Movin' To Montana Soon (Frank Zappa)
Nick,
Mark is still in Montana, and unless the new movie theater installation is not complete, should be back in Salt Lake City/Bountiful this weekend. Yes, he has boards, but the second run of Al's boards are dwindling.
$1 million Ferrari destroyed in car accident in L.A. Did they pull out the stereo?
Nick,
Mark is still in Montana, and unless the new movie theater installation is not complete, should be back in Salt Lake City/Bountiful this weekend. Yes, he has boards, but the second run of Al's boards are dwindling.
$1 million Ferrari destroyed in car accident in L.A. Did they pull out the stereo?
lawbadman said:
Hi Lawrence,
If it's any help, I've built two KSA50's. The first one was using the Delta Audio boards. I used a single 30-0-30 500vA. Works perfectly. For the second one I used the Pinkmouse boards and I used two 25-0-25 400vA, mono-block style, and it sound the same to me. Perhaps they measure differently but I can't hear any difference between the two amps.
Blessings, Terry
LuckyLyndy said:
I believe in some parts in LA they pull out the driver, in other areas the stereo.
I just finished the second channel of the KSA, this one with the revised MPSA Vas, and compared both versions. I'll stick to the original design with double Toshiba Vas.
Thanks Ansrew
I want to bias to class A so I think is better to purchase a lower voltage transformer .
What do you think if I use more than 3pair mosfets for output .
Just to spread the mosfets better on the heatsink .
I sow at the Ebay a 2x31v 800VA transformer , please let me know what do you think about . I dont want to modifie the pc board , to replace the resistors ect. I just dont have the tools to do . Please let me know if I use these transformer , with 4 or 5 pair power mosfet it going to work to me ?
Thanks one more time
Regards
I want to bias to class A so I think is better to purchase a lower voltage transformer .
What do you think if I use more than 3pair mosfets for output .
Just to spread the mosfets better on the heatsink .
I sow at the Ebay a 2x31v 800VA transformer , please let me know what do you think about . I dont want to modifie the pc board , to replace the resistors ect. I just dont have the tools to do . Please let me know if I use these transformer , with 4 or 5 pair power mosfet it going to work to me ?
Thanks one more time
Regards
gaborbela said:
I'm no genius but the Krell Clone does not use MOSFETs, unless you change the design you should use bipolar output transistors.
Yes, if you use bipolars, 3 pairs per channel are fine, I have 4 pairs per channel on mine and did not change any circuit values to account for this.
And if you are going 100wpc, double the outputs and also double the drivers as what Krell did. i.e. they had a driver for each pair of outputs.
HI
I'm sorry it just a mistake the mosfet . I'm using MJL21194/93 power transistor .
The same time I work on a Aleph30 and that why I wrote mosfet .
Thanks for help.
Regards
I'm sorry it just a mistake the mosfet . I'm using MJL21194/93 power transistor .
The same time I work on a Aleph30 and that why I wrote mosfet .
Thanks for help.
Regards
K-amps said:
Do you think my drivers are warmer than normal since I have 4 pairs and did not double them? They dont get dangerously hot even at high volumes.
I wonder if I should go back in and double them? I'm not using a higher rail voltage so it did not occur to me.
drivers...
Hi,
The original Krell KSA100 only had a single pair of drivers despite the additional outputs, there isn't any problem as far as I can see. The drivers could be more stressed under very high current situations, but the additional outputs will actually make their life easier for all but the most demanding loads. Since each output is carrying less of the total load, in general it will have a higher intrinsic gain and the output stage as a whole will exhibit higher gain easing the load on the drivers. Doug Self documents this effect in his book if anyone wants more info...
HTH
Stuart
Hi,
The original Krell KSA100 only had a single pair of drivers despite the additional outputs, there isn't any problem as far as I can see. The drivers could be more stressed under very high current situations, but the additional outputs will actually make their life easier for all but the most demanding loads. Since each output is carrying less of the total load, in general it will have a higher intrinsic gain and the output stage as a whole will exhibit higher gain easing the load on the drivers. Doug Self documents this effect in his book if anyone wants more info...
HTH
Stuart
Correct and as Stuart says, there will be a reduction in distortion (under high current loading) in the "Pre"-drivers. i.e. This is an issue for the prior driver not the one being dobled or even the OP stage but the prior driver which gets loaded more once the gain of the driver begins to fail or droop under high current load.
i.e.A pre-driver driving 1 driver for a given current loading will be taxed less than the same pre-driver if it were driving 2 drivers ultimately driving the same output load. Seems a little contradictory as logically the opposite would be true because driving 2 devices to class-A would be more taxing, but in this case after a certain point, the dual driver topology will have advantages over the single driver.
Again it depends... for a KSA-50 I would not worry till 2 ohms. If you have less than 2 ohm load or want a KSA-100, then I would think about it.
Sorry I cannot predict specifically the conditions where one scenario would be advantageous over the other BUT I would reckon someone like AndrewT would be able to come up with the exact conditions and calculations where this transition would happen. he would probably factor in all currents involved in the OP/driver/pre-driver plus the hfe linearity of each device at each current loading plus the distortion arising out of such a droop... perhaps would need to rig it up as calcs alone may not shed all the light.
i.e.A pre-driver driving 1 driver for a given current loading will be taxed less than the same pre-driver if it were driving 2 drivers ultimately driving the same output load. Seems a little contradictory as logically the opposite would be true because driving 2 devices to class-A would be more taxing, but in this case after a certain point, the dual driver topology will have advantages over the single driver.
Again it depends... for a KSA-50 I would not worry till 2 ohms. If you have less than 2 ohm load or want a KSA-100, then I would think about it.
Sorry I cannot predict specifically the conditions where one scenario would be advantageous over the other BUT I would reckon someone like AndrewT would be able to come up with the exact conditions and calculations where this transition would happen. he would probably factor in all currents involved in the OP/driver/pre-driver plus the hfe linearity of each device at each current loading plus the distortion arising out of such a droop... perhaps would need to rig it up as calcs alone may not shed all the light.
Hi Kamps,
take out the reference to distortion, then, Yes it's already been investigated BEFORE I started purchasing the parts.
That Bensen spreadsheet is an absolute godsend. Although the number of mods I've added make it almost unrecognisable.
Just to confirm the previous posters' replies.
At the same loading, additional parallel output devices reduce the load on the driver and pre-driver.
Doubled drivers also reduce loading on the pre-driver.
Reduce the load impedance and all three output stages suffer more stress.
take out the reference to distortion, then, Yes it's already been investigated BEFORE I started purchasing the parts.
That Bensen spreadsheet is an absolute godsend. Although the number of mods I've added make it almost unrecognisable.
Just to confirm the previous posters' replies.
At the same loading, additional parallel output devices reduce the load on the driver and pre-driver.
Doubled drivers also reduce loading on the pre-driver.
Reduce the load impedance and all three output stages suffer more stress.
Re: Movin' To Montana Soon (Frank Zappa)
$1 million Ferrari destroyed in car accident in L.A. Did they pull out the stereo?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
mabe he can try this car next
http://www.forbes.com/2001/11/12/1112vow.html
but only with a Kraco 8-track
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
has anyone tried the ksa 50 and the 50s?
$1 million Ferrari destroyed in car accident in L.A. Did they pull out the stereo?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
mabe he can try this car next
http://www.forbes.com/2001/11/12/1112vow.html
but only with a Kraco 8-track
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
has anyone tried the ksa 50 and the 50s?
2 ohms?
OK, I admit that when I put 4 pairs of output devices I assumed that I would not have a problem with 2 or even 1 ohm loads. Is it going to work or not? I don't mind if its stressed into these loads because they will be infrequent. As I said about 1000 posts ago, I'm too afraid to actually connect these loads for power testing as I don't want to fry anything. But not afraid to crank my krell all night long baby!!
K-amps said:
OK, I admit that when I put 4 pairs of output devices I assumed that I would not have a problem with 2 or even 1 ohm loads. Is it going to work or not? I don't mind if its stressed into these loads because they will be infrequent. As I said about 1000 posts ago, I'm too afraid to actually connect these loads for power testing as I don't want to fry anything. But not afraid to crank my krell all night long baby!!
L,
I don't think you will fry the amp with 1 ohm on those low rails. And it will take special ears to feel the difference. You are ok... 🙂
I don't think you will fry the amp with 1 ohm on those low rails. And it will take special ears to feel the difference. You are ok... 🙂
Hi,
I would like to put some conditions on that "yes" into 1ohm.
My output stage (1500w of devices - 5pairs) can push a 2ohm load to 45 phase angle when Tc is at or below (<=)70degC.
In other words it will drive most low impedance speakers adequately in a domestic situation. Even pairs of 4ohm.
However this ability is much reduced into a 1ohm load when it can only manage 12degrees of phase angle indicating that it is struggling to drive any kind of speaker combination that is well below 2ohm.
A second problem at these very low value loads is the increasing heatsink temperature when driven beyond the ClassA bias level. As the output current approaches 2 times Iq then the total dissipation is still Pq. But as soon as you exceed 2Iq then the dissipation increases and sink temp rises. For domestic use these excursions are very short when driving 4 to 8ohm loads, but at 2ohm these excursions beyond 2Iq become longer and more frequent.
In the domestic situation and no one in their right mind would use these or real Krells for PA work or partying when drink gets the better of volume control finesse, these problems can be avoided by adding an over temperature switch if you foresee regular use into very low impedance loads. This same switch might also save most of the output stage if a fault (biasing problem) develops that causes overtemperature.
I would like to put some conditions on that "yes" into 1ohm.
My output stage (1500w of devices - 5pairs) can push a 2ohm load to 45 phase angle when Tc is at or below (<=)70degC.
In other words it will drive most low impedance speakers adequately in a domestic situation. Even pairs of 4ohm.
However this ability is much reduced into a 1ohm load when it can only manage 12degrees of phase angle indicating that it is struggling to drive any kind of speaker combination that is well below 2ohm.
A second problem at these very low value loads is the increasing heatsink temperature when driven beyond the ClassA bias level. As the output current approaches 2 times Iq then the total dissipation is still Pq. But as soon as you exceed 2Iq then the dissipation increases and sink temp rises. For domestic use these excursions are very short when driving 4 to 8ohm loads, but at 2ohm these excursions beyond 2Iq become longer and more frequent.
In the domestic situation and no one in their right mind would use these or real Krells for PA work or partying when drink gets the better of volume control finesse, these problems can be avoided by adding an over temperature switch if you foresee regular use into very low impedance loads. This same switch might also save most of the output stage if a fault (biasing problem) develops that causes overtemperature.
Pinky et all.
You guys know, I wanted to sell my 6 Jan boards, so I put them on ebay after no interest was shown on the thread.
All I wanted to do was recoup the cost... BUT, look what they sold for.... What do I do with the extra cash? I don't feel comfy keeping it...
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ssPageName=ADME:L:EOISSAA:US:11&item=5869452218
Donate to DIYaudio? 😀
You guys know, I wanted to sell my 6 Jan boards, so I put them on ebay after no interest was shown on the thread.
All I wanted to do was recoup the cost... BUT, look what they sold for.... What do I do with the extra cash? I don't feel comfy keeping it...
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ssPageName=ADME:L:EOISSAA:US:11&item=5869452218
Donate to DIYaudio? 😀
heat
Good idea. My fan controller has an alarm that will visually and audibly indicate if any of the 4 temperature sensors hits the programmable alarm temperature. I've set this for 65C and its never gone off.
In practice I have found that the sinks (well at least mine) don't vary their temperature by much, even at low/high volumes. I guess my speakers don't dip significantly below 4 ohms.
AndrewT said:
Good idea. My fan controller has an alarm that will visually and audibly indicate if any of the 4 temperature sensors hits the programmable alarm temperature. I've set this for 65C and its never gone off.
In practice I have found that the sinks (well at least mine) don't vary their temperature by much, even at low/high volumes. I guess my speakers don't dip significantly below 4 ohms.