I believe everyone got proper pack of files in e-mail , in case of later revisions
not that many that I can count of, I mean - major being inclusion of small mosfet in place of zener
not substantial, more like my OCD kicking in
easiest to spot any difference, in case of doubt, simply looking at "parts placement" pic
not that many that I can count of, I mean - major being inclusion of small mosfet in place of zener
not substantial, more like my OCD kicking in
easiest to spot any difference, in case of doubt, simply looking at "parts placement" pic
re-check all semis, at least with diode test
if not finding evident shorts, just fire it up, completed with outputs
you can temporary put 2A to 2A5 fast fuses in rails (after cap bank!)
but, be sure that you did mount all parts per SET schematic appropriate for your boards; if you don't see part on schematic, do not mount it on pcb, that simple
I tested my Babelfish SET board yesterday with IRFP140/9140 mosfets. Rail voltages are about 24-26 V. When I switched on this circuit with the lowest Iq then DMM reads 0,145V between 0,12 Ohm resistor. This should give me about 1,2 A bias? Mosfets get hot quite quickly so I tested only about 30 seconds. Lights are on and offset is also quite ok about 0,015V or less.
Are these Iq values normal? Should I use higher resistor value in P2 place?
Are these Iq values normal? Should I use higher resistor value in P2 place?
1.2A seems perfectly fine to me.
1.2A x 26V ~30W of dissipation for a TO247 package. Good heat conduction to a large heatsink is a must.
1.2A x 26V ~30W of dissipation for a TO247 package. Good heat conduction to a large heatsink is a must.
I saw DMM numbers and quickly doing the math to calculate the bias. Then I remembered Zen Mod said 1A for bias with these heatsinks. Then I mounted these mosfets to 5U/500mm heatsinks because I could go not lower bias to test this wonderful looking Babelfish.
So the minimum bias is about 1,2A? Does it also depends on the mosfets?
You are tempting fate by not attaching the mosfets to a heatsink even for 1sec, let alone 30. 😬
I didn't invest too much time thinking about how much lower than, say, 1A5 I can go
I know it can go lower than that, but no reason to remember exact number
anyhow, whatever reason, it's pretty simple to alter few resistors to allow loooow Iq
I wrote somewhere few times - my friend wanted to play and make his own pcbs ........ then he was so fired up so couldn't wait to get 5U/500 case, mounted it all in 4U/400 case he had on disposal, set it to 1A Iq , being happy camper ...
Babelfish SET version is now singing. For the output I am using FQA36P15 and FQA46N15 mosfets. Rail voltages +-23V. What would be a good Iq A for the bias for these mosfets? I am using 5U/500 case. Q9 and M2 are SET parts and these heatsinks are 45 degrees celcius. Is this normal?
If I like to add more ZEN, sugar, color and warmth to the sound then what changes I can try for that in the XA252 SET schematic? 😆
If I like to add more ZEN, sugar, color and warmth to the sound then what changes I can try for that in the XA252 SET schematic? 😆
1A8 to 2A sounds reasonable, with Keratherm or Alumina pads
your temperature is, say, 36.9C
either convert it to XA252 SIT .......... or build SissySIT (42)
My room temperature is about 21C. If I touch these Q9 and M2 heatsinkst then they are quite hot and then I measured their heat with a DMM wire probe then I get about 45C.
I am using this SP2000, thermal Conductivity: 3.5 W/m-K.
What kind of SIT mosfet do you suggested?
Does GBR resitor 0R or 15R affect the sound? What do you suggest to use here?
Does DN2540 affects the sound? Only adding more H2?
Tokin; everything explained in thread first posts
no; Beauty Factor resistor is doing that - more Ohms, more Sugar ........ but - don't bother, differences are minor
it's there for different purpose ........ level shifter and buffer, necessary to drive either Schade-d mosfet or SIT
idea is - it doing own purpose but must be sonically invisible, meaning - no ill effects, just positive ones
to repeat - if you want more Sugar, either go to SIT, or build different amp
Could you tell me more about the sound differences and what you like both of them?
As Aleksandar implied above, the Sissy is sweeter and to me more involving. The XA252 delivers the punch in spades and in my system has better bass.
Compromise might be to build XA252SIT. I didn't go that path because I had the Sissy. In either case both amps make want to listen and keep that foot tapping.
Compromise might be to build XA252SIT. I didn't go that path because I had the Sissy. In either case both amps make want to listen and keep that foot tapping.
as Bubba said
SissySIT is 18 special watts, while XA252 is at least double, depending of iteration
besides that, driving capability is way on side of XA
with proper speakers, SissySIT is best to combine with neutral sources and preamps, itsel being all Honey and more .......... while XA is allowing some Honey in preceding gadgets
for both, all measurements and graphs are in start of corresponding threads
some glue, to help in data analyzing:
https://www.firstwatt.com/wp-content/uploads/2023/12/art_cas_2015.pdf
https://www.firstwatt.com/wp-content/uploads/2023/12/art_sweet_spot.pdf
https://www.firstwatt.com/wp-content/uploads/2023/12/art_peanut_butter.pdf
SissySIT is 18 special watts, while XA252 is at least double, depending of iteration
besides that, driving capability is way on side of XA
with proper speakers, SissySIT is best to combine with neutral sources and preamps, itsel being all Honey and more .......... while XA is allowing some Honey in preceding gadgets
for both, all measurements and graphs are in start of corresponding threads
some glue, to help in data analyzing:
https://www.firstwatt.com/wp-content/uploads/2023/12/art_cas_2015.pdf
https://www.firstwatt.com/wp-content/uploads/2023/12/art_sweet_spot.pdf
https://www.firstwatt.com/wp-content/uploads/2023/12/art_peanut_butter.pdf
Is there a way that I can turn it to positive 2nd phase to compare these two different versions which I like more?
Any sound difference between mosfets and IXYS pucks in SET version?
Per Papa's lectures, to flip phase of dominant harmonic, all you need is to flip phase at speaker terminals
I didn't pursue that difference; initial tests were made with IRFP in place of IXYS pucks just because I was Chicken while concept of amp was still unproven and, as soon I've seen nothing smoking, TO247s were changed to pucks
Anyhow, there is Plethora of Pinjatas, which is practically Mini XA252; with my speakers (big and ballsy and sensitive) I'm finding that sole significant difference between Mini and Real McCay is in heat emanated in room
This time I really hurt my Babelfish. 
After making changes in PSU I missed to link GND wire to the gnd hub. 😡 Now a little bit of sound comes out like from a behind of thousands curtains. What part to look up that has been testroid if powering up Babelfish without a GND?
@Zen Mod I am really testing your all mighty knowledge.
After making changes in PSU I missed to link GND wire to the gnd hub. 😡 Now a little bit of sound comes out like from a behind of thousands curtains. What part to look up that has been testroid if powering up Babelfish without a GND?@Zen Mod I am really testing your all mighty knowledge.