I`ve looked many times at Frank`s line pre-amp.Ok if 100mv goes in, let`s say from a cd player or a phono pre,how much voltage comes out.Just a ballpark figure.Al
Since the cathode resistor (first stage) in Frank's design is un-bypassed, there is going to be some degeneration of the signal voltage. I am not near my equipment right now (nor have a messed around with the circuit in awhile) but I would say the voltage gain of the circuit would be about 10, so if 100mV was the input, you could expect to get 1V out.
Thank for the response. Îs there any way to increase the gain, say to 15 or a bit more... without any major changes , say a cap between cathode and ground...I am aware of the coloration that accompany
Is there a way to get more gain, say 15-20x...A cathode by- pass capacitor maybe... I am aware that any increase in gain can result in coloration...
quote:
Is there a way to get more gain, say 15-20x...A cathode by- pass capacitor maybe... I am aware that any increase in gain can result in coloration...
I made this one years ago and put a by pass cap on the cathode of the 6sn7.
I didn't think it added any colorization but it did add gain.
Is there a way to get more gain, say 15-20x...A cathode by- pass capacitor maybe... I am aware that any increase in gain can result in coloration...
I made this one years ago and put a by pass cap on the cathode of the 6sn7.
I didn't think it added any colorization but it did add gain.
Hello,
I just plugged the first stage of franks preamplifier into the simulator. As is without a cathode bypass capacitor the gain looks to be in the range of 9. With the cathode bypassed the gain is in the range of 17, right on the requested target.
A fun trick you do not see in words often is using a couple of resistors in series that add up to the original cathode resistor value and connect the cathode bypass capacitor at the divider point between the resistors. Using this technique you can adjust the cathode resistor feedback and stage gain to any point between full capacitor bypass and none. If you have the bench tools you can measure gain, 2nd and 3rd harmonics. Tune them to where you want.
DT
All just for fun!
I just plugged the first stage of franks preamplifier into the simulator. As is without a cathode bypass capacitor the gain looks to be in the range of 9. With the cathode bypassed the gain is in the range of 17, right on the requested target.
A fun trick you do not see in words often is using a couple of resistors in series that add up to the original cathode resistor value and connect the cathode bypass capacitor at the divider point between the resistors. Using this technique you can adjust the cathode resistor feedback and stage gain to any point between full capacitor bypass and none. If you have the bench tools you can measure gain, 2nd and 3rd harmonics. Tune them to where you want.
DT
All just for fun!
Hey , long time...your sugestion was well received.Now I have stumbled upon a neat program freeware;It`s called ``visual analyser``.com.See for yourself,and there are many others.With this program I get 2 trace occ.distortion analyser ,function generator and much more.It irrates me when I contemplated the purchase of rta programs...no need
Is there a possibility to add a ``current source ``to this line stage...Or is it a complete waste of time.I welcome any input
I built with 6cg7 (pins are different) based on the scheme, but I have a loud noise and no music. Do you know my mistake?
12at7
I built with 12at7 / ecc81. I do not know what I did but the sound is better for me.
Modification: 50k pot instead of 100k- 1k resistor instead of 0.047 uF capacitor.
Can you give me advice?
Thanks
I built with 12at7 / ecc81. I do not know what I did but the sound is better for me.
Modification: 50k pot instead of 100k- 1k resistor instead of 0.047 uF capacitor.
Can you give me advice?
Thanks
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can anyone post the schematic of the RPA preamp? no links on the net are working since the thread is about a decade old.
Secondly my observations towards using just choke for filtering improved the sound quality considerably. I'm using a solid-state rectifier but want to move to tube 5AR4 and then move further up to get better sq.
I have few doubts can anyone clarify on them please.
I have used common toroidal and r core transformer for the tube preamplifier and found many issues when using solid-state bridge blocks etc.
So do we need to use independent transformers for B+ and Heaters?
If so which type of transformers to be used for B+ and which type for Heaters?
Secondly my observations towards using just choke for filtering improved the sound quality considerably. I'm using a solid-state rectifier but want to move to tube 5AR4 and then move further up to get better sq.
I have few doubts can anyone clarify on them please.
I have used common toroidal and r core transformer for the tube preamplifier and found many issues when using solid-state bridge blocks etc.
So do we need to use independent transformers for B+ and Heaters?
If so which type of transformers to be used for B+ and which type for Heaters?
