More Schemo
- Thread starter analag
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Michael Krusch
Well-known member
How does it sound?
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Guest
Guest
interesting.... I need to get some more k170's....
Thanks for the schemo Rowan.
Thanks for the schemo Rowan.
I don't get it.
From the white-space at the bottom of the posted image, to why M1 eats so much power, to why Q1 works through a low-gain path to stabilize (maybe) the J1-J4 drain voltage, to C2 C3 bypaaing into that loop instead of ground, to J6 J7 fighting J5 J6 when the load is low-impedance. Or why you need four SK170s to take the wiper of a 50K pot and feed two gates.
From the white-space at the bottom of the posted image, to why M1 eats so much power, to why Q1 works through a low-gain path to stabilize (maybe) the J1-J4 drain voltage, to C2 C3 bypaaing into that loop instead of ground, to J6 J7 fighting J5 J6 when the load is low-impedance. Or why you need four SK170s to take the wiper of a 50K pot and feed two gates.
I do
Gone
I am going for low noise amplification, also M1 is now Q2
Q1 is actually there to provide a definable level of degenerative feedback
which in turn increases the input dynamic range of J1 J2, lowers noise, increases bandwidth, lowers distortion, etc.
C2 C3 bypassing into that loop produces a better looking high frequency response while working just as well in the low frequency range if it were connected to ground
Look at the value of R9, it is just high enough to cause J3 J6 to swing enough to help linearize the OPT performance and does minimalist reduction to output swing
That is subjective and a tweak was made. Even though I have an affection for brute force circuitry. It has a certain sound to it I think.
Analag
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Guest
Guest
ok, the other questions are fair questions....but who cares if there is a white space at the bottom of his posted image ? 
Swedish Chef
Well-known member
[quote author="Lo-Fi"]ok, the other questions are fair questions....but who cares if there is a white space at the bottom of his posted image ? [/quote]
PRR apparently... :roll:
I think the heavyweights get a little cranky when they fear someone may be mis-leading their flock.
The 'white space' dig was just indicative of that I think :grin:
chef
[/quote]PRR apparently... :roll:
I think the heavyweights get a little cranky when they fear someone may be mis-leading their flock.
The 'white space' dig was just indicative of that I think :grin:
chef
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Guest
Guest
[quote author="Swedish Chef"][quote author="Lo-Fi"]ok, the other questions are fair questions....but who cares if there is a white space at the bottom of his posted image ? [/quote]
PRR apparently... :roll:
I think the heavyweights get a little cranky when they fear someone may be mis-leading their flock.
The 'white space' dig was just indicative of that I think :grin:
chef[/quote]
nice avatar by the way.
i understand....it just seemed a little "nit-picky." i dont suppose a little white space would mislead anyone....but what do i know?
the only complaint i have about analag's post is that it's harder to read with a gray background....maybe the standard black-white thing would be cooler.... but again, that's just me being "nit-picky." :grin:
[/quote]PRR apparently... :roll:
I think the heavyweights get a little cranky when they fear someone may be mis-leading their flock.
The 'white space' dig was just indicative of that I think :grin:
chef[/quote]
nice avatar by the way.
i understand....it just seemed a little "nit-picky." i dont suppose a little white space would mislead anyone....but what do i know?
the only complaint i have about analag's post is that it's harder to read with a gray background....maybe the standard black-white thing would be cooler.... but again, that's just me being "nit-picky." :grin:
[quote author="Swedish Chef"]
I think the heavyweights get a little cranky when they fear someone may be mis-leading their flock.
The 'white space' dig was just indicative of that I think :grin:
chef[/quote]
No, I think PRR's just concerned about the web layout. Too large images make things hard to read for users with small screens.
Granted I don't know shit, some things in the schemo do look weird to me. Like the pot going directly to -30V. I'm not sure that's a solid construction. Trim pots blow easily.
Also the 50k pot at the input - I would think that introduces some series resistance and thus noise.
Did you actually build it? How does it sound and what about noise?
I think the heavyweights get a little cranky when they fear someone may be mis-leading their flock.
The 'white space' dig was just indicative of that I think :grin:
chef[/quote]
No, I think PRR's just concerned about the web layout. Too large images make things hard to read for users with small screens.
Granted I don't know shit, some things in the schemo do look weird to me. Like the pot going directly to -30V. I'm not sure that's a solid construction. Trim pots blow easily.
Also the 50k pot at the input - I would think that introduces some series resistance and thus noise.
Did you actually build it? How does it sound and what about noise?
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Guest
Guest
yes,
also, everyone, what has helped me sooo much when looking at posted schems, is a program ( totally free ) called irfan view. it is the bomb-diggidy on viewing schems and printing them in a useable format.
looking at the schem here, it is kind of hard to read, but i did a copy/pasted into irfan view and it looks great!
just a hint for everyone...
a guy that designs alot of eh guitar pedals showed irfan view to everyone on another forum, and it has helped me out tremendously.... :thumb:
also, everyone, what has helped me sooo much when looking at posted schems, is a program ( totally free ) called irfan view. it is the bomb-diggidy on viewing schems and printing them in a useable format.
looking at the schem here, it is kind of hard to read, but i did a copy/pasted into irfan view and it looks great!
just a hint for everyone...
a guy that designs alot of eh guitar pedals showed irfan view to everyone on another forum, and it has helped me out tremendously.... :thumb:
NewYorkDave
Well-known member
Ifranview is da bomb, for sure. I use it all the time.
www.irfanview.com
www.irfanview.com
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Guest
Guest
[quote author="NewYorkDave"]Ifranview is da bomb, for sure. I use it all the time.
www.irfanview.com[/quote]
yup, i used to have problems printing schems...(they would go off of the page, but that problem was fixed when i started using irfan view....
oh gosh, im starting to sound like a commercial...! :roll:
www.irfanview.com[/quote]
yup, i used to have problems printing schems...(they would go off of the page, but that problem was fixed when i started using irfan view....
oh gosh, im starting to sound like a commercial...! :roll:
clintrubber
Well-known member
Another satisfied Irfanview-user here.
And may I recommend MWSnap for screengrabbing ?
The other side of the graphic story so to say.
I'm more than satisfied about MWSnap (freeware, from http://www.mirekw.com/winfreeware/mwsnap.html )
but hmm, even if I wasn't this satisfied I would keep using it
- each time I use it it reminds me of our late singer,
from who I got it - but that's another story.
And may I recommend MWSnap for screengrabbing ?
The other side of the graphic story so to say.
I'm more than satisfied about MWSnap (freeware, from http://www.mirekw.com/winfreeware/mwsnap.html )
but hmm, even if I wasn't this satisfied I would keep using it
- each time I use it it reminds me of our late singer,
from who I got it - but that's another story.
The pot is there as an input trim (input sensitivity control) it is not a miniature 15 turn trimmer as you might believe. This control goes on the front panel.
After the input transformer gives us a free gain of 5 times whatever went into it.... a 50k pot does very little to noise. If I waited around for endorsements and approvals before I put my ideas and designs down on a perf board, I too would be left stuck wondering.
Analag
[quote author="analag"]
The pot is there as an input trim (input sensitivity control) it is not a miniature 15 turn trimmer as you might believe. This control goes on the front panel.
[/quote]
I'm a little confused. Are you talking about the 330 ohms pot or the 50K pot after the transformer? I'm a bit worried about the 330 ohms pot. Looks like there is serious DC on that one, which is never good for a pot. I think you should compute the wattage for that pot, if you haven't done so already. I don't think a normal pot will do, at least not for long.
[quote author="analag"]
After the input transformer gives us a free gain of 5 times whatever went into it.... a 50k pot does very little to noise. If I waited around for endorsements and approvals before I put my ideas and designs down on a perf board, I too would be left stuck wondering.
[/quote]
Have you tested it with low output dynamics or ribbons? That's where you might notice the noise the pot contributes.
The pot is there as an input trim (input sensitivity control) it is not a miniature 15 turn trimmer as you might believe. This control goes on the front panel.
[/quote]
I'm a little confused. Are you talking about the 330 ohms pot or the 50K pot after the transformer? I'm a bit worried about the 330 ohms pot. Looks like there is serious DC on that one, which is never good for a pot. I think you should compute the wattage for that pot, if you haven't done so already. I don't think a normal pot will do, at least not for long.
[quote author="analag"]
After the input transformer gives us a free gain of 5 times whatever went into it.... a 50k pot does very little to noise. If I waited around for endorsements and approvals before I put my ideas and designs down on a perf board, I too would be left stuck wondering.
[/quote]
Have you tested it with low output dynamics or ribbons? That's where you might notice the noise the pot contributes.
Rossi, there is no 330 ohm pot that I know of unless I get one made just for me, so therefore I used a 1k clarostat 2watt plastic conductor pot paralleled with a resistor to form the desired resistance. A wire wound pot could be used as well...I work with condensers almost exclusively so it's built for that...it's still in the testing stage and so far no problems. If noise is your concern, remove the 50k pot, if it then has too much gain rewire the input transformer for a 1:2.5 ratio. I use the 50k pot so that I can saturate the input transformer without overloading the FETs to get the colors I need. As a DIYer you should always customize your creation to suit your specific needs.
The greatest inventions are not the product of theory, but are of experiments and accidents.
Analag
The greatest inventions are not the product of theory, but are of experiments and accidents.
Analag
[quote author="analag"]
The greatest inventions are not the product of theory, but are of experiments and accidents.
Analag[/quote]
I'm not sure I agree. A lot of great stuff may be inspired by experiments, but usally there's a lot of theory in the refinement process. As for myself, I'm not much of a theory person, but I sure wish I knew more about theory to make experimentation more effective and consistent. I just got into spice simulation to learn more by experimenting in the sandbox, as it were.
Not too long ago I built PRR's ribbon booster (in real life, not in spice). That experience taught me a lot about resistance and noise. Base speading resistance can contribute a lot of noise. With the step up transformer the noise contribution of Rbb becomes significantly less. Still, you paralleled devices to lower Rbb (or whatever that's called in FETs) and thus get even lower noise. The 50k pot seems to defeat your own design purpose. The more you turn it down, the more series resistance you get. At half way down, the ratio between signal+noise resistance and pure noise resistance gets pretty bad. Unless I'm wrong, which is totally possible.
The greatest inventions are not the product of theory, but are of experiments and accidents.
Analag[/quote]
I'm not sure I agree. A lot of great stuff may be inspired by experiments, but usally there's a lot of theory in the refinement process. As for myself, I'm not much of a theory person, but I sure wish I knew more about theory to make experimentation more effective and consistent. I just got into spice simulation to learn more by experimenting in the sandbox, as it were.
Not too long ago I built PRR's ribbon booster (in real life, not in spice). That experience taught me a lot about resistance and noise. Base speading resistance can contribute a lot of noise. With the step up transformer the noise contribution of Rbb becomes significantly less. Still, you paralleled devices to lower Rbb (or whatever that's called in FETs) and thus get even lower noise. The 50k pot seems to defeat your own design purpose. The more you turn it down, the more series resistance you get. At half way down, the ratio between signal+noise resistance and pure noise resistance gets pretty bad. Unless I'm wrong, which is totally possible.
