The Kuartlotron - keantoken's simple error-correction superbuffer

[donovas]

hi ive built this circuit following the layout that was posted by a member and the thing works, and offset is almost zero when the input is shorted. however when its not, the offset is 3.8v both at the output and the input. what could be the cause of this? oscillation?

it seems to play fine, and the sound is marvelously clear. however im missing a lot of drive i am used to and thinking its related to the misbehavior that is the offset.

i should add i did not use bc560C but instead used B... whereas bc550 is C

[keantoken]

It sounds like your DC trimmer may be open or has a bad connection.

[donovas]

Thank you, Keantoken. Yes, I fixed it by omitting the dc trimmer R9 altogether. I neglected to read the whole thread and chose a 5k pot based on the schematic alone.

As for the sound- this is by far the most delicate mid and high freq ive ever heard from a buffer. It seems to add that special something to the sound which makes yoh want to listen more and more, while being so much more transparent than most of my builds in the past that im hearing things ive never heard before.

That being said, id like to try the push pull 8 transistor version you mentioned earlier. I believe it will help with the bass because the current transfer is bipolar. I can always tell the leaning of the bass with single ended circuits and the k buffer is sadly not an exception.

If you could tell me how to go about doing the push pull version id muxh appreciate it.

Do i just mirror the circuit and tie the input and output?

[keantoken]

Glad you like it!

One half probably wouldn't perform as well and one would always dominate over the other. In which case you would get better performance by just omitting the worse half. This is why I didn't go that route. The Kuartlotron is not like an EF stage where both halves need each other in order to approach linearity. You would not get a symmetrical output behavior, but rather something in between a good performing Kuartlotron and a worse performing one.

One thing you could try is to use the BC337-40/327-40. These are slower but more robust transistors. I decided the BC550C/560C were best overall, but the others are also interesting.

[donovas]

If i change the 10k ohm input to gnd to 100k ohm, will it affect the performance much, and what other values should be changed?

Also instead of 22pf of lpf, id like to use the 100pf wima caps i have. Once again what other values should be changed?

[keantoken]

Those will both be fine. 100k input resistance will be more sensitive to the input offset trim, but it is a common input resistance chosen for the Kuartlotron.

[rookiesparks]

Originally Posted by keantoken

Kuartlotron R2 PCB info:

The Kuartlotron R2 is the second PCB after learning from the first one. Improvements were made to solderability, component selection, pads, etc. Simple shunt regulators were added to the board so it could accommodate a variety of input voltages. Side-screw trimmers are now used so that the trimmers can still be accessed when the boards are mounted in a stack.

Short-form instructions:

1: The square pads in the upper left need to be shorted with a solder bridge to use the PCB inductor, unless you want to use a discrete 2uH inductor. No one has felt the need so far. The +10V and -10V vias are not to be used to power other circuits.
2: The resistors marked with an asterisk on the PCB need to be determined based on your input voltage. Included in the Mouser cart are resistors for a range of input voltages:

12V - 68R
13V - 120R
14V-15V - 150R
15V-16V - 196R 1/2W
17V-19V - 332R 1/2W
You can delete from the cart the resistors you don't need.

3: Preferably before installing the trimmers, use a DMM and set them to the values given on the PCB ("set 56R"). You can just omit the trimmers and use resistors of those values between the outer trimmer pads if you don't plan on trimming.
4: You can start trimming if you so choose.

BOMs:
Standard pair:
Access to this page has been denied.
Topscrew trimmer pair:
Access to this page has been denied.
Single board:
Access to this page has been denied.
Single topscrew trimmer:
Access to this page has been denied.


Details and FAQ:

1: Each board is one channel, so you need a pair for stereo.

2: Some quick notes on construction:

a: Component values are shown on the PCB.
b: It accepts screw terminal inputs and outputs and M3 or 6-32 standoffs.

3: Customizations:

a: Input resistance is normally 100k. You can use 10k if you want.
b: Output impedance is set to 47R for driving cables to reduce reflections. If you want lower output impedance you can use 4.7R in place of the 47R resistor.
c: Those who want to use superregulators can use the +10V and -10V vias on the PCB as sense points.

Trimming procedure:

1: Each trimmer should be set to the value indicated on the PCB. This can be done before soldering them.
2: Short the input and adjust R5 so that TP reads half of V+ (5V).
3: Remove short from the input and then adjust the DC trimmer so that input voltage reads 0.
Output offset should now be within 5mV. This generally results from small variances in components and won't reduce performance.
4: Refer to the Kuartlotron webpage for distortion trimming if you have distortion measuring equipment and the inclination.
The Kuartlotron

hi is it possible to use a 24v power supply, if so what value resistors for (asterisk ) on pcb

[keantoken]

1W 520 ohm.

[rookiesparks]

Originally Posted by keantoken

Kuartlotron R2 PCB info:

The Kuartlotron R2 is the second PCB after learning from the first one. Improvements were made to solderability, component selection, pads, etc. Simple shunt regulators were added to the board so it could accommodate a variety of input voltages. Side-screw trimmers are now used so that the trimmers can still be accessed when the boards are mounted in a stack.

Short-form instructions:

1: The square pads in the upper left need to be shorted with a solder bridge to use the PCB inductor, unless you want to use a discrete 2uH inductor. No one has felt the need so far. The +10V and -10V vias are not to be used to power other circuits.
2: The resistors marked with an asterisk on the PCB need to be determined based on your input voltage. Included in the Mouser cart are resistors for a range of input voltages:

12V - 68R
13V - 120R
14V-15V - 150R
15V-16V - 196R 1/2W
17V-19V - 332R 1/2W
You can delete from the cart the resistors you don't need.

3: Preferably before installing the trimmers, use a DMM and set them to the values given on the PCB ("set 56R"). You can just omit the trimmers and use resistors of those values between the outer trimmer pads if you don't plan on trimming.
4: You can start trimming if you so choose.

BOMs:
Standard pair:
Access to this page has been denied.
Topscrew trimmer pair:
Access to this page has been denied.
Single board:
Access to this page has been denied.
Single topscrew trimmer:
Access to this page has been denied.


Details and FAQ:

1: Each board is one channel, so you need a pair for stereo.

2: Some quick notes on construction:

a: Component values are shown on the PCB.
b: It accepts screw terminal inputs and outputs and M3 or 6-32 standoffs.

3: Customizations:

a: Input resistance is normally 100k. You can use 10k if you want.
b: Output impedance is set to 47R for driving cables to reduce reflections. If you want lower output impedance you can use 4.7R in place of the 47R resistor.
c: Those who want to use superregulators can use the +10V and -10V vias on the PCB as sense points.

Trimming procedure:

1: Each trimmer should be set to the value indicated on the PCB. This can be done before soldering them.
2: Short the input and adjust R5 so that TP reads half of V+ (5V).
3: Remove short from the input and then adjust the DC trimmer so that input voltage reads 0.
Output offset should now be within 5mV. This generally results from small variances in components and won't reduce performance.
4: Refer to the Kuartlotron webpage for distortion trimming if you have distortion measuring equipment and the inclination.
The Kuartlotron

hi can you help, i have shorted the signal inputs and and measured (tp) and it read about 8v and adjusted (r5)to 5v i have now removed shorted input........what i would like to know is how to adjust the dc trimmer ? is that r1 or r5 ??the off set reads .8v

[rookiesparks]

oops ,,,,i seem to of worked it out myself, will have to get a 5m trimmer instead of a fixed 2.7m resistor,