Project 11.1 from Slone "High-Power Amplifier" Book - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

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 July 2008, 08:22 PM   #1
Karl71 is offline Karl71  United States
diyAudio Member
 
Join Date: Mar 2007
Default Project 11.1 from Slone "High-Power Amplifier" Book

Does anyone have experience with the "11.1" project from the Randy Slone book, "High-Power Audio Amplifier Construction Manual"? It is the first and simplest amplifier in Ch. 11. What is the wattage? Can it handle a minimum load of 2.5 Ohms presented by an e-stat? Slone says early on that all of the amps in the book will drive a 2 Ohm load, but only temprarily. The nominal load is 6 Ohms.

BTW, I love the book. I like his approach and design philosophy. I am anxious to get building.

Regards,

Karl Lewis
  Reply With Quote
Old 4th July 2008, 08:53 PM   #2
diyAudio Member
 
nigelwright7557's Avatar
 
Join Date: Apr 2008
Location: Carlisle, England
Default Re: Project 11.1 from Slone "High-Power Amplifier" Book

Quote:
Originally posted by Karl71
Does anyone have experience with the "11.1" project from the Randy Slone book, "High-Power Audio Amplifier Construction Manual"? It is the first and simplest amplifier in Ch. 11. What is the wattage? Can it handle a minimum load of 2.5 Ohms presented by an e-stat? Slone says early on that all of the amps in the book will drive a 2 Ohm load, but only temprarily. The nominal load is 6 Ohms.

BTW, I love the book. I like his approach and design philosophy. I am anxious to get building.

Regards,

Karl Lewis
Most amps will drive a 2 ohm load so long as you dont turn them up too far. Too low a laod takes too amny amps from the amp power supply before max volts is reached.

I often play my amp into 1ohm but dont turn it right up.
__________________
PCBCAD50 software. http://www.murtonpikesystems.co.uk
  Reply With Quote
Old 5th July 2008, 02:00 AM   #3
expert in tautology
diyAudio Member
 
bear's Avatar
 
Join Date: Apr 2002
Location: New York State USA
Hi!

Not sure if this is the amplifier book I remember with that sort of name or not... if it is the same one, avoid! Otoh, it may be a different one.

Perhaps if you post the schematic, people could make intelligent comments, or unintelligent comments about it.

Generally speaking, if the driver can handle enough current, you can increase the number of outpoot devices, and so be able to run more current into your load.

In order to run a lower Z load you need to run more current into the load. Take the power supply rail and figure out what the current requirement into the load impedance will be, then work backwards to look at that SOA of the outputs... then you will know the answer to your question for any specific amplifier.


_-_-bear
__________________
_-_-bear
http://www.bearlabs.com -- Btw, I don't actually know anything, FYI -- [...2SJ74 Toshiba bogus asian parts - beware! ]
  Reply With Quote
Old 5th July 2008, 02:20 AM   #4
diyAudio Member
 
Join Date: Sep 2002
Location: Sweden
The 11.1 is a simple amp intended as a beginners project. It has 50 V rails and a single pair of 2SJ162/2SK1058. The max Id rating of those is 7 A, which you reach already at 14 V output for a 2 Ohm load. Obviosly you could reach several times the max Id with that rail voltage. You could lower the rail voltage to maybe 20 V (which is probably safe considering Vgs and other losses) or use parallel output devices as Bear suggested, but it is hardly worth it for a simple amp that not even the author thinks is very good.
  Reply With Quote
Old 5th July 2008, 03:01 AM   #5
Karl71 is offline Karl71  United States
diyAudio Member
 
Join Date: Mar 2007
Nigel -

That's what I have read. I don't intend to run the 'stats very loud. The 2.5 Ohm impendence occurs at around 12 KHz.

Bear -

Why should I avoid the book? I've read past posts regarding Slone's works, and I know that there are conflicting opinions regarding his positions and designs. What are your objections?

Christer -

So, do you think I could use the 11.1 amp with the 'stats? The builder told me that Rotels, Adcoms, and NAD units have had no trouble with his panels. Would a higher power design in the Slone book be more appropriate in this application?

Thanks to everyone so far for your imput. Keep it coming.

Karl
  Reply With Quote
Old 5th July 2008, 11:48 AM   #6
djk is offline djk
diyAudio Member
 
djk's Avatar
 
Join Date: Feb 2001
Location: USA
"max Id rating of those is 7 A, which you reach already at 14 V output for a 2 Ohm load. "

Which is 10V RMS for a whopping 50W at 2 ohms.

For better results, reduce the main supply voltage to like 30V and use a higher voltage like 40V for the front end. It still won't put out any more power, but now it won't be a space heater.
__________________
Candidates for the Darwin Award should not read this author.
  Reply With Quote
Old 5th July 2008, 11:53 AM   #7
diyAudio Member
 
Join Date: Sep 2002
Location: Sweden
And even 30 V rails are enough to make the amp suicidal with a 2 Ohm load, especially since 11.1 is intendend as a very simple project and doesn't have current limiting or any other form of protection.
  Reply With Quote
Old 5th July 2008, 12:33 PM   #8
Did it Himself
diyAudio Member
 
richie00boy's Avatar
 
Join Date: Nov 2003
Location: Gloucestershire, England, UK
I believe that the advice to stay away largely stems from the fact that one of the more complex amps exists in simulation only and if built would blow up on first application of power.
__________________
www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more.
  Reply With Quote
Old 5th July 2008, 01:55 PM   #9
djk is offline djk
diyAudio Member
 
djk's Avatar
 
Join Date: Feb 2001
Location: USA
"And even 30 V rails are enough to make the amp suicidal with a 2 Ohm load,"

If he was driving a regular speaker I might agree with you, and drop the main rail even lower.

The E-stats only drop that low at very high frequecies. With the low program content and high peak-to-avereage ratio up there I think he may be safe.

" especially since 11.1 is intendend as a very simple project and doesn't have current limiting or any other form of protection."

An output fuse and a thermal switch on the heatsink are generally sufficient for lateral MOSFETS.

The Hafler XL-280 used three pair of outputs on 63V main rails with a higher voltage for the front end, it drove 2 ohms quite well. If we cut the V in half the dissipation will be cut by about 75%, so one pair ought to do (with his speakers).
__________________
Candidates for the Darwin Award should not read this author.
  Reply With Quote
Old 5th July 2008, 08:46 PM   #10
expert in tautology
diyAudio Member
 
bear's Avatar
 
Join Date: Apr 2002
Location: New York State USA
I said, IF that is the book I recall...

post the schematic, is what I said??

Anyhow, it is usually difficult to make a silk purse out of a sow's ear?

A better idea might be to start with a project that is known to work for your application? That is one that has sufficient current capability for the power level that you want to run at?

In general terms, ESLs are fabulously low sensitivity speakers, which means in practice that you want to throw the maximum voltage swing you can muster at them.

IF you have an ESL with a dip down to 2 ohms, then you might want to reconsider how you match to them? That might be the reason that you have such a dip? The place for that is in the ESL section here...

But, assuming you are going to need to drive the 2 ohm part, as has been mentioned it only is a big problem if you have to put significant energy there for a while - in terms of blowing up the amp - but in terms of practical listening, you will not like the sound of your amp clipping at all when you run an ESL!! Very annoying, imho.

That's one reason people prefer tubes on ESLs in some situations!

Anyhow there are a number of amps that have been suggested on DIYaudio where people have made up PCBs for the driver part, and there are the Pass designs - some of which will drive 2 ohms all day - and there are known commercial kits that range from blank PCBs to full parts + PCBs and instructions.

For a first ever building project, I'd suggest staying within the range of something that is well known and relatively easy to put the parts together so that it actually works.

The JC-3 amp thread might be worth a look too - or was the JC-2? I get the nomenclature mixed up. Someone made a PCB up for that, and it is a Class A amp that should not mind the low Z load, assuming the proper number of outpoot devices...

These are just some ideas...

Oh, there are also some Opamp based amplifier projects that might work just fine for you! There's an app note that uses a new ultra low distortion opamp as a front end for a power amp: National Semiconductor App Note AN-1645 you probably also want to look at AN-1490 which is referenced in the first one.

No reason that I see that you can't bridge a pair and get substantial voltage swing... and maybe even bias them up into near Class A...

So, P = I^2 R

100 = I^2 2ohms

100/2 = 50 = I^2

= 7 amps


BUT, you want 100 watts (for example) at 8 ohms!
That works out to be 200 @ 4 and then 400w @ 2 ohms!

So let's refigure:

400/2 = I^2 = 14 amps.

Since about a 200w @ 8 ohm amp seems to have about the right voltage swing to run most ESLs, that means even more current available! (whoa!) (but the good part is that some transistors today have ample current and voltage ratings)

Now in practical terms, you're not going to actually pull this current running an ESL, but the ouput devices need to have the SOA so that they do not blow up in use - the ESL looks like a capacitor as a load. (rather reactive, not resistive)

So, the amp also needs to be stable into this load. (important!)

The reason that your ESL is dipping down to 2 ohms is that there is some combination of factors, first the reduction of Z as frequency goes up, and probably in this case (if it dips and comes back up) a resonance of the secondary of the ESL driver transformer with the panel itself (or some other component added in...) causing an impedance dip, and doubtless a phase shift WRT to frequency.

You want an amp that will not blow up or clip before you reach normal listening levels WRT the power level in the majority of the spectrum - which works out to be the voltage swing required when run through the ESL's transformer necessary to deflect the diaphragm sufficiently (on the order of 5kv!). Ok then?

Put another way, to run most ESLs you want an amp with an ample SOA, and that means current capability, PLUS the most voltage swing you can manage - that equation usually means a big, high power amplifier in practice.

_-_-bear
__________________
_-_-bear
http://www.bearlabs.com -- Btw, I don't actually know anything, FYI -- [...2SJ74 Toshiba bogus asian parts - beware! ]
  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
Randy Slone's "Fig 11.4" (Self's "Blameless"?): PCB layout tcpip Solid State 128 23rd September 2013 04:45 PM
What makes an amplifier "bright", "warm", or "neutral"? JohnS Solid State 51 13th December 2009 06:42 PM
Book "Evolve Power Amplifiers" from Shinichi-Kamijo in English ? tiefbassuebertr Solid State 2 13th August 2009 04:22 AM
Randy Slone "Fig 11.6" amp, modded: will work? tcpip Solid State 85 29th May 2007 10:31 PM
"High" THD in Slone Figure 11.4 amp Thoru Solid State 30 13th March 2006 04:01 PM


New To Site? Need Help?

All times are GMT. The time now is 12:58 PM.


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