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-   -   F5 Turbo Builders Thread (http://www.diyaudio.com/forums/pass-labs/207103-f5-turbo-builders-thread.html)

ungie 19th February 2012 09:47 PM

F5 Turbo Builders Thread
 
This thread is intended to discuss the preparation and construction phase of building an F5 Turbo. A thread already exists for the circuit boards, so I'm guessing we will see a lot of activity here!

ungie 19th February 2012 09:54 PM

To start it all off, I'll outline my plan:

I have some nice, single output winding 35V, 750VA transformers that have been sitting around collecting dust. Two of these transformers will be used per channel. I'm planning on monoblock F5 Turbos running at ~+/-48V rails. This will be based on the F5 Turbo V3 schematic, without any modification initially.

A few questions:

What are the current, reliable sources for matched 2SK170/2SJ74 devices?

For the output devices, is matching even more critical in the F5 Turbo than the standard F5, given the diode action across the source resistors?

For those that built an F5, how many output devices did you purchase to make sure you got enough matched sets?

More to follow...

geraldfryjr 19th February 2012 10:00 PM

My question is what Jfets can be used for the input stage and can they be source from the more common parts house's like Digikey or Mouser or even Newark?

If so which ones are they?

I don't like having to chase down obsolete parts that are not being made anymore as well as the very high prices when they are actually found.

A few of the semiconductor company's do make some complimentary N and P jfet's and some that are matched in one package.

Can any of these be used?

Please excuse my ignorance on this as I don't no may way around small signal jfet's too good.

I really would like to start building some F5 amps and this is my only stumbling block.



Thanks !!

jer :)

Bksabath 19th February 2012 10:06 PM

1) Spencer and while ago Blues

2) Yes diode action take source resistor out and source resistor are there as a cushion for poor matching

3) I got 100 each FQA12P20 and FQP19N20 (could not get the FQA type FQP is TO220)

Got them from Farnell and batch is all over the place avoid if you can as looks like loads of different production runs mixed up.

Do you have Papa Pass mosfet matching paper?

48 V rails sound realy good and most probably what I will go for on nex build

you will need loads of 63 V capacitors and with current involved I would scale up on Papa design.

Bksabath 19th February 2012 10:11 PM

Quote:

Originally Posted by geraldfryjr (Post 2913833)
My question is what Jfets can be used for the input stage and can they be source from the more common parts house's like Digikey or Mouser or even Newark?

If so which ones are they?

I don't like having to chase down obsolete parts that are not being made anymore as well as the very high prices when they are actually found.

A few of the semiconductor company's do make some complimentary N and P jfet's and some that are matched in one package.

Can any of these be used?

Please excuse my ignorance on this as I don't no may way around small signal jfet's too good.

I really would like to start building some F5 amps and this is my only stumbling block.



Thanks !!

jer :)

Same for all Liner make LSK170 and promised the 2SJ74 equivalent but nothink so far

Papa Pass is the best person to keep naghin to give us same alternatives.

F6 with devices currently in production is my bighest dream

ungie 19th February 2012 10:14 PM

I'm planning on using:

FQA36P15 P Channel QFET
FQA28N15 N Channel QFET

Filter capacitance will be 264,000uF per monoblock.

Bksabath 19th February 2012 10:18 PM

One thing be realy nice and abowe my capability

Spec sheet with plans for current demands number of devices in parrallel

Power dissipation and sinks.

Capacitance of those is about 2 times the ones on the specs.
so help (explanating delucidification for the mentaly mechanicaly minded) regarding this is certanly a big fawor to ask.

264,000 sound jut about right

Planning for CRCRC wuld also be big improvment especialy with couple of cokes

UKToecutter 19th February 2012 10:28 PM

Quote:

Originally Posted by ungie (Post 2913850)
I'm planning on using:

FQA36P15 P Channel QFET
FQA28N15 N Channel QFET

Filter capacitance will be 264,000uF per monoblock.

ungie,

How are you getting to the 264,000uF

ungie 19th February 2012 10:46 PM

Quote:

Originally Posted by UKToecutter (Post 2913868)
ungie,

How are you getting to the 264,000uF

8 x 33,000uF/63V per channel.

ungie 19th February 2012 10:52 PM

Quote:

Originally Posted by Bksabath (Post 2913856)
One thing be realy nice and abowe my capability

Spec sheet with plans for current demands number of devices in parrallel

Power dissipation and sinks.

Capacitance of those is about 2 times the ones on the specs.
so help (explanating delucidification for the mentaly mechanicaly minded) regarding this is certanly a big fawor to ask.

264,000 sound jut about right

Planning for CRCRC wuld also be big improvment especialy with couple of cokes

I'm going to start off with 8 output devices per channel, as per Papa's V3 schematic.

Bias will be determined once I see how hot the sinks get. Heatsinks are 11" x 11" x 2" from R-Theta from the long-ago Aleph-X group buy. Each bank of N or P channel devices will get their own heatsink.

I'm also thinking about starting with CRC and maybe going CRCRC later. Instead of the paralleled 3W, 0R47 resistors Papa has in his schematic, I'm going to use a single 0R07/25W Dale per rail mounted to the main heatsinks. Or at least that's what I'm currently considering!


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