I suppose I have learned new things along the way. For instance, I've never heard of the Preamp suggested. But, as I said, I went to the link'ed reveiw and skimed through it and I see where the output RCAs go directly to a transformer 😉
When I asked "Do you have manuals? What is the source output circuit? A follower? A transformer?" In a few minutes I answered that question.
Now the question is, what effects will the 2800 ohm Xfrmr output preamp have on the F3.
I'm not an expert either but that does not generally sound like a good match. I would think you'ld want a higher input impeadance than the F3 offers? I would suggest finding a sample and trying it? Now that we know a little more, maybe Nelson or someone else can answer more precicely?
When I asked "Do you have manuals? What is the source output circuit? A follower? A transformer?" In a few minutes I answered that question.
Now the question is, what effects will the 2800 ohm Xfrmr output preamp have on the F3.
I'm not an expert either but that does not generally sound like a good match. I would think you'ld want a higher input impeadance than the F3 offers? I would suggest finding a sample and trying it? Now that we know a little more, maybe Nelson or someone else can answer more precicely?
On second look, I confused the Pics in that reveiw with the power amp with Xfrmr output. The correct answer is still unkown to me because all I see in the pre pic is a PCB with a TO220 and 8 legged critter? That would not necessarily offer any easy reasoning why you have 2800 ohm output Z?
Give a a whril and see, is still a good option 🙂
Give a a whril and see, is still a good option 🙂
Not knowing myself, what issues would arise by driving the amp from an OT? In what scenarion would an OT be ok for the amp that follows. I know that recently there has been transformers used in FE of somw of Passm designs. His M2 is based on this I believe. There is also a member who recently put out the "Magma" FE for either BA output or even F4. How different is an input trafo to an output trafo? I ask only because I have stuff on the way to play with different F3 versions.
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Generally OTs are designed to meet specs working into a load equal to their impedance rating, so driving 2800 ohms should be fine but you will incur a 6db loss of signal because of the nature of matching impedances. It might still sound better working into a lighter load though.
Input trafos are usually wound quite differently, but generally can be used for output if loaded correctly.
Input trafos are usually wound quite differently, but generally can be used for output if loaded correctly.
Given what I can see about the Prima Luna, it has large enough output
capacitance and cathode followers, so it probably is fine with 10K load.
😎
capacitance and cathode followers, so it probably is fine with 10K load.
😎
sorry, it's me again. I am trying to understand all this based on my very limited electrical engineering knowledge.
My understanding about the importance of matching the impedance between the preamp and amplifier is because it acts like a band pass filter. If the input impedance of the amplifier is low, it makes the the cut off frequency high which results in bass roll off (low frequency got filter out)
The equation of the cut off frequency f = 1/(2*pie*R*C)
But as indicated by Mr. Pass, there is no capacitor. It has a series of resistor, the input impedance Z = R1 + R2 + ... + Rn
And if we say the impedance does not matter in this case, is it because without the capacitor, it no longer act as a low pass filter? Is this what Mr. Pass means the impedance number won't matter, but it depends on the circuit design?
I may have ask a stupid question, but I tried my best to understand this.
Thanks.
My understanding about the importance of matching the impedance between the preamp and amplifier is because it acts like a band pass filter. If the input impedance of the amplifier is low, it makes the the cut off frequency high which results in bass roll off (low frequency got filter out)
The equation of the cut off frequency f = 1/(2*pie*R*C)
But as indicated by Mr. Pass, there is no capacitor. It has a series of resistor, the input impedance Z = R1 + R2 + ... + Rn
And if we say the impedance does not matter in this case, is it because without the capacitor, it no longer act as a low pass filter? Is this what Mr. Pass means the impedance number won't matter, but it depends on the circuit design?
I may have ask a stupid question, but I tried my best to understand this.
Thanks.
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http://www.google.com/m/url?client=...oQFjAB&usg=AFQjCNH7oemET_JfAxRe3S5EDJyauIgYVA
Read this download from Erno borberly. In it he discusses Crss, Reverse Transfer Capacitance, also known as parascitic capacitance. If this does not help, look for a recent thread of mine on the topic.
http://www.diyaudio.com/forums/pass-labs/188268-f3-help.html
Read this download from Erno borberly. In it he discusses Crss, Reverse Transfer Capacitance, also known as parascitic capacitance. If this does not help, look for a recent thread of mine on the topic.
http://www.diyaudio.com/forums/pass-labs/188268-f3-help.html
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