I am not the expert actually;
I was the one who proposed it here on the forum for DIY community.
Well Paul Merlin Belencowe book Designing Power Supplies for Tube amplifiers has a very goog section on Gyrators . Using a mosfet as device to imitate a choke not that many parts about 4 resistor a zener and a cap. and try Just one thing about music - when it hits you feel no pain go to miscellanea: look at the ted reg and super ted reg . given it about naim gear you get the idea . I been simulating the gyrator with models of real parts but have not raised the bar up to where a anode choke need to be thats at 150 h plus .
Triodethom;
what is called there Teddy Reg is not a gyrator. It is a ripple filter made of R-C network and a source follower. Source follower allows higher resistances than would be needed without it, that means lower capacitance is needed for the same time constant. It is nice approach, but it is different: it provides low dynamic output resistance of power supply, and very low ripples.
The question was about gyrator loads of tubes, not about power filters. The essence of gyrator load is a constant current source with servo that keeps stable DC voltage on anode providing high dynamic load resistance.
Paul could use Search function of the forum to find a lot about gyrators here in threads we already discussed.
Nobody wrote a book yet about gyrator anode loads. Probably it was me who supposed to write such a book, but I don't have time even for an article in a magazine, despite I promised to Jan Didden several years ago...
Sincerely,
Anatoliy
what is called there Teddy Reg is not a gyrator. It is a ripple filter made of R-C network and a source follower. Source follower allows higher resistances than would be needed without it, that means lower capacitance is needed for the same time constant. It is nice approach, but it is different: it provides low dynamic output resistance of power supply, and very low ripples.
The question was about gyrator loads of tubes, not about power filters. The essence of gyrator load is a constant current source with servo that keeps stable DC voltage on anode providing high dynamic load resistance.
Paul could use Search function of the forum to find a lot about gyrators here in threads we already discussed.
Nobody wrote a book yet about gyrator anode loads. Probably it was me who supposed to write such a book, but I don't have time even for an article in a magazine, despite I promised to Jan Didden several years ago...
Sincerely,
Anatoliy
Last edited:
Thanks all for your responses. I have found searching to be a bit frustrating, wading through oceans of verbiage.
Anatoliy, with regard to your description (post no 7) I have built and used active anode loads - usually single transistors but sometimes cascodes; it's the rest of it I have to understand!
Thanks
Paul
Anatoliy, with regard to your description (post no 7) I have built and used active anode loads - usually single transistors but sometimes cascodes; it's the rest of it I have to understand!
Thanks
Paul
Would a constant current source get close to high impedance low voltage drop desired here or is the rising impedance of a choke to frequency the goal . What I had being looking at a gyrator and a cap multiplier are very close part count and only slightly different connection , but you point is correct Wavebourn . If I understand you the gyrator gives both high impedance and stable dc voltage . This active device then should have great effect on the sound of the tube would it not ?
Last edited:
Thanks for that though of course being for a power supply, the device is run as a source follower with consequent low output resistance.
I was envisaging using the device as an active load which ideally will have a very high output resistance as seen by the anode of the valve. That isn't to say mind you that I might not use the circuit as shown elsewhere!
Thanks again
Paul
One more thread: pay attention on Michael Koster's version also that uses N-type MOSFET. Advantage of his version is, anode voltage referenced to ground instead of B+ in mine.
http://www.diyaudio.com/forums/tubes-valves/143687-gyrator-question.html
http://www.diyaudio.com/forums/tubes-valves/143687-gyrator-question.html
+1
I have a great deal to read still, I'm a dummy with transistors and though I have built active loads, regulators and current sinks am not really clear about what is happening...
Incidentally with regard to the LTP thread, in 2002 I built a driver stage using 7N7 with active loads (one transistor) and current sink; driving E810F pentode cathode followers. This worked very well, at +40dB output 9.5v rms) THD was 0.063%.
Paul
Last edited:
I use Gyrators in Mu-follower mode and stage output impedance is very low. A great circuit for a driver (e.g. Currently using this setup on a 6j5 driver stage in my 45SE amp and distortion is the lowest achieved using any other driver) and also using it for pre-amps with great sonic results.
Have tried it with most of DHTs and doing a side by side comparison against an OT (LL1660) 26 preamp, on a blind test my wife (who has a particularly refined ear) preferred it to the OT version...
So bottom line, gyrators can sound really good if used properly!
Have tried it with most of DHTs and doing a side by side comparison against an OT (LL1660) 26 preamp, on a blind test my wife (who has a particularly refined ear) preferred it to the OT version...
So bottom line, gyrators can sound really good if used properly!
Paul,
If you look at the threads I started on 4p1L preamp, help with gyrator and other for example there is a lot of good information about MOSFET and Anatoly's Bipolar-MOSFET version for lower quiescent currents (I.e. lower than 10mA).
A good thing to do is to simulate in Spice to check things first and actually helps a lot to understand circuit, etc.
Cheers,
Ale
Yes, and in order to use it properly you have to understand its pros/cons against chokes:
1. Choke accumulates energy, gyrator turns it into heat so choke uses power better.
2. Choke can saturate and distorts more all the way, gyrator distorts less until hits the bottom then distorts harshly.
3. Choke has parasitic capacitance, gyrator also has capacitance that limits it's upper frequency, even though it can be much higher.
4. Choke picks up magnetic hum, gyrator almost does not. But it is more noisy than a choke because uses active components.
1. Choke accumulates energy, gyrator turns it into heat so choke uses power better.
2. Choke can saturate and distorts more all the way, gyrator distorts less until hits the bottom then distorts harshly.
3. Choke has parasitic capacitance, gyrator also has capacitance that limits it's upper frequency, even though it can be much higher.
4. Choke picks up magnetic hum, gyrator almost does not. But it is more noisy than a choke because uses active components.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.