diyAudio - Blog Entries
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
Old

Test Blog - no current words

Posted 10th April 2016 at 12:26 PM by Tea-Bag

Test only. Place holder.
Tea-Bag's Avatar
diyAudio Member
Posted in Uncategorized
Views 386 Comments 0 Tea-Bag is offline
Old

Restored and modded Cambridge Audio A3i

Posted 9th April 2016 at 01:51 PM by alexcp (My DIY projects)
Updated 13th April 2016 at 03:17 PM by alexcp

The designer of Cambridge Audio A3i had talked about the amp in this forum and suggested some changes to the components that bring the performance of the amp to a new level.

When I saw a cheap A3i on eBay, I decided to try it out. One channel was DOA, but it did not matter as I was about to mod it anyway.

Here is what I've done:
  1. Replaced all rectifiers (D201-D206 on the schematic) with soft recovery diodes and removed the capacitors in paralell with the diodes;
  2. Changed the grounding scheme so that the protection circuit and the relay driver are connected directly to the star ground;
  3. Added a 30ohm resistor in series with the rectifiers of the protection circuit;
  4. Replaced the electrolytic capacitors in the amplifier (but not the protection circuit) with Nichicon KA and replaced the two large power supply capacitors with Nichicon LLS;
  5. Replaced all film capacitors with Kemet PHE426 or, where PHE426 wouldn't fit, with Kemet SMR;
  6. Replaced the rectifiers
...
Attached Thumbnails
Click image for larger version

Name:	diyaudio_blog - 13.jpg
Views:	288
Size:	858.8 KB
ID:	1906   Click image for larger version

Name:	diyaudio_blog - 15.jpg
Views:	154
Size:	870.3 KB
ID:	1907   Click image for larger version

Name:	diyaudio_blog - 16.jpg
Views:	164
Size:	900.8 KB
ID:	1908   Click image for larger version

Name:	diyaudio_blog - 17.jpg
Views:	140
Size:	781.5 KB
ID:	1909  
Attached Files
File Type: pdf A3I schematic.pdf (1,011.2 KB, 92 views)
alexcp's Avatar
diyAudio Member
Views 390 Comments 0 alexcp is offline
Old

Krell KSA-5 clone

Posted 9th April 2016 at 01:27 PM by alexcp (My DIY projects)
Updated 11th April 2016 at 08:14 PM by alexcp

When I saw the discussions of KSA-5 headphone amplifier on head-case.org and on this forum, I thought it may be a nice use for the bag of 1000uF capacitors I had at the time. This was the main motivation for putting this Krell KSA-5 clone together.

The main challenge was to drill the front panel. The 10mm aluminum panel that came with the enclosure is easy to work with, but I wanted it to be pretty and asked the people at Modushop to CNC it for me.

Although it works ok, I think it is not a very good power amplifier for loudspeakers. As a headphone amplifier, it is no match for my Musical Fidelity X-CANv8.
Attached Thumbnails
Click image for larger version

Name:	diyaudio_blog - 10.jpg
Views:	546
Size:	954.1 KB
ID:	1904   Click image for larger version

Name:	diyaudio_blog - 11.jpg
Views:	431
Size:	908.3 KB
ID:	1905   Click image for larger version

Name:	ksa5.jpg
Views:	272
Size:	656.2 KB
ID:	1924  
Attached Files
File Type: pdf ksa5.pdf (129.1 KB, 242 views)
File Type: pdf ksa5psschem.pdf (54.7 KB, 241 views)
alexcp's Avatar
diyAudio Member
Views 405 Comments 0 alexcp is offline
Old

NCore based power amplifier

Posted 9th April 2016 at 01:20 PM by alexcp (My DIY projects)
Updated 9th April 2016 at 07:46 PM by alexcp

Ever since I heard about the Hypex NCore technology, I have wanted to build a power amplifier based on Hypex NC400 modules. Here is what I got. It works very well with the preamplifier from the previous post.

I used a spare Arduino to control the SMPSes. For now, it simply allows to use a momentary push button on the front panel. I may add remote control (12V trigger or similar) later.
Attached Thumbnails
Click image for larger version

Name:	diyaudio_blog - 9.jpg
Views:	537
Size:	460.3 KB
ID:	1903  
Attached Files
alexcp's Avatar
diyAudio Member
Views 257 Comments 0 alexcp is offline
Old

Bruno Putzeys' MicroPre

Posted 9th April 2016 at 01:14 PM by alexcp (My DIY projects)
Updated 11th April 2016 at 08:21 PM by alexcp

In April 2013, Linear Audio published in Vol.5 Bruno Putzeys' article "The G Word, or How to Get Your Audio off the Ground". Linear Audio included a free PCB for the demo project from the article: a balanced volume controller, or rather a minimalist balanced preamp with two pairs of balanced inputs.

I have been looking at balanced interconnects for some time and decided to use the free PCB and build the preamp. Here is what I built.

The enclosure used is Galaxy GX247 with front and back panels custom made by Front Panel Express. It was difficult to place a C14 power inlet on the back panel, as the space is quite limited due to the central placement of the six XLR connectors. An easy solution would be to fix the power cord permanently to the preamp, but I found a compact snap-in connector that fits the 3mm back panel of the enclosure.

I understand the article is available for download at the Hypex web site, and the PCB gerbers and a...
Attached Thumbnails
Click image for larger version

Name:	diyaudio_blog - 1.jpg
Views:	177
Size:	594.8 KB
ID:	1899   Click image for larger version

Name:	diyaudio_blog - 2.jpg
Views:	127
Size:	190.8 KB
ID:	1900   Click image for larger version

Name:	diyaudio_blog - 3.jpg
Views:	158
Size:	203.6 KB
ID:	1901   Click image for larger version

Name:	diyaudio_blog - 7.jpg
Views:	174
Size:	320.6 KB
ID:	1902   Click image for larger version

Name:	bp v5 f28a component_placement.png
Views:	101
Size:	397.0 KB
ID:	1928  

Click image for larger version

Name:	bp v5 f28b top.png
Views:	85
Size:	417.4 KB
ID:	1929   Click image for larger version

Name:	bp v5 f28c bottom.png
Views:	87
Size:	159.6 KB
ID:	1930  
Attached Files
File Type: pdf The G Word.pdf (731.5 KB, 65 views)
File Type: zip MicroPre_gerbers.zip (53.9 KB, 31 views)
alexcp's Avatar
diyAudio Member
Posted in Preamps
Views 431 Comments 0 alexcp is offline
Old

My Dream System (As of Today)

Posted 9th April 2016 at 07:08 AM by museguy

Fostex T40RP mk3 with mods, including MadDog Pads $140usd

Sennheiser HD600 $377usd

Headphone Amp
Krell KSA-5 Clone

DAC
?
diyAudio Member
Posted in Uncategorized
Views 262 Comments 0 museguy is offline
Old

Print A3-sized schematics from A4 printer (Windows/OSX/Linux)

Posted 8th April 2016 at 02:10 PM by autopoiesis

The situation

1. You have a schematic in PDF format, but it's hard to read when printed on A4
2. Only A4 printer available
3. Printer drivers can't solve the problem
4. A3 size wanted (ie two sheets A4, with some overlap for taping together)
5. Following (free/OSS) programs are available:
GIMP
PosteRazor

To illustrate point 3: my printer will print multiple pages per sheet ("2 in 1" - ie reduce), or print an A4 page on (n x n) sheets (A2 - four times the area), but there's no option to double the size to A3. A4 too small; A2 too big

Click image for larger version

Name:	Printer_NoA3Option.png
Views:	99
Size:	24.1 KB
ID:	1881

About GIMP - https://www.gimp.org/
Open source image manipulation program - sort of free Photoshop, plenty of info around.

About PosteRazor - PosteRazor - Make your own poster!
PosteRazor is designed to split image files into [n by m] individual pages in a single PDF file, on whatever page size...
Attached Thumbnails
Click image for larger version

Name:	GIMP_GIF_Export.png
Views:	72
Size:	32.8 KB
ID:	1874   Click image for larger version

Name:	GIMP_PDF_Import.png
Views:	54
Size:	27.0 KB
ID:	1875   Click image for larger version

Name:	PosteRazor1_GIF_Import.png
Views:	21
Size:	32.6 KB
ID:	1876   Click image for larger version

Name:	PosteRazor2_PaperFormat.png
Views:	34
Size:	14.6 KB
ID:	1877   Click image for larger version

Name:	PosteRazor3_OverlapOptions.png
Views:	34
Size:	13.8 KB
ID:	1878  

Click image for larger version

Name:	PosteRazor4_PosterSize.png
Views:	44
Size:	31.0 KB
ID:	1879   Click image for larger version

Name:	PosteRazor5_ExportPDF.png
Views:	18
Size:	26.8 KB
ID:	1880   Click image for larger version

Name:	PosteRazor_PDF_Output.png
Views:	48
Size:	65.7 KB
ID:	1882   Click image for larger version

Name:	FinalResult_Smalll.JPG
Views:	45
Size:	834.1 KB
ID:	1883  
Attached Files
autopoiesis's Avatar
diyAudio Member
Posted in Uncategorized
Views 300 Comments 0 autopoiesis is offline
Old

Mighty mite balanced SE classA headphone amp

Posted 5th April 2016 at 09:39 AM by abraxalito
Updated 25th April 2016 at 11:06 AM by abraxalito

I was going to call this amp 'fleapowered' but after doing some searching online I found fleapowered amps in general were much higher output power than this - single digit Watts typically. Whereas this one is more than a couple of orders of magnitude lower than that (under 10mW) so deserved a different moniker. Seeing as a mite is smaller than a flea, 'mighty mite' seemed to me as good as any descriptor for it.

The mighty mite started life in my imagination after I walked into a local headphones shop and tried out some cans that the shop assistant recommended to me - AT MSR7s. I'd brought my 'Buffalito' headphone buffer with me and some step down transformers for its output - fed from my mobile phone its way too loud for my AKGs and Superluxes. However the MSR7s were too loud even with the 2:1 step down trafo so I told the assistant I'd come back and listen again once I had a more suitable trafo. I figured it needed to be 4:1 step down, so I built a pair of those (PQ32/20)...
Attached Thumbnails
Click image for larger version

Name:	P60405-171819.jpg
Views:	175
Size:	364.2 KB
ID:	1868   Click image for larger version

Name:	P60408-113831.jpg
Views:	95
Size:	322.9 KB
ID:	1893  
Attached Files
abraxalito's Avatar
diyAudio Member
Views 407 Comments 2 abraxalito is offline
Old

Supermatched JFETs

Posted 29th March 2016 at 05:10 AM by rjm (RJM Audio Blog)
Updated 18th April 2016 at 11:52 PM by rjm

Truth be told, for a self-biased jfet audio circuit like the CrystalFET the main reason we need to used matched jfets is to ensure that the signal gain is the same in both channels. The operating point of the amplifier stage (the voltages and currents) can be allowed to vary a little so long as the transconductance, g_m is the same, as this is directly proportional to the open loop voltage gain, A, as

A = g_m R_l (transconductance x load resistance)

Now, yes, ideally you would find two jfets with identical saturation current and pinch off voltages, ensuring not just the same gain but also the same operating point. In practice though you are usually binning parts that are close to each other based on some reference parameter like the pinch off voltage (V_gs0) that you hope closely correlates with the signal gain. This is not quite as good though as the calculating the actual transconductance of the particular device in the circuit it is to be used in. And since...
Attached Thumbnails
Click image for larger version

Name:	supermatchB.png
Views:	111
Size:	33.5 KB
ID:	1953  
Attached Files
rjm's Avatar
rjm
diyAudio Member
Views 536 Comments 5 rjm is offline
Old

Pocketable headphone transformers

Posted 24th March 2016 at 02:44 AM by abraxalito
Updated 25th March 2016 at 11:54 PM by abraxalito

Seems I got a bit carried away with listening to my heavily modded XuanZu amp in the last-to-one blog post. I even considered it was superior to my current headphones - that would mean shelling out on some new ones. Before I went shopping though I did try it into my DT880s, which are 600ohms (hence I usually only use them for special occasions) - they sounded cleaner, although considerably quieter. This amp doesn't have enough voltage swing available to deliver the SPLs into such a high impedance. So was the cleanliness of these phones due to their being higher quality (they're at least 4* the cost of the others)? Or just because of listening at a lower level?

When my over-enthuasiasm for the amp had subsided a bit I decided to consider a way to answer these questions. If the amp was indeed not producing the artifacts which I was hearing on piano into the low-Z cans, then putting a 2:1 step-down transformer on its output would make no difference at all. The amp has plenty...
Attached Thumbnails
Click image for larger version

Name:	P60322-104815.jpg
Views:	67
Size:	249.6 KB
ID:	1839   Click image for larger version

Name:	P60326-074537.jpg
Views:	98
Size:	282.9 KB
ID:	1841  
Attached Files
abraxalito's Avatar
diyAudio Member
Views 323 Comments 0 abraxalito is offline
Hide this!Advertise here!

New To Site? Need Help?

All times are GMT. The time now is 02:15 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2016 DragonByte Technologies Ltd.
Copyright 1999-2016 diyAudio

Content Relevant URLs by vBSEO 3.3.2
Wiki