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Old 12th April 2010, 09:54 AM   #7701
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Quote:
Originally Posted by kp93300 View Post
I suggest bypass of the power supply caps.
regards
kp93300
I thought this is the key too... Now the last cap is small siemens sikorel,but i think good MKP should have positive influence,as i know allready, with these a-class transistor amps ANY mod in PSU are noticable.
I really hope that F5 can give suzuki superbike like performance with my titan dioxide tweeters,more "being there" felling.Now it's just amp that dont involve me much in the music.With harsh cd,speakers,maybe it would be very good.
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Old 12th April 2010, 10:47 AM   #7702
tinitus is offline tinitus  Europe
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Quote:
Originally Posted by jackies View Post
Those heatsinks are commonly used, you'd need 4 of these I reckon.
Yes, I guess one pr device would work
But they dont seem very practical to use, with tricky mounting

HEATSINK ALUMINUM EXTRUSION 10.08 WIDE 1-12" PC. - eBay (item 170471042670 end time Apr-17-10 05:06:27 PDT)
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Old 12th April 2010, 12:52 PM   #7703
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Quote:
Originally Posted by markofka View Post
Hi there,
Just built my first F5,standart PCB but with toshiba sk1530,sj201 transistors. 8x47000 caps,24V-1.1A.
First impression it's too smooth,like diy member Bear mentioned in "F5 listening" impressions" thread. But didn't find solution to solve this out.
Amps is very stable,with wide soundtage,great detail but too smooth at the top end,no simbiliance at all.
What could i do to improve resolution performance?
1.Bypass big electolytic caps with MKP?
2.Increase current to 1.3A?
3.Change Tosh's to IRFP's? (Teabag said tosh's smooth things)
4.Burn in amp ,since it's working only two hours or so?
5.Change resistors at PCB, meaning i have Toshiba instead IRFP?

Thanks
There is no sibilance? that's good, not bad, unless you can measure a rolloff at HF....

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Old 12th April 2010, 12:57 PM   #7704
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Quote:
Originally Posted by etoiledusoir View Post
Hi everybody,

I'm in the first step to build a f5. I know that a lot of question have been made concerning heatsink. But I found some surplus stock of heatsink made for power rectifier on the web and I really don't know if they are ok for the project. The dimension is 6 1/4" X 6 1/4" X 9" Long.

Aluminum Heat Sink 6 1/4" X 6 1/4" X 9" Long. - eBay (item 7607693627 end time Apr-15-10 09:31:06 PDT)
Personally, I would not use these heatsinks because you will need a considerable distance between the PCB and the mosfets... the flat back with fins type extrusion is much easier to use with this type of amp.

There may be tricks to be able to make a flat attachment to the type of heatsink you showed, but they're not worth the effort, nor the machining especially for used ones with holes in them, or unless you have some cosmic styling aesthetic.

There are flat backed ones on ebay, someone mentioned the vendor earlier in this thread, iirc.

_-_-bear



Quote:
I plan to make a vertical amp, the trafo and psu on the bottom and the heatsink on top with two channel pcb on the same surface. Is this heatsink fit for the job ?
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Old 12th April 2010, 01:03 PM   #7705
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Quote:
Originally Posted by jackies View Post
Those heatsinks are commonly used, you'd need 4 of these I reckon.
The flat back heatsinks make a good base for the PCB.

The only problem i had was because the ehatsink had fins on the other side was I had to tap all the holes for the output transistors and pcb.
Of course I missed a bit of swarf and punctured one of the insulators !
Luckily I checked with a meter first before powering it up.

It was my first time using a tap and of course I broke two before looking up that you need cutting oil for them to work OK.
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Old 12th April 2010, 01:34 PM   #7706
cjkpkg is offline cjkpkg  United States
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Quote:
Originally Posted by nigelwright7557 View Post
It was my first time using a tap and of course I broke two before looking up that you need cutting oil for them to work OK.
LOL...I had no cutting oil when I tapped mine...ended up using extra virgin olive oil...worked great!
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Old 12th April 2010, 02:01 PM   #7707
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Quote:
Originally Posted by bear View Post
There is no sibilance? that's good, not bad, unless you can measure a rolloff at HF....

_-_-bear
It's not good when there are too much or too little simbliliance But in some recordindgs it must be.Now i have a feeling of some kind of rollof,but there isn't, when different amp is connected Vocals ,instruments arent "very" sharp.
Ok i try do not bother with my subjective opinion,will bypass psu,some other upgrades and write my final subjective decision some day
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Old 12th April 2010, 03:13 PM   #7708
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we have a separate thread for listening impressions and discussions, fwiw... but most folks equate "sibilance" or similar effects with "highs"... I prefer to compare to natural sound, which tends to not have the same sort of "electronic" or mechanical sounding effect.

Otoh, I have heard the F5 vary all over the map in terms of "sound" depending on all sorts of rather minor seeming things. So, wazzup wit dat?

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Old 12th April 2010, 09:25 PM   #7709
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Quote:
Just built my first F5,standard PCB but with toshiba sk1530,sj201
Markofka, can you you tell us more about your build? You used standard R values from NP's schematic? Jfet's are 2sk170/2sj74?

I may be wrong, but you are the first to post about a build of the F5 using the Toshiba outputs in a stock (original NP F5 schematic) configuration.
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Old 12th April 2010, 09:31 PM   #7710
amp_guy is offline amp_guy  United States
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Quote:
Originally Posted by cjkpkg View Post
LOL...I had no cutting oil when I tapped mine...ended up using extra virgin olive oil...worked great!
The absolute best lube for tapping aluminum I have ever used is Anchorlube
You won't believe how easy the tap goes through, first time you use it you will wonder if you drilled the hole too big.
And someone is selling it on E-bay so it is easy to get.

eBay.com.sg: ANCHORLUBE TAP CUTTING FLUID G-771 ECOFRIENDLY 4 FL OZ (item 220540873893 end time Apr 06, 2010 00:38:57 SGT)
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