Hi,
It is not clear in the last Moglia Hybrid Mu follower where is exactly the added gate stopper resistor in his last v8 shematic for the low Fet ?
Is it in serie with the two face to face diodes as the shematic or is it in parrallel with these diodes ?
The blog talks about a shematic error (the R9 resistor) https://www.bartola.co.uk/valves/2019/02/03/hybrid-mu-follower-aka-gyrator-rev08-pcb-update/
Should not it be also 1K ?
?!
Thanks
It is not clear in the last Moglia Hybrid Mu follower where is exactly the added gate stopper resistor in his last v8 shematic for the low Fet ?
Is it in serie with the two face to face diodes as the shematic or is it in parrallel with these diodes ?
The blog talks about a shematic error (the R9 resistor) https://www.bartola.co.uk/valves/2019/02/03/hybrid-mu-follower-aka-gyrator-rev08-pcb-update/
Should not it be also 1K ?
?!
Thanks
It is as per schematic in the link, I built the board and it works just fine. Value is 330ohms. Determining the right value of R8 to get a the led to indicate properly is a little more annoying.
I use 67ohms for 30mA and I wish the led was a little more 'lively'.
I use 67ohms for 30mA and I wish the led was a little more 'lively'.
There is no error. Prior to v8, R9 is not included. It will work fine without R9, i have built v7. However, it is added in v8 to avoid oscillation for some high gm mosfets eg. BSH111. In the link you posted, the schematic is updated to have R9. I did some minor surgery on my v7 boards to include the gate stopper resistor after some time, just in case.
Thanks, so the first is the good one? 330R is ok ?
Would you think r9 is not needed with a J113 ?? I think it a ok Jfet for an ECC88. Many J113 goes around 15 to 18 mA...
Would you think r9 is not needed with a J113 ?? I think it a ok Jfet for an ECC88. Many J113 goes around 15 to 18 mA...
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I have used BSN20 and CPH3910 without the gate stopper resistor without experiencing oscillation. I honestly think j113 would be fine without r9.
But with the BSH111, there is oscillation. This transistor has been a constant reminder from Moglia regarding oscillation. After i installed the gate stopper resistor, i did not put on the BSH111 again to try because i am very happy with the CPH3910.
But with the BSH111, there is oscillation. This transistor has been a constant reminder from Moglia regarding oscillation. After i installed the gate stopper resistor, i did not put on the BSH111 again to try because i am very happy with the CPH3910.
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Thanks zoom. I want to Mu follower my TDA1541A, but not sure it is sounding better than a CCS or anode coil feeded said a friend...
At least I try to find a fet that have near mA output to try to make it works nearer to SRPP operation, I wonder if a fet that has 10x the mA output vis a vis of the tube... makes the tube really needed, Not so clear when it works push pull and when it is more a follower with finally a dominant silicon... So just in doubt I try to balance the current between the two poles. I wish I had a 5687 with the ecc88.
At least I try to find a fet that have near mA output to try to make it works nearer to SRPP operation, I wonder if a fet that has 10x the mA output vis a vis of the tube... makes the tube really needed, Not so clear when it works push pull and when it is more a follower with finally a dominant silicon... So just in doubt I try to balance the current between the two poles. I wish I had a 5687 with the ecc88.
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