hello I am in the process of building the 4780 kit (parallel) using a single 300va 22v transformer and have a few questions ??
1. can I use one rectifier board to run both lm4780's??
2. if rectifier 2 boards are needed do I just parallel the 22vac side ??
3. is the "chg" terminal on the amp board the chassis ground ??
4. can I mount the chip a heat sink using steal screws if the heat sink is tied to the chassis ground (the chip will have mica between the chip and the sink)
5. should i use thermal compound and if so where i.e between the chip and the mica or between the mica and the heat sink ??
thanks
1. can I use one rectifier board to run both lm4780's??
2. if rectifier 2 boards are needed do I just parallel the 22vac side ??
3. is the "chg" terminal on the amp board the chassis ground ??
4. can I mount the chip a heat sink using steal screws if the heat sink is tied to the chassis ground (the chip will have mica between the chip and the sink)
5. should i use thermal compound and if so where i.e between the chip and the mica or between the mica and the heat sink ??
thanks
1. yes
2. it's not recommended to use two rectifier boards with one transformer
3. yes
4. the metal screws are fine, but double check that they do not touch metal tab on the chip which is normally connected to V-
5. thermal compound should be applied to both sides of mica washer
http://home.pacific.net.au/~gnb/audio/images/4780PkgPins9a-10.jpg
2. it's not recommended to use two rectifier boards with one transformer
3. yes
4. the metal screws are fine, but double check that they do not touch metal tab on the chip which is normally connected to V-
5. thermal compound should be applied to both sides of mica washer
http://home.pacific.net.au/~gnb/audio/images/4780PkgPins9a-10.jpg
I guess you could do that, but it's better to do it the way described here: http://www.diyaudio.com/forums/showthread.php?postid=1518369#post1518369
Heatsink?
Peter
I've recently ordered one of your kits and while I wait for it to be delivered I've been looking into cooling requirements. I started another thread about heatsinking in general and how to calculate it, but it's got to the stage where heatspreaders have been discussed, in particular referencing your amplifier design.
I've been looking at you use of copper block for some time, and to me it's far more elegant than two big heat sinks as it allows for a more compact case unit.
How does the copper blocks compare to using heat sinks - are there any limitations of them that should be taken into consideration?
I also assume that you're connecting the copper block directly to the case and using the rest of the casing to dissipate heat? If so, how warm does the casing get?
My design ideas for the case will be based on your own (copying being the best form of flattery
), but I intend to make the case about 6" * 9.5" and 4" high. Do you reckon that would give enough surface area for adequate heat dissipation from the copper blocks?
Thanks
Ian
Peter
I've recently ordered one of your kits and while I wait for it to be delivered I've been looking into cooling requirements. I started another thread about heatsinking in general and how to calculate it, but it's got to the stage where heatspreaders have been discussed, in particular referencing your amplifier design.
I've been looking at you use of copper block for some time, and to me it's far more elegant than two big heat sinks as it allows for a more compact case unit.
How does the copper blocks compare to using heat sinks - are there any limitations of them that should be taken into consideration?
I also assume that you're connecting the copper block directly to the case and using the rest of the casing to dissipate heat? If so, how warm does the casing get?
My design ideas for the case will be based on your own (copying being the best form of flattery
), but I intend to make the case about 6" * 9.5" and 4" high. Do you reckon that would give enough surface area for adequate heat dissipation from the copper blocks?Thanks
Ian
I briefly checked the other thread and while the advice posted there is sound, I wouldn't complicate things that much, it's only a Gainclone amp and heat dissipation usually is not a problem at all.
All my chassis, except for Integrated amp, have underated heatink capabilities, and when pushing the amp to deliver full power constantly, the chassis temperature will exceed 50*C or so. In real life it was never a problem and I had people running Patek amp into 2 ohms loads with success.
The temperature will depend on your listening habits and type of music. Pushing heavy bass content material (techno, house music) will make things hot. Playing Jacinta or Patricia Barber at moderate volumes will cause no sweat
I use copper in a Patek amp mostly to increase the amp weight, influence sonic signature a bit by controlling resonances, as well provide means of efficient heat transfer to all 4 chassis panels. Too much copper is no good either, as it collects heat and releases slowly.
I used bigger solid brass block in my other amp, but it was getting too hot an I had to drill holes to increase dissipation area: http://www.diyaudio.com/forums/showthread.php?s=&threadid=76609&highlight=
Using external chassis panels is a good idea and actual heatsinks are rarely needed.
All my chassis, except for Integrated amp, have underated heatink capabilities, and when pushing the amp to deliver full power constantly, the chassis temperature will exceed 50*C or so. In real life it was never a problem and I had people running Patek amp into 2 ohms loads with success.
The temperature will depend on your listening habits and type of music. Pushing heavy bass content material (techno, house music) will make things hot. Playing Jacinta or Patricia Barber at moderate volumes will cause no sweat
I use copper in a Patek amp mostly to increase the amp weight, influence sonic signature a bit by controlling resonances, as well provide means of efficient heat transfer to all 4 chassis panels. Too much copper is no good either, as it collects heat and releases slowly.
I used bigger solid brass block in my other amp, but it was getting too hot an I had to drill holes to increase dissipation area: http://www.diyaudio.com/forums/showthread.php?s=&threadid=76609&highlight=
Using external chassis panels is a good idea and actual heatsinks are rarely needed.
Hi Peter
Few posts back you included a picture of your 4 channel amp with a single transformer. Is it possible to build a 10-12 channels with a single transformer or 4 is the max? I wanted to use F5 amp boards but i was told that such amp would make to much heat. Is your LM4780 amp more suitable for such build? I bought a pair of LM4780 boards from your website to check it out and I'm encouraged by its size. I'd like to keep them in a single chassis but if i can't 3 is better than 5 or 6 (if i had to go for 2 channels per chassis) I need around 60 watts per channel, the load would be 6 and 8 ohm.
Any advise would be greatly appreciated.
Few posts back you included a picture of your 4 channel amp with a single transformer. Is it possible to build a 10-12 channels with a single transformer or 4 is the max? I wanted to use F5 amp boards but i was told that such amp would make to much heat. Is your LM4780 amp more suitable for such build? I bought a pair of LM4780 boards from your website to check it out and I'm encouraged by its size. I'd like to keep them in a single chassis but if i can't 3 is better than 5 or 6 (if i had to go for 2 channels per chassis) I need around 60 watts per channel, the load would be 6 and 8 ohm.
Any advise would be greatly appreciated.
4-way amplifiers
I built 2 sets of 4-way amplifiers (LM3875s) to run my Linkwitz Orion speakers using solid copper bars and aluminium strips to house connectors and to keep the whole thing together. I did not fully enclose the chassis allowing air to move over the boards.
Rather than using one psu per channel I opted for two with the boards being run in pairs. Power was fine - but I do not know what would have happened if I had used one psu per side.
There were no heat problems at any time - the copper bar (1 inch square) never got warm.
For a larger number of channels I might be tempted to buy a large flat heatsink and attach all the chip amps to it (300x200 mm might be adequate).
Alan
I built 2 sets of 4-way amplifiers (LM3875s) to run my Linkwitz Orion speakers using solid copper bars and aluminium strips to house connectors and to keep the whole thing together. I did not fully enclose the chassis allowing air to move over the boards.
Rather than using one psu per channel I opted for two with the boards being run in pairs. Power was fine - but I do not know what would have happened if I had used one psu per side.
There were no heat problems at any time - the copper bar (1 inch square) never got warm.
For a larger number of channels I might be tempted to buy a large flat heatsink and attach all the chip amps to it (300x200 mm might be adequate).
Alan
transformer rating
Peter,
It’s been almost a year I listen to GC I built as per your design with NOS DAC. It is simply a great combination..…
Lately I’ve been thinking of upgrading the power supply by using higher transformer rating with the rest of the component and setup still the same. The reason for upgrading is to achieve better bass power, instead of placing a bigger main caps...
At the moment I’m using mono configuration with 225VA 2x22V per channel (dual bridge) driving 8 ohm speaker.
Do you think going to 500VA 2x25V (Avel) is excessive for this LM3875 GC…? Could make a comment on what would be the optimum transformer rating for this?
Thanks in advance.
Joshua
Peter,
It’s been almost a year I listen to GC I built as per your design with NOS DAC. It is simply a great combination..…
Lately I’ve been thinking of upgrading the power supply by using higher transformer rating with the rest of the component and setup still the same. The reason for upgrading is to achieve better bass power, instead of placing a bigger main caps...
At the moment I’m using mono configuration with 225VA 2x22V per channel (dual bridge) driving 8 ohm speaker.
Do you think going to 500VA 2x25V (Avel) is excessive for this LM3875 GC…? Could make a comment on what would be the optimum transformer rating for this?
Thanks in advance.
Joshua
Attachments
In a past I tried some larger transformers, but the effect wasn't that good and presently 400VA would be maximum I recommend for either stereo or dual mono version.
If you don't want to use Zobel, don't install those parts, placing jumpers could actually set the whole thing on fire.
ChristianL said:
If you don't want to use Zobel, don't install those parts, placing jumpers could actually set the whole thing on fire.