★★Free JLH Hifi Headphone Amp PCB, 0.008% THD★★ - Page 8 - diyAudio
Go Back   Home > Forums > Commercial Sector > Vendor Forums > Siliconray Online Electronics Store

Siliconray Online Electronics Store Amplifier boards, HiFi components, tubes and all kinds of electronics for the DIYer from Siliconray

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 24th May 2014, 12:05 PM   #71
diyAudio Member
 
nautibuoy's Avatar
 
Join Date: Jan 2010
I received my free headphone amp boards thank you. Nice boards too.

Ray
  Reply With Quote
Old 30th May 2014, 12:07 PM   #72
diyAudio Member
 
e_fortier's Avatar
 
Join Date: May 2001
Location: Canada
Hi Siliconray,

I have recently built the JLH 2005 power amp version and it sounds great. The only issue I had was that the spacing on the small transistors TO-92 style are VERY close to each other, also the size of the pads are too small unless you are used to doing surface mount soldering, if you do a re-spin of the PCB please think about this request.

Is it the same for this headphone amp ? I would buy a kit if these spacing and pad were bigger.

Thanks for offering these PCB and kits.

BR,
Eric

Last edited by e_fortier; 30th May 2014 at 12:12 PM.
  Reply With Quote
Old 15th August 2014, 09:28 PM   #73
diyAudio Member
 
nautibuoy's Avatar
 
Join Date: Jan 2010
Hi SiliconRay

It's time for me to assemble my boards but some questions if I may;

1. I've not tracked down any heatsinks like those you've used. Can you advise where I can get some or tell me what spec (deg C/Watt) I need to obtain? I plan to use 15V supplies with 150-200mA quiescent current.

2. Where can I find the instructions for setting up the boards for quiescent current and dc offset once I've assembled them?

Thanks

Ray
  Reply With Quote
Old 16th August 2014, 08:11 AM   #74
diyAudio Member
 
nautibuoy's Avatar
 
Join Date: Jan 2010
Iíve had a good look around and I can find little information to support the build process, so Iím piecing things together for myself. Grateful to anyone who can check the following.
Regarding setting up the boards, VR2 sets Quiescent Current and VR1 adjusts DC offset.
I should adjust the quiescent current, then the DC offset, then iterate a couple of times through the process to reach optimal settings.
Input should be shorted and connections made after set up.
Dummy load resistor should be connected across outputs during set up.
To set Quiescent Current (Iq):
Voltage across R10 = Iq * R10
Therefore, assuming R10 = 0.51R and required Iq = 200mA
Voltage across R10 = 0.2 * 0.51 = 0.102V DC
Connect multimeter probes across R10 and adjust VR2 until the voltage measured = 0.1V.
To adjust DC Offset:
Connect multimeter probes across the output and adjust VR1 to lowest level of DC.
Other Considerations:
There seem to be some examples of alternative output transistors causing oscillation. I propose using BD937 transistors for Q1 & Q2 as these seem to be a safe option with respect to stability and sound quality and have the same pinout as the MJE3055 devices?
I will be using regulated supplies at +/-15V, which is within the range shown on the PCB.
Suitable heatsinks?
Sorry if this is basic stuff by I am no electronics expert and would rather be safe than sorry.
Thanks
Ray
  Reply With Quote
Old 16th August 2014, 03:12 PM   #75
diyAudio Member
 
e_fortier's Avatar
 
Join Date: May 2001
Location: Canada
Quote:
Originally Posted by nautibuoy View Post
I’ve had a good look around and I can find little information to support the build process, so I’m piecing things together for myself. Grateful to anyone who can check the following.
Regarding setting up the boards, VR2 sets Quiescent Current and VR1 adjusts DC offset.
I should adjust the quiescent current, then the DC offset, then iterate a couple of times through the process to reach optimal settings.
Input should be shorted and connections made after set up.
Dummy load resistor should be connected across outputs during set up.
To set Quiescent Current (Iq):
Voltage across R10 = Iq * R10
Therefore, assuming R10 = 0.51R and required Iq = 200mA
Voltage across R10 = 0.2 * 0.51 = 0.102V DC
Connect multimeter probes across R10 and adjust VR2 until the voltage measured = 0.1V.
To adjust DC Offset:
Connect multimeter probes across the output and adjust VR1 to lowest level of DC.
Other Considerations:
There seem to be some examples of alternative output transistors causing oscillation. I propose using BD937 transistors for Q1 & Q2 as these seem to be a safe option with respect to stability and sound quality and have the same pinout as the MJE3055 devices?
I will be using regulated supplies at +/-15V, which is within the range shown on the PCB.
Suitable heatsinks?
Sorry if this is basic stuff by I am no electronics expert and would rather be safe than sorry.
Thanks
Ray
Very good job at figuring this by yourself. A few details I would do differently ;

1. Adjust DC offset via VR1 while amp is cold. No loads connected to output.
2. Adjust Bias via VR2 while amp is cold. No loads connected to output.
3. Measure bias across R10 like you mentioned, perfect.
4. If your running the amp at +/- 15Vdc instead of +/- 12Vdc maybe the 200mA intended for +/- 12Vdc supply will be different for your +/- 15Vdc setting. Siliconray to confirm.
5. Once amp is warm (wait 1h) repeat step 1-3.

For the heatsink, running your amp at +/-15Vdc gives you 30Vdc at 0.2A therefore 6W of heat to dissipate / channel (3W for Q1 & 3W for Q2). If you need a heatsink maximum temp. rise of lets say 15C your heatsink requirement will be 15C/3W = 5 C/W for a final heatsink temp. of 15C + 25C ambient so roughly 40C.

An exemple : http://uk.farnell.com/multicomp/mc33...hed/dp/1710610

I built the JLH 2005 power amp using +/- 14Vdc supply, I got 10W/ch. It's a great sounding amp

Keep us posted on your built.

Rgds,
Eric

Last edited by e_fortier; 16th August 2014 at 03:36 PM.
  Reply With Quote
Old 16th August 2014, 11:53 PM   #76
diyAudio Member
 
nautibuoy's Avatar
 
Join Date: Jan 2010
Thanks Eric, that is very helpful.

Upon further consideration, it's easy enough to adjust the voltage of my power supply modules so I will do that and run +/-12V rails. That'll mean I will need to dissipate 2.4W per output device; allowing a temp rise of 25C means a heatsink of circa 10C/W or better (to allow for the inevitable inefficiencies).

I'll update in due course.

Ray
  Reply With Quote
Old 17th August 2014, 04:06 AM   #77
diyAudio Member
 
e_fortier's Avatar
 
Join Date: May 2001
Location: Canada
You are welcome Ray.

Final temp of 50C is on the high side, aiming for a lower value would prolong the life of your output transistors and improve reliability. It's up to you.

Have fun building the headphone amp.

Rgds,
Eric
  Reply With Quote
Old 12th September 2014, 07:37 PM   #78
diyAudio Member
 
nautibuoy's Avatar
 
Join Date: Jan 2010
I've got all the parts together now and started soldering up the board today; I have to say that it's a dog to solder though, the ground pads in particular. I don't know if it is just the extremely small pads or the a combination of that and the gold finish but it's really hard to get good solder flow and I keep getting dry joints.

I'm using good quality Stannol brand solder (4% silver, lead free) and a 60W temp=controlled solder station with a very small chisel tip. Never had a problem soldering up boards before.

Anyone else had a problem?

Ray
  Reply With Quote
Old 12th September 2014, 07:53 PM   #79
diyAudio Member
 
e_fortier's Avatar
 
Join Date: May 2001
Location: Canada
Quote:
Originally Posted by nautibuoy View Post
I don't know if it is just the extremely small pads or the a combination of that and the gold finish but it's really hard to get good solder flow and I keep getting dry joints.

I'm using good quality Stannol brand solder (4% silver, lead free) and a 60W temp=controlled solder station with a very small chisel tip. Never had a problem soldering up boards before.

Anyone else had a problem?

Ray
Have a look at my comments on post no.72 they are identical as yours...there is no reason for having such small pads soldering becomes a PITA.

If the pads were bigger I would buy one of these board right away.

Rgds,
Eric
  Reply With Quote
Old 12th September 2014, 09:09 PM   #80
diyAudio Member
 
nautibuoy's Avatar
 
Join Date: Jan 2010
Yes Eric, PITA is about right. I have the joy of soldering the small transistors in the morning!

Ray
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
★★ Free PCB for JLH 2005 Class-A Amplifier siliconray Siliconray Online Electronics Store 219 14th June 2014 07:43 PM
★BR Bookshelf Cabinets for Mark Audio CHR-70, Special Price:$65/pair only Musik007 Twin Audio 112 15th August 2013 05:20 PM
★★Another Donation: Free Power Supply PCB For JLH Amp, including components! siliconray Siliconray Online Electronics Store 2 12th December 2011 10:18 PM
Another free PCB project: JLH headphone amplifier siliconray Solid State 0 29th November 2011 07:57 AM
★Plywood bookshelf cabinets for CHR-70, Special Price: US$60/pair only Musik007 Twin Audio 50 23rd August 2011 02:10 PM


New To Site? Need Help?

All times are GMT. The time now is 07:28 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2