It is currently Sat Aug 19, 2017 3:47 am

Click the link below to visit the site sponsor

The Ham Radio Shop




Post new topic Reply to topic  [ 71 posts ]  Go to page Previous  1, 2, 3, 4, 5
 Sick of over priced extention speakers from the big three. 
Contributor 2017
User avatar

Joined: Tue Oct 09, 2012 1:09 pm
Posts: 7550
Location: West Midlands
Feedback: 82 (100%)
Reply with quote
Post Re: Sick of over priced extention speakers from the big thre
Out of interest, why not a PNP Darlington? (obviously the others and the capacitors etc would have to be changed too)

_________________
===================
Gee Three Eee Jay Ess
===================


Wed Aug 02, 2017 7:42 am
Profile Send private message

 Sick of over priced extention speakers from the big three. 
Advanced Member
User avatar

Joined: Sat Jan 23, 2016 7:24 am
Posts: 769
Location: Blackpool. IO83lu
Feedback: 4 (100%)
Reply with quote
Post Re: Sick of over priced extention speakers from the big thre
Sangoma wrote:
Out of interest, why not a PNP Darlington? (obviously the others and the capacitors etc would have to be changed too)



Just using what I have and I just don't think it would be necessary for what I'm playing with at the moment. I have a BD675 from the first amp, but I'll need two for this. The only other Darlingtons I have are TIP137s and as they use body diodes... probably will end in tears :)

_________________
https://www.qrz.com/db/G0SLV


Thu Aug 03, 2017 6:58 am
Profile Send private message

 Sick of over priced extention speakers from the big three. 
Advanced Member
User avatar

Joined: Sat Jan 23, 2016 7:24 am
Posts: 769
Location: Blackpool. IO83lu
Feedback: 4 (100%)
Reply with quote
Post Re: Sick of over priced extention speakers from the big thre
Time for an update:

Ok.. totally abandoned the class A design. Too power hungry.... problems with parasitic oscillations... impossible to control bias properly... it was a mess.

I've gone for class B, but with careful consideration of biasing to minimise crossover distortion.

Designed this amp from the ground up. I've simulated it in LTSpice, and it looks good. THD of 0.04 at 6 watts into 8 Ohms. Total power RMS should be around 7 watts.

Built on breadboard. Works well!

Attachment:
ertherthetr.jpg
ertherthetr.jpg [ 207.24 KiB | Viewed 112 times ]


Designed a new board for it.

Because the design reminds me of the old amps you used to get in 70s audio equipment, TVs, Radios etc, I thought I'd give it an appropriate name :)

Attachment:
345g345g3.jpg
345g345g3.jpg [ 165.8 KiB | Viewed 112 times ]


I need to change the driver transistors named on the board. They are now BD139/BD140s.

The design is working really well. Doing around 7 watts RMS with 24v feeding it.

Attachment:
34563456345346.jpg
34563456345346.jpg [ 214.9 KiB | Viewed 111 times ]


I love it when you design something from the ground up and it works. Great feeling.

_________________
https://www.qrz.com/db/G0SLV


Fri Aug 11, 2017 11:10 pm
Profile Send private message

 Sick of over priced extention speakers from the big three. 
Advanced Member
User avatar

Joined: Sat Jan 23, 2016 7:24 am
Posts: 769
Location: Blackpool. IO83lu
Feedback: 4 (100%)
Reply with quote
Post Re: Sick of over priced extention speakers from the big thre
OK. Some updates finally. (Been busy)

The above board was revised once more. Not due to any flaws, but because I've been tinkering and made the amplifier more powerful. Basically, I've reconfigured and adjusted it for 30V, so now it's a full fat, 10 watts RMS. As a result I thought it prudent to move the finals off the board (with their small heatsinks) and mounted them on a separate, larger heatsink.

I've been soak testing it... and abusing it, all morning, and it hasn't put a foot wrong.... utterly flawless, and sounds fantastic!

Amplifier on test....

Attachment:
_DSC9747s.jpg
_DSC9747s.jpg [ 174.32 KiB | Viewed 60 times ]


Here's a shot of the finished amplifier board. Very pleased with it. It sounds utterly fantastic. I started out just wanting a reasonably powerful amplifier adequete for communications use, but this redesign in a properly hi-fi capable amp.. albeit at 10 watts, but that 10 watts is RMS, so it's punchier than you would imagine.

Attachment:
_DSC9750s.jpg
_DSC9750s.jpg [ 214.3 KiB | Viewed 60 times ]


One final job remains before starting on the enclosure building, is a new PSU needs to be built. Not a big deal as PSUs are easy, but now it's a beefier amplifier, the original PSU is getting very warm. If it gets warm in open air, it will get hot in a sealed box. I'm redesigning it with a LM338 instead of a LM317, so should run cool.

I'll update the thread as progress on the rest of the build as it happens, but the electronic part is pretty much done. I'll upload pics of the new PSU, but after that, it's carpentry time.

_________________
https://www.qrz.com/db/G0SLV


Thu Aug 17, 2017 12:59 pm
Profile Send private message

 Sick of over priced extention speakers from the big three. 
Contributor 2016
User avatar

Joined: Mon Aug 18, 2014 3:50 pm
Posts: 2541
Location: IO95DA Newcastle Upon Tyne
Feedback: 14 (100%)
Reply with quote
Post Re: Sick of over priced extention speakers from the big thre
Nice work Dave, maybe if you get time a short video of the amp in action?

I spent a reasonable length of time sourcing a suitable internal speaker for my SSB transceiver project and settled on a 2.5" driver from RS Components, was not cheap and came in at £12 but is very good build quality and has a decent frequency response.
I have yet to design the AF Power amplifier but will probably settle on a TDA2030 or similar for the small footprint, I will be driving this with a low noise NE5534 pre-amp after the product detector.

You should publish this design in PW and RADCOM, nice size project for most HAM's to tackle.

Rob.


Thu Aug 17, 2017 1:06 pm
Profile Send private message WWW

 Sick of over priced extention speakers from the big three. 
Advanced Member
User avatar

Joined: Sat Jan 23, 2016 7:24 am
Posts: 769
Location: Blackpool. IO83lu
Feedback: 4 (100%)
Reply with quote
Post Re: Sick of over priced extention speakers from the big thre
I've stripped it all down now Rob, as that was just temporary wiring. I'll do a video when it's finished, as it will sound much nicer when the drivers are in the enclosure.

Thanks :)

_________________
https://www.qrz.com/db/G0SLV


Thu Aug 17, 2017 1:39 pm
Profile Send private message

 Sick of over priced extention speakers from the big three. 
Advanced Member
User avatar

Joined: Sat Jan 23, 2016 7:24 am
Posts: 769
Location: Blackpool. IO83lu
Feedback: 4 (100%)
Reply with quote
Post Re: Sick of over priced extention speakers from the big thre
2E1IIP wrote:
I spent a reasonable length of time sourcing a suitable internal speaker for my SSB transceiver project and settled on a 2.5" driver from RS Components, was not cheap and came in at £12 but is very good build quality and has a decent frequency response.
I have yet to design the AF Power amplifier but will probably settle on a TDA2030 or similar for the small footprint, I will be driving this with a low noise NE5534 pre-amp after the product detector.


Yep.. the TDA2030 is a robust little thing. Makes more sense than building a discreet component amp. I just wanted to do so as a project. In your case, it makes much more sense to use an on-chip solution.


David

_________________
https://www.qrz.com/db/G0SLV


Thu Aug 17, 2017 1:58 pm
Profile Send private message

 Sick of over priced extention speakers from the big three. 
Contributor 2016
User avatar

Joined: Mon Aug 18, 2014 3:50 pm
Posts: 2541
Location: IO95DA Newcastle Upon Tyne
Feedback: 14 (100%)
Reply with quote
Post Re: Sick of over priced extention speakers from the big thre
G0SLV wrote:
2E1IIP wrote:
I spent a reasonable length of time sourcing a suitable internal speaker for my SSB transceiver project and settled on a 2.5" driver from RS Components, was not cheap and came in at £12 but is very good build quality and has a decent frequency response.
I have yet to design the AF Power amplifier but will probably settle on a TDA2030 or similar for the small footprint, I will be driving this with a low noise NE5534 pre-amp after the product detector.


Yep.. the TDA2030 is a robust little thing. Makes more sense than building a discreet component amp. I just wanted to do so as a project. In your case, it makes much more sense to use an on-chip solution.


David

My issue is space Dave, I am constrained by the dimensions of the equipment enclosure I have bought (gonna be close)
I want to magnetically shield the speaker, do you know of an easy way to achieve this?


Thu Aug 17, 2017 2:04 pm
Profile Send private message WWW

 Sick of over priced extention speakers from the big three. 
Advanced Member
User avatar

Joined: Sat Jan 23, 2016 7:24 am
Posts: 769
Location: Blackpool. IO83lu
Feedback: 4 (100%)
Reply with quote
Post Re: Sick of over priced extention speakers from the big thre
I've never needed to do this Rob, so I'm not sure. Some speakers are supplied already shielded though. I'm sure there'll be tons of stuff on t'internet though :)

_________________
https://www.qrz.com/db/G0SLV


Thu Aug 17, 2017 3:00 pm
Profile Send private message

 Sick of over priced extention speakers from the big three. 
Advanced Member
User avatar

Joined: Sat Jan 23, 2016 7:24 am
Posts: 769
Location: Blackpool. IO83lu
Feedback: 4 (100%)
Reply with quote
Post Re: Sick of over priced extention speakers from the big thre
Just finished testing the new PSU. Works perfectly, from 3v to 30v and can deliver 3 amps before the LM338 gets too warm. With a bigger sink, it will do 5 amps easy, but it only needs to provide just over 1 amp, so will remain cool, even when inside the speaker enclosure. A 33v Zener is used in conjunction with the SCR, so it crowbars at that voltage.

It's less than half the size of the first one.

Forgive the rat's nest of wires - they're just for testing. The LED will be removed when fitted too, as the speaker's power LED will be linked directly to the transformer secondary winding via a diode. Reason being, using the board's LED means it stays on a while after switch off due to the smoothing cap discharging.

Nice little build.

Attachment:
_DSC9752.jpg
_DSC9752.jpg [ 166.85 KiB | Viewed 21 times ]

_________________
https://www.qrz.com/db/G0SLV


Fri Aug 18, 2017 8:44 pm
Profile Send private message

 Sick of over priced extention speakers from the big three. 
Contributor 2016

Joined: Wed Nov 28, 2012 2:43 pm
Posts: 4883
Location: Cumbria IO94iv
Feedback: 21 (100%)
Reply with quote
Post Re: Sick of over priced extention speakers from the big thre
A work of art and very well built.


Fri Aug 18, 2017 9:09 pm
Profile Send private message
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 71 posts ]  Go to page Previous  1, 2, 3, 4, 5


Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  
Powered by phpBB © phpBB Group.
Designed by Vjacheslav Trushkin for Free Forums/DivisionCore.