RJM Audio Sapphire Desktop Headphone Amplifier - Page 112 - diyAudio
Go Back   Home > Forums > Amplifiers > Headphone Systems
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Headphone Systems Everything to do with Headphones

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 12th February 2017, 12:30 AM   #1111
rjm is offline rjm  Japan
Richard Murdey
diyAudio Member
 
rjm's Avatar
 
Join Date: May 2004
Location: Kyoto
Blog Entries: 165
Some thoughts about what features to bake in (and which to remove) on the next board revision.

In addition to increasing the clearance between the power planes and the input, the main thing I feel needs to be addressed is gain selection.

This is done with a two position jumper and three resistors for R2, one fixed and two optional. Three gain options can be configured, 8-15-25 dB for example.

The other is the feedback connection. Rather than the flying resistor mod, what you have here is two R3 positions on the board. Use R3 for the usual connection, or populate R3X instead of R3 if you want to connect to the output.

I considered making this a jumper setting, but the thing is the values of R2 to use with R3X are different than for R3, so even if R3 was switchable you'd have to pull out all R2 and add new resistors to match. So realistically the board would have to be built as one or the other, which is why I opted to nix the second jumper.

Removed the V+ V- pads, and the T- pad (voltage TRIM an be referenced to case, COM, etc...)

Input welcome.
Attached Images
File Type: png pcb-sapphire-41c-brd-trial.png (64.5 KB, 322 views)
__________________
RJM Audio (phonoclone.com / G+)

Last edited by rjm; 12th February 2017 at 12:32 AM.
  Reply With Quote
Old 12th February 2017, 10:27 PM   #1112
rjm is offline rjm  Japan
Richard Murdey
diyAudio Member
 
rjm's Avatar
 
Join Date: May 2004
Location: Kyoto
Blog Entries: 165
Preview of 4.1d - minor clean up of 4.1c above.
Attached Images
File Type: png pcb-sapphire-41d-brd.png (82.1 KB, 276 views)
File Type: png pcb-sapphire-41d-sch.png (41.5 KB, 275 views)
__________________
RJM Audio (phonoclone.com / G+)
  Reply With Quote
Old 13th February 2017, 08:16 AM   #1113
diyAudio Member
 
Join Date: Aug 2012
Default Sapphire 4 Transformer Options

Has anyone has experience of the recommended Dual transformer vs a single transformer to power the 2 boards?

The reason for the question is that I have an existing chassis which would fit a single transformer easily, but will struggle with two.
I'm looking at the suggested alternative 'medical grade' Triad VPM24-1040 as a single transformer, is this sufficient in VA rating? There is a 50VA version available which would fit the chassis.

Any thoughts on sound quality of 1x vs 2x transformers greatly appreciated.

Andy
  Reply With Quote
Old 13th February 2017, 08:54 AM   #1114
rjm is offline rjm  Japan
Richard Murdey
diyAudio Member
 
rjm's Avatar
 
Join Date: May 2004
Location: Kyoto
Blog Entries: 165
If it means anything to you I will probably do future builds with just one transformer. Two VPMs just gets ridiculous in terms of total bulk. They are so much bigger than the VPTs and I'd rather have one VPM, with it's shield and screen, than two VPTs lacking either.

Triad VPM24-1040 is 1.04A/25 VA while the VPM24-2080 is 2.08A/50 VA. Since the price isn't dramatically different I'd get the biggest which still fits conveniently in the case, but I wouldn't lose sleep over "only" using 25 VA, it's enough even for stereo.
__________________
RJM Audio (phonoclone.com / G+)

Last edited by rjm; 13th February 2017 at 08:59 AM.
  Reply With Quote
Old 13th February 2017, 09:42 AM   #1115
diyAudio Member
 
Join Date: Aug 2012
Default Single it is

Many Thanks for the quick reply Richard, it's great to get such a quick response from the 'horses mouth'
  Reply With Quote
Old 22nd March 2017, 01:20 AM   #1116
rjm is offline rjm  Japan
Richard Murdey
diyAudio Member
 
rjm's Avatar
 
Join Date: May 2004
Location: Kyoto
Blog Entries: 165
Default Sapphire 4.1m

There were some layout tweaks in development, but the production boards 4.1m are not very different from 4.1d introduced above. Will have in hand by late April.
Attached Images
File Type: png pcb-sapphire-41m-brd.png (20.9 KB, 176 views)
File Type: png pcb-sapphire-41m-sch.png (20.4 KB, 168 views)
File Type: png sapphire-41m.png (198.3 KB, 90 views)
Attached Files
File Type: zip pcb-sapphire-41m-bom.zip (158.2 KB, 13 views)
__________________
RJM Audio (phonoclone.com / G+)
  Reply With Quote
Old 22nd March 2017, 04:20 AM   #1117
diyAudio Member
 
Join Date: Sep 2016
Location: Seoul
Hi RJM!
Board size seems changed to 7 * 9cm. Am I right?
  Reply With Quote
Old 22nd March 2017, 08:53 AM   #1118
rjm is offline rjm  Japan
Richard Murdey
diyAudio Member
 
rjm's Avatar
 
Join Date: May 2004
Location: Kyoto
Blog Entries: 165
No, the 70x90 indicates that the mounting holes conform to the metric standard for RJM Audio boards. The boards are 80x100, like before, and the mounting holes are the same also in this instance. The "70x90" label makes it explicit that this board conforms to the latest standard which I am working to make all my projects conform to, as:

1. 80x100 boards
2. 70x90 M3 mounting holes
3. 4 pad, edge mounted power input V++, COM, COM, V--
4. (5 pad edge mounted I/O IN+,IN-,GND,OUT-,OUT+) <- this could not be managed for the Sapphire layout unfortunately

VSPS200, CrystalFET, Phonoclone 3.8a, and Sapphire are compliant. VSPS300 and the old Phonoclone 3.5h are not.
__________________
RJM Audio (phonoclone.com / G+)

Last edited by rjm; 22nd March 2017 at 08:56 AM.
  Reply With Quote
Old 23rd March 2017, 08:53 AM   #1119
diyAudio Member
 
Join Date: Sep 2016
Location: Seoul
Quote:
Originally Posted by rjm View Post
No, the 70x90 indicates that the mounting holes conform to the metric standard for RJM Audio boards. The boards are 80x100, like before, and the mounting holes are the same also in this instance. The "70x90" label makes it explicit that this board conforms to the latest standard which I am working to make all my projects conform to, as:

1. 80x100 boards
2. 70x90 M3 mounting holes
3. 4 pad, edge mounted power input V++, COM, COM, V--
4. (5 pad edge mounted I/O IN+,IN-,GND,OUT-,OUT+) <- this could not be managed for the Sapphire layout unfortunately

VSPS200, CrystalFET, Phonoclone 3.8a, and Sapphire are compliant. VSPS300 and the old Phonoclone 3.5h are not.
Thank you for answer. Also for sharing your great work to public.
This project is very interesting and looks promising.
I thought it would be great if I can use hammond case. (1455T2201 or 2202)
With current PCB size, I need to put PCB one side on PCB rail, but the other side with stand-off. But it seems some resisters will short to chasis..
Maybe I will modify layout myself when proto phase is finished.
I will look forward to your result with Sapphire 4.1

Cheers,
  Reply With Quote
Old 23rd March 2017, 09:46 AM   #1120
rjm is offline rjm  Japan
Richard Murdey
diyAudio Member
 
rjm's Avatar
 
Join Date: May 2004
Location: Kyoto
Blog Entries: 165
Thanks.

I think you are better off with a much bigger chassis. I recommend this one. Plan to allow about 20 cm in width and 30 cm depth, otherwise things get really cramped.
__________________
RJM Audio (phonoclone.com / G+)
  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
RJM Audio Sapphire Headphone Amplifier rev14a1 kit rjm Group Buys 14 2nd September 2016 11:23 PM
RJM Audio Gainbloc Preamplifier Mk. I rjm Analog Line Level 11 7th September 2011 11:59 PM
Parts for RJM Audio/47 Labs Phoneclone jim rose Swap Meet 0 15th May 2011 06:55 PM
New Desktop Tube Amplifier, 6V6 SE Musik007 Twin Audio 11 6th October 2010 04:23 PM
FS: DIY Cavalli Audio Embedded Hybrid Headphone Amplifier sachi Swap Meet 4 19th May 2010 09:43 PM


New To Site? Need Help?

All times are GMT. The time now is 05:40 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2
Wiki