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A guide to building the Pass F4 amplifier.
A guide to building the Pass F4 amplifier.
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Old 30th June 2020, 03:28 AM   #1931
yoshida is offline yoshida  Japan
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Quote:
Originally Posted by cal3713 View Post
Looks amazing Yoshida. And I love that case, just beautiful.

Can you provide a source for your transformer?
The case is takachi's HY177-33-33SS.
This heatsink is a bit smaller for F4 so I reduced the bias a bit.

The R-core transformer was custom made by Phoenix Corporation. They are popular for DIYer in Japan because they accept custom orders for amateurs.
However, they do not seem to accept small lot orders from overseas.
It would be nice if the Store handles it.
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Old 30th June 2020, 06:14 AM   #1932
Norrlands Guld is offline Norrlands Guld  Sweden
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Originally Posted by syracuze View Post
Re. Your 2nd question: no it will not affect the class-a envelope of the amp: while each half of balanced monoblock will see 2 ohm load, it will also need to swing half of the voltage (as balanced mono brings 6db voltage gain).

And this corresponds to same current need

Re. Your 1st question: there are many highly regarded amplifiers with high output impedance: e.g. first watt sit’s, dartzeel’s, dan dagostinos come to mind (see stereophile reviews), so not necessarily a bad thing: ideally you try for yourself.

One thing is for sure: balanced monoblock enables substantial 2nd harmonic cancellation which also helps for lower intermodulation distortion.

And if you are digital only, you might even be ok with a dac with volume control that can swing 6vrms from balanced output (which corresponds to ~10w power per channel to 4 ohms), and ditch the preamp, just saying..
Great info. Many thanks. I actually have a DAC with volume control and 6v at XLR. How did you know

If 6 vrms is not enough what XLR vrms is needed for max output for bridged balanced F4?
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Old 30th June 2020, 10:23 AM   #1933
syracuze is offline syracuze  United Kingdom
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Quote:
Originally Posted by Norrlands Guld View Post
Great info. Many thanks. I actually have a DAC with volume control and 6v at XLR. How did you know

If 6 vrms is not enough what XLR vrms is needed for max output for bridged balanced F4?

You can use the classical formula
Power = VxV / R
To calculate voltage swing need

Say you need 50 watts, for 4 ohm load, applying the above formula ->
V = sqrt (50 x 4) which makes roughly 14 V rms.

That being said, I suggest you first test the loudness level with 6 Vrms output then look for any higher gain options.
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Old 30th June 2020, 11:09 AM   #1934
Norrlands Guld is offline Norrlands Guld  Sweden
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Originally Posted by syracuze View Post
You can use the classical formula
Power = VxV / R
To calculate voltage swing need

Say you need 50 watts, for 4 ohm load, applying the above formula ->
V = sqrt (50 x 4) which makes roughly 14 V rms.

That being said, I suggest you first test the loudness level with 6 Vrms output then look for any higher gain options.
I looked at this post.


Is it correct that I would only get 18w in Class-A 4 ohm bridged bit up to 50w Class-A parallel?

what's the best Pass take on 4ohm load with balanced input?
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Old 30th June 2020, 12:33 PM   #1935
Dennis Hui is online now Dennis Hui  Canada
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A guide to building the Pass F4 amplifier.
It's around that range, assuming you are using the standard ~1.3A bias and ~ +/-24V
rails.

For bridged, the bias current is the limiting factor, while for parallel, the limit is the
rail voltage.
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Old 30th June 2020, 01:00 PM   #1936
myleftear is online now myleftear  Switzerland
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A guide to building the Pass F4 amplifier.
Quote:
Originally Posted by Norrlands Guld View Post
I looked at this post.


Is it correct that I would only get 18w in Class-A 4 ohm bridged bit up to 50w Class-A parallel?

what's the best Pass take on 4ohm load with balanced input?

You’ll want to most probably ditch the „only“ before that 18W. Just a guess.
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Old 30th June 2020, 01:01 PM   #1937
Norrlands Guld is offline Norrlands Guld  Sweden
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Originally Posted by myleftear View Post
You’ll want to most probably ditch the „only“ before that 18W. Just a guess.
Sorry my English is not great. What do you mean?
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Old 30th June 2020, 01:43 PM   #1938
Dennis Hui is online now Dennis Hui  Canada
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A guide to building the Pass F4 amplifier.
Perhaps that you may find 18W sufficient. Of course, that depends heavily
on your speakers and listening space and personal preference.
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Old 30th June 2020, 01:52 PM   #1939
Norrlands Guld is offline Norrlands Guld  Sweden
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Originally Posted by Dennis Hui View Post
Perhaps that you may find 18W sufficient. Of course, that depends heavily
on your speakers and listening space and personal preference.
Yes sure.

But which version would you chose? I am ok with 50w max power.

Use bridged and get 18w Class-A and max power 200w and damping factor 20

OR

Use parallel and get 50w Class-A and max power 50w and damping factor 80.
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Old 30th June 2020, 05:02 PM   #1940
myleftear is online now myleftear  Switzerland
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A guide to building the Pass F4 amplifier.
Quote:
Originally Posted by Norrlands Guld View Post
Sorry my English is not great. What do you mean?

I tried to say (A guide to building the Pass F4 amplifier.) that only 18w out of a f4 could be very very good. Sorry on my side (my Englisch is sometimes weird)
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