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Old 7th October 2012, 04:25 AM   #461
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Quote:
Originally Posted by 6L6 View Post
The most important things to remember are -

1) Do the components fit the PCB mount holes, and also have no interference with each other?

2) Are the caps of big enough capacity and of a proper voltage rating?

3) Are the resistors of the proper value and wattage?

4) Does the component fit in the provided holes?

5) Are you planning on using a clip-on (or screw on) heatsink for the diodes, or mount them to the chassis? Do said heatsinks fit?
(Or will you just ignore the discrete diodes entirely and use a pair of bridges?)


There is a reason why fit is such a big deal - you will have a bazillion choices in manufacturer, value, voltage rating, etc... of the various components to use, and it will most likely work just fine. However, if something dosen't fit, it's a headache.

6L6, I have some experience in design, it's what I believe is my forté. Overkill in planning and design is something I love. Hopefully that will take care of #1, 4, 5. I have some preliminary research before getting to #2, 3. Which I'll be sure to post make sure I'm not wasting time and money. Thanks again!
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Old 7th October 2012, 04:27 AM   #462
6L6 is offline 6L6  United States
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Looks like you posted a couple of questions when I was typing.

TO-220 vs. TO-3P/TO-247 The latter is a bigger package. Possible a higher power rating of the discrete diode. Look at the datasheet (of the suggested parts) for the specifics.

The suggested diodes in the TO-220 package are about half the price of the others...

As for voltage of your transformer, the really important question is what version of the amp are you building? F5? Parallel F5? Cascoded F5? The first 2 require a bipolar +/- 24v supply, so a transformer with 18v+18v secondaries is in order. A cascoded F5 can have a higher voltage supply, +/- 32v I think.

The two voltages you show in your image clips are what you should measure at those points, not supply voltages. The "+24v" and "-24v" are the supply voltages required from that schematic.

Also, have you read this? An illustrated guide to building an F5

It might help answer some questions.
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Old 7th October 2012, 04:40 AM   #463
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hi alfa147x,
If you want a 24 volt supply you will need (2) 18volt secondary,after rectification,that's about 24 volts,

In post 458, that .6 is the voltage across the load resistor,I bought 3 cheap meters ,I have one across each .47 3watt resistor and the other meter across the output to measure DC,it should be close as you can adjust the pots for the bias to get zero DC,The article tells this it's at FIRST WATT website,That .6 volt is about 1 amp on the fet's,
There 3 connections on the power supply + - Gnd,Those are on the board too.
NS

Last edited by noSmoking; 7th October 2012 at 04:42 AM.
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Old 7th October 2012, 04:43 AM   #464
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Hi 6L6,
Didn't mean to post over you,was at the same time,lol.
NS
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Old 7th October 2012, 05:00 AM   #465
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Quote:
Originally Posted by 6L6 View Post
Looks like you posted a couple of questions when I was typing.

TO-220 vs. TO-3P/TO-247 The latter is a bigger package. Possible a higher power rating of the discrete diode. Look at the datasheet (of the suggested parts) for the specifics.

The suggested diodes in the TO-220 package are about half the price of the others...

As for voltage of your transformer, the really important question is what version of the amp are you building? F5? Parallel F5? Cascoded F5? The first 2 require a bipolar +/- 24v supply, so a transformer with 18v+18v secondaries is in order. A cascoded F5 can have a higher voltage supply, +/- 32v I think.

The two voltages you show in your image clips are what you should measure at those points, not supply voltages. The "+24v" and "-24v" are the supply voltages required from that schematic.

Also, have you read this? An illustrated guide to building an F5

It might help answer some questions.

Parallel F5. I'm trying to remove digital processing from my turntable setup. I have two speakers so I'm going with the F5 parallel method on this first build. When I get around redoing my living room setup (and if this successful) I'll go another route.

I got a bit confused when I got to the power board portion. Should I with the Peter Daniel PSU board or the DIYAudio PSU Cap Diode Board? or does not make much of a difference?


Quote:
Originally Posted by noSmoking View Post
Hi alfa147x,
At the store site it has a Bom there ,for the boards,and I just go through the Power Supply and write those down to order them,In Nelson Pass articles he tells of a beefier supply to use,I've attached it for you,
If you decide you want some more power,you can go to 32v on the power supply,If you want more you will need bigger heat sinks or a fan or 2,and need to cascode the input fets,You can also remove the limiters and protection circuits ,but don't short the outputs and keep the thermocouples they stabilize voltages on bias from the heat on the heat sinks,I hope this helps you some just go slow and If your stuck ask here,someone will answer!
Have fun!
NoSmoking
NoSmoking, ah thanks for the help. I think I'll go with the standard board for now since this is my first build. It's quite daunting already .

Quote:
Originally Posted by noSmoking View Post
hi alfa147x,
If you want a 24 volt supply you will need (2) 18volt secondary,after rectification,that's about 24 volts,

In post 458, that .6 is the voltage across the load resistor,I bought 3 cheap meters ,I have one across each .47 3watt resistor and the other meter across the output to measure DC,it should be close as you can adjust the pots for the bias to get zero DC,The article tells this it's at FIRST WATT website,That .6 volt is about 1 amp on the fet's,
There 3 connections on the power supply + - Gnd,Those are on the board too.
NS
Ah great. I'll look at that FirstWatt document again.

Quote:
Originally Posted by noSmoking View Post
Hi 6L6,
Didn't mean to post over you,was at the same time,lol.
NS
haha. I think I need to get some sleep. lol
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Old 7th October 2012, 05:04 AM   #466
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Hi 6L6,
Best guide I have saw!I wish I 'd had that a while back!
Ns
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Old 7th October 2012, 05:22 PM   #467
kroyin is offline kroyin  India
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I have a few questions about V2

--JFets with 10mA ldss will need heatsinks. How do you attach them?

---I totally forgot my F5 learning :-). Would zero-ing out the p1/p2
effectively change the 1k resistors to 0 ohm (pre power routine)

-What would be starting setting of p3 (like closest to it not being there) Halfway?

Thank you
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Old 10th October 2012, 11:12 AM   #468
AndrewT is offline AndrewT  Scotland
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jFETs are in To92 plastic packaging.
They normally don't need nor get additional heatsinking.

There are To92 clip on sinks, usually brass coloured. But they don't lower the junction temp of the device much. The To92 is just not designed to dissipate lots of heat.

If heat is a problem, then you should be looking at alternative topologies. eg, cascode to lower voltage Vd, or select lower Id by using duals or lower Idss.

Set the bias resistors to zero ohms. Check the build manual, all the details are in there !!!!!!!!!!!
__________________
regards Andrew T.
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Old 10th October 2012, 01:42 PM   #469
kroyin is offline kroyin  India
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Thanks Andrew..the manual says that if JFETS have an ldss of 10mA then
ensure 'jfets gets some cool air or a little heat sink'.

Would a drop of superglue be a bad idea
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Old 10th October 2012, 02:45 PM   #470
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do you allready have the J-fets? and are they 10mA?
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