Hi
Greetings, on a rarher cold, but sunny Monday morning. I figure that as this forum is my first read every morning, I may as well stop lurking around as a guest and actually register. I might even get around to posting one or two questions, and hopefully will be able to contribute to one or two of the very enthusiastic debates.
Most of my experience is in the field of PA audio. Although with the price of commercial equipment these days, HiFi may well be the way to go especially if I ever want to own that 5.1 theatre at home.
Just picked up a 100MHz dual timebase scope from work. Now I just need to get through the Exams so some real development can begin.
My biggest problem. Choosing ONE project and FINISHING it before starting the next one.
Anyway, wishing you all well
Cheers,
Stuart
Greetings, on a rarher cold, but sunny Monday morning. I figure that as this forum is my first read every morning, I may as well stop lurking around as a guest and actually register. I might even get around to posting one or two questions, and hopefully will be able to contribute to one or two of the very enthusiastic debates.
Most of my experience is in the field of PA audio. Although with the price of commercial equipment these days, HiFi may well be the way to go especially if I ever want to own that 5.1 theatre at home.
Just picked up a 100MHz dual timebase scope from work. Now I just need to get through the Exams so some real development can begin.
My biggest problem. Choosing ONE project and FINISHING it before starting the next one.
Anyway, wishing you all well
Cheers,
Stuart
Hi again,
I'm busy with the following:
Phono preamp (done prototype)
Complete preamp
Headphones amp (done prot.)
Power amp
Integrated amp
All these in very little time in betweens...
Problem - enclosures (metal for electronics and wooden for speakers).
AP has them ugly and I can't find a normal carpenter (my hands are both left, so boxes look bad).
Idea/suggestion - we meet sometimes and start something like a DIY Hi-Fi in Joburg, maybe it grows into something interesting?
And, after successful project:
Jack
I'm busy with the following:
Phono preamp (done prototype)
Complete preamp
Headphones amp (done prot.)
Power amp
Integrated amp
All these in very little time in betweens...
Problem - enclosures (metal for electronics and wooden for speakers).
AP has them ugly and I can't find a normal carpenter (my hands are both left, so boxes look bad).
Idea/suggestion - we meet sometimes and start something like a DIY Hi-Fi in Joburg, maybe it grows into something interesting?
And, after successful project:
Jack
Unfortunately, my curent project list is endless.
At the moment Im looking at building:
1 remote controlled microprocessor based preamp
2 A couple of gainclones, just for the fun of it.
3 100 - 150 W PA power amp.
4 DTS transciever for the PS2.
5 Pair of simple bookshelf speakers
6 Small hometheatre subwoofer (probable disguised as a side table)
7 A really decent HiFi rack (aka. big, heavy and asthetically pleasing)
etc.......
As you say time is a big issue. Im currently at WITS business school, doing some part time studying.
I have just found a supplier of flat packed 19" aluminium cases in Springs, and am busy investigating. There is also a toroidal transformer manufacturer in Booysens. Last time I looked their prices were pretty good!
Im with you on the Diy HI-Fi idea!
Ill try to get in touch with you later in the week. Assignment due for this evening, and I havent really started.
Cheers, Stuart
At the moment Im looking at building:
1 remote controlled microprocessor based preamp
2 A couple of gainclones, just for the fun of it.
3 100 - 150 W PA power amp.
4 DTS transciever for the PS2.
5 Pair of simple bookshelf speakers
6 Small hometheatre subwoofer (probable disguised as a side table)
7 A really decent HiFi rack (aka. big, heavy and asthetically pleasing)
etc.......
As you say time is a big issue. Im currently at WITS business school, doing some part time studying.
I have just found a supplier of flat packed 19" aluminium cases in Springs, and am busy investigating. There is also a toroidal transformer manufacturer in Booysens. Last time I looked their prices were pretty good!
Im with you on the Diy HI-Fi idea!
Ill try to get in touch with you later in the week. Assignment due for this evening, and I havent really started.
Cheers, Stuart
Hi, Jack (oops!) and Stuart
I notice you guys are building amps. I have some PCB's available for Douglas Self -style Load Invariant amplifier. If you're interested, contact me.
Stuart:
Please share with us your findings on the 19" rack and the transformers.
My work buys toroidals from W. Gardner (sp?) somewhere out your way in Gauteng (possibly Jo'burg).
I notice you guys are building amps. I have some PCB's available for Douglas Self -style Load Invariant amplifier. If you're interested, contact me.
Stuart:
Please share with us your findings on the 19" rack and the transformers.
My work buys toroidals from W. Gardner (sp?) somewhere out your way in Gauteng (possibly Jo'burg).
Hi guys (Shaun, Stuart)
I know someone who knows someone else who manufactures toroidals, but I am currently dealing with a guy who makes EI types, and some C cores. Prices very reasonable, like 100VA is about R100, etc. Springs is 10km from where I work, so I could go and check the racks...
What does D. Self amp. looks like? Complicated? Where can I check the diagram?
Keep up the good work, we'll stay in touch.
Jack
I know someone who knows someone else who manufactures toroidals, but I am currently dealing with a guy who makes EI types, and some C cores. Prices very reasonable, like 100VA is about R100, etc. Springs is 10km from where I work, so I could go and check the racks...
What does D. Self amp. looks like? Complicated? Where can I check the diagram?
Keep up the good work, we'll stay in touch.
Jack
Here are some pictures of an earlier version of my PCB:
http://users.pandora.be/airborne/blameless.html
The diagram is not complicated; in fact the circuit topology is very common. Sorry that the following image is not of good quality.
These guys also sell a PCB for the Load Invariant amp (£30):
http://www.signaltransfer.freeuk.com/invariant.htm
I'm asking $25 for mine.
Read a bit about Self's work on distortion in power amps:
http://www.dself.dsl.pipex.com/ampins/dipa/dipa.htm
Regards
Shaun
http://users.pandora.be/airborne/blameless.html
The diagram is not complicated; in fact the circuit topology is very common. Sorry that the following image is not of good quality.
These guys also sell a PCB for the Load Invariant amp (£30):
http://www.signaltransfer.freeuk.com/invariant.htm
I'm asking $25 for mine.
Read a bit about Self's work on distortion in power amps:
http://www.dself.dsl.pipex.com/ampins/dipa/dipa.htm
Regards
Shaun
Attachments
No. That PCB was made by a company that is now defunct (ER Circuits). My latest PCB was made by W.H. Circuit. Trax wanted to charge me more than they originally quoted, and then was not interested in re-negotiating. They generally charge more that other companies. W.H. made a good quality board, and I can't justify paying Trax more for the same thing.
Performance, briefly:
Using 55V rails (16000uF), 160VA transformer/40V not optimal I got 110W/8ohms, 180W/4ohms (transformer was getting nice and warm).
Basic output depends on the supply voltage; performance into 8 ohms vs 4 ohms depends on the beefiness of the power supply. In my case, the transformer was underrated.
Distortion was measured at 0.006% (1kHz, 5.2V output).
Noise -104dB (5.2V output).
Performance, briefly:
Using 55V rails (16000uF), 160VA transformer/40V not optimal I got 110W/8ohms, 180W/4ohms (transformer was getting nice and warm).
Basic output depends on the supply voltage; performance into 8 ohms vs 4 ohms depends on the beefiness of the power supply. In my case, the transformer was underrated.
Distortion was measured at 0.006% (1kHz, 5.2V output).
Noise -104dB (5.2V output).
Local (Gauteng) Transformer & Enclosure Suppliers
Hi guys,
Having joined recently and seeing your discussion around local amplifier component suppliers, I am also keen to establish where the best places to shop are.
My project list is also extensive. I want to build some established designs before approaching my own design. This is partly to gain construction experience (last amp I built was 13 years ago) - Components were a lot cheaper then!.
My medium term goal is a medium power (80Wrms or less) design with a preamp (D Self & Randy Slone as guides). Ideally I would like the preamp to have a digital user interface using the Atmel 8bit risc controller to run the display and select the inputs.
Unfortunately finding affordable toroidal transformers has proven difficult. 300VA was quoted upwards of R700 and from RS in Midrand at R800+. If you do know a supplier for this in the Gauteng region please post the details.
Similarly for enclosures, if you have any good suppliers please post the details. I also bought one from AP (expensive and not quite what I wanted). Communica and the rest don't have anything worth purchasing for a professional look and feel.
With regards to components, Avnett Kopp seems to be the only supplier carrying some of the popular semiconductors used in these designs eg MJ15003/MJ15004 etc.
I would be interested in creating a local knowledge base around suppliers and exchanging info wrt designs.
Hi guys,
Having joined recently and seeing your discussion around local amplifier component suppliers, I am also keen to establish where the best places to shop are.
My project list is also extensive. I want to build some established designs before approaching my own design. This is partly to gain construction experience (last amp I built was 13 years ago) - Components were a lot cheaper then!.
My medium term goal is a medium power (80Wrms or less) design with a preamp (D Self & Randy Slone as guides). Ideally I would like the preamp to have a digital user interface using the Atmel 8bit risc controller to run the display and select the inputs.
Unfortunately finding affordable toroidal transformers has proven difficult. 300VA was quoted upwards of R700 and from RS in Midrand at R800+. If you do know a supplier for this in the Gauteng region please post the details.
Similarly for enclosures, if you have any good suppliers please post the details. I also bought one from AP (expensive and not quite what I wanted). Communica and the rest don't have anything worth purchasing for a professional look and feel.
With regards to components, Avnett Kopp seems to be the only supplier carrying some of the popular semiconductors used in these designs eg MJ15003/MJ15004 etc.
I would be interested in creating a local knowledge base around suppliers and exchanging info wrt designs.
Hello Shannon
Great to see the DIY community in this country becoming more visible. Unfortunately quality components are not all that easy to find here, however they are avaliable. The only component supplier I know of in Pretoria is Communica, although Im sure there are many more.
For toroidal transformers I use W. Gardner and Son Ill look out their details this evening when I get home. They used to charge about R1 per 1VA. Of course that may have changed by now, but Ill bet they are cheaper than RS, and I think they will wind you custom secondaries if you ask.
Enclosures are a constant battle. So far the only ones I have found to be worthwhile come from the industrial racking manufacturers. They normally produce good quality 19' cases. I also tend to build my own from extrusions and items I find lying around, such as my IDE gainclone (built into a stripped cast aluminium casing from an IDE harddrive)
I have started working on a knowledge base for my own use. Ill forward it to you tomorrow. Maybe we should put together an online resource for people to log their favorite suppliers?
regards,
Stuart
Great to see the DIY community in this country becoming more visible. Unfortunately quality components are not all that easy to find here, however they are avaliable. The only component supplier I know of in Pretoria is Communica, although Im sure there are many more.
For toroidal transformers I use W. Gardner and Son Ill look out their details this evening when I get home. They used to charge about R1 per 1VA. Of course that may have changed by now, but Ill bet they are cheaper than RS, and I think they will wind you custom secondaries if you ask.
Enclosures are a constant battle. So far the only ones I have found to be worthwhile come from the industrial racking manufacturers. They normally produce good quality 19' cases. I also tend to build my own from extrusions and items I find lying around, such as my IDE gainclone (built into a stripped cast aluminium casing from an IDE harddrive)
I have started working on a knowledge base for my own use. Ill forward it to you tomorrow. Maybe we should put together an online resource for people to log their favorite suppliers?
regards,
Stuart
A knowledge base is definitely a great idea! Good luck with setting it up.
W. Gardner is definitely cheaper than RS. I think 400VA is around R400 (225VA was about R240). They can also vacuum impregnate the transformer to minimise vibration.
It's best to design & build your own enclosures as per Stuart's recommendation. If you're willing to splash out, you could get some engineering company to make special parts, like grille cutouts in the panels. Even better if you have friends in the industry.
Good luck!
W. Gardner is definitely cheaper than RS. I think 400VA is around R400 (225VA was about R240). They can also vacuum impregnate the transformer to minimise vibration.
It's best to design & build your own enclosures as per Stuart's recommendation. If you're willing to splash out, you could get some engineering company to make special parts, like grille cutouts in the panels. Even better if you have friends in the industry.
Good luck!
Hi Shaun,
Good to see you on the forum. Could you mail me the clearer version of the DS amp version please.
...good to see you changed the current source (original 2 X noisey diodes) of the LTP and VAS stage. Also by removing the diode over the RC feedback close to the non-inverting input you lowered the noise floor substantially. You can better high frequency phase shift effects by adding a 10p cap over your FB resistor.
How is the thermal stability?
(BTW, Douglas' site is offline - strange...)
Any news on the venue for our next meeting?
Cheers,
Stephan (from CT Audio Club)
Good to see you on the forum. Could you mail me the clearer version of the DS amp version please.
...good to see you changed the current source (original 2 X noisey diodes) of the LTP and VAS stage. Also by removing the diode over the RC feedback close to the non-inverting input you lowered the noise floor substantially. You can better high frequency phase shift effects by adding a 10p cap over your FB resistor.
How is the thermal stability?
(BTW, Douglas' site is offline - strange...)
Any news on the venue for our next meeting?
Cheers,
Stephan (from CT Audio Club)
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