Re: May I jump in?
Konnichiwa,
Thge article states clearly what changes need to be made to the circuit to make it work with DAC's having a output current of 4mA PP for full scale instead of the more common 2mA or less.
Ultimatly selecting the I/V resistor is a choice between too high distortion from the DAC and too low output. You need to select the Resistor apropriatly and design the analogue stage apropriatly.
With 4mA peak-peak current and 100 Ohm I/V resistance you get 400mV peak-peak or 141mV. To get 2V from 141mV we need a gain of around 14. The ECC88 SRPP will have a gain of approximatly Mu/2 where Mu for the ECC88 is 33, so the gain becomes 16.5, so the output level will be a little higher than most normal CD-Players.
If you reduce the I/V resistor further your output voltage will drop unless you increase the gain of the SRPP Stage. If you use an ECC81 whose Mu is closer to 60 you get a gain of 30 and thus you could use a resistor of around 50 ohm.
Please appreciate that those people who post here and provide free help and advise live lives of their own. They are not at your immediate beck and call but will answer when they have time. This may at times take several days, not a few hours.
Sayonara
Konnichiwa,
Andypairo said:
Thge article states clearly what changes need to be made to the circuit to make it work with DAC's having a output current of 4mA PP for full scale instead of the more common 2mA or less.
Ultimatly selecting the I/V resistor is a choice between too high distortion from the DAC and too low output. You need to select the Resistor apropriatly and design the analogue stage apropriatly.
With 4mA peak-peak current and 100 Ohm I/V resistance you get 400mV peak-peak or 141mV. To get 2V from 141mV we need a gain of around 14. The ECC88 SRPP will have a gain of approximatly Mu/2 where Mu for the ECC88 is 33, so the gain becomes 16.5, so the output level will be a little higher than most normal CD-Players.
If you reduce the I/V resistor further your output voltage will drop unless you increase the gain of the SRPP Stage. If you use an ECC81 whose Mu is closer to 60 you get a gain of 30 and thus you could use a resistor of around 50 ohm.
Andypairo said:
Please appreciate that those people who post here and provide free help and advise live lives of their own. They are not at your immediate beck and call but will answer when they have time. This may at times take several days, not a few hours.
Sayonara
Hello Thorsten,
thank you for your help.
I had seen which changes need to be made for a DAC like the TDA1541A, but the I/V resistor value confused me a bit.
Lowering that resistor seems the only way to me (I just bought some Mullard ECC88...
), even if it means a lower output.
This output stage is somewhat an experiment for me to see how can tubes affect the sound and maybe this can be a new start...
Cheers
Andrea
PS Point taken, I didn't want to hurry a reply but rather give more visibility to my question ... if I should do it again
me
thank you for your help.
I had seen which changes need to be made for a DAC like the TDA1541A, but the I/V resistor value confused me a bit.
Lowering that resistor seems the only way to me (I just bought some Mullard ECC88...
), even if it means a lower output.This output stage is somewhat an experiment for me to see how can tubes affect the sound and maybe this can be a new start...
Cheers
Andrea
PS Point taken, I didn't want to hurry a reply but rather give more visibility to my question ... if I should do it again
me
Hi,
Depending on the DAC chip used an I/V resistor of 100-120R should be fine with the ECC88 in SRPP.
Make sure to use a metalfilm resistor of good quality for lowest noise.
Cheers,😉
Depending on the DAC chip used an I/V resistor of 100-120R should be fine with the ECC88 in SRPP.
Make sure to use a metalfilm resistor of good quality for lowest noise.
Cheers,😉
fdegrove said:
The DAC is, as said before, a TDA1541A.
Or do you mean "depending on how good is your TDA1541A?"
BTW is it possible to test if a tube works properly without a tube tester?
Cheers
Andrea
Hi,
No, just the type of DAC. For a TDA1541A a 100R should work fine.
Yes, but most are basically just emission testers.
Cheers,😉
No, just the type of DAC. For a TDA1541A a 100R should work fine.
Yes, but most are basically just emission testers.
Cheers,😉
Hoping not to abuse,
If I should feel the need to squeeze some more gain from the poor ECC88, can you point me to a suitable circuit?
Cheers
Andrea
If I should feel the need to squeeze some more gain from the poor ECC88, can you point me to a suitable circuit?
Cheers
Andrea
Konnichiwa,
Use the same, but connect a large value capacitor (at least 47uF)across the lower cathode resistor. Voila, your gain goes up a little. Otherwise try 12AT7/12AV7/12AZ7, especially the 5965 is underrated and will work well....
Sayonara
Andypairo said:
Use the same, but connect a large value capacitor (at least 47uF)across the lower cathode resistor. Voila, your gain goes up a little. Otherwise try 12AT7/12AV7/12AZ7, especially the 5965 is underrated and will work well....
Sayonara
Well if the gain is too much I can lower the I/V resistor...😀
If the SRPP gain was about 16, this stage gains... ? (yes I don't understand a **** about tubes... but if this project turns out well I promise I'll get a book and will start reading😉...)
Cheers
Andrea
If the SRPP gain was about 16, this stage gains... ? (yes I don't understand a **** about tubes... but if this project turns out well I promise I'll get a book and will start reading😉...)
Cheers
Andrea
Hi,
Simply put:
SRPP mu/2 so 6N1P 33/2 = 16
Mu follower, as the name suggest tracks the mu of the valve more closely so you roughly arrive at mu = 33.
Not IF but WHEN....
Cheers,😉
Simply put:
SRPP mu/2 so 6N1P 33/2 = 16
Mu follower, as the name suggest tracks the mu of the valve more closely so you roughly arrive at mu = 33.
Not IF but WHEN....
Cheers,😉
again on 22uF cap
I came across a couple of 10uF/630V Solen caps, can they suffice or is the capacitance value mandatory?
Cheers
Andrea
Kuei Yang Wang said:
I came across a couple of 10uF/630V Solen caps, can they suffice or is the capacitance value mandatory?
Cheers
Andrea
Re: again on 22uF cap
Konnichiwa,
You can try them, but I'd recommend to stick to my original value. Due to my STRONG preference for non-polar capacitors I usually use the lowest value I feel I an "get away" with. Lower values MAY work, but I do not guarantee it.
Sayonara
Konnichiwa,
Andypairo said:
You can try them, but I'd recommend to stick to my original value. Due to my STRONG preference for non-polar capacitors I usually use the lowest value I feel I an "get away" with. Lower values MAY work, but I do not guarantee it.
Sayonara
To be true I have some russian PIO caps that I could parallel to the Solens to reach the 20uF, the only problem is their size....
Btw for the power supply at the moment I have a 250V trafo (but it measures more like 270V ac), so, using a double RC cell (2k7 + 470 uF) I get it down to about 230V.. is that safe or should I use higher value resistors?
Cheers
Andrea
Btw for the power supply at the moment I have a 250V trafo (but it measures more like 270V ac), so, using a double RC cell (2k7 + 470 uF) I get it down to about 230V.. is that safe or should I use higher value resistors?
Cheers
Andrea
Attachments
Konnichiwa,
If you must recycle junkbox parts, try this:
100uF electrlytic capacitor, then 100R series resistor and the the the best 5-10uF capacitor you have. I would advise against Solens, in the past I found them to give sonic problems.
Sayonara
Andypairo said:To be true I have some russian PIO caps that I could parallel to the Solens to reach the 20uF, the only problem is their size....
If you must recycle junkbox parts, try this:
100uF electrlytic capacitor, then 100R series resistor and the the the best 5-10uF capacitor you have. I would advise against Solens, in the past I found them to give sonic problems.
Sayonara
Konnichiwa,
A hard, unpleasant sound. This may be very well a result of the microphonic behaviour of these capacitors, just sweep one with a nice high level sinewave while applying a few volt bias....
Sayonara
Pedja said:
A hard, unpleasant sound. This may be very well a result of the microphonic behaviour of these capacitors, just sweep one with a nice high level sinewave while applying a few volt bias....
Sayonara
fdegrove said:
Frank
Here
You are showing that mu follower with ECC88
fdegrove said:
And here you are talking about 6N1P. Can I just replace the tube of above schematic with 6N1P (I have loads of them but nil ECC88 or 6N23P)?
Regards,
Argo
Konnichiwa,
In what application and compared to what other options?
I have compared them to the ICW's, Ampohm and Ansars, with the SCR/Solen types coming out poor seconds compared to these. Between Ansar & ICW the race is less clear cut, it often depends upon the specific position, the Ampohm are solidly encased and are best of all these MKP types I came across.
Sayonara
Pedja said:
In what application and compared to what other options?
I have compared them to the ICW's, Ampohm and Ansars, with the SCR/Solen types coming out poor seconds compared to these. Between Ansar & ICW the race is less clear cut, it often depends upon the specific position, the Ampohm are solidly encased and are best of all these MKP types I came across.
Sayonara
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