The original article is from a HP-Journal 1971-02 that can be downloaded here Index of /hpjournal/pdfs/IssuePDFs (you can find a table of content for the site here Index of /hpjournal/pdfs ).
Yes I am quite fond of CFP.
From what I have been reading it is far easier to stabilize and presents superior linearity.
From what I have been reading it is far easier to stabilize and presents superior linearity.
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Finally collected all the parts....
As I am starting to populate the boards tomorrow, I would like to know if I must make space for an output coil.... I know most amps need it in the output to prevent weird behavior... is this the case ?
As I am starting to populate the boards tomorrow, I would like to know if I must make space for an output coil.... I know most amps need it in the output to prevent weird behavior... is this the case ?
I do not use an output coil and had no trouble.
When you use low inductance, high capacitance cable or you drive an electrostatic it may be necessary.
Dynamic speakers usually have some inductance in the treble anyway so a coil is not necessary. I found the Nobrainer is quite stable without a coil.
When you use low inductance, high capacitance cable or you drive an electrostatic it may be necessary.
Dynamic speakers usually have some inductance in the treble anyway so a coil is not necessary. I found the Nobrainer is quite stable without a coil.
Those are very good news.
If I get some trouble due to the speaker cables (not probable because I am using interlaced multy strand kimber cable) I can use a zobel just to stabilize it.
If I get some trouble due to the speaker cables (not probable because I am using interlaced multy strand kimber cable) I can use a zobel just to stabilize it.
You can alway add a coil external if you want and listen what sounds better.
Recently i had an oscillation problem with a VSSA. I really did not like my low inductance ribbon loudspeaker cable and produced an unpleasant high pitched tone. I took a 10 Ohm wire wound resistor and wound 12 windings of stiff solid core cable around it.
I dipped it in wax from a melted candle. That parallel combination of 10 Ohm plus coil solved the problem.
Recently i had an oscillation problem with a VSSA. I really did not like my low inductance ribbon loudspeaker cable and produced an unpleasant high pitched tone. I took a 10 Ohm wire wound resistor and wound 12 windings of stiff solid core cable around it.
I dipped it in wax from a melted candle. That parallel combination of 10 Ohm plus coil solved the problem.
Anyway, i have the Nobrainer amp around, although in balanced form.
I will try it with my low inductance cable.
I will try it with my low inductance cable.
Thank you 🙂
I have been rearranging the layout (once you get the parts you can start figuring out how they fit together....)
Already made some breadboard tests regarding the opamp psu lines... cool.
Can I use a film cap in the input instead of the bipolar EL arrangement ? .... what would the minimum value required ?
I have been rearranging the layout (once you get the parts you can start figuring out how they fit together....)
Already made some breadboard tests regarding the opamp psu lines... cool.
Can I use a film cap in the input instead of the bipolar EL arrangement ? .... what would the minimum value required ?
What opamp are you using ?
If you use a Fet opamp a cap at the input is not necessarily required.
When you set the input impedance to 10kOhm a 4,7uF should be big enough.
You can alternatively rise the input impedance to 47kOhm and take a 1uF.
In recent years the input impedance of Power Amps has come down from 47kOhm to 10kOhm. So the old 47kOhm is the new 10kOhm. Theoretical 10kOhm is more robust to pick up noise.
If you use a Fet opamp a cap at the input is not necessarily required.
When you set the input impedance to 10kOhm a 4,7uF should be big enough.
You can alternatively rise the input impedance to 47kOhm and take a 1uF.
In recent years the input impedance of Power Amps has come down from 47kOhm to 10kOhm. So the old 47kOhm is the new 10kOhm. Theoretical 10kOhm is more robust to pick up noise.
I am going to use LME49710 opamp, so maybe I need the input cap.... strange that my Meridian 101 preamp uses a LME49720 in the input and does not need an input cap.... Anyway, 4u7 seems a reasonable value for the input cap.... I am following your schematic and am planning to use 10kohms for R11 (I believe that will determine input imp...)
Why did you choose two 100u caps resulting in a bipolar 50u ?
Why did you choose two 100u caps resulting in a bipolar 50u ?
I'm using these lovely lovely lovely ... 49710's all over the place and never need input caps (even in my phono) (please go for the metal can version 🙂).
It Ain't Half Hot Mum - My Lovely Boy 2-3 - YouTube
Yes... metal can are even better... so much better (I am using 49720 metal can in that meridian modded pre).
Maybe if I get the psu right I will not need input caps 🙂
Maybe if I get the psu right I will not need input caps 🙂
Well, that Opamp does have input bias cancelation, the NE5534 does not.
When you have a cap in the chain before the power amp you do not need a cap anyway.
A cap is praxis though in commercial amps for protection.
When you use elcaps it is better to use a bigger value or there is risk of rising distortion in the bass. The more voltage develops over the cap the more distortion, see Douglas Self.
When you have a cap in the chain before the power amp you do not need a cap anyway.
A cap is praxis though in commercial amps for protection.
When you use elcaps it is better to use a bigger value or there is risk of rising distortion in the bass. The more voltage develops over the cap the more distortion, see Douglas Self.
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Thank you for the EL explanation... did not know that.... If I decide to go electrolytic, can I use two 47u instead of 100u... I have plenty of those (there is always a compromise 🙂)
Ok.
You can make a fake bipolar by connecting the minus poles together.
That halves the capacitance though so you need 4 to make 47uF again.
Anyway, maybe a foil cap ist better.
You can make a fake bipolar by connecting the minus poles together.
That halves the capacitance though so you need 4 to make 47uF again.
Anyway, maybe a foil cap ist better.
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