New amplifier...possibly.. - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps

Chip Amps Amplifiers based on integrated circuits

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
Reply
 
Thread Tools Search this Thread
Old 4th December 2011, 01:28 AM   #1
fooboo is offline fooboo  United Kingdom
diyAudio Member
 
Join Date: Oct 2008
Default New amplifier...possibly..

Hello all

It's been a long while since I was last here. Life has just been too hectic and other projects have been getting in the way.

I have been planning for a long while to have a bash at building my own amplifier. One of the LM38** family in all likely hood. But for my first foray I happen to have a pair of TDA1562Q IC's to hand.

I was going to build a pair of circuits from an Elektor magazine but since starting to dip into the forum again I have come across a couple of slightly different layouts. One is a dual PCB and the other a single, and smaller than the single version I have. This is due to the buffer circuitry of my original choice.

I can make my own PCB's, and have been for about 2 -3 years now. I also have a pair of Kenwood car amplifiers which I am going to gut to free up the ali cases for my project.

I have some rather nice blocks of wood which I fancy turning into the fascia of the unit as well. The internal void of the case will be 100mm H x 210mm W x 170mm D. I am hoping to fit the pair of amps and the single transformer inside but I have to do some research on physical size and form to see if this is feasible.

The ali cases will be fitted base to base probably with a wood fillet between the 2 ends a wooden fascia, as mentioned, and possibly a heat sink filling the rear void. Speaker wise I have a pair from my old Akia Stereo which has resided in storage for about 4 years. Twin tape, triple CD changer, FM radio with surround sound......That never seemed to work IMO. They will do for now I guess but I will move on to making my own speakers at some point.

I hope to etch the PCB's this coming week and have them populated soon after. The PSU may take a little while longer to do. I need a 240V transformer with a pair of secondary windings that can supply 10A tops. This should give enough headroom I hope.

Probably a CD player will be the source either a PC rom drive or an old playstation. Would anyone have a recommendation, if required, as to whether a buffer of some sort between the source and the amp would be advisable?

regards

fooboo
Attached Images
File Type: png Amplifier.png (120.3 KB, 1591 views)
  Reply With Quote
Old 4th December 2011, 07:50 PM   #2
fooboo is offline fooboo  United Kingdom
diyAudio Member
 
Join Date: Oct 2008
Hi There

Going through my component storage, electronic components, I have found an LM3876T I ordered last year from rapid when I first became interested in making my own.

I am placing a small order this week for parts for a pair of voice mods for some American friends so I am going to order a second LM3876T so I am good to go once I have the first project sorted.

I also have some 0.9mm Enamelled copper wire on the way that was for the first design of 1562 amplifier I looked at. As the design I settled on doesn't require the use of this wire to make coils it was redundant.... Except for the fact the LM3876T circuit does require the use of the same wire

My drive for this project is down to an experience I had in my youth. In the audition room of a 'specialist audio shop'. A pair of Mission 761i speakers hooked up to an ARCAM amplifier and CD player. Sleek, very plain and unassuming. Until the familiar first notes of 'BAD', by U2, on the Live under a blood red sky album drifted, apparently out of nowhere. I was, to say the least, transfixed. It's an album I knew inside out but to be able to hear the little details brought into much more clarity than I had ever heard before.

Sadly things went a bit belly up an I never had the funds to buy my dream set up. It also never occurred to me, back then, to build it myself. If I can only build something that performs a 10th as well I my well be happy.

regards

Fooboo
  Reply With Quote
Old 4th December 2011, 08:19 PM   #3
GloBug is offline GloBug  Canada
Banned
 
Join Date: Jun 2011
Well your on the right track, keep at it and keep us posted.
I can't tell you weather or not you need to buffer your input, perhaps someone with more experience can advise on that.

Sounds like a fun project.
  Reply With Quote
Old 5th December 2011, 05:53 PM   #4
diyAudio Member
 
danielwritesbac's Avatar
 
Join Date: Nov 2007
With a non-inverting amplifier, its probably unnecessary to add a buffer.
Also, with a one-piece car bridge chip, its probably unnecessary to add a buffer.

However, you will probably need a 10k potentiometer.
  Reply With Quote
Old 5th December 2011, 07:14 PM   #5
fooboo is offline fooboo  United Kingdom
diyAudio Member
 
Join Date: Oct 2008
Hi there

That sounds fair enough to me and I'm sure I can handle the 10K pot to boot

I've been doodling in sketchup and based on the possible transformer, regulator PCB's and the amp boards I've come up with a slightly different 'concept'.

The proposed enclosure now stands on it's end. Internally the traffo is at the bottom which will help stabilise the unit. Amp boards at the top and regulator boards just under these. The idea being to help keep the AC lines away from the audio IN/OUT. The pot will be fitted as near as possible to the PCB's so a shaft will be needed to connect it to the control knob at the front.

As a minor detail a bulgin anti vandal switch will be used to operate the unit. I'm currently (you see what I did there?) Reading up on traffo's and regulators as the required power will dictate what size traffo I end up with. So long as I can fit it in the proposed case with everything else all will be well.

Now in a lateral bit of thinking I am hoping I can just bolt the chips to the case, as per the original occupant, The walls are very thick and there is a lot of surface area to act as a heat sink.

In a slight sideways step in this convoluted path to home build amp ownership I am getting a PC cdrom audio adapter, after Christmas, to set up a CDROM player for the use of. I saw this idea mentioned on this forum and it sounds good to me!......... I hope it does when it's done!!

A slight fly in the ointment is rapideonline no longer stock the LM3867 So cricklewood will be my next stop off!

regards

Fenris
Attached Images
File Type: jpg AutoSave_Amplifier.jpg (197.1 KB, 1443 views)
  Reply With Quote
Old 5th December 2011, 09:45 PM   #6
diyAudio Member
 
danielwritesbac's Avatar
 
Join Date: Nov 2007
Its TDA1562Q that needs the 10k pot.

The popular National Semiconductor gainclone projects normally use a 20k pot in parallel with a 22k resistor for input load. Its still about 10k to 11k.

You might have a look at Rod Elliot site for the article "a better balance control" which is also an interesting proposition.

And there are also law fake arrangements using a Log pot for its slightly higher accuracy, paralleled with a resistor to cause something very much like audio taper. That makes a cheap pot perform just about like an expensive pot.
  Reply With Quote
Old 6th December 2011, 11:37 AM   #7
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
The vertical orientation will get better performance from the case as a heat dissipater.
This is not a common arrangement, but will work well and will take up less shelf space, since we are not allowed to stack power amps on top of each other.
__________________
regards Andrew T.
  Reply With Quote
Old 6th December 2011, 01:23 PM   #8
fooboo is offline fooboo  United Kingdom
diyAudio Member
 
Join Date: Oct 2008
Hi there

@Daniel - Oh yes for the TDA it is. I've been browsing Rob Elliot's site, an excellent resource, for some time. Coincidently it was the Googling of fake law pots that got me there, months ago, on a different project. I was short of a 10K log pot for a project and learned how to make a linear pot work for the volume control; which it indeed does

@Andrew - Cheers With the layout as is it also gives me a lot of empty space that could be used for any additions to the set up. Selector, buffer, phono pre-amp, soft start, speaker delay. Up to a point I can thicken the wood strips to increase the width of the unit but I wouldn't want to overdo this.

Without the strip spacer the enclosure width is 100mm Ext/90mm Int. The next option adds 10mm and as a maximum option a total of 30mm added. anything beyond this and I think the unit will start to look too squat. I have the minimum of tools to work the aluminium and again for the wood. But I should get by.

The overall size is 284mm H. 170mm D and 100mm, 110mm or 130mm W.

For now I am perusing the forum trying to find the thread that indicated how to work out transformer size based on speaker Ohm/watts and volts..

Onwards and upwards

regards

Fenris
Attached Images
File Type: jpg AutoSave_Amplifier.jpg (45.5 KB, 1316 views)
  Reply With Quote
Old 6th December 2011, 01:42 PM   #9
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Transformer size that offers good $ value for electrical performance is defined very easily as follows:
VA = one to two times the total maximum output power for a ClassAB amplifier.
eg.
two channels each of 60W will play well with a transformer from 120VA to 240VA.
The same amplifier will also play/operate with transformers outside this VA range.

Conditions are: playing all music styles in all domestic situations. PA and Sound Reinforcement and motor driving and all other exceptional duties need a much better model.
__________________
regards Andrew T.
  Reply With Quote
Old 6th December 2011, 03:29 PM   #10
fooboo is offline fooboo  United Kingdom
diyAudio Member
 
Join Date: Oct 2008
Hi Andrew

Thanks for that. I'm looking at a range that starts at 160VA. They are toroidal with a single primary (230VAC) with dual secondary windings. I think given the specs from the PDF, see below, 2 X 15V secondary coils would be the way to go. But I am not sure what Ampere they need to be. The original 1562 circuit I was going to do recommended a 9A minimum. Would that stand for this version as well?

Here's a link to the document for easier reference -

50+ watts from a 12 V battery.pdf - File Shared from Box - Free Online File Storage

Measurement results (at Ub=14.4 V)
Supply voltage - 8–18 V
Sensitivity - 760 mV r.m.s.
Input impedance - 70 kΩ
Power output - 54 W r.m.s. into 4 Ω (f=1 kHz; THD+N=1%)
Harmonic distortion (THD+N) - at 1 W into 4 Ω: 0.046% (1 kHz)
0.29% (20 kHz) - at 35 W into 4 Ω: 0.12% (1 kHz)
0.7% (20 kHz) - Signal-to-noise ratio (with 1 W into 4 Ω)
88 dBA
Power bandwidth
7.5 Hz – 185 kHz (at 25 W into 4 Ω)
Quiescent current
about 135 mA (‘on’)

I am also thinking of running the PSU side of the circuit as a 'snubberised' type rather than fully regulated.

regards

Fenris
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Simple 200 watt complimentary FET amplifier (possibly tube driver?) deltavektor Solid State 6 15th May 2011 07:15 AM
Possibly Fried Alpine MRV-F352 5 channel Car Amplifier lickwid Car Audio 19 2nd March 2009 04:34 AM
Help! What could possibly be wrong? sonata149 Tubes / Valves 22 9th May 2008 06:30 PM
2 x TC2+ 15" subwoofers for sale (possibly 4) and mint Crown K2 amplifier taloyd Swap Meet 6 4th May 2007 03:30 PM


New To Site? Need Help?

All times are GMT. The time now is 03:39 AM.


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