Hi Guys, I've built a 5C1 kind of amp but it seems low powered, with not much volume. Its is quiet ( no buzzes) and very clean until you put a pedal in front of it, then it comes alive but still not really enough volume.
The schematic shows the voltages I'm getting.
Any help and advice much appreciated.
The schematic shows the voltages I'm getting.
Any help and advice much appreciated.
Both the anode voltage and the screen grid voltage of the 6SJ7 are too high, which means the 6SJ7 is hardly passing current.
Looking at the data for the 6SJ7 from one of the RCA Receiving Tube Manuals, I think that the value of the cathode resistor is too high, and the value of the screen grid resistor too low. The cathode resistor should be something like 900 Ohm (but either 820 or 1K will do) and the screen grid resistor should be something like 870K (but 820K will do).
If changing these resistors doesn't help (enough) than probably your 6SJ7 is at the end of its life.
Looking at the data for the 6SJ7 from one of the RCA Receiving Tube Manuals, I think that the value of the cathode resistor is too high, and the value of the screen grid resistor too low. The cathode resistor should be something like 900 Ohm (but either 820 or 1K will do) and the screen grid resistor should be something like 870K (but 820K will do).
If changing these resistors doesn't help (enough) than probably your 6SJ7 is at the end of its life.
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5c1 low volume
Thanks for your reply 😀 , I suspected the voltages were to high but was unsure how to fix it.
I have made the changes you recommended but used an 820k on the grid, and it is much better the caps were burning in at first but it's starting to sound good at mid volumes now. At full volume it breaks up nicely but when a heavy bass note is struck there is some unwanted rattling and some brittle sounding high tones in the back ground if you hold the note. It's coming from the speaker (not the cab) and is separate to the guitar sound.
Can the bass be tuned in a bit better buy changing the 6V6 cathode resistor from 500 ohm to 550 or higher ?
The amp is also very sensitive to even touching the guitar neck is it possible to dampen this?
Thanks again for you help 🙂🙂
Thanks for your reply 😀 , I suspected the voltages were to high but was unsure how to fix it.
I have made the changes you recommended but used an 820k on the grid, and it is much better the caps were burning in at first but it's starting to sound good at mid volumes now. At full volume it breaks up nicely but when a heavy bass note is struck there is some unwanted rattling and some brittle sounding high tones in the back ground if you hold the note. It's coming from the speaker (not the cab) and is separate to the guitar sound.
Can the bass be tuned in a bit better buy changing the 6V6 cathode resistor from 500 ohm to 550 or higher ?
The amp is also very sensitive to even touching the guitar neck is it possible to dampen this?
Thanks again for you help 🙂🙂
I don't think highering the value of the cathode resistor of the 6V6 has an effect on only the bass. I would leave it like it is if I were you.
I don't know what causes the rattling in your speaker so I can't help you with that.
If by sensitive you mean that you hear a 'click' and possible some hum when you touch a metal part of your guitar (like the strings, the bridge, a knob, etc.) than try earthing the amplifier. If it is already earthed through the mains plug, than I don't think that there is something you can do about it (or at least I don't know how).
I don't know what causes the rattling in your speaker so I can't help you with that.
If by sensitive you mean that you hear a 'click' and possible some hum when you touch a metal part of your guitar (like the strings, the bridge, a knob, etc.) than try earthing the amplifier. If it is already earthed through the mains plug, than I don't think that there is something you can do about it (or at least I don't know how).