Filament cap is this one connected (+) to 475R .
Normaly with 0.6V on T 5,6 to ground cathodes = both filaments must glow.
Attachments
Kevin, did you try replacing that filament cap with another cap just to verify it is not the problem?
With my channel imbalance, I swapped the JFETs between channels and problem remains....AC at T8 is 11-12mV while AC at T7 is 12-13mV. I don't know what voltages I should be seeing either side of the 1K resister feeding the gate of Q1 or what voltages I should be seeing at R1 for Q2. I did see .75v DC on the physical right side of R1 in both channels but I didn't test any further.....dinner time.
With my channel imbalance, I swapped the JFETs between channels and problem remains....AC at T8 is 11-12mV while AC at T7 is 12-13mV. I don't know what voltages I should be seeing either side of the 1K resister feeding the gate of Q1 or what voltages I should be seeing at R1 for Q2. I did see .75v DC on the physical right side of R1 in both channels but I didn't test any further.....dinner time.
Glad you found it! Builders flub, we’ve all done it. Literally one second before I powered up my m2 I noticed the big c3 cap was backwards. Who knows what might’ve gone out with that. Your B1 is up and running, enjoy the music!
Kevin,
Glad you found the problem.
A quick question; is there any specific location either input side or output side that you have to install the four matched Q1 Q2 Jfet sets or can any set go in any location?
Thanks. Nash
It would appear that they're tightly matched enough that any one in the bag labeled Q1 could go in any hole labled JQ1...and so forth.
You indicated
upper left = 6.4
upper right = 2.3
lower left = 6.5
lower right = 2.4
which would mean JQ1 is 6.4 and 6.5 and Q2 would be 2.3 and 2.4 or is it the other way around?
Thanks.
Great job Kevin!
I am still having trouble with mine and now I'm really scratching my head. I swapped Q1 and 2, R1 and the 1K gate resistor between channels and the right channel is still lower in level than the left. I am getting identical AC voltage out of A1 and A2 on the Nutube.
I didn't yet check the 100ohm F+ resistor because it feeds both input and output JFETS and the problem is only on the output side. Could the output cap be causing a tiny voltage drop upstream at T8? What about the 100ohm output resistor? Could the RCA jacks be causing a 1mV drop in voltage? I am testing without an amp connected, just measuring either at the test points or at the euroblocks, but with the jacks still wired in.
Without an amp connected could I take out the output cap, and both output resistors and test it safely? Actually if I take the cap out, the circuit breaks there and the resistors are out of the circuit anyway...
I am still having trouble with mine and now I'm really scratching my head. I swapped Q1 and 2, R1 and the 1K gate resistor between channels and the right channel is still lower in level than the left. I am getting identical AC voltage out of A1 and A2 on the Nutube.
I didn't yet check the 100ohm F+ resistor because it feeds both input and output JFETS and the problem is only on the output side. Could the output cap be causing a tiny voltage drop upstream at T8? What about the 100ohm output resistor? Could the RCA jacks be causing a 1mV drop in voltage? I am testing without an amp connected, just measuring either at the test points or at the euroblocks, but with the jacks still wired in.
Without an amp connected could I take out the output cap, and both output resistors and test it safely? Actually if I take the cap out, the circuit breaks there and the resistors are out of the circuit anyway...
A bit confused here. NP says "For J113 parts, the Idss of Q1 is set to be equal to current through Q2" . Since R1 is source degenerating Q2 then Q2 should be the higher value so that after degenerating it matches Q1, so JQ1 should be 2.3 and Q2 6.5.
Using an AVC/TVC at the input
Hi,
I have a Tribute Autoformer Volume control not currently installed anywhere. The Tribute inductive volume control has a DC resistance of only 33 ohms...
If I wanted to use this instead of the 50k pot specified, can I bypass the input buffer? What about the 10uF cap connected to the "grid" of the NuTube? Can this be deleted as well?
Kindest regards,
Chris
Hi,
I have a Tribute Autoformer Volume control not currently installed anywhere. The Tribute inductive volume control has a DC resistance of only 33 ohms...
If I wanted to use this instead of the 50k pot specified, can I bypass the input buffer? What about the 10uF cap connected to the "grid" of the NuTube? Can this be deleted as well?
Kindest regards,
Chris
The Tribute and Slagle AVC are I would like to think similar design concept devices, so I will add a information I was offered yesterday evening.
I had my first audition of a Korg B1 in my home system, the Pre' was kindly brought along by the builder.
After an hour or so of listening to the system, the Slagle AVC was exchanged for the Korg B1, which had not undergone a period of warm up before it was hooked up .
The Korg B1 is a recently completed new build, that has undergone a few tweaks to the components as well as a exchanged off board power supply.
So I will work on the basis that the Korg B1 needs about 100 more hours of play time to completely settle with all the new components to burn in.
In my system, the Korg required about 15 minutes of Playtime, before the real magic come to fruition, I was out of the sweet spot, giving the guests the hottest seats in the listening room.
When the Korg hits its stride, I picked up on it immediately, and it prompted me to suggest a track to be played, I had been familiarising myself with over the Holidays as a new test track.
Within one minute of hearing this track, I made a statement saying that is the most honest steel string guitar I have heard to date.
In my system to pick up on such slight improvements in the SQ has, resulted in my being assured, I have made a very good choice getting on board with the Korg.
As I have at present only requested that my Korg B1 is produced as a working bread board, on revealing this to the builder of the Korg in the system,
a discussion about my build options took place, i.e, how many boxes, the possible need for the electrical thump suppressor ?,
The builder of the Korg, has another Korg B1 project undergoing a build modular build concept where their is a third box being introduced to house dual volume control Pot's, and a thump suppression management.
This then led to my build and a suggestion was made, which may have a relevance to the Tribute AVC as well as my Slagle AVC.
The suggestion was to build a three box design, have the Korg B1 build into its own housing with Input/Output only, and use the Dual Mono Slage AVC in the same method I use it at present to control the volume attached to the inputs of the Korg B1.
It was said, I may require a thump suppression treatment, and I can have the off board Power Supply.
This appeals to me as a initial build, as it will incorporate something old and something new, as well as have a volume control from the AVC and not the Pot's.
The option to listen to the volume control with Pot's will be available, as the other build is to have its own standalone volume control module.
I am not a EE minded individual, so can only say the proposal 'struck a chord'
and I feel this is where I would like my base build to take off from.
I had my first audition of a Korg B1 in my home system, the Pre' was kindly brought along by the builder.
After an hour or so of listening to the system, the Slagle AVC was exchanged for the Korg B1, which had not undergone a period of warm up before it was hooked up .
The Korg B1 is a recently completed new build, that has undergone a few tweaks to the components as well as a exchanged off board power supply.
So I will work on the basis that the Korg B1 needs about 100 more hours of play time to completely settle with all the new components to burn in.
In my system, the Korg required about 15 minutes of Playtime, before the real magic come to fruition, I was out of the sweet spot, giving the guests the hottest seats in the listening room.
When the Korg hits its stride, I picked up on it immediately, and it prompted me to suggest a track to be played, I had been familiarising myself with over the Holidays as a new test track.
Within one minute of hearing this track, I made a statement saying that is the most honest steel string guitar I have heard to date.
In my system to pick up on such slight improvements in the SQ has, resulted in my being assured, I have made a very good choice getting on board with the Korg.
As I have at present only requested that my Korg B1 is produced as a working bread board, on revealing this to the builder of the Korg in the system,
a discussion about my build options took place, i.e, how many boxes, the possible need for the electrical thump suppressor ?,
The builder of the Korg, has another Korg B1 project undergoing a build modular build concept where their is a third box being introduced to house dual volume control Pot's, and a thump suppression management.
This then led to my build and a suggestion was made, which may have a relevance to the Tribute AVC as well as my Slagle AVC.
The suggestion was to build a three box design, have the Korg B1 build into its own housing with Input/Output only, and use the Dual Mono Slage AVC in the same method I use it at present to control the volume attached to the inputs of the Korg B1.
It was said, I may require a thump suppression treatment, and I can have the off board Power Supply.
This appeals to me as a initial build, as it will incorporate something old and something new, as well as have a volume control from the AVC and not the Pot's.
The option to listen to the volume control with Pot's will be available, as the other build is to have its own standalone volume control module.
I am not a EE minded individual, so can only say the proposal 'struck a chord'
and I feel this is where I would like my base build to take off from.