The F6 build of the century :) (I want to learn everything)

Dadbeh

Member
2010-09-17 11:32 am
Hi guys. Im setting to build it right. Im a physics student and I know a bit of the fundamentals (Ohm's law) but I have never done anything like this and I have questions every single step.

Im going through the BOM and the second resistor is 0.47 ohm. I looking on mouser.com and I have narrowed it downn to this

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now They match word by word afaiks, so what gives? the bottom one has an icon that says NRND, so what's up with that?
 

needtubes

Member
2003-05-24 9:23 pm
They do not match exactly. Notice one is 3SJR47 and the other is 3FJR47. The F uses iron leads, so might be considered inferior for audio use. I would go with the S series for peace of mind. Plus, they are cheaper, too.

NRND means 'not recommended for new designs'. This model has (sadly) been discontinued.
 
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Dadbeh

Member
2010-09-17 11:32 am
thanks for the thoughtful tips guys. it's helped me greatly. Im almost done with having all the reistors ready to order. one thins: in the BOM it says:

P1,2 5Kohm 25 turn Bourns 3296W or equivalent (You can use a single-turn pot if you like, but the 25-turn will make setting the amplifier much easier.)

i cant find this item. i searched all over mouser. there is nothing called turn bournes
 

2 picoDumbs

Member
2013-09-06 9:35 am
If the pcb has 3 holes in straight line then you need a trimpot with 3 pins in a straight line.
If it is a triangular pattern on the pcb you'll need a trimpot with a triangular pattern.
Some pcbs will have both patterns to give the builder more options.

Also check pin spacing.
 

2 picoDumbs

Member
2013-09-06 9:35 am
I think the consensus here is that the most appropiate Zener is between 5.6V and 6.8V.
I used 5.6V, it works perfectly.
Papa recommended 5.1V, some people claimed that they had issues with biasing using 5.1V Zeners. 9.1V is overkill.

In any case Zeners are useful, they are also cheap, buy a few at different voltage ratings.

1/2 Watt is usually adequate for most tasks.
 
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thanks for the info. is this ok for the trans?
AS-4225 - 400VA 25V Transformer - AnTek Products Corp

No, the voltage (25 is too high). It will cook your jfets. You need an 18 Volt transformer which gives around 23 Volts DC after rectification and filtering.
The 400 VA 18 Volt is out of stock. I used this one ---
AN-5218 - 500VA 18V TRANSFORMER---for my build and it worked perfect and its in stock. It is not shielded but that didn't cause me any problems. It is $55 compared to $51
for the 400 VA, only $4 more.
 

Dadbeh

Member
2010-09-17 11:32 am
The voltage is too high; you want something like this:

AS-4218 - 400VA 18V Transformer - AnTek Products Corp

After rectification, the rails should then be in the +/-23V range under load.

it's OOS

You want AS4218, for 23Vdc

AS4225 is far too high. The transformer ratings are Vrms.

gotcha

No, the voltage (25 is too high). It will cook your jfets. You need an 18 Volt transformer which gives around 23 Volts DC after rectification and filtering.
The 400 VA 18 Volt is out of stock. I used this one ---
AN-5218 - 500VA 18V TRANSFORMER---for my build and it worked perfect and its in stock. It is not shielded but that didn't cause me any problems. It is $55 compared to $51
for the 400 VA, only $4 more.

ok I didnt realize 25 was that high. so that's out. but what about the 20 Vrms version? AS-4220
so you're saying getting 500VA 18Vrms would be a better fit that let's say 400VA 20 Vrem shielded?
 
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