diyAudio - Entries for April 2017
Go Back   Home > Forums > Blogs
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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

Sapphire 4 headphone amplifier [Rev. 4.1m]

Posted 24th April 2017 at 01:02 AM by rjm (RJM Audio Blog)
Updated 21st June 2017 at 09:17 AM by rjm

Development thread starts here.

While I consider this my best work to date, the documentation trail has become hopelessly scattered so let me try to regroup in this blog post and make some sort of gateway/portal to the project. [Update: web page write up now finished.]

The followup to the Sapphire 3 started out as a generic musing on stacked diamond buffers and current mirror amplification, coalesced for a bit as the ill-fated Project Unity before becoming part of the Sapphire line initially as a temporary measure as something I could drop in my existing chassis for testing. The first iteration kept the open loop buffer of previous Sapphire iterations, but now I'm running the 4.1m boards with the buffer inside the feedback loop I realize I've ended up at just the classic, dictionary definition current feedback amplifier (CFA). Sigh. So much for originality. It sounds great though, so I'm not as upset about it as I might have been.

Attached Thumbnails
Click image for larger version

Name:	pcb-sapphire-41m-brd.png
Views:	129
Size:	20.9 KB
ID:	2360   Click image for larger version

Name:	sapphire-41m.png
Views:	89
Size:	198.3 KB
ID:	2361   Click image for larger version

Name:	pcb-sapphire-41m-sch.png
Views:	229
Size:	20.4 KB
ID:	2362   Click image for larger version

Name:	DSC_1165s.jpg
Views:	153
Size:	203.3 KB
ID:	2363   Click image for larger version

Name:	DSC_1172s.jpg
Views:	126
Size:	386.5 KB
ID:	2364  

Click image for larger version

Name:	sapphire-41-ltspice R3X 15dB.png
Views:	119
Size:	83.5 KB
ID:	2376   Click image for larger version

Name:	summary.png
Views:	68
Size:	21.8 KB
ID:	2377  
Attached Files
File Type: zip (195.9 KB, 58 views)
File Type: asc Sapphire 41.asc (6.2 KB, 103 views)
rjm's Avatar
diyAudio Member
Views 457 Comments 3 rjm is offline

Now For Something Completely Different - In a Neat Little Box!

Posted 22nd April 2017 at 04:30 AM by googlyone
Updated 22nd April 2017 at 04:40 AM by googlyone

After a few months of playing with loudspeaker drivers and software fixes to code that I wished I had never written in the first place, the lure of the BJT loomed large again...

There I was, sitting at my desk, and pondering where these dark feelings were coming from and how to scratch that evil itch, and my eyes came to rest upon that most ludicrous of things - the amplifier of 100 transistors.

About a year ago, or so it seems to me sitting here, I built this homage to the BC549, or as the engineer in me says, "Laughably stupid thing, which probably shouldn't work. Who would be dumb enough to try and find out?".

It needed a case. It needed a power supply. It deserved each of the above that would allow it to work, and ideally take an equally "left field" approach. it should never have been built, but it had. It should have been put in the back of a very dark, locked cupboard, but it had not.

The idea then...
Attached Thumbnails
Click image for larger version

Name:	RESIZE_Many_Tiny_Chassis.jpg
Views:	97
Size:	734.6 KB
ID:	2354   Click image for larger version

Name:	resize_MAny_Tiny_Workshop.jpg
Views:	110
Size:	973.2 KB
ID:	2355   Click image for larger version

Name:	resize_Many_Timy_Complete.jpg
Views:	195
Size:	1,010.2 KB
ID:	2356   Click image for larger version

Name:	RESIZE_Many_Tiny_Chassis_1.jpg
Views:	110
Size:	974.4 KB
ID:	2357   Click image for larger version

Name:	Resize_Many_Tiny__Case.jpg
Views:	106
Size:	848.1 KB
ID:	2358  

Click image for larger version

Name:	Resize_Many_Tiny_Lid.jpg
Views:	88
Size:	956.8 KB
ID:	2359  
Attached Files
diyAudio Member
Posted in Uncategorized
Views 411 Comments 4 googlyone is offline

CrystalFET 2 MM passive phono preamplifier with JFET amplification

Posted 21st April 2017 at 01:05 AM by rjm (RJM Audio Blog)
Updated 21st April 2017 at 04:44 AM by rjm (revised to 2.0g (capacitors C9 and C10 misslabelled))

In hindsight the original CrystalFET suffered from overreach. To obtain the 55 dB midband gain required for an MC phono stage lots of other things I might have wanted to build into the design like degenerative feedback were discarded.

Degenerative feedback as it applies to JFET amplifiers is the practice of leaving the source resistor partially or completely unbypassed. It reduces the voltage gain, but linearizes the dynamic operation of the amplifier - coercing the gain to the ratio of the source and drain resistors rather than leaving it defined by the JFET transconductance. The circuit gain can then be fixed by the designer without worrying so much about matching devices.

The CrystalFET circuit is a traditional two stage passive photo preamplifier design, the only novelty here is the addition of a second JFET configured as a source follower to each amplifier stage. To obtain above 50 dB gain no degenerative feedback could be used, and the JFETs had to be not...
Attached Thumbnails
Click image for larger version

Name:	pcb-crystal-20g-sch.png
Views:	190
Size:	9.9 KB
ID:	2347   Click image for larger version

Name:	pcb-crystal-20g-brd.png
Views:	110
Size:	35.5 KB
ID:	2348   Click image for larger version

Name:	crystal20g.png
Views:	84
Size:	142.5 KB
ID:	2349   Click image for larger version

Name:	crystal20-response.png
Views:	79
Size:	20.9 KB
ID:	2353  
Attached Files
File Type: zip (63.3 KB, 49 views)
File Type: zip (220.3 KB, 50 views)
File Type: asc Crystal 20.asc (5.2 KB, 98 views)
rjm's Avatar
diyAudio Member
Views 308 Comments 0 rjm is offline

Group Buy for Salas Boards

Posted 17th April 2017 at 06:05 PM by Tea-Bag

DCG-3 preamplifier and DCSTB DC Power stabilizer purpose built for it

The boards are going to be in Matte black, like the PS on the right

Click the image to open in full size.

Threads for boards:

Building Thread

GB Thread

DCSTB Board $20
DCSTB Board $25
Transistor Kits for the DCG-3 and the DCSTB are available. Full kits are also available.
DCG-3 Transistor Kit $ 40 - includes matched transistors where needed.
DCG-3 Full Kit (includes transistor kit) $75


Note that DCSTB kits only cover half the board. Additionally, if you wish to run at a higher bias and...
Tea-Bag's Avatar
diyAudio Member
Posted in Uncategorized
Views 527 Comments 0 Tea-Bag is offline

Hafler 9505 power supply capacitors for sale. IMPOSSIBLE to find!!!

Posted 11th April 2017 at 10:38 PM by wmeyer
Updated 14th April 2017 at 10:59 AM by wmeyer (forgot the caps value though members would look up supplied part #)

Would anyone be interested in purchasing Hafler 9505 PS capacitors? I am looking into acquiring brand new caps not NOS. I'm not sure what I will be charging but if I was to make a guess I would say about $100.00 each. The 9505 uses 4 of these. You can also use these in other projects as well. The small size makes it perfect for a low profile amplifier. These are very hard to find. Here is the part number, DCMX203U100CJ2B Please let me know if this works for anyone out in the diy world, Please chime in. The caps are 20,000uF 100vdc 3.635"tall x 2.5" dia with lead spacing of 1.13".
These are a direct drop in for the Hafler 9505 TransNova amplifier or this number also. i am waiting for a reply. 3186FD203T100BPA1
diyAudio Member
Posted in Uncategorized
Views 403 Comments 3 wmeyer is offline
Hide this!Advertise here!

New To Site? Need Help?

All times are GMT. The time now is 02:44 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