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Old 3rd February 2009, 10:45 PM   #2671
massimo is offline massimo  Italy
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It doesn't make sense. In that position an inductive resistor is probably better than a n.i. one. Think about CLC.....
If you get a slight lower voltage, this is most probably due to the Vf of the diode bridge and/or the pw xfrmr regulation.
Just my 2c
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Old 3rd February 2009, 10:47 PM   #2672
tms0425 is offline tms0425  United States
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I believe mine runs a little under 23v under load with 4x0.47r in the CRC and a generic bridge.
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Old 3rd February 2009, 10:48 PM   #2673
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Quote:
Originally posted by massimo
It doesn't make sense. In that position an inductive resistor is probably better than a n.i. one. Think about CLC.....
If you get a slight lower voltage, this is most probably due to the Vf of the diode bridge and/or the pw xfrmr regulation.
Just my 2c

Thanks Massimo, The voltage worries me less than if the performance might go all wrong (or a wee bit) at a sonic level. Easy enough to change.
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Old 3rd February 2009, 10:53 PM   #2674
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With a single 2 x 18V transformer I'm getting +/-23V , with 20V transforer, it is 27V
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Old 3rd February 2009, 10:54 PM   #2675
massimo is offline massimo  Italy
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Don't worry, listen to music and enjoy your nice amp!
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Old 3rd February 2009, 11:21 PM   #2676
udailey is offline udailey  United States
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Fran,
Freakin nice job. That looks beautiful.
Uriah
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purchase LDRs anytime Also try my Resistor Replacers or LDR based Input Selector Email me. diyldr@gmail.com
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Old 3rd February 2009, 11:22 PM   #2677
ichiban is offline ichiban  United States
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Default Re: Re: Re: Re: Finished my F5 --- tms0425

Quote:
Originally posted by woodturner-fran
Nice looking box there ichiban.
Fran
Thanks, but all it is so far is a left over sheet of aluminum that is 12 inches wide and when the excess length is trimmed off will fit the back perfectly Your amp looks verrry nice. A wood front from a very old oak table leaf extension is what I'm considering, offset from the sinks.
Quote:
Originally posted by tms0425

I wish I had some of those nice milled and drilled Conrads. Very nice
Instead of tapping the heatsinks for all of them right away, I would be inclined to use flat bar stock temporarily clamped over the pairs of Mosfets. If it won't work that way in free air, the closed case with toroids inside definitely wouldn't make it.
Thanks for the reply. Yeah, the Conrads are nice. Should have ordered four from cwujek's group buy. He's considering another.
That's exactly what I was considering, clamping first. Thank you for the reply.

Quote:
Originally posted by Nelson Pass

Just adjust the bias until the sinks run 50-55 deg C, and there you are.
Sounds like a plan, oh great one Ah, em, cough, cough. Hoping for a balanced F5 in the F6-7-8 !¿ Big Grin
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Old 3rd February 2009, 11:43 PM   #2678
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Thanks guys. funny you should mention that old oak.... thats exactly what this was. It was a board from the kitchen table in the house I was born in, since derelict and so has senimental attachment too. Can tell you though, it was a bitch to plane. Whatever crud got into it over the years (the open grain is actually black) I wore a set of planer blades to blunt bringing just a few boards back to true. Nice to have it though.

Some details, I'm using a 12" x 6" x 2" heatsink per side and it gets good and hot, at least 50 deg each side I reckon. I can hold my hands for 10 secs ok, but it gets uncomforable after that. My DMM with temp probe is outside in the workshop, will get an accurate measurement tomorrow night. But right now, you need that size of heatsink for sure. I'll be checking bias again tomorrow night to be sure to see how it settles out.

Sonics: well I've only had a short listen, couple of albums, but initially, the sound seems very refined. My initial impression is that it has the best qualities of both my EL84 amp and the mini aleph. Has a really nice airiness to the highs. Seems to be a little lower gain than the mini-aleph too, I seem to have the volume knob up a little more on the pre. Bearing in mind this amp has not been running for more than 2 hours, it sounds very good - well worth the build and I do think it improves on the mini-aleph. Maybe its just the extra power of course (mini was 10wpc) but there is a lovely kind of unforced nature to the sound. Need to try it out on some dynamic speakers too (mine are quad 57s).


Thanks to all.....

Fran
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Old 4th February 2009, 12:26 AM   #2679
ichiban is offline ichiban  United States
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Default that old oak...

Quote:
Originally posted by woodturner-fran
Thanks guys. funny you should mention that old oak.... thats exactly what this was. It was a board from the kitchen table in the house I was born in, since derelict and so has senimental attachment too.
Sonics: My initial impression is that it has the best qualities of both my EL84 amp and the mini aleph. Has a really nice airiness to the highs. Seems to be a little lower gain than the mini-aleph too,Fran
My piece of oak is from my paternal grandmothers table. Hoping to just remove some aging, giving it a rustic look.
I have an old Akai reel2reel tape recorder, bought in 1967 at the Webb TX. AFB px, that has EL84s
used single ended. It has a very fine high end. Only 5 beautiful watts .
So, if the F5 has its qualities at a higher power, I will be in heaven.
I've read somewhere that the F5 will need a pre-amp with extra gain.
Guess I'll use my HarmonKardon 1 for awhile.
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Old 4th February 2009, 07:57 PM   #2680
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A question for those running without current control/ temp compensation....


Have you tracked voltage across R11 and 12 with case temp? I'm finding that voltage can rise by about 0.6-0.7V when my case is closed. Is this ok? R11/12 get to about 60 deg C.

Heatsinks are getting to 45-50 deg C


I have some imbalance between Q3 and 4 on one channel. What I think is wrong is that R11 and 12 on this channel got a roasting so maybe have drifted. If the resistance has drifted that would cause it right? This leads to higher offset naturally, but will it affect the sound?


Thanks,

Fran


EDIT: I'm thinking strongly of reconnecting the thermistors and then also R15 IIRC. Might leave things a little more stable.
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