Hi LazyCat,
I will be building one of these on a testbench soon. As you know I want to use it to power a tough speaker. A few questions:
1. Any guidelines on the VA size of the transformer?
2. How do I decide what rail voltages to use and is this determined by the number of output devices used?
3. Would the power suply benefit from a low noise regulator or is LM317/LM337 sufficient?
4. If I built just the front end to drive my 50R headphones, what supply voltages should I use?
Thanks!
Ryan
I will be building one of these on a testbench soon. As you know I want to use it to power a tough speaker. A few questions:
1. Any guidelines on the VA size of the transformer?
2. How do I decide what rail voltages to use and is this determined by the number of output devices used?
3. Would the power suply benefit from a low noise regulator or is LM317/LM337 sufficient?
4. If I built just the front end to drive my 50R headphones, what supply voltages should I use?
Thanks!
Ryan
these are all general questions that any ambitious amplifier builder will need answers for.
They have nothing to do with SSA specifically.
You have a lot of learning to catch up on.
read:
PASS
ESP
Decibel Dungeon
Leach
etc.
Thanks Andrew, you released me from being too occupied.
If someone can help dr.H by these questions I would be very grateful.
Dr H,
there are numerous postings on transformer VA advice.
There are numerous postings on determining transformer voltage and from there to supply rail voltage.
There is a current thread discussing device & Power output as well as numerous previous postings.
What is the 317 reg doing? Is it audio circuit influencing?
Read the numerous posts on headphone amplifiers and recommendations for supply voltages.
there are numerous postings on transformer VA advice.
There are numerous postings on determining transformer voltage and from there to supply rail voltage.
There is a current thread discussing device & Power output as well as numerous previous postings.
What is the 317 reg doing? Is it audio circuit influencing?
Read the numerous posts on headphone amplifiers and recommendations for supply voltages.
Thanks Andrew, you released me from being too occupied.
If someone can help Dr.H by these questions I would be very grateful.
As beginner, i ask me all the time Dr H question. The first question Dr h have to ask himself is what sort af speakers he want to drive (sensitivity, minimal impedance not nominal impedance, impedance profile, and the last phase shift). Then what listening habit he have (nearfield? sound level? may be musique nature?) and the last to my mind the size of the listening room. Without all this parameters he can't determined what amp ratings he needs. The simple look at all amp treads may help you ; for domestic use the builders goal is often 70-100w/8r and 140-200w/4R achieving with +/-50Vdc rails and between 300 à 500Va/chanels. With these ratings you are able to drive a large wide of speakers. But if these are less sensitiv or goes down less 4 ohms you have to increase rail voltage or output number. For output numbers it will depend on output nature (SOA curve).
That's for general guide line....from a beginner...
Marc
Thanks guys, I appreciate that the Q's are generic. Just thought that the answers would be reasonably straightforward.....
Let me try a specific question:
I have a 0.4 ohm speaker, I'd l;ike to run it at around 50W. How many output devices would be required in the SSA? And at what rail voltage? Any maths would be highly appreciated
Let me try a specific question:
I have a 0.4 ohm speaker, I'd l;ike to run it at around 50W. How many output devices would be required in the SSA? And at what rail voltage? Any maths would be highly appreciated
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Power Amplifier for Apogee Scitilla
Nico,
I do have listen the same type of speakers. From my long experience the only amp survive all the power requirement for all type of music listening and not to the levels that cops will inrush .... Is the one I mention, I do test the all renowned power amp. names and none survive more than 30 min. So I'm talking for Apogee Scintilla speakers only to be driven the way that listener can't fell the music power compression due to all kind of power looses in the power amplifier. This is so specific speaker with almost constant 0,3 R impedance within all the F. response and it is surely very significant a power reserve and drive ability of the amp connected to Scintillas.
For all other type of speakers there is not needed such an over dimensioned power - amplifier.
Cheers,
A.
Nico,
I think Mr. Dr. H. is listening at home Apogee Scintilla all ribbon 3 way speakers.
I do have listen the same type of speakers. From my long experience the only amp survive all the power requirement for all type of music listening and not to the levels that cops will inrush .... Is the one I mention, I do test the all renowned power amp. names and none survive more than 30 min. So I'm talking for Apogee Scintilla speakers only to be driven the way that listener can't fell the music power compression due to all kind of power looses in the power amplifier. This is so specific speaker with almost constant 0,3 R impedance within all the F. response and it is surely very significant a power reserve and drive ability of the amp connected to Scintillas.
For all other type of speakers there is not needed such an over dimensioned power - amplifier.
Cheers,
A.
Moved these posts to a thread of their own. Nico let me know if you want me to remove your OT comment in the above post.
Personal Tastes,
Nico,
It's not an offer here for the same amp I use at all, its just what happed to me, that after so many try-outs i made in the past 15.yrs., I must agree with that guy, who made this amp I currently use, that he exactly knows what will work in just any listening situation. I found Myself listening music mostly with low listening levels, but when it come a need for a real life-like feel of live performance of a full symphonic orchestra + choir at eg. Mahler 8. Symph. than 50 watts just can't do.
It would be a really nice experience if one would be at least once able to really feel what a radiating area, comparable to eight 12 inch woofers per speaker, can actually do in a reasonable size listening room, than he will maybe agree with me for the need for much more Watts....
I speak for this particularly speaker, and in a conjunction with dedicated custom made low-loss direct ribbon drive crossover network, the sound experience is remarkable.
With small amps, small speakers & small listening rooms nice sound can be achieved.
Bigger speakers, amps and rooms, it's another story.
Cheers,
A.
Nico,
It's not an offer here for the same amp I use at all, its just what happed to me, that after so many try-outs i made in the past 15.yrs., I must agree with that guy, who made this amp I currently use, that he exactly knows what will work in just any listening situation. I found Myself listening music mostly with low listening levels, but when it come a need for a real life-like feel of live performance of a full symphonic orchestra + choir at eg. Mahler 8. Symph. than 50 watts just can't do.
It would be a really nice experience if one would be at least once able to really feel what a radiating area, comparable to eight 12 inch woofers per speaker, can actually do in a reasonable size listening room, than he will maybe agree with me for the need for much more Watts....
I speak for this particularly speaker, and in a conjunction with dedicated custom made low-loss direct ribbon drive crossover network, the sound experience is remarkable.
With small amps, small speakers & small listening rooms nice sound can be achieved.
Bigger speakers, amps and rooms, it's another story.
Cheers,
A.
Thanks guys.
Smiley 09, what are you using now to drive your Scinctilla's? I have two KRELL KMA160's which I have modified (CCS for Zener, some new smoothing caps). I'd like to try other mods, but LazyCats design is interesting, so keen to build that too.
As you say though, the cost of buidling something to drive the Scinnies would not be cheap.
Smiley 09, what are you using now to drive your Scinctilla's? I have two KRELL KMA160's which I have modified (CCS for Zener, some new smoothing caps). I'd like to try other mods, but LazyCats design is interesting, so keen to build that too.
As you say though, the cost of buidling something to drive the Scinnies would not be cheap.
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Dr H,
If your need is for 50watt, the rail voltage is around 15VDC. The current would be around 12 amps and if using 2SK1058/2SJ162, 6 pairs of devices per channel would probably be adequite. Using the rule of thumb of 1000uF minimum/amp current, then 12 000uF per rail per amplifier would be a good starting point and a 150VA transformer per monobloc should be more than enough.
Smiley may have a different approach.
Kind regards
Nico
If your need is for 50watt, the rail voltage is around 15VDC. The current would be around 12 amps and if using 2SK1058/2SJ162, 6 pairs of devices per channel would probably be adequite. Using the rule of thumb of 1000uF minimum/amp current, then 12 000uF per rail per amplifier would be a good starting point and a 150VA transformer per monobloc should be more than enough.
Smiley may have a different approach.
Kind regards
Nico
Something I found from AndrewT in a different thread:
The actual numbers are irrelevant, ,more the relationships that are of interest.
your 50Vac will give 70.7Vdc as you said.
Add on the transformer regulation of 4% to 6% giving 73.5Vdc to 75Vdc. subtract diode drop at idle current say about 1V. final voltage at rated mains input voltage 72.5Vdc to 74Vdc.
If you now add in the mains variation from +6% to + 10% you will be way over 80Vdc. You decide if you want to take that risk. I would recommend 100V for your 50Vac transformer. for a 55Vac transformer you definately need 100V caps.
Regarding VA rating I would recommend 1.5 times the maximum output. So you need 600VA for 400W. This will have good bass if the caps are about 2mF to 3mF per amp of peak output current.
Your 4ohm speaker will have a minimum Z of about 3ohms. the Vpk will be about 60Vpk leading to Ipk=20A. you then need about 40mF to 60mF on each rail. You could go higher on VA rating and this would reduce your cap size slightly (30mF to 40mF). Alternatively, as suggested by others, go down on VA rating and increase the cap size to compensate. Half the VA would probably benefit from doubling the caps to 80mF to 120mF on 300VA transformer. This will still give good bass. The continuous output power will be slighly down maybe 300W but it will play music like a 400W amp.
The actual numbers are irrelevant, ,more the relationships that are of interest.
your 50Vac will give 70.7Vdc as you said.
Add on the transformer regulation of 4% to 6% giving 73.5Vdc to 75Vdc. subtract diode drop at idle current say about 1V. final voltage at rated mains input voltage 72.5Vdc to 74Vdc.
If you now add in the mains variation from +6% to + 10% you will be way over 80Vdc. You decide if you want to take that risk. I would recommend 100V for your 50Vac transformer. for a 55Vac transformer you definately need 100V caps.
Regarding VA rating I would recommend 1.5 times the maximum output. So you need 600VA for 400W. This will have good bass if the caps are about 2mF to 3mF per amp of peak output current.
Your 4ohm speaker will have a minimum Z of about 3ohms. the Vpk will be about 60Vpk leading to Ipk=20A. you then need about 40mF to 60mF on each rail. You could go higher on VA rating and this would reduce your cap size slightly (30mF to 40mF). Alternatively, as suggested by others, go down on VA rating and increase the cap size to compensate. Half the VA would probably benefit from doubling the caps to 80mF to 120mF on 300VA transformer. This will still give good bass. The continuous output power will be slighly down maybe 300W but it will play music like a 400W amp.
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