Powering A Tough Speaker (Split from Simple Symmetrical Amplifier)

[Dr.H]

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

[AndrewT]

Originally Posted by Dr.H

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?

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.

[Lazy Cat]

Originally Posted by AndrewT

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.

[AndrewT]

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.

[Idefixes]

Originally Posted by Lazy Cat

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

[Dr.H]

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

[Nico Ras]

Dr H. probably 4 pairs devices at rail voltages of around 18V, I am guessing.

[Smiley 09]

Dr. H,

12 pairs MJ21195/MJ21196 (24 trannies) per mono-block and 4x 1500W toroids at 35V AC (two each per mono block) - cca + - 50V DC smoothed with 120K Cap. bank per rail do the job. Price for the project . . . ? it isn't friendly at all.

Cheers,

A.

[Nico Ras]

Hi Smiley, is it not a little over-kill he wants 50 watt not 1500 watt? Anyway we are designing a "normal" amp, this is as Andrew says off topic.

[Smiley 09]

Nico,

Originally Posted by Nico Ras

Hi Smiley, is it not a little over-kill he wants 50 watt not 1500 watt?

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.