Re: Re: Square wave ringing?
I do not believe I have that value laying around. I will have to go to my local electronics store Monday when they are open and try that idea. To make sure I am looking at the right mpsa18 in my Aleph 3, is it the one bjt below the two 1.5K 1K5 UF ohm resisters off of the positive 25 volt rail? Not the current sense side? In your babelfish thread on page 1 your schematic referred to Q4 BC546?
http://www.diyaudio.com/forums/attachment.php?s=&postid=862357&stamp=1141601488
I hope to get this oscillations solved.
Both Mark and Lyndon were very enthusiastic about converting their Alephs after hearing mine. Mark thought maybe he could convert his Aleph 2's by changing some resisters to lower the voltage to the front end.
But for now, I still need to solve the oscillations yet alone the ringing.
choky said:
I do not believe I have that value laying around. I will have to go to my local electronics store Monday when they are open and try that idea. To make sure I am looking at the right mpsa18 in my Aleph 3, is it the one bjt below the two 1.5K 1K5 UF ohm resisters off of the positive 25 volt rail? Not the current sense side? In your babelfish thread on page 1 your schematic referred to Q4 BC546?
http://www.diyaudio.com/forums/attachment.php?s=&postid=862357&stamp=1141601488
I hope to get this oscillations solved.
Both Mark and Lyndon were very enthusiastic about converting their Alephs after hearing mine. Mark thought maybe he could convert his Aleph 2's by changing some resisters to lower the voltage to the front end.
But for now, I still need to solve the oscillations yet alone the ringing.
Re: 1nF
yup;
1 nanofarad from C to B of Q4 in Babelfish schm
NP sez that this cap is for preventing oscillations in CCS
ceramic is more than good for that,in fact-maybe best solution (think RF)
if that doesn't help,problem is somewhere in your physical layout of pcb and parts,not actual schmtc
btw-I have some thoughts about comparing KSA bass with J bass........not on Dynaudio
you can try the same on some 15" based lsp system,but not on Dynaudios
BillWW said:
yup;
1 nanofarad from C to B of Q4 in Babelfish schm
NP sez that this cap is for preventing oscillations in CCS
ceramic is more than good for that,in fact-maybe best solution (think RF)
if that doesn't help,problem is somewhere in your physical layout of pcb and parts,not actual schmtc
btw-I have some thoughts about comparing KSA bass with J bass........not on Dynaudio
you can try the same on some 15" based lsp system,but not on Dynaudios
Capacitors
Oh, and by the way,
Am I missing something. You all have such HUGE capacitors for your Alephs ... most people here on this board do.
My multi-purpose capacitors (i.e. must do for EVERYTHING) are 10 000uF 50V 85Celsius, and are only 30 * 40mm. A 120 000uF bundle sits nicely along my hand. Just looking back on the specification, the temperature rating looks like the most likely thing to be my undoing. It is these that I would be wanting to use on my currently non-existent Aleph 3/Babbelfish-Js.
Any thoughts please.
George.
Oh, and by the way,
Am I missing something. You all have such HUGE capacitors for your Alephs ... most people here on this board do.
My multi-purpose capacitors (i.e. must do for EVERYTHING) are 10 000uF 50V 85Celsius, and are only 30 * 40mm. A 120 000uF bundle sits nicely along my hand. Just looking back on the specification, the temperature rating looks like the most likely thing to be my undoing. It is these that I would be wanting to use on my currently non-existent Aleph 3/Babbelfish-Js.
Any thoughts please.
George.
They like a deeeeep reservoir for the power supplies on the Alephs. Pass approves, and the sound apparently can't be argued with...
There has been a lot of good discussion about large filter sections on this board, you can read for days about caps and chokes etc.
But it sure is hard to argue with so many satisfied "customers".
There has been a lot of good discussion about large filter sections on this board, you can read for days about caps and chokes etc.
But it sure is hard to argue with so many satisfied "customers".
Re: Choky
George,
I am using the MikeW boards that are single ended. I do not think it really matters on the boards, because I also have some Aleph BrianGT boards, and they sound similiar to me.
I do not know how to post photos on the forums yet. So, would not be able to do that currently.
It seems to me all of the Alephs that I have seen ring and that they all need compensations caps.
Even with mine slightly ringing, it sounded really nice. Some argue, if you dampen the ringing too much you lose musical definition or clarity. So, you only want to dampened as little as possible.
Regards, Bill
GeorgeBoles said:
George,
I am using the MikeW boards that are single ended. I do not think it really matters on the boards, because I also have some Aleph BrianGT boards, and they sound similiar to me.
I do not know how to post photos on the forums yet. So, would not be able to do that currently.
It seems to me all of the Alephs that I have seen ring and that they all need compensations caps.
Even with mine slightly ringing, it sounded really nice. Some argue, if you dampen the ringing too much you lose musical definition or clarity. So, you only want to dampened as little as possible.
Regards, Bill
Aleph boards?
George,
Here is the exact board and schematic I have been using for all of my year or so long tweaking.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=37446&highlight=
The MikeW revision 2 board pdf file is my setup.
Bill
George,
Here is the exact board and schematic I have been using for all of my year or so long tweaking.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=37446&highlight=
The MikeW revision 2 board pdf file is my setup.
Bill
Hello, Stocker.
Yes, I can understand the need for a large capacitance. As I wrote, 120000uF is what I am familiar with, and I am going to use that at least for any of the Alephs from 30W and up. It is just the general "bigness" of the blue capacitors which everyone seems to be using. Maybe it is a voltage or temperature thing, but I would have thought that the ones I describe should fill the bill. I guess I could add a fan if temperatures in the case get too high.
Regards,
George
Yes, I can understand the need for a large capacitance. As I wrote, 120000uF is what I am familiar with, and I am going to use that at least for any of the Alephs from 30W and up. It is just the general "bigness" of the blue capacitors which everyone seems to be using. Maybe it is a voltage or temperature thing, but I would have thought that the ones I describe should fill the bill. I guess I could add a fan if temperatures in the case get too high.
Regards,
George
Nelson Pass said:
they think on cap across 220K feedback resistor
I think that Bill's "abused"
amp needs compensation in output CCS or even ~1n from gate stopper of lower output mosfet to output rail,known from some iterations of Alephsbut-first,I'm sure that his amp need pair of new pcbs.......or ptp from start...
Attachments
I'm just curious :
whatza initial DC offset for Aleph amp (from cold) ?
I didn't make any Aleph before,so my xperience is limited to Babelfish only;
to NP,if he's willing to respond:
do we and when we will have chance to see J service manual ?
I'm not dying from desire to make exact J,same as I will not make Z8 (even if I have several LU thingies).....I'm just curious and willing to learn something
whatza initial DC offset for Aleph amp (from cold) ?
I didn't make any Aleph before,so my xperience is limited to Babelfish only;
to NP,if he's willing to respond:
do we and when we will have chance to see J service manual
?I'm not dying from desire to make exact J,same as I will not make Z8 (even if I have several LU thingies).....I'm just curious and willing to learn something
Test tone generator
Here is an update,
I have not done much with the amp, since Mark has my test tone generator. I do have my computer, which I could use my Tri Vista DAC to output a square wave to the Aleph from my computer software generator. But after checking the square wave of the DAC, it was no where near as nice as my Test tone tube generator that Mark has. So, I became discouraged in trying to even look at my aleph with the poor output from the DAC.
I guess I will have to see Saturday how Mark is doing with it. He was going to check some of the tubes in my tone generator.
I did try 10 pF on the 220K feedback resister. On the MikeW boards, the .001 uF on the mpsa18, it only had provisions other than the base and collector, so I have not tried that exact combination yet.
I will start with the 5 pF on the feedback, but will have to most likely play around with it Saturday. Maybe I will be able to get my tube test tone generator back to try various compensations.
To me the ringing did not look that bad on the first photo in the square wave photos in this thread on page 7 I believe.
Regards, All
Thank you for all those who have helped me on this jfet project. This has been a very wonderful project and I have learned a lot for my first amp that I have continually modified over the year and a half owning it.
PS Choky,
I have more boards than just this prototype. Once I find what I like, I will tri amp my system, but first I have to find what I like first before using my fresh mint boards.
Here is an update,
I have not done much with the amp, since Mark has my test tone generator. I do have my computer, which I could use my Tri Vista DAC to output a square wave to the Aleph from my computer software generator. But after checking the square wave of the DAC, it was no where near as nice as my Test tone tube generator that Mark has. So, I became discouraged in trying to even look at my aleph with the poor output from the DAC.
I guess I will have to see Saturday how Mark is doing with it. He was going to check some of the tubes in my tone generator.
I did try 10 pF on the 220K feedback resister. On the MikeW boards, the .001 uF on the mpsa18, it only had provisions other than the base and collector, so I have not tried that exact combination yet.
I will start with the 5 pF on the feedback, but will have to most likely play around with it Saturday. Maybe I will be able to get my tube test tone generator back to try various compensations.
To me the ringing did not look that bad on the first photo in the square wave photos in this thread on page 7 I believe.
Regards, All
Thank you for all those who have helped me on this jfet project. This has been a very wonderful project and I have learned a lot for my first amp that I have continually modified over the year and a half owning it.
PS Choky,
I have more boards than just this prototype. Once I find what I like, I will tri amp my system, but first I have to find what I like first before using my fresh mint boards.
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