Ayre's EquiLock, what is it?

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lumanauw

lumanauw

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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."
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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?
 
C

Cauhtemoc

Member
Joined 2007
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."
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Sounds like it's similar to the enhanced cascode as described by Hawksford here.
 
mlloyd1

mlloyd1

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Joined 2001
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
 
courage

courage

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Joined 2006
Seems like this thread died a slow one, but has anyone further investigated the Hansen's equilock topology and what are your conclusions/findings. I'm currently in the proces of looking into this further, but it would be a waste to find out the wheel again.

Hope someone has some fresh additional info and maybe Charles himself will throw a few crumbs for further digestion.
 
courage

courage

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Joined 2006
Seems like Charles visits the forum every now and then, but not as frequent as before.

I mainly read most of the revieuws of the KX-R and MX-R which sometimes explain the basic route Charles has taken in the design of these amps. I'm also aware of other threads dealing with, for instance, the On Semi ThermalTrak devices and the proper use and implementation.

Also the "Variable Gain Transimpedance" implementation on the KX-R seems interesting to further explore. It seems like none of the threads dealing with these issues seem to be interesting enough as they came to a sudden halt.

Personally I find Charles his approach refreshing and quite interesting to explore. And as usual any useful information which gives room for further discussion is welcome.

mlloyd 1 and stinius thanks for your response.
 
S

stinius

Disabled Account
Joined 2008
courage said:
Seems like Charles visits the forum every now and then, but not as frequent as before.

I mainly read most of the revieuws of the KX-R and MX-R which sometimes explain the basic route Charles has taken in the design of these amps. I'm also aware of other threads dealing with, for instance, the On Semi ThermalTrak devices and the proper use and implementation.

Also the "Variable Gain Transimpedance" implementation on the KX-R seems interesting to further explore. It seems like none of the threads dealing with these issues seem to be interesting enough as they came to a sudden halt.

Personally I find Charles his approach refreshing and quite interesting to explore. And as usual any useful information which gives room for further discussion is welcome.

mlloyd 1 and stinius thanks for your response.
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Franklin

I have tried to discuss it in the BT thread, but without any luck.
I agree it’s an interesting subject, so keeping the thread alive is important.

BTW: you are more than welcome to post in the BT thread; bear was a bit hasty in his reply to you.

Cheers
 
mlloyd1

mlloyd1

Member
Joined 2001
franklin:

have you built any of the circuits posted in the bt thread that charles commented on? i'd like to, but thanks to economics, i work 250+ miles from my home (and my basement full of all my goodies) so my experimenting is VERY limited these days :bawling:

i played around in ltspice with a preamp circuit i think you posted in the bt thread (fully balanced i/o, quad comp jfet input, cascode bipolar current mirrors, no loop feedback, etc.) and added a couple of diamond buffer output stages (yeah, it was a lot of parts). i often wonder how that would sound ...

mlloyd1

btw, although great for audio books, i never realized how much i despise listening to music in mp3 format, now that i'm forced to either do that or nothing :hot:
 
courage

courage

Member
Joined 2006
stinius said:



Franklin

I have tried to discuss it in the BT thread, but without any luck.
I agree it’s an interesting subject, so keeping the thread alive is important.

BTW: you are more than welcome to post in the BT thread; bear was a bit hasty in his reply to you.

Cheers
Click to expand...

Stinius,

I still follow the BT thread, but don't feel like participating there anymore. It has grown into an ego thing and that's not my cup of tea. Besides I focus on Charles's his designs as he takes things a step further or in another direction if I may put it this way. But thanks for your encouragement. Appreciate it.


mlloyd1 said:
franklin:

have you built any of the circuits posted in the bt thread that charles commented on? i'd like to, but thanks to economics, i work 250+ miles from my home (and my basement full of all my goodies) so my experimenting is VERY limited these days :bawling:

i played around in ltspice with a preamp circuit i think you posted in the bt thread (fully balanced i/o, quad comp jfet input, cascode bipolar current mirrors, no loop feedback, etc.) and added a couple of diamond buffer output stages (yeah, it was a lot of parts). i often wonder how that would sound ...

mlloyd1

btw, although great for audio books, i never realized how much i despise listening to music in mp3 format, now that i'm forced to either do that or nothing :hot:
Click to expand...

mlloyd 1,

I did indeed post a couple of open loop line stages in the BT thread. However the availability of hard-to-get components made me change my idea to build the circuits. As I got more and more interested in Charles's approach, I started to focus more on his current designs. It is also a possibility to take the circuit that already existed a step further. I mainly do simulations at the moment, but sometimes the lack of proper spice models can be frustrating.

I find the open loop concept quite interesting as I can vagely imagine how it could sound. But to benefit from this approach both the pre and power amp should be open loop.

Are you willing to share a schematic of your current circuit here or off the forum? I basically try to grasp Charles his approach by exploreing his V3 pre and power amp. Although his designs have evolved and improved, it's a good start.

I resisted MP3 for quite some time, but when travelling long distances it's good to have some music. I agree it can be horrible to listen too. I can also do without and still enjoy good music though by listening to music inside my head which comes in every flavour I wish to hear at that moment and as clear as how live music can sound. Have had this ability for quite some years now. Can also hear totally new music in every genre I wish. Sounds quite spooky, don't it?

Take care.
 
mlloyd1

mlloyd1

Member
Joined 2001
i tried to search for the particular circuit i referred to earlier that was posted in the bt thread and found it was by justcallmedad instead. i haven't actually found it yet, but i know it's there.

really, it is ...
:)

i'll see what i can do about posting what i've got. might take a while to find it (spread across 3 non-networked computers).

mlloyd1
 
mlloyd1

mlloyd1

Member
Joined 2001
hmmm ....
after a considerable amount of searching, i see the references but the actual schematics themselves have disappeared (probably related to the disappearance of justcallmedad's web site that was hosting them).

at least i know i'm not crazy or senile or whatever ...

mlloyd1
 
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