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F4 power amplifier
F4 power amplifier
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Old 1st April 2018, 11:11 PM   #4381
Telstar is offline Telstar  Italy
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Quote:
Originally Posted by Zen Mod View Post
as far as I know , that is exactly last iteration of F4 , you can find it in SM on FW site
That's the one I have too, downloaded from FW site. Tnx.
And I also have the "dyaudio" version with bigger caps and single jfets, which simulates very well in ltspice.
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Old 2nd April 2018, 12:23 AM   #4382
Telstar is offline Telstar  Italy
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Originally Posted by BDP View Post
The question is always how much damping is enough? For many of us we have not had the opportunity to listen to various combinations of amps and speakers to really know where that "enough" lies.
200 is the theoretical limit where diminishing returns end.
But we dont need that much actually, and current delivery is as much important as DF.
I had time to experiment recently with various amp from very low to very high DF, and... it depends on the speakers. The way the XO is made has an influence on both DF and current demands.
F4 has 40 DF into 8 ohms (it halves on 4 Ohm). It is not much but it should be OK for many commercial speakers and even more DIY, especially if active driven directly as shown in the F4 manual.

Excessive DF will not sound right either, it tends to dry the sound excessively and overdampen a pair of speakers with already tight bass (such as TL like mines, closed boxes or OB for instance).
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Last edited by Telstar; 2nd April 2018 at 12:24 AM. Reason: grammar
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Old 4th April 2018, 07:51 PM   #4383
Variac is offline Variac  Costa Rica
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F4 power amplifier
just an FYI:
we still sell the boards for the F-4 at the diyAudio Store

F-4 – diyAudio Store
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Old 4th April 2018, 11:34 PM   #4384
Telstar is offline Telstar  Italy
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I know. I'm waiting to make and order cause I dont know yet if I need to bridge it or not.
How's the stock?
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Old 7th April 2018, 02:36 PM   #4385
Telstar is offline Telstar  Italy
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Originally Posted by GRollins View Post
I have a buddy who wants total, absolute darkness in his listening room. I've suggested increasing resistors, detaching the lead to the LED, switch for the power light, ignoring the lights, you name it.
His solution is ordinary black vinyl electrical tape over the LEDs.
Doesn't stick all that well to anodized aluminum, leaves a gummy residue, and looks like hell. He doesn't care.
To each his own.

Grey
LightDims Original Strength - Light Dimming LED covers and Light Dimming Sheets for Routers, Electronics and Appliances and more. Dims 50-80% of Light, in Minimal Packaging. - Ceiling Pendant Fixtures - Amazon.com

This works perfectly to dim blue leds and stick well to aluminum frontplates.
I have used it for those damn blue leds on other devices

For total cover, there is another version, which would look much better than electrical tape:
LightDims Black Out Edition - Light Blocking LED covers / Light Dimming Sheets for Routers, Electronics and Appliances and more. Blocks 100% of Light, in Retail Packaging. - Light Dims Led Light Blocker - Amazon.com
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Old 7th April 2018, 02:45 PM   #4386
Zen Mod is online now Zen Mod  Serbia
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F4 power amplifier
great !!

though , I;m usually using resistor for that



take 9W WW , some super glue , and glue resistor in front of led

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Old 7th April 2018, 03:00 PM   #4387
anatech is offline anatech  Canada
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F4 power amplifier
I have a customer that does the same thing with electrical tape. Look great over the large power meters!

-Chris
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Old 7th April 2018, 03:04 PM   #4388
Telstar is offline Telstar  Italy
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I used for a DAC which was very cramped inside.
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Old 7th April 2018, 06:02 PM   #4389
Andrzej Sochon is offline Andrzej Sochon  Poland
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Originally Posted by anatech View Post
I have a customer that does the same thing with electrical tape. Look great over the large power meters!

-Chris
In the deep past I used result of punching: small black circles/pucks taken from typical puncher - instead of paper I used special stiff plastic tape with a glue layer. Such tapes ware used for embosing white text on tape. It was DYMO hand printing/embossing tool and tapes, variety of colours. The only problem was that the puncher sometimes makes a white border around the puck.

Black tape to completely suppress the light, red tape to slightly suppress too bright red LED.

Andrzej

Last edited by Andrzej Sochon; 7th April 2018 at 06:06 PM.
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Old 9th April 2018, 12:21 PM   #4390
william2001 is offline william2001  United States
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I am liking the concept of these "hot followers". Not sure why I didn't build one sooner. Well, actually I did with the BA-1 but I didn't fully flesh out the idea. It opens up a whole world of high gain SS and tube circuits that were a poor match with my previous medium and high gain amplifiers. I cleaned the dust off of my old Bottlehead Foreplay 2 and have that in front of my new F4's right now, really the first time I have been able to get a feel for what it sounds like. No mods on that really, just better output caps and DC filaments. Before it simply had "hair trigger" volume pots and throwing away most of the signal to ground. I added resistors to pad the input to make the volume pots use-able, but if I remember correctly it really affected the sound quality in a negative way. Obviously some poor system gain structure right there, so the thing just never got used.
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