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Building an F5 Turbo v2 (in-Progress)
Building an F5 Turbo v2 (in-Progress)
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Old 12th March 2018, 11:29 PM   #231
Todd Mills is offline Todd Mills  Canada
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Default %FT question

Hey Guys

My transformers finally arrived today so I am ready to start wiring everything up. I just need a matched pair of JFETS from the DIY store when they become available.
My question is whether or not I need one speaker protection board(from the DIY shop) for each channel. I am already going to use one inrush board per channel as I am using a 1000VA transformer and 264,000uf for each channel. Does it make sense to run two speaker protection boards or will one suffice. This is a single chassis dual mono build.
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Old 13th March 2018, 12:03 AM   #232
Erlend Sæterdal is offline Erlend Sæterdal  Denmark
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Building an F5 Turbo v2 (in-Progress)
I bought 2 pairs and have one pair I do not need.
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Old 20th March 2018, 12:08 PM   #233
coolnose is offline coolnose  Europe
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Quote:
Originally Posted by Todd Mills View Post
Hey Guys

My transformers finally arrived today so I am ready to start wiring everything up. I just need a matched pair of JFETS from the DIY store when they become available.
My question is whether or not I need one speaker protection board(from the DIY shop) for each channel. I am already going to use one inrush board per channel as I am using a 1000VA transformer and 264,000uf for each channel. Does it make sense to run two speaker protection boards or will one suffice. This is a single chassis dual mono build.
If you want to stay double mono.... yes, you'll need 2 protection boards - 1 per channel
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Old 15th January 2019, 05:48 PM   #234
DiegodB is offline DiegodB  Italy
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Default F5 Turbo V2 build planning

Hello,

I'm presently planning to build the F5T V2.
I have selected a power transformer from Toroidy (Polish company) having 1kVA rating.
The Pass schematics claims for 2x24Vac secondary voltage, would it be a pain to have 2x25 or 2x26 Vac voltage (+- 35Vdc or +-37 Vdc no load)?

Also, since I live in Italy and have easy accessibility to HIFI2000 enclosures, I selected the 5U 500mm depth one (available in Italy). This chassis has 4 heat sinks (250mm x 210mm x 40mm each)

the heat dissipation is a little increased respect to the 400mm depth and maybe a little higher bias could be achieved.

Increasing the supply voltage do you suggest to also fit the cascode circuitry?

Concerning the PSU, from the Pass article, the PSU schematic has a thermostat 75°C in series with the primary winding of the transformer. This thermostat should be fitted on the heat sink?

thanks in advance
kind regards

Diego
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Old 16th January 2019, 05:00 AM   #235
Hikari1 is offline Hikari1  United States
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Location: Seattle
I would cascode the jfets at that voltage.

My f5 v2 with 24v transformer (31v rails) can bias to 1.8 amps in the 5u 400mm chassis. Heat sink temps are 50-53c. You may be able to bias more but the higher rail voltage will make more heat.

Usually pass has the thermal cut off switch standing in free air around the cap bank. Problem with it attached to one sink is one channel may overheat without the other. Also, the switch is on the ac line, before the transformer.

Last edited by Hikari1; 16th January 2019 at 05:03 AM.
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Old 16th January 2019, 09:51 PM   #236
Russellc is online now Russellc  United States
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Building an F5 Turbo v2 (in-Progress)
What value of parts would be used for the cascode? Never have been clear on how these parts are calculated.....

Russellc
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Old 16th January 2019, 10:29 PM   #237
AudioSan is offline AudioSan  Norway
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Originally Posted by Russellc View Post
What value of parts would be used for the cascode? Never have been clear on how these parts are calculated.....

Russellc
railvoltage/(R25+R27)xR27 = cascode voltage. (partnumbers from F5 turbo v3 schematic from the turbo article).


ex: 50Vdc rails. 50/(10+4.75)x4.75=16.1Vdc.


And do the same for R26/R28.

Last edited by AudioSan; 16th January 2019 at 10:34 PM.
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Old 18th January 2019, 10:06 PM   #238
Russellc is online now Russellc  United States
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Building an F5 Turbo v2 (in-Progress)
Thanks for that, I will calculate a little for my application....

Russellc
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