[jrebman]

Just curious, but would any of you guys build a pair of F4 monoblocks on commission, and how much would you charge?  Just something I'm considering doing sometime this year as I really love my Carina, but I need more power for better dynamic performance.  Please respond via PM or email.

Anand, I'm going to be very interested in hearing Mike G.'s Abbey's when he gets them done.

-- Jim

[sts9fan]

I really liked the F4 Aikido(4X6SN7) combo with my Druids.  I am running a F3 now and building a Aikido of my own.

[jrebman]

STS9,

Edited, and hopefully to your approval.  I post it where the builders are.

Somehow your post doesn't seem all that pertinent to building an F4 either. ::

[sts9fan]

your right I am sorry.  I have run a DIY F4 with Aikido though.  I was not attempting to be inflammatory or accusatory.

[jrebman]

No problem.  I apologize, I have a bad case of bronchitis and feel like crap and am more than a bit on edge today.

-- Jim

[TomS]

I bet my F4's would work nicely with my future dream speaker - the Geddes Abbey. Nice job Tom!

Anand.

Yes, I would love to hear that myself, so you need to get started on those   Looking at your other efforts I'm sure they'd be something very special.

[JoshK]

An aikido preamp would likely work well for driving the F4's, but I'd use a 6SL7 or 12ax7 upfront and keep the cables really short. 

I have an Aikido but it is single ended and I'd like to run them as balanced mono's.  John B sent me a few details on his balanced version but I'm still waiting for more info from him.  Unfortunately it needs both +/-300vdc so won't be the easiest to implement.

Hmm... John Broskie has shown the balanced version of the Aikido many times but doesn't yet offer his boards for it yet (although he prototyped them already).  Nowhere in what he's shared is a bipolar supply.  All the versions he has shown have been just B+ ~ 300vdc.   If you build point to point, one doesn't need to wait for Broskie to build a balanced Aikido all the details are already there. 

But you don't really have to do a balanced Aikido to get a balanced output either.  There are more than one way to skin a cat.  There are pluses and minuses for every method. Pick your poison.  If you use an output transformer (1:1, splitting, step down, whatever) you can easily derive a balanced output. 

[TomS]

An aikido preamp would likely work well for driving the F4's, but I'd use a 6SL7 or 12ax7 upfront and keep the cables really short. 

I have an Aikido but it is single ended and I'd like to run them as balanced mono's.  John B sent me a few details on his balanced version but I'm still waiting for more info from him.  Unfortunately it needs both +/-300vdc so won't be the easiest to implement.

Hmm... John Broskie has shown the balanced version of the Aikido many times but doesn't yet offer his boards for it yet (although he prototyped them already).  Nowhere in what he's shared is a bipolar supply.  All the versions he has shown have been just B+ ~ 300vdc.   If you build point to point, one doesn't need to wait for Broskie to build a balanced Aikido all the details are already there. 

But you don't really have to do a balanced Aikido to get a balanced output either.  There are more than one way to skin a cat.  There are pluses and minuses for every method. Pick your poison.  If you use an output transformer (1:1, splitting, step down, whatever) you can easily derive a balanced output. 

What he shared with me was quite different from the hints on TCJ, with just a pair of 6SN7's.  Very interesting design.

I realize there are a lot of ways to do it, which is why I'm putting together the Pumpkin preamp with dual mono shunt supplies   Should be a fun project, but so far assembling all the parts is a major challenge and it's more expensive than you might think without a rich parts bin to draw from.

[JoshK]

That's Broskie for you.  Constantly coming up with something different than the version before.  I mean that in a good way.  He is truely a thinker and willing to go against the norm. 

[zybar]

Just a little update.  I finally built the second F4 up to enable balanced 100w Class A monoblocks.   Since the Conrad heatsinks work so well, I was able to bias them a bit higher than before (about 0.6A per device).  Nice and toasty for the winter months.

Now on to the Pumpkin/Shunty balanced preamp project to swing the F4's to full output and finish up an F5 for the top end of my CS2's.

Any new updates Tom?

George

[poseidonsvoice]

Don't you use the F5 for the satellite and F4's for the bass on your CS2's, or perhaps I'm mistaken? Dig the Real Traps room treatment, in fact it was because of fellas like Zybar and TomS that I decided to go with GIK treatments. Less expensive than Real Traps but good nonetheless. In fact, Ethan Winer's videos, and descriptions of absorption, diffusion, etc...are very down to earth and easily understood.This will at least get my room ready before I tackle the Abbey's.

Anyway, comments from TomS most welcome as he is paving the way here in the Lab with the First Watt builds!

Anand.

[bellicon]

What he shared with me was quite different from the hints on TCJ, with just a pair of 6SN7's.  Very interesting design.

I realize there are a lot of ways to do it, which is why I'm putting together the Pumpkin preamp with dual mono shunt supplies   Should be a fun project, but so far assembling all the parts is a major challenge and it's more expensive than you might think without a rich parts bin to draw from.

Congrats on building your F4 amps! I hope you're still finding them as enjoyable as ever. I know this is an old thread but as you're so experienced with operating the F4 as a balanced mono block I hope you can advise me.

I want to use my stock F4 in balanced mono mode to drive a ~ 90db SPL/w/m center channel speaker. As the F4 does 100 watts, my room's only ~ 2800 cu ft and I'd be only 13 ft away how much input signal voltage could the F4 really need, even to sound it's best under these conditions?

That's why I wanted to know if you or someone you know has ever put a balanced passive preamp between the F4 and a balanced output source-like a multichannel DAC, which will have a ~ 4.6V output. Would there any loss in sound quality using a passive preamp like these, assuming their balanced stereo passive outputs could be bridged to feed the F4's balanced input?  https://khozmo.com/product-category/preamplifiers/

[TomS]

Congrats on building your F4 amps! I hope you're still finding them as enjoyable as ever. I know this is an old thread but as you're so experienced with operating the F4 as a balanced mono block I hope you can advise me.

I want to use my stock F4 in balanced mono mode to drive a ~ 90db SPL/w/m center channel speaker. As the F4 does 100 watts, my room's only ~ 2800 cu ft and I'd be only 13 ft away how much input signal voltage could the F4 really need, even to sound it's best under these conditions?

That's why I wanted to know if you or someone you know has ever put a balanced passive preamp between the F4 and a balanced output source-like a multichannel DAC, which will have a ~ 4.6V output. Would there any loss in sound quality using a passive preamp like these, assuming their balanced stereo passive outputs could be bridged to feed the F4's balanced input?  https://khozmo.com/product-category/preamplifiers/

Wow, it's been 15 years ...

The F4 has no voltage gain, so whatever your preamp has in terms of voltage swing is what you get. I doubt 4 volts is enough. My preamps had ~15-20 volts. Study page 2 of the manual for better answers. It's a great amp in the right situation, so best of luck https://www.firstwatt.com/wp-content/uploads/2023/08/prod_f4_man.pdf