Nuuk said:
Me againCarlos, I have had my GC monoblocks running continuously for four hours as I am trying to break in my rebuilt Goodmans 201s. When I read your post I went straight over to see if they are hot but they are only very slightly warm and it is very hot here today.
My MUR860's are just glued to a piece of fibreglass.
Ahha, a hot day in Somerset, have a nice cool cider.
Re: Re: Re: If it has a hole, it's for a heatsink
I was actually speaking from experience. I use my Proac Clones and have had them playing loud for at least 4 hours in a room 32+ degrees centigrade and the 3875's, attached to the bottom of my not too thick case, get slightly warm to the touch but nowhere near anything called hot. The diodes are close to room temperature. And that even in a place where the air is restricted. And I'm running 25 VAC transformers. And I am playing Fourplay, Lisa Nilsson and others with a fair amount of long bass notes.
However, if we are talking a bridge GC used with powers in the order of 200 W for extended low frequency content, like a sub, and a 4 Ohm load then obviosuly I would think about at least mounting them to something heat dissipating. And checking the BPA-200 and the heatsink used it should be pretty obvious that the heatsink needed is very modest.
carlosfm said:
I was actually speaking from experience. I use my Proac Clones and have had them playing loud for at least 4 hours in a room 32+ degrees centigrade and the 3875's, attached to the bottom of my not too thick case, get slightly warm to the touch but nowhere near anything called hot. The diodes are close to room temperature. And that even in a place where the air is restricted. And I'm running 25 VAC transformers. And I am playing Fourplay, Lisa Nilsson and others with a fair amount of long bass notes.
However, if we are talking a bridge GC used with powers in the order of 200 W for extended low frequency content, like a sub, and a 4 Ohm load then obviosuly I would think about at least mounting them to something heat dissipating. And checking the BPA-200 and the heatsink used it should be pretty obvious that the heatsink needed is very modest.
Re: Re: Re: Re: If it has a hole, it's for a heatsink
Ok, but don't judge it that way.
If you only tested with one pair of speakers...
Maby your speakers are an easy load.
My Epos speakers, although 8 ohms, are a tough load, very hard to drive.
And I tested my GC with several speakers.
With some of them it's a piece of cake and it only gets warm.
But with a pair of Allison 4 ohm speakers, for testing purposes listening very loud, I managed to "see" the thermal protection in action.
On the datasheet it says it kicks in at 150ºC!
What it does is to reduce the volume, then it cool a little and then up again.
The result is the volume up-down-up-down.
I don't need to tell you that when I put my hand on the bottom of the case I almost got without skin.
This was listening very loud, for testing only, as I don't listen to music that way.
But this serves to see that each case is a case and some people have some speakers, other people have other speakers and the results may vary.
With some speakers it will get hot even at "normal" volumes.
What I can tell you is that you can make it go very hot, in a question of a few minutes if you don't have a decent heatsink.
These days more and more speakers are 4 ohms, or have 4 ohm woofers.
The majority of american speakers nowadays are 4 ohms.
Nevermind, I usually prefer the british speakers.
Or the ones I made with Seas units.
UrSv said:
Ok, but don't judge it that way.
If you only tested with one pair of speakers...
Maby your speakers are an easy load.
My Epos speakers, although 8 ohms, are a tough load, very hard to drive.
And I tested my GC with several speakers.
With some of them it's a piece of cake and it only gets warm.
But with a pair of Allison 4 ohm speakers, for testing purposes listening very loud, I managed to "see" the thermal protection in action.
On the datasheet it says it kicks in at 150ºC!
What it does is to reduce the volume, then it cool a little and then up again.
The result is the volume up-down-up-down.
I don't need to tell you that when I put my hand on the bottom of the case I almost got without skin.
This was listening very loud, for testing only, as I don't listen to music that way.
But this serves to see that each case is a case and some people have some speakers, other people have other speakers and the results may vary.
With some speakers it will get hot even at "normal" volumes.
What I can tell you is that you can make it go very hot, in a question of a few minutes if you don't have a decent heatsink.
These days more and more speakers are 4 ohms, or have 4 ohm woofers.
The majority of american speakers nowadays are 4 ohms.
Nevermind, I usually prefer the british speakers.
Or the ones I made with Seas units.
Neat Bridge from Avondale
I like the look of this bridge from Avondale Audio in the UK.
http://www.users.zetnet.co.uk/avondale
http://www.users.zetnet.co.uk/avondale/Bridge.jpg
The bare pcb is 4.50 GBP.
Anyone used one of these?
I think it could do nicely - especially with some small anodised heatsinks on the board!
Cheers
Jon
I like the look of this bridge from Avondale Audio in the UK.
http://www.users.zetnet.co.uk/avondale
http://www.users.zetnet.co.uk/avondale/Bridge.jpg
The bare pcb is 4.50 GBP.
Anyone used one of these?
I think it could do nicely - especially with some small anodised heatsinks on the board!
Cheers
Jon
ALW said:
Actually I didn't misunderstood anything. I just chose to do it that way because of space limitation and my thinking that even without resistor it is still better. Also, in one of the threads dealing with snubbers, the was opinion, that in certain setups, capacitor alone is enough. These days I'm not using the caps across diodes at all, as I think it sounds worse (I'm actually listen to parts and circuits now). The picture of the bridge is from the Aleph X (this may be also a reason why GC sounds better
).So, in GC there's no snubbers, just diodes. And on certain material and speakers the diodes get pretty hot, but still you'll be able to touch them. Same goes for the chip. Once I got my amp hot at at least 50 deg. C, where normally it's barely warm. Thge only extra caps I'm using now is a pair of 4.7 BG N right after bridges, on ea. rail to ground.
ALW said:
That's the link from the snubbers thread. On page 10 of the article we can read:
It is interesting to see what happens when only a capacitor is used as a snubber, as is
commonly recommended. A value of 0.01uF was added for C x and then simulated.
Figure 11 shows the results.
Figure 11. 0.01uF capacitor only snubber.
Ringing is still evident, no damping or snubbing has occurred, however the frequency is
much lower.
Obviously the improvement in sonic quality or reduction of noise occurs because the
ringing frequency is so much lower that the ability to couple to other circuits is reduced.
In fact, the larger the capacitor, the lower the frequency. All of this very much depends
on the quality of the components and the transformer involved. It should come as no
surprise that each power supply must be individually tuned for optimum performance.
So my understanding is that if someone doesn't want to go through all those snubber calculations, using a single high value cap across diodes, should still bring improvement (at least that's what' suggested in the article) and many manufacturers are practising that. But as I said before, I prefer to choose better sounding diodes and forget about all those snubber issues. I also suspect, that although snubbers may improve certain aspects of performance, they screw up sonics in some other way.
what ?
I have repeatedly noticed a huge improvement in quality with just caps but that is with the caps directly across the secondarys. otherwise as andy says the caps are just providing a HF s/s path across the diodes
have you tried caps across the secondarys ?
I would be really suprised if you did not notice a big impovement.
I use 4.7uF on all my power amps - sounds outrageous in theory, but in practice, for me, it sounds amazing, much more refined and no trade offs that I have noticed
If you do not notice the difference I will have to conclude that we are living in different universe's with different laws of nature operating
chou
mike
Peter Daniel said:
I have repeatedly noticed a huge improvement in quality with just caps but that is with the caps directly across the secondarys. otherwise as andy says the caps are just providing a HF s/s path across the diodes
have you tried caps across the secondarys ?
I would be really suprised if you did not notice a big impovement.
I use 4.7uF on all my power amps - sounds outrageous in theory, but in practice, for me, it sounds amazing, much more refined and no trade offs that I have noticed
If you do not notice the difference I will have to conclude that we are living in different universe's with different laws of nature operating
chou
mike
Jonclancy-
Thanks for the link. I like that layout. I think I will turn it inside out, tho, without the pcb. Lay them on their sides with pins in on the perfboard. Bend the pins down into the holes and solder the bridge.
Then I will heatsink each diode with something small, and since the tabs are all pointing out, I will have plenty of room.
As long as I have a little air circulation gap between the diodes and the perfboard, I should do fine.
Thanks for the link. I like that layout. I think I will turn it inside out, tho, without the pcb. Lay them on their sides with pins in on the perfboard. Bend the pins down into the holes and solder the bridge.
Then I will heatsink each diode with something small, and since the tabs are all pointing out, I will have plenty of room.
As long as I have a little air circulation gap between the diodes and the perfboard, I should do fine.
Here's one of my more recent bridges in GC monoblock. One per rail http://www.diyaudio.com/forums/showthread.php?s=&threadid=13687&highlight=gainclone+monoblocks
Attachments
they are heatsinked, but because the heat issue isn't that big here I used a piece of thin fiberglass strip for that purpose. If you have enough space this is probably the best way to wire a bridge: outside pins connected together for AC supply, the inside pins crossed connected for ground and DC supply. As you see, no snubbers this time
Have you guys tried the RC filter described as ideal in the article you quoted? The graphic with just the cap showed a pronounced lower-freq sine, for a long while after the no-snubber ringing would have ended. It is lower energy so it doesn't couple with other elements of your circuit, but if you make the cap a lot bigger than what was quoted you end up impinging on audio frequencies.
Squalish said:
I the real world I find it hard to see any ringing wether the cap is there or not. for me, the lower the frequency the better, the filter caps and chips supply rejection are far far more effective at low frequencies. subjectively the big cap sounds great.
it's worth trying...
mike
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