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Zen Mod 11th June 2021 06:15 PM

Babelfish XA252 / Babelfish XA252 SIT / Babelfish XA252 SET
 
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Few years ago, we had enormous fun in funny named thread : F4 Beast Builders

Well, you can call it Group of Hysteric Housewives Brainstorming :rofl: :p

Result of that was that I had myriad of back of napkin sketches, and after these I started simulating ...... and simulating ... and simulating

After myriad of sims ( out of sheer enthusiasm I even made pcb files for some of iterations), I finally had made nice smallish channel pcbs, containing OS having different-ish approach to biasing than Papa's original XA25, while FE was in principle same as Papa's, but with few beautiful quirks, of which I was damn proud (yup, Mighty ZM reinventing Da Wheel, time and time again)

And they were sitting, populated, on my shelf ........ always being pushed to bottom of list; I knew they would work, but somehow I wasn't content with overall picture

Now, recently - besides revising biasing mechanismus for SissySIT ( resulting in R.3) and few other amps, I also made FE called Plethora of Pinjatas ( or just Plethora, short) and found interesting to combine it in sitting Babelfish XA25 project

Plethora Fe having both SE and Bal inputs as matter of choice, called to adding another "2" in name , so result is Babelfish XA252

Plan is also to have iteration of DEF OS ( real SIT, no emulation in form of Schaded Mosfet), thus addition of "SIT" in name, so Babelfish XA252 / SIT

Find enclosed cumulative schematic, and will do edits of this post, if and when needed

OK1-OK2-TH1 .......... 10A limiting circuit, Savior of Our Souls, blatantly stolen from Pa :p


amp is phase correct , Papa's fave gigglywiggly graphs sez that 2nd is negative phase

all measurements made with SE input, neg leg input grounded


edit on 18.07.2021.

Babelfish XA252 SIT - post #64 Babelfish XA252 / Babelfish XA252 SIT / Babelfish XA252 SET

Babelfish XA252 SET - post #119 Babelfish XA252 / Babelfish XA252 SIT / Babelfish XA252 SET

Zen Mod 11th June 2021 06:19 PM

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Now, for clarity sake, there is edited schm, parts needed for SIT iteration omitted

few more funny pics, too

Zen Mod 11th June 2021 06:25 PM

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I did planned before to make it, but finally made T-Bed 2 , as proper cradle for prototyping this

from one of pics, you can clearly see that ZM is Chicken , executing first power up and settings with IRFP240/9140 and 2A fuses in rails...... did it with smallish Iq, and later - when I was happy camper, changed to Biguns

Zen Mod 11th June 2021 06:36 PM

Graphs , 8R load, BFR=22R
 
5 Attachment(s)
FE is made as more or less basic LTP thingy; though, I did wanted to have possibility of altering THD level by changing OLG in simple and predictable way - which I made in also basic way - tearing LTP halves ( each halve having own CCS) and introducing common degeneration resistor ( practically changing length of effective Tail of LTP) , which I then named as Beauty Factor Resistor, short BFR

as you will see, changing value of that resistor is chhanging OLG, thus changing amount of overall NFB, and as result we have lesser or higher THD level

Luckily, Spectra is not changing, and that was a goal :clown:

now - set of measurements with highest possible OLG - BFR s 22R

Rails are 30Vdc ( amp projected to work with rails of 30-35Vdc with no changes)

Iq 1A7

DC offset and Iq practically not changing in temperature domain

While varying mains voltage (nominal 230Vac) between 200Vac and 255Vac - DC offset is changing some 20mV, while Iq is practically not changing

Good enough for me :devily:

Load for these graphs is 8R; each graph is having title captured, so you can see what/how much

Zen Mod 11th June 2021 06:38 PM

Graphs , 8R load, BFR=22R, continued
 
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too many pics for one post, so continued

due to 30Vdc rails, clipping smidge above 40W

with 35Vdc rails, clip near 55W

who needs that ?

Zen Mod 11th June 2021 06:41 PM

Graphs , 4R load, BFR=22R
 
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everything the same, load 4R

Zen Mod 11th June 2021 06:43 PM

Graphs , 4R load, BFR=22R, continued
 
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again

I didn't investigated where is bloody clipping

Meant that 70W is already enough

Zen Mod 11th June 2021 06:45 PM

Graphs , 8R load, BFR=510R, continued
 
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Everything the same, but BFR changed to 510R, that being opposite extreme to 22R - practically lowest OLG which I considered

Zen Mod 11th June 2021 06:46 PM

Graphs , 8R load, BFR=510R, continued
 
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more of these

Zen Mod 11th June 2021 06:48 PM

Graphs , 4R load, BFR=510R
 
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everything same as previous, load changed to 4R


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