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

Stereo VSPS rev 50c

Posted 25th April 2012 at 01:48 AM by rjm (RJM Audio Blog)

The original stereo VSPS project is now quite mature. I did a couple of minor tweaks on the last re-spin of the layout, removing the pads for the old Black Gate coupling caps (long gone), adding thermal isolation, and making room for a pair of optional ceramic bypass caps next to the op amp.

The new boards are matt black. Quite cool. I have a small stack if you need any.

All the info you need to build one is attached.
Attached Thumbnails
Click image for larger version

Name:	DSC_3986 1280.jpg
Views:	712
Size:	235.5 KB
ID:	644   Click image for larger version

Name:	pcb-vsps-50c.png
Views:	1943
Size:	13.3 KB
ID:	645   Click image for larger version

Name:	pcb-vsps-50c-brd.png
Views:	2269
Size:	10.2 KB
ID:	646   Click image for larger version

Name:	pcb-vsps-50c-sch.png
Views:	1460
Size:	24.3 KB
ID:	647  
Attached Files
File Type: zip pcb-vsps50c.zip (83.0 KB, 397 views)
File Type: zip pcb-vsps50c-bom.zip (86.2 KB, 333 views)
rjm's Avatar
rjm
diyAudio Member
Views 2439 Comments 2 rjm is offline
Old

Custom building

Posted 21st April 2012 at 02:10 PM by jtktam (Newbie audio DIYer)

Last few months have been crazy with my day time job and with the custom builds I have taken up.

A water leak above my hobby work space caused a big headache. I had to sort through some of the boxes and trash tons of wet parts but now I am back in full swing

Lately there was some rumbling about ODAC being a commerical product etc.. I was caught in the crossfire trying to organize a groupbuy since the designer / manufacturer is local to me.

I have approach the admins about this and the "correct" way to get this going.. sucks trying to do people a service and get shot down with the rest of the violators

Looking to start a web site with pictures of my builds to try get more business.. this hobby is eating lots of my money and the excess parts is taking up too much space
diyAudio Member
Posted in Uncategorized
Views 965 Comments 1 jtktam is offline
Old

Flattening the NOS droop

Posted 14th April 2012 at 04:13 AM by abraxalito
Updated 14th April 2012 at 04:48 AM by abraxalito

Having been a fan of NOS DACs now for something over a year I've decided it was high time for sorting out their most serious drawback - the roll off in the HF. This is an unavoidable result of using a zero-order hold function to reconstruct the original (impulse) samples. Droop exists even with oversampled DACs, its just at its most severe in NOS.

One of the most popular ways to flatten the response is to add on some kind of analog filter with a rising response (to 3.16dB @ 20kHz). A first order shelving filter can't quite cut it though so an LC tank circuit has been employed by a few. This needs to have a moderately high Q to achieve the correction.

I've played around with inductors to achieve this and haven't much liked the resulting sound. Whether this was due to the particular inductors I was using I didn't experiment. Admittedly they were very cheap ones. In general though when I've used high Q circuits in crossovers I haven't much liked the colouration...
abraxalito's Avatar
diyAudio Member
Views 1413 Comments 10 abraxalito is offline
Old

X-reg Evaluation Boards

Posted 7th April 2012 at 01:15 AM by rjm (RJM Audio Blog)
Updated 9th April 2012 at 04:37 AM by rjm

Once in a while I get emails asking after the X-reg evaluation boards. These are handy little 5x8 cm test boards for the X-reg voltage regulator - or they would be, if I had ever bothered to get a set made.

Since the circuit is built into the VSPS300 and Phonoclone 3, it wasn't really a big priority.

Anyhow, yesterday I re-drew the evaluation boards and I'll be getting a batch made in the near future, along with some of the stereo VSPS that people were also asking after recently. They won't exactly fly off the shelves, but I started to feel bad for those few people who actually wanted them.
Attached Thumbnails
Click image for larger version

Name:	pcb-xreg-15c-brd.png
Views:	1343
Size:	10.3 KB
ID:	640   Click image for larger version

Name:	pcb-xreg-15c.png
Views:	1813
Size:	11.0 KB
ID:	641   Click image for larger version

Name:	pcb-xreg-15c-sch.png
Views:	1108
Size:	22.2 KB
ID:	642  
Attached Files
File Type: zip pcb-xreg.zip (129.5 KB, 340 views)
rjm's Avatar
rjm
diyAudio Member
Views 1610 Comments 0 rjm is offline
Old

Recycling?

Posted 2nd April 2012 at 09:37 PM by DigitalJunkie

So,one of the monitors I use decided to die yesterday,it came back from standby,but had rainbow lines all over the screen..Something in the TFT panel itself,COF or something.Gaw.

Anyways,it had built in sound,using a TDA7496L chip for the amp..I got to looking at it,and decided to pull it off the PCB and build a (headphone)amp with it.

It's basically the schematic on the datasheet,with slightly larger input and output caps,and it's all powered by a 3-cell Li-ion pack for a Vcc of about 11-12V.

Here's the datasheet.
http://www.st.com/internet/com/TECHN...CD00001216.pdf

It doesn't sound tooo bad,really. It's not the best thing ever,but for a couple hours of tinkering with junk that was on the bench, I'm pleased.
It's got more than enough power for 'phones,some care needs to be taken to prevent any accidents.

So yea,yesterday was more or less; Troubleshoot monitor,discover...
diyAudio Member
Posted in Uncategorized
Views 1218 Comments 3 DigitalJunkie is offline
Old

Time for a new Digital Crossover - ADAU1442

Posted 2nd April 2012 at 02:29 PM by googlyone

Well, it has been a few years since I built my last digital crossover - like six I think.
It is not that I was planning to do this - but a conversation with someone about my seemingly modest choice of the AD1941 DSP chip for my old crossover made me look at what else Analog Devices are offering.
The ADAU1442 is on the surface a very similar chip to the AD1940, but it has a lot more integrated into it, and offers significantly greater capacity.
So I set about designing a new crossover that used this, and also addressed a few of the shortcomings of my original design.
The goals were broadly:
- A modular DSP based crossover
- That provides a standard interface for the ADC
- That provides a standard interface for the DAC
- That includes SPDIF in and out
- That anybody can design digitisers and dacs for - no code level drivers built in, though the interface does ALLOW for SPI control of these
- That is controlled from a simple...
Attached Thumbnails
Click image for larger version

Name:	DSC03601-small.jpg
Views:	1839
Size:	194.2 KB
ID:	636   Click image for larger version

Name:	DSC03604-small.jpg
Views:	2053
Size:	257.5 KB
ID:	637   Click image for larger version

Name:	DSC03615-small.jpg
Views:	3383
Size:	300.7 KB
ID:	638   Click image for larger version

Name:	DSC03624-small.jpg
Views:	1245
Size:	257.6 KB
ID:	639  
Attached Files
diyAudio Member
Posted in Uncategorized
Views 6218 Comments 7 googlyone is offline
Old

Headphone Amplifier Gain

Posted 2nd April 2012 at 09:45 AM by rjm (RJM Audio Blog)
Updated 2nd April 2012 at 12:43 PM by rjm

I posted this earlier today, but I think it deserves to be put in the blog - if nothing else so I can find it again next time ... and there always seems to be a next time when it comes to calculating headphone amplifier gains.

Starting at the beginning, the encoded data on a CD goes from 0 to 1 in 2^16 steps, but in a typical CD player or soundcard, the DAC output is -2.8 V to 2.8 V or 2 V rms or 6 dB. Many sources, such as phono stages and portable audio, are lower, perhaps as low as 250 mV.

How loud the sound is depends on the source signal amplitude, the position of the volume control, the circuit gain, and the impedance and sensitivity of the headphones.

As a practical matter, most people would want the volume control at the 9-10 o'clock position for "normal" listening.

For standard "line level" source, the gain required to keep the volume control at a 9-10 o'clock varies depending on the impedance...
Attached Thumbnails
Click image for larger version

Name:	headphone sensitivity.png
Views:	737
Size:	25.9 KB
ID:	635  
Attached Files
rjm's Avatar
rjm
diyAudio Member
Views 4087 Comments 2 rjm is offline
Old

Pimp My Board Contest Results

Posted 31st March 2012 at 01:20 PM by rjm (RJM Audio Blog)
Updated 31st March 2012 at 01:28 PM by rjm

I did get a couple of responses to my invitation. Well, two, actually.

So congratulations! Free boards will be heading your way in about a month, and I'll throw in most if not all the parts, too.

First was simonov's entry. He's clearly done this several times before. His confident layout ticks all the right buttons: ground plane (check), thermal isolation (check), clean, geometric layout (check). One jumper required, but that's a very minor offence.

Click the image to open in full size.

While I allowed modifications of the circuit, simonov went and redesigned pretty much the whole thing. CCS replaces the source resistor, current limiter and capacitance multiplier blocks added. The BOM was starting to spiral, and no longer uses my standard parts set so I'd have difficulty supplying kits based on his design. His modifications, although certainly improvements, ended up counting against him....
rjm's Avatar
rjm
diyAudio Member
Views 1312 Comments 2 rjm is offline
Old

Conduction Angle, Or Why You Need a Bigger Power Transformer Than You Think You Need

Posted 29th March 2012 at 05:35 PM by rjm (RJM Audio Blog)

I tell people: "Buy a nice, heavy power transformer. It will sound better."

They are skeptical, because the circuit only draws a couple of watts, and less than 100 mA current.

The image below shows how the power transformer, and rectifier diodes, actually work much harder than you would estimate from looking at the output power.

It shows a zener regulated supply with a load drawing 100 mA at 20 V. That's 2 W.

As a result of the capacitor input filter directly after the diodes, however, the diodes and transformer do not conduct current all the time, but instead for just a couple of milliseconds twice every cycle of the AC wave. They have to supply all the output current in just that short space of time. As you can see in the simulation, the diodes are pushing peak currents well in excess of 1A or 10x the output current. This is a typical "normal" power supply with a initial ripple ratio of a modest 1/40, things...
Attached Thumbnails
Click image for larger version

Name:	jmo2 ps conduction angle.png
Views:	1354
Size:	63.1 KB
ID:	633  
Attached Files
rjm's Avatar
rjm
diyAudio Member
Views 2446 Comments 11 rjm is offline
Old

Why do some chip amps / gainclones sound so bad? (updated 2012-03-30)

Posted 29th March 2012 at 05:56 AM by dunndatt
Updated 31st March 2012 at 01:23 AM by dunndatt (clarification fix)

Years ago when getting started into DIY audio, I picked up three different chip amps from my local electronics shop. They were cheap and easy enough to build according to the data sheets, so I had a go at them. To my dismay, they sounded HORRIBLE! I couldn't figure out what went wrong until I really started digging into the data sheets.

While I didn't build the LM3886, I'm going to pick on it since it is a very common chip amp:
National Semiconductor LM3886 (from national.com, bought out by ti.com)
Claims 68watts into 4ohm speakers with 0.1% THD+N from 20-20kHz

National did pretty good with most of their claims, but I'll focus on something that stands out: The Distortion Vs. Power graphs. (As a comparison, I discovered that one of my other chip amps did their power testing at 10% distortion... which is pitiful. Every chip amp data sheet I've looked at has some kind of failing with this graph.)

Click the image to open in full size....
Attached Thumbnails
Click image for larger version

Name:	lm3886_DistortionVsPower.png
Views:	12585
Size:	30.8 KB
ID:	629   Click image for larger version

Name:	lm3886_SMPTEvsPower.png
Views:	2870
Size:	31.4 KB
ID:	630   Click image for larger version

Name:	lm3886_SMPTEvsPower2.png
Views:	2977
Size:	31.3 KB
ID:	631  
Attached Files
File Type: pdf LM3886.pdf (852.4 KB, 302 views)
diyAudio Member
Views 2427 Comments 4 dunndatt is offline
Hide this!Advertise here!

New To Site? Need Help?

All times are GMT. The time now is 08:44 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