Thanks for the response s3tup.
The hum is approx 70-80 Hz.
When I swap out the board (connecting the working board to the same power supply and input source) I get nice clean music, so I believe it must be the board... Incidentally, I get hum even with no input connected (only not as loud as when there's input).
I'm not at home right now but I'll upload pics this evening.
Thanks again
The hum is approx 70-80 Hz.
When I swap out the board (connecting the working board to the same power supply and input source) I get nice clean music, so I believe it must be the board... Incidentally, I get hum even with no input connected (only not as loud as when there's input).
I'm not at home right now but I'll upload pics this evening.
Thanks again
Check the resistance between input and ground on both boards when everything is off. It feels like the ground is missing on input of the faulty board. Maybe that's the issue.
Alternatively, you can A/B check the resistor impedances everywhere to find the difference, as you have a good board for reference. If you'll find a difference, it will be easy to pin-point the cause.
Visually check the IRS IC - it's package is small, and there may be some leftovers from soldering/rosin. The rosin may start being conductive, and give some resistance between pins.
Check the resistance of input capacitor, it should be open (very high). Again, verify with working board... It will look like shortcircuit when you start measuring, it will rise to some point during measurement. Note the polarity of probes when doing A/B.
Alternatively, you can A/B check the resistor impedances everywhere to find the difference, as you have a good board for reference. If you'll find a difference, it will be easy to pin-point the cause.
Visually check the IRS IC - it's package is small, and there may be some leftovers from soldering/rosin. The rosin may start being conductive, and give some resistance between pins.
Check the resistance of input capacitor, it should be open (very high). Again, verify with working board... It will look like shortcircuit when you start measuring, it will rise to some point during measurement. Note the polarity of probes when doing A/B.
Well, I had the opportunity to look at this again last night... I disconnected both boards from their PS's & checked the boards out as per s3tup's suggestions. I couldn't find any discrepancy (frustrating). I took my soldering iron to all the solder joints again (for lack of any better ideas). I reconnected the trouble board to the PSU, fired it all up and the humm is gone!!!
Obviously this had me smiling, but at the same time I wish I was able to pinpoint the problem and deliberately fix it.
At least now I can continue with my build
Thanks again for your help s3tup.
Justin
Obviously this had me smiling, but at the same time I wish I was able to pinpoint the problem and deliberately fix it.
At least now I can continue with my build
Thanks again for your help s3tup.
Justin
Well, I had the opportunity to look at this again last night... I disconnected both boards from their PS's & checked the boards out as per s3tup's suggestions. I couldn't find any discrepancy (frustrating). I took my soldering iron to all the solder joints again (for lack of any better ideas). I reconnected the trouble board to the PSU, fired it all up and the humm is gone!!!
Obviously this had me smiling, but at the same time I wish I was able to pinpoint the problem and deliberately fix it.
At least now I can continue with my build
Thanks again for your help s3tup.
Justin
You did ...
I noticed the 2 r117 resisters (5k1/2watt) get extremely hot (too hot to touch) on the L25D board. Is this normal? (using -+77v rails @ 8R)
I guess, in a way but it's nice to be able to find the culprit.
You did ...
I guess, in a way but it's nice to be able to find the culprit.
True, but at least you know it was one of those solder joints.. sometimes a shotgun is the right tool for the job..
Re your resistor issue, there was a mention of "hot resistors" on one of the threads (L15D or L20D) and ljm_ljm did suggest that they be swapped with 2Watt resistors instead.. thanks for reminding me about that.. I'll want to do the same on my L15D's
Hi,
I've purchased two L25D at ebay and wanted to use a SMPS 500R from Connexelectronic. But I wonder which voltage I should use. There's the possibility that the amp will power 4 Ohm speakers or 8 Ohm speakers. The SMPS can be ordered in +/-60 V or +/-72 V. From my point of view it is more important to me to have the flexibility concerning the impedance of the speakers than to have the full power the amps are capable of. So could you tell me which voltage to choose?
Thanks a lot
Sven
I've purchased two L25D at ebay and wanted to use a SMPS 500R from Connexelectronic. But I wonder which voltage I should use. There's the possibility that the amp will power 4 Ohm speakers or 8 Ohm speakers. The SMPS can be ordered in +/-60 V or +/-72 V. From my point of view it is more important to me to have the flexibility concerning the impedance of the speakers than to have the full power the amps are capable of. So could you tell me which voltage to choose?
Thanks a lot
Sven
Hi.
Similarly, I've purchased two L25D from ebay and want to use an existing power supply (very "stiff" +/-75vdc dual channel) from an old 200wpc (high-end) stereo power amp.
My woofers are 4ohms, and am hoping to get good results here, replacing a pair of 10 year old 250W plate amps...
Any experience or advice here?
-Chas
Similarly, I've purchased two L25D from ebay and want to use an existing power supply (very "stiff" +/-75vdc dual channel) from an old 200wpc (high-end) stereo power amp.
My woofers are 4ohms, and am hoping to get good results here, replacing a pair of 10 year old 250W plate amps...
Any experience or advice here?
-Chas
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I have built a 2092 with 2 off IRFB4227 and it sounds very good.
I have also built a 750 watt with 4 off IRFB4227 into 2 ohms and that sounds great too.
To drive the 4227's I used TC4420 driver chips.
I'm assuming that your very "stiff" +/-75vdc dual channel supply is a linear unregulated transformer/bridge. The key is how high the idle voltage will be, since the idle dissipation of the 2 channels will be only ~15W. 70v gives 350W into 2 ohms must be a typo, as I think it's more like 350W into 4 ohms.Just wondering if anyone here used such high voltage rails, as the ad said 70v gives 350W into 2 ohms...
You really need to figure out a few things, though. I'm not sure from your posts whether you have 2 or 4 channels, but your L25Ds driving 4 Ohms per channel could deliver up to 1.4KW if your very "stiff" supply really were. Regardless how high-end your 200W amp was, I doubt the supply has that much margin. If it does, then that explains why many audiophile equipment companies don't stay in business.
If you know you'll be driving 4 Ohm loads only, then you'd be much better off with a lower voltage supply, such as +/- 50V unless you're really looking for 350W/ch. If you're going to stick with your "stiff" +/-75vdc dual channel supply, then you need to figure out the supply's load regulation over the load range you expect in your application to make sure it's acceptable for your L25Ds.
TC4420
Hi Nigelwright7557
greetings
Quote:
Originally Posted by solviken View Post
So from what i read there are lots of people building these amps! But no one has posted anything about how they sound, and how they compare in sound quality to other Diy amps. ?? Can anyone please share their opinion?
I have built a 2092 with 2 off IRFB4227 and it sounds very good.
I have also built a 750 watt with 4 off IRFB4227 into 2 ohms and that sounds great too.
To drive the 4227's I used TC4420 driver chips
TC4420EPA or TC4420MJA which one do you use to drive IRFB4227
warm regards
andrew lebon
Hi Nigelwright7557
greetings
Quote:
Originally Posted by solviken View Post
So from what i read there are lots of people building these amps! But no one has posted anything about how they sound, and how they compare in sound quality to other Diy amps. ?? Can anyone please share their opinion?
I have built a 2092 with 2 off IRFB4227 and it sounds very good.
I have also built a 750 watt with 4 off IRFB4227 into 2 ohms and that sounds great too.
To drive the 4227's I used TC4420 driver chips
TC4420EPA or TC4420MJA which one do you use to drive IRFB4227
warm regards
andrew lebon
This was a PS Audio 200C, a 70lb monster with a huge transformer and 20,000ufd of computer-grade cans each channel. It was rated (and reviewed by Stereophile) for 200wpc/8ohms, 400wpc/4ohms and 1,000wpc into 1.5 ohms! I'd say the supply has the margin for this application; The question is: is the amp capable of handling the supply and the load (nominal 6ohms, 4ohms min).
-Chas
Tiny phase inverter for L15 , 20 and 25 D
I build this tiny phase inverter to drive 2 of the 5 amps in my HT amp with 5 L15D’s with opposite phase to avoid bus pumping .
The schematic is from the reference design IRAUDAMP7D REV 2.8 page 32
The PCB measures 16 x 16 mm and fits well under the amp with double sided tape . You’ll need some higher stand offs .
Works great
The scope pic is driving my front channels in a 4 ohm dummyload .
The decoupling caps are mounted in the IC socket
I build this tiny phase inverter to drive 2 of the 5 amps in my HT amp with 5 L15D’s with opposite phase to avoid bus pumping .
The schematic is from the reference design IRAUDAMP7D REV 2.8 page 32
The PCB measures 16 x 16 mm and fits well under the amp with double sided tape . You’ll need some higher stand offs .
Works great
The scope pic is driving my front channels in a 4 ohm dummyload .
The decoupling caps are mounted in the IC socket
Attachments
With reference to power supplies:
LJM recommends a psu board earlier in this thread with many capacitors. Can these run a stereo pair of boards or do I need to buy one for each amplifier board? They seem to have 25A rectifiers. Is this the limiting factor, and will 25A be enough to power two boards with +/-70V (2 x 50Vac transformer)?
I am trying to decide whether to go for a linear PSU with the above PSU board (more expensive) or SMPS from connexelectronics for my 8 channel power amp (8 x L25D boards).
Kind regards,
Jai
LJM recommends a psu board earlier in this thread with many capacitors. Can these run a stereo pair of boards or do I need to buy one for each amplifier board? They seem to have 25A rectifiers. Is this the limiting factor, and will 25A be enough to power two boards with +/-70V (2 x 50Vac transformer)?
I am trying to decide whether to go for a linear PSU with the above PSU board (more expensive) or SMPS from connexelectronics for my 8 channel power amp (8 x L25D boards).
Kind regards,
Jai