Thought this might be of interest.
I calculated the low frequency roll-off for My Precision1 input capacitor, and included my Valve preamps output coupling/blocking capacitor in the calculation. I used AT's formula where 90ms - F=1.8Hz
My preamp cap is an Auricap 3.3uf, but measures 3.8uF. Using an input cap of 10 uF (BG N) on the precision 1, with it's 15K ohms input impedance, the low frequency -3db point works out at 0.826 hz.
For an input cap of 100uF the frequency is 1.1 hz.
for a cap of 0.22 uF it is 0.06 hz.
For two caps in series Ct = C1 x C2
-----------
C1 + C2
I think my calculation is correct, but I would not bet on it.
My Perreaux amp ,which also has an input loading resistor of 15K ohms, has a 6uF cap ,and rolls off at 0.7 hz, according to my calculation.
billabong
I calculated the low frequency roll-off for My Precision1 input capacitor, and included my Valve preamps output coupling/blocking capacitor in the calculation. I used AT's formula where 90ms - F=1.8Hz
My preamp cap is an Auricap 3.3uf, but measures 3.8uF. Using an input cap of 10 uF (BG N) on the precision 1, with it's 15K ohms input impedance, the low frequency -3db point works out at 0.826 hz.
For an input cap of 100uF the frequency is 1.1 hz.
for a cap of 0.22 uF it is 0.06 hz.
For two caps in series Ct = C1 x C2
-----------
C1 + C2
I think my calculation is correct, but I would not bet on it.
My Perreaux amp ,which also has an input loading resistor of 15K ohms, has a 6uF cap ,and rolls off at 0.7 hz, according to my calculation.
billabong
My thinking on input caps (and please tell me if it's suspect) is that it really shouldn't matter the value of the cap, as long as it satisfies three requirements: 1) it filters signals below the audible range; 2) blocks DC effectively (which are really both the same task); and 3) works with, or at least doesn't interfere with, the rest of the amplifier circuits.
Since DC is logarithmically impossible in terms of signal frequency (to reasonable decimal places), practically any input cap should handle blocking DC.
My expectation for #1 is that attenuating signals beginning at different points below the normal audible limit (say 20 Hz for argument) shouldn't make any sonic difference. Apparently it does according to Nordic. Why more bass when filtering at .5 Hz rather than filtering at 5 Hz? Why does altering this roll-off point upset the balance of the bass/treble response? That's a curiosity to me.
What else is changing to make that sound difference? Or is it ill-perceived? Hmm... I will be experimenting with this curiosity.
This thinking is what lead to my original question to Carlos about the value required for rolling off about 5Hz. It's well below audible range, but will still block DC. (I'm not concerned about rumble, since my sources are all digital.) I wanted the cap value to be audibly irrelevant -- even to babies -- and why not?
..Todd
Since DC is logarithmically impossible in terms of signal frequency (to reasonable decimal places), practically any input cap should handle blocking DC.
My expectation for #1 is that attenuating signals beginning at different points below the normal audible limit (say 20 Hz for argument) shouldn't make any sonic difference. Apparently it does according to Nordic. Why more bass when filtering at .5 Hz rather than filtering at 5 Hz? Why does altering this roll-off point upset the balance of the bass/treble response? That's a curiosity to me.
What else is changing to make that sound difference? Or is it ill-perceived? Hmm... I will be experimenting with this curiosity.
This thinking is what lead to my original question to Carlos about the value required for rolling off about 5Hz. It's well below audible range, but will still block DC. (I'm not concerned about rumble, since my sources are all digital.) I wanted the cap value to be audibly irrelevant -- even to babies -- and why not?
..Todd
Input caps again. I messed up the calculations in my last post, as I mis-used the formula.
With C in of 4.7uF on the precision1, Z in of 15k, and C out of 3.8uf on my preamp, the correct -3db frequency is just over 5 Hz (31.5ms)
The other values were wrong as well, but I won't bother with them here.
Using a 1uF input cap,as Carlos suggests, on the P1, and the same preamp, gives a -3db roll-off at about 13.5Hz, which would be suitable for turntable use. My phono preamp has filtering in it's input section, so I do not need additional filtering.
Actually, I could omit the P1 input cap altogether. The preamp output coupling cap alone would roll off at 2.79Hz, and the Precision1s sound may be improved without the extra cap.
billabong.
With C in of 4.7uF on the precision1, Z in of 15k, and C out of 3.8uf on my preamp, the correct -3db frequency is just over 5 Hz (31.5ms)
The other values were wrong as well, but I won't bother with them here.
Using a 1uF input cap,as Carlos suggests, on the P1, and the same preamp, gives a -3db roll-off at about 13.5Hz, which would be suitable for turntable use. My phono preamp has filtering in it's input section, so I do not need additional filtering.
Actually, I could omit the P1 input cap altogether. The preamp output coupling cap alone would roll off at 2.79Hz, and the Precision1s sound may be improved without the extra cap.
billabong.
Hi Billabong,
Have you listened to the various values? 10uF/4.7uF/1uF/none
Any audible difference?
..Todd
Have you listened to the various values? 10uF/4.7uF/1uF/none
Any audible difference?
..Todd
jest need to know
Hi Dx and others,
REG: Precision I
My amp is operating quite well, yesterday I had operated for 18hrs in mid volume without any problem or over heat. Sorry, I just need to know few more things now.
My first question is, as I know output transistor E-B must be 500milv or above, if I set it to lower then 500milv, what is the impact will be happens on the amp?
Second question is why used power supply capacitor minimum recommended 48000uf per channel.
Can I construct like this for 48000uf per cannel? +v rail 24000uf and – volt rail 24000uf? So its total 48000uf?
Best regards
Michael
Hi Dx and others,
REG: Precision I
My amp is operating quite well, yesterday I had operated for 18hrs in mid volume without any problem or over heat. Sorry, I just need to know few more things now.
My first question is, as I know output transistor E-B must be 500milv or above, if I set it to lower then 500milv, what is the impact will be happens on the amp?
Second question is why used power supply capacitor minimum recommended 48000uf per channel.
Can I construct like this for 48000uf per cannel? +v rail 24000uf and – volt rail 24000uf? So its total 48000uf?
Best regards
Michael
taj,
Like you, I have not built a DX amp yet. As far as I know, only Nordic has built the DX approved version of the Precision 1, using Nordic's PCBs, and he used a higher +/- 70V supply, with lower than desirable reservoir capacitance. Carlos has only built protype versions, as far as we know. space2000 has built a completely diy version, using different output transistors. His efforts are appreciated, especially his feedback.
Re. your input cap question:
After including my Preamp 3.8uF output coupling capacitor into the calculation, The -3db frequency of Precision1 input cap values you mentioned were:
10uf - 3.85 Hz; 4.7uf - 5.05 Hz; 1uf -13.4 Hz. (these include Preamp Cout of 3.8uf in the calculation).
No input cap on Precision1:
with output coupling/blocking cap on source of 1uf > F = 10.61 Hz.
" " " " " " 6.8uf > F = 2.79 Hz.
You would need to be certain that your source component had a coupling capacitor that will block DC, before omitting the input cap on Precision.
I think it may be risky to omit the input capacitor, since although you might know that the source you are using at the time has an output blocking caoacitor, you may later change to a source that has no output cap. You would need to stick a warning sticker on the Precision1.
billabong.
Like you, I have not built a DX amp yet. As far as I know, only Nordic has built the DX approved version of the Precision 1, using Nordic's PCBs, and he used a higher +/- 70V supply, with lower than desirable reservoir capacitance. Carlos has only built protype versions, as far as we know. space2000 has built a completely diy version, using different output transistors. His efforts are appreciated, especially his feedback.
Re. your input cap question:
After including my Preamp 3.8uF output coupling capacitor into the calculation, The -3db frequency of Precision1 input cap values you mentioned were:
10uf - 3.85 Hz; 4.7uf - 5.05 Hz; 1uf -13.4 Hz. (these include Preamp Cout of 3.8uf in the calculation).
No input cap on Precision1:
with output coupling/blocking cap on source of 1uf > F = 10.61 Hz.
" " " " " " 6.8uf > F = 2.79 Hz.
You would need to be certain that your source component had a coupling capacitor that will block DC, before omitting the input cap on Precision.
I think it may be risky to omit the input capacitor, since although you might know that the source you are using at the time has an output blocking caoacitor, you may later change to a source that has no output cap. You would need to stick a warning sticker on the Precision1.
billabong.
Michael,
You really should read more of the thread, as your questions have been thoroughly covered.
Anyway to answer your questions:
VBE - you are correct that Carlos says not to go below 500mv.
So, do not go below 500mv - believe Carlos, as nothing good will happen.
Batween 500mv and 580mv is ok. 500mv is better than 590 or 600mv. The "magic" number is 575mv. Do not go above 640mv.
Supply capacitance: 47000uF per channel (23500uF per rail) will be ok. I am going to use that and I would not use less than that. I think it is about right for 8 ohm speakers, but 4 ohm speakers could use more capacitance, I feel.
billabong.
You really should read more of the thread, as your questions have been thoroughly covered.
Anyway to answer your questions:
VBE - you are correct that Carlos says not to go below 500mv.
So, do not go below 500mv - believe Carlos, as nothing good will happen.
Batween 500mv and 580mv is ok. 500mv is better than 590 or 600mv. The "magic" number is 575mv. Do not go above 640mv.
Supply capacitance: 47000uF per channel (23500uF per rail) will be ok. I am going to use that and I would not use less than that. I think it is about right for 8 ohm speakers, but 4 ohm speakers could use more capacitance, I feel.
billabong.
Michael,
I forgot that you are using different output transistors, so I do not know if your VBEs would necessarily be the same. You would need to compare the data sheets.
I think Carlos has lost interest in the Precision1, and Nordic and DX have parted company, so basically you and the rest of us may be on our own now.
Anyway, since your amp uses different parts, it is a different, although similar, amplifier, You might be better off getting the correct output transistors, so you can use the data Carlos has published.
billabong.
I forgot that you are using different output transistors, so I do not know if your VBEs would necessarily be the same. You would need to compare the data sheets.
I think Carlos has lost interest in the Precision1, and Nordic and DX have parted company, so basically you and the rest of us may be on our own now.
Anyway, since your amp uses different parts, it is a different, although similar, amplifier, You might be better off getting the correct output transistors, so you can use the data Carlos has published.
billabong.
taj,
Correction to post 1186 - too late to edit.
No input cap on Precision1:
With output coupling/blocking cap on source of 1uf > F = 10.61 Hz
----3.8uf > F = 2.79 Hz. ( I incorrectly had 6.8uf instead of the correct 3.8uf)
billabong.
Correction to post 1186 - too late to edit.
No input cap on Precision1:
With output coupling/blocking cap on source of 1uf > F = 10.61 Hz
----3.8uf > F = 2.79 Hz. ( I incorrectly had 6.8uf instead of the correct 3.8uf)
billabong.
about Prs-i
hi,
i just want to say i am using it for my very own. i am telling that its sound great, there is no question. add equalizer to get nice balanced sound from it. Very strong bass with hi fidelity and treble is strong sweet too.....pls do not use 2sc5200 on this, I have tested on it and found sound is flat with 2sc5200, not interesting at all. When I used 2sc2922 original transistor.....It really can say nice and sweet sound so clear treble I ever heard....very details, I want to kiss Carlos chick.....I am now listing too.....i just like the sound quality.
My uncle even asked me to make for him same as mine.....he too listened and says its really beautiful sound . pls make it using 2sc2922 and listen the quality as I said.
my speaker is not that kind of good still sound good....i am going to make a speaker 12 inch two each box....
still waiting for proper guidance...
thanks...
hi,
i just want to say i am using it for my very own. i am telling that its sound great, there is no question. add equalizer to get nice balanced sound from it. Very strong bass with hi fidelity and treble is strong sweet too.....pls do not use 2sc5200 on this, I have tested on it and found sound is flat with 2sc5200, not interesting at all. When I used 2sc2922 original transistor.....It really can say nice and sweet sound so clear treble I ever heard....very details, I want to kiss Carlos chick.....I am now listing too.....i just like the sound quality.
My uncle even asked me to make for him same as mine.....he too listened and says its really beautiful sound . pls make it using 2sc2922 and listen the quality as I said.
my speaker is not that kind of good still sound good....i am going to make a speaker 12 inch two each box....
still waiting for proper guidance...
thanks...
Thanks billabong.
I'm not so curious about the values and F3 shoulders as they are all theoretically fine. But I am very curious to know if they have a sonic difference. Keep that in mind and if you get a chance to experiment with those values after your P1 is built, and I certainly hope you do since it's so simple to swap this cap, let us know your thoughts. I will certainly be doing that.
I am very much in agreement with Carlos that the numbers themselves are a lower priority than the sound.
But when the theory and the sonic results contradict each other, I tend to suspect an error exists somewhere. I also agree with Carlos that human error is very common: Wiring errors, math errors, errors of judgement. It's a minefield.
..Todd
I'm not so curious about the values and F3 shoulders as they are all theoretically fine. But I am very curious to know if they have a sonic difference. Keep that in mind and if you get a chance to experiment with those values after your P1 is built, and I certainly hope you do since it's so simple to swap this cap, let us know your thoughts. I will certainly be doing that.
I am very much in agreement with Carlos that the numbers themselves are a lower priority than the sound.
But when the theory and the sonic results contradict each other, I tend to suspect an error exists somewhere. I also agree with Carlos that human error is very common: Wiring errors, math errors, errors of judgement. It's a minefield.
..Todd
That you will need to experience for yourself.
But whether there is a sonic difference, we have the answer when Andrew said he could tell the difference. Whether such low frequencies, which are felt, rather than heard, benefits sound quality, is another matter - I think perhaps not.
A good reason to stay away from hospitals.
In diy, patience can reward you in far fewer mistakes. Work carefully, which takes time and do not work when tired.
billabong.
Not the condenser type by itself, or brand, but the value can make huge
diference.
The Precision I sounds a little bit boomy, has very strong bass...speaker wants to move into the floor.... also you have treble, but the perceived ratio is different.
Those strange things folks...measuring, it is flat...but listening, it has a lot of bass....so...numbers and audibility are different.
The correct value into the input condenser, in special, can reduce bass..... this will happens in level.... we can produce a roll off into 30 hertz..... or choice another -3dB point.... considered flat when you think in numbers... the plus and less 3 dB points.
When you make that, you will reduce power waste into subsonics .... the amplifier will work more cool and the treble will be perceived as normal..... you gonna perceive as less 3db into the bass and plus 3dB into the treble...and this is normal...considered flat.
Observe, and i would like to call your attention to that:
You can have flat amplifiers that do not sounds flat...not only the speaker or environment, or acoustics...there's "something" i have not discovered, and this makes amplifiers sounds very different one compared to the other.
The HRII is hell loud and clear into the trebles...but try to measure....it is FLAT!
The Dx Standard is the nigthmare, the thunderstorm, the earthquake...but it is also flat!
This is the main reason why i do not bother with numbers....they do not reflect the reality, or at least, not preciselly.
There are som very low THD and IHD amplifiers that sounds awfull!...and others, bad to measure, that sounds great!
So....in my mind, the subjective evaluation, your, personall evaluation...and your, personall speaker adjustment.... your, personall home acoustic care is the needed thing, and the most valuable thing.
regards,
Carlos
diference.
The Precision I sounds a little bit boomy, has very strong bass...speaker wants to move into the floor.... also you have treble, but the perceived ratio is different.
Those strange things folks...measuring, it is flat...but listening, it has a lot of bass....so...numbers and audibility are different.
The correct value into the input condenser, in special, can reduce bass..... this will happens in level.... we can produce a roll off into 30 hertz..... or choice another -3dB point.... considered flat when you think in numbers... the plus and less 3 dB points.
When you make that, you will reduce power waste into subsonics .... the amplifier will work more cool and the treble will be perceived as normal..... you gonna perceive as less 3db into the bass and plus 3dB into the treble...and this is normal...considered flat.
Observe, and i would like to call your attention to that:
You can have flat amplifiers that do not sounds flat...not only the speaker or environment, or acoustics...there's "something" i have not discovered, and this makes amplifiers sounds very different one compared to the other.
The HRII is hell loud and clear into the trebles...but try to measure....it is FLAT!
The Dx Standard is the nigthmare, the thunderstorm, the earthquake...but it is also flat!
This is the main reason why i do not bother with numbers....they do not reflect the reality, or at least, not preciselly.
There are som very low THD and IHD amplifiers that sounds awfull!...and others, bad to measure, that sounds great!
So....in my mind, the subjective evaluation, your, personall evaluation...and your, personall speaker adjustment.... your, personall home acoustic care is the needed thing, and the most valuable thing.
regards,
Carlos
Very good post Carlos. All you say is very true.
I hope you can help us out here occasionally, as we begin to build the Precision I. Hope we (me) do not take too long in doing so, as your patience may wear thin, I think.
I think you might agree with the following:
Numbers are necessary but are only a guide, a starting point.
Then comes the listening evaluation and subsequent refinement, to arrive at a finished product that will sound good.
As has been shown for decades now, good measurements do not necessarily result in good sound.
billabong.
I hope you can help us out here occasionally, as we begin to build the Precision I. Hope we (me) do not take too long in doing so, as your patience may wear thin, I think.
I think you might agree with the following:
Numbers are necessary but are only a guide, a starting point.
Then comes the listening evaluation and subsequent refinement, to arrive at a finished product that will sound good.
As has been shown for decades now, good measurements do not necessarily result in good sound.
billabong.
Yes,
let's just screw up the frequency reponse of the amplifier to attempt to correct for speakers with a poor choice of location or Q or any other substandard characteristic.
let's just screw up the frequency reponse of the amplifier to attempt to correct for speakers with a poor choice of location or Q or any other substandard characteristic.
Hi Andrew,
Two schools of thought here. I have to agree with Billabong on this one. Technical perfection-- and a lot of amps etc come pretty close -- means little if at the end of the day you don't for whatever reason enjoy the listening experience.
An F1 car may be technically superior to any road car, but I am sure you would not want to pop down to the shops in one 🙂
Not a very good example true.
What about a musical instrument. The concert pianist or the classical violinist will choose purely on the basis of sound and "feel". They don't care that their choice has some measured technical imperfection. It's how it sounds.
For me, if an amp is "approaching perfection" in all measurements, and yet the musical result is less than perfect it has failed.
Don't think we will ever agree on this one 🙂
Can I ask Andrew, and I don't know what you listen to at home, but do you find that a lot of the designs presented here do sound "similar".
I should also add this in no way reflects on any of Carlos's work as I have not built or heard one of his designs.
I really think the ear likes a bit of imperfection (providing it is the right sort)
Karl
Two schools of thought here. I have to agree with Billabong on this one. Technical perfection-- and a lot of amps etc come pretty close -- means little if at the end of the day you don't for whatever reason enjoy the listening experience.
An F1 car may be technically superior to any road car, but I am sure you would not want to pop down to the shops in one 🙂
Not a very good example true.
What about a musical instrument. The concert pianist or the classical violinist will choose purely on the basis of sound and "feel". They don't care that their choice has some measured technical imperfection. It's how it sounds.
For me, if an amp is "approaching perfection" in all measurements, and yet the musical result is less than perfect it has failed.
Don't think we will ever agree on this one 🙂
Can I ask Andrew, and I don't know what you listen to at home, but do you find that a lot of the designs presented here do sound "similar".
I should also add this in no way reflects on any of Carlos's work as I have not built or heard one of his designs.
I really think the ear likes a bit of imperfection (providing it is the right sort)
Karl
AndrewT wrote:
Andrew, are you implying that high fidelity amplifier designers screw up the frequency response in order to achieve better sound?
I cannot think of even one amplifier designed in such a way.
Can you give us an example of what you speak?
Carlos has stated that his DX amplifiers measure with a flat frequency response, so you can exclude them from your example.
billabong.
Andrew, are you implying that high fidelity amplifier designers screw up the frequency response in order to achieve better sound?
I cannot think of even one amplifier designed in such a way.
Can you give us an example of what you speak?
Carlos has stated that his DX amplifiers measure with a flat frequency response, so you can exclude them from your example.
billabong.
A simple example is using a small two way speaker in a box deliberately made too small to raise the Q of the speaker above "Butterworth" and produce a hump in the frequency response.
These speakers generally are very intolerant of placement near room boundaries due to the exceesive upper bass they produce which usually makes most male spoken voice sound completely wrong.
Combine a speaker like that with an amplifier with a roll off that starts in the upper bass and it in part compensates the high Q of the speaker and makes the speaker sound better in typical listening rooms.
I suggest the amp should be wide band and the speaker should be designed to match the room.
I further suggest that many speakers are designed that way to give the impression that the small box has adequate bass.
To be able to sell amplifiers to this market, many astute amplifier designers will deliberately tailor their amps to suit the predominant speakers they have to drive.
The amp businesses that didn't would simply go out of business.
We know from our DIY speaker threads how to make proper bass speakers and this generally means bigger boxes.
To drive these we should not be buggering up the frequency response of the DIY amplifier, instead, make sure your flat amp and speaker are well matched to the listening room.
These speakers generally are very intolerant of placement near room boundaries due to the exceesive upper bass they produce which usually makes most male spoken voice sound completely wrong.
Combine a speaker like that with an amplifier with a roll off that starts in the upper bass and it in part compensates the high Q of the speaker and makes the speaker sound better in typical listening rooms.
I suggest the amp should be wide band and the speaker should be designed to match the room.
I further suggest that many speakers are designed that way to give the impression that the small box has adequate bass.
To be able to sell amplifiers to this market, many astute amplifier designers will deliberately tailor their amps to suit the predominant speakers they have to drive.
The amp businesses that didn't would simply go out of business.
We know from our DIY speaker threads how to make proper bass speakers and this generally means bigger boxes.
To drive these we should not be buggering up the frequency response of the DIY amplifier, instead, make sure your flat amp and speaker are well matched to the listening room.
- Status
- Not open for further replies.