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Old 25th September 2012, 02:56 PM   #91
Salas is offline Salas  Greece
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Your Vin-Vo should be enough if its J1's pinch off + 2Vbe so R4 can be scaled best for Q1's thermal economy although a mains play allowance can work against tight guesses.
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Old 25th September 2012, 06:02 PM   #92
mikelm is offline mikelm  England
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Perhaps we like a CFB reg for a CFB amp

This one has a better Vref but has slightly less good regulation compared with previous one but should be nice and fast with CFB. No idea how each of these will actually sound.

Salas, please don't feel obliged to check yet another one unless you feel particularly inspired.

I think this is my best effort provided it works as intended ! I wonder if I can squeeze a CCS into a 2.5V space

Sonny any tips or advice for me here ?
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Last edited by mikelm; 25th September 2012 at 06:05 PM.
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Old 25th September 2012, 07:25 PM   #93
mikelm is offline mikelm  England
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In this improved version this regulator appears to give better performance in every respect.

Line regulation about -80db
Load regulation about -100db
Seems to be wider bandwidth and more stable than CFB design.
filtered zener gives good stabilty and should be quiet.

If it were left to me I would go for this one but I don't claim much expertise in this field.

Any further comments welcome
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Old 25th September 2012, 07:39 PM   #94
sonnya is offline sonnya  Denmark
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Current through Q1 drawn from the jfet will destroy Q1 at power up. 8mA x beta (~150).

May be an bc817-25 instead and jfet current of 2 - 4mA. But have to check power disipation In Q1.

Besides This, i Think it is a good implementation.
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Old 26th September 2012, 06:16 AM   #95
mikelm is offline mikelm  England
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Thanks Sonny,

I will investigate the turn on cycle to check this and try the mods you suggest. I will also investigate using a soft start and / or a Mosfet O/P device. Both of these measures should ease the strain on Q1 during turn on and subsequently allow maximum dynamics during normal use.

I will also investigate noise & stability. I'm concerned that I do not loose any of the very good qualities of my choke supplies when I add regulation. Although the choke supplies do not have good load regulation their line regulation is about as good as it gets in the throughout the entire spectrum of frequencies except low bass and I have found this to be a great asset for sound quality.

So using both Salas's Cap multiplier ( as a reference ) and my design I will inject a step signal into the load via varying values of load R and measure the regulator output currents for signs of HF ringing.

For me, particularly with an amp as transparent as your TSSA, this is a crucial issue and I will not tolerate even one cycle of ringing. I think it will be better to have less regulation or just less HF gain rather than any ringing. I will do initial tests with nominal spice caps which may be the most demanding and then after with estimated real world values.

May take a while but I post when I'm done

cheers

mike

Last edited by mikelm; 26th September 2012 at 06:19 AM.
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Old 26th September 2012, 06:21 AM   #96
Salas is offline Salas  Greece
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Looks a bit nicer on some Japanese semis I got in my bin so I gave them a run on spice.
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Old 26th September 2012, 06:58 AM   #97
mikelm is offline mikelm  England
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Our spice methods are slightly different. To test line & load regulation I add a 1V AC source at input and later at output and spice gives me a graphs with -xdb.

I'm not so familiar with LT spice are you adding noise to line & load simultaneously to check regulation or is your method different ?

I think a Jfet with a higher idss & resistor might give a higher impedance but perhaps in this case this is not necessary.
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Old 26th September 2012, 07:31 AM   #98
sonnya is offline sonnya  Denmark
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Quote:
Originally Posted by mikelm View Post
Thanks Sonny,

I will investigate the turn on cycle to check this and try the mods you suggest. I will also investigate using a soft start and / or a Mosfet O/P device. Both of these measures should ease the strain on Q1 during turn on and subsequently allow maximum dynamics during normal use.

I will also investigate noise & stability. I'm concerned that I do not loose any of the very good qualities of my choke supplies when I add regulation. Although the choke supplies do not have good load regulation their line regulation is about as good as it gets in the throughout the entire spectrum of frequencies except low bass and I have found this to be a great asset for sound quality.

So using both Salas's Cap multiplier ( as a reference ) and my design I will inject a step signal into the load via varying values of load R and measure the regulator output currents for signs of HF ringing.

For me, particularly with an amp as transparent as your TSSA, this is a crucial issue and I will not tolerate even one cycle of ringing. I think it will be better to have less regulation or just less HF gain rather than any ringing. I will do initial tests with nominal spice caps which may be the most demanding and then after with estimated real world values.

May take a while but I post when I'm done

cheers

mike
If i was you, i would add a series base resistor bjt transistor. 10 - 22R

This will prevent oscillation on the output device.
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Old 26th September 2012, 11:40 AM   #99
mikelm is offline mikelm  England
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Well this is my latest version.

Adjust R5 for load regulation -100db to -115db
Adjust R3 to vary o/p between zener steps
Change C2 to adjust frequency compensation
R9 smooths out the compensation.
R10 may have to be bigger.
regarding stability it looks pretty good with some compensation applied but the spice results are usual pure fiction in this respect so will have to wait to see in reality.
I think will be OK if used with slow start as shown in Sonny's PSU document.

Will need to build before finalizing exactly what values to choose.

I'm of the opinion at present that chokes up line will still bring sonic benefits particularly regarding purity of the earth rail.

I have other things to do for a few days now so will come back to this later

As always all comments welcome.

mike
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Old 26th September 2012, 12:49 PM   #100
mikelm is offline mikelm  England
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Are we really shure this will sound better that Salas's proposed cap multipier ?

I never made a regulator for a power amp o/p stage before.

I heard that nothing can substitute for the immediate power of charge pre-stored in a capacitor so I'm wondering how much capacitance people are planning to use after the regulator ?
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