| LBHajdu |
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 it’s 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. That’s 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 I’m 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 don’t 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. I’ll 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 don’t 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. |
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| Mikett |
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. |
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| WorkingAtHome |
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 |
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| Mikett |
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? |
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| 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. |
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| 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. |
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| Villaw |
| 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. |
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| 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 |
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| LBHajdu |
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 aren’t to many schematics on line for total amp regulators, at these powers. I have found two possibilities. One is a circuit by Anthony Holton. He’s 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, it’s 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. It’s 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 |
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| EJ |
| 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. |
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| LBHajdu |
I can’t really comment on this as I don’t have the experience. However my guess would be that the zeners hold the Vgs constant, as long as the rail doesn’t drop to low.
There is a quote from Mr. Pass here that doesn’t sound to good:
| quote: | The output impedance of this circuit is fairly low, being the inverse of the transconductance figure of the MOSFET, which for the IRFP240 is about 5 Siemens, which means that the output impedance will be about .2 ohms.
This figure is not particularly great as a regulator, and ordinarily we would look to improve on it, usually by enclosing the regulator transistor in a feedback loop to correct for this variation. If this were a higher power Class B or AB type amplifier, such an output impedance could easily result in one or two Volts of nonlinear distortion signal in the power supply, and this would bleed into the output circuit as distortion.
With a Class A amplifier, we have the advantage that the current draw from the supply is a linear function of the output current, and so no distorted "half waveform" is seen impressed on the supply voltage. This being the case, the importance of the output impedance becomes less, and we can consider using this follower without feedback.
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| Mikett |
My copies of the Boak supply is unfortunately deep in storage right now. However, the aritcles were written in the early 80s in the Audio Amateur. There were a series of articles called "Measuring Power Supply output impedance" or something along those lines. In these articles it was clearly shown that regulation actually reduces measurable distortion as well. The supplies that I used was the final version of the Boak where Walter Jung had recommended some changes that improved output impedance further. What we finally did was to incorporate two boards +,-, into one board that inclluded preregulators.
The heat dissipation and transistor was not a big issue. Why? If you choose a sufficiently "stiff" transformer to begin with, you can minimize the voltage on the pass transistors by running a lower unregulated voltage and minimize the heat produced. Furthermore, since there is also preregulator, the voltages that each of the pass transistors see might be only a few volts. With this you could probably get a modern TO3/multiple palstics that could pass maybe 50+ amps and still easily stay in the SOA. I used the MJ802/4502 and recall that I was good for 50 amps.
Unlike low level signal sections, a fast unstable supply in an amp of this power could have SUPER consequences. That's probably why not many have tackled this sort of thing much. The BOAK we used was proven to be stable over several power amps and that's why I was comfortable to scale it up and use it. But I'm sure it's performance might be laughable today, but you never know.
After this amp, I have not had the desire to build another amp for over twenty years because no significant ideas have come forward.. |
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| Mikett |
| no it was essentially a current boosted 3 terminal reg with a prereg |
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| acenovelty |
ALL-FET Dual low-noise regulator
2x+/-(24-40)V/200mA. Needs 2x(22-32)VAC
ONE 185.00 Euros
The EB-202/254 consists of two dual wide-band, low-noise regulators, using only FETs (JFETs and MOSFETs) as active elements. Maximum input voltage is ±45V and maximum output voltage is ±40V. Maximum output current with 5V input/output voltage difference is ±200mA.
The set-up procedure consists of adjusting the output voltage to the desired value. Connect 2x270 Ohm/5W resistors to the outputs and a DVM across one of the resistors. Connect the appropriate unregulated DC voltage to the regulator (should be approx. 5V higher than the expected output voltage) and check the output with the DVM. Adjust the output voltage to the desired value with trimpots P1/P2. If you have an oscilloscope and/or an audio µV meter, connect them across the load resistors and check the residual hum/noise. The scope should not show any ripple and the µV meter should show less then 5µV of noise over the audio bandwidth. |
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| acenovelty |
| The Walt Jung Super-Regulator |
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| LBHajdu |
acenovelty,
The Walt Jung Super-Regulator may have potential, the Borbely doesn’t it’s basically the same as the Anthony Holton circuit, but with fets and no component values. The maximum output voltage on the Borbely is way to low, and it’s allot of money to pay. You’re pay more for the intellectual property then you are for the board.
At this point the Anthony Holton circuit seems to be the best candidate. As the Pass would need feedback added or many more devices to compensate for the high resistance. The way I understand the problem is that when the amp draws instantaneous current from the regulator the voltage it outputs sags / modulates. To compensate for this the regulator with feedback senses the drop and sends even more voltage through.
Does anyone have more information on the Walt Jung Super-Regulator, the schematic does not talk about max input voltage or max output amps.
Another working circuit can be seen at LCAudio’s web site in the articles section. The only problem again is that the voltage is to low.
Leve |
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| jacco vermeulen |
Maybe Al, the Mighty Mouse, made a proper suggestion, a separate thread for a voltage regulation circuit is more obvious.
I just asked for the possibility of separated lines on the Leach layout.
The first amplifier i heard (of) with full regulation was one by ML.
That amplifier was so stable that a German mag bridged the twins and welded a couple of bras strips together with them.
You could check at MarkLev.com for the regulation circuitry.
Or ask the ML expert here, Mr John Curl, maybe he can give some info on it. The ML20, 1st or 2st ed.
Andre Schmeets in Germany made a couple of designs with simple discrete voltage regulators.
One of his designs can easily be altered for +90 volts operation,
the original is around 80 Volts in.
From memory:
1 BD139/140 and 3 BC546/556, a couple of caps and R's |
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| Damon Hill |
Jung's superregulator in stock form has a maximum output
voltage of 24 volts. I think it would take fundamental
redesign to adapt it for significantly higher voltages.
I'd consider voltage regulation for the pre-driver stages,
or even the driver, but as an outboard solution that could
be wired in separately. It probably would not be difficult
to use a good three-terminal regulator in place of the
existing dropping resistors; I've thought about that for
years but just haven't followed up on it. I'm sure it could
be 'floated' on top of an existing board as there are
only about five or so parts involved, per rail.
Full regulation of the output stages is a lot more ambitious,
equivalent to doubling the complexity of the amplifier, and
adding significantly to dissipation.
I'd have to hear the results to go to that extent in building
a power supply, and would rather go with a switching
supply at any rate. |
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| EJ |
Has anyone tried this?
This circuit, with normal small signal opamps and proper part values, is able to provide regulated voltage of more than +/-100V
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| acenovelty |
| Ryan Power Voltage Regulator. The original design was published in Audio Amateur Magazine in the 4th quarter of 1989. |
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| still4given |
OK, can any of these regulators work to bring 125V rails down to 90V?
Blessings, Terry |
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| Mikett |
| I'm not an EE but if in the simplest fashion, if you float the grounds of each rail with a zener, you can lift the volatge up on each side. If higher currents are seen, then a "power zener" with a pass transistor can be implemented. Of course this can be refined by using better voltage references but the lifting concept is valid. |
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| Stuart Easson |
To answer your question, in essence yes, most of these can be built out to drop 125v to 90v. The pass transistor, be it BJT or mosfet only has to deal with the potential difference from the highest possible voltage in to the lowest defined output, in this case 35volts. Personally I'd use pass transistors that can deal with the full load voltage of the supply, but it isn't strictly necessary.
But, and as usual it's a big but, if you expect, say 5 amps of output from this bad boy you are immediately sent into the big transistor and heatsink department of the local supermarket. 35v at 5amps is 175watts...of course on average it will probably only be half this, but then again you have 2 regulated rails.
The only one of these schematics explicitly designed to be used in the context of a high current, big output class AB amp of the leach type is the Ryan regulator. It was created to sit in the case of the Adcom 555, mark I. He successfully used the original heatsinks, because the nature of the pass transistors power dissipation is to be the inverse of the output transistors.The total amount of power dissipated is increased, but not by much, and of course the overall dissipation of the output stage proper is lowered.
Ryan chose to use some very good output transistors from sanken, fast enough to keep up, and robust enough to deliver the current the amp could deliver. Arguably the sanken transistors are better than the ones used in the output stage of the 555. I've made a couple of single output versions of these and put them in the Adcom 545ii, with very noticeable improvements, so I know it works. I have the ryan article somewhere, if I can find it I'll scan it and put it somewhere for you guys to look at. IIRC it lowered PSU ripple and droop from a few volts to a couple of tens of millivolts, not bad for a 20amp regulator.
It's kind of like you are cascoding the entire amplifier...and as such the regulator has to have the same attention to detail and at least in current has to match the overall capabilities and expectations of the amp itself. No good making a 5 amp regulator for an amp that can drop 15amps into a reactive load...
Hope that helps
Stuart |
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| Stuart Easson |
...Ryan used some transistors that are no longer available, but the recommended replacements from Sanken - 2sa1216/2sc2922 are very nice.
Stuart |
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| jleaman |
| Id like to try one of these setups and build one. what is the rail voltage after regulation ? |
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| djk |
http://www.audioxpress.com/bksprods/pcbs/nelsonpass.htm
ITEM # PCBP-10B Pass/Thagard A75 Power Amplifier
From Audio Amateur Issues 4/92 and 1/93. Pass/Thagard A75 2-channel power amplifier power supply board. 3-3/8 " x 5". 1 lb. $8.95
The Ryan regulator has some problems as published. Holton has a fix published.
http://home.kimo.com.tw/skychutw/
Then click through to 'ampzilla', 'son of ampzilla'
Hafler does the same on the XL280, XL600 |
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| Villaw |
Does this provide any regulation DJK? |
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| djk |
"Does this provide any regulation DJK?"
Yes, it uses MPSA42/92 and MJE13031/30 pairs
http://www.passdiy.com/pdf/a75p2.pdf
If more than 150V total is needed then use the MJE15032/33.
Board has other goodies (all optional) on it too, inrush limiter, fan speed regulator, etc. |
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| Stuart Easson |
The regulator you mention is not for the outputs, it doesn't have anywhere near the capacity for that, but it would be perfect for everything else...
Stuart |
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| still4given |
Hi guys,
Please excuse my ignorance, but the Superamp is designed to run on 90V rails. So far, almost all of the regulated supplies that folks have listed are not rated for anywhere near those voltages. Since this thread was birthed out of the Leach Superamp thread, shouldn't we be striving to come up with a regulated supply that will serve that amps needs?
If you have a design that can be modified to supply those voltages, would it be too much trouble to show how it should be modified to meet that purpose?
Thanks, Terry |
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| Villaw |
it appears we are all stack here. It appears difficult to create an all out regulated PSU at such voltages with the added bonus that you would need this to output 5 A or so as well.
The more knowledgeable members should shed some light in this path, to us mere mortals. |
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| jacco vermeulen |
Hi Terry,
it looks as if two conversations are talking place on this thread.
One is about an active voltage regulator for the front end of the Super Leach.
The second for obtaining regulated powerlines for the output stage.
The first one is not difficult.
It needs few components, a regular Joe like a BD139 or BD140 is fast and big enough to deliver the current required.
Active regulators need very fast, wide band, devices for adequate regulation.
Devices like the 139/140 go way over 100 mHZ bandwidth, a couple of 100 mA they deliver easily with a decent heatsink, say 10 C/W.
An active regulation for the output stage needs big heatsinks, high power transistors, multiple ones.
And they need speed too, and that costs !
The posted regulator from walkabout Anthony Holton delivers plenty amps for such an output stage.
Problem is that i am one of the few that have the 2SC2565 and 2SA1095, Toshiba stopped production.
Replacements like a 2SA1303/2SC3284 can be used, they are not as fast as the ones in the circuit, bandwidth is much lower , at 50 MHz.
A single one probably costs as much as several IRFP240's in the US, the Leach requires a substantial number of them.
Heatsinks will be big, cost a lot of money, and you'll need a big chassis for them.
With class A output stages, an active regulator for the output stage makes a lot of sense.
The regulator can drop noise level due to the high bias enormously, and as mentioned you're talking a constant current source with class A amps.
Regulation for class AB output stages is questionable, i think.
The current at constant voltage changes from 100 mA to way over 10 amps if needed.
I have built a couple of class A amplifiers with full regulation.
With a fully regulated output stage the obvious, in my reasoning, would be to transfer the Super Leach to a high class A or full class A amplifier.
Given the power level, i'll settle for class AB.
That is why i am building the Leach, Pass doesnt do AB's.
For the front end i mentioned one earlier that can be changed for 90 volts operation. If needed i can deliver ten circuits that do the job.
Who knows, maybe Master of the Universe Self made a couple.
For the output stage i can get you one too that does 90 volts in, 75 to 85 volts out, delivering 10 to 20 amps.
But tiny question, do you want it ?
There may be an alternative.
Norman Thagard designed and built an amplifier in the 90s, with advice from Nelson Pass.
The output stage used a combination of MJ150** BJT's and Mosfets. Mr astronaut called it Bi-Mos.
It is not the same as full active regulation, somewhere in between.
The output stage looks like the Double Barrel, both devices are stacked.
But the Base and Gate of the BJT and Mosfet are not connected, one handled the current, the other the voltage. |
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| djk |
"If you have a design that can be modified to supply those voltages, would it be too much trouble to show how it should be modified to meet that purpose?"
If you can't do it from the instructions provided, maybe...
This is DIYaudio.com last time I checked.
Go to the Leach site and figure out the bias currents from the instructions provided (5th grade math required).
Plug that number into the (5th grade math required) instructions at the PassA75 site. |
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| andy_c |
Regarding the use of regulators with power amps, the choice of running only low-power circuitry from the regulator and high-power circuitry from an unregulated supply is not nearly as big of a compromise as it might seem at first.
If you conceptually split the power amp into input stage / VAS combo in one half, and output stage on the other half (including all 3 stages of emitter followers in the Leach amp case), analysis of the circuit shows that the input stage / VAS combo dominates the power supply rejection performance. The power supply rejection of emitter followers is actually quite good compared to a typical input stage / VAS combo. This is a good thing, because it says if you run the input stage / VAS combo on a regulated supply and the output stage from the unregulated supply, you have the possibility of dramatically improving the overall PSRR of the amp (if the regulator line regulation is mathematically considered part of the amp itself). The current demands of a regulator designed to do this become quite reasonable, and there are no efficiency issues like you'd see if you tried to run the output stage from a "monster regulator". This means "garden variety" regulators can be used, with the necessary mods for high-voltrage use.
Below are links to a couple of alternatives for adapting the LM317/337 to high-voltage use. In the Linear Tech app not below, the relevant circuit is in Figure 11 and described in the text nearby.
http://www.linear.com/pc/downloadDo...,C3,P1243,D4099
The National app note below describes a similar circuit:
http://www.national.com/an/LB/LB-47.pdf
Hope this helps,
Andy |
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| jacco vermeulen |
Hey, that's an idea, lets use vacuum tube regulation.
Figure 7 looks like a nice lab supply. |
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| darkfenriz |
the simpliest idea is for me like this
(sorry for using MSpaintSpice) |
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| LBHajdu |
The truth is active regulation of the whole power amp (front and back-end) is just as complicated as driving one amp with another. Because I am having my transformers custom wound (it cost the same as off the shelf) I’m going to have them wind the two secondarys wit taps at 0-40-50Vac. This will give me two rails, one at +-57Vdc and one at +-70Vdc. The 70volt rails can be regulated down to 57v. If the active regulation doesn’t make things sound better I just chuck the boards and go with no regulation by using the 57v tap from the transformer.
The Anthony Holton regulator witch is an improvement on the Ryan Power Voltage Regulator seems best to me. I would like to get more power out of it. I have taken the hard to read picture and redrawn it with some changes.
Changes:
Replaced all 2SC2240 with MPSA42
Replaced all 2SA970 with MPSA92
Replaced all power devices with MJL21194 and MJL21193
Doubled the number of output devices
Renumber all resistors
I have never seen a schematic where a mje340 drives 4 pairs of output devices, so I assume that you need an MJE15032 as a buffer (If I’m wrong about that please let me know). This is where I need help from some one that really knows what they are doing. How exactly does one slip in the MJE15032 and what values have to be changed? Are there any engineers out there?
Attached is my schematic: |
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| LBHajdu |
You will want to expand the last picture I posted all the way otherwise it becomes really difficult to read.
I am also posting a picture of the “known to work” schematic for the Anthony Holton regulator. This one is a little hard to read even when it is expanded all the way. But magnifying it helps. |
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| Villaw |
I wonder how different sound an amp would have if one were to substitute the full regulator circuits suggested with a very large bank of good quality capacitors powered by an oversized discrete transformer. In effect this would serve as a cheaper type of "regulation" as flactuations in voltage would subside if the transformer were able to handle the current drawn being say at a maximum of 20-30% of its power rating.
As Jacco suggested, a small separate PSU for the driver stage would assist against any voltage drop dissipated by the front stages. Moreover the front stage could easilybe regulated with a very simple low current circuit for superior results.
The net effect would be to have full regulation for the driver stage and excellent "pseudo-regulation" of the unregulated PSU for the output stage without needing to power the amplifier by another regulation "amplifier" with the added disadvantages of heatsinking, cost and labor. |
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| jacco vermeulen |
If you look at the top US amplifiers in the +250 watt range from the last 20-25 years heavy armor powersupplies were common.
I doubt that Mr Marshall designed his amplifier in the 80s to drive an Apogee or an Infinity IRS.
US amplifiers traded with BIG Holden&Fisher toroids and very large Sprague and Mallory capacitors.
In Europe amp builders went for relatively small transformers and large numbers of small caps.
In Japan the philosophy was to build amplifiers the size of the japanese, small.
No room for big powersupplies,but electronic gadgets.
In my view, a large part of the dominance of US amplifiers was due to stable power, big powersupplies.
An amplifier like the ML23 is in the Super Leach range.
The toroid transformers used in the 23 are 1200VA types.
I believe the capacitors used for the output were double 46.000 uF per channel, connected to the output devices with solid metal bars, an inch wide.
The gain stages had 15.000uF caps, separate windings, and voltage was stabilised for the front end.
The SuperLeach is capable of delivering 300 watts RMS.
With an output stage of minimal 12 devices it has a peak capability of over 2500 watts.
I'd think the amplifier should be capable to deliver next to 900 in 2 ohm, close to 1500 peak.
But that requires a big transformer and big caps, the original powersupply will not hack it.
I quote KiloWattski: Why re-invent the wheel, copycat the artist !
With a bigger powersupply lower ripple comes as a bonus, no need for fancy PSRR mods.
And more stable voltage at lower gains improves sound quality.
The genuine freak skips active regulation anyway, he decorates his livingroom wall with car batteries. |
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| LBHajdu |
Doesn’t anybody know how to, calculate the values for my circuit?
Villaw,
I believe this quoted post will put an end to your speculation, assuming the results can be believed:
| quote: |
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.
|
But as I say I’m not taking any chances with the dual taps. |
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| acenovelty |
LBHajdu,
"Doesn’t anybody know how to, calculate the values for my circuit? "
It appears not, and what happened to:
"For the front end i mentioned one earlier that can be changed for 90 volts operation. If needed i can deliver ten circuits that do the job. Who knows, maybe Master of the Universe Self made a couple.
For the output stage i can get you one too that does 90 volts in, 75 to 85 volts out, delivering 10 to 20 amps.But tiny question, do you want it ?"
posted earlier.
Even djk says "If you have a design that can be modified to supply those voltages, would it be too much trouble to show how it should be modified to meet that purpose?"
If you can't do it from the instructions provided, maybe...
This is DIYaudio.com last time I checked.
Everyone is eagerly waiting. Seems we must suffer through a history lesson first. |
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| Mikett |
Regarding the "tapped" transformer. I heard of someone using that configuration but adding a "party switch". If the amp was used for party purposes, the regulator was removed/jumpered out and the lower voltage unregulated was used. That way, one need not worry about power dissipation of the regulators in "non critical" listening high continuous power situations.
I've been browsing Linear Tech newer three terminal regs and they appear to be much improved over the older 3 term regulators. Maybe the BOAK regulator needs revisiting by someone more qualified than myself. Keep in mind the boak regulator uses preregulation so that under heavy loads all the pass transistors might see is 5-10 volts. |
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| Villaw |
| quote: | Originally posted by LBHajdu
Villaw,
I believe this quoted post will put an end to your speculation, assuming the results can be believed:
[/B] |
Well not really because I have read that too and I fully take for granted the writer's tests and comments. My point is strictly limited to the economics and efficiency side of it.
Clarifying, my point is to oversise so much the transformer and have so much rail total capacity as to have an almost constant voltage source. The argument being that it would be easier and less costly to pack up say 100000uf per rail and use a 2kva transformer than use the circuits suggested. This is just a layman's opinion on the subject based on empirical evidence.
Furthermore if one were to choose the smaller leach amp with full regulation then that is another story since for smaller currents regulation is not that much of a hassle.
I am also a keen propounder of the theory of avoiding the reinvention of the wheel as it is very inefficient especially in this area where the larger companies have spent so much R & D on the subject. Even if we argue for the next 20 years to come our finding would still lag behind the research made by the Mark Levinsons and krells of this world. Therefore why not find out what a really successful, in terms of tests etc, amp of similar size uses and copy that. If the case is that of full regulation then I guess there is no point in arguing about it. A place to start is to examine a recent model such as a Krell FBP-600 or other amp not wishing of course to favor Krell over other brands. |
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| jacco vermeulen |
| quote: | Originally posted by LBHajdu
I have never seen a schematic where a mje340 drives 4 pairs of output devices, so I assume that you need an MJE15032 as a buffer |
Did you calculate the gain you need for driving the 21194/21193 ?
The MJL21194/21193 need between 2 and 2.5 volts to open up,
(average is like 2.2 volts i think)
Normal driver current is in the 20 to 50 mA range.
Suppose you choose 25 mA.
Then the emitter value for the ML15032 is :
2.5 V / 25 mA = 100 Ohm.
Once the output devices are open voltage increases on the output, voltage over R23 (?) remains 2.5 volts to keep them open.
Dissipation for R23 is : 2.5*2.5 / 100 = 0.06 watt.
The value for R23 depends on the voltage needed to get the outputs to open, and isnt really dependant on powersupply voltage, as you can see.
With audio amplifier driver stages the current going through the driver influences sound quality, designers try different values to hear ( and measure) what current level is optimal.
Oops, yet another history lesson !
You can do the same for the MJE340(if you think you need it) |
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| LBHajdu |
jacco vermeulen,
So you agree with me that a buffer is needed in-between the outputs and the MJE340 ?
I’ll plug this into my Multisim2000 software and see if it seems right. I don’t know of I can trust this software, as it is the first time I have used it and I can’t find exactly the transistors I want to use.
If anyone is interested, here is the model as it is now:
Thanks,
Leve |
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| Mikett |
In DIY you do some projects then you begin to "push the envelope". DIY is not of necessity for economics sometimes as most commercial products are. There are categories of projects and a regulated supply for an amp is not a "bang for buck" or optimum cost one by any means.
I think the author steered into the "good enough for reasonable cost" camp very quickly and did not discuss what made the Mark Levinson tick
BTW my initials are ML, my amps are ML ( Marshall Leach) and I like ML ( Mark Levinson) equipment but can't justify it. So that tells you of my biases. |
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| jacco vermeulen |
LBHadju,
The emitter resistors on the output stage can handle nearly 4 amps each before you fry them.
4 in parallel is 15.5 amps, say 16.
The MJL21194 has an Hfe of 25 at 8 amps.
16 amp divided 25 is 640 mA.
The MJE15032 fully open has to push 640 mA in the output devices.
The MJE15032 has a minimum Hfe of 50 on its datasheet.
(not entirely true, for the exact number you need to see the graph)
Means the predriver MJE340 has to deliver 640 / 50 ~ 13 mA.
Then, the MJE340 has an minimum Hfe of 30(sheet, not graph)
So, the MPSA92 has to push 13 / 30 ~ 0.5 mA in the base of the MJE340.
But if you take a look at the sheet for the MPSA92 you'll see that it has an Hfe of minimum 25.
Fully open with only 0.5 mA flowing out of the emitter of the MPSA92 the current coming out of the base is :
0.50 / 25 = 0.02 mA !!!!!!!!
The first MPSA42 connected to R13 has 12 volts on its base, R13 has 11.4 volts behind the emitter of the MPSA42.
Current through R13 is 11.3 / 4.7 k = 2.4 mA.
If there is a current of 0.6 mA flowing through R17 there is a voltagedrop of 0.60 volts on the base of the MPSA92 next to R17.
The difference : 2.4 - 0.60 = 1.80 mA can flow out of the base of the MPSA92.
Before that happens voltage level at the output is high enough to open the second MPSA42, so more current from that will flow into R3 and less from the first MPSA42.
Less current means less through R17, means less voltage drop over R17, less current from the base of the MPSA92.
But anything above 0.02 mA going through it will make the 0.33 ohm resistors go pop !!
Leave the MJE340 out and the required current flowing out of the base of MPSA92 is 30 times 0.02 = 0.6 mA.
An MPSA42 is not the same as a 2SC2240, Hfe for the 2SC2240 is not 30 but 200 minimum, same for the 2SA970
In the original circuit total Hfe from the 2SA970 and the MJE340 is
200 * 30 = 6000.
In yours it is : 25 * 30 * 50 = 37500.
How many amps do you want the output to deliver ?
btw: i would not object to owning a couple of ML2's
Anyone wanting fully regulated ML2's, ask for a thread and design boards. I'll join !!
All original drawings for the ML2 are at www.MarkLev.com |
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| acenovelty |
"If needed i can deliver ten circuits that do the job. Who knows, maybe Master of the Universe Self made a couple. For the output stage i can get you one too that does 90 volts in, 75 to 85 volts out, delivering 10 to 20 amps.But tiny question, do you want it ?"
Circuits? Guess not. |
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| Villaw |
| quote: | Originally posted by Mikett
In DIY you do some projects then you begin to "push the envelope". DIY is not of necessity for economics sometimes as most commercial products are. There are categories of projects and a regulated supply for an amp is not a "bang for buck" or optimum cost one by any means.
I think the author steered into the "good enough for reasonable cost" camp very quickly and did not discuss what made the Mark Levinson tick
BTW my initials are ML, my amps are ML ( Marshall Leach) and I like ML ( Mark Levinson) equipment but can't justify it. So that tells you of my biases. |
I believe the author gives a very good account of his empirically based knowledge there but strictly from a subjective perspective. Having noted that however, I take for granted your experiences too to the effect that I shall try your suggestions using Jen's smaller version perhaps at a lower voltage supply and am sure would have tremendous difference.:cool:
All in all, what is difficult, and what seems to be the view advocated by Jacco and some of the rest of the members including the TNT author, is that for very high power amps such as the super leach it would be virtually impossible to build a regulated supply to accomodate say 600w at 4 ohms or 900w at 2 ohms without perhaps using 12 power transistors for the PSU alone.
:bawling: |
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| mikeks |
| A well designed amp, with intrinsically high PSRR should not require electronically regulated supplies of any complexion to give of its best.... |
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| Mikett |
Re: the ML2s, if my experience is anything to go by there are a few points that I have noted.
Using similar parts quality, similar fully regulated power supplies, I have found that I prefer the sound of the standard Leach over that of the Super Leach. Thus a reason why my Super Leach is at rest most of the time now.
Yes, a fast modern power supply does yield better sound quality. I have compared the sound of a prereg Sulzer type to that of the prereg type Jung/Didden type of supply and the differences are immediately obvious. There is simply no comparison. BTW, these PSUs were used with the AD744-811 line preamp. These ICs already sport pretty good PSRR furthermore, the unregulated feed was coming from a 160VA toroid, yet there were differences so PSRR does not tell the whole story.
What if you strapped on a Jung Didden PSU onto the front end of a ML2 and used the standard regulator for the outputs in CLASS A, maybe this amp would be really something. I see the ML2 only uses rails at 24V. Hmmmmmm......
Again for those wanting to build a "statement" amp, I'm not sure the Super Leach is the way to go. I'd tend towards a standard Leach but really put no holds on it. I was twenty years younger, better ears but foolish enough to think I needed a monster amp. Like getting high horsepower autos today.
As for the number of pass transistors and dissipation,it's really not that bad. First you use a large tranformer that does not sag much. That way the delta between the full load and off load voltage is low. Next, my voltage drops were handled in three sections. Preregulation, current sensing, final pass transistor. I calculated that on peaks I wanted 50 amps. At these loads, my prereg pass transistor only saw 5 to 6 volts, and similarly with my final pass. I did not desire a 50amp steady because I never could see a need. The BOAK regulator used a three terminal device in a current split arrangement with the pass transistor. The three terminal device is bolted onto the heatsink and this thermal capacitance allows large current transients to go thru before it shuts down because of heat.
So for music and normal listening, the regulator is fine, not hot at all but on steady current, you have a heat disspation issue and it shuts down as a three terminal device would.
The weakness of this regulator is the speed. There is no doubt about that. However, it is much better than no regulator at all. I'm an engineer and yes, the models say otherwise but I trust my ears and I've been enjoying fully regulated power amps for the last twenty years. I am grateful to TAA publications and DIY fanatics who push the envelope and lead the way. People like J. Didden, Walt Jung, James Boak and of course Marshall Leach and Gary Galo who scouted the territory and reported back. The world is not flat my friends, even though our maps/models tell us so.
Power supply regulation has been a seriously neglected factor because it is commerically impractical except for mega buck equipment and even there, they are copying what amateurs have been doing the past 20+ years.
sorry for long post. |
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| jacco vermeulen |
| quote: | Originally posted by Mikett
I see the ML2 only uses rails at 24V. Hmmmmmm...... |
Did you check the output stage bias of the ML2 ? |
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| Mikett |
| No, I just peeked at the schematics quickly. I imagine it doesn't help with the Kyoto accord. |
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| jacco vermeulen |
It seems that most on this thread hold the view that an active voltage regulation for the front end of the Leach is definitely an improvement, may it be regular, extended , or the Super.
First objective, as i see it, is coming up with the right regulator for the front of the Leach.
Those who feel for a fully regulated powersupply for the output stage have a good idea by now how much hardware is involved to build an active regulation with a high voltage and current capability, and the high demands on the quality of the active parts.
Seems to me that on DIYaudio the JLH would be the first to try active output regulation on, maybe someone on the JLH thread tried it.
I am a DIY person, not a history teacher or an audio designer.
I received my Toshiba output devices for the Leach, hope to get the Leach boards from Jens in about a week's time.
By then i would be pleased if this thread resulted in the proper voltage regulation circuit for half of the Leach, the front half.
Maybe a good idea to ask Janneman Didden to join this thread ? |
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| Villaw |
Ok then, I suggest we use one of the topologies already suggested on this thread and have someone design us the pcb. If a number of us make a group then we can pay a mark up as well to the designer.
I propose to create this for the small leach amp as for the super one it would be impossible to construct. Any views?
Jens, Jan, Jacco anyone interested in the pcb design? |
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| JensRasmussen |
As the result of the Super Leach thread is unknow as of today, I would think that I can find the time to do the layout.
Since I will have most of the components in my libs I will create the schematics and a PCB, but the construction and design of the psu I leave to you.
Hows about that?
May I suggest a SKYPE conference?
\Jens |
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| Villaw |
I would be happy with that arrangement Jens myself. If I ahve a gerber or whatever file that the pcb company can accept I would raise my hat to you...
As regards Skype, I dont have the mic and speakers unfortunately but you have my position on this anyway.
Which regulated PSU design topology will you follow? the more versatile in terms of voltage and current the better. |
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| LBHajdu |
I would love it if you designed a regulator for the stander leach amp. A think it’s +-57V.
We have two options:
1)
A regulator built with passive (I am using “passive” very loosely) parts (transistors, mosfets, op amps. ect.) The Anthony Holton regulator is a good example.
2)
The other option is a Boosted regulator, A small off the shelf regulator has it’s current capacity lifted. A good example of a low voltage regulator of this type can be seen at http://www.alansmodels.com/links/to...powersupply.htm
This type of power supply is the type used in the testimonial from Mikett. This type of regulator is simpler to build (fewer parts). I can’t comment on the proforments.
I think I may have the schematic to the one Mikett is talking about. I don’t know what the copy rights on it are, however I can e-mail it to you if you wish.
I am not particularly concerned if PCBs are not available, I have funny heat sinks anyway so they may not be usable anyway.
What is a SKYPE conference?
Leve |
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| jacco vermeulen |
Number one.
Regulation circuit for the Mark Levinson 23.5 |
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| jacco vermeulen |
Number two, simple regulator from a fast Elektor amp.
This one is for 70 in, 60 out.
For a higher voltage and current rating :
The BD139 could be swapped for an MJE15030.
The BC546 by MPSA29 or MPSA42, up to 100v in preferably the 29 because it has an Ft of 125 MHz.
3 resistor values altered, and a zener diode.
(could not get a good fix with the light, can scan this one and post a pdf) |
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| LBHajdu |
jacco vermeulen,
The ML looks like only a front and amp, and so totally unsuitable in it’s current form. The other is better. All the regulators you posted all share the same topology more or less. The Anthony Holton regulator also shares this topology. However before we consider any of this we should decide if this is the topology we actually want.
In my post #65 I have split regulators in to two different groups. We must first decide which we like best.
Things to consider:
Which has the lowest Output Impedance. That is based on which is fastest.
Which has the highest noise rejection.
Which is lest likely to go into oscillation.
Jens,
Since you have built it, you’ll be able to decide how much regulation you need based on how much the rails sag.
I don’t what to put words in Jens mouth, but I think we’re going to need about 4 output devices pre rail (MJLxxxxx). With a 10v drop over the regulator and the amp at it’s max draw of 8 amps that’s about 80watts dissipation per rail. With 4 devices its 20watts per device. That seems about right. The 80watts is the peek dissipation however. At idle the amp only draws 200mA at best s the dissipation of the regulator will be only 2watts (4watts for both regulators).
Jens I am dieing to know what your thoughts are. Please do tell.
Leve |
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| jacco vermeulen |
Thats funny, the ML pic looks like an active voltage regulator to me.
Even the voltage entries and levels are there, 87 volts in, 65 volts out.
Maybe i am getting old, i even see the regulated and not regulated outputs mentioned on the circuit.
I suppose i am the only one on this thread who desires an active voltage regulator on the front end of the Leach ? |
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| LBHajdu |
But it’s not designed for anywhere near the current we’re talking about. It could only drive the front end. Now that I have looked it up the same is true about the “fast Elektor amp”.
It’s like suggesting that a Childs wheel barrow could transport a 10ton block of steel. Yes it will fit inside, but no it’s not going anywhere. |
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| jacco vermeulen |
| Okidoki, then i am out of here. |
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| Mikett |
Stability
From a stability standpoint, the three terminal device looks to be the easiest and safest. Over the years, every time I hear of a discrete high current regulator, I always hear of instabilites somewhere along the way. That scares the heck out of me with high power amps.
Reliability & Protection
What I can say is that I have built 6 Boak regulators and none of them were unstable. I know of at least 12 more and all have been rock solid with no reliability problems. Furthermore once it actually protected the output section of my amp.
Performance
As for performance, it is NOT the best from a low output impedance standpoint at high frequencies BUT that was in comparison to PSUs driving preamps such as the Sulzer and the Jung/Didden super regulator. I strongly suspect nearly sure that if one of the newer LT three terminal devices were used, it would not be shabby at all especially at low frequencies. Again, taken in perspective, no passive xformer cap arrangement even comes close. Also keep in mind that the LT will pass high current transients and it is this ability that allows the whole arrangement to carry high currents.
Please someone dig out those older TAA in the early 80s. Mine is in storage right now or else I'd offered them up by now. |
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| Mikett |
TAA 1980 Regulated Power Amp Power Supplies
TAA 1983 Measure Power Supply Output Impedance, Pt 1-2
TAA 1981 POOGE-2: Hafler DH-200 Upgrade |
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| jleaman |
| Skype is Voice over ip software for free i bought a head set with a mic and i talk to jen's all the time now, we have it down to a art for when to talk i get up he is getting home from work when i'm coming home from work he is going to work 9 hours difference : O ) Skype is a nice piece of software i recommend it for sure |
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| janneman |
| quote: | Originally posted by Mikett
TAA 1980 Regulated Power Amp Power Supplies
TAA 1983 Measure Power Supply Output Impedance, Pt 1-2
TAA 1981 POOGE-2: Hafler DH-200 Upgrade |
TAA 1995 issue 1,2,3,4, Jung/Didden/Galo, "Super regulators for audio".
Jan Didden |
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| Villaw |
| Jacco, get your *** back here.. we need you! |
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| Mikett |
| Now that janneman is here. Can the super regulators be easily and reliably scaled for the voltages we are talking about. If so, they are going to be added to the front end of my Leaches pronto and I'll leave the heavy current stage on the boaks. |
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| jacco vermeulen |
Boaks ?
Could be you wont feel that glad with me on skype, i talk even more than i type.
Maybe this thread needs a head count:
those who want a good one for the front and those who desire something for the back(side).
An integrated voltage regulator circuit i can just do myself, and better than with LT317/337.
I have a couple of tubes of Military versions, in TO3 case, the LT117AK is the MIL spec version of the LT337.
(ex airplane factory stock) |
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| jacco vermeulen |
The D44H11 is nice, it has an Ft of 50 MHz, and delivers loads of amps.
But only goes till 90 volts, OK for the regular Leach. |
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| acenovelty |
Power Supply Components
The power supply circuit diagram is the same as for the Low TIM Amplifier. The parts are the same with the following exceptions.
* T1 - The transformer should have either a center tapped secondary or two separate secondary windings which can be wired in series. With 120 V ac rms applied to the primary, the no load secondary voltage should be 120 to 130 V ac rms for a center tapped secondary or 60+60 (60x2) to 65+65 (65x2) V ac rms for two secondary windings. This should give a no load amplifier power supply voltage of plus and minus 85 to 93 V dc. Some transformers are rated at 115 V ac rms on the primary. With 120 V ac rms applied, the secondary voltage will be greater by a factor 120/115. If the transformer is rated at full load, its no load voltage will be 15% to 20% higher. I would recommend a transformer current rating of at least 6 A. |
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| Peter Daniel |
| quote: | Originally posted by jacco vermeulen
Number one.
Regulation circuit for the Mark Levinson 23.5 |
I've buit that regulator and was using them in A-75 front end. Still have the pictured boards, if someone is interested, they are for sale. |
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| jleaman |
| YOu selling them boards ( regulator ) peter or are they in something ? |
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| Peter Daniel |
I'm selling complete boards, $50 a board.
They can be adjusted for wide range of voltages, the ones in picture are set to 50V DC. |
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| jacco vermeulen |
Peter, you are an audio designer.
What is your opinion on the ML active regulation ?
In the A75, that means not the original voltage doubler circuit of the A75 ? |
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| jleaman |
| quote: | Originally posted by Peter Daniel
I'm selling complete boards, $50 a board.
They can be adjusted for wide range of voltages, the ones in picture are set to 50V DC. |
Please email me so we can talk : O ) about this board. |
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| Peter Daniel |
| quote: | Originally posted by jacco vermeulen
Peter, you are an audio designer.
What is your opinion on the ML active regulation ?
In the A75, that means not the original voltage doubler circuit of the A75 ? |
I didn't realy compare this reg to any other, so it's hard for me to comment. However, A-75 sounded really good, may be in part due to those boards? ;)
I was never using a voltage doubler, and I've built 3 sets of those amps. |
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| jacco vermeulen |
True, the boards look great
(as did the other from you i have seen till now)
The end of the board resembles the GC again :clown: |
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| LBHajdu |
The thread has cooled down a bit. Mikett has photocopied and sent me the Boak Regulator (with Walt Jung’s modifications) documentation. It seems like a nice regulator, especially considering the date when it was designed (much like the leach amp). I was surprised that it’s a two stage design(two regulators the output of one is the input of the other).
I believe that the rules of DIY audio don’t allow me to post it even if I could. I am in the process of redrawing it in pdf format (maybe I can post that).
The semiconductors seem to be still available. However they are somewhat old I was hoping someone could recommend some modern day improved parts. What would be really great is if I could get way with using some of the same parts Jens leach amp uses, as this cuts down my parts list.
The parts I am looking to replace are:
1N5401
MJE2955
MJE3055
TIP35C
TIP36C
TIP31C
TIP32C
LM340T5
LM320T5
Leve |
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| Mikett |
I don't recall sending you photocopies of the reg but if you have them, great.
There are really three key modules there, a Preregulator/capacitance multiplier, the three terminal current split with the 2955 and the lifting of the ground reference for the three terminal device. I have always used ( MJ802/4502) for the pass transistors and had good results. The MJ 15003 did not seem to have as high a peak current capability as the 802/4502. The voltage on the pass elements are not that high.
Again, I'm sure that there are improved three terminal regs such as the LT series from Linear. Also there might be better outputs than the MJ802/4502 I used 20 years ago. Make sure you use the modified regulator as per Walt Jung suggestions.
You can tell that this reg is optimized for the low and midrange performance. The HF area is left to output caps to flatten.
Still, has anybody built a high voltage low current reg for a power amp front end with the bandwidth of Walt Jung/ Jan Didden super regulator?
The improvement in a "line stage" is obvious with that PS, imagine it's effect on something with 20-26 dB of gain! |
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| LBHajdu |
I’m sorry I got you confused with somebody else. If the Jung type opamp based regulators are better then these boosted designs, there are “power op-amps” that could be used to make such a regulator. OPA541 can run off of rails of +-40V and can output 5A. This would be more then sufficient to drive the base of a power transistor in a Jung type topology. Does anyone have any thoughts on this?
Leve |
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| jacco vermeulen |
What bandwidth would you like a voltage regulator to have ?
An opa541 is a complete audio amplifier, with a regulated low bandwidth.
I have LT117/LT317 voltage regulators that are 0.005 % line regulation accurate, still do -20dB at 500 KHz. |
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| LBHajdu |
This is where I stand. I am going to try a regulator, it’s just a question of which one. The Boak Regulator is currently looking like the best one. It’s performance is not outstanding but it’s pretty good and it has been tested in many amps and is known to work well and it’s one of only two or three that will work at these currents and voltages.
However I know if someone wanted to they could design a better regulator then the Boak Regulator. In 20 years there have emerged better parts that are faster and capable of withstanding more voltage. The Jung regulator seems simple I have looked at it, however I don’t think I have the skill to upgrade it to the current and voltage where talking about.
If some new ideas come along that makes it possible to reliably build a better regulator I’ll obviously go down that path instead of the Boak. However, at the current time there are no better regulators so it looks as if the Broak is still my best bet. |
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| jez |
just a quick word of caution here... I have tried many types of regulator over the years, both published designs and high voltage /high current designs of my own, and whilst I am aware that the levinson amps and also the Naim amps use full regulation with success, the majority of attempts to fully regulate will result in worse sound than with a large unregulated supply (usually sounds more "grey", "leaden", "solid-state" and undynamic than unregulated version), regulation of input/driver stages is usually more successfull but any improvement is dependent on the PSRR of these stages.
I have a feeling that there will be replies to this saying that this is not your experiance of regulated amps and that they DO sound great but this is not what I have found..... dont say I did'nt warn you:smash:
This is one topic in which I find myself in complete agreement with a certain D.Self:xeye: |
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| Dark Harroth |
| quote: | Originally posted by Peter Daniel
I've buit that regulator and was using them in A-75 front end. Still have the pictured boards, if someone is interested, they are for sale. |
Pretty good regulator, I should say... :up:
Is it somehow possible to get your board layout/schematic (if it's not also for sale)? My amp just happens to require 50 Volts :rolleyes: |
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| Dark Harroth |
Well, the information there might be pretty useful, but it's written in hieroglyphs. And furthermore, there are some parts not available in any shop nearby. So, I've decided to buy the SPS for my headamp from a local enthusiast.
But I have an another question: is the Jung Super Regulator (the latest version) capable of driving a 50V-load @ 4-5 Amperes? The thing is that the regulator from my 2*150W amplifier had burnt a few days ago, but the amp itself and the transformer are still alive. I tried to find a replacement for the zeners and the power transisors, but they are obsolete and very hard-to-find (GDR-made).
Also I tried to use passive filters (two large 0.01 F capacitors), but it doesn't seem to sound very good.
Any help would be appreciated. |
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| Mikett |
The Jung Super Reg is not capable of that kind of current, think about less than one tenth that.
Using the second link I provided it appears that circuit provides a general idea of how to scale up the Jung Super Reg for high voltages.
Anyone have any further comments on how to get the Jung Super Reg for high voltages? |
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| jez |
To get higher voltage it should be just a matter of adding a x2 gain level translator stage between the output of the op-amp and the series pass device. The op-amp continues to run from the same voltage as now but the level translator and pass device run from the higher rail voltage. The new stage would have to be fast and should be run at an appreciable current, also it would be phase inverting and so the = & - connections to the op-amp would need to be reversed.
Another method is to replace the op-amp IC with a discrete op-amp built to take the voltage. In both cases the compensation would need some playing with. |
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| andy_c |
| quote: | Originally posted by Mikett
Anyone have any further comments on how to get the Jung Super Reg for high voltages? |
I was playing around with this a while back but haven't built it. |
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