Ayre's EquiLock, what is it?

[lumanauw]

From Stereophile's Ayre MX-R review :

EquiLock is kind of like creating a cascode by combining two triodes. You could say we're joining together two transistors to act like one transistor that has a really stable operating point. Adding a second transistor to the signal path seems like it deviates from my belief that simpler is better, except that it works better."

2 transistors to act like 1 transistor? I can only draw 2, one is darlington and one is CFP. What is EquiLock looks like? Mr Hansen?

[Cauhtemoc]

Sorry to resurrect an old thread, but I came across this in the recent review of the KX-R preamp:

Key to VGT was Ayre's development of what they call EquiLock circuitry for the MX-R monoblock. "In a conventional circuit, the gain transistor has a load, usually either a resistor or a current source," Hansen said. "When the current through the gain transistor changes, then the voltage across the load also changes, which, in turn, means that the voltage across the gain transistor is changing. In fact, all of the parameters (transconductance, capacitance, etc.) vary when the voltage across the transistor varies.

"The EquiLock circuit adds another transistor between the gain transistor and the load. (In our case, the load is actually a current mirror.) This extra transistor holds the voltage of the gain transistor at a fixed level while still transmitting the changes in current to the load (the current mirror). By stabilizing the voltage across the gain transistor, all of the parameters of the gain transistor are also stabilized. The circuit is very similar to a cascode circuit, which has been used by other manufacturers, but EquiLock is an improvement over a conventional cascode circuit."

Sounds like it's similar to the enhanced cascode as described by Hawksford here.

[mlloyd1]

i don't think you'll find or receive a detailed description/schematic for the equilock topology, but you'll find some useful tidbits from charles scattered around in john's blowtorch thread.

perhaps another useful tip is don't be alarmed by use of a fair number of transistors, due to:
- fully balanced operation throughout
- high performance (i.e. better than the simple two transistor mirror) current mirrors
- cascoding
in other words, the "minimalist" approach was not necessarily a design goal.

justcallmedad posted an interesting gain stage in the blowtorch thread (?) worth investigating if you're curious about balanced, open loop, jfet input gain block architectures.

mlloyd1

[scott wurcer]

Originally posted by Cauhtemoc
Sorry to resurrect an old thread, but I came across this in the recent review of the KX-R preamp:



Sounds like it's similar to the enhanced cascode as described by Hawksford here.

Cascoding with a JFET tied back to the emitter does a pretty fine job without the extra biasing.

[BV]

Example for input diferential stage
http://www.diyaudio.com/forums/showt...50#post1656250

[jam]

Could it mean that the cascode ie referenced to the input fets rather than ground, which would improve linearity or the cascodes referenced to each other via a current source?

Jam

[nelsonvandal]

Originally posted by jam
Could it mean that the cascode ie referenced to the input fets rather than ground, which would improve linearity or the cascodes referenced to each other via a current source?

Jam

I was thinking the same. Like Borbely, and that memory distortion guy does it.

[Cauhtemoc]

Originally posted by jam
Could it mean that the cascode ie referenced to the input fets rather than ground, which would improve linearity or the cascodes referenced to each other via a current source?

Jam

This is the "enhanced cascode" described by Hawksford in the link I posted above.

[KBK]

With I/O included, there are only 36 different combinations possible with two transistors..so have at it.

Oh..wait a minute. Oops. Lots more. Oh well.

[janneman]

Didn't Nelson's Stasis do the same? Basically bootstrappping the Vds / Vce?

Jan Didden