no compromises ?
moderator Note: thread split from here http://www.diyaudio.com/forums/showthread.php?s=&threadid=138615
Hello Andrea
thanks for sharing.
You wrote “no compromise phono preamplifier”. But I can see some compromises.
First: The cathode bypass cap. It is not in the signal path but it has a strong sonic influence. Signal current causes voltage droppings and these are added (or subtracted) to the input signal between ground and grid.
Second: At high signal frequencies, there is more signal level at the grid of the input triode than at the output triode. Means dynamic loss at high frequencies.
Third: You have transformers in the signal path.
LG Darius
moderator Note: thread split from here http://www.diyaudio.com/forums/showthread.php?s=&threadid=138615
Hello Andrea
thanks for sharing.
You wrote “no compromise phono preamplifier”. But I can see some compromises.
First: The cathode bypass cap. It is not in the signal path but it has a strong sonic influence. Signal current causes voltage droppings and these are added (or subtracted) to the input signal between ground and grid.
Second: At high signal frequencies, there is more signal level at the grid of the input triode than at the output triode. Means dynamic loss at high frequencies.
Third: You have transformers in the signal path.
LG Darius
@ #6
Hi SY,
try to understand the difference between
signal path and current (loops). In the picture the red line shows the singal path, the green line shows the signal current in the output loop.
Comes from Have a look at some commercial schematics. This is the common way signal path is drawn.
I know, in the audiophool word it is different ... 😉
LG Darius
Hi SY,
try to understand the difference between
signal path and current (loops). In the picture the red line shows the singal path, the green line shows the signal current in the output loop.Comes from Have a look at some commercial schematics. This is the common way signal path is drawn.
I know, in the audiophool word it is different ... 😉
LG Darius
Attachments
Since the expression for voltage at any point in the signal circuit includes terms involving the cathode impedance, the cathode impedance is certainly in the signal path.
How does drawing a red line eliminate the cathode impedance terms from the expression for voltage at any point along it?
@ #10
The red line shows the signal path, that's all. Drawing the red line does not "eliminate" something. I'm sorry. Please note #7.
LG Darius
The red line shows the signal path, that's all. Drawing the red line does not "eliminate" something. I'm sorry. Please note #7.
LG Darius
How does the "signal" know that it doesn't go anywhere else? Is there no signal at the cathode? The bypass caps are perfect? No "signal" goes through the RIAA caps? They're an open circuit?
Drawing a red line doesn't change the flow of charge or take terms out of the transfer functions.
Drawing a red line doesn't change the flow of charge or take terms out of the transfer functions.
Darius,
I am relatively NEW to the hobby but I think that VOLTAGE of the signal being elavated is the Whole POINT of a Preamp.
As I understand all the posts, the goal is a minimum number of components in the signal path. The signal is a sine wave which has FREQUENCY. The voltage or AMPLITUDE changes are irrelavant as long as they are steady or FLAT throughout the AUDIBLE range. Since some changes are REQUIRED (RIAA EQ) then the goal seems to have been met IMHO. The F3 of the bypass caps is 1.1Hz can you hear 1.1Hz?? If so you need to be in the Guiness Book! My math may be a little "fuzzy" but by the time the frequency hits 21Hz (bottom threshold of hearing) The attentuation of the signal level is less than 1/10 of 1 percent.
I am relatively NEW to the hobby but I think that VOLTAGE of the signal being elavated is the Whole POINT of a Preamp.
As I understand all the posts, the goal is a minimum number of components in the signal path. The signal is a sine wave which has FREQUENCY. The voltage or AMPLITUDE changes are irrelavant as long as they are steady or FLAT throughout the AUDIBLE range. Since some changes are REQUIRED (RIAA EQ) then the goal seems to have been met IMHO. The F3 of the bypass caps is 1.1Hz can you hear 1.1Hz?? If so you need to be in the Guiness Book! My math may be a little "fuzzy" but by the time the frequency hits 21Hz (bottom threshold of hearing) The attentuation of the signal level is less than 1/10 of 1 percent.
@ #12
Hi SY
The signal does not know anything. The signal path just shows the way from input to output. There is signal current e.g in the cathode bypass cap. See first in post #4. You can draw the current loop “green line” Voltage droppings caused by the signal current have an influence in the signal. The signal current in the RIAA network causes a signal voltage drop at the 220K resistor. This makes the RIAA eq. Possible. 🙂
LG Darius
PS: The underlined/blue words are hyperlinks.
Hi SY
The signal does not know anything. The signal path just shows the way from input to output. There is signal current e.g in the cathode bypass cap. See first in post #4. You can draw the current loop “green line” Voltage droppings caused by the signal current have an influence in the signal. The signal current in the RIAA network causes a signal voltage drop at the 220K resistor. This makes the RIAA eq. Possible. 🙂
LG Darius
PS: The underlined/blue words are hyperlinks.
No, but many claim to be able to hear the effects of the nonideality of large electrolytic capacitors. Thus the claim of eliminating capacitors from the signal path. However, this is only true if one defines "signal path" as being "a red line drawn on a schematic." Unfortunately, in a real circuit, the voltages don't know about the red line and they are dependent on all paths that the current can flow, including places that don't have the red line drawn on them.
Audibility can be debated forever, but any impedance, R, L or C, that is in series with, or in parallel with, the signal, is "in the signal path". Did I get enough commas in there? That obviously includes anything to ground, but also includes anything to the power supply and all its branches. IMHO, that's pretty much everything, so discussions of what is or isn't in the signal path don't get at the real issues. It's the question of "how much and in what way does it affect the signal?" that's interesting.
cathode bypass
Hi SY
learn the difference between signal, voltage and current. Kirchhoff is not signal path. Understand how a circuit works and what influence electronic components have.
Hi coldcathode
the signal voltage drop at the bypass cap has a much bigger influence in the signal than the voltage drop of a supply rail capacitor. This is why I try to 'eliminate' them. The cathode bypass capacitor is one of the most critical components. If I must decide between cathode bypass ( in the signal current loop) and coupling capacitor ( in the signal path), I would take the coupling capacitor. See RIAA2001 input section.
LG Darius
Hi SY
learn the difference between signal, voltage and current. Kirchhoff is not signal path. Understand how a circuit works and what influence electronic components have.
Hi coldcathode
the signal voltage drop at the bypass cap has a much bigger influence in the signal than the voltage drop of a supply rail capacitor. This is why I try to 'eliminate' them. The cathode bypass capacitor is one of the most critical components. If I must decide between cathode bypass ( in the signal current loop) and coupling capacitor ( in the signal path), I would take the coupling capacitor. See RIAA2001 input section.
LG Darius
If I do that, will I then know how to draw arbitrary red lines?
Wow, you're as ignorant as I am! One day, Grasshopper, you will also know how to draw the Red Line.
I think SY and Conrad Hoffman have clarified that the audio signal does pass through all components that come in it's path including ones going to ground or any supply point. And strictly speaking all 'grounded' points are not the same or at "0.0000..." volts.
Why do you compare a coupling cap with a power supply cap ?
About choosing between a cathode bypass cap and an output coupling cap. I guess you mean which needs a better (expensive! )cap ? Both can degrade the sound and I think both are important . If possible I would not use a cathode bypass cap ( and pay a price by loosing gain etc..!) and just deal with the output coupling cap.
I find it quite funny that you should be trying to teach SY about signal flow.....!😀
Why do you compare a coupling cap with a power supply cap ?
About choosing between a cathode bypass cap and an output coupling cap. I guess you mean which needs a better (expensive! )cap ? Both can degrade the sound and I think both are important . If possible I would not use a cathode bypass cap ( and pay a price by loosing gain etc..!) and just deal with the output coupling cap.
I find it quite funny that you should be trying to teach SY about signal flow.....!😀
Most of the input tube's AC signal current passes through the cathode cap, any 'errors' are reflected back as a grid-cathode voltage. The cathode cap is very much in the signal path.
Re: @ #6
The red line appears to pass those transformers right by.
If the red line defines the "signal path", then of what use is consideration of the "signal path" since there are more components out of the "signal path" that influence the signal than in it?
Count me among the ignorant as well, since the last cap before the transformers is also in the signal path.
At any rate, if I were designing a cost no object phono stage, this is not likely how I would do it. However, that said, I bet it sounds lovely.
oldeurope said:
oldeurope said:
The red line appears to pass those transformers right by.
If the red line defines the "signal path", then of what use is consideration of the "signal path" since there are more components out of the "signal path" that influence the signal than in it?
SY said:
Count me among the ignorant as well, since the last cap before the transformers is also in the signal path.
At any rate, if I were designing a cost no object phono stage, this is not likely how I would do it. However, that said, I bet it sounds lovely.
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