F6 Illustrated Build Guide

Jump to Latest
#1,821
Korg as F6 Preamp

So while gearing up to start on my F6 I decided to go ahead and order one of the DIY Store B1 Korg kits. As I keep reading and listening to Nelson I see that the F6 is buffered and in Nelson's talk he talked about the 2nd order harmonic characteristics of the F6.

It sounds like I am duplicating the benefits of each design?

Am I creating a monster by combining the B1 Korg and F6 with too much buffering and too many harmonics? Will there be enough Gain?

I have efficient speakers and I currently have tha Amp Camp dual mono blocks with an ancient Hafler preamp
 
#1,826
I have ordered a bunch of parts for my first First Watt F6 amp last week. Super excited but can’t find the Jensen JT-123-FLPCH trafos anywhere. Jensen are not answering. Perhaps they are inundated.

Does anyone know where I can buy these? Alternative suppliers I have found showing no stock.

Or is there an alternative with the same specs available on the market?

Thanks
 
#1,829
jqmce said:
I have ordered a bunch of parts for my first First Watt F6 amp last week. Super excited but can’t find the Jensen JT-123-FLPCH trafos anywhere. Jensen are not answering. Perhaps they are inundated.

Does anyone know where I can buy these? Alternative suppliers I have found showing no stock.

Or is there an alternative with the same specs available on the market?

Thanks
Click to expand...

Try email. I emailed them two weeks ago for a quote and they got back to me the next day. I forwarded payment via PayPal and the transformers shipped the same day.

Finished my amp last night and enjoying wonderful music!
 
#1,830
WKCox said:
Try email. I emailed them two weeks ago for a quote and they got back to me the next day. I forwarded payment via PayPal and the transformers shipped the same day.

Finished my amp last night and enjoying wonderful music!
Click to expand...

Same here - I emailed them and got TWO emails back immediately with a fill-in-the-blanks PDF order form and instructions. I think these transformers are pretty much stock items.
 
#1,833
The JT-123-FLPCH is a quadfilar transformer, meaning it’s 4 wires wrapped around the core all at the same time. It’s 1:1 by physical winding but depending on series or parallel connections can be wired into different ratios.
 
#1,835
JimM said:
My F6 build, ordered F6 kit on 12-12 and received the boards and transformer on 12-19. I converted my BA-2 build to the F6, so chassis and power supply were already available. My BA-2 used + - 50 volt rails so wired the antek for 240 volt and got the +- 25 volt rails.
The following are the results of the F-6 build.
let cook for 4 hours biased the amps at 0.610v with offset of 2 to 3 mv FETS got up to 50 c.
Testing with meters, signal generator, and Scope.
Left channel
Bias (cold) 0.493v
Offset (cold) 28.4mv
Right channel
Bias (cold) 0.51v
Offset (cold) 25.4mv
At 30 minuets
Left
Bias 0.595v
Offset 3.8mv
Right
Bias 0.592v
Offset 1.7mv
At 1 hour
Left
Bias 0.617v
Offset 6.2mv
Right
Bias 0.619v
Offset 2mv
Power supplies at full bias +- 22.2v
No load clipping 41.2 v peak to peak
Measurements with 4 ohm load, voltages are peak to peak from scope at 1KHz.
Left channel
Input Output Bias
0.29v 1.37v 0.606
2.84v 13.45v 0.618
5.66v 26.15v 0.67
Right channel
Input Output bias
0.286v 1.43v 0.605
2.84v 13.7v 0.615
5.65v 27.15v 0.67
At soft clipping top of sine wave just starting to change shape.
6.5-7.6v 34-36v 0.8+ Left
6.5-7.6v 34-36v 0.8+ Right
Let smoke out of right channel 0.47 ohm resistor. All measurement with one channel driven. Measured current on one channel with meter 10 to 12 amps at soft clipping.
Comments: First impression with DIY speakers very good detailed sound whereas BA-2 was a softer presentation. Will install on big speakers ( Maggie 1.7 and Tannoy DC10A) to get a better handle on sound.
The preamp will need to output around 4 to 5 volt RMS to achieve full output from the amp at current gain setting, which may be a problem for some pre’s. Also if you are going to drive 4 ohm or lower loads at close to full output then need to parallel the bias resistors to get 6 watt or higher wattage. May be a good fit for Caddock resistors (May try to order some to try out).
Click to expand...
Please how do I setup the bias for buchardt s400 which is 4 Ohms speakers?
 
#1,836
qafro - I'm not sure why you quoted that entire post. Any context?

Is your amp already up and running using the values in post #1? Are you not happy with the way it sounds with those speakers? Issues?

Was it the last lines of the post you quoted that made you ask re: full power into a 4 ohm load?
 
#1,838
Remote MOSFET: loaded question.
Wat are the implications for remote mounting Mosfets? Say 10 - 15 cm between PCB and mosfets with wire running between?
What are the risks?
I have a concept in my head for a wall mount First Watt F6 (F6 wall art or as I like to call it “FART 6” ) with remote power supply but need to know if mounting them will be detrimental.
Yep I will still have a very large custom machined heatsink involved.
 
#1,840
jqmce said:
Remote MOSFET: loaded question.

Wat are the implications for remote mounting Mosfets? Say 10 - 15 cm between PCB and mosfets with wire running between?

What are the risks?

I have a concept in my head for a wall mount First Watt F6 (F6 wall art or as I like to call it “FART 6” ) with remote power supply but need to know if mounting them will be detrimental.

Yep I will still have a very large custom machined heatsink involved.
Click to expand...
I was ready to ask this as well. I believe there's a post earlier in the thread about which wires should be twisted and which should be separate.

I want to use CPU heatsinks for my monoblocks; remote mounting the mosfets would make it way easier.
 
You must log in or register to reply here.
Top Bottom