How to build the F5

[geraldfryjr]

I have been contemplating such a design but everyone here frowns on using off line supply's. jer

 

[AndrewT]

Isn't each output device biased to 1.3A? Doesn't that mean that you are drawing more than 5.2A from the transformer?
In the F5 manual the amp as per Firstwatt a stereo F5 pulls about 180W from the wall, so for fun lets assume that the transformer has to provide about 160VA with a 1.3A bias per output device due to losses and such. That means you are drawing around 9A from the transformer at stock bias.

Lerg,
there's something seriously wrong with your numbers !

 

[kannan_s]

Here are the photos of the initial powerup and the final tweaking/tuning.
...
And as NP said, "...And there you have it!!"



Oh, the Hiaku -

Building the F5
In solder fumes I smile
heat and balance sings


Or, if you are into 3-5-3

Pass amps are
in their special way
his and mine

Hi where did you buy your heatsinks ?
thanks
kannan

 

[merlin2069er]

6L6, Jim (and Woody, etc)......

I dug a litte deeper into Antek's published specs for there 18-0-18 VAC torroid core transformer families. All data I used is from the Antek website. I've plotted the data in the attached. The info for the smaller transformers (100, 200, 300 VA) is mostly FYI. Please note that for each VA model I've plotted the three data points in the Antek specs, except for the 500 VA model, where the third data point (for the most heavy current load) was clearly erroneous.

Some interesting observations. The 500 VA model, based upon Antek's own data, is not a strong candidate for the F5, considering it's cave-in under loads; a little surprising for a claimed 500 VA model. Note that the Antek data suggests the 400 VA and 600 VA models are ALMOST IDENTICAL in VAC/current specs, to include voltage sag under load, up through the "expected" operational range for a straight-forward F5. (I'm certain some will chose to debate what "expected" operational range ought to be, but I'm considing that to be about 10 amps/rail, and close to the stated 18 VAC secondary. For those who want to debate, please feel free to start a new thread).

Also note the "blue dot", at about 18 VAC and ~3 Amps--that's where my curent 400VA transformer is working......pretty far below the Antek data for that model.

In any case, enjoy. All, FYI..... Again, all the "hard data" is from Antek itself. I'd be interested in others' thoughts........

Ken

Should I replace my antek 4218?

 

[Russellc]

Well, the 600va is fine. I am quite lucky that I bought one that was "too big". No worries, no wondering if it's going to work. It's quiet, it's cool.

I'm sure the 500VA will also work, I've recently bought one and will be reporting any problems. Inasmuch as several have built with them using the 300VA for a stereo amp without problems, (and, while there is a lot I dont understand here), I dont see how the 500VA is less than a candidate for the
300VA model would be.

I should say outright that my only experience with Antek is the dual 300VA units in my F-5, which are hum/buzz free and have done a fantastic job as far as I can tell. (with no way to really measure its performance).

I think the original F-5 uses a single 250VA? Trying to find where I got this info as we speak, I thought it was the F-5 article on the Firstwatt site.

Would be nice to see them and a few others measured in a similar fashion, so we could see how they perform.

Russellc

 

[Russellc]

Should I replace my antek 4218?

Are you having any problems with it? Is it making noise? Does it get way too hot? If not you likely have not a thing to worry about. I'm doing a build right now with the suspect 500VA model. I have every confidence in it. That said, I will find out. The Antek stuff has been widely used and I'm not aware of any problems here or elswhere, but there sure could be.

They are, by a good margin priced lower than most of the competition, I'm willing to admit their could be quality differences between these Anteks and Plitron or Avel-Lindberg as well.

I dont have a lot of testing equipment, but would help with any testing anyone would like performed on this unit.

It would be nice to have the folks at Antek weigh in, bit oh well.

I will report back any failings of this unit as used with F-5.

Russellc

 

[MagnumOpus]

Courtesy of Decibel Dungeon -

Use a incandescent lightbulb, obviously...

Thanks

 

[merlin2069er]

Are you having any problems with it? Is it making noise? Does it get way too hot? If not you likely have not a thing to worry about. I'm doing a build right now with the suspect 500VA model. I have every confidence in it. That said, I will find out. The Antek stuff has been widely used and I'm not aware of any problems here or elswhere, but there sure could be.

They are, by a good margin priced lower than most of the competition, I'm willing to admit their could be quality differences between these Anteks and Plitron or Avel-Lindberg as well.

I dont have a lot of testing equipment, but would help with any testing anyone would like performed on this unit.

It would be nice to have the folks at Antek weigh in, bit oh well.

I will report back any failings of this unit as used with F-5.

Russellc

I'm still in the process of putting it together.

 

[sts9fan]

I have built a point to point PS for my F5. I have two large 68000uF caps on each rail in a CRC. I cannot find anything wrong but I keep blowing fuses with no load on the PS. Is it possible that even witht he CL60 the inrush is too much? I had fast blows so I ordered some slow blows. I had an EE check my work and he said everything looked fine but could be inrush and suspected at steady state things should be fine.
Can I add thermisters to the rails? How can I test this hypothesis? My Transformer is a Antek 300VA.

Kris

 

[CanAm Man]

Should I replace my antek 4218?

Good question. I'll be talking to Antec about my 400VA model......

In any/all cases, I found their tech data to be very interesting.......!

Probably the best is to listen to the amp, and see if you like what you hear. (Of course, without an identical amp with a bigger VA transformer, it will be a "one-deep blind test".....)

 

[Zen Mod]

I have built a point to point PS for my F5.......

Kris

try with bulb in series - measure voltages at caps

 

[6L6]

I cannot find anything wrong but I keep blowing fuses with no load on the PS.

Are you absolutely sure you have the transformer primaries wired correctly? That will pop a fuse every time...

 

[sts9fan]

pretty sure. It does not pop until I reach 40VAC with my variac. Plus like I said I had someone check it out. Without the returns connected together on the last caps I get 24V across each cap.

 

[6L6]

Hmmm... Interesting.

Can you post some photos? That would help immensely.

 

[sts9fan]

I will post some when I get home. I am gonna try the light buld also.

 

[Andersonix]

Sts9fan: What value of fast blow fuse are you popping? (I remember most of NP's PS diagrams showing a slow-blow fuse.)

 

[6L6]

Adding thermistors is fairly easy and part of the final design, you might as well do it now and see what happens.

Also, the slo-blo fuses might alleviate your problem. But if you are turning things up slowly on a variac, that probably will not help.

 

[sts9fan]

I have blown up to 6A fast blow. Also I do have the thermistors on the mains. I was thinking of adding some to the rails.

 

[6L6]

That's weird.

Post pictures. (Yes, I know you said you would... just reiterating!)

 

[Andersonix]

Can you confirm: So even with a Variac ("temporary soft-start") and CL-60s on both primary legs, you are still blowing the 6A FB fuse at +/-24VDC voltage on the >unloaded< PS?