lytics (C19,C20,C29,C32) => wire link
Treble tone 330pF poly (C1,C10) => 330pF Wima FKP
Opamp feedback cap (C9,C15): 10pF ceramiq. => 10pF Silver Mica
Supply decoupling caps(C16,C17):47nF mkt => 33nF Wima FKP
Power Amp :
Input DC blocking caps (C3,37): 10uF lytic => 3.3 uF Wima MKS2
Supply decoupling caps (C40,41,42,43): 100uF 50V RGTX (?) => 470uF 50V Pana FC + 150nF Wima MKS2
Feedback nfb caps (C22,38): 47uF 16V=> 100uF 25V Elna Silmic II
Feedback ceramiq. (C73,74): 10pF => 10pF Silver Mica
33pF ceramiq. (C71,C72) : => 33pF Silver Mica
Output filter cap (C2,C36): 100nF ceram. => 100nF Epcos MKT
Signal gnd to main gnd caps (C67-C70): 1nf ceram. => 1nf Wima FKP.
Photos:
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