Hello Carlos,
is it possible to expand the DX-Amp by a volume attenuator?
In my case the input to the DX-Amp is the line-out of my PC Soundblaster soundcard.
I want to leave the adjustment by software at its maxmimum level and control the volume by ... ?
Can this simply be done by replacing R3 (39K) by a potentiometer?
Which value should the potentiometer have?
Best regards from Hamburg - Rudi
is it possible to expand the DX-Amp by a volume attenuator?
In my case the input to the DX-Amp is the line-out of my PC Soundblaster soundcard.
I want to leave the adjustment by software at its maxmimum level and control the volume by ... ?
Can this simply be done by replacing R3 (39K) by a potentiometer?
Which value should the potentiometer have?
Best regards from Hamburg - Rudi
Re (39K) is for biasing purposes, it connects first transistor base to ground
Cannot be used as volume control.
Watch the schematic attached.... build this way.
R10 (2K2) controls the gain, the amplifier sensitivity, and should not be substituted by a trimpot...not a good idea...but can be tweaked to adjust sensitivity...increasing it your reduce the amplifier gain.... reducing it will increase the gain.
So..if you increase the input volume to the maximum, and also increase your volume into the software to the maximum, and even this way you feel the power is not the maximum (20 volts RMS undistorted), them reduce the resistance value in steps...alike 2K, then 1K8, them 1K5, then 1K2 then 1K and so on)
If you perceive audio from soundblaster boards is too much high for this amplifier sensitivity (750 milivolts RMS to full power), them increase the resistance in steps and listen to see the result.... steps are 2K7,3K3,3K9 and so on.
Of course, you can use a potentiometer to find the good value...but after conclude the good value, remove it, measure with an ohmeter and them install a fixed resistance there.
regards,
Carlos
Cannot be used as volume control.
Watch the schematic attached.... build this way.
R10 (2K2) controls the gain, the amplifier sensitivity, and should not be substituted by a trimpot...not a good idea...but can be tweaked to adjust sensitivity...increasing it your reduce the amplifier gain.... reducing it will increase the gain.
So..if you increase the input volume to the maximum, and also increase your volume into the software to the maximum, and even this way you feel the power is not the maximum (20 volts RMS undistorted), them reduce the resistance value in steps...alike 2K, then 1K8, them 1K5, then 1K2 then 1K and so on)
If you perceive audio from soundblaster boards is too much high for this amplifier sensitivity (750 milivolts RMS to full power), them increase the resistance in steps and listen to see the result.... steps are 2K7,3K3,3K9 and so on.
Of course, you can use a potentiometer to find the good value...but after conclude the good value, remove it, measure with an ohmeter and them install a fixed resistance there.
regards,
Carlos
Attachments
Thank you João.... the race mixing we had here result, sometimes, very interesting
Those are my girls...left one is my daugther in my heart.... she is my wife's daugther... a nice mixing.... Afro-brazilian, Native Indian,Greek, Portuguese, Venezuelan and Spanish blood.
Rigth one is Larissa, my daugther...also another interesting mixing...Afro-brazilian blood,Native Indian,Greek, Portuguese, Dutch, Italian and Spanish.
Girls here result nice..not too much tall...average is 165 centimeters.... not normal to grow above 175 (rarity).... nice strong legs, ligth brown skin (coffee with a lot of milk), beautifull feet, curly hairs (rings with one inch diameter)... strong breasts (smaller than US girls) and many types of eyes...all colours, beeing the Indian Honey colour the most rare colour here..dominant is ligth brown and deep black.
They have some heart problems (usually blood pressure because African Heritage) and use to be alive till 75 years old.
The best they have...i think this is the most important for us...they think we, husbands, are alike king.... early morning they grow up and prepare coffee and clean all stuff for you...they go to work also... they take care from our childrens tenderly, are always worrying about you..ready to serve you in a wonderfull way...they are modern slaves...slaves in her hearts....ready to be good, to be kind, to be protective, to be your mother, your friend and your lover..also they do not use to betray their husbands...this is not acceptable and rarely happens...but men here is alike dog.... sadly men here is not fine.
Germans use to come here and often return with a Brazilian wife...some of them very nice..fall in love really... some others are professionals hunting strangers thinking they are rich (fause idea)...then they return and the Germans order them to wash his clothing and some problems happens there..... when they realize they are not Princess..others fall in love with Germans.... they love the white colour and blue eyes...we love strangers..we love the skin difference....
Picture was taken in Spain, last year...those girls walked 12 to 14 miles each day..during 30 days they were visiting Spain, France, Portugal,Holland, Germany and Italy...they have returned with beautifull legs because the strong exercise they made walking this way, and daily....maybe 350 miles during the month...the shoe used gone to the trash box... they both have double nationality, they are Spanish citizen too, they have all documents from Europe Union.
Well...too much of topic talk...i will reduce...or moderators will not be happy with uncle charlie.
regards,
Carlos
Those are my girls...left one is my daugther in my heart.... she is my wife's daugther... a nice mixing.... Afro-brazilian, Native Indian,Greek, Portuguese, Venezuelan and Spanish blood.
Rigth one is Larissa, my daugther...also another interesting mixing...Afro-brazilian blood,Native Indian,Greek, Portuguese, Dutch, Italian and Spanish.
Girls here result nice..not too much tall...average is 165 centimeters.... not normal to grow above 175 (rarity).... nice strong legs, ligth brown skin (coffee with a lot of milk), beautifull feet, curly hairs (rings with one inch diameter)... strong breasts (smaller than US girls) and many types of eyes...all colours, beeing the Indian Honey colour the most rare colour here..dominant is ligth brown and deep black.
They have some heart problems (usually blood pressure because African Heritage) and use to be alive till 75 years old.
The best they have...i think this is the most important for us...they think we, husbands, are alike king.... early morning they grow up and prepare coffee and clean all stuff for you...they go to work also... they take care from our childrens tenderly, are always worrying about you..ready to serve you in a wonderfull way...they are modern slaves...slaves in her hearts....ready to be good, to be kind, to be protective, to be your mother, your friend and your lover..also they do not use to betray their husbands...this is not acceptable and rarely happens...but men here is alike dog.... sadly men here is not fine.
Germans use to come here and often return with a Brazilian wife...some of them very nice..fall in love really... some others are professionals hunting strangers thinking they are rich (fause idea)...then they return and the Germans order them to wash his clothing and some problems happens there..... when they realize they are not Princess..others fall in love with Germans.... they love the white colour and blue eyes...we love strangers..we love the skin difference....
Picture was taken in Spain, last year...those girls walked 12 to 14 miles each day..during 30 days they were visiting Spain, France, Portugal,Holland, Germany and Italy...they have returned with beautifull legs because the strong exercise they made walking this way, and daily....maybe 350 miles during the month...the shoe used gone to the trash box... they both have double nationality, they are Spanish citizen too, they have all documents from Europe Union.
Well...too much of topic talk...i will reduce...or moderators will not be happy with uncle charlie.
regards,
Carlos
Attachments
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The LTP at the front end of the amplifier will work better when fed from a low source impedance.
Increasing the source impedance will make most LTP circuit create more distortion in their output signal.
A low source impedance is always beneficial.
Some designers may optimise the LTP to work better from a higher source impedance, but this is (I believe) relatively rare. The Crimson I built up came with a comment that it was optimised to operate witha 5k source impedance and since 1k0 was already fitted on the PCB, Crimson recommended that an extra 4k be inserted in the signal feed.
A Zin = 39k is inviting a pot <=10k. or better still, insert a buffer after the pot.
Increasing the source impedance will make most LTP circuit create more distortion in their output signal.
A low source impedance is always beneficial.
Some designers may optimise the LTP to work better from a higher source impedance, but this is (I believe) relatively rare. The Crimson I built up came with a comment that it was optimised to operate witha 5k source impedance and since 1k0 was already fitted on the PCB, Crimson recommended that an extra 4k be inserted in the signal feed.
A Zin = 39k is inviting a pot <=10k. or better still, insert a buffer after the pot.
Oh!..... thank you...i am perceiving something that makes sense
I will reduce the impedance Andrew.
thank you...i was thinking about that just now!
I am trying to match the input resistance to ground...but better is to reduce.
What about to include a resistance in parallel with the pot, connected to the pot extremes resistance...let's say 22K?
regards,
Carlos
I will reduce the impedance Andrew.
thank you...i was thinking about that just now!
I am trying to match the input resistance to ground...but better is to reduce.
What about to include a resistance in parallel with the pot, connected to the pot extremes resistance...let's say 22K?
regards,
Carlos
Attachments
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Hi Carlos,
Have you ever tried a unity gain buffer with your DX amplifier? From your pre-amplifier posts, I know you're not particularly attracted to this idea and I wasn't either until I started experimenting.
I recently built an op-amp buffer using the LM4562 with an input impedance of 100K and used this to feed a chip amplifier via a 20K volume pot. Compared to the original amplifier input impedance, this buffer significantly reduced the loading on the various sources and resulted in a much-improved (more detailed) sound stage.
Kind regards,
Steve
Have you ever tried a unity gain buffer with your DX amplifier? From your pre-amplifier posts, I know you're not particularly attracted to this idea and I wasn't either until I started experimenting.
I recently built an op-amp buffer using the LM4562 with an input impedance of 100K and used this to feed a chip amplifier via a 20K volume pot. Compared to the original amplifier input impedance, this buffer significantly reduced the loading on the various sources and resulted in a much-improved (more detailed) sound stage.
Kind regards,
Steve
Yes current flow...i do not like to introduce stages, in special many stages
as we have inside a chip.
Also, forgive me by my possible ignorance,but i do not see any mismatch....my source output impedance is 47K.... the power amplifier input impedance is around 39K...so, in my mind, it is fine!
thank you anyway... because the chip...take a look at the chip inside.... a lot of stages!
regards,
Carlos
as we have inside a chip.
Also, forgive me by my possible ignorance,but i do not see any mismatch....my source output impedance is 47K.... the power amplifier input impedance is around 39K...so, in my mind, it is fine!
thank you anyway... because the chip...take a look at the chip inside.... a lot of stages!
regards,
Carlos
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I agree there are many stages in these chips, but the sound changes speak for themselves (at least in my experience). I didn't suggest a mismatch exists in your case - sorry if you thought otherwise.
I would just be interested, if you had the inclination to try it, to see whether you found it sounded "better".
Regards,
Steve
I would just be interested, if you had the inclination to try it, to see whether you found it sounded "better".
Regards,
Steve
Chips already tested..i did with and without... and the second option is better
Also, each one of them (chip case ID number, factory and internal circuit) sounds different.... to me this is something not to test once again...i have already learned...not studying other things.
In my mind it is good not even to use those chips in audio..as to discover the one is the best one you gonna drive yourself crazy...and also, using them, you will have distortions resulted by the inclusion of stages inside the audio patch.
I suggest you, if you have not made the test, to do it by yourself.... with and without the chip.. and switching to both sittuations (A and B) very fast..because this is the only way we have to really fell things...and to change our speach and writing...in the place to write "I think so".... or "I imagine that"... you will be able to say to yourself and others a big and loud I KNOW!
thank you,
regards,
Carlos
Also, each one of them (chip case ID number, factory and internal circuit) sounds different.... to me this is something not to test once again...i have already learned...not studying other things.
In my mind it is good not even to use those chips in audio..as to discover the one is the best one you gonna drive yourself crazy...and also, using them, you will have distortions resulted by the inclusion of stages inside the audio patch.
I suggest you, if you have not made the test, to do it by yourself.... with and without the chip.. and switching to both sittuations (A and B) very fast..because this is the only way we have to really fell things...and to change our speach and writing...in the place to write "I think so".... or "I imagine that"... you will be able to say to yourself and others a big and loud I KNOW!
thank you,
regards,
Carlos
Attachments
I've tried three different op-amps in the buffer, the LM4562, OPA2134 and NE5532. The first two sounded similar, but the LM4562 had the distinct edge. The NE5532 sounded slightly less bright by comparison with a marginally inferior sound stage. They certainly sound "different" to each other as you describe. However, I won't be losing sleep in deciding which one of these I prefer, as it is fairly obvious from my tests which gives the most pleasant result.
Admittedly I haven't had the luxury of fast switching both with and without the chip, but even with slower switching tests my preference is currently with the buffer. Don't worry Carlos, I'm not attempting to convert you
Regards,
Steve
heheheheh...convertion not possible...i am a fanatic
this is above the reasons....it is passion..it is absolutelly non sense my dear.
We all think we are rigth and all others wrong...very crazy this stuff!.... the ones does not think into the conscience may be because they have those codes into the sub conscience..and this is something that barely comes to conscience.
It is self defense...the ego shield that makes us happy and self confident..different than that is depression... the other extreme..we must travel between those two extremes...maniac and depressive... me good today!
Do not worry and be happy!
regards,
Carlos
this is above the reasons....it is passion..it is absolutelly non sense my dear.
We all think we are rigth and all others wrong...very crazy this stuff!.... the ones does not think into the conscience may be because they have those codes into the sub conscience..and this is something that barely comes to conscience.
It is self defense...the ego shield that makes us happy and self confident..different than that is depression... the other extreme..we must travel between those two extremes...maniac and depressive... me good today!
Do not worry and be happy!
regards,
Carlos
Attachments
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I am adjusting my dual amplification system...amplifiers and speakers
one channel for bass and a second channel for treble and midrange.
I am adjusting the passive input filters and also the speaker.
Soon i will upload the speaker details in pictures...in one hour will be posted here.
Now one small test:
http://www.youtube.com/watch?v=cPqXEd1U6DM
Video not important..i have not even power on home ligth..audio is important.
Listen using good speakers and good amplification..you have some deep bass.
Here the slide movie showing the speaker inside:
http://www.youtube.com/watch?v=rljMY96z13M
one channel for bass and a second channel for treble and midrange.
I am adjusting the passive input filters and also the speaker.
Soon i will upload the speaker details in pictures...in one hour will be posted here.
Now one small test:
http://www.youtube.com/watch?v=cPqXEd1U6DM
Video not important..i have not even power on home ligth..audio is important.
Listen using good speakers and good amplification..you have some deep bass.
Here the slide movie showing the speaker inside:
http://www.youtube.com/watch?v=rljMY96z13M
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Thank you.... i use to spend some effort, in special to let young people understand
some simple things that were hard to me to discover.... no one teaches, they just show themselves that they know.... they use to criticise, to correct errors, but they do not use to teach you things.
This way, i had to learn by myself and reading forum, some goodwill guys have teached/explained me something.
Also, i have perceived that when they figth, to show themselves better than others, sometimes they inform some secrets they would never inform when not into an EGO competition... into those moments i could learn something too.
Enjoy our forum.... we have not more than 1 percent of very incredible nice folks... the same percentual we use to find into our society...but 1 percent of 100 thousand guys produces a very good number.
I think much more than half of my knowledge came from this forum... entire forum readings...other half came from long time building amplifiers.... when they exploded in my face i have learned not to use under rated voltage into condenser..also that transistor is a transistor and not more than a transistor...that there's no mistery..they have voltage, current, gain, polarity and maximum dissipation..and loves to work from one third to half the maximum allowable voltage with all leads connected into the circuit....say..both circuits operating, base to emitter and colector to emitter...also that you can put others.... to substitute 2SC5200 you have hundreds....some of them have thousands possible substitution... those things we learn burning parts.
Also transistor does not sound.... some of them can give you a sligtly less distorted high end because they can operate into very high frequencies (around 150 Megahertz or more)..but "there's not the good sound device"..also not the good sound capacitor or condenser... a lot of myths...and you realise they are not serious buiding, trying, testing, substituting and listening, and comparing A to B, a blind test... evaluated by non audiophile (prejudices), as childrens for instance.
You have just to ask children:
- "tell me the one sounds better and them explain why?"
Then you swith capacitor A to capacitor B and children will tell your the real thing without prejudice or mind polution caused by myths generated in our communitty.
Some defective capacitors, or some capacitor that have different capacitances (capacitive reactance different) compared to the value printed...those may sound different...but because deffective....normal ones sounds absolutelly the same.
regards,
Carlos
some simple things that were hard to me to discover.... no one teaches, they just show themselves that they know.... they use to criticise, to correct errors, but they do not use to teach you things.
This way, i had to learn by myself and reading forum, some goodwill guys have teached/explained me something.
Also, i have perceived that when they figth, to show themselves better than others, sometimes they inform some secrets they would never inform when not into an EGO competition... into those moments i could learn something too.
Enjoy our forum.... we have not more than 1 percent of very incredible nice folks... the same percentual we use to find into our society...but 1 percent of 100 thousand guys produces a very good number.
I think much more than half of my knowledge came from this forum... entire forum readings...other half came from long time building amplifiers.... when they exploded in my face i have learned not to use under rated voltage into condenser..also that transistor is a transistor and not more than a transistor...that there's no mistery..they have voltage, current, gain, polarity and maximum dissipation..and loves to work from one third to half the maximum allowable voltage with all leads connected into the circuit....say..both circuits operating, base to emitter and colector to emitter...also that you can put others.... to substitute 2SC5200 you have hundreds....some of them have thousands possible substitution... those things we learn burning parts.
Also transistor does not sound.... some of them can give you a sligtly less distorted high end because they can operate into very high frequencies (around 150 Megahertz or more)..but "there's not the good sound device"..also not the good sound capacitor or condenser... a lot of myths...and you realise they are not serious buiding, trying, testing, substituting and listening, and comparing A to B, a blind test... evaluated by non audiophile (prejudices), as childrens for instance.
You have just to ask children:
- "tell me the one sounds better and them explain why?"
Then you swith capacitor A to capacitor B and children will tell your the real thing without prejudice or mind polution caused by myths generated in our communitty.
Some defective capacitors, or some capacitor that have different capacitances (capacitive reactance different) compared to the value printed...those may sound different...but because deffective....normal ones sounds absolutelly the same.
regards,
Carlos
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