F5 Turbo Builders Thread

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Daniel(Del)

Member
Joined 2005
jacco vermeulen said:
The J74/K170 are 400mW devices, doesn't mean they're supposed to dissipate the full amount.

Standard practice is 50% Max, read chapter 6 of the Toshiba semiconductor reliability handbook, referenced to in any Toshiba part datasheet.

50% is a bit conservative.
The standard F5 design has J108/K370, 200mW devices.
Vds is a little under 20V, derated Idss is 6mA, makes short of 120mW.
Or ~60% of the 200mW Max Pd.

50% derated J74/K170 handle 200mW, at 10Vds good for 20mA drain current.
High current good : higher Idss, better numbers, e.g. capacitances, lower noise.
High voltage bad : more heat, more gate leakage, etcetera.
Click to expand...

Sorry to ask, but is this an answer for the bl vs v question?
 
jacco vermeulen

jacco vermeulen

Member
Joined 2004
The answer was that (all) Violets can be used in a cascoded F5, in a standard F5 only the lower Idss V-grades due to the elevated dissipation. (or stick heatsinks on them, shave 'm off, etc.)

Personally, i don't have a problem with Blue JFETs in parallel. If it works in a head-amp, it'll work for power amps. Papa did as well in the concept amps for the top of the line Xs.

Prettiest of course would be J72/K147 V's in the +20mA Idss range.
 
A

arche13

Member
Joined 2009
Hello
I plan to make a F5 turbo V1, on the plan the resistances of triggers mosfet (R13 to R16) are of values 47,5 ohms. In the series Dale RN60 1 / 4W 1 %, I have the choice between two values: 49,9 ohms or 44,2 ohms. Which of both values is the best adapted
Thank you for your help
Cordially
 
D

Daniel(Del)

Member
Joined 2005
jacco vermeulen said:
The answer was that (all) Violets can be used in a cascoded F5, in a standard F5 only the lower Idss V-grades due to the elevated dissipation. (or stick heatsinks on them, shave 'm off, etc.)

Personally, i don't have a problem with Blue JFETs in parallel. If it works in a head-amp, it'll work for power amps. Papa did as well in the concept amps for the top of the line Xs.

Prettiest of course would be J72/K147 V's in the +20mA Idss range.
Click to expand...

Now I see, thank you Jacco
 
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lhquam

Member
Joined 2010
Bksabath said:
I have source for FQA19N20 they sell minimum of 1000 pieces so no go for me there
If one has the cash to go for it PM.
FQA19N20C is one different kind of beast with more capacitance and more power then there is the FQA19N20 L even more power and again more capacitance.

I use FQP19N20, which is closer match(current wise) for FQA12P20 but has TO220 pack
Having bought 100 each I can spare a few so Pm
They have been running since last August on MY F5.

I quite like the idea to use the 36 and 28 as you mention I am not shure how they perform and my Knolledge is limited so it will have to be a build and see thing the gain of those 2 is quite interesting so try them and report back.

I have seen post about potential buy of the original pair 19 / 12 will need to search for that
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I just made measurements of a F5 amplifier using FQA36P15 and FQA28N15 mosfets. The distortion measurements of the amplifier are disappointedly high, probably due to the high input capacitance. I am seeing about .004% THD at 1 kHz, 1 watt into 8 ohms. Unlike all of my other F5 builds, the P3 adjustment will does not reduce the 2nd harmonic below the 3rd harmonic.

I am still looking for a source for FQA19N20C and FQA12P20 or 2SK1530 and 2SJ201. I need 4 each for a pair of balanced amps. It would be nice to have 4 more each for a future build. If I cannot find any other source, I am willing to try the TO-220 counterparts (FQP19N20 and FQP12P20).
 
Bksabath

Bksabath

Banned
Joined 2007
lhquam said:
I am still looking for a source for FQA19N20C and FQA12P20 or 2SK1530 and 2SJ201. I need 4 each for a pair of balanced amps. It would be nice to have 4 more each for a future build. If I cannot find any other source, I am willing to try the TO-220 counterparts (FQP19N20 and FQP12P20).
Click to expand...

Send me a PM and we take it from there I got same FQP19N20 to spare.
I am using those with the FQA12P20
 
Bksabath

Bksabath

Banned
Joined 2007
lhquam said:
With your method of clamping the devices to the heatsink using a metal bar, how would you deal with devices with of different thickness, such as TO-220 and TO-3P?
Click to expand...

That is prety easy as they are in 2 separate parts of board use 2 bars
one for TO220 and one for TO247 :D
There are loads of beter pictures about the heath spreaders and clamping on
MY F5 tread

I got no PM from you.
Pity because I was interested in the distortion mesurament you taken and was going to send you 2 pairs of matched FQP19N20 for the price of the postagge :confused:
 

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L

lhquam

Member
Joined 2010
Bksabath said:
That is prety easy as they are in 2 separate parts of board use 2 bars
one for TO220 and one for TO247 :D
There are loads of beter pictures about the heath spreaders and clamping on
MY F5 tread

I got no PM from you.
Pity because I was interested in the distortion mesurament you taken and was going to send you 2 pairs of matched FQP19N20 for the price of the postagge :confused:
Click to expand...


The clamping I need to do is 4 devices in a line: TO-3P MOSFET, 2 MP915 Caddock resistors, TO-3P MOSFET. The Caddocks are 2mm thinner than the MOSFETs. I am considering some type of compressible material (plastic foam?) as a shim for the Caddocks.
 
flg

flg

Member
Joined 2005
In my bis we quite regularly line up 5-6 pair of transistors in line on a board and cover all of them with the same H.S. We use a material we call Gap Pad(trade name?). There are several brands of such stuff, 3M comes to mind also. It ussually has a dielectric rating(perportional to thickness but, high enough we don't care) and a thermal rating(naturally, also porportional to thickness). There is another material I have used that we call Body Filler(humorous). It looks like body filler you would use to fix dents in your auto. It's blue, and you mix it up like body filler. It dosent cure to a nice hard plastic though. It is removeable.
Both of these substances are designed to planerize the devices to the heat sink. That is, take up the hieght differences with a thermal spongy sheet of raz-ma-taz or goop for good contact to the H.S..
:D
 
KatieandDad

KatieandDad

Member
Joined 2011
Has anyone had a successful F5(T)v3 build yet ?

I'm intrigued to see how much heat they are ditching.

I've got a DIY Aleph 4 which gets quite - but not excessivley - hot.

I'm wondering wether I can't use it as a donor for a dual mono build. ie keep the chassis, heatsinks and power supplies. +/- 48V may be too high even for the V3 ???
 
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A

AudioSan

Member
Joined 2009
KatieandDad said:
Has anyone had a successful F5(T)v3 build yet ?

I'm intrigued to see how much heat they are ditching.

I've got a DIY Aleph 4 which gets quite - but not excessivley - hot.

I'm wondering wether I can't use it as a donor for a dual mono build. ie keep the chassis, heatsinks and power supplies. +/- 48V may be too high even for the V3 ???
Click to expand...

there is no problem running the v3 on +/-48V
your aleph4 dissipates around 200W pr channal?
thats around 2A bias on +/-48V supply.
 
KatieandDad

KatieandDad

Member
Joined 2011
My A4 has only got 2 x 500VA transformers - it is in dual mono configuration.

The 6 x IRFPs are biassed at a combined 2.4A (ie 400mA each) with ROCK STEADY 48V CLC rails.

The Aleph 4 has four groups of 6 x IRFP. 2 x Current Sources and 2 x SE Amplifiers.
 
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