Aleph amp questions

[Bksabath]

So start with 200 or what ever for R5 and R7
200 200 and 150 =60
200 200 and 300 =75
200 200 and 566 =85

Best way realy is to put the formula in excell but not a clue on how to stick this here.

Me think that if he can rig a multipole switch he can then try different values on the fly
once happy just solder the proper resistor value in.

 

[Melon Head]

So start with 200 or what ever for R5 and R7
200 200 and 150 =60
200 200 and 300 =75
200 200 and 566 =85

Best way realy is to put the formula in excell but not a clue on how to stick this here.

Me think that if he can rig a multipole switch he can then try different values on the fly
once happy just solder the proper resistor value in.

The only thing I would change here is that you won't here much difference betwwen 60, 75 and 85.
75, 100, and 150 will be better, or possibly 100, 150, and 200.

 

[Russellc]

This approach seems much lighter touch than what I read in F-5 thread.
Nelson's recomendations were seen on post #3731 in the F-5 thread, but was way more extensive, some commenting that "It wasnt subtle."

"Increase value of source resistors to 1 0hms, and increase value of feedback resistors from 2 x 100 ohm and 10 ohms to 1 x 100 and 22 ohms."

Seems to me, (who knows nothing) your guys more gentle bumping of the feed back resistors only may be more "subtle" and likely what I need.

Thanks guys, your ideas are much appreciated!

Russellc

 

[Russellc]

besides fun -that's main goal

just ask ....... as you said - better to ask than sorry

But if sorry, it should "catch on fire at least" right?

Russellc

 

[Russellc]

http://rocky.digikey.com/weblib/Ohmite/Web photos/RES SERIES.jpg

Well, at least it looks plenty substantial! Giant pot on tiny Peter Daniels board.

russellc

 

[Russellc]

exactly - word by word

start with 150 instead of 100 and listen

All 4 resistors to 150? Or just two? ( R5 and R8)

Thanks again for this help. I'm preparing for a no current limiting version with Toshiba mosfets, and I think a giant single transformer this time, 600-800 VA, instead of the dual mono with 2 300VA units. (Antek)

Many thanks,

Russellc

 

[Zen Mod]

start increasing values of (R5//R7) and (R6//R8) groups

now each group have value of 50 ohms

increase value of both groups to , say, 65 ohms ; that will be 100R//180R

 

[Bksabath]

Hi Russel

You are looking at the ratios of R5 in Parallel with R7 feeding R1 on one side
and R6 R8 feeding R2 on the other

Whatever you do you must keep the to sides equal for clarity lets call parallel of R5 and R7 R Feedback top and R6 and R8 Rfeedbackbotom

If you change Rf-Top you must change Rf-Bottom by exactly the same amount.

If you can keep the final values exactly the same this should not effect the balance of the circuit which other vise spoils the result of a listening session .

More than welcome mate actually tanks to you as I am going trough the same process and this would have been one of my questions eventually.

On transformers I went for 2 1000VA with 24V and a tap at 20V
this would give me same flexibility as I will try different builds
The F5 should drive my Polk's but "I don't want to do 55 Mph with the pedal on the floor"
(nougty nougty noughty Litle Alex was doing 137 caming back home this morning)
Tanks Thanh1973 I will try those 75 100 150 and 200

Russel you OK with the math side?

I made a excel table but I got not a clue on how to place it here.

Al

 

[Russellc]

Ok, I believe I see whats going on. Thanks for taking the time guys, much appreciated.

Now I find I have four Daniels F5 boards and my mind is thinking about X version, Whoa now the horse beating begins in earnest!

I need to order some resistors and get this feedback thing sorted out to my taste. Should be interesting to see a little more gain.

Russellc