Juma's Head Amp

[prasi]

Did you get local pots or did you order from rs or the likes?

Sent from my A0001 using Tapatalk

I had the pots from an online seller in India. I think they are only reselling aliexpress stuff (albeit at a higher price, but still way less than element14/ rs).

 

[saheb11123]

I had the pots from an online seller in India. I think they are only reselling aliexpress stuff (albeit at a higher price, but still way less than element14/ rs).

Only the rs stuff is genuine as both local and indian sites sell same chinese bourns knock-offs.
I had the pleasure of experiencing this when I was building my f5t, had to change the pot 3-4 times.

Sent from my A0001 using Tapatalk

 

[prasi]

Here is my version of a compact single-sided PCB PSU for "laser printer's technology"

nicely done, very compact. do post if you decide to build it.

 

[saheb11123]

Btw from where did you get the ir's from?

Sent from my A0001 using Tapatalk

 

[prasi]

ir's i got from a trusted local store in my city😀, i never experienced bad quality from him.

 

[e_fortier]

I'm having some thermal issue with the Juma HA. After the HA is on for a few hours my heatsink goes un to about 45C (flat rectangular surface of 150 x 75 x 12mm aluminum), it could be my fault since the bias was set to 150mA despite Juma's range of 50-100mA.

Fab recommended that I could simply lower the bias, this makes sense but how do you determine the required bias for a headphone amp ? My headphone are Senn HD380 Pro which are rated 54ohm. Would a bias of 50mA sufficient ? I want to make sure the SQ will remain just as good as when biased at 150mA ? I'm not too sure about how to calculate all this, is there any rules of thumb.

Thanks,
Eric

 

[cwtim01]

From the HD380 Pro spec, it only needs 1Vrms to produce 110dB SPL. At 110dB SPL, it'll take 30mins of listening to cause permanent hearing damage. With 54R impedance, it only needs 26mA to reach 1Vrms.

50-100mA bias is pretty sufficient, more will lower the distortion but it's then how much heat you can deal with.

 

[e_fortier]

This is exactly the info. I was looking for, THANKS!!

The amp will be a table top type, ac powered with a linear +/- 15Vdc regulated supply.

I will lower the bias to 100mA.

Thanks,
Eric

 

[chat72]

potepuh;4932184]xrk- 1 set (1 PSU+1 Stereo HA)+2 buffer-shipped-delivered
gannaji- 1 set (1 PSU+1 Stereo HA)-delivered
saheb- 1 set (1 PSU+1 Stereo HA+2 buffer)-shipped
kram- 1 set (1 PSU+1 Stereo HA)-shipped
rumina-1 set (1 PSU+1 Stereo HA)- shipped-delivered
nicusim-1 set (1 PSU+1 Stereo HA)- shipped-delivered
potepuh-1 set (1 PSU+1 Stereo HA)- shipped-delivered
e_fortier-2 PSU +1 Stereo HA+2 buffer-shipped
touchdown -1 Stereo HA-shipped
albertNL- 1 set (1 PSU+1 Stereo HA) shipped-delivered
Malvin - 1 set (1 PSU+1 Stereo HA)-shipped
DrizztDo-1 set (1PSU+1 Stereo HA)+1 Buffer- shipped-delivered
one more member through PM-1set(1 PSU+1 Stereo HA)-shipped
one more member through PM-1set(1 PSU+1 Stereo HA)-shipped
one more member through PM-1set(1 PSU+1 Stereo HA+2buffer)-shipped -delivered
one more member through PM-1set(1 PSU+1 Stereo HA)-shipped
thimios -1 set (1 PSU+1Stereo HA)-shipped
nicusim-1 more set (1 PSU+1HA)-shipped
chat72- 1 set (1 PSU+1HA)-shipped-delivered

Thank

 

[e_fortier]

Hi Chat72,

The latest post with the list of delivered PCBs was no.443, it seems you did not use that one so post 489 is not accurate.

BR,
Eric

 

[prasi]

5 more people need to confirm the delivery..
xrk- 1 set (1 PSU+1 Stereo HA)+2 buffer-shipped-delivered
gannaji- 1 set (1 PSU+1 Stereo HA)-delivered
saheb- 1 set (1 PSU+1 Stereo HA+2 buffer)-shipped-delivered
kram- 1 set (1 PSU+1 Stereo HA)-shipped-delivered
rumina-1 set (1 PSU+1 Stereo HA)- shipped-delivered
nicusim-1 set (1 PSU+1 Stereo HA)- shipped-delivered
potepuh-1 set (1 PSU+1 Stereo HA)- shipped-delivered
e_fortier-2 PSU +1 Stereo HA+2 buffer-shipped-delivered
touchdown -1 Stereo HA-shipped
albertNL- 1 set (1 PSU+1 Stereo HA) shipped-delivered
Malvin - 1 set (1 PSU+1 Stereo HA)-shipped
DrizztDo-1 set (1PSU+1 Stereo HA)+1 Buffer- shipped-delivered
one more member through PM-1set(1 PSU+1 Stereo HA)-shipped
one more member through PM-1set(1 PSU+1 Stereo HA)-shipped
one more member through PM-1set(1 PSU+1 Stereo HA+2buffer)-shipped -delivered
one more member through PM-1set(1 PSU+1 Stereo HA)-shipped
thimios -1 set (1 PSU+1Stereo HA)-shipped
nicusim-1 more set (1 PSU+1HA)-shipped
chat72- 1 set (1 PSU+1HA)-shipped-delivered

 

[prasi]

5 more people need to confirm the delivery..
xrk- 1 set (1 PSU+1 Stereo HA)+2 buffer-shipped-delivered
gannaji- 1 set (1 PSU+1 Stereo HA)-delivered
saheb- 1 set (1 PSU+1 Stereo HA+2 buffer)-shipped-delivered
kram- 1 set (1 PSU+1 Stereo HA)-shipped-delivered
rumina-1 set (1 PSU+1 Stereo HA)- shipped-delivered
nicusim-1 set (1 PSU+1 Stereo HA)- shipped-delivered
potepuh-1 set (1 PSU+1 Stereo HA)- shipped-delivered
e_fortier-2 PSU +1 Stereo HA+2 buffer-shipped-delivered
touchdown -1 Stereo HA-shipped
albertNL- 1 set (1 PSU+1 Stereo HA) shipped-delivered
Malvin - 1 set (1 PSU+1 Stereo HA)-shipped-delivered
DrizztDo-1 set (1PSU+1 Stereo HA)+1 Buffer- shipped-delivered
one more member through PM-1set(1 PSU+1 Stereo HA)-shipped
one more member through PM-1set(1 PSU+1 Stereo HA)-shipped
one more member through PM-1set(1 PSU+1 Stereo HA+2buffer)-shipped -delivered
one more member through PM-1set(1 PSU+1 Stereo HA)-shipped
thimios -1 set (1 PSU+1Stereo HA)-shipped
nicusim-1 more set (1 PSU+1HA)-shipped-delivered
chat72- 1 set (1 PSU+1HA)-shipped-delivered

 

[prasi]

4 more members to confirm
xrk- 1 set (1 PSU+1 Stereo HA)+2 buffer-shipped-delivered
gannaji- 1 set (1 PSU+1 Stereo HA)-delivered
saheb- 1 set (1 PSU+1 Stereo HA+2 buffer)-shipped-delivered
kram- 1 set (1 PSU+1 Stereo HA)-shipped-delivered
rumina-1 set (1 PSU+1 Stereo HA)- shipped-delivered
nicusim-1 set (1 PSU+1 Stereo HA)- shipped-delivered
potepuh-1 set (1 PSU+1 Stereo HA)- shipped-delivered
e_fortier-2 PSU +1 Stereo HA+2 buffer-shipped-delivered
touchdown -1 Stereo HA-shipped
albertNL- 1 set (1 PSU+1 Stereo HA) shipped-delivered
Malvin - 1 set (1 PSU+1 Stereo HA)-shipped-delivered
DrizztDo-1 set (1PSU+1 Stereo HA)+1 Buffer- shipped-delivered
one more member through PM-1set(1 PSU+1 Stereo HA)-shipped-delivered
one more member through PM-1set(1 PSU+1 Stereo HA)-shipped
one more member through PM-1set(1 PSU+1 Stereo HA+2buffer)-shipped -delivered
one more member through PM-1set(1 PSU+1 Stereo HA)-shipped
thimios -1 set (1 PSU+1Stereo HA)-shipped
nicusim-1 more set (1 PSU+1HA)-shipped-delivered
chat72- 1 set (1 PSU+1HA)-shipped-delivered

 

[xrk971]

Prasi,
The regulated PSU works fine powering the Salas DCG3 headamp. I have it set at 14v with load otherwise there is no regulation because the amp draws a lot of current and sags the rails down from a higher setting.

http://www.diyaudio.com/forums/anal...cg3-preamp-line-headphone-99.html#post4952245

 

[prasi]

Thats nice to know and nice build. Do share the Juma HA build once you get a moment to assemble it.
A gentleman has kindly agreed to send me an extra pcb of Nazar PSU. Waiting for that to build this PSU properly.
reg
Prasi

 

[TIC37]

Late..... what to do??

Hello, late as usual!!

What can I do more than stand in queue for the next coming GB of Jumas HA.

Put me up for a coming event, pleeease!!

 

[prasi]

Hi, Sure, will keep in mind.
reg
Prasi

 

[prasi]

some postmen are still in new year holidays...
remaining people, if you have received pl confirm .........
3 more members to confirm
xrk- 1 set (1 PSU+1 Stereo HA)+2 buffer-shipped-delivered
gannaji- 1 set (1 PSU+1 Stereo HA)-delivered
saheb- 1 set (1 PSU+1 Stereo HA+2 buffer)-shipped-delivered
kram- 1 set (1 PSU+1 Stereo HA)-shipped-delivered
rumina-1 set (1 PSU+1 Stereo HA)- shipped-delivered
nicusim-1 set (1 PSU+1 Stereo HA)- shipped-delivered
potepuh-1 set (1 PSU+1 Stereo HA)- shipped-delivered
e_fortier-2 PSU +1 Stereo HA+2 buffer-shipped-delivered
touchdown -1 Stereo HA-shipped
albertNL- 1 set (1 PSU+1 Stereo HA) shipped-delivered
Malvin - 1 set (1 PSU+1 Stereo HA)-shipped-delivered
DrizztDo-1 set (1PSU+1 Stereo HA)+1 Buffer- shipped-delivered
one more member through PM-1set(1 PSU+1 Stereo HA)-shipped-delivered
one more member through PM-1set(1 PSU+1 Stereo HA)-shipped-delivered
one more member through PM-1set(1 PSU+1 Stereo HA+2buffer)-shipped -delivered
one more member through PM-1set(1 PSU+1 Stereo HA)-shipped
thimios -1 set (1 PSU+1Stereo HA)-shipped
nicusim-1 more set (1 PSU+1HA)-shipped-delivered
chat72- 1 set (1 PSU+1HA)-shipped-delivered

 

[rumina]

Has anyone build the Juma amp with the new prasi pcb? I have problems to bring the offset down. Whats the way to set bias and offset properly with this pcb? What should be the voltage across the 2w resistor?

Prasis psu works fine with the corrected diode position, so half way done ;-).

 

[prasi]

Hi Rumina,
Pl have a look here on how to set bias and adjust offset at the same time. post no. 224 http://www.diyaudio.com/forums/pass-labs/298369-jumas-head-amp-23.html#post4896041

I did manage to damage my psu pcb (wrong value resistor build). i received a new pcb just recently. next weekend i will try and test the psu and if possible the ha.