|
Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets. |
|
Thread Tools |
21st Nov 2019, 3:11 pm | #41 | ||
Dekatron
Join Date: Jul 2007
Location: Evesham, Worcestershire, UK.
Posts: 4,241
|
Re: Mullard Audio Circuit
Quote:
But voltage efficiency as a goal is the pointless bit. Did that once when I was still at school - talk about a lesson in decibels learnt the hard way! I did once consider building a Texan, but by that stage I'd already done a lot of my own designs and had decided to keep away from projects in the magazines, as some of them were really quite iffy in my experience thus far. Random aside: Douglas Self did an amplifier based on a 32 NE5532s in parallel - no output transistors!. 16 watts per channel into 8 ohms at extremely low distortion, from +/-18.3V rails. Meant as a bit of fun, but interesting nonetheless |
||
21st Nov 2019, 9:49 pm | #42 |
Nonode
Join Date: Jun 2016
Location: Bognor Regis, West Sussex, UK.
Posts: 2,288
|
Re: Mullard Audio Circuit
This talk about the Texan reminded me that many yaers ago we had a group project in our spare time at work, we were all building identical amplifiers and bulk buying the components.
The design was similar to the Texan in that it used op-amps, 741s I think, driving transistor output stages but was unusual in that it used filters to split the signal into low, mid and treble frequencies and amplified them separately to drive the tweeter, mid range and woofer speakers rather than splitting the signal with crossovers in the speaker. I seem to recall the design was from chip a manufacturers application note. Does anyone recall what the design might have been? Peter |
21st Nov 2019, 10:47 pm | #43 |
Dekatron
Join Date: Nov 2010
Location: Oxford, UK.
Posts: 4,942
|
Re: Mullard Audio Circuit
That was probably earlier than Siegfried Linkwitz's first active crossover system design in WW 1978, May, June and December. That used TL072 op amps. I built it in about '79 or '80.
Siegfried was designing and refining the active crossover concept until not long before he died at 82. I personally use his final and greatest design, the LX521. https://www.linkwitzlab.com/ Craig |
21st Nov 2019, 10:56 pm | #44 | |
Dekatron
Join Date: Nov 2010
Location: Oxford, UK.
Posts: 4,942
|
Re: Mullard Audio Circuit
Quote:
Nelson Pass has upstaged Self by building a power amp with several thousand complementary discrete JFET buffers in parallel http://www.firstwatt.com/pdf/art_beast.pdf Craig |
|
22nd Nov 2019, 2:49 am | #45 |
Hexode
Join Date: Mar 2018
Location: Bishop Auckland, County Durham, UK.
Posts: 373
|
Re: Mullard Audio Circuit
A fascinating thread. Just a thought, was there any clever audio circuitry employed in the "slab" type of STK output chips that were popular in the 80s and 90s?
__________________
Regards Martin |
22nd Nov 2019, 9:48 am | #46 | |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,803
|
Re: Mullard Audio Circuit
Quote:
David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done |
|
22nd Nov 2019, 2:07 pm | #47 |
Dekatron
Join Date: Nov 2010
Location: Oxford, UK.
Posts: 4,942
|
Re: Mullard Audio Circuit
There is a very poor and often out of focus You Tube video of the internals of an STK here https://www.youtube.com/watch?v=m6DbeIy51tU
Seems to be a combination of conventional circuit board, thick film and discrete. This one was ripped open because (surprise surprise) it had blown up. Craig |
22nd Nov 2019, 11:37 pm | #48 | |
Octode
Join Date: Feb 2009
Location: Bletchley, Buckinghamshire, UK.
Posts: 1,205
|
Re: Mullard Audio Circuit
Quote:
I didn't build it, but I've no doubt that tri-amping would have enabled the three, rather low-powered, amplifiers to punch well above their weight. |
|
23rd Nov 2019, 9:46 am | #49 | |
Nonode
Join Date: Jun 2016
Location: Bognor Regis, West Sussex, UK.
Posts: 2,288
|
Re: Mullard Audio Circuit
Quote:
I think you have hit the nail on the head. I think I have been confusing the Texan with the triple SL403 project. I am pretty sure now that it was the Texan we built, I remember one of us testing and matching the ouput transistors into pairs and thinking back we each got 4 for a stereo pair not 18. Back to the triple SL403 it would only give a sigificant increase in power if the sound to be reproduced was evenly distributed across the spectrum otherwise one channel would have to handle the lions share and that would limit the available power. Peter |
|
23rd Nov 2019, 2:20 pm | #50 |
Octode
Join Date: Jan 2007
Location: Dorridge, West Midlands, UK.
Posts: 1,475
|
Re: Mullard Audio Circuit
The SL403 article using 3 ICs was in Practical Electronics Dec 1969 on by M J Gay of Plessey.
It can be found here if you're interested. https://www.americanradiohistory.com...cs-1969-12.pdf I played around with several of these modules and ICs in the late 60s building stereo amps for mono record players for friends.
__________________
Chris Wood BVWS Member |