Pavel Macura's MOSFET Power Follower

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#22
Hi Jay!
Thanks for your reply and advise!. I had thought about replacing LM7xxx by LM317 and LM337, but it happens that the LM337 will suffer a significant deterioration in its impedance and PSRR from the 2 or 3 KHz and more. (the PSRR can be as low as 30dB).
I want to implement the cascode CCS mode (with two units of the LM317, instead of using the LM337).

Can you advise me any other options?

Greetings
 
#23
Hi Diego,

I don't understand electronics as well as you. Your schematic confused me. Are you sure that the regulator capable of supplying class-A amp current? What amp is this? What is the wattage? Are you sure you can get 0V at the output (direct coupled)? If so, I think this is an improvement, provided that the power supply is upgraded. I like chokes for this purpose.
 
#24
Jay said:
Hi Diego,

I don't understand electronics as well as you. Your schematic confused me. Are you sure that the regulator capable of supplying class-A amp current? What amp is this? What is the wattage? Are you sure you can get 0V at the output (direct coupled)? If so, I think this is an improvement, provided that the power supply is upgraded. I like chokes for this purpose.
Click to expand...


Jay:

The circuit is a voltage follower based on mosfet. Voltage gain is slightly less than 1. The circuit has current gain. LM317T regulator serves as a source of constant current of 0.5 Ampere. The circuit operates in pure Class A up to a maximum power of 0.95 watts (on an 8 ohm load). Currently I use it connected to the output of a CD player that delivers 2 V rms maximum, so the maximum output power at 6 ohms is 0.66 watts.
I have intentions of changing the constant current source for improved high frequency response. Would using two LM317 units operating in the cascode mode.

PS: Sorry for my English.
 
#25
diegomj1973 said:
The circuit operates in pure Class A up to a maximum power of 0.95 watts (on an 8 ohm load). Currently I use it connected to the output of a CD player that delivers 2 V rms maximum, so the maximum output power at 6 ohms is 0.66 watts.
I have intentions of changing the constant current source for improved high frequency response. Would using two LM317 units operating in the cascode mode.
Click to expand...

Is this a headphone amp? I think most headphones have higher than 8 ohm impedance? I'm not familiar and do not have experience with headphone amps...

And, are you sure you already have good enough analog amplification after the DAC inside your CD player?
 
#26
Jay:

I use this amp with normal speakers, I do not use it with headphones. My listening room is not very large. Its output power is more than enough for me. Could be used with headphones, but reducing its power output.

You can watch a recording I made on Youtube.

Search for "Common Drain MOSFET Amplifier. Pure Class A (part 1 ) ... to ... ( part 6)"
Grettings
 
#27

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  • Macura,Parwel-Bunta Sziklai follower IRF350+2SA1302+CS TIP142.gif
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  • dinamic_power_follower.jpg
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#29
#30
#31
Hello:

I have two Macura MPF questions, both oriented toward non-hi-fi use, like maybe a guitar amp.

1) I am interested in making a low power Class A amp, ballpark 1W, and having seen the Macura MPF in higher power versions, wonder if there is a reason to not do this (better way).

2) With no specific power output goal at this time, I'm curious if the bag of 47N60 MOSFET's I found is a candidate for a MPF, or better as a power supply pass element? It seems like a rather huge part and if it works 'best' at a particular bias point, then there would be a particular power level that corresponds with that. Trying to use an oversized part at a much lower bias current might be in a less linear region. The very high gfs of some of these big parts is a curiosity, and I suppose it isn't critical in a follower...but it leads me to wonder what difference it makes.

Thank you

Murray
 
#33
Guitar Amp

multi-volti said:
Hello:

I have two Macura MPF questions, both oriented toward non-hi-fi use, like maybe a guitar amp.

1) I am interested in making a low power Class A amp, ballpark 1W, and having seen the Macura MPF in higher power versions, wonder if there is a reason to not do this (better way).

2) With no specific power output goal at this time, I'm curious if the bag of 47N60 MOSFET's I found is a candidate for a MPF, or better as a power supply pass element? It seems like a rather huge part and if it works 'best' at a particular bias point, then there would be a particular power level that corresponds with that. Trying to use an oversized part at a much lower bias current might be in a less linear region. The very high gfs of some of these big parts is a curiosity, and I suppose it isn't critical in a follower...but it leads me to wonder what difference it makes.

Thank you

Murray
Click to expand...

If you want great low power guitar power amplifier, look at my slightly modded ACA (Amp Camp Amp by Nelson Pass).
 

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  • ACA 5W SE MOSFET Guitar.png
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#36
What is the advantage of the Sziklai variation?

Better for clean or the guitar option?

I think I have some of the '1302's, some power Darlington's but the only megamosfets I have right now are some 47N something monsters.

Does the Sziklai pair option make MOSFET choice more flexible?

Thanks
 
#40
lineup said:
I love this sort of amplifier.
Pavel Macura's idea is great.
It is a good replacement for pure Class A amplfiers.

To build a little preamplifier that can feed the circuit is not difficult.
More info at Project 83 - MOSFET Power Follower
Where is also recommended DoZ preamp for use.: Minimalist Discrete Hi-Fi Preamp

Nobody could be disappointed if building this amplifier!
🙂
Click to expand...


Hey Lineup, great to see you back!

Don't forget Ciuffoli's classic (w new PCB):

the Power Folllower


PF2014_sch.gif


( virtual gnd; 'batt supply')

Re, vis a vis

Power follower 99c Vs Zen

Pavel Macura's MOSFET Power Follower



Cheers Lineup
 
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