A guide to building the Pass F4 amplifier

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6L6

6L6

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To hit full power, you need a gain of about 20 and the ability to swing +/-24V. Even more if you are driving the F4 bridged. That is a very tall order. Impasse, Pumpkin, are tailor-made for the job, many tube designs have gain and swing, or just add a 1:2 or 1:4 transformer to the input if the F4 and use your current preamp.
 
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tonyEE

tonyEE

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6sX7 said:
running F4 monsterblocks with balanced input, they are very, very neutral. So neutral, I'm building various preamp circuits as stand-alone front-ends/gain stages to play with flavor. Although, I have to rethink this as, after moving, the listening space is much smaller and the Benchmark DAC will drive them quite handily into hurty volumes.
Click to expand...

How much voltage does the Benchmark swing?
 
tonyEE

tonyEE

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6L6 said:
To hit full power, you need a gain of about 20 and the ability to swing +/-24V. Even more if you are driving the F4 bridged. That is a very tall order. Impasse, Pumpkin, are tailor-made for the job, many tube designs have gain and swing, or just add a 1:2 or 1:4 transformer to the input if the F4 and use your current preamp.
Click to expand...

Get a used Conrad Johnson preamp.... I looked at the specs for both of mine and they both put out a max of 20Vrms with a gain of 25db... they both drive the F4 handily. Unfortunately they are both single ended...

To be honest.... if I had to get off this merry go round, one of the CJ preamps. the F4 and some of my speakers would make a fantastic system... but then, what I would I do with the other equally fantastic stuff?

Will the Iron Pre balanced drive a pair of F4?
 
tonyEE

tonyEE

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I understand your point... but sometimes you need to realize that what you build may not be as good... I'm after the best sound so I admit that some people do know better than me... and sometimes the market is upside down...

When a CJ preamp sells for less than a Marantz 2325 with "new LEDs" then...

And then sometimes... well, you just have to have both something that was custom built and something that was strictly commercial..

The only limitation is the size of your house and your wife's patience. ;-)
 
tonyEE

tonyEE

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H

Holzarbeiter

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tonyEE said:
Do BOTH.

It's a hobby.
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It is NOT a hobby. It was decades ago.

Now it is a means to keep what "skills" I had from degenerating further to be able or NOT leave this bedroom 'maschine' shop to get back to building/restoring what I used to be able to do. In a real Maschine Restoration Shop.

This was mentioned to you in a PM you sent months ago.
 
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skrifa

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Joined 2017

@KevinHeem​

thanks, good to know

@Zen Mod​

I can solve the mosfet issue by buying paired ones,
I'm more concerned about whether the dual power supply (four rails) in each amplifier will cause problems with connection and produce noise later. Does everything connect in the same way as when it is a single power supply (two rails) if I run them as parallel monoblocks and later as bridged via balanced inputs. Does anyone have this experience?
 
Zen Mod

Zen Mod

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just chill

academically speaking, when bridging, better to have one set of references (common PSU for one case) but in praxis - go for it

if you made them proper (meaning, both channels in one case equally good) no reason to fret

as bonus - you'll always be happier when you use them in usual (one case stereo) way, knowing that you did best possible
 
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