Juma's Head Amp

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#282
Hi Prasi,

I'm interested in one stereo HA board, I've added myself to the list:

xrk- 1 set (1 PSU+1 Stereo HA)
gannaji- 1 set (1 PSU+1 Stereo HA)
saheb- 1 set (1 PSU+1 Stereo HA)
kram- 1 set (1 PSU+1 Stereo HA)
btesize-1 set (1 PSU+1 Stereo HA)
rumina-1 set (1 PSU+1 Stereo HA)
nicusim-1 set (1 PSU+1 Stereo HA)
potepuh-1 set (1 PSU+1 Stereo HA)
e_fortier-2 PSU
touchdown -1 Stereo HA

Thanks
Nicola
 
#284
e_fortier said:
Hi Prasi,

Thanks for adding my name for the GB.

I have just calibrated 2 of the board and noticed that when orienting the board the right way, i.e. with the output transistors on the right side, you have to turn P1 and P2 counter clockwise to increase the bias, it's usually more intuitive to turn clockwise to increase bias. Maybe you could rewire P1, P2.

Just my 2 cents.

p.s. Worked right away. Thanks.

BR,
Eric
Click to expand...

Hi Eric,
Great to hear that you had no problems to get your HA working.

what values of R5, R2/R3, R16/18/20 that you are using? the final design that i made uses R5=22k (w/o i/p coupling cap=jumper), R5=100k (with coupling cap=1uF, 5mm pitch), R2/R3=47R, R16/18/20=330R or single 1k res.

Thanks for your suggestion, one could just install the pots opposite to silk.
I did the design as per Juma's original suggestion to start with maximum resistance of pots for least bias and decrease the resistance to set the bias. http://www.diyaudio.com/forums/pass-labs/271926-f5-headamp.html#post4269989
reg
Prasi
 
#286
Just wanted to some opinions regarding signal i/p connector that people prefer to use. the final design uses a 2.54mm pitch 2 pin header. i have tried possibility of jst / screw termi block, but seems difficult, as i had to accommodate 1uf coupling cap.

x, i know you prefer termi blocks😉...
 

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#288
I like the Molex connectors too. The location at present would put it right against the amp front panel. I don't know how to bring it farther back away from panel to allow easier access when installing or removing plug from PCB. The PCB is now attached to front panel by virtue of pot soldered on. Getting the pot and heatsink holes for mosfets to line up may be tricky.
 
#291
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#292
Hi Prasi,

I've added myself to the list:

xrk- 1 set (1 PSU+1 Stereo HA)
gannaji- 1 set (1 PSU+1 Stereo HA)
saheb- 1 set (1 PSU+1 Stereo HA)
kram- 1 set (1 PSU+1 Stereo HA)
btesize-1 set (1 PSU+1 Stereo HA)
rumina-1 set (1 PSU+1 Stereo HA)
nicusim-1 set (1 PSU+1 Stereo HA)
potepuh-1 set (1 PSU+1 Stereo HA)
e_fortier-2 PSU
touchdown -1 Stereo HA
albertNL- 1 set (1 PSU+1 Stereo HA)

Thanks
Albert
 
#294
prasi said:
Hi Eric,
Great to hear that you had no problems to get your HA working.

what values of R5, R2/R3, R16/18/20 that you are using? the final design that i made uses R5=22k (w/o i/p coupling cap=jumper), R5=100k (with coupling cap=1uF, 5mm pitch), R2/R3=47R, R16/18/20=330R or single 1k res.

Thanks for your suggestion, one could just install the pots opposite to silk.
I did the design as per Juma's original suggestion to start with maximum resistance of pots for least bias and decrease the resistance to set the bias. http://www.diyaudio.com/forums/pass-labs/271926-f5-headamp.html#post4269989
reg
Prasi
Click to expand...

Hi Prasi,

I only adjusted the bias at 150mA with 0mV DC offset, I did not yet installed an input cap (2.2uF) so I've no clue how it sounds. Working now on the PSU since the heatsinks seems a bit too small.

For the input connector, see what I've used, fits nicely and has screws. X will like 😉

http://www.digikey.com/product-detail/en/on-shore-technology-inc/OSTVN02A150/ED10561-ND/1588862

BR,
Eric
 

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#296
prasi said:
care to share data sheet? Molex is a sea, not easily available in my place, except for look alikes and pc's
I might just be able to fit
http://www.molex.com/molex/products/datasheet.jsp?part=active/0022232021_PCB_HEADERS.xml
reg
Prasi
Click to expand...

i feel, its always good practice to get commonly held opinions/ user's opinions while designing the pcb's so that its easier for the people to build...
in any case, people could grab 2.54mm pin headers available in their nearest bin, or order molex part ...
one thing (or many things) to note here for the HA...(build notes!)
All resistors are 1/4 W, except, R13/17, should be 1W.
C5/C4, are 10mm dia electro caps, fit as big as possible (16v or 25 v parts),
C1/C2 have 2.5mm pitch x 7mm dia or 3.5mm pitch x8mm dia
P1/P2 are 3296W bourns 5k pots,
i/p coupling cap when used, is a good quality Epcos/Wima >=1uF 5mm pitch 63v film cap (with R5=100k) or jumper it and use R5=22k/10k even....

C3 (anywhere between 330p to 1n) is optional and should be a NPO/C0G type....
bypass caps (C6/7) should be 100nf , x7r ceramic smd with 1206 package and are purely optional.
T1/T2/T3/T4 could be BC547/557 as per silk or could be BC550/560 , pl match hfe using atleast multimeter...
i have had good experience in closely matching hfe of i/p pair on Apex Fx-8 (sweet), with 2-3mV DC offset...
, nothing is special to note here, the beauty being commonly available parts for this design.

reg
Prasi
 
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#297
e_fortier said:
Hi Prasi,

I only adjusted the bias at 150mA with 0mV DC offset, I did not yet installed an input cap (2.2uF) so I've no clue how it sounds. Working now on the PSU since the heatsinks seems a bit too small.

For the input connector, see what I've used, fits nicely and has screws. X will like 😉

OSTVN02A150 On Shore Technology Inc. | Connectors, Interconnects | DigiKey

BR,
Eric
Click to expand...
Eric,
you seem to have some very special parts in your stock... all resistors/pots/connectors+blue pcb.... wow! nicely done....i am drooling here....
do have a listen and share your views...
one thing, for R17/13, are you sure you used hefty resistors?
reg
Prasi
 
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