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Post by Deleted on Mar 4, 2012 22:14:21 GMT
No fans.... you will always hear them.
Convection cooling seems the best way..
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Post by floriangerard51 on Mar 5, 2012 1:34:48 GMT
ok then i'll go with a heatsink like this one: uk.farnell.com/abl-heatsinks/520ab1000mb-t03/heat-sink-to-3-1-4-c-w/dp/253728That's exactly the heigh of the amp in the pictures....100mm of height. That's should be better to get it running colder and even more if i want to get a better classA mod like you said before... HAve you the formula for the LMs? What the output value we went to get? Just to know what type of resistor i should get.... ;-) Another question, If i run cable from the back anode 1, anode 2 and ground to the back plastic plate and put some pin connector to get an easyest way to mesure the bias voltage, du you think it could be bad for the amp? like interferance? Antenna effect??? |
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Post by Deleted on Mar 5, 2012 7:49:34 GMT
You could increase the idle current to 0.6A (per channel)
This would mean your regulated power supply should at least be able to handle 1.8A.
the resistors would become: 1.25V/0.6A = 2.1 Ohm (so 2.2 Ohm giving 0.58A idle current)
The heatsinks (when air can flow freely) will be getting 20oC hotter than the surrounding air.
The output resistance can be lowered to 1 Ohm if desired (max 120 Ohm).
wires:
I would not recommend that.
What you can do is connect a small resistor (1k or something) in series with that measuring wire and measure on the source (+ of the output caps).
Those wires can be pulled to the back without much problems.
In this case the correct voltage is not 13.5 at that point but you must adjust around 11.5V at that specific point.
This will result in 13.5V actual bias voltage.
The bias point itself is rather high-Ohmic and the amp is already open frame.
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Post by floriangerard51 on Mar 6, 2012 10:24:52 GMT
where are located the output reistors???they are 47ohms normally?
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Post by Deleted on Mar 6, 2012 14:39:09 GMT
Follow the trace from the - of the output cap to the headphone socket. the resistor in it's path are the output reisistors.
They are very close to the output socket.
Mkae sure you do not mix them up with the resistors from the output socket to ground.
They must stay there and the value must be the same.
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Post by floriangerard51 on Mar 6, 2012 20:16:28 GMT
Ok i changed the adj resistor to 2.2 And the temp at heatsink surface is running 58°c! I think i'll change the resistor to 4 or 5 no? Thats quite hot And you havent seen the heats inks I have placed! Double the size of the black ones...on the picts...
I will tomorrow check the output resistors...
And when I finish I'll write the tuto...
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Post by floriangerard51 on Mar 7, 2012 9:33:46 GMT
Ok I made a test this morning, I'm running the fans provided with the heatsink ( one article cooling l2 pro on each side) and with a small l7805cv I'm feeding the two fans.... Nothing audible at the moment....and the heatsinks are now at nothing more 24degrees!!! Incredible from the 58-60 to 24 now with minimals fans....
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Post by Deleted on Mar 7, 2012 11:09:39 GMT
As long as the fan noise doesn't bother you it is a good way.
Heatsinks only work correctly when there is air flow is correct or forged (fans).
Placing the bottom of a passive heatsink on a surface (table for instance) severly compromises free air flow hence the high temperatures.
heatsinks intended for forged air flow (those that need a fan) generally have realtively very poor passive heat radiation characteristics due to their construction which is optimised for a certain type of air flow.
How does the amp sound with all these mods ?
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Post by floriangerard51 on Mar 7, 2012 11:34:17 GMT
Well the amp sound very good in fact ! I'm finally quite surprised buy the sound that comes from a small hybrid amp like this one....! I still did not test the linear supply because I'm waiting for the lt1083 to be shipped from us....and I did not change the output resistors.
Do you think output resistor will give me better results? How to get a bit more volume choice from the main pot? Cauz I can run the amp from zero to 1/4 turn max....the volume is more than amplified....;-) do I need to change the alps pot or the output resistors change will give me more range from the pot?
A small test review between my little dot mkiii and this one give me more more soundstage on the mkiii....the 12au7 give good treble bass and mids but there is a lake of soundstage clearly. But the price is not that much different finally with the mods done on the bravo. The mkiii is sell for Something like 200€...considering he has a case...
The tiny bravo will fit in my office for working hours, and the mkiii still have is place in my home...;-) until I'll received my lafigaro 339...
Well I think the tuto will be finished by the end of the week...it was a great work and many thanks solderdude for your precious help within this small DIY project!
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Post by Deleted on Mar 7, 2012 12:44:42 GMT
Do you think output resistor will give me better results? The HD650 might sound a tad better in the lows (and thus appearing to boost the highs) when changing from 47 Ohm to 1 Ohm. The differences may not be very big, around 1dB max around 100Hz. How to get a bit more volume choice from the main pot? Cauz I can run the amp from zero to 1/4 turn max....the volume is more than amplified....;-) do I need to change the alps pot or the output resistors change will give me more range from the pot? It seems likely to replace the pot for a log type. Yours appears to be linear as far as I can see from the posted pics. Another quick fix (that has some disadvantages as well) can be to mount a resistor of 1k Ohm (each channel one) from the middle pin of the volpot to ground (the outer pins of the pot that are connected together). Another way is to add resistors in the input path. 2 in a divider form or one in series with input connector and volpot. Another option is to lower the input level by adding an extra resistor in series between the input connector and the 'hot' input pin of the volpot. This involves cutting wires. |
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Post by floriangerard51 on Mar 7, 2012 13:34:51 GMT
Ok then I'll change the resistors....
For the vol pot, I'll buy a log type . What is the pot max value?
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Post by Deleted on Mar 7, 2012 13:45:52 GMT
anything between 5k and 50k will do.
I suggest to use 10k or 20k (25k)
You can test if your pot is linear.
Set it to 12 o'clock setting (with noting connected to the input and switched off)
measure resistance between middle pin and ground.
If the measured value is around 5k it's linear.
If more in the direction of 1k it's log type.
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Post by floriangerard51 on Mar 7, 2012 17:05:16 GMT
that's 5K a 12 oclock and at 6 oclock (min) that's 10k....It's a linear one.
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Post by floriangerard51 on Mar 7, 2012 17:25:58 GMT
also i saw when i was changing the output resistors, that it is not a 47ohms in parallal with a 3Kohms to the ground, that's a 1kohms to the ground....Does it change anything???
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Post by floriangerard51 on Mar 7, 2012 17:55:03 GMT
ok true it's quite better with the output resistor change! that's much much better oversound is better! i put 2.2ohms resistors as i don't have 1ohms ;-) That's very great!!!! Just a point, the LMs and Mosfet are running as hot as i can't leave my finger on the black.....the heatsinks are really low in temperature since they have the fans but the black bodys remains very very hot...is it a problems?  Well guys i would like you to test this small modded amp! that's just so much fun ;-)))) |
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Post by floriangerard51 on Mar 7, 2012 18:01:39 GMT
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Post by floriangerard51 on Mar 7, 2012 18:03:08 GMT
i havent said but for english speaking people you have to click on the:
Télécharger ce fichier
meaning download this file.....that's a french provider page for sending big big file over 1Go or more....
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Post by luin on Mar 7, 2012 21:27:15 GMT
This is the soution I used for the over heating... Inspired in the pics of the sunrise  Cheap and effective....  Cheers |
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Post by Deleted on Mar 7, 2012 21:40:54 GMT
also i saw when i was changing the output resistors, that it is not a 47ohms in parallal with a 3Kohms to the ground, that's a 1kohms to the ground....Does it change anything??? Nope the 1k to the ground is only there to pull the output caps low when no headphone is connected. The 1k is in parallel with the headphone. the output resistor is in series with it. Otherwise when connecting a headphone to an amp that is already on you would hear an extremely loud 'plop' |
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Post by Deleted on Mar 7, 2012 21:41:38 GMT
that's 5K a 12 oclock and at 6 oclock (min) that's 10k....It's a linear one. I figured as much judging from the pics.  |
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Post by Deleted on Mar 7, 2012 21:45:07 GMT
ok true it's quite better with the output resistor change! that's much much better oversound is better! i put 2.2ohms resistors as i don't have 1ohms ;-) That's very great!!!! Just a point, the LMs and Mosfet are running as hot as i can't leave my finger on the black.....the heatsinks are really low in temperature since they have the fans but the black bodys remains very very hot...is it a problems? Well guys i would like you to test this small modded amp! that's just so much fun ;-)))) I would remove the heatsink compound. The silicone already acts as one. Adding heatsink compound only adds to the thermal resistance. When using that stuff it is VERY important the layer must be as thin as possible. after applying that stuff wipe the stuff off with a creditcard (or something similar). When it ouzes out while tightening the screw it is TOO much. 2.2 Ohm is fine for HD650 |
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Post by floriangerard51 on Mar 7, 2012 21:51:35 GMT
no with the new heatsink i havnt put any compound, just the silicone...
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Post by floriangerard51 on Mar 8, 2012 8:49:02 GMT
One question i use a l7805cv for the fans ans i realize that i can hear a small noise on the right channel...nothing on the left. I use à 0.33uf on the input and a 0.1uf on the output of the 7805...do you have any idea of how to get à better filter?
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Post by Deleted on Mar 8, 2012 10:16:37 GMT
Is the noise gone with fan's off ?
Do you use the L version ? (TO-92) or the TO-220 version ?
Are the decoupling caps soldered with very short wires directly to the reg ?
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Post by floriangerard51 on Mar 8, 2012 11:37:07 GMT
Yes With fans of no noise...i was thinking of the proximity of right Channel but test done With distanci
Ng the 7805 without getting less noise...thats a to220...
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