Pepping up a Silicon Chip SC480 audio amplifier - Page 2

Do you have a question? Post it now! No Registration Necessary

Translate This Thread From English to

Threaded View
Re: Pepping up a Silicon Chip SC480 audio amplifier
Quoted text here. Click to load it

Hi Phil,

sorry my lousy ISP wont support ABSE. email me, and I'll send you a scan.

Cheers
Terry

Re: Pepping up a Silicon Chip SC480 audio amplifier
finger to keyboard and composed:

Quoted text here. Click to load it

http://us1.webpublications.com.au/static/images/articles/i302/30285_4mg.jpg

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

Re: Pepping up a Silicon Chip SC480 audio amplifier
Quoted text here. Click to load it

Thanks, Franc!

Cheers
Terry

Re: Pepping up a Silicon Chip SC480 audio amplifier
Quoted text here. Click to load it

Here it is:
http://us1.webpublications.com.au/static/images/articles/i302/30285_4mg.jpg

Dave.

Re: Pepping up a Silicon Chip SC480 audio amplifier



Quoted text here. Click to load it

Well, you of all people should know about stability issues which will affect
how high it goes.

The typical limiting devices are the output transistors. What are they ?

Also you could reduce the open-loop gain and close the loop at the same
gain. That should extend the bandwidth if done right because of larger
margins.

Graham


Re: Pepping up a Silicon Chip SC480 audio amplifier
Quoted text here. Click to load it

TIP3055 & TIP2955. I downloaded the data sheets, and the rat bastards at
bourns dont even spec Ft, but with storage times approaching 1us, Im
picking its only a few MHz. sounds like this is, indeed, whats gonna
stop me.

Quoted text here. Click to load it

didnt think of that. email me & I'll send you a copy of the schematic -
audio amps sure aint my speciality.

Cheers
Terry


Quoted text here. Click to load it

Re: Pepping up a Silicon Chip SC480 audio amplifier



Quoted text here. Click to load it

You bet. They're as fast as slugs on mogadon.


Quoted text here. Click to load it

Oh the email in my headers works fine.

Graham


Re: Pepping up a Silicon Chip SC480 audio amplifier



Quoted text here. Click to load it

**If you want high frequencies, then build a MOSFET amp.


--
Trevor Wilson
www.rageaudio.com.au



Re: Pepping up a Silicon Chip SC480 audio amplifier
Quoted text here. Click to load it

Jaycar didnt have one

Cheers
Terry

Re: Pepping up a Silicon Chip SC480 audio amplifier



Quoted text here. Click to load it

**You could be right. Altronics have them.


--
Trevor Wilson
www.rageaudio.com.au



Re: Pepping up a Silicon Chip SC480 audio amplifier

"Trevor Wilson"
 "Terry Given"

Quoted text here. Click to load it


** They have one  -  the K5173  200W amp module with psu for $300.

As Given is after a power amp with VHF bandwidth -  I suggest he design his
own.



...   Phil



Re: Pepping up a Silicon Chip SC480 audio amplifier
Quoted text here. Click to load it

I thought about getting this one, but I wasn't certain I could make it
all work, so only spent $50 or so.

Quoted text here. Click to load it

perhaps, one day. doing it properly is a big job, one I am unlikely to
tackle without cash incentives.

in practice 100kHz is a great start (it allowed me to critically damp my
AC & DC filters), and 1MHz is excellent.

at present the SNR degrades significantly above 100kHz, as the output
amplitude rolls off. The analyser does have something like 130dB dynamic
range, and I got good results to 1MHz with a 2,000 second sample time
using 1Hz RBW. it just took half an hour. I can improve that further
still with n-tuple trace averaging, but now we are looking at the best
part of a day to take a single measurement.

So with Phils mods, I ought to get useable results to 10MHz (if I can be
bothered waiting that long), and excellent high-speed results to 1MHz,
which will probably suffice. When I next spark up the HP3577 I'll take
some before-and-after plots, and figure out a way to post them.

thanks all, especially Phil

Re: Pepping up a Silicon Chip SC480 audio amplifier



Quoted text here. Click to load it

**Indeed. 200MHz is a bit of a stretch for an audio product.


--
Trevor Wilson
www.rageaudio.com.au



Re: Pepping up a Silicon Chip SC480 audio amplifier



Quoted text here. Click to load it

May not actually be that fast. Remember gate capacitance. You need a beefy
driver stage to get them moving quickly as Terry will surely already know.

Graham


Re: Pepping up a Silicon Chip SC480 audio amplifier



Quoted text here. Click to load it

Not even necessary with Toshiba bipolars.

Graham


Re: Pepping up a Silicon Chip SC480 audio amplifier
Quoted text here. Click to load it

any suitable part numbers?

and yeah, I knew the xx55's were slow as all hell.

I havent done my power-bandwidth tests yet, but my small signal
bandwidth is now 0-10MHz, which is good enough for a lot of what I have
to do.

If I can get 1W@1MHz I'll be doing well indeed.

I sent you a pretty picture, too.

Cheers
Terry

Re: Pepping up a Silicon Chip SC480 audio amplifier
Wierd Terry!
My newreader parsed the 1W@1MH as an email address. I guess it must do that
with all something@somethings.   Looks like it...

Quoted text here. Click to load it



Re: Pepping up a Silicon Chip SC480 audio amplifier
Quoted text here. Click to load it

LOL

Re: Pepping up a Silicon Chip SC480 audio amplifier

"Terry Given"
Quoted text here. Click to load it


** If you want wide power bandwidth, then lateral mosfets are the clear
winners.

Eg, Hitachi 2SK176 / 2SJ56  or the similar Semelab BUZ 901/6  devices.

Main reason is lack of charge storage in the C-B junction means they turn
off so much faster ( circa 50nS ) you avoid the cross conduction disaster at
high slew rates.

Also, these mosfets self protect at high chip temperatures, " throttling
back " instead of simply blowing up.

http://www.magnatec-uk.co.uk/pdf/magnatec/BUZ900.pdf



.....   Phil





Re: Pepping up a Silicon Chip SC480 audio amplifier



Quoted text here. Click to load it

Straight off the top of my head no and I don't have a Toshiba Data book
here although I may have in pdf form. Their 'audio' power devices vary if
fT from 10-40 Mhz. Sanken do some fast ones too IIRC.

Hah - from a QSC schematic, 2SA1943 and 2SC5200 (widely used) are good for
30 MHz and plenty of volts and amps.

Can post in abse

Graham


Site Timeline