OK, i lied, I don't have the pi filter inductors. But you have now reminded me that we can use resistors. They appear to be 0.22ohm, 10 watt, right?
How hot do they get? !
! !
I guess in this case inductive resistors are actually an advantage, right?
In the lower right corner of the schematic for the power supply filter, you have an output labeled V+20 L .
I think you meant V-20R ? Tiny point but don't want to confuse anyone.
Man, I want to get this up and running! gotta veneer my speakers first....
How hot do they get? !
! ! I guess in this case inductive resistors are actually an advantage, right?
In the lower right corner of the schematic for the power supply filter, you have an output labeled V+20 L .
I think you meant V-20R ? Tiny point but don't want to confuse anyone.
Man, I want to get this up and running! gotta veneer my speakers first....
Fuling said:
Yep, 120 ohms per phase for a 240 ohm balanced load...
Henrik:
As I have lovered the 7,5 ohm resistors from your schematic to 6,8 ohm, I figure I have about 3dB less gain in my XSOZ. I would like to compensate for this by adding 3dB extra gain in the XBZLS; could you please recommend me a new set of feedback-resistor values? 60K?
Variac said:OK, i lied, I don't have the pi filter inductors. But you have now reminded me that we can use resistors. They appear to be 0.22ohm, 10 watt, right?
How hot do they get? !
I guess in this case inductive resistors are actually an advantage, right?
In the lower right corner of the schematic for the power supply filter, you have an output labeled V+20 L .
I think you meant V-20R ? Tiny point but don't want to confuse anyone.
Man, I want to get this up and running! gotta veneer my speakers first....
Yep, 0,22 ohm/10W. They have about 0,9V across them. They get really hot, but I haven't measured the temp.
Inductive resistors can be seen as an advantage, as they take out some high frequency noise.
You are right AND wrong: it is supposed to say "V+20R" 😉
Hehe, that's the danger of hooking things up before they're completely finished....
While we are on the subject (inductive resistors):
The power resistors I use in this SOZ are inductive. I have buildt several 8W SOZ versions in the past, all with different parts selctions etc. What I learned is that every little thing you put into this amp makes a audible difference in the final sound of the amp.
For instance, if you use non-inductive power resistors (in my amp: Caddock MP930 4+4 ohm) the amp is more analytical, while if you use inductive resistors (like this one Arcol HS50) it becomes more romantic. This is all a matter of taste. The only problem is that it can be quite difficult/expensive to to these kinds of experiments.
In this XSOZ version I have made my choice of components based on earlier experiences, except for the MOSFETs (I can also imagine some cap changes) which I will be trying different ones for obvious reasons.
The power resistors I use in this SOZ are inductive. I have buildt several 8W SOZ versions in the past, all with different parts selctions etc. What I learned is that every little thing you put into this amp makes a audible difference in the final sound of the amp.
For instance, if you use non-inductive power resistors (in my amp: Caddock MP930 4+4 ohm) the amp is more analytical, while if you use inductive resistors (like this one Arcol HS50) it becomes more romantic. This is all a matter of taste. The only problem is that it can be quite difficult/expensive to to these kinds of experiments.
In this XSOZ version I have made my choice of components based on earlier experiences, except for the MOSFETs (I can also imagine some cap changes) which I will be trying different ones for obvious reasons.
Very cute amp. Nice layout. Yup, this is a great sounding amp. You hear everything. It's only as good as your source. Quality LP's sound awesome. I have a little over ten watt mono blocks. It runs hot and I have at least twice the heat sinking. I do not know how your cute amp simply does not melt down into a pool of molten metal.
Also if one of those resistors goes it makes a huge mess. You hear a large pop. The ends fly off. A coil of charred wire pops out. And black soot floats about the room landing like black snow everywhere( if the top cover is off).
Also if one of those resistors goes it makes a huge mess. You hear a large pop. The ends fly off. A coil of charred wire pops out. And black soot floats about the room landing like black snow everywhere( if the top cover is off).
Thanks gnoumus..
Aluminium can take about 1000'C before meltdown 😀
I don't think 60-70'C chassis temp is something to get overly excited about, it just isn't pleasant to touch it. The resistors blowing is among the least of my worries, in fact I'm not worried at all 😉
-Sounds like you have experienced som resitor blowing? -Care to tell the whole story?
Aluminium can take about 1000'C before meltdown 😀
I don't think 60-70'C chassis temp is something to get overly excited about, it just isn't pleasant to touch it. The resistors blowing is among the least of my worries, in fact I'm not worried at all 😉
-Sounds like you have experienced som resitor blowing? -Care to tell the whole story?
I was testing mosfets for SOZ in a real amp like test rig. Used too small a wire wound resistor without heat sink. Ignored the little bit of smoke from the resistor. Soon after boom. Big mess. Now if I smell or see the slightest amount of smoke in a project I am building I dive for the off switch.
Hi Mad_K
I can't see how you should miss 3db of gain because of the 6.8 Ohm resistors.
You are running your amp at a bit higer current, you have something like 1.95 A through each fet, mine are running at 1.8A.
Your smaller loadresistors should work just fine because of the higer current. Even the drain bias is ok.
May bee I have missed something.
Raising the gain is a bit difficult, but could be done.
If you raise the gain by altering the feedbackresistor in the X-BOSOZ, watch out for the high end roll off. With IRFP140 and IRF610 from IRF, your system is about 3db down at 100kHz, if you change the R122 R123 to 62K then you are down around 3db at 80kHz, and that is audible, I have been there.
A better solution would be to lower the inpurresistor to 6.8K that shoud give you +3db, but the cost is lower inputimpedance.
These mesurements is done in Simetrix' simulator, and I have navigated through realworld experiments and listeningtests to reach the boundaries of this setup between the X-BOSOZ and the SOZ.
A lot of people has ben concerned about the heat when scaling XSOZ up to more than 10W, I say heat can be removed but keeping the freguency response at a higer gainlevel is a bigger challenge.
Buffers makes a good job when it comes to impedance matching, but here they tends to degrade the sound significantly. May be the buffers I tried out wasn´t good enough, i tried the buffer from the ZV4.
These problems is caused by the input capacitanse of the fets, so try to find some fets with significantly lesser capacitanse.
Improovements in impedance/sound is still to be done.
Regards Henrik
Mad_K said:
I can't see how you should miss 3db of gain because of the 6.8 Ohm resistors.
You are running your amp at a bit higer current, you have something like 1.95 A through each fet, mine are running at 1.8A.
Your smaller loadresistors should work just fine because of the higer current. Even the drain bias is ok.
May bee I have missed something.
Raising the gain is a bit difficult, but could be done.
If you raise the gain by altering the feedbackresistor in the X-BOSOZ, watch out for the high end roll off. With IRFP140 and IRF610 from IRF, your system is about 3db down at 100kHz, if you change the R122 R123 to 62K then you are down around 3db at 80kHz, and that is audible, I have been there.
A better solution would be to lower the inpurresistor to 6.8K that shoud give you +3db, but the cost is lower inputimpedance.
These mesurements is done in Simetrix' simulator, and I have navigated through realworld experiments and listeningtests to reach the boundaries of this setup between the X-BOSOZ and the SOZ.
A lot of people has ben concerned about the heat when scaling XSOZ up to more than 10W, I say heat can be removed but keeping the freguency response at a higer gainlevel is a bigger challenge.
Buffers makes a good job when it comes to impedance matching, but here they tends to degrade the sound significantly. May be the buffers I tried out wasn´t good enough, i tried the buffer from the ZV4.
These problems is caused by the input capacitanse of the fets, so try to find some fets with significantly lesser capacitanse.
Improovements in impedance/sound is still to be done.
Regards Henrik
I have just finished my new 10W XSOZ, so it shoud fit in here.
Unfortunately I can't hear it, my midrange drivers is beeing reconed, I will get them sometimes next week
May be I will go without fans at side of the amp, those heatsinks is just 32'C above room temp. When I think of Mad_K's I feel safe.
It also makes it easier to get the amp in and out the rack without a screwdriver.
Unfortunately I can't hear it, my midrange drivers is beeing reconed, I will get them sometimes next week
May be I will go without fans at side of the amp, those heatsinks is just 32'C above room temp. When I think of Mad_K's I feel safe.
It also makes it easier to get the amp in and out the rack without a screwdriver.
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Awesome work. Your Mosfets have more than enough heat sinking. They should last long. Wait till you see how those resistors cook. A lot of heat. Good thing you have the fans.
Wow, nice work.
Cabling and soldering looks quite artistic.
As far as I can see you don´t like metal work too.😉
Where did you get your cases?
Cheers
Jens
Cabling and soldering looks quite artistic.
As far as I can see you don´t like metal work too.😉
Where did you get your cases?
Cheers
Jens
Gnomus
Thanks for the kind words.
Yes, I am verry happy for those fans for the resistors, and I hope you are right abut the heatsinks for my fets.
Actually I have seen the resistors cooking, and the box, the heatsinks and the powerresistors are there from my earlier testversion of this X-SOZ.
Regards
Thanks for the kind words.
Yes, I am verry happy for those fans for the resistors, and I hope you are right abut the heatsinks for my fets.
Actually I have seen the resistors cooking, and the box, the heatsinks and the powerresistors are there from my earlier testversion of this X-SOZ.
Regards
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