F5 Turbo Builders Thread

[Nikitas]

And also I noticed that the heatsink within about one minute had room temperature!That was fast!

 

[buzzforb]

The 2sk1530 has lower Vgs for given current in comparisonto 2sj201. If youhad both pots set to 1.5V, you would have sythe sk1530 biased fairly high, while the 201 would just be just turning on. Takr a look at the datasheets for appx Vgs for a given current.

 

[Nikitas]

I had them both set at 3V like we had discussed.

 

[buzzforb]

THey will work great and will plug directly in with little effect. Just look up their datasheet and try to get an idea of the VGs needed for the bias you want. Before plugging them in, set your pots below that point about 25%-50%. You have tested you FE and all is good. As long as you mount and isolate them correctly, you should be able to listen within the day.

 

[Zen Mod]

Odysseas - goal is to set them at desired current - measuring voltage across one of source resistors ;

that voltage is information about current flowing through resistor and mosfet itself



who cares what's Ugs ......


there are few tutorials floating around , and reading them few times is worthwhile

 

[Nikitas]

Yes, thanks ZM, looking at the differences at the datasheets of the two toshibas, I wonder what would that (desired) current is. I just want to be at all times class A.
There is quite some difference at the current drain at the same voltage, like buzz pointed out.

 

[buzzforb]

Shoot for 300mV to 400mV across the Rs. Start at 300 and let it warm up.

 

[Zen Mod]

Yes, thanks ZM, looking at the differences at the datasheets of the two toshibas, I wonder what would that (desired) current is. I just want to be at all times class A.
There is quite some difference at the current drain at the same voltage, like buzz pointed out.

do what buzz buzzed few times to you , already ;

stay in ballpark for your project (didn't read which iteration you are exactly building) keeping in mind that (say) 40W per device and 55C at heatsink are limits which you must respect

 

[buzzforb]

THis is probably done wrong, but i think this is my 1W performance

 

[6L6]

Awesome!

How do you read that graph... ?

 

[buzzforb]

I didnt realize how blurry it was. The blue is loopback showing soundcard distortion and the red is the distortion of the F5T at 1W. Its a breakdown of the harmonic structure of the distortion. Like I said, I am not 100% sure of its validity, but i think it is right. My ears seem to agree

 

[6L6]

You like it? I'm currently building mine...

 

[buzzforb]

Yes. It is very good from top to bottom. I cant say that it is my favorite, but that is yet to be decided. I have to bring forth proper competition. I did not like the F5, and hearing the F5T has sold me on the multiple output concept. Of course my system has to be considered.

 

[Marra]

I decided to check out my p/s so hooked up the transformer/rectifiers and caps which loaded with nothing more than 3k3 bleed resistors and a couple of led's is giving me +- 38V dc.What sort of voltage drop can I expect with a V2 amp?
The transformer is 350VA with 25-0-25 secondaries.

 

[Nikitas]

You should be careful with 38V. It's not extreme, but it is risky.
What do you mean <<What sort of voltage drop can I expect with a V2 amp?>>?

 

[buzzforb]

multiply your secondary times 1.3 for a good approximation. 38v is fine as long as you you the cascaded version, but iexpect your rail to be closer to around 34V loaded. 350VA is going to be strugglinf under fully biased V2 unless your have dual mono setup.

 

[henryve]

To be honest I would not use anything less that 650VA for the V2. Even better would be 2 X 500VA for a dual mono setup.

For a V3 I would definitely suggest monoblocks, with a 750VA as minimum per monoblock and 1000VA as a comfortable requirement.

 

[henryve]

BTW, it would be interesting to compare the V2 with my KSA50 clone. Both of these should be good at the bottom. The top is where I believe the V2 could be better.

 

[buzzforb]

I would be willing to bet it will crush it sonically.

 

[Marra]

Sorry I should have said this is per channel.I used the transformers previously to power an Aleph 5 without any problems and the voltages sat at +-34/35 volts.It will be cascoded. I am rubbish with the math