Playing in the Sandbox

[mcandmar]

The F4 is a current amp only -- no voltage gain. Rule of thumb is that you need a preamp of 12-15 dB gain. That's a bit much for the bh preamps. The Aleph J is a much better amp than the F5 and is one of Nelson's personal favorites of all his designs. This is typically the amp that people who like SET/tube amps go to because of it's predominant second order distortion characteristic, and will work fine with BH preamps. I believe it is also easier to build than the F5, but I'm not sure about that.

The F4 is the amp to use if you have a SET amp and speakers that need more juice and you don't want to sacrifice your SET sonics. Also a great amp in it's own right.

-- Jim

Thanks Jim that's good to know, i was looking at the various boards and wondering the pros/cons were between them.   The transparency of the F4 is what really caught my interest, i like the idea of using a tube amp with the F4 as an output stage to provide the power, i.e. the best of both worlds.

[debk]

The Smash will have an upgrade package that should push the gain into that region.

-PB

That is interesting to know.  While it worked with the SET amp driving it, I still like the SET amp better alone.  Maybe I just like the purity of it.
I am looking at a preamp to drive the F4's with.  Maybe I will consider getting a smash with the C4S upgrade when it is available.  I am also looking at the pumkin preamp, a SS preamp designed for driving the F4.

I really have way more amps than I know what do with 

Debra

[bjorgens]

similar to DebK, I built an F4 (only one in my case however)... Just finished said build and with limited listening time, I can say it seems pretty transparent running behind my paramounts.  More experimentation ahead, but if nothing else, it was fun to build while waiting for the BH DAC.

Bryan

[debk]

Nice build!

Deb

[mcandmar]

Just curious how you two are getting on with the F4, and what amps you have running infront of it?

I'm seriously considering building one but i need to work out what i need to put in front of it.  A preamp like the Smash or Beepre, or a regular amp like the S.E.X. or Paramounts. Decisions decisions.

[debk]

Mcandmar

Mine are sitting gathering dust at the moment.  I hope to build a preamp to drive them with this winter.  I have most of ht eparts to build a Pumpkin preamp
I drove them with my 2a3 Paramounts, while it wokred with no problem, I really like the sound of my SR45/ BeePree combo the better.
As time permits I will play more with it.

Slan
Deb

[2wo]

Have you tried the F4 with the BeePre? That might be interesting. I have an F5 which sounds OK when I need some more power. Pretty much the only SS amp I have been able to stand for any length of time. The SR-45 is hard to beat...John 

[mcandmar]

Ok stupid question time. What is the SR-45?  I tried googling it and get a lot of hits for a Marantz amp which i assume is not what you are talking about?

[Natural Sound]

Ok stupid question time. What is the SR-45?  I tried googling it and get a lot of hits for a Marantz amp which i assume is not what you are talking about?

Shunt Regulated 45.

[mcandmar]

Gotcha, i've seen talk about BH working on a 45 amp, i assume a replacement for the Paramours?

I've gone ahead and ordered the F4, power supply, speaker protect, and soft start PCB's.  Currently trying to put together a BOM in Mouser, then order a transformer and case.  Anybody got any words of wisdom i should know about?    .....a decent manual wouldn't go amiss for these, especially for sizing the power supply section as i'm having to scroll through hundreds of pages to pick out bits of information here and there.  Why cant everybody do a kit like Bottlehead

Cheers,

Mark

[debk]

Mark

I didn't use a soft start board in my build.  I think the thermistors do a good enogh job with any inrush current.

I sent you a PM about some parts

Deb

[mcandmar]

Thanks to your inspiration, advice, and parts donation i have finally finished building my own little sandcastle.  It really is everything i hoped it would be, and by that i mean transparent to the point it sounds exactly like whatever you are driving it with.  My speakers are a pair of large inefficient vintage KEFs from the 70's which can fill the house with authority powered by nothing more than a humble little Quickie so volume range is not an issue. 

Vs the 5.1 Pioneer amp i was using before it really is astounding how much better the DAC/Quickie/F4 setup sounds, so smooth yet detailed, i cant wait to build a nice preamp for it now.

I still have plenty of experimentation to do with different sources to work out what gain and voltage levels i need for these speakers to operate in, given how well the Quickie drives the setup it appears they dont need very much at all. I am also really curious to try the S.E.X. amp in front of it so i need to make up a cable to make that happen.  Out of interest have you tried running yours directly from the BeePre?

Thanks again for all your help Deb!

Mark

[debk]

Very nice build!

Deb

[Skip Pack]

If you are using the SEX amp as a preamplifier (which I am) try putting power resistors across the binding posts (I'm using 16 ohm Mills 12 watt resistors). I like the result with a load close to spec paralleling the power amp input. It works without, but it's nicer with.

Skip

[mcandmar]

Interesting, i will give that a try.

Cheers,

Mark