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

[Dadbeh]

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

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]

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.

 

[Dadbeh]

thanks, man. im learning so much. im a little overwhelmed though, by all the information im reading and have 2 million questions. damn, I love this place

 

[Dennis Hui]

I believe the 0.47 ohm is also used in the power supply PCB. Go for the cheaper
one and get a bunch. (100 would be good for a few amps.)

Dennis

 

[Dadbeh]

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]

Bourns not Bournes

Just try typing in 3296W in the search bar

Important Note: Check the bloody pinout pattern for the pcb and trimpot. 3296W may not be applicable for your needs.

 

[2 picoDumbs]

Also check 3299Y as a possibility.
This one may meet the pinout you need.

 

[Dadbeh]

Guys when you say check the pins? what do you mean? i mean I can look at the picture of the PCB board where I see 3 holes and the picture of the actual component has 3 pins? lol should i just eye ball it?

 

[2 picoDumbs]

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.

 

[Dadbeh]

gotcha! appreciated

 

[Dadbeh]

this is the pcb board:

3296w has 3 straight pins
3299y has 3 pins triangular.

what do you think?

 

[Zen Mod]

pcb is made for both

 

[Dadbeh]

great. The diodes are 1N4739 9.1V but there is no power rating or tolerance provided. is 1 watt and 5% good? does it matter which brand, in your opinion?

 

[2 picoDumbs]

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.

 

[Dadbeh]

thanks for the info. is this ok for the trans?
AS-4225 - 400VA 25V Transformer - AnTek Products Corp

 

[Dennis Hui]

thanks for the info. is this ok for the trans?
AS-4225 - 400VA 25V Transformer - AnTek Products Corp

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.

 

[2 picoDumbs]

You want AS4218, for 23Vdc

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

 

[oreo382]

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]

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?

 

[wdecho]

You can get by with 300VA but I usually go for 400VA. The size of the transformer increases with the VA rating which will put it closer to the input transformers.