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Old 21st August 2010, 11:49 PM   #381
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Originally Posted by ostripper View Post
It has shown me why the DX/aksa55 sounds as it does and how all the others stack up.
IMHO, there is a very big difference between a DX amp and an AKSA55. Even though they are similar topology, component choice and attention to detail make a huge (hugh) difference.
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Old 22nd August 2010, 12:15 AM   #382
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Originally Posted by ostripper View Post
OK , I split the grounds between the 2 banks on (attachment 1). "A" goes to the trafo CT and then to the chassis ground ? B is then separate and takes all the connections from both "G1 and G2" . Do A and B then connect separately to the chassis ? Also, is this change because of the CLC ? On the Quasi NMOS PS all amp grounds , the trafo CT , and all capacitor grounds terminate at a central star on the PS PCB.
OS


Also , would the main audio star ground be on the chassis ?
Hi ostripper,

Even though I haven't done this myself, I'd be tempted to put your on-board star earth on the output side. Allow for a connection between A and B either via a link or use quick connectors so you can experiment. I'd also allow for an off-board star earth. In short, allow it to be configurable. While you are at it, move the LEDs to the diode side and allow for a cap between AC1 and AC2. When having a takeoff point between 2 caps make sure it is from the middle of the caps.

I plan to do something very similar to prove to myself that all this actually makes a difference. I'm planning for a resistor after the diodes, so RCLC. I have a feeling it won't make much difference.

regards
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Old 22nd August 2010, 01:19 AM   #383
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Originally Posted by Greg Erskine View Post
Hi ostripper,

Even though I haven't done this myself, I'd be tempted to put your on-board star earth on the output side. Allow for a connection between A and B either via a link or use quick connectors so you can experiment. I'd also allow for an off-board star earth. In short, allow it to be configurable. While you are at it, move the LEDs to the diode side and allow for a cap between AC1 and AC2. When having a takeoff point between 2 caps make sure it is from the middle of the caps.

I plan to do something very similar to prove to myself that all this actually makes a difference. I'm planning for a resistor after the diodes, so RCLC. I have a feeling it won't make much difference.

regards
Here is what national semi says about it : http://www.national.com/an/AN/AN-1849.pdf
(also attachment below)

They seem to do it like the quasi with signal , load (speaker) and amp grounds going right to a main PCB star. the only connection to the chassis is Rg , a little 100R component. CT goes right to the capacitor bank. I think I will leave all options open and allow 2 extra fastons between A and B.

This is the PS that national uses to make for the best reference of it's LME line , so I can assume the research is already done.
OS
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Old 22nd August 2010, 03:08 PM   #384
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Originally Posted by homemodder View Post


Thanks, very interesting. Seems that cap works as well as a darlington.
Could you post the sim file please, going to keep it for reference, who came up with the cap idea, it seems good. I will try it in a couple of minutes on one of my 1200w x 2 class G amp which I had factory built and was delivered this afternoon and see if it works good. As long as it doesnt oscillate it should be ok. They will be doing duty tonight in a nightclub replacing two previous versions of amps I hand built 3 years ago so hopefully all goes well.
Here is the .asc file. I wonder if there would be a benefit from using 5.5V "supercaps" for the mod? Could be interesting... I replaced the BD1xx with the japanese device Bigun used on his schematic.

I found the cap trick independently, first posting it in the HAKSA headphone amp development thread. I don't know who all else knows about it, OS posted the same thing with a 100nF cap in post #314. It's a simple mod though, I don't see any use in taking credit.

- keantoken
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Old 22nd August 2010, 03:14 PM   #385
AndrewT is offline AndrewT  Scotland
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Originally Posted by ostripper View Post
Also , would the main audio star ground be on the chassis ?
if you have one cap then each terminal (+ & -) is both input and output.
CT to -, - to zero Volts.
Rectifier to + and + to +ve supply.

When you parallel a pair of capacitors to do the same job you could still use the input pins as the output pins, but from well arranged diagrams I have seen it can be done better.

CT to -, - to wire, wire to 2nd-, 2nd- to Zero volts
and similarly
Rectifier to +, + to wire, wire to 2nd+, 2nd+ to +ve supply.
This uses the parasitic capacitance and inductance of the wire links between the two caps as a zero cost, zero space, addition to the filtering ability of the parallel caps.

Looking at rCRC and rCLC, the parasitics of the wires can be used between all the main components.

In at one end through the parallel caps, to the R or L, in at one end of the next bank, through this 2nd bank of parallel caps to the output at the far end.
Same with the Zero Volts. EXCEPT. The Zero Volts output from the first bank has very high ripple. A short wire to a star ground located at the output of the final bank achieves the same separation effect (similar to a Power Amp and it's PSU) of big charging spikes from the low level ripples at the ground of the next stage.
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Last edited by AndrewT; 22nd August 2010 at 03:17 PM.
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Old 23rd August 2010, 04:28 AM   #386
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Originally Posted by AndrewT View Post
if you have one cap then each terminal (+ & -) is both input and output.
CT to -, - to zero Volts.
Rectifier to + and + to +ve supply.

When you parallel a pair of capacitors to do the same job you could still use the input pins as the output pins, but from well arranged diagrams I have seen it can be done better.

CT to -, - to wire, wire to 2nd-, 2nd- to Zero volts
and similarly
Rectifier to +, + to wire, wire to 2nd+, 2nd+ to +ve supply.
This uses the parasitic capacitance and inductance of the wire links between the two caps as a zero cost, zero space, addition to the filtering ability of the parallel caps.

Looking at rCRC and rCLC, the parasitics of the wires can be used between all the main components.

In at one end through the parallel caps, to the R or L, in at one end of the next bank, through this 2nd bank of parallel caps to the output at the far end.
Same with the Zero Volts. EXCEPT. The Zero Volts output from the first bank has very high ripple. A short wire to a star ground located at the output of the final bank achieves the same separation effect (similar to a Power Amp and it's PSU) of big charging spikes from the low level ripples at the ground of the next stage.
Taking that advice , which "jives" with chapter 14 (D.self audio amp handbook) , I redesigned the ps100 (1st below). Knowing that the "dirtiest"
pulses are where the 1st set of reservoir caps meet the bridge rectifier , G1 from the amp boards (output transistor decoupling) is the only connect here.
G2 , which is the cap multipliers and voltage/signal board are tee'ed off the 2'nd half of the main star which is split by a wire jumper as suggested by Andrew T.

This arrangement also coincides with the national semi app note:

http://www.national.com/an/AN/AN-1849.pdf

Used the general layout rules of the app note.

It is even better with the split star , leds (so you don't die) , CLC and more robust construction. For a maximum rating , this board will do ..

Capacitor specs
100k@100v (35mm X60mm)
120k@80v
144k@63v

Amperage/wattage : with 50A bridge can handle 1 800w amp / 4R
or 2 250 -300W units. Below - are your other choices .
JUNK!!
Click the image to open in full size.
Or this , adequate for diy but crude.

Click the image to open in full size.

Hopefully this will be the only board you will need , it will be done tonight "PS100_complete.zip"

On another note , I will add the ability to use a second regulated power supply to both powerboards for running the voltage boards. I have a 35-0-35VAC toriod but need to figure how to implement a voltage doubler to get 70v rails ... any circuits or ideas??


OS
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Old 23rd August 2010, 05:16 AM   #387
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Originally Posted by Greg Erskine View Post
Hi ostripper,

Even though I haven't done this myself, I'd be tempted to put your on-board star earth on the output side. Allow for a connection between A and B either via a link or use quick connectors so you can experiment. I'd also allow for an off-board star earth. In short, allow it to be configurable. While you are at it, move the LEDs to the diode side and allow for a cap between AC1 and AC2. When having a takeoff point between 2 caps make sure it is from the middle of the caps.

I plan to do something very similar to prove to myself that all this actually makes a difference. I'm planning for a resistor after the diodes, so RCLC. I have a feeling it won't make much difference.

regards
As you see , your suggestions as well as the others are implemented. A real "mongrel" power supply.
OS
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Old 23rd August 2010, 06:03 AM   #388
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Originally Posted by ostripper View Post
As you see , your suggestions as well as the others are implemented. A real "mongrel" power supply.
OS
I noticed
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Old 25th August 2010, 08:38 AM   #389
csy is offline csy
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Hi OS

It looks like you've completed the revised PB60LPV1.1. This new form-factor and layout is much improved!

Taking a closer look, the fuse length of 25mm seems unusual. 5x20mm or 6x32mm (3AG) is more common.

Also, the overlay drawing implies the output inductor/resistor assembly is being done differently?
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Old 25th August 2010, 11:47 AM   #390
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Originally Posted by csy View Post
Hi OS

It looks like you've completed the revised PB60LPV1.1. This new form-factor and layout is much improved!

Taking a closer look, the fuse length of 25mm seems unusual. 5x20mm or 6x32mm (3AG) is more common.

Also, the overlay drawing implies the output inductor/resistor assembly is being done differently?
All for the people .. cheap power to the people!! Thanks for the "closer look",CSY. I added 1 -40 pixel hole to use either the 20mm or 25mm spacings, the extra trace space is there. They do make 1 " (25mm) fuses. 20 and 25mm are most common at Mouser. I use the datasheets (below-1st attachment)
to determine lead spacing and even add holes for the most common TWO components that mouser stocks in great numbers.

00300210N Littelfuse Fuseholders, Clips, & Hardware
These boards are made for what is out there..man.


I also reworked my "BABY" , the PB250 (2nd attachment). Shorter traces , ability to use second PS for voltage board/cap mult. (Vee2/Vcc2 connections).

To keep mind occupied , I make the LEECH amp (EX - 3rd attachment). Professor leach did do his homework , BUT with the modern parts and NO possibly unstable triple to deal with... I can do better. A real simple amp but needs closer match of input trannies as determined by this topology, you would just have to buy 20 each ksa992/ksc1845 and match 2 pairs for each amp.
OS
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File Type: gif fuseholder.gif (8.7 KB, 339 views)
File Type: gif BIG AMP.gif (39.7 KB, 159 views)
File Type: gif LEECH.gif (28.4 KB, 208 views)
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