CS8412 locking?
When can I be asured that cs8412 is properly locking signal?
I checked pins 25(ERF) and 25 (VERF) , both changing from High to Low- is signal locked then ?
I also observed pin2 (Cd/F1)changing from High to Low ( Sel=1)
pin14(User data output) changing value from 0V to 0.5V
pin20(Filter)- from 0V to 0.5V
When can I be asured that cs8412 is properly locking signal?
I checked pins 25(ERF) and 25 (VERF) , both changing from High to Low- is signal locked then ?
I also observed pin2 (Cd/F1)changing from High to Low ( Sel=1)
pin14(User data output) changing value from 0V to 0.5V
pin20(Filter)- from 0V to 0.5V
Seems like I am writing to myself , but I ask again : how (what pins shouls I check) to confirm CS8412 is locking signal ?
Anybody, please.
Anybody, please.
Well, if you are using ECC88 tube output schematics as in post #11 I advise to try higher value (100R) cathode resistors.
CS8412 is locked when ERF (pin 25) goes low "0". So it seems you have a lock.
TDA1541A outputs have approx. 2mA bias current, so the voltage drop across 47R would be around 0.02 * 47 = 0.94V (no tube output connected). So the voltages you measured seem to be OK.
CS8412 is locked when ERF (pin 25) goes low "0". So it seems you have a lock.
TDA1541A outputs have approx. 2mA bias current, so the voltage drop across 47R would be around 0.02 * 47 = 0.94V (no tube output connected). So the voltages you measured seem to be OK.
Thank You for reply , I will try different biasing of ECC88.
There is another thing which worries me , pin2 going from High to Low when Sel=High.
Anyway what is a reason everybody set pin SEL= High?
There is another thing which worries me , pin2 going from High to Low when Sel=High.
Anyway what is a reason everybody set pin SEL= High?
SEL = "1" channel status information on the 6 channel status output bits
SEL = "0" error and frequency (source) information on the 6 channel status output bits.
SEL = "0" error and frequency (source) information on the 6 channel status output bits.
Played little with anode voltage and finally I am getting some sound out of DAC, but on very low level and accompanied by a lot of noise .Touching both RCA cables (2 seperate runs of Stereovox) brings some distortion and sometimes music to normal level.
Wonder where to look next.
Wonder where to look next.
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Seems the tube output circuit is oscillating (no grid stopper resistor). Try to insert approx. 1K Ohm resistor between ECC88 tube grid (pin 2 and 7) and 47nF / 47 Ohm junction.
I attached the modified schematic for reference. When the circuit functions you can fine-tune the 100R resistor for best linearity. Use ECC88 plate characteristics for this, datasheet can be found here:
JJ Electronic ECC88 (datasheet) | High Fidelity Tubes
JJ Electronic ECC88 (datasheet) | High Fidelity Tubes
Attachments
To make think worse my soldering iron just gave-up,
Thank you -ecdesigns- for help, I will try grid stoppers.
There is another concern , as looking for error I changed grounding few times and at the moment is pretty mixed-up.
Ground from Mains, transformer shields,"-"from Anode PSU, leg9 from ecc88, "-" from Heaters PSU and ground from DAC are connected to chassis in one common point.
Ground on DAC is made as follow:
1.analog ground bus under TDA1541 with all 0u1 caps connected to,
2."+" from -5V and -15V PSU's,
Pin DGND from TDA1541,
Pin DGND from CS8412,
I/V resistor and output stage,
connected to this bus at one common point,
3."-" From Digital +5V PSU connected to DGND pin -CS8412
4."-" From Analog +5V PSU connected to AGDN pin CS8412
Digital +5V PSU is common for TDA1541 and CS8412.
Thank you -ecdesigns- for help, I will try grid stoppers.
There is another concern , as looking for error I changed grounding few times and at the moment is pretty mixed-up.
Ground from Mains, transformer shields,"-"from Anode PSU, leg9 from ecc88, "-" from Heaters PSU and ground from DAC are connected to chassis in one common point.
Ground on DAC is made as follow:
1.analog ground bus under TDA1541 with all 0u1 caps connected to,
2."+" from -5V and -15V PSU's,
Pin DGND from TDA1541,
Pin DGND from CS8412,
I/V resistor and output stage,
connected to this bus at one common point,
3."-" From Digital +5V PSU connected to DGND pin -CS8412
4."-" From Analog +5V PSU connected to AGDN pin CS8412
Digital +5V PSU is common for TDA1541 and CS8412.
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Low level of output signal
Finally got it working🙂🙂🙂 , I stayed with 10R cathode resistor , added grid stoppers and tube is working fine under following condition:
Plate voltage:75V
Cathode-Grid voltage: 0.27V
Plate curent:~15mA
Grid stoppers as adviced: 1k
I also re-arranged (once again) grounding layout.
Only worrying thing is low level of output signal , DAC hardly runs my amplifier - anyway to imrove it?
Finally got it working🙂🙂🙂 , I stayed with 10R cathode resistor , added grid stoppers and tube is working fine under following condition:
Plate voltage:75V
Cathode-Grid voltage: 0.27V
Plate curent:~15mA
Grid stoppers as adviced: 1k
I also re-arranged (once again) grounding layout.
Only worrying thing is low level of output signal , DAC hardly runs my amplifier - anyway to imrove it?
What is your i/v resistance? increase the i/V resistor value can increase the output voltage.
For 2x TDA1541A: Max value 60 ohm.
For 1x TDA1541A: Max value 90 ohm.
Info from Lampizator.
By the way, what is the voltage output rms of your output stage?
For 2x TDA1541A: Max value 60 ohm.
For 1x TDA1541A: Max value 90 ohm.
Info from Lampizator.
By the way, what is the voltage output rms of your output stage?
Hi slav,
TDA1541A full scale output current equals 4mA, so a 47R resistor and a single TDA1541A produces 0.004 * 47 = 188mVpp, with 2 x TDA1541A this amplitude doubles. Keep in mind that there is a limit to the ac voltage on the DAC output. In the datasheet it's specified as output compliance and it equals 50mVpp max. Exceeding this limit by a small margin doesn't lead to unacceptable THD, but above certain threshold the THD really starts to rise to unacceptable levels leading to distorted sine wave shape (clipping).
With 90R passive I/V resistor and a single TDA1541A, signal amplitude would be 0.004 * 90 = 360mVpp. I can guarantee you that this will introduce unacceptable high distortion. This can be easily verified by using a 1 KHz 0dB sine wave test track and observe the signal across the 90 Ohm passive I/V resistor.
Based on measurements I would recommend max. 33 Ohm passive I/V resistor value for a single TDA1541A.
Assuming your power amp would require 1V rms (2.82Vpp) for full power, tube amp gain would have to be 2.82 / 0.188 = 15x.
Grounded cathode tube amplifier is discussed here:
A little history and theory
TDA1541A full scale output current equals 4mA, so a 47R resistor and a single TDA1541A produces 0.004 * 47 = 188mVpp, with 2 x TDA1541A this amplitude doubles. Keep in mind that there is a limit to the ac voltage on the DAC output. In the datasheet it's specified as output compliance and it equals 50mVpp max. Exceeding this limit by a small margin doesn't lead to unacceptable THD, but above certain threshold the THD really starts to rise to unacceptable levels leading to distorted sine wave shape (clipping).
With 90R passive I/V resistor and a single TDA1541A, signal amplitude would be 0.004 * 90 = 360mVpp. I can guarantee you that this will introduce unacceptable high distortion. This can be easily verified by using a 1 KHz 0dB sine wave test track and observe the signal across the 90 Ohm passive I/V resistor.
Based on measurements I would recommend max. 33 Ohm passive I/V resistor value for a single TDA1541A.
Assuming your power amp would require 1V rms (2.82Vpp) for full power, tube amp gain would have to be 2.82 / 0.188 = 15x.
Grounded cathode tube amplifier is discussed here:
A little history and theory
Hi
Having problem again , this time with high dc offset appearing on RCA while switching on and off. Voltage on sockets rises to +60V then goes to -10V and after around 10 sec. settles at 25mV. Could it be multimeter ?
Having problem again , this time with high dc offset appearing on RCA while switching on and off. Voltage on sockets rises to +60V then goes to -10V and after around 10 sec. settles at 25mV. Could it be multimeter ?
No, you choose tubes and this is IMO normal with tubes. It is normal with semiconductors too but not such high voltages. That is why muting relays are a must when working with tubes. You don't want that kind of offset on the inputs of your (pre)amp. Just think of accidentally having the volume a bit up when switching on your DAC. Ouch !
So please think of implementing a simple muting circuit with a relay connecting signals to GND and releasing after a second or 10. The muting circuit as used in the DCB1/Mezmerize/Hypnotize is a nice one. Don't make the same error by switching the output and thus having the contacts in the signal path, it is better to short the output to GND and releasing it after a while. Then the contacts are parallel to the signal path. This could not be done with the mentioned devices for other technical reasons.
BTW did you switch TDA chips already and if so: how does the new one sound ?
So please think of implementing a simple muting circuit with a relay connecting signals to GND and releasing after a second or 10. The muting circuit as used in the DCB1/Mezmerize/Hypnotize is a nice one. Don't make the same error by switching the output and thus having the contacts in the signal path, it is better to short the output to GND and releasing it after a while. Then the contacts are parallel to the signal path. This could not be done with the mentioned devices for other technical reasons.
BTW did you switch TDA chips already and if so: how does the new one sound ?
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Hi, I would not connect signal GND to safety ground directly. I use a 100 Ohm resistor for that. Safety ground is for eh...safety. You don't want to pollute your signal GND with mains noise etc. The case and the transformer shields should be connected directly to safety ground though ( PE ). If you connect signal GND to safety ground directly you will make more problems than you want to solve.
Never understood this technique and never did it like this too but maybe somebody can give a good explanation why connecting signal GND to safety ground is wise choice as I can not find a single benefit. It will make ground loops enter your electronic life.
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Thanks "jean-paul".
As I worked away for last couple of weeks I never had a chance to thank you for TDA1541 you sent me .
Temporarily I have sorted problem by inserting 1k5 resistor between signal output and ground (instead of 1M resistor), but of course I will consider using relay.
speaking of sound of new chip , I am still searching for best working point. So far I use Adagio's output stage but instead anode choke I used resistor, by the way do you know any place to buy decent , but not very expensive plate chokes?
As I worked away for last couple of weeks I never had a chance to thank you for TDA1541 you sent me .
Temporarily I have sorted problem by inserting 1k5 resistor between signal output and ground (instead of 1M resistor), but of course I will consider using relay.
speaking of sound of new chip , I am still searching for best working point. So far I use Adagio's output stage but instead anode choke I used resistor, by the way do you know any place to buy decent , but not very expensive plate chokes?
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