Cheap 100 to 150 Watt Amp

[AndrewT]

..............Looking at just the resistive load, I thought there was a lot of room to push more power through an 8-Ohm load. But the reactive load line says it ain't so.

exactly !
However you manufacturer usually gives a good guide to short term overload tolerance. The 100ms, 10ms, 1ms, 100us, 10us SOA allow much higher currents provided the overload is short term and is not a repetition of similar signals. They are one shot guarantees of performance when Tc=25degC

I'll look at B9

 

[Buckeye]

Right, but the DC SOA is good enough for me. The kind of amps I work with are sometimes driven to clipping continuously without regard to low or high frequencies. It's not your typical audiophile environment where the user has the sense to turn it down when it sounds bad.

Pingr's post I'm talking about is here:

http://www.diyaudio.com/forums/grou...mp-pcb-group-buy-interest-64.html#post2364365

It's only been 5 1/2 years so I'd expect everyone to have this fresh in their minds.

 

[AndrewT]

The B9 cell that Pingrs is referring to is, I think, in Bob Ellis' spreadsheet.
It is certainly not a reference to Bensen's sheets.

 

[wg_ski]

The kind of amps I work with are sometimes driven to clipping continuously without regard to low or high frequencies.

True, but in those applications amps won't see anythig worse than 1.4+j0 or 0+j4 ohms, even driving two of the nastiest, dual driver cabs you can dig up on each channel. If it does distort (limit) on a few-millisecond-long signal into a 0.5+j2 ohm load its going to be so buried in the distortion from clipping on everything else that no one will ever notice.

 

[Buckeye]

I couldn't find a spreadsheet from Bob Ellis. Instead I found your mention of 3 spreadsheets you modified from Ether's work, but couldn't find the spreadsheets themselves. Are these the same as what Pingrs posted? If not, can you please link me to them?

 

[Pingrs]

I couldn't find a spreadsheet from Bob Ellis. Instead I found your mention of 3 spreadsheets you modified from Ether's work, but couldn't find the spreadsheets themselves. Are these the same as what Pingrs posted? If not, can you please link me to them?

Andrew,

Thanks for stepping in here in my absence.

Buckeye,

Cell B9 (=SQRT(B7/B5)) is indeed in Bob Ellis's Load Line spread sheet, http://www.diyaudio.com/forums/grou...mp-pcb-group-buy-interest-64.html#post2305042

In Michael Kiwanuka's excellent article, a method of calculating the resistor values from points on a given protection plot was proposed. I revised his method so that given values would result in a protection plot of sorts; manipulating those values then gave a desired result-no calculations required to achieve Michael's "Transparent VI limiter". Another reason was that calculations often ended up with odd value resistors requiring series/parallel combinations. Here one can specify E series values.

While Michael's article is copyright, I remember him being so exasperated with the publisher's many errors that he offered to post a corrected version to those who wanted it at the time, but that was a few years ago.

My contribution to this thread was thus to show this method of relatively easily determining the component values for a VI limiter, with your particular case as an example. The Bensen spreadsheet, as you say, makes no mention of VI limiting-it was never intended as such, but it does serve a vital purpose (along with the SOAR's) in showing the limits within which to place a protection plot.
I plotted the load lines and SOAR limits on a linear basis, rather than the log-log used in Eather and Bensen's work, but the calculations are substantially the same, so I didn't think I needed to repeat them, hence why they weren't included.


Brian.

 

[Buckeye]

OK, thanks. Could I please get a sample of your MASTER sheet?

 

[jspayneco]

Circuit brd layout with mods for "Cheap 150 Watt Amp"

I have created a layout of this 150 watt amplifier circuit (page one of this thread) and a PDF of the foil/bottom is available. It has provision for decoupling capacitors, gain reduction at high frequency caps, Universal mount/pinout for the TIP output transistors, and improved biasing. It is located at 150 Watt Power Amplifier Circuit Board.

If you wish to email me, I am at: pcb(at)jspayne.com for comments or criticism.

Regards

Stephen Payne