down the memory lane .......
post #1314 in F4 Beast Builders thread, brainchild of Mighty ZM, embracing PapaFE but introducing some twists and quirks
as it happened, written in very first post of this thread:
just imagine these (fully populated) sitting for 2 years or so..... I never connected them to power :
moral of the story :
- main purpose of Pa's hanging around here all these years is - him having fun
- second (less important to him, but illustrating his nature being partly Sisyphus-like) purpose of Pa's hanging around all these years is - him nudging us to use some brain, and not to fear of some gray smoke, here and there
That is very true.
I just acquired the "ability" to work with a PASS .8 stereo amplifier which I will turn into proper monoblocks, really looking forward to that. I will give the XA252 the same treatment such that the PSU and power capability will be similar. That way, the sound signature of either will not be influenced by a difference in the PSU (more than necessary) and as a final touch, the attenuation will be heavily inspired by Iron Pumpkin / Turtle and once these parts are finalized, my hunt and tracking down which amplifier(s) to build my system around will be over. This is the final mile.
I'm so happy I stuck around. What a remarkable time to be alive.
I just acquired the "ability" to work with a PASS .8 stereo amplifier which I will turn into proper monoblocks, really looking forward to that. I will give the XA252 the same treatment such that the PSU and power capability will be similar. That way, the sound signature of either will not be influenced by a difference in the PSU (more than necessary) and as a final touch, the attenuation will be heavily inspired by Iron Pumpkin / Turtle and once these parts are finalized, my hunt and tracking down which amplifier(s) to build my system around will be over. This is the final mile.
I'm so happy I stuck around. What a remarkable time to be alive.
Jazz is not dead, it just smells funny
it really applies on any time; I believe we're going to have tremendous fun even after being such alive
Pass as you know, is a goldmine which we should travel through while we can. Every gold pocket runs out eventually
down the memory lane .......
post #1314 in F4 Beast Builders thread, brainchild of Mighty ZM, embracing PapaFE but introducing some twists and quirks
as it happened, written in very first post of this thread:
just imagine these (fully populated) sitting for 2 years or so..... I never connected them to power :
View attachment 1202099
moral of the story :
- main purpose of Pa's hanging around here all these years is - him having fun
- second (less important to him, but illustrating his nature being partly Sisyphus-like) purpose of Pa's hanging around all these years is - him nudging us to use some brain, and not to fear of some gray smoke, here and there
a critter
I believe I still have them in drawer or box, stripped of everything but resistors
While we are down the rabbit hole. If all else is equal - Have anyone tested and reported any differences and if so, what ?
Yamaha M-5000 use LTP in their buffer and that amplifier sounds magnificent
all roads are leading to Rome
final result(s) with any construction is sum of all compromises made along the way
major compromise I'm forced to make all the time is sort of induced by few things:
Yore Toshiba JFets are scarce
modern audio*** JFets are exclusively N channel
***meaning - Idss, dissipation, xconductance - all being in range that simplest arrangements are giving satisfactory outcome
final result(s) with any construction is sum of all compromises made along the way
major compromise I'm forced to make all the time is sort of induced by few things:
Yore Toshiba JFets are scarce
modern audio*** JFets are exclusively N channel
***meaning - Idss, dissipation, xconductance - all being in range that simplest arrangements are giving satisfactory outcome
Well I've been staring at the XA252 schematic(s) for some time and have extracted a BOM (which I find very helpful to understand the circuit and of course order parts) but have a couple of open points that I would like the community here to give some insight on if they are willing.
1.) The TPC 817B is no longer available. Any suggestions on a replacement? (I have a couple of 4N35 left from M2 build. I know different footprint)
2) Component values: Is 100pF correct for C8, Is 4p7 correct for the feedback cap C5?
3) Thermal considerations: I learned from the discussion in this thread that max rails are +-35V and a reasonable Iq max is 2A.
-are we talking 70W for M2 and M3 each?
-Is a standard on board heat sink for TO-220 packages (H=12.7 mm L= 19mm) adequate for Q9? Q1&Q2?
-What about M1?
Lastly any guidance on the footprint sizes selected for the Zobel componentent C19 and R64?
Thanks to all for their insight to date and a special thanks to ZM. Without whom none of this would happen.
1.) The TPC 817B is no longer available. Any suggestions on a replacement? (I have a couple of 4N35 left from M2 build. I know different footprint)
2) Component values: Is 100pF correct for C8, Is 4p7 correct for the feedback cap C5?
3) Thermal considerations: I learned from the discussion in this thread that max rails are +-35V and a reasonable Iq max is 2A.
-are we talking 70W for M2 and M3 each?
-Is a standard on board heat sink for TO-220 packages (H=12.7 mm L= 19mm) adequate for Q9? Q1&Q2?
-What about M1?
Lastly any guidance on the footprint sizes selected for the Zobel componentent C19 and R64?
Thanks to all for their insight to date and a special thanks to ZM. Without whom none of this would happen.
.....which is exactly proper approach to start ....... everything
1. there are myriad 817* optocouplers around - it doesn't need to be TPC; for suffix - use either B or C
2. 100pF C8 yes, 4p7 C5 yes ; for peace of mind, order 100V
3.
- M2 and M3, 70W, yes - they'll be happy critters - no isolation pads, just goop
- use bigger one for Q1,Q2 pair - or pair of these back to back; for Q9 that size is proper
- M1, that size is proper
- Zobel is not used/populated; footprint/place "just in case"
Hi ZM,
You have outdone yourself again!
I actually purchased speakers which are a rather difficult load to the amplifier, Thiel CS 2.3. They work wonderfully together. I think this will remain in my main system for a long while.
To achieve such results with DIY is quite extraordinary. Thank you and pa (again!).
BUT....it runs hot! I wish to bias it at 1A but the trimpot only allows me 1.15A. Could you point me which resistor and what value I could change to be in the right bracket for bias adjustment?
You have outdone yourself again!
I actually purchased speakers which are a rather difficult load to the amplifier, Thiel CS 2.3. They work wonderfully together. I think this will remain in my main system for a long while.
To achieve such results with DIY is quite extraordinary. Thank you and pa (again!).
BUT....it runs hot! I wish to bias it at 1A but the trimpot only allows me 1.15A. Could you point me which resistor and what value I could change to be in the right bracket for bias adjustment?
you can try to increase r28(the one in series with p2) to 1k8.
Depending on your listening level 1A bias may be pretty low for your speakers which go as low as 2ohm( https://www.stereophile.com/content/thiel-cs23-loudspeaker-measurements ). The amp will leave class A at 10-15w into that load.
Depending on your listening level 1A bias may be pretty low for your speakers which go as low as 2ohm( https://www.stereophile.com/content/thiel-cs23-loudspeaker-measurements ). The amp will leave class A at 10-15w into that load.
Thanks Schultz! I was still doubting to make monoblocks as it sounds so good as is. Well, your answer might have convinced me to do so.
I guess especially with these speakers it makes sense to do that.
Btw, currently I have both channels biased at 1.3A but the Pass knockoff heatsinks do not dissipate that well. Heatsink temp is 61C....
Sounds great though😈
I guess especially with these speakers it makes sense to do that.
Btw, currently I have both channels biased at 1.3A but the Pass knockoff heatsinks do not dissipate that well. Heatsink temp is 61C....
Sounds great though😈
What are your rail voltages? For your actual speakers 30vdc would be perfect since they mostly stay under 5ohm.
You could help the airflow with a babysitter.
Most of the times 5-10w are more than enough.
I know it sounds great, I have mine singing for a month now 🙂
You could help the airflow with a babysitter.
Most of the times 5-10w are more than enough.
I know it sounds great, I have mine singing for a month now 🙂