diyAudio - General Comments
Go Back   Home > Forums > Blogs > rjm

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
General Comments My soapbox.
Old

Bypassing, Goldilocks, and the Sound of Nothing

Posted 31st May 2012 at 06:28 PM by rjm
Updated 1st June 2012 at 11:53 PM by rjm

Douglas Self writes,
Quote:
The 5532 and 5534 type op-amps require adequate supply decoupling if they are to remain stable, otherwise they appear to be subject to some sort of internal oscillation that degrades linearity without being visible on a normal oscilloscope. The essential requirement is that the positive and negative rails should be decoupled with a 100 nF capacitor between them, at a distance of not more than a few millimeters from the op-amp; normally one such capacitor is fitted per package as close to it as possible.
He's someone who should know. Anyway, it doesn't take much digging on the internet to confirm beyond reasonable doubt that bypass caps should be as close to the op amp power pins as possible. So thinking about my previous experiments with bypassing the Sapphire, by adding bypass caps around the transistors I also effectively also added a bypass for the op amp, but a rather poor one as the power-pin-to-power-pin round trip loop distance is probably 10...
Attached Thumbnails
Click image for larger version

Name:	DSC_1366 1280 hack.jpg
Views:	711
Size:	313.9 KB
ID:	696   Click image for larger version

Name:	pcb-sapphire-14s1-brd-bypass.png
Views:	1627
Size:	40.6 KB
ID:	697  
rjm's Avatar
rjm
diyAudio Member
Views 1944 Comments 0 rjm is online now
Old

Headphone Amplifier Gain

Posted 2nd April 2012 at 08:45 AM by rjm
Updated 2nd April 2012 at 11:43 AM 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:	497
Size:	25.9 KB
ID:	635  
rjm's Avatar
rjm
diyAudio Member
Views 3168 Comments 2 rjm is online now
Old

My system (Jan 2012)

Posted 23rd January 2012 at 12:12 PM by rjm
Updated 26th January 2012 at 02:57 AM by rjm

Biggest changeover in many years.

Denon DP-2000, DA-307, DL-103 turntable/tonearm/cartridge
Phonoclone 3 with 160 VA Plitron power supply
47 Labs "Treasure" model 0247 preamplifier
47 Labs "Treasure" model 0347 amplifier
Onkyo D-605SR speakers
Cables by oyaide, mostly.
(photo: Pentax K10D, Pentax FA 31mm F1.8 AL Limited)
Attached Thumbnails
Click image for larger version

Name:	IMGP1552j 1280.jpg
Views:	1304
Size:	369.4 KB
ID:	580  
rjm's Avatar
rjm
diyAudio Member
Views 1251 Comments 0 rjm is online now
Old

Five-times-bandwidth

Posted 3rd January 2012 at 04:44 PM by rjm

If we accept that conventional wisdom that the audio bandwidth extends from 20 Hz to 20 kHz, a good rule of thumb for the f(-3 dB) high and low cutoff points of the frequency response of each audio circuit element is 5x the bandwidth, or 4 Hz to 100 kHz. In practice most designs tend to shift that range a little to the higher frequencies, so perhaps 5 Hz - 200 kHz, or 4 - 250 kHz.

Personally I "tune" my circuits to 4 Hz. That is, the time constants are adjusted to about 4 ms. Capacitance is usually cheap enough to go even longer, but the influence on sonics is typically net negative.

The high frequency side is more interesting, since many circuit elements naturally run into the megahertz range, the the question is do you actively try to prevent that, and if so, where and how?

The biggest issue is bypassing: a small value electrolytic (100 uF) is probably fine up to 100 kHz or so, but quite useless at 2 Mhz. The textbook solution is...
rjm's Avatar
rjm
diyAudio Member
Views 578 Comments 0 rjm is online now
Old

The cost of hi-end audio: is it worth it?

Posted 20th December 2011 at 05:16 AM by rjm
Updated 20th December 2011 at 05:30 AM by rjm

Having recently actually bought some new (not used, not my own design, and relatively expensive) audio gear, and from 47 Labs no less, the following question has been occupying my thoughts of late:

How much would you pay to not have a component installed in the audio equipment you buy?

The traditional price scheme for audio equipment is [BOM-times-X], where BOM is the cost of the parts used to make it, and X is a multiple to cover fabrication and distribution costs, as well as profit for the various parties involved. My understanding is that for consumer audio "X" is about 4, though companies with strong brand recognition can get away with higher multiples. And do.

The basic problem is this: how much it costs to build and how good it sounds are not the same thing. There is some correlation: a large, high quality transformer is pretty much guaranteed to improve the sound quality, but for the rest, stuffing a pretty box with many cheap...
rjm's Avatar
rjm
diyAudio Member
Views 1147 Comments 3 rjm is online now
Hide this!Advertise here!

New To Site? Need Help?

All times are GMT. The time now is 07:26 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2015 DragonByte Technologies Ltd.
Copyright 1999-2015 diyAudio

Content Relevant URLs by vBSEO 3.3.2