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nishant's β24+α10 integrated amp build log

beta24

Re: nishant's β24+α10 integrated amp build log

Postby tommarra » October 2nd, 2013, 6:43 am

Quick update on the build - all parts for the β24 boards and power supply have been ordered...it was a big charge on the credit card.

All inclusive, the integrated β24+α10 is going to run me ~$1800. Which includes the transformer, Chasis and all the parts.

Lets hope I can build it to sound as good :-)
AMB Projects built: B22 (Active ground), S22, S25, LCDunio, D1, D2, A20
AMB Projects in progress: A10+B24 integrated amplifier
http://www.amb.org/forum/nishants-beta24-alpha10-integrated-amp-build-log-t2193.html
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Re: nishant's β24+α10 integrated amp build log

Postby tommarra » October 6th, 2013, 3:22 pm

Got all the parts from AMB Shop and Mouser, and started the build again. This weekend completed the build for the two Sigma 22 36V power supplies.

Here are a few pictures of the build

S22 for B24 1.jpg


S22 for B24 2.jpg



I have a couple of questions on this though.

1. Unequal voltage for two supplies:

One of the power supplies is giving an output of 34.1V, where as the other is 33.53V. Is this a problem? The build calls for a 36V power supply.

How do I get 36V output. I have used all the parts specified in the parts list on the S22 page.

2. Blown fuse:

While doing the initial test, I first connected the transformer to the 1st power supply. After confirming that it was working fine, I unplugged the AC mains and connected the second power supplies. When I switched it on, the blue LEDs came on for both the supplies. However, when I started doing the voltage check on the second power supply, the 2A inline fuse blew out.
I tested the second power supply for shorts and not finding any short, I replaced the fuse and plugged it in again. This time, everything functioned the rightway.

Why did the first fuse blew-out? I do not think that no-load S22 draws 2A worth of current? Any ideas, why the fault when i started taking the voltage measurements?


P.S: The transformer in the background is a Richard Sumr's encapsulated transformer with dual primaries, 4x 36V secondaries, 4x 30V secondary and 1x 12V secondary. Total power of 550W.
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AMB Projects built: B22 (Active ground), S22, S25, LCDunio, D1, D2, A20
AMB Projects in progress: A10+B24 integrated amplifier
http://www.amb.org/forum/nishants-beta24-alpha10-integrated-amp-build-log-t2193.html
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Re: nishant's β24+α10 integrated amp build log

Postby amb » October 7th, 2013, 12:53 am

1. It's not a problem that both voltages are slightly low. It's most likely due to tolerances in the D5 zener diode (measure across them and you'll probably read lower than exactly 12.0V. Since the error amp's gain is 3 to get 36V, any zener tolerance is also multiplied by 3. If you're really bothered by this, get a handful of diodes, test each one and select ones that are closest to 12.0V.

2. Was the blown fuse a fast acting fuse? With two σ22s, even though there is no load, there is still a surge current at turn on when the transformer is energizing up its magnetic field, and also to charge up the bulk capacitors on the σ22 boards. If the fuse is fast acting, then the combined current may be just close enough to its rating to blow it. Is your 2nd fuse also fast acting? If so then maybe it works because of fuse tolerances, or perhaps the 1st fuse was not up-to-spec, or possibly there was an accidental short circuit (tools, DMM probes, other metal bits nearby?).
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Re: nishant's β24+α10 integrated amp build log

Postby tommarra » October 7th, 2013, 6:12 am

amb wrote:1. It's not a problem that both voltages are slightly low. It's most likely due to tolerances in the D5 zener diode (measure across them and you'll probably read lower than exactly 12.0V. Since the error amp's gain is 3 to get 36V, any zener tolerance is also multiplied by 3. If you're really bothered by this, get a handful of diodes, test each one and select ones that are closest to 12.0V.


Great. As long as the difference in voltages doesnt impact the audio quality, I will not desolder the existing zeners.

However out of curiosity, what is the fastest way to test and swapout zener diodes without soldering them on and off the board?
amb wrote:2. Was the blown fuse a fast acting fuse? With two σ22s, even though there is no load, there is still a surge current at turn on when the transformer is energizing up its magnetic field, and also to charge up the bulk capacitors on the σ22 boards. If the fuse is fast acting, then the combined current may be just close enough to its rating to blow it. Is your 2nd fuse also fast acting? If so then maybe it works because of fuse tolerances, or perhaps the 1st fuse was not up-to-spec, or possibly there was an accidental short circuit (tools, DMM probes, other metal bits nearby?).


Yes the blown fuse as well as the fuse i have put in now are fast acting ones. The σ22s are working fine, so I am not too worried about it. As you said, It might have been a combination of an old fuse and the surge current from two boards.
AMB Projects built: B22 (Active ground), S22, S25, LCDunio, D1, D2, A20
AMB Projects in progress: A10+B24 integrated amplifier
http://www.amb.org/forum/nishants-beta24-alpha10-integrated-amp-build-log-t2193.html
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Re: nishant's β24+α10 integrated amp build log

Postby tommarra » October 7th, 2013, 10:13 am

I have a question:

I will be done soldering components for atleast one β24 amplifier board today. In order to test if everything works on it, is it okay to power it on without the heatsinks attached (with no Load).

I have not ordered the chassis from Hifi2000 yet, but want to make sure that the board works properly.

Or should I wait for the chasis to arrive, and attached the output MOSFETs to the heatsink before powering on
AMB Projects built: B22 (Active ground), S22, S25, LCDunio, D1, D2, A20
AMB Projects in progress: A10+B24 integrated amplifier
http://www.amb.org/forum/nishants-beta24-alpha10-integrated-amp-build-log-t2193.html
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Re: nishant's β24+α10 integrated amp build log

Postby amb » October 7th, 2013, 1:01 pm

tommarra wrote:However out of curiosity, what is the fastest way to test and swapout zener diodes without soldering them on and off the board?

You can measure them offboard by connecting a power supply and a series resistor, then measure the voltage drop across the zener. If you use a 24V supply, and you're measuring a "12V" zener, then the resistor has to drop 12V. If you want around 2mA to flow through the zener, then the resistor value should be 12V / 0.002A = 6K ohms. You can use a 5.6K standard value resistor.
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Re: nishant's β24+α10 integrated amp build log

Postby tommarra » October 8th, 2013, 6:14 am

amb wrote:You can measure them offboard by connecting a power supply and a series resistor, then measure the voltage drop across the zener. If you use a 24V supply, and you're measuring a "12V" zener, then the resistor has to drop 12V. If you want around 2mA to flow through the zener, then the resistor value should be 12V / 0.002A = 6K ohms. You can use a 5.6K standard value resistor.


Thanks! Why didnt I think of that! :?

Chasis Question for : I was looking at a few chasis from SiliconRay. And found a chasis that has 142mm of internal height. Quickly checking the width of the β24 revealed that it is just 115mm. I think that I will be able to fit the board on the heatsink of this case. Any reason why 142mm may not be enough clearance?


http://www.siliconray.com/mechanical/en ... osure.html


However SiliconRay, charge crazy amounts for shipping and handling! For each case they want to charge $95 / box in shipping and handling. Even Hifi2000 dont charge this much for shipping.
AMB Projects built: B22 (Active ground), S22, S25, LCDunio, D1, D2, A20
AMB Projects in progress: A10+B24 integrated amplifier
http://www.amb.org/forum/nishants-beta24-alpha10-integrated-amp-build-log-t2193.html
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Re: nishant's β24+α10 integrated amp build log

Postby amb » October 8th, 2013, 11:26 am

tommarra wrote:Chasis Question for : I was looking at a few chasis from SiliconRay. And found a chasis that has 142mm of internal height. Quickly checking the width of the β24 revealed that it is just 115mm. I think that I will be able to fit the board on the heatsink of this case. Any reason why 142mm may not be enough clearance?

http://www.siliconray.com/mechanical/en ... osure.html

Don't forget that you'll need additional clearance for the MOSFETs on both sides of the board. The hifi2000 case that I used in the reference build has an internal height of 165mm (external 180mm) and it's barely enough.
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nishant's β24+α10 integrated amp build log

Postby tommarra » October 9th, 2013, 8:37 pm

amb wrote:Don't forget that you'll need additional clearance for the MOSFETs on both sides of the board. The hifi2000 case that I used in the reference build has an internal height of 165mm (external 180mm) and it's barely enough.



Point taken...I will order the Hifi2000 case. Silicon ray is another option but their shipping and handling fee is way too high. Also hifi2000 can apparently do panel work on a 10 mm aluminum black panel. Front Panel Express only does it for natural anodized aluminum.


I have another question to add to my seemingly endless list of questions for you :-)

I finished the build for my unregulated power supply...the no load transformer voltage is 35 volts fort transformer....by putting the two secondaries in series as shown in the power supply diagram, I get a total of 70VAC that is applied to the bridge rectifier.

This means that the final full wave rectified DC voltage out is 70 * SQRT(2) = 98.98 VDC. in other words my unloaded V+ is 49.5V and unloaded V- is -49.5V

Does this voltage seem right? I know it is unregulated and under no load condition but is it a bit too high and am I doing something wrong here?

Thanks in advance!

Nishant
AMB Projects built: B22 (Active ground), S22, S25, LCDunio, D1, D2, A20
AMB Projects in progress: A10+B24 integrated amplifier
http://www.amb.org/forum/nishants-beta24-alpha10-integrated-amp-build-log-t2193.html
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Re: nishant's β24+α10 integrated amp build log

Postby amb » October 9th, 2013, 10:28 pm

All is well. Give it a load and the transformer secondary voltage will drop.
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