Re: specs, measurements
Stuart,
Are you saying that at saturation, the coils are still inductive to a limit and then resistive after that or are you saying that at saturation they suddently convert to 0% inductive and 100% resistive?
I would have thought they remain inductive but the inductance does not increase anymore with the increase in current (at saturation) but proportionally decreases after saturation.
thanks!
K-
Stuart Easson said:
Stuart,
Are you saying that at saturation, the coils are still inductive to a limit and then resistive after that or are you saying that at saturation they suddently convert to 0% inductive and 100% resistive?
I would have thought they remain inductive but the inductance does not increase anymore with the increase in current (at saturation) but proportionally decreases after saturation.
thanks!
K-
weelll...once apon a time, long, long ago...
there was an inductor...
but seriously, discard this, if you know this stuff...
Discussion: At the point where the core is saturated, because there is no increase in the magnetic field, additional current flowing through the device cannot induce the normal back emf that should accompany it. So in essence the thing is only a resistor. I doubt in reality that the cutover is as sharp as this suggests. As the current begins to decrease, the magnetic field will not diminish until the current has decreased below the point of saturation and therefore no forward emf will develop...
Theory: The inductance of a coil doesnt change as the current through the device changes, it is a measure of how much voltage is generated as a result of a current change. Basically it resists dynamic changes to the flow of current. If you try and make more current flow it will generate a back emf (electro motive force), ie a voltage that opposes the one trying to force the current. If the current decreases, as the magnetic field collapses it will generate a forward emf to try and force the current to maintain it's present level. The reservoir of energy in an inductor is the magnetic field, in order to charge the field, you have to 'force' feed more current into the thing by overcoming the back emf it generates, at the point where you stop increasing the current, the magnetic field will stabilise, and be available to generate a forward emf if the current tries to diminish. The maximum amount of energy you can store in an inductor is limited by the 'size' of the magnetic field you can generate, the core saturating stops the field increasing any more, so at that point it is full. Unlike a cap, an inductor being 'full' generally doesn't involve explosions.
Consequences: When you discharge a capacitor you can get huge currents if you do it quickly, with an inductor you get similar discharge characteristics, but they apply to voltage not current. If you dicharge it quickly you will get huge voltages, really, really huge voltages. This is the reason for diodes placed across relay coils and the like,without them discharging the stored energy, the emf will anihilate other components, especially semiconductors.
...and with the evil prince eviscerated, his innards picked apon by passing crows, they all lived happily ever after.
The end
Stuart
there was an inductor...
but seriously, discard this, if you know this stuff...
Discussion: At the point where the core is saturated, because there is no increase in the magnetic field, additional current flowing through the device cannot induce the normal back emf that should accompany it. So in essence the thing is only a resistor. I doubt in reality that the cutover is as sharp as this suggests. As the current begins to decrease, the magnetic field will not diminish until the current has decreased below the point of saturation and therefore no forward emf will develop...
Theory: The inductance of a coil doesnt change as the current through the device changes, it is a measure of how much voltage is generated as a result of a current change. Basically it resists dynamic changes to the flow of current. If you try and make more current flow it will generate a back emf (electro motive force), ie a voltage that opposes the one trying to force the current. If the current decreases, as the magnetic field collapses it will generate a forward emf to try and force the current to maintain it's present level. The reservoir of energy in an inductor is the magnetic field, in order to charge the field, you have to 'force' feed more current into the thing by overcoming the back emf it generates, at the point where you stop increasing the current, the magnetic field will stabilise, and be available to generate a forward emf if the current tries to diminish. The maximum amount of energy you can store in an inductor is limited by the 'size' of the magnetic field you can generate, the core saturating stops the field increasing any more, so at that point it is full. Unlike a cap, an inductor being 'full' generally doesn't involve explosions.
Consequences: When you discharge a capacitor you can get huge currents if you do it quickly, with an inductor you get similar discharge characteristics, but they apply to voltage not current. If you dicharge it quickly you will get huge voltages, really, really huge voltages. This is the reason for diodes placed across relay coils and the like,without them discharging the stored energy, the emf will anihilate other components, especially semiconductors.
...and with the evil prince eviscerated, his innards picked apon by passing crows, they all lived happily ever after.
The end
Stuart
Hi All-
Ok so my neighbor just found some 800va toroids with 25 volt secondaries. That is 16 amps per secondary.
We are planning on doing CLC pwr supplies with three(3) channels.
I figure 1 amp bias x 9 transistors per rail = 9 amps so a 16 amp per rail x-former will give > 75% margin on power requirements.
Is there a reason to go with a larger transformer *except* for welding purposes?
If not, he will pick up these two Toroids for us and I shall keep my puny little EI cores for another project.. Maybe an XGC?
Anyway, is 800va adequate for 2.5 channels of klone? The "middle channel will be lower bias and usually NOT on for stereo listening..
Ok so my neighbor just found some 800va toroids with 25 volt secondaries. That is 16 amps per secondary.
We are planning on doing CLC pwr supplies with three(3) channels.
I figure 1 amp bias x 9 transistors per rail = 9 amps so a 16 amp per rail x-former will give > 75% margin on power requirements.
Is there a reason to go with a larger transformer *except* for welding purposes?
If not, he will pick up these two Toroids for us and I shall keep my puny little EI cores for another project.. Maybe an XGC?
Anyway, is 800va adequate for 2.5 channels of klone? The "middle channel will be lower bias and usually NOT on for stereo listening..
he 'found' them...
...Obviously I'm not looking hard enough...were they under something?
Each channel will pull ~2amps, and from 25-0-25 will have 37v rails, so you are using ~150watts for normal class A operation for one channel, 3 requires 450 watts. So 800va will easily power 3 channels...
...Obviously I'm not looking hard enough...were they under something?
Each channel will pull ~2amps, and from 25-0-25 will have 37v rails, so you are using ~150watts for normal class A operation for one channel, 3 requires 450 watts. So 800va will easily power 3 channels...
Re: he 'found' them...
Ha ha. You funny man...
No actually I have EI cores.. Neighbor has nothing. So I told him what to shop for.. I mentioned 750 va, he found "good prices" on an 800va...
But of course I don't know anything so HE was unsure whether 800va would be enough and requested a second opinion....
Stuart Easson said:
Ha ha. You funny man...
No actually I have EI cores.. Neighbor has nothing. So I told him what to shop for.. I mentioned 750 va, he found "good prices" on an 800va...
But of course I don't know anything so HE was unsure whether 800va would be enough and requested a second opinion....
800VA - PN Y236900
25-0-25
$69.93
1000VA - PN Y236950
25-0-25
$81.85
Plus shipping...
Ordered directly from them.
http://avellindberg.com/transformers/y23_range_specs.htm
25-0-25
$69.93
1000VA - PN Y236950
25-0-25
$81.85
Plus shipping...
Ordered directly from them.
http://avellindberg.com/transformers/y23_range_specs.htm
Hmmmm be creative.
Beg her to reconsider or sell on eBay......
Well anyway not sure if it would have made such a huge diff. But
I think I could have gotten them for $50 plus $8 for shipping to me... roughly. I am in Indiana so it might have been cheaper to ship to the rest of the mainland... oh well!
PS: Please don't ask me the supplier who did that for me or Melanie would have him for Dinner.
Beg her to reconsider or sell on eBay......
Well anyway not sure if it would have made such a huge diff. But
I think I could have gotten them for $50 plus $8 for shipping to me... roughly. I am in Indiana so it might have been cheaper to ship to the rest of the mainland... oh well!
PS: Please don't ask me the supplier who did that for me or Melanie would have him for Dinner.
Our latest news flash
When using TO-3's... be careful, the case is live, so never touch both sides at once!!! (it tickles a little)....
On that note, i'm wearing gloves this time just to make sure i don't do THAT again
Another note, i've got my heatsink built up with 5 pairs of outputs and my rail voltage was under 35vdc under moderate load... i don't think i have a 300va toroid anymore, sounds like it might be overrated a little (or a lot)
Aaron
When using TO-3's... be careful, the case is live, so never touch both sides at once!!! (it tickles a little)....
On that note, i'm wearing gloves this time just to make sure i don't do THAT again
Another note, i've got my heatsink built up with 5 pairs of outputs and my rail voltage was under 35vdc under moderate load... i don't think i have a 300va toroid anymore, sounds like it might be overrated a little (or a lot)
Aaron
Up and stable!
Ok,
I got mine up and running...
5 pairs of output transistors... TO-3 variety (as mentioned above!)
Now running 40vdc rails (loaded down a fair bit... i MAY be going beyond the toroids ability - how do i know when it's run out of steam????)
Few questions...
I had 41vdc rails with 150ma bias ("highest" out of the 10 chips... by about 10ma) heatsink was sitting at 58deg after 1 hour...
What sort of output would i have got from that (class A - i'm running into 4 ohms)??
Next: I'm now running 2 12cm fans @ 9v and they are going ok, reasonably quiet, silent about 1m away...
Now running 250ma bias (varies a little but no more than 10ma difference between all the outputs) with 40vdc rails - what class A would i expect @ 4 ohm? The heatsinks are sitting at 39deg also the outputs are also at 41deg approx (all the same)...
I will be running more bias than this, but if i go higher with the adjustment the rail voltage drops pretty fast, so i think i have hit the limit for my toroid...
How much heat should i be dissapating at the moment? I'm guessing (going on calcs) about 150w??? I'm using 0.68ohm emitter resistors... Are those calcs about right?
Last question - on my board the P channel pre-driver gets hot (about 51deg) and the n channel gets about 45deg - is there a reason for that? the drivers is hard to tell as they are on the same sink, but appear to have about 3deg difference... The outputs however have the same (exact) temp across every output...
Should i be worried?
Aaron
Ok,
I got mine up and running...
5 pairs of output transistors... TO-3 variety (as mentioned above!)
Now running 40vdc rails (loaded down a fair bit... i MAY be going beyond the toroids ability - how do i know when it's run out of steam????)
Few questions...
I had 41vdc rails with 150ma bias ("highest" out of the 10 chips... by about 10ma) heatsink was sitting at 58deg after 1 hour...
What sort of output would i have got from that (class A - i'm running into 4 ohms)??
Next: I'm now running 2 12cm fans @ 9v and they are going ok, reasonably quiet, silent about 1m away...
Now running 250ma bias (varies a little but no more than 10ma difference between all the outputs) with 40vdc rails - what class A would i expect @ 4 ohm? The heatsinks are sitting at 39deg also the outputs are also at 41deg approx (all the same)...
I will be running more bias than this, but if i go higher with the adjustment the rail voltage drops pretty fast, so i think i have hit the limit for my toroid...
How much heat should i be dissapating at the moment? I'm guessing (going on calcs) about 150w??? I'm using 0.68ohm emitter resistors... Are those calcs about right?
Last question - on my board the P channel pre-driver gets hot (about 51deg) and the n channel gets about 45deg - is there a reason for that? the drivers is hard to tell as they are on the same sink, but appear to have about 3deg difference... The outputs however have the same (exact) temp across every output...
Should i be worried?
Aaron
K-Amps, why not just post it here... after allthis is an information type of forum where one cannot post too much data.
I spent all of last night listening to my KSA-50's on my Dynaudios. It really makes them come alive! Its very reminiscent of my KSA-80B but with perhaps a tad smoother high end. Resolution of fine detail, soundstaging and depth have to be heard to be appreciated. The amp is VERY dynamic and capable. BUT...It does what all Krells do, it makes a bad sounding CD sound really bad and turns a good sounding one into pure magic...... my KSA-80 did this exact same thing.
Does it sound better than others.... No, The Krell has excellence that stands on its own merits, its just different like a different wine(to quote Nelson Pass)
.
NOTE: Those that have a tizzy high end response from their speakers may not like this amp!
I spent all of last night listening to my KSA-50's on my Dynaudios. It really makes them come alive! Its very reminiscent of my KSA-80B but with perhaps a tad smoother high end. Resolution of fine detail, soundstaging and depth have to be heard to be appreciated. The amp is VERY dynamic and capable. BUT...It does what all Krells do, it makes a bad sounding CD sound really bad and turns a good sounding one into pure magic...... my KSA-80 did this exact same thing.
Does it sound better than others.... No, The Krell has excellence that stands on its own merits, its just different like a different wine(to quote Nelson Pass)
.
NOTE: Those that have a tizzy high end response from their speakers may not like this amp!
Attachments
Mark, I just wanted to make sure I do not overload the thread with data irrelevant to others, if you think it will benefit people here it is:
Aaron's first scenario:
Class-A output Calculation: Krell KSA-50 Mk. II
Inputs
Number of output devices: 5 Pairs
Voltage rails (per rail): 41 volts
Emitter resistance (per device): 0.68 ohms
Bias voltage per Emmiter resistor: 100 mv
Idle bias per device 147.1 mA
Speaker ohms 8 ohms
Results
Idle bias per device: 0.147 Amps
Total Amplifier bias (per rail)** 0.74 Amps
Total Amplifier bias (both rails) 1.47 Amps
Total Dissipation (per channel) 60.3 Watts
Dissipation per device pair at idle 6.0 watts
Class-A output: Peak 17.3 Watts peak
Class-A output: RMS 8.7 Watts RMS
Efficiency 14.35 %
Aaron's second scenario:
Class-A output Calculation: Krell KSA-50 Mk. II
Inputs
Number of output devices: 5 Pairs
Voltage rails (per rail): 40 volts
Emitter resistance (per device): 0.68 ohms
Bias voltage per Emmiter resistor: 170 mv
Idle bias per device 250.0 mA
Speaker ohms 8 ohms
Results
Idle bias per device: 0.250 Amps
Total Amplifier bias (per rail)** 1.25 Amps
Total Amplifier bias (both rails) 2.50 Amps
Total Dissipation (per channel) 100.0 Watts
Dissipation per device pair at idle 10.0 watts
Class-A output: Peak 50.0 Watts peak
Class-A output: RMS 25.0 Watts RMS
Efficiency 25.00 %
4 ohm class A output is exactly half of 8 ohm. These calcs represent 8 ohms. Below are the same with 4 ohm loads:
Class-A output Calculation: Krell KSA-50 Mk. II
Inputs
Number of output devices: 5 Pairs
Voltage rails (per rail): 40 volts
Emitter resistance (per device): 0.68 ohms
Bias voltage per Emmiter resistor: 170 mv
Idle bias per device 250.0 mA
Speaker ohms 4 ohms
Results
Idle bias per device: 0.250 Amps
Total Amplifier bias (per rail)** 1.25 Amps
Total Amplifier bias (both rails) 2.50 Amps
Total Dissipation (per channel) 100.0 Watts
Dissipation per device pair at idle 10.0 watts
Class-A output: Peak 25.0 Watts peak
Class-A output: RMS 12.5 Watts RMS
Efficiency 12.50 %
For 4 ohm load and 150 watt class-A, Aaron needs to crank up the bias to 0.867 amps per device. At that level the amp will be dissipating over 300 watts at idle plus 150 watts at max power i.e. 450 watts total? As opposed to his current dissipation of 60-100 watts. Also the PSU will need to keep that rails at a minimum of +/-35vdc or above to get 150 watts class-A into 4 ohms.
Lastly assuming his rails will drop, I have used a figure of +/-36vdc for this calc: (adding a volt or so for losses etc).
Class-A output Calculation: Krell KSA-50 Mk. II 150watts into 4 ohms
Inputs
Number of output devices: 5 Pairs
Voltage rails (per rail): 36 volts
Emitter resistance (per device): 0.68 ohms
Bias voltage per Emmiter resistor: 589 mv
Idle bias per device 866.2 mA
Speaker ohms 4 ohms
Results
Idle bias per device: 0.866 Amps
Total Amplifier bias (per rail)** 4.33 Amps
Total Amplifier bias (both rails) 8.66 Amps
Total Dissipation (per channel) 311.8 Watts
Dissipation per device pair at idle 31.2 watts
Class-A output: Peak 300.1 Watts peak
Class-A output: RMS 150.1 Watts RMS
Efficiency 48.12 %
Assuming he can sink that much heat and keep the thing alive, he will have a KSA-75.
Aaron's first scenario:
Class-A output Calculation: Krell KSA-50 Mk. II
Inputs
Number of output devices: 5 Pairs
Voltage rails (per rail): 41 volts
Emitter resistance (per device): 0.68 ohms
Bias voltage per Emmiter resistor: 100 mv
Idle bias per device 147.1 mA
Speaker ohms 8 ohms
Results
Idle bias per device: 0.147 Amps
Total Amplifier bias (per rail)** 0.74 Amps
Total Amplifier bias (both rails) 1.47 Amps
Total Dissipation (per channel) 60.3 Watts
Dissipation per device pair at idle 6.0 watts
Class-A output: Peak 17.3 Watts peak
Class-A output: RMS 8.7 Watts RMS
Efficiency 14.35 %
Aaron's second scenario:
Class-A output Calculation: Krell KSA-50 Mk. II
Inputs
Number of output devices: 5 Pairs
Voltage rails (per rail): 40 volts
Emitter resistance (per device): 0.68 ohms
Bias voltage per Emmiter resistor: 170 mv
Idle bias per device 250.0 mA
Speaker ohms 8 ohms
Results
Idle bias per device: 0.250 Amps
Total Amplifier bias (per rail)** 1.25 Amps
Total Amplifier bias (both rails) 2.50 Amps
Total Dissipation (per channel) 100.0 Watts
Dissipation per device pair at idle 10.0 watts
Class-A output: Peak 50.0 Watts peak
Class-A output: RMS 25.0 Watts RMS
Efficiency 25.00 %
4 ohm class A output is exactly half of 8 ohm. These calcs represent 8 ohms. Below are the same with 4 ohm loads:
Class-A output Calculation: Krell KSA-50 Mk. II
Inputs
Number of output devices: 5 Pairs
Voltage rails (per rail): 40 volts
Emitter resistance (per device): 0.68 ohms
Bias voltage per Emmiter resistor: 170 mv
Idle bias per device 250.0 mA
Speaker ohms 4 ohms
Results
Idle bias per device: 0.250 Amps
Total Amplifier bias (per rail)** 1.25 Amps
Total Amplifier bias (both rails) 2.50 Amps
Total Dissipation (per channel) 100.0 Watts
Dissipation per device pair at idle 10.0 watts
Class-A output: Peak 25.0 Watts peak
Class-A output: RMS 12.5 Watts RMS
Efficiency 12.50 %
For 4 ohm load and 150 watt class-A, Aaron needs to crank up the bias to 0.867 amps per device. At that level the amp will be dissipating over 300 watts at idle plus 150 watts at max power i.e. 450 watts total? As opposed to his current dissipation of 60-100 watts. Also the PSU will need to keep that rails at a minimum of +/-35vdc or above to get 150 watts class-A into 4 ohms.
Lastly assuming his rails will drop, I have used a figure of +/-36vdc for this calc: (adding a volt or so for losses etc).
Class-A output Calculation: Krell KSA-50 Mk. II 150watts into 4 ohms
Inputs
Number of output devices: 5 Pairs
Voltage rails (per rail): 36 volts
Emitter resistance (per device): 0.68 ohms
Bias voltage per Emmiter resistor: 589 mv
Idle bias per device 866.2 mA
Speaker ohms 4 ohms
Results
Idle bias per device: 0.866 Amps
Total Amplifier bias (per rail)** 4.33 Amps
Total Amplifier bias (both rails) 8.66 Amps
Total Dissipation (per channel) 311.8 Watts
Dissipation per device pair at idle 31.2 watts
Class-A output: Peak 300.1 Watts peak
Class-A output: RMS 150.1 Watts RMS
Efficiency 48.12 %
Assuming he can sink that much heat and keep the thing alive, he will have a KSA-75.
