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Old 11th April 2010, 12:10 AM   #7691
kp93300 is offline kp93300  Malaysia
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Default problem solved

I changed R4, R3, R1, R2 , Q1 and Q2.
dc offset now is zero.

I think i fried one of the jfet by static discharge while changing interconnect.
kp93300
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Old 11th April 2010, 04:24 AM   #7692
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Usually it takes quite a zap to damage a Jfet. They don't have
the delicate Gate insulators of Mosfets.

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Old 11th April 2010, 10:28 AM   #7693
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Join Date: Jun 2007
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
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Old 11th April 2010, 05:03 PM   #7694
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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
try to burn in the amp for a good 100 hours.
my aleph 1.7 had the same sound at first.
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Old 11th April 2010, 06:11 PM   #7695
a.wayne is offline a.wayne  United States
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Location: Front Row Center



100 Hrs, that would take a Yr ... LOL...........


Markofka wrote : 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?

So it has detail but need better resolution


Toshiba's or IRFP's ?

.

Last edited by a.wayne; 11th April 2010 at 06:15 PM.
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Old 11th April 2010, 06:41 PM   #7696
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Join Date: Jun 2007
My F5 has quite good detail,but lacks resolution (detail) at the top end. Dont know how to describe better. I have Hiraga's le monstre and le class too and they both performs better,except "bass tightness" area.

Now i rewired my PSU ,increased bias,things got a little better.Will wait for another sugestions while amp is burning in...
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Old 12th April 2010, 12:52 AM   #7697
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Nelson, thank you for your contributions to this community and for sharing your work. I keep reading your articles over and over and I'm starting to get it What is "New Class A"??? I have a Technics amp that is New Class A


Tony
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Old 12th April 2010, 02:18 AM   #7698
kp93300 is offline kp93300  Malaysia
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Join Date: Mar 2007
Quote:
Originally Posted by markofka View Post
My F5 has quite good detail,but lacks resolution (detail) at the top end. Dont know how to describe better. I have Hiraga's le monstre and le class too and they both performs better,except "bass tightness" area.

Now i rewired my PSU ,increased bias,things got a little better.Will wait for another sugestions while amp is burning in...
I suggest bypass of the power supply caps.
regards
kp93300
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Old 12th April 2010, 06:04 AM   #7699
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Join Date: Nov 2009
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)

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, 07:01 AM   #7700
jackies is offline jackies  United States
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Those heatsinks are commonly used, you'd need 4 of these I reckon.
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