heatsink: it is about 15x15cm. I thought these chips can dissipate 40W each at full power (I think thats about the calculation in the data sheet) and compared sizes with my aleph-x (100W dissipation double size heatsink,65°C)
You think I can get away with much less? Probably I will put an XBOSOZ on that heatsink also to make an integrated amp. Then I think it could be justified? I like building cases around heatsinks...
Do they have to run hot to sound good?
power supply: yes I just have transformer, rectifier bridge and 2x10000µF, no regulation. No audible hum. Don't know what happens when very loud...
Would be probably a good idea to use an LM150 (3A) and its negative counterpart, which is that? Or do you just use 2 positive regulators?
The LM338 is very expensive... this my project is meant as the cheapest amp possible...
m.
You think I can get away with much less? Probably I will put an XBOSOZ on that heatsink also to make an integrated amp. Then I think it could be justified? I like building cases around heatsinks...
Do they have to run hot to sound good?
power supply: yes I just have transformer, rectifier bridge and 2x10000µF, no regulation. No audible hum. Don't know what happens when very loud...
Would be probably a good idea to use an LM150 (3A) and its negative counterpart, which is that? Or do you just use 2 positive regulators?
The LM338 is very expensive... this my project is meant as the cheapest amp possible...
m.
dieringe,
Interesting. I had some real trouble with my setup until I regulated the power supply. Now that I seem to have all the kinks worked out on my version, I'll have to remove the regulation and see how it works without it.
I don't know how much stock you can put into what the guys over in the chip amp forum claim, but the general consensus from them is that if you have a large amount of PS capacitance (in contrast to the Pass forum crowd, the GC guys call anything over a few thousand microfarads a lot) then you need to go with one of the following options:
1) add regulation after the capacitance, and then put 100uF decoupling caps on the chips PS pins, or
2) add a snubber network after the capacitance, and then put 100uF decoupling caps on the chips PS pins.
Right now, I have ~20 millifarad before the regulators, and then a 1500uF cap connecting each power supply on the chip to ground. I plan on trying a few of the variations the GC guys suggest, but not until after I get my BZLS up and running so I can drive my amp balanced.
As to the heatsink, it is definitely overcapacity. Unlike the class A stuff, these chips only draw power based on demand. I have both channels of my amp mounted on a flat piece of 1/4" aluminum plate about 20 x 20 cm, and even playing a a good volume, the plate never gets more than slightly warm to the touch.
Interesting. I had some real trouble with my setup until I regulated the power supply. Now that I seem to have all the kinks worked out on my version, I'll have to remove the regulation and see how it works without it.
I don't know how much stock you can put into what the guys over in the chip amp forum claim, but the general consensus from them is that if you have a large amount of PS capacitance (in contrast to the Pass forum crowd, the GC guys call anything over a few thousand microfarads a lot) then you need to go with one of the following options:
1) add regulation after the capacitance, and then put 100uF decoupling caps on the chips PS pins, or
2) add a snubber network after the capacitance, and then put 100uF decoupling caps on the chips PS pins.
Right now, I have ~20 millifarad before the regulators, and then a 1500uF cap connecting each power supply on the chip to ground. I plan on trying a few of the variations the GC guys suggest, but not until after I get my BZLS up and running so I can drive my amp balanced.
As to the heatsink, it is definitely overcapacity. Unlike the class A stuff, these chips only draw power based on demand. I have both channels of my amp mounted on a flat piece of 1/4" aluminum plate about 20 x 20 cm, and even playing a a good volume, the plate never gets more than slightly warm to the touch.
Re: too cool
I'm currently "burning in" (something like white noise) at 10ohms 5W resistors.
The resistors get warm only very very slightly but the heatsink is maybe
at 30-35°C. So if I add a BOSOZ and voltage regulators the heatsink maybe not so much too big...
As I switched back to my aleph-x after a few days I now notice how much better that is...
m.
I'm currently "burning in" (something like white noise) at 10ohms 5W resistors.
The resistors get warm only very very slightly but the heatsink is maybe
at 30-35°C. So if I add a BOSOZ and voltage regulators the heatsink maybe not so much too big...
As I switched back to my aleph-x after a few days I now notice how much better that is...
m.
SuperSymmetry?
After building, I now took a look at the schematic (as always 😀)---
Can somebody explain to me where the X-factor is? I just don't get it, I thought the feedback must somehow go from one half to the other but I just see two independent halves?
Feedback from the output goes to the input where the opamp is driven from, it is inverted but that doesn't make supersymmetry?
I compared with the aleph-x circuit. Shouldn't C1 and C2 (in Nelson's 1b schematic) go to the opposite sides? Then the opamps would have to run inverted?
thanks
m.
After building, I now took a look at the schematic (as always 😀)---
Can somebody explain to me where the X-factor is? I just don't get it, I thought the feedback must somehow go from one half to the other but I just see two independent halves?
Feedback from the output goes to the input where the opamp is driven from, it is inverted but that doesn't make supersymmetry?
I compared with the aleph-x circuit. Shouldn't C1 and C2 (in Nelson's 1b schematic) go to the opposite sides? Then the opamps would have to run inverted?
thanks
m.
Re: SuperSymmetry?
In fact it " travels" at the emitters of the BJT that are in communication
between the halves.
dieringe said:
In fact it " travels" at the emitters of the BJT that are in communication
between the halves.
Re: Re: SuperSymmetry?
really. So in the Aleph-x the "X-over" is just because the output stages are inverting?stefanobilliani said:
Re: Re: Re: SuperSymmetry?
Yes the output stages are inverting. The positive phase portion of the signal goes in the negative phase input of the diff pair , and vice versa .
That forms the negative feedback and X.
Of course the diff pair acts as phase inverter too.
In the GC Su-Sy both inputs of the GC (+ and -) itself ,and each halve, receive an inverted portion of the feedback signal, referenced to each input polarity.
dieringe said:
Yes the output stages are inverting. The positive phase portion of the signal goes in the negative phase input of the diff pair , and vice versa .
That forms the negative feedback and X.
Of course the diff pair acts as phase inverter too.
In the GC Su-Sy both inputs of the GC (+ and -) itself ,and each halve, receive an inverted portion of the feedback signal, referenced to each input polarity.
Re: Re: Re: Re: SuperSymmetry?
thanks. I think it is the diff pair that is not clear to me how it works...
Could there be an advantage (sonically) of flipping inputs of the opamps (make them inverting) and crossing the feedback? Only 2 instead of 3 transistors in the X-feedback?
It's a choice of which feedback has a longer way to go? Most probably it doesn't make a difference...
thanks. I think it is the diff pair that is not clear to me how it works...
Could there be an advantage (sonically) of flipping inputs of the opamps (make them inverting) and crossing the feedback? Only 2 instead of 3 transistors in the X-feedback?
It's a choice of which feedback has a longer way to go? Most probably it doesn't make a difference...
Re: Re: Re: Re: Re: SuperSymmetry?
Attacched is how the diff pair works in term of phase splitting .
Of course you can swap the outputs as you like taking the diff pair alone .
But the Su-Sy has some requirements for it function ...
From the diff pair point of view , the op amp acts as a non-inverting amp , the way we look at a Zen X . That's becouse the "feedback" around the diff are not crossed.
The OP amp itself , needs some negative Feedback just to work. I mean feedback from its output ,to its negative input .
So if you think of a Su- Sy without a point of communication from one halve to the other ,well it is not supersymmetry .
It is possible the use of a resistor instead of the CCS , with the consequence of having worse CMMR and PSRR.
OTOH , using the op amp inverting input for the X , and so on , crossing the diff outputs , will leave the OP amp + input at ground (assuming that it would work )
the GC-SS-3a.pdf shows an example where the positive op amp input is at ground , but doesn't use a diff pair .
dieringe said:
Attacched is how the diff pair works in term of phase splitting .
Of course you can swap the outputs as you like taking the diff pair alone .
But the Su-Sy has some requirements for it function ...
From the diff pair point of view , the op amp acts as a non-inverting amp , the way we look at a Zen X . That's becouse the "feedback" around the diff are not crossed.
The OP amp itself , needs some negative Feedback just to work. I mean feedback from its output ,to its negative input .
So if you think of a Su- Sy without a point of communication from one halve to the other ,well it is not supersymmetry .
It is possible the use of a resistor instead of the CCS , with the consequence of having worse CMMR and PSRR.
OTOH , using the op amp inverting input for the X , and so on , crossing the diff outputs , will leave the OP amp + input at ground (assuming that it would work )
the GC-SS-3a.pdf shows an example where the positive op amp input is at ground , but doesn't use a diff pair .
Attachments
Re^7: SuperSymmetry?
Yes I guess you couldn't just drive the negative input of the opamp and give it positive feedback instead of negative (just inverting everything)-
What a thought! I'm sorry
stefanobilliani said:
Yes I guess you couldn't just drive the negative input of the opamp and give it positive feedback instead of negative (just inverting everything)-
What a thought! I'm sorry
Re: Re: Re: SuperSymmetry?
This is not necessary. You can cross the outputs of the
differential inputs and use non-inverting stages and it works
just fine.
dieringe said:
This is not necessary. You can cross the outputs of the
differential inputs and use non-inverting stages and it works
just fine.
Hi,
At last, I have successfully completed my GC Supersymmetry. This time I use LM4766TF in place of TDA2030A and also increase the voltage rail to +/-30V.
Driving it directly from CD player(single ended), the sounds is quite blur compared to LM3875 GC. As I increase the volume, the sounds is breaking up the louder I go. At first I suspect that LM4766 and the transformer can't sustain high enough current in bridge mode, but after running for some time, heatsink and trafo(5A rating) are barely warm. Do you think that adding an input buffer to something like BUF634 will cure this?
I am going to implement DRV134 to drive it in balance mode. is it a worthwhile upgrade?
Pls advise.
Thanks.
At last, I have successfully completed my GC Supersymmetry. This time I use LM4766TF in place of TDA2030A and also increase the voltage rail to +/-30V.
Driving it directly from CD player(single ended), the sounds is quite blur compared to LM3875 GC. As I increase the volume, the sounds is breaking up the louder I go. At first I suspect that LM4766 and the transformer can't sustain high enough current in bridge mode, but after running for some time, heatsink and trafo(5A rating) are barely warm. Do you think that adding an input buffer to something like BUF634 will cure this?
I am going to implement DRV134 to drive it in balance mode. is it a worthwhile upgrade?
Pls advise.
Thanks.
Ipanema,
Sounds like you have run into the same problem I experienced earlier, and after some experimentation, I concluded that my CD player did not have enough current output capability to drive the amp without distorting. I solved the problem by using an active preamp to drive the amp, but the input buffer idea you are suggesting should also correct this.
As to driving it balanced, it is a timely question. I finally got my modified BZLS to a functional stage yesterday thus giving me a chance to run the Supersymmetric GC from a balanced source. The difference is not small, as evidenced by my wife immediately noticing the difference (her interest in my hobby is that it keeps me from bothering her, so I use her as my yardstick to ensure I am not hering "builders bias"). I highly recommend you upgrade to driving it biased.
Cheers, Terry
Sounds like you have run into the same problem I experienced earlier, and after some experimentation, I concluded that my CD player did not have enough current output capability to drive the amp without distorting. I solved the problem by using an active preamp to drive the amp, but the input buffer idea you are suggesting should also correct this.
As to driving it balanced, it is a timely question. I finally got my modified BZLS to a functional stage yesterday thus giving me a chance to run the Supersymmetric GC from a balanced source. The difference is not small, as evidenced by my wife immediately noticing the difference (her interest in my hobby is that it keeps me from bothering her, so I use her as my yardstick to ensure I am not hering "builders bias"). I highly recommend you upgrade to driving it biased.
Cheers, Terry
Completed some more experimenting and I am happy to report that my Susy GC can definitely play music deserving the moniker "high-end", but it requires two key elements:
1) Requires a balanced source signal.
2) Requires a source signal that has some current delivery capability.
Otherwise it reverts to sounding on the fuzzy side.
In comparison to the BrianGT Basic Kit GC, the Susy GC is clearly superior. The Susy GC also now clearly smokes my Rotel integrated. Faster, smoother, better soundstage, more detailed. Now I really wish I had an Aleph or X or Aleph-X to compare against, or for that matter to have heard one for memory comparisons.
So a question to Nelson:
Does the fuzziness that occurs when driven single-ended indcate that there is still a bit of instabilitiy happening, and thus a little more gain should thrown out?
Cheers, Terry
(Wishing he had an oscilloscope)
1) Requires a balanced source signal.
2) Requires a source signal that has some current delivery capability.
Otherwise it reverts to sounding on the fuzzy side.
In comparison to the BrianGT Basic Kit GC, the Susy GC is clearly superior. The Susy GC also now clearly smokes my Rotel integrated. Faster, smoother, better soundstage, more detailed. Now I really wish I had an Aleph or X or Aleph-X to compare against, or for that matter to have heard one for memory comparisons.
So a question to Nelson:
Does the fuzziness that occurs when driven single-ended indcate that there is still a bit of instabilitiy happening, and thus a little more gain should thrown out?
Cheers, Terry
(Wishing he had an oscilloscope)
A Mini-A is easy enough to make and ebay is full of o'scope's.
Great job Terry. One day I'll compare the GC with the AlephX.
/Hugo 🙂 -always likes to push people a little further-
Great job Terry. One day I'll compare the GC with the AlephX.
/Hugo 🙂 -always likes to push people a little further-
still sharp
I now made regulated power supply with higher voltage (2x26V).
It seems really to be better, especially the bass, but it is still sharp in the highs, compared to my aleph-x. Bass is better than aleph-x. Would be good for bi-amping...
My preamp is an XBOSOZ btw., but without CCS, just resistors.
metalman, what kind of zobel do you use? I have 220nF and 4.7 ohms. How would I detect instabilities with a scope?
m.
I now made regulated power supply with higher voltage (2x26V).
It seems really to be better, especially the bass, but it is still sharp in the highs, compared to my aleph-x. Bass is better than aleph-x. Would be good for bi-amping...
My preamp is an XBOSOZ btw., but without CCS, just resistors.
metalman, what kind of zobel do you use? I have 220nF and 4.7 ohms. How would I detect instabilities with a scope?
m.
dieringe,
I am using a 0.1uF film cap with a 5.1ohm 5W wirewound (neither are anything exotic. My zobel becomes active at about 300kHz, whereas yours starts at about 150kHz, so theoretically, yours should be more effective at reducing brightness. I agree that bass is a strong point for these amps. I have not heard my B&W's go that low before.
As to using a scope to look for instabilities, I've never had a chance to use one, so maybe someone alse here can comment. If I can get my hands on one I was simply going to look at distortion levels while trying different parts in the zobel and trying different gain-tossing levels.
Netlist,
I already have plans and some parts for building a pair of 25W Mini-A monoblocks (found some nice big heatsinks at a disposal company for real cheap that will handle 88W with a 30°C temp rise). Tell you what, I'll build the mini-A's, you build the Susy-GC, and then we can compare notes ...
Cheers, Terry
I am using a 0.1uF film cap with a 5.1ohm 5W wirewound (neither are anything exotic. My zobel becomes active at about 300kHz, whereas yours starts at about 150kHz, so theoretically, yours should be more effective at reducing brightness. I agree that bass is a strong point for these amps. I have not heard my B&W's go that low before.
As to using a scope to look for instabilities, I've never had a chance to use one, so maybe someone alse here can comment. If I can get my hands on one I was simply going to look at distortion levels while trying different parts in the zobel and trying different gain-tossing levels.
Netlist,
I already have plans and some parts for building a pair of 25W Mini-A monoblocks (found some nice big heatsinks at a disposal company for real cheap that will handle 88W with a 30°C temp rise). Tell you what, I'll build the mini-A's, you build the Susy-GC, and then we can compare notes ...
Cheers, Terry
