Hello.
I will add a second channel on my mic preamp.
I want to wire it like that because I don't want to use 2 input transformers (pricey).
I don't know if I created a ground loop, between the "normal channel" and the "low channel" ?
Is it a good way to do it ? If you have any suggestions on a better way please feel free.
Thank you.
EDIT : Do you know if using an ECC81 will be lower noise as the input stage than ECC83 ?
The schematic :
I will add a second channel on my mic preamp.
I want to wire it like that because I don't want to use 2 input transformers (pricey).
I don't know if I created a ground loop, between the "normal channel" and the "low channel" ?
Is it a good way to do it ? If you have any suggestions on a better way please feel free.
Thank you.
EDIT : Do you know if using an ECC81 will be lower noise as the input stage than ECC83 ?
The schematic :
An externally hosted image should be here but it was not working when we last tested it.
What makes the low gain and normal amplifiers differ in gain, the reduction in supply voltage being fed in series? That will surely impact the grid voltages being made the same.
I have a voltage divider after the input stage, and for lower supply I did not even tough about it.
I just wanted to A/B 2 design at once fast, because I always modify my preamps.
Do you think the ground is ok ? No ground loop ? Noise ?
Thank you.
I just wanted to A/B 2 design at once fast, because I always modify my preamps.
Do you think the ground is ok ? No ground loop ? Noise ?
Thank you.
Last edited:
The ground is fine. If you whant to be sure then introduce a small resistor of say 10 ohms into each ground that would drop any stray voltage difference.
Thank you very much.
What would be the best dual triode to use for the best input stage, lowest noise highest signal ratio ?
I was told ecc81 should be avoided because it is more noisy (grid noise) than an ecc83.
What would be the best dual triode to use for the best input stage, lowest noise highest signal ratio ?
I was told ecc81 should be avoided because it is more noisy (grid noise) than an ecc83.
For high gain the 12ax7 is good.
Careful layout and screening is required to keep out noise though.
Transformers are notorious for picking up noise.
Its unusual for a pre-amp to have ground loop because currents are so small.
If the audio ground and power supply ground have got mixed together then the charging impulses into the smoothing cap can cause hum.
Careful layout and screening is required to keep out noise though.
Transformers are notorious for picking up noise.
Its unusual for a pre-amp to have ground loop because currents are so small.
If the audio ground and power supply ground have got mixed together then the charging impulses into the smoothing cap can cause hum.
Thank you I will try to find what tubes are used by you guys on the forum.
I read book samples by merlin blencowe and the ecc83 was better than I thought.
I read book samples by merlin blencowe and the ecc83 was better than I thought.