In Renardson amp the zener's are included after the 300 ohm resistors while in other schematics they are before the resistors, or are missing.
Is it ok to move these zeners before the 300 ohm resistors. This way I could easily add another pair of transistors and 300 ohm resistors.
Thanks Alexandru
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I am trying to find a place where to buy a toroidal transformer 120V primar with 2 X 30V sec. www.qkits.com has them but the shiping costs $118 
Who knows another place?
Thanks Alexandru
Who knows another place?
Thanks Alexandru
tryalx said:I am trying to find a place where to buy a toroidal transformer 120V primar with 2 X 30V sec. www.qkits.com has them but the shiping costs $118
Who knows another place?
Thanks Alexandru
Try :
http://export.farnell.com/jsp/home/...sp/home/exportHome.jsp_A&_DAV=en_EX_DIRECTEXP
PSU power ratings
What power supply do I need?
Considering that the the amp provides at ful power a peak voltage of 30V on 4 ohm, this means 7.5 amps peak current. The average current should be 7.5 divided by the square root of 2 = 5.3 amps. Is this correct?
Considering that the rail to rail voltage is 85V than the average power consumed is 85 * 5.3 = 400.5. Does this mean that I would need a power supply that has at least 400 watt of sustained power for one mono amplifier? Is my computation correct?
I am trying to order a 30 x 30V or 33 x 33V toroidal transformer and I would appreciate your input.
Thanks, Alexandru
What power supply do I need?
Considering that the the amp provides at ful power a peak voltage of 30V on 4 ohm, this means 7.5 amps peak current. The average current should be 7.5 divided by the square root of 2 = 5.3 amps. Is this correct?
Considering that the rail to rail voltage is 85V than the average power consumed is 85 * 5.3 = 400.5. Does this mean that I would need a power supply that has at least 400 watt of sustained power for one mono amplifier? Is my computation correct?
I am trying to order a 30 x 30V or 33 x 33V toroidal transformer and I would appreciate your input.
Thanks, Alexandru
Re: PSU power ratings
You have to be careful with supply lines on amps.
While its easy to think 45 volts is OK for an amp it doesnt take into consideration transients in the music. Music has a huge dynmaic range.
I was shocked just how quickly the transients were clipped on my amp. So in the my next design I went for a 55 volt power line.
This also fits in well with 63 volt electrolytics which are in abundance.
I have even seen on this forum people using upto 130 volt power lines !!!!!
tryalx said:
You have to be careful with supply lines on amps.
While its easy to think 45 volts is OK for an amp it doesnt take into consideration transients in the music. Music has a huge dynmaic range.
I was shocked just how quickly the transients were clipped on my amp. So in the my next design I went for a 55 volt power line.
This also fits in well with 63 volt electrolytics which are in abundance.
I have even seen on this forum people using upto 130 volt power lines !!!!!
tryalx said:
I have read from other sources that you need work out what power goes into the speaker, then double it for power lost in the output transistors then add another 50% so the transformer isnt cooking on full load over long periods.
So for a 1000VA transformer you should get out about 330WRMS
That's a more straightforward way to figure out the transformer's power.
I won't be listening in my room at very high power levels, but as you mentioned the dynamics may jump high at moments. It looks like I may need a 500VA transformer to occasionally allow a max of 200W RMS burst of power into 4 ohm (also taking into account an 85% transformer efficiency).
Thanks, Alexandru
Hello Alexandru,
Have a look here www.signaltransfer.freeuk.com/powerout.htm it's quite well written and easy to follow.
The gate protection diodes ( if the amp is for your own use and you are not going to be shorting the outputs etc) I personally would not fit them. It's different in a commercial product that has to be as abuse proof as possible. If you move the zeners, there would be problems, the other side of the resistors is at a lower impedance, so more, possibly destructive current could be drawn + if they were triggered into conduction and the "characteristics" if you can call it that of the limiting action would be severely compromised.
Your transformer-- always use a bulb (mains filament say 60 to 100 watt) in series with the mains for testing, and not just for the tranny wiring but the whole amp as well.
Oh yes the primary windings, connect in parrallel. Which way round you ask --- use the bulb method, the correct way will draw no (minimal) current, the incorrect way and the bulb will be at high brightness. Now imagine trying that without the bulb
Have a look here www.signaltransfer.freeuk.com/powerout.htm it's quite well written and easy to follow.
The gate protection diodes ( if the amp is for your own use and you are not going to be shorting the outputs etc) I personally would not fit them. It's different in a commercial product that has to be as abuse proof as possible. If you move the zeners, there would be problems, the other side of the resistors is at a lower impedance, so more, possibly destructive current could be drawn + if they were triggered into conduction and the "characteristics" if you can call it that of the limiting action would be severely compromised.
Your transformer-- always use a bulb (mains filament say 60 to 100 watt) in series with the mains for testing, and not just for the tranny wiring but the whole amp as well.
Oh yes the primary windings, connect in parrallel. Which way round you ask --- use the bulb method, the correct way will draw no (minimal) current, the incorrect way and the bulb will be at high brightness. Now imagine trying that without the bulb
Forgot --- power output. Do you know the efficiency of your speakers in dB/WATT. The Forum Web page rearranges things, arghhh, first column is a 92 db speaker 2nd columnn an 82 db speaker.
Remember that doubling the power in the speaker increases the level by 3 db. So a 92 dB sensitivity speaker will give,
92 db/watt speaker.........and........an 82 db/watt speaker
92db for 1 watt rms..............82db for 1 watt rms
95db for 2 watt rms..............85db for 2 watt rms
98db for 4 watt rms..............88db for 4 watt rms
101db for 8 watt rms..............91db for 8 watt rms
104db for 16 watt rms..............94db for 16 watt rms
107db for 32 watt rms..............97db for 32 watt rms
110db for 64 watt rms..............100db for 64 watt rms
113db for 128 watt rms..............103db for 128 watt rms
The 82 db speaker is a real example -- Celestion SL6 -- used to use these a few years ago.
Speaker sensitivity is far more important than power. The first example is "louder" on 4 watts than the other is on 32 watts.
Even then it's not that straightfoward as a 3 db increase in level is barely perceptible to many. To get that extra 3 db which may not even be noticable adds hugely to the cost /size of everything.
I always ask this
DO YOU HAVE A 'SCOPE.
Remember that doubling the power in the speaker increases the level by 3 db. So a 92 dB sensitivity speaker will give,
92 db/watt speaker.........and........an 82 db/watt speaker
92db for 1 watt rms..............82db for 1 watt rms
95db for 2 watt rms..............85db for 2 watt rms
98db for 4 watt rms..............88db for 4 watt rms
101db for 8 watt rms..............91db for 8 watt rms
104db for 16 watt rms..............94db for 16 watt rms
107db for 32 watt rms..............97db for 32 watt rms
110db for 64 watt rms..............100db for 64 watt rms
113db for 128 watt rms..............103db for 128 watt rms
The 82 db speaker is a real example -- Celestion SL6 -- used to use these a few years ago.
Speaker sensitivity is far more important than power. The first example is "louder" on 4 watts than the other is on 32 watts.
Even then it's not that straightfoward as a 3 db increase in level is barely perceptible to many. To get that extra 3 db which may not even be noticable adds hugely to the cost /size of everything.
I always ask this
DO YOU HAVE A 'SCOPE.Hi Karl,
That's a very nice example, thank you, you saved me from searching through my electricity books from highschool .
Ok, so the gate protection diodes are not really critical in my case, that's great.
The trick with the bulb is also nice, I will remeber it!
I looked at different speakers, and probably I will settle on these one, once I get some more cash:
http://www.definitivetech.com/loudspeakers/mythos/mythos_st_supertower.html
These speakers got some awards and also have an efficiency of 93dB, which isn't bad. Your dB comparision table is very helpful.
I looked a while ago for a scope or eventually a pc scope such that I can apply some fourier to see the spectrum, and also to check the distortion level. Do you have any suggestions?
So will read the article and make up my mind about the PSU.
Thanks again,
Alexandru
That's a very nice example, thank you, you saved me from searching through my electricity books from highschool .
Ok, so the gate protection diodes are not really critical in my case, that's great.
The trick with the bulb is also nice, I will remeber it!
I looked at different speakers, and probably I will settle on these one, once I get some more cash:
http://www.definitivetech.com/loudspeakers/mythos/mythos_st_supertower.html
These speakers got some awards and also have an efficiency of 93dB, which isn't bad. Your dB comparision table is very helpful.
I looked a while ago for a scope or eventually a pc scope such that I can apply some fourier to see the spectrum, and also to check the distortion level. Do you have any suggestions?
So will read the article and make up my mind about the PSU.
Thanks again,
Alexandru
Hi Alex,
Nice speakers I think a MOSFET amp would be great with these.
Oscilloscopes, get real one you don't need anything too extreme for audio, even a 20Mhz dual trace is fine. Make sure it has a good bright trace preferably one where the CRT has a high final anode voltage -- 8 to 12 kv or so as these are much better than ones with around 1 to 2 kv final anode volts - much brighter and sharper.
Nice speakers
I think a MOSFET amp would be great with these. Oscilloscopes, get real one
you don't need anything too extreme for audio, even a 20Mhz dual trace is fine. Make sure it has a good bright trace preferably one where the CRT has a high final anode voltage -- 8 to 12 kv or so as these are much better than ones with around 1 to 2 kv final anode volts - much brighter and sharper.Hi Karl,
I have found some osciloscopes on sale here:
http://www.tequipment.net/OWONEDU5022.html
http://www.tequipment.net/OwonHDS1022M.html
They are not crt based, but they seem to hove some nice features. Do you have experience with any of these?
Thanks, Alexandru
I have found some osciloscopes on sale here:
http://www.tequipment.net/OWONEDU5022.html
http://www.tequipment.net/OwonHDS1022M.html
They are not crt based, but they seem to hove some nice features. Do you have experience with any of these?
Thanks, Alexandru
Hi Alex,
Afraid not, I use a 100Mhz 'scope. This is dual trace model together with a delayed sweep timebase, had it about 14 years now.
The thing with an analogue scope is it's all very real, there are no digital artefacts to confuse things, what you see on the screen is very real.
I am sure some of the modern LCD display types are very good, and they have features that would never be available on an analogue one.
Anyone else any views on this ?
Don't know what to advise really
Afraid not, I use a 100Mhz 'scope. This is dual trace model together with a delayed sweep timebase, had it about 14 years now.
The thing with an analogue scope is it's all very real, there are no digital artefacts to confuse things, what you see on the screen is very real.
I am sure some of the modern LCD display types are very good, and they have features that would never be available on an analogue one.
Anyone else any views on this ?
Don't know what to advise really
Hi Karl,
I have found an article about digital oscilloscopes here: http://www.picotech.com/applications/oscilloscope_tutorial.html
They suggest that the resolution of a digital oscilloscope should preferably be higher than 8bit.
The OWON ones are 8 bit so I will do some more search around.
Thanks, Alexandru
I have found an article about digital oscilloscopes here: http://www.picotech.com/applications/oscilloscope_tutorial.html
They suggest that the resolution of a digital oscilloscope should preferably be higher than 8bit.
The OWON ones are 8 bit so I will do some more search around.
Thanks, Alexandru
Looks interesting- will have a read later.
A lot depends on how much you want to pay. Audio is all low frequency stuff really, but my feeling is still to go with analogue. Unless your paying big bucks, digital will not offer the bandwidth I suspect. Viewing 20Khz is one thing, a stability problem in the Mhz range something else.
It may be worth you posting a new thread on 'scopes asking for recommendations. Ask yourself this though. "Will the model I am looking at display a 1 Mhz squarewave accurately" what about at 10 Mhz. That's a walk in the park for a good analogue 'scope.
Think of "Digital TV" & LCD monitors etc and the effects of pixalation. Then think of the resolution you can get with an old monochrome CRT, no contest !!
A lot depends on how much you want to pay. Audio is all low frequency stuff really, but my feeling is still to go with analogue. Unless your paying big bucks, digital will not offer the bandwidth I suspect. Viewing 20Khz is one thing, a stability problem in the Mhz range something else.
It may be worth you posting a new thread on 'scopes asking for recommendations. Ask yourself this though. "Will the model I am looking at display a 1 Mhz squarewave accurately" what about at 10 Mhz. That's a walk in the park for a good analogue 'scope.
Think of "Digital TV" & LCD monitors etc and the effects of pixalation. Then think of the resolution you can get with an old monochrome CRT, no contest !!
Your link to the tutorial. Figure 2b and 2c. I can relate to this, the colour burst signal of a composite video waveform. In the UK our (soon to be switched off --- yes yes yes ) analogue TV service uses the PAL system and the burst is at 4.433 Mhz. Is the NTSC 3.58 Mhz ? from memory. Anyway the representation shows "digital artefacts" even at this frequency, now imagine expanding the trace so one cycle fills the screen. It should be a nice clean sinewave, but you can see it "stepped" by the sampling of the 'scope.
) analogue TV service uses the PAL system and the burst is at 4.433 Mhz. Is the NTSC 3.58 Mhz ? from memory. Anyway the representation shows "digital artefacts" even at this frequency, now imagine expanding the trace so one cycle fills the screen. It should be a nice clean sinewave, but you can see it "stepped" by the sampling of the 'scope.- Status
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