Hi Platenspeler, I just read your description of building your LM1875 Gainclown.
I like the idea of using the aluminium tube for heatsinking but it would be much more efficient to mount it vertically. Then with suitable holes made in the base of the housing, and in the lid, you would have a 'chimney' effect which is the next best thing to having a fan.
Although my Gainclones don't get hot, I may try and find some aluminium tube for my next ones and make the above arrangement.
I like the idea of using the aluminium tube for heatsinking but it would be much more efficient to mount it vertically. Then with suitable holes made in the base of the housing, and in the lid, you would have a 'chimney' effect which is the next best thing to having a fan.
Although my Gainclones don't get hot, I may try and find some aluminium tube for my next ones and make the above arrangement.
Yesterday I made some new 1.5 metre speaker cables to try with my GC's.
I used bell wire (0.6mm) and started by removing all of the insulation. I passed each conductor through a 150cm bootlace and fitted speaker plugs on one end (the speakers I am using have spring terminals for bare wires).
I expected the bass to diminsh substantially but to my surprise it just tightened up, went deeper and seemed to increase!
As you would expect with tinned wire, not burned in, the sound is a bit on the grainy side and I also felt that the mid and high frequencies were a little attenuated and 'dry'.
When I went back to the 79 strand cables, the bass seemed flabby in comparison but the mid and high frequencies had that lovely silky sound that makes the GC's a pleasure to listen to.
I will repeat the experiement with OFC wires and then maybe do a combination cable using a solid core and small stranded cable together.
I used bell wire (0.6mm) and started by removing all of the insulation. I passed each conductor through a 150cm bootlace and fitted speaker plugs on one end (the speakers I am using have spring terminals for bare wires).
I expected the bass to diminsh substantially but to my surprise it just tightened up, went deeper and seemed to increase!
As you would expect with tinned wire, not burned in, the sound is a bit on the grainy side and I also felt that the mid and high frequencies were a little attenuated and 'dry'.
When I went back to the 79 strand cables, the bass seemed flabby in comparison but the mid and high frequencies had that lovely silky sound that makes the GC's a pleasure to listen to.
I will repeat the experiement with OFC wires and then maybe do a combination cable using a solid core and small stranded cable together.
heat tube
Nuuk,
Thanks for the suggestion, for the next project it may be worth trying. I was wondering whether two holes in the top of the bar would help with the heat dissipation. I did this with the other clone.
Thi clo(w)ne is playing 1 hour now on the maximum accepted "family" level in my living room.
The amp gets warm where the alu bar is mounted, but the temperature is not excessive. Still I want to do a few tests and make photographs so I will open it later this day ..
Maarten
Nuuk,
Thanks for the suggestion, for the next project it may be worth trying. I was wondering whether two holes in the top of the bar would help with the heat dissipation. I did this with the other clone.
Thi clo(w)ne is playing 1 hour now on the maximum accepted "family" level in my living room.
The amp gets warm where the alu bar is mounted, but the temperature is not excessive. Still I want to do a few tests and make photographs so I will open it later this day ..
Maarten
Good morning Maarten, it looks like we are the early 'cloners' today 
You could try holes in the top of the tube, or even in the sides of the case although I appreciate the problem of cutting that steel
It does seem, if the clones don't have a problem like oscillation, that they run at reasonable temperatures but I do like to keep anything electronic as cool as possible, if only to lengthen the life of components such as capacitors.
You could try holes in the top of the tube, or even in the sides of the case although I appreciate the problem of cutting that steel
It does seem, if the clones don't have a problem like oscillation, that they run at reasonable temperatures but I do like to keep anything electronic as cool as possible, if only to lengthen the life of components such as capacitors.
Nuuk,
It's earlier for you than it is for me
I find it difficult to determine when warm becomes too-hot. Especially since the LM1875 with it's 20W power rating will run warmer than it's brother based on the LM3875.
My wife has one of those temp. sensors in the kitchen. I use it every now and then to conduct temp. measurements with audio setups.
I might drill two additional holes when necessary.
thanks,
Maarten
It's earlier for you than it is for me
I find it difficult to determine when warm becomes too-hot. Especially since the LM1875 with it's 20W power rating will run warmer than it's brother based on the LM3875.
My wife has one of those temp. sensors in the kitchen. I use it every now and then to conduct temp. measurements with audio setups.
I might drill two additional holes when necessary.
thanks,
Maarten
Nuuk,
Tidying up the house is not my hobby. Wish you courage
I just realized that the higher temperature is also due to the fact that there are two opamps mounted on a bar which is the same size as the bar I connected one LM3875 to on the last project.
With each idividual LM1875 probably dissapating more heat than a LM3875 on same listening level ... hmmm ... work to do
Maarten
Tidying up the house is not my hobby. Wish you courage
I just realized that the higher temperature is also due to the fact that there are two opamps mounted on a bar which is the same size as the bar I connected one LM3875 to on the last project.
With each idividual LM1875 probably dissapating more heat than a LM3875 on same listening level ... hmmm ... work to do
Maarten
TDA7294 / standby and mute
Peter,
sorry for the late answer - I do not have time to check and read this enormous thread as regularily as I would wish.
No I was wrong, I must admit, I am sorry to have caused any confusions. Pin 9 and pin10 must be positive (>3.5V) to activate the amp, according to the schematics shown in the spec-sheet.
Peter,
sorry for the late answer - I do not have time to check and read this enormous thread as regularily as I would wish.
No I was wrong, I must admit, I am sorry to have caused any confusions. Pin 9 and pin10 must be positive (>3.5V) to activate the amp, according to the schematics shown in the spec-sheet.
LM3875 isolation
I am using the noninsulated version of this chip. I know that it is "electrically active."
Could someone please explain this in more detail. Particularly, in regards to ground. Can the metal surface to which the chip is mounted be the star ground?
Furthermore, I have seen some amps that have been built where the left and right channel chips are mounted on the same heat sink, but I do not know if they are mounted on an insulating pad or with just thermal compund. Would this type of mounting affect stereo separation?
Thanks.
I am using the noninsulated version of this chip. I know that it is "electrically active."
Could someone please explain this in more detail. Particularly, in regards to ground. Can the metal surface to which the chip is mounted be the star ground?
Furthermore, I have seen some amps that have been built where the left and right channel chips are mounted on the same heat sink, but I do not know if they are mounted on an insulating pad or with just thermal compund. Would this type of mounting affect stereo separation?
Thanks.
Vic,
the mounting tab of the chip is at V- voltage and not on ground levels. It is possible not to use an isolation washer but then you have to isolate the heatsink or whatever you mount the chip on from the ground since the whole heatsink will be at V- level.
It is perfectly possible to make the heatsink your starground. I used one aluminum bar for the GainClown project (See http://www.platenspeler.com/diy/uk_index.html) on which I mounted both chips with an isolation washer and in the middle between both chips I made the star ground.
And if you make a monoblock it's perfectly possible to use the isolation set (mine even contained a soldering lug for that) and make that your star ground. Still, no electrical contact between chip and heatsink.
When making an integrated amp I would isolate both chips separately. After all, you give them each their own power caps in order to make sure they do not interact.
maarten
the mounting tab of the chip is at V- voltage and not on ground levels. It is possible not to use an isolation washer but then you have to isolate the heatsink or whatever you mount the chip on from the ground since the whole heatsink will be at V- level.
It is perfectly possible to make the heatsink your starground. I used one aluminum bar for the GainClown project (See http://www.platenspeler.com/diy/uk_index.html) on which I mounted both chips with an isolation washer and in the middle between both chips I made the star ground.
And if you make a monoblock it's perfectly possible to use the isolation set (mine even contained a soldering lug for that) and make that your star ground. Still, no electrical contact between chip and heatsink.
When making an integrated amp I would isolate both chips separately. After all, you give them each their own power caps in order to make sure they do not interact.
maarten
Peter,
I used an aluminum bar for cooling, and then it works out quite well.
But you're right, I would not use a heatsink as a starground but instead select a place close to the chip with enough space to run all kinds of wire to.
A picture of the starground in GainClown:
Maarten
I used an aluminum bar for cooling, and then it works out quite well.
But you're right, I would not use a heatsink as a starground but instead select a place close to the chip with enough space to run all kinds of wire to.
A picture of the starground in GainClown:
An externally hosted image should be here but it was not working when we last tested it.
Maarten
Elso,
I know, but it's the price you pay when you need to mount two 5-pin amps on 9 cm auluminum and connect it to 6 resistors, 4 caps, 2 inputs, 1 pot and 4 speakerterminals with the intention of making all connections as short as possible.
Fortunately the picture taken from 5 cm or so looks much more messy than the original from 50 cm distance
My own tube projects look better too even from close distance.
Maarten
I know, but it's the price you pay when you need to mount two 5-pin amps on 9 cm auluminum and connect it to 6 resistors, 4 caps, 2 inputs, 1 pot and 4 speakerterminals with the intention of making all connections as short as possible.
Fortunately the picture taken from 5 cm or so looks much more messy than the original from 50 cm distance
My own tube projects look better too
even from close distance.An externally hosted image should be here but it was not working when we last tested it.
Maarten
telephone cable
I don't know. This was 20 meters surplus left over by the phone company when they did the ADSL install in my place.
No brand name on cable either.
Today I made some interconnects with shoe laces around this wire, as suggested above.
/Jan
Matttcattt said:
where can i get some?
I don't know. This was 20 meters surplus left over by the phone company when they did the ADSL install in my place.
No brand name on cable either.
Today I made some interconnects with shoe laces around this wire, as suggested above.
/Jan
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