Interesting...
I tried the tones, set my amps volume level to where I typically listen and measured 0.16V
If I have the house to my self, and am going for it, I go to 3.29V and that's plenty loud enough.
So, considering my speakers efficiency, I need 11 watts clean ;-)
My room is irregular, but about 11 x 19.
So, if I understand it correctly, I typically listen to 1/39th of a watt ?????
.16^2 = .0256
I tried the tones, set my amps volume level to where I typically listen and measured 0.16V
If I have the house to my self, and am going for it, I go to 3.29V and that's plenty loud enough.
So, considering my speakers efficiency, I need 11 watts clean ;-)
My room is irregular, but about 11 x 19.
So, if I understand it correctly, I typically listen to 1/39th of a watt ?????
.16^2 = .0256
Thanks for the report. 0.16 is pretty darn low. 3.3V seems right if your speakers are efficient. A 15 watt amp should cover you.
As for your average power - with that low 0.16 on the test tones, you'd be near 3 milliwatts for that signal. Average music is a little lower. Peaks will be around 0.64 volts or 51 milliwatts into 8 ohms. That does seem suspiciously low so you might want to double check.
NOTE: Your two listening levels are 26dB apart. That's a lot.
As for your average power - with that low 0.16 on the test tones, you'd be near 3 milliwatts for that signal. Average music is a little lower. Peaks will be around 0.64 volts or 51 milliwatts into 8 ohms. That does seem suspiciously low so you might want to double check.
NOTE: Your two listening levels are 26dB apart. That's a lot.
So the average level is when the wife is home, when we just want good clear background music. The high level is only when all of the planets are in alignment, empty house, a beer or three, and in a jamb out mood.
I hardly ever get to that upper level. I enjoy whats left of my hearing.
The question began because I want to build a tube amp. The question of what do I need in terms of max power came up.
I also wondered why my VU meter hardly ever moves. Within the normal range of background music to "this is what we are doing" The VU doesnt move at all. The VU meter was a dead end route, but heck, Im learning....
I saw someone somewhere say try E^2/DCR = P.. Not using test tones, but music at my normal levels and a DMM with max hold on resulted in .25 of a watt as an upper average. Again, thats about as loud as the Mrs likes (Unless its led zep or simmialr
I very much appreciate your responce. While I have always loved listeing, I have only begun to scratch the surface... Between building my elsinores, the ACA, a little tube rolling burrying my head in as much as I can when ever I can, I know that I have barley even smudged (let alone scratched) the surface...
I hardly ever get to that upper level. I enjoy whats left of my hearing.
The question began because I want to build a tube amp. The question of what do I need in terms of max power came up.
I also wondered why my VU meter hardly ever moves. Within the normal range of background music to "this is what we are doing" The VU doesnt move at all. The VU meter was a dead end route, but heck, Im learning....
I saw someone somewhere say try E^2/DCR = P.. Not using test tones, but music at my normal levels and a DMM with max hold on resulted in .25 of a watt as an upper average. Again, thats about as loud as the Mrs likes (Unless its led zep or simmialr
I very much appreciate your responce. While I have always loved listeing, I have only begun to scratch the surface... Between building my elsinores, the ACA, a little tube rolling burrying my head in as much as I can when ever I can, I know that I have barley even smudged (let alone scratched) the surface...
It's a power ratio: 10^0.84 = ~1.2134*140 W = ~170 W transient peak @ 8 ohms. In general, we want at least +3 dB and preferably +6 dB, so implies normal power will be a lot < 140 W...........
GM
Yeah, [140 W/8 ohms]^0.5 = ~4.1833 A * [7] ch = ~29.283 A^2 * 8 ohms = 6860 W!
The sonic structure of a movie soundtrack being what it is, it's doubtful it would ever be called upon to need but a fraction of this much, so maybe they did enough research to know that ~140 W total was all they'd ever need in home, but back in the early days of HT receivers it would have been a simple 140/7 = 20 W/ch * ~1.2134 = ~24.27 W/ch, so am curious what it actually means now.
GM
The sonic structure of a movie soundtrack being what it is, it's doubtful it would ever be called upon to need but a fraction of this much, so maybe they did enough research to know that ~140 W total was all they'd ever need in home, but back in the early days of HT receivers it would have been a simple 140/7 = 20 W/ch * ~1.2134 = ~24.27 W/ch, so am curious what it actually means now.
GM
I keep coming back to this test. Recently I made cheap chinese LM3886 amp so took test again. I measured at three settings. For Normal listening I got 1V. At louder levels which I rarely listen I got around 1.5 V and absolutely high loud levels (Torture tested on 8 ohms Sony Boombox speakers ) I got around 2.2 to 2.8V. I used Center Tapped 18-0-18 (5Amp) transformer. Modules and PS loose (Not in cabinet) and tested with series bulb tester. My questions are...
1) for my normal listening levels I get 1V. For transients peaks I multiplied this voltage with 4. So 4X4 = 16 watts. Which is comfortable for LM3886 type of amplifier. Correct ?
2) When tortured tested at maximum level where I got 2.2/2.8V at loud drums part of music (Dire straits Calling Elvis) the series bulb glow bright in intensity. What does this indicate ?
3) Rookie Question : Having nothing else to do I tested current draw at transformer center tap wire. Multimeter in series at red dots as shown in pic. I got 4.4 Amps. What does this indicate ? This was at very loud listening level.
Thanks very much for the test.
Regards.
1) for my normal listening levels I get 1V. For transients peaks I multiplied this voltage with 4. So 4X4 = 16 watts. Which is comfortable for LM3886 type of amplifier. Correct ?
2) When tortured tested at maximum level where I got 2.2/2.8V at loud drums part of music (Dire straits Calling Elvis) the series bulb glow bright in intensity. What does this indicate ?
3) Rookie Question : Having nothing else to do I tested current draw at transformer center tap wire. Multimeter in series at red dots as shown in pic. I got 4.4 Amps. What does this indicate ? This was at very loud listening level.
Thanks very much for the test.
Regards.
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Maybe I'm not reading far enough up the thread, but I just don't think this sounds right. It looks like a twisted way to go from 140 W into 8 ohms, multiplied by 7 channels equals 6860 W, which we know isn't nearly the case. In fact, the power supply is likely to be pulling approximately 1300 W at full power into all 7 channels. This cannot be reconciled with the 6860 W figure there. Furthermore, due to simple physics, it is highly unlikely that the power supply can sustain 1300 W, and will therefore collapse under continuous load.
I would like to suggest that your calculation should probably read ... ~29.283 A^2 * 1.143 ohms = 980 W (or just 140 W x 7 = 980 W). The 8 ohm loads must be taken as a parallel combination.
The spec is 140 W per channel. Usually the spec will say something like "all channels driven".
Hiten. If your loudest setting results in 2.8V on the test tone, that means your peaks will be around 11.25 volts. A +/- 12V DC supply might just get by. Your 18-0-18 transformer is a good choice.
Are you saying that each channel was pulling 4.4A at full volume? That seems very high, even if your speakers are 4 ohm. That would indicate a little over 17 WPC. Since you aren't doing much more than 1 WPC at that setting, I don't understand the current draw. Can you measure again to double check?
Are you saying that each channel was pulling 4.4A at full volume? That seems very high, even if your speakers are 4 ohm. That would indicate a little over 17 WPC. Since you aren't doing much more than 1 WPC at that setting, I don't understand the current draw. Can you measure again to double check?
Thanks Pano. Yes each channel. Though I only measured on one channel. As I have separate Transformer and powersupply board for each channel. I will measure again. Also wanted to know...
Is the method of measuring current draw from Secondary Center tap correct ? Pic. attached in previous post.
On loud passages why did series test bulb glow bright ? Does that mean more current is flowing across primary and (Will not be doing/listening at that level ever) if pushed very very hard the primary will short ? just curious.
2.8 V I measured is at unimaginable volume. I got 1V at normal listening and around 1.5V at high volume listening.
regards
Is the method of measuring current draw from Secondary Center tap correct ? Pic. attached in previous post.
On loud passages why did series test bulb glow bright ? Does that mean more current is flowing across primary and (Will not be doing/listening at that level ever) if pushed very very hard the primary will short ? just curious.
2.8 V I measured is at unimaginable volume. I got 1V at normal listening and around 1.5V at high volume listening.
regards
Can it be like this. The secondary is putting too much stress on primary. The reason I ask is I am curious and will help me understand. Earlier I smoked a very old power transformer (50 yrs) of tube amp which was in intial stage.
Can I make RH84 from these parts ?
Can I make RH84 from these parts ?
I think it would be normal for a 60 or 100 watt bulb to flicker fairly brightly as the volume is turned up. I've certainly noticed that testing amplifiers.
The bulbs resistance increases in a non linear way as current increases, that causes the rails to drop quickly, then when the peak in the music passes the reservoir caps draw lots of current charging back up. It all averages out and you see it as the bulb lighting at some 'average' kind of brightness level.
Your measured 4.4 amps sounds a lot but it is also probably very peaky and highly non sinusoidal and so the reading on a normal DVM will not be accurate.
The bulbs resistance increases in a non linear way as current increases, that causes the rails to drop quickly, then when the peak in the music passes the reservoir caps draw lots of current charging back up. It all averages out and you see it as the bulb lighting at some 'average' kind of brightness level.
Your measured 4.4 amps sounds a lot but it is also probably very peaky and highly non sinusoidal and so the reading on a normal DVM will not be accurate.
I again checked the current drawn at centertap of Transformer Secondary. However Sony Boombox speakers were taken away by my friend so I used different speakers. To keep consistancy I used test tones to get desired voltages at speaker terminal so speakers does not matter. Also when nothing was played my multimeter was showing inconsistent current draw so I would treat these measurements as little unreliable. But to atleast have some average results I checked 3 to 4 times. Multimeter dial was set at 20A the probes at common and mA setting.
Test signal played at...
1V = 0.40 A
1.5V = 0.50 A
2V = 1.50 A
2.5V = 2.10 A
3V = 2.30 A
then I played Direstraits track at same volume setting of (3V test tones). With music playing at loudest. The currnt draw hovered around 2.2 A
Should I presume this as normal. This will help me decide to change rectifier diodes which are currently 6A4. and will also get peace of mind that transformer are suffecient. In broad sense how much average current is drawn from transformer ?
Thanks very much.
Test signal played at...
1V = 0.40 A
1.5V = 0.50 A
2V = 1.50 A
2.5V = 2.10 A
3V = 2.30 A
then I played Direstraits track at same volume setting of (3V test tones). With music playing at loudest. The currnt draw hovered around 2.2 A
Should I presume this as normal. This will help me decide to change rectifier diodes which are currently 6A4. and will also get peace of mind that transformer are suffecient. In broad sense how much average current is drawn from transformer ?
Thanks very much.
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And thank you for doing the measurements again. If measuring the current at the center tap is an accurate way to do it, then you amp must have a very high idle current. But maybe the center tap is not the place to measure - I don't know.
Is it possible to measure at the same speaker voltages but in the positive and/or negative leg only? I've done that with preamps, but maybe not power amps.
Is it possible to measure at the same speaker voltages but in the positive and/or negative leg only? I've done that with preamps, but maybe not power amps.