F5 power amplifier

[westend]

Originally Posted by alazira

Hi,
Set the bias pots to zero. On CVillers' board he has legs 2&3 together which means you turn completely counter clockwise to zero it. On Peter Daniel's board he has pins 1&2 together which means you start with the pot turned completely clockwise and bias it by turning it counter-clockwise.

This was my understanding, also, regarding the trim pots, until I fired the amp for the first time. I am using C Villers boards and the Bourns 5K trimpots. If the trimmers are turned counter-clockwise, full current will be delivered to the circuit. The trimmers must be turned clockwise to zero the current You can read the gory details Here. Fortunately, my components survived this misstep and the amp is settling in well.

[Beftus]

You must have skipped this bit in the F5 manual:
Before applying power to the amplifier, you will want to set the values of P1 and P2 to their minimum. Verify this with an ohmmeter.

[alazira]

Originally Posted by Russellc

Is it running yet? Thanks for the post.

russellc

I had it running for a few days before the discussion of R1&R2 wattage ratings came up. Initially I thought I had .33w resistors there and had played it at volume so was surprised that they didn't fail. However, I rechecked and they are actually 1watt HOLCO resistors.

It's a PTP that I used for practice before I use my "better" caddock parts, and to see if I needed R9. So for those here with a Lightspeed Attenuator and F5 (I see quite a few here who frequent both threads), you can probably make it without R9. Just one less resistor in the pathway



Not terribly elegant looking. None of my stuff turns out that way. More like a caveman put it together I have PD's boards and may use them as I built it to be interchangable with his formfactor.



I thought why not make everything point-to-point, even the bridge diode.

[tinitus]

Originally Posted by alazira

So for those here with a Lightspeed Attenuator and F5 (I see quite a few here who frequent both threads), you can probably make it without R9. Just one less resistor in the pathway

According to F5 manual R9/10 are fore safety reasons to minimize any problems with parasitic problems from a connected source
You know that too, Im sure

But Im not sure its safe to be that categorical regarding the Lightspeed
I suppose it would very much depend on the individual build and setup
Or maybe even the signal source before the preamp

btw, I got my Jfets today

[alazira]

Originally Posted by westend

This was my understanding, also, regarding the trim pots, until I fired the amp for the first time. I am using C Villers boards and the Bourns 5K trimpots. If the trimmers are turned counter-clockwise, full current will be delivered to the circuit. The trimmers must be turned clockwise to zero the current You can read the gory details Here. Fortunately, my components survived this misstep and the amp is settling in well.

Hi,
Here I have pins 2&3 shorted, turned completely clockwise.



Maybe I'm remembering incorrectly. I'll check when I get home from work.

[alazira]

Originally Posted by tinitus

According to F5 manual R9/10 are fore safety reasons to minimize any problems with parasitic problems from a connected source
You know that too, Im sure

But Im not sure its safe to be that categorical regarding the Lightspeed
I suppose it would very much depend on the individual build and setup
Or maybe even the signal source before the preamp

Hi,
I didn't know R9 if for safety. If it is I'll put it in the final build.
You're right about differing systems, so that's why I used the politicians "probably", but should have been more clear. I'm using a simple setup of CD player - LSA - F5.

[Russellc]

Originally Posted by Beftus

You must have skipped this bit in the F5 manual:
Before applying power to the amplifier, you will want to set the values of P1 and P2 to their minimum. Verify this with an ohmmeter.

How is this done in circuit? (I've already soldered them in place.)

Russellc

[Tea-Bag]

alazaria,
cool looking p2p build. It looks like a diyselfer built it.
As long as it didn't catch fire, good listening!

[Russellc]

Originally Posted by alazira

Hi,
Here I have pins 2&3 shorted, turned completely clockwise.



Maybe I'm remembering incorrectly. I'll check when I get home from work.

As I have the Daniels boards, I am waiting for your response!

Russellc

[tinitus]

Right, I just checked, to be sure
R9 is precaution against the parasitics
R10 is safety reference grounding, when no signal connected

My humble guess about R9 is that it may sound ok without R9, and you may still have some oscillation or whatever without knowing, until it some day goes down without any warning
I wouldnt mess with those
Just a guess

Heavy looking amp your building