Bora is a nice guy from Serbia - Yugoslávia

[Ultima Thule]

Yes Steven, that's the paper, thanks for clearing this out!

Bora,

have you tested in your Delta design with and without how the Hawksford distorstion correction circuit makes any difference, any listening experiences and/or measured?
BTW, those distortion and BW figures in your schematics, are those measured or from simulations?

Cheers Michael

[ChocoHolic]

Hi Darkfenriz,

I think you are right.
Also to my understanding this Hawksford error canceling diff amp turns signal polarity to the opposite of a normal diff amp.
...see figure 15 in Hawksford papers Chapter "5 Indirect Distorsion Cancellation Topologies"....

Let's go stage by stage:

When the input signal moves upwards:
==> Ic of Q1 increases, due to error cancelling diff arrangement.
==> Ube of Q11 increases.
==> Ic of Q11 increases.
==> Ic of Q12 increases.
==> Output moves downwards.

Input at Q1 is inverting.
Base of Q2 is noninverting input and getting the feedback signal.
...urghs... !!
Great that you noticed this point !

[ChocoHolic]

Originally posted by darkfenriz
However it could be easily fixed to make an amp work properly...

???
Are you sure?
I would expect that your proposal does not change the polarity, but
just resulting in less gain...

[darkfenriz]

Thank you ChocoHolic, my great tutor.
Yes, what I've drawn also isn't free from drawing mistake.
It should look like this: (attachment)
Good example of error correction amongst us.

[ChocoHolic]

Originally posted by darkfenriz
Thank you ChocoHolic, my great tutor.

...hope you are joking, we have better guys (and ladies !!!) here...

Originally posted by darkfenriz

Yes, what I've drawn also isn't free from drawing mistake.
It should look like this: (attachment)
Good example of error correction amongst us.

Yes this circuit would match to my understanding.

[lumanauw]

Hi, Steven,

What exactly this Delta (Hawksford) configuration do? I mean compared to standard 3 stages (+VBE multiplier biasing scheme)?

[Steven]

Hi Lumanauw,

Nothing special. The Delta is also a three stage amp, with differential input stage, VAS stage and output buffer stage.
The special thing is the use of a differential cross quad circuit as input amplifier. Vbe cancelling is used to decrease the distortion of the input differential amplifier. This works for relatively small differential input signals only, so do not use this for amplifiers without feedback to the input stage, or add the Vk voltage sources as described by Hawksford in his paper.
BTW This cross quad arangement is not invented by Hawksford, but exists already for decades, so better not call it a Hawksford configuration. Who knows who invented it?

Steven

[Ultima Thule]

Steven,

thanks for your input!
I just got curious to this circuit, would like to know if there's other people who have used it and what's their experiences with it.

As you mentioned Steven the Vk voltage can be "omitted" and the Base can be connected directly to the opposit transistors Collector if, as stated in the Hawksford paper, the signal is small, else there should be a Vk not equal to the Collector potential added if the input signal is larger.
I have to read the paper more carefully sometime to get into the subject.

But is the cross quad arrangement patented, does anybody know?
Well, next week I will get my "new" soundcard so hopefully I can start to make some real measurements.

Cheers Michael

[destroyer X]

But i change my mind.

You have so deep knowledge, that almost every amplifier is already known by you..... so.... the fun related discover things may had finish in your live...hummmm...

I will continue to be the way i am...as every new amplifier...new posted, seems a new world to me.

Now i will think to reach you related the respect the community have to you...but will not want anymore to have so deep knowledge...as things turns common.... loose taste this way.

No, there are not double ideas hidden in my text...the words have the correct meaning...really, you were someone to reach related know how, and this was perceived when i entered the forum. and i told you...in a post...and i was not kidding..this happened a year and half ago....you continue to be an explendid EE...but i think i will try to reach your respectability ...the knowledge i do not want anymore...better to have fun learning slowly.

I understand those things because i had passion to travel using Jet Planes.... and i entered a Japanese Company, i had to travell 15 days of each month.... all the pleasure finished, i had already travelled to every brazilian town.... i could identify and remenber the Pilots name...all thing turns very boering to me, I expect, and really wish that you continue to feel good constructing things, because your level is to design, and be distant from production... the pleasure to hold the soldering iron and sometimes to burn some finger..hehe.

regards,

Carlos

[Tom2]

Steven said,
BTW This cross quad arangement is not invented by Hawksford, but exists already for decades, so better not call it a Hawksford configuration. Who knows who invented it?

The earlist reference I have is:

Raimondo Caprio, "Precision Differential Voltage-Current Converter",
Electronics Letters, Vol.9 No.6, 22nd March 1973.

Papers with S. Pookaiyaudom as one of the authors that were published
in the later part of the 70's uses the topology.

I think Brett Wilson referred to the cross topology as the Pookaiyaudom
quad (or something like that) in the early 80's in one of his papers???

Tom