light bulb testing
Hi,
some posts ago I reported about the light coming from the lightbulb tester of my first chipamp when using a CAT5 self-made speaker cable. AndrewT suggested a possible instability of the chipamp with a higher capacitance cable,
I like to report you my further newbie experience while using the lightbulb tester.
Finally I built a case for my LM1875 chipamp from chipamp.com. No news while driving my Fostex103E BR speakers, it sounds very nice. Then I connected it to my Jordan MLTL-48 (still in progress, they need to be painted).
Again I made this test by using the lightbulb tester. Every thing was just fine with the first records with soft music, but the lightbulb tester lighted when I moved to more power demanding music. It lights just when there are power peaks.
I changed the loudspeakers cables , removed the BSC, without any change.
The sound to me is OK, I would have no concerns if I did use a standard power cable and did not see the light.
Then I connected the lightbulb tester to my commercial integrated amplifier, I own it since 1995; it is an YBA Integré dual mono (2500$/€ current price), a 50 Watt "audiophile" amp as suggested by the reviews of the specialized press.
To my surprise the tester began to light, similarly to the chipamp, but with much higher intensity.
I connected the YBA to the Fostexs: again the light from the tester although with much lower intensity.
Have you some opinion on whati is going on?
In particular I am concerned with the safety issue.
Thank you a lot
Renato
Hi,
some posts ago I reported about the light coming from the lightbulb tester of my first chipamp when using a CAT5 self-made speaker cable. AndrewT suggested a possible instability of the chipamp with a higher capacitance cable,
I like to report you my further newbie experience while using the lightbulb tester.
Finally I built a case for my LM1875 chipamp from chipamp.com. No news while driving my Fostex103E BR speakers, it sounds very nice. Then I connected it to my Jordan MLTL-48 (still in progress, they need to be painted).
Again I made this test by using the lightbulb tester. Every thing was just fine with the first records with soft music, but the lightbulb tester lighted when I moved to more power demanding music. It lights just when there are power peaks.
I changed the loudspeakers cables , removed the BSC, without any change.
The sound to me is OK, I would have no concerns if I did use a standard power cable and did not see the light.
Then I connected the lightbulb tester to my commercial integrated amplifier, I own it since 1995; it is an YBA Integré dual mono (2500$/€ current price), a 50 Watt "audiophile" amp as suggested by the reviews of the specialized press.
To my surprise the tester began to light, similarly to the chipamp, but with much higher intensity.
I connected the YBA to the Fostexs: again the light from the tester although with much lower intensity.
Have you some opinion on whati is going on?
In particular I am concerned with the safety issue.
Thank you a lot
Renato
During demanding music play, there is probably enough current draw to light the bulb. Everything is likely fine if the bulb pulses during demanding music. What would be a concern is if the bulb lit brightly and stayed on (especially when not playing music). That would indicate a short or other problem. If the DC offset at the output is fine, and music comes out, you should probably remove the light bulb tester to get the full power/quality the amp can deliver.
If anyone cares, I am going to have some boards burned which will approximate what National describes in application note 1849 -- only thing is that I prefer MUR860's to bridge rectifiers and a pants-n-suspenders approach to snubbers -- with TH's setup you have the provision for slow-start and mute etc. There'll also be a provision for auxiliary power for a buffer etc.:
http://www.national.com/an/AN/AN-1849.pdf
http://www.national.com/an/AN/AN-1849.pdf
yes, it's a tester to allow safe/undamaging startup of a new or modified project.
The positive temperature coefficient of the tungsten filament does not suit operational use. Even the negative temperature temp coef of a power thermistor modulates the transformer voltage and can be seen in the lower clipping of output signal.
The positive temperature coefficient of the tungsten filament does not suit operational use. Even the negative temperature temp coef of a power thermistor modulates the transformer voltage and can be seen in the lower clipping of output signal.
An externally hosted image should be here but it was not working when we last tested it.
or read the DD site very well!
Alright so I've tested my psu. I have an amveco dual secondary/dual primary toroid. It's rated at 140VA with 24V per secondary.
Now I thought the Voltage was supposed to be 1.4 times greater after the bridge? But I measured 24V DC on the nose coming out of my rectifier. I'm thinking I was wrong about the 1.4 factor, just want to make sure I'm not headed for a catastrophe.
Now I thought the Voltage was supposed to be 1.4 times greater after the bridge? But I measured 24V DC on the nose coming out of my rectifier. I'm thinking I was wrong about the 1.4 factor, just want to make sure I'm not headed for a catastrophe.
|Vcc|+|Vee|<=84Vdc.
If a dual polarity supply is used then <=+-42Vdc.
this is absolute max for which National Guarantee the Chip.
But, you must allow for worst case conditions. Maximum mains supply voltage, minimum current draw from the PSU (all but one channel disconnected)
The normal maximum transformer voltage is 28Vac but many builders refuse to go higher than 25Vac when driving 8ohm speakers.
If a dual polarity supply is used then <=+-42Vdc.
this is absolute max for which National Guarantee the Chip.
But, you must allow for worst case conditions. Maximum mains supply voltage, minimum current draw from the PSU (all but one channel disconnected)
The normal maximum transformer voltage is 28Vac but many builders refuse to go higher than 25Vac when driving 8ohm speakers.