diyAudio - Blog Entries
Go Back   Home > Forums > Blogs

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

2,000W into 1 ohm

Posted 12th February 2014 at 04:10 AM by fas42
Updated 12th February 2014 at 09:55 PM by fas42

I mentioned in a thread a while ago about doing an exercise of engineering an amp capable of delivering 2k watts into a 1 ohm load, with distortion aiming at the magical ppm figure. This is still happening, and making progress ... key problem as I saw it was managing crossover distortion intelligently - I'm looking at a conventional class AB output stage at the moment - and it didn't make sense to try and control it using a classic global negative feedback approach.

By nature I'm an excellent scavenger, I look to see what ideas are already out there - so I'm trying out some concepts in using local negative feedback. This is evolving, step by step - and showing promise: in a simulation of the output stage only, getting effectively 2kW in 1R, at 200kHz with reasonable stability - and the waveform at this stressful frequency looks pretty good, there is still some crossover glitching, but I'm reducing the visible level of it steadily.
fas42's Avatar
diyAudio Member
Posted in Tweaking
Views 638 Comments 14 fas42 is online now
Old

Code for dual channel DDS...

Posted 25th January 2014 at 01:37 PM by googlyone
Updated 26th January 2014 at 05:34 AM by googlyone (Incomplete)

I was asked if I would share the code for the audio DDS I was playing with.

It is here...

Ver0.1.zip

I think this is all the files you need.

To show just how lazy I am, the main function is the file titled "dig_cross.c" - as that was the main function I edited as the base of this code. There is also a file "ad1940.c" which contains a bunch of the SPI stuff. This is yet another illustration of my bone idle-ness - as this module is probably a decade old. It is used, but has nothing to do with an AD1940 IC....

No apologies

There is a bunch of comments in this, but some general overview comments are:
- About 95% of the source code is about:
- Running the user interface
- Generating the display (rather utilitarian implementation)
- Reading from the EEPROM, and doing limit checks on data
- Writing to EEPROM

...
diyAudio Member
Posted in Uncategorized
Views 343 Comments 0 googlyone is offline
Old

Next generation Ozone analog stage - 'free radical'

Posted 25th January 2014 at 01:28 AM by abraxalito
Updated 6th February 2014 at 03:49 AM by abraxalito

Last night I finished building the second channel of my dual mono approach to DAC building which I've called 'free radical'. Here's a picture of the second channel's build just prior to adding all the crapacitors (cheap shanzai 'Sanyos' which measure extremely well). While building the second channel I was listening to the first in mono and that was a spur to quick completion

From left to right there's the AD605 with its top hat array of MLCCs - outputs are isolated via ferrite bead chokes from the AD8017 under its own pile of SMT ceramics. In between the two active stages are the capacitors associated with power supply reference voltage filtering. I realized from the previous build that as the AD605's gain is controlled by DC voltages, these voltages need to be low noise to ensure gain stability. Hence lots of RC filtering with those Nichicon and Rubycon low ESR lytics. I'm using BC817 transistors as low drop-out regulators and the reference voltages (2.5 and 5.7V) come...
Attached Thumbnails
Click image for larger version

Name:	free radical.JPG
Views:	228
Size:	672.2 KB
ID:	1229  
abraxalito's Avatar
diyAudio Member
Views 582 Comments 7 abraxalito is offline
Old

Voltage Regulators for Line Level Audio. Part V : Graduation Day

Posted 20th January 2014 at 03:32 AM by rjm
Updated 20th January 2014 at 10:21 PM by rjm

Part five of a series.

Last time, we'd got to a functional voltage regulator, with a pass transistor and op amp error amplifier but I cheated and used ideal voltages for the reference and op amp power supply.

This time I've sketched out a functional circuit using real parts found in the LTSpice library. I've chosen a rail-to-rail op amp to avoid problems with low voltage references. The LT1009 reference puts out 2.5 V, the op amp gain is 4, for an output of 10 V into 1 kohms.

Two versions of the circuit are included below. Voltageregulator5 has some additional RC filter stages to remove noise from the reference and op amp power supply Voltageregulator5b just takes everything straight from the input voltage. As you can see there's a fairly substantial advantage gained from judicial use of RC filtering.

So that's the end of Term 1. The basics have been covered, however briefly. I encourage you to download the LTSpice files and play...
Attached Thumbnails
Click image for larger version

Name:	voltageregulator5.png
Views:	285
Size:	61.6 KB
ID:	1226  
Attached Files
File Type: asc voltageregulator5.asc (2.8 KB, 124 views)
File Type: asc voltageregulator5b.asc (1.9 KB, 106 views)
rjm's Avatar
rjm
diyAudio Member
Views 481 Comments 0 rjm is offline
Old

Voltage Regulators for Line Level Audio. Part IV : The Error Amplifier

Posted 18th January 2014 at 06:05 AM by rjm
Updated 20th January 2014 at 10:21 PM by rjm

Part 4 for a series.

At the end of Part 3 I promised to introduce feedback, and I will, but what we are really talking about here is the addition of the error amplifier, the heart of all modern series pass regulators. The error amplifier is a non-inverting DC signal amplifier, and its function is simple: amplify and buffer the reference voltage. The twist is that the amplifier output is connected to the base of the pass transistor, while the feedback connection is taken from it’s emitter. The pass element is thus placed inside the feedback loop of the error amplifier, improving the ripple rejection and output impedance of the regulator dramatically.

So here we are, the three building blocks of a voltage regulator are in place: the reference voltage, the error amplifier, and the pass device. In the LTSpice circuit I’ve cheated, deliberately, in order to make the operation easier to follow. Instead of building a practical voltage reference I’ve...
Attached Thumbnails
Click image for larger version

Name:	voltageregulator4.png
Views:	195
Size:	43.1 KB
ID:	1223   Click image for larger version

Name:	voltageregulator4b.png
Views:	169
Size:	41.9 KB
ID:	1224  
Attached Files
File Type: asc voltageregulator4.asc (1.9 KB, 102 views)
rjm's Avatar
rjm
diyAudio Member
Views 505 Comments 0 rjm is offline
Old

Voltage Regulators for Line Level Audio. Part III : The Z-reg

Posted 17th January 2014 at 04:35 AM by rjm
Updated 20th January 2014 at 10:21 PM by rjm

Part 3 of a series.

I’m going to have to make a detour to point out what we are doing here is learning how these circuits work, and get a very rough idea of their relative merits. We’re not trying to minimize the output impedance, or maximize the ripple rejection. Three reasons immediately come to mind for why it would be bad practice to try and do that:

1. Any such contest will be easily won by the largest capacitor placed on the regulator output.

2. There are clear limits on these parameters after which further “improvement” is unlikely to serve any useful purpose.

3. There are other considerations such as the output noise of the regulator and the stability under dynamic loads, which are equally if not more important.

Clear? No cookies for the “most bestest” circuit in LTSpice. The great utility of LTSpice is it allows you, the designer, to easily check if you’ve left performance...
Attached Thumbnails
Click image for larger version

Name:	voltageregulator3.png
Views:	224
Size:	95.2 KB
ID:	1220   Click image for larger version

Name:	voltageregulator3b.png
Views:	194
Size:	97.5 KB
ID:	1221   Click image for larger version

Name:	LM317.png
Views:	131
Size:	37.2 KB
ID:	1222  
Attached Files
File Type: asc voltageregulator3 (zreg).asc (1.7 KB, 112 views)
rjm's Avatar
rjm
diyAudio Member
Views 638 Comments 0 rjm is offline
Old

Triton One speaker unveiled at CES

Posted 17th January 2014 at 02:45 AM by abraxalito
Updated 17th January 2014 at 02:57 AM by abraxalito

Just for a change from DACs, here's a speaker which caught my eye.

http://www.avsforum.com/t/1511825/go...ne-at-ces-2014

Now how much of its improved SQ over rivals three or more times the price is going to be down to the active bass section offloading the most PSU-draining signals from the driving poweramp? The comments about the scale of the soundstage do reflect the kinds of improvements I've been getting by reducing LF noise in my DAC, so the reduced LF noise from the poweramp from having a more benign load to drive could indeed be key. 92dB efficiency certainly helps a lot in reducing poweramp PSU stress.

That article says this speaker is 'sure to shake up the industry'. Really? What do you guys think?
abraxalito's Avatar
diyAudio Member
Posted in Uncategorized
Views 597 Comments 17 abraxalito is offline
Old

Voltage Regulators for Line Level Audio. Part II : The Pass Transistor

Posted 16th January 2014 at 04:14 AM by rjm
Updated 20th January 2014 at 10:21 PM by rjm

Part 2 of a series.

Instead of pulling the output current through R1, we add an npn pass transistor, Q1. The output current now "passes" through the transistor, while the Zener diode still regulates the output voltage by being connected to the transistor base.

The output impedance falls to a few ohms, but the ripple rejection improves only slightly.

This is a useful basic circuit block for audio, but the ripple rejection can easily improved by the addition of a couple of additional components, as we'll see shortly.
Attached Thumbnails
Click image for larger version

Name:	voltageregulator2.png
Views:	208
Size:	90.6 KB
ID:	1217   Click image for larger version

Name:	voltageregulator2b.png
Views:	146
Size:	92.7 KB
ID:	1218  
Attached Files
File Type: asc voltageregulator2.asc (1.2 KB, 110 views)
rjm's Avatar
rjm
diyAudio Member
Views 395 Comments 0 rjm is offline
Old

Voltage Regulators for Line Level Audio. Part I : Zeners

Posted 15th January 2014 at 11:34 PM by rjm
Updated 16th January 2014 at 04:40 AM by rjm

This is the first of a series, where I will be investigating the output impedance and ripple rejection of various voltage regulator circuits using LTSpice.


Today, for the first "lesson" (I'm teaching myself, as much as anything) we will look at the very simple zener voltage regulator.

The load is 1 kohm, and the Zener breakdown voltage is 12 V. The load current is about 10 mA, and to avoid gross inefficiency we will limit the current flowing through the Zener to about 5 mA, by adjusting R1 accordingly. The input voltage is fixed at 18 V.

To measure the ripple rejection, we perform an AC analysis with the voltage source AC set to 1 and the current source AC set to zero. The ripple rejection is the negative value of the signal at Vout: so -20 dB means 20 dB ripple rejection (1 V ripple at Vin generates 0.1 V ripple at Vout at a given frequency.).

To measure the output impedance, again the AC analysis function is used but...
Attached Thumbnails
Click image for larger version

Name:	voltageregulator1.png
Views:	175
Size:	92.9 KB
ID:	1213   Click image for larger version

Name:	voltageregulator1b.png
Views:	141
Size:	92.6 KB
ID:	1214  
Attached Files
File Type: asc voltageregulator1.asc (1.1 KB, 101 views)
rjm's Avatar
rjm
diyAudio Member
Views 432 Comments 0 rjm is offline
Old

A "music cafe", Kyoto.

Posted 13th January 2014 at 09:45 PM by rjm

A small corner of audio heaven, for anyone willing to pay the 500 yen cover charge.
Attached Thumbnails
Click image for larger version

Name:	DSC_3842 1000.jpg
Views:	188
Size:	209.9 KB
ID:	1212  
Attached Files
rjm's Avatar
rjm
diyAudio Member
Views 311 Comments 0 rjm is offline
Hide this!Advertise here!

New To Site? Need Help?

All times are GMT. The time now is 10:15 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