Leach Super Amp Regulated supply - diyAudio
Go Back   Home > Forums > Amplifiers > Power Supplies

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 17th February 2005, 10:22 PM   #1
LBHajdu is offline LBHajdu  United States
diyAudio Member
 
Join Date: Feb 2002
Active regulation is a pain. It introduces so many more parts and not just passive ones. So there are more things to go wrong. So unless in actually improves the sound itís probably not worth it. Mark Levinson is a fan of active regulation, as you can see form there boards.

If we do want more backend regulation, other options are:
1)
Making the second C in the CRC network that exists now bigger. This CRC network was always an interesting thing to me. When the amp comes online the 10ohm resistors sees a short until the cap has some charge. For that brief moment in time the 10ohm resistor could have as much as 6A across it. Thatís 360watts from a half watt resistor. I realize that the time of this serge is very short, but still this is well over the short term overload. This is why Iím afraid the raze this cap form 100uF to 1,000 or 2,000uF. I would like to understand how to calculate rated wattage for the resistor in DC RC networks. Also I see that Jens has moved the RC network back leaving one more stage unprotected, I donít know what the logic was behind this.

2)
We could move up to a CLC filter AKA pi filter. I have seen some post where people have said that this makes thing sound worst, so maybe this is not a good idea. Iíll let others decide.

3)
One could use a separate small transformer to drive the back end. This is most likely the best way.

4)
Bryston uses a similar CRC as the leach but with a zener diode to ground. This keeps the voltage constant, however there is a 30V voltage drop across the regulator.

There are more ways of doing regulation all Jens has the do is not connect the back and the front end, just leave a jumper incase people donít want the regulation. Does anyone have a comment on any of these forms of regulation, or any that I have not stated? All but number 4 are passive regulation.
  Reply With Quote
Old 17th February 2005, 11:04 PM   #2
Mikett is offline Mikett  Canada
diyAudio Member
 
Join Date: Aug 2003
Location: Toronto
In 1983, I took my Leach Monoblocks (Lower Power version) and compared them to another Leach amp that was built dual mono with large toroids >500VA per channel and with similar quality parts.
My regulated amp only sported 300VA hammond standard core with a couple of radio shack 12V@6amp booster transformers.

There was simply no comparison. The unregulated amplifier sounded positively undynamic in comparison. It was very apparent in kickdrums and really low bass transients. In the highs, the regulated amp seem to have more clarity. Yes, we checked the stability of both amps with scopes etc.

To prove that the power supply was the core of the differences, we disconnected his power supply and jumpered my regulator outputs to his amplifier boards. Now his amps sounded similar to mine.

Within a week, owner quickly retrofitted a front end only regulation using lifted discrete regulators ( I think 317/337) and while it had improved a bit, the fully regulated amp was still clearly superior. Needless to say, he had another project that converted his amp to full regulation.

A similar comparison was made with the super leach with similar results. Yes, on paper full regulation of the ouput appears to be unnecessary but close listening proves otherwise. PSRR etc. will say otherwise but the differences exist. Is it worth the extra effort and resources? It depends on what you desire. If you want that extra "kick" for dynamics. Higher wattage may NOT necessarily give that to you. Maybe the lower power version fully regulated might be better from a resource/parts standpoint.

Yes, regulation is very much more complex and requires a supply that can pass very high current transients but remember that a "super" amp is being contemplated.
  Reply With Quote
Old 18th February 2005, 12:44 AM   #3
diyAudio Member
 
BrianDonegan's Avatar
 
Join Date: Dec 2004
Location: TPA HQ
Hmm. So maybe another requirement will be a regulated power supply for the redesign. That sounds (ha ha) like it might be a real improvement. There are designs out there, let pick one and target a voltage to this application.

Agree/disagree?

The Super Regulated Leach
__________________
Twisted Pear Audio
  Reply With Quote
Old 18th February 2005, 05:16 AM   #4
Mikett is offline Mikett  Canada
diyAudio Member
 
Join Date: Aug 2003
Location: Toronto
Here's what might be interesting. In 1983, the regulator used was the one that was designed by James Boak in Amateur Audio. The core of this design was a current split arrangement with a three terminal LM-340T. ( Eeegads..... that's correct- the LM340T) . More modern 3 terminal devices likely will improve that design but the point is that even with such "old" devices there were easily audible improvements to be had over a simple power supply.

More recently ( loosely termed) about four years ago I decided to update some equipment I had built earlier. Where I had Sulzers, I put in Jung Super regulators, and the Sulzers displaced 3 terminal supplies.
Again each improvement in PS led to superior audio quality that was not too subtle at all.

I can only imagine what a good power amp with an up to date fast regulator would sound like!!!!!!!!

Who's up to that challenge?
  Reply With Quote
Old 18th February 2005, 07:32 AM   #5
diyAudio Member
 
jacco vermeulen's Avatar
 
Join Date: Oct 2004
Location: At the sea front, Rotterdam or CuraÁao
Send a message via Yahoo to jacco vermeulen
Just a reminder:
normal regulation for a 1000 VA toroid is about 5 %
Put 120 vac on a 55 volt transformer for 110 vac and secondary voltage will be 60 volts.
With zero load voltage will increase with the 5 % : 63 volts.
I believe the measured voltage on the toroid transformer Terry bought at Ebay with zero load was a bit over 63 volts.

For the high voltage:
With the regulation of Terry's transformer a 125 V cap or higher would be needed, but a small one is enough, say 1000uF.
150 volt caps are expensive, 75 volt caps not.
Two 1000uF capacitors placed in series are equal to one 150 v cap.
In series the internal resistance of 2 caps in series is doubled.
As Bob Ellis mentioned, the current the regulator needs to deliver is not that high, esr for the regulator caps is not that important.

The regulator on Mr Thagard's A75 is a nice one, adapting it to the voltage used is easy.
I have been a huge fan of Mark Levinson builds, every ML amplifier is a piece of art.
A good example of ML regulation is the model 23, or 23.5
The 23 uses extensive regulation for the front end of the amplifier, a transformer with multiple voltage secondaries and separate powersupplies.
Pictures of it are plenty around on the web, at the French ML club, i can scan pictures of the model 23 brochure and post if you like.
__________________
The buck stops Here
  Reply With Quote
Old 18th February 2005, 08:19 AM   #6
diyAudio Member
 
jacco vermeulen's Avatar
 
Join Date: Oct 2004
Location: At the sea front, Rotterdam or CuraÁao
Send a message via Yahoo to jacco vermeulen
Front end voltage does not need much more voltage than the output stage for continuous output with BJT's, voltage level is 1.41 times dc level anyway.

Transistors have a linear behavior within a range, a device often operates in class A, only a part of the current through the device can be used for voltage swing to avoid getting in the non-linear area.
And then it may be better to have a little slack on the voltage swing.
Front ends may have current stages to collect enough current for the next gain stage.
A current stage lowers max voltage swing.
On a Pass single ended amplifier thread NP mentioned a few weeks ago that he prefers to have some 5 volts headroom because that improves the sound quality of the design.

If there is sufficient voltage from the power supply, as Terry has on his transformer, putting some more voltage on the front end is not a bad thing.
Many of the designs with separate voltages for front and output stages, that i have seen, have a much higher voltage difference than just a few volts.
Designs that have voltage regulations for the front stage often have voltage levels considerably higher too.
A diesel engine operates on 90 % max continuous rating.
It can be used on 100 % constantly, usual is to keep 10 % slack.

As Mr Ellis said, regulators need heatsinks.
An easy regulator can be built with a lifted LM317/337 by raising the reference voltage on the regulator pin.
This can be done because the current the regulator will deliver is much lower than the maximum the LM's can handle.
Higher voltage drop induce higher dissipation, proper heatsinks are very important.
Usually an amplifer chassis has ample room for placing a few small regulator boards with heatsinks.
Discrete regulators are much better, i do not disagree with that.
I am a firm believer in stable power supplies.
__________________
The buck stops Here
  Reply With Quote
Old 18th February 2005, 09:16 AM   #7
Villaw is offline Villaw  Cyprus
diyAudio Member
 
Join Date: Feb 2005
Location: Ni
ok boys, lets have some examples of regulator topologies to see what we may be facing here. If we can accomodate the regulator on the same board then the extra hassle would be minimal and the advantages great.
__________________
Nick
  Reply With Quote
Old 18th February 2005, 12:25 PM   #8
diyAudio Member
 
kilowattski's Avatar
 
Join Date: Aug 2003
Location: Long Island, New York
The regulated power supply in figure 7 of the following Nelson Pass article is easily modifiable for this purpose by changing the zener diode values and the number of paralleled pass elements. The curcuit is simple and effective and has a low parts count. Why reinvent the wheel. Of course, because of the power required, a pretty good heat sink will be needed but that will be true of any linear power supply utilized with this amp. The other alternative is a SMPS which has other concearns.



Pass Active Supply Regulation
__________________
-----------------------------------------------
Kilowattski
  Reply With Quote
Old 18th February 2005, 12:28 PM   #9
LBHajdu is offline LBHajdu  United States
diyAudio Member
 
Join Date: Feb 2002
Mikett,
I have never even considered total amp regulation. However, if it makes the huge improvement you claim, then it may well be worth it. Your claims do sound to be very conclusive. If it does not then I will be stuck with a transformer with higher rail voltage then I wish to use. Has anybody had similar observations? Could you post a schematic of your regulator and some pictures of your amp?

There arenít to many schematics on line for total amp regulators, at these powers. I have found two possibilities. One is a circuit by Anthony Holton. Heís the one that built the really good sounding N-channel amp about a year ago, it was really popular. The only problem with it was it kept on exploding. It has good PSRR. However the circuit an only supply about 200 watts max, the schematic is almost unreadable, itís not very well documented, and the parts are very difficult to pick up in the US. Here is a link:
http://www.aussieamplifiers.com/regulated.htm

The other option is a Pass regulator using mosfets for the power stage. Itís PSRR is not very good and the circuit has to be scaled up a little. But the circuit is so simple, that it is very easy to do. Right now it would be my preferred regulator. A schematic can be found at:
http://www.passdiy.com/projects/zenv3-6.htm
  Reply With Quote
Old 18th February 2005, 01:07 PM   #10
EJ is offline EJ
diyAudio Member
 
Join Date: Jun 2002
Location: PA
Quote:
Originally posted by kilowattski
The regulated power supply in figure 7 of the following Nelson Pass article is easily modifiable for this purpose by changing the zener diode values and the number of paralleled pass elements. The curcuit is simple and effective and has a low parts count. Why reinvent the wheel. Of course, because of the power required, a pretty good heat sink will be needed but that will be true of any linear power supply utilized with this amp. The other alternative is a SMPS which has other concearns.



Pass Active Supply Regulation
I've always thought that the power supply regulator of Mr. Pass is not suitable for this purpose.
If the current draw from the output of the regulator is not constant, the output voltage will also variate since the Vgs of the mosfet in the regulator will variate with the current through it.
For an amp that does not draw constant current from the PSU, I think what we need for regulating is a circuit with some feedback.
  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
Leach Super Amp Power Supply ComradeConrad Solid State 12 5th May 2008 12:42 AM
Leach amp - regulated supply only for the voltage gain stages? velicko Solid State 2 21st January 2008 11:16 AM
Super regulated power supply peranders Power Supplies 25 29th November 2005 05:40 AM
Power supply for Super Leach amp supernet Solid State 5 6th June 2002 11:53 AM
Power supply for Super Leach amp supernet Solid State 6 23rd March 2002 09:11 PM


New To Site? Need Help?

All times are GMT. The time now is 11:56 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