from wayy back, I know, but still. This resonates with me strongly.
TYVM for sharing your ideas and your explanations.
Kind regards,
Drew
That's a workbench to be proud of! My 'desk' is only as neat as yours on it's best days, otherwise there are usually items scattered everywhere when I am tinkering with something - which happens to be all the time unfortunately.
Great job and congratulations on 2 successfully powered channels! Fugly deserved!
Cheers,
Stephen
Great job and congratulations on 2 successfully powered channels! Fugly deserved!
Cheers,
Stephen
Hi ZM
Both channels are fired up now for a couple of hours.
I have the lower and upper covers in place with feet under amp allowing air circulation on the bench.
My DVM does have a contact type thermocouple to measure temps with.
I took measurements several times as best as I could with the top cover in place to mimic operation.
Ambient temp in the room where I work is about 22 C (or 72 F). Its in the same space as my furnace.
I would say this temp is a little higher than the average of what we would try to maintain in the house with AC/Heat.
The top center of the heatsinks appear to have stabilized at around 53 C (or about 127 F).
I can confirm that my hands on the top center hurt and have to be pulled away by the time 5 seconds pass…so Crikey to Bloody Hot!?
I was able to feed the thermocouple down through the ventilation slots in the top cover and take temps at a few different places.
The temp in the center of the head on the mosfet mounting screws was the hottest point at about 61-63.5 C.
I took the temp of the mosfet cases along their top edge in the center. The range was 59-61 C.
I also took the temp on the heatsink right above the top edge of the Keratherm pads on center. The range was 57-58 C.
The Iq on both channels is set to 665-670mV.
I have zeroed out DC offset on both channels.
Not sure how much higher you would recommend going…or not?
P.S. Yes I think living with the all irfp version for a while is a good idea. It’s been a long build and I want some joy. Besides, I already have a second stereo case built along with a bit of its power supply. I can use that for Semisouth down once its tested and then compare the two amps.
Both channels are fired up now for a couple of hours.
I have the lower and upper covers in place with feet under amp allowing air circulation on the bench.
My DVM does have a contact type thermocouple to measure temps with.
I took measurements several times as best as I could with the top cover in place to mimic operation.
Ambient temp in the room where I work is about 22 C (or 72 F). Its in the same space as my furnace.
I would say this temp is a little higher than the average of what we would try to maintain in the house with AC/Heat.
The top center of the heatsinks appear to have stabilized at around 53 C (or about 127 F).
I can confirm that my hands on the top center hurt and have to be pulled away by the time 5 seconds pass…so Crikey to Bloody Hot!?
I was able to feed the thermocouple down through the ventilation slots in the top cover and take temps at a few different places.
The temp in the center of the head on the mosfet mounting screws was the hottest point at about 61-63.5 C.
I took the temp of the mosfet cases along their top edge in the center. The range was 59-61 C.
I also took the temp on the heatsink right above the top edge of the Keratherm pads on center. The range was 57-58 C.
The Iq on both channels is set to 665-670mV.
I have zeroed out DC offset on both channels.
Not sure how much higher you would recommend going…or not?
P.S. Yes I think living with the all irfp version for a while is a good idea. It’s been a long build and I want some joy. Besides, I already have a second stereo case built along with a bit of its power supply. I can use that for Semisouth down once its tested and then compare the two amps.
Attachments
Hi twitchie
Thanks for the kind words of support. I am eager to hear some tunes.
I wish I had more space and the energy/determination to really organize things. I do go through cycles…but have way too much stuff horded and not so much room.
Thanks for the kind words of support. I am eager to hear some tunes.
I wish I had more space and the energy/determination to really organize things. I do go through cycles…but have way too much stuff horded and not so much room.
chrome, you're all good - now just enjoy
no upping Iq, no room for that, according to heatsink temperature
let her be a judge how successful and enjoyable new amp is
and send her my Ciao! ........ I'm always remembering her being absolute Sport, near back stairs in BAF building, while her Boy is having own fun
that's Love
🙂
no upping Iq, no room for that, according to heatsink temperature
let her be a judge how successful and enjoyable new amp is
and send her my Ciao! ........ I'm always remembering her being absolute Sport, near back stairs in BAF building, while her Boy is having own fun
that's Love
🙂
Hi ZM
Yes I am a very lucky man to have such a supportive and encouraging wife.
She has some plans this weekend so we’ll see when I can find time to get the amp hooked up for a listen.
I had hoped these cases would dissipate heat a little better…I knew they weren’t optimal…but I’m an artist/tinkerer not an engineer.
I bought the heatsinks years ago when I first took an interest in building my own amps/cases and was trying to mimic the 4U/300 because it was recommended for quite a few of the store amps.
After this project started I decided to take advantage of a Madisound sale and picked up a pair of 4U/400 cases as it was pretty clear the SissySIT and LuDef I was interested in would need bigger case.
I’m gonna run with it for now, but I am wondering if I should consider these cases a temporary home?
There’s always the option of adding fans to the case or a babysitter. I did that with my F2Js using the same sinks in monoblock cases I built.
I’m wondering where I stand in relation to the bias “sweet spot” with only 670mV (as opposed to the 850mV target) across R136/236?
I thought other builders mentioned they were pushing an Iq of 1.6-1.8…but I don’t know where I stand because I don’t know the math.
I keep trying to learn and make fewer mistakes…I suppose one can’t happen without the other.
Maybe I have some other amp boards hoarded that would create less heat that I could “hermit crab” into these cases if necessary.
I did pick up some Aleph J boards from the store during a sale…feel almost guilty for having not built one yet.
Yes I am a very lucky man to have such a supportive and encouraging wife.
She has some plans this weekend so we’ll see when I can find time to get the amp hooked up for a listen.
I had hoped these cases would dissipate heat a little better…I knew they weren’t optimal…but I’m an artist/tinkerer not an engineer.
I bought the heatsinks years ago when I first took an interest in building my own amps/cases and was trying to mimic the 4U/300 because it was recommended for quite a few of the store amps.
After this project started I decided to take advantage of a Madisound sale and picked up a pair of 4U/400 cases as it was pretty clear the SissySIT and LuDef I was interested in would need bigger case.
I’m gonna run with it for now, but I am wondering if I should consider these cases a temporary home?
There’s always the option of adding fans to the case or a babysitter. I did that with my F2Js using the same sinks in monoblock cases I built.
I’m wondering where I stand in relation to the bias “sweet spot” with only 670mV (as opposed to the 850mV target) across R136/236?
I thought other builders mentioned they were pushing an Iq of 1.6-1.8…but I don’t know where I stand because I don’t know the math.
I keep trying to learn and make fewer mistakes…I suppose one can’t happen without the other.
Maybe I have some other amp boards hoarded that would create less heat that I could “hermit crab” into these cases if necessary.
I did pick up some Aleph J boards from the store during a sale…feel almost guilty for having not built one yet.
amount of Iq is not so critical as long you're having no impression of amps going out fo setam, with your speakers and SPL you're used on
670mV across 0R5 means 1A34 of Iq, little less than I'm used but no biggie
make simple Babysitter and see where you can push it regarding Iq to still have no more than 55C at sinks
simple as that .....
Boyz form Store - as I'm preaching all these years - made somewhat wrong decision to choose 4U/300 as Store Swiss Knife case, simply because 4U/400 is so much better not just heatsink wise but also giving 100mm more of precious space inside - easier to work, better for more air between modules, better fopr more space between Donut and things which can be influenced with
so, in short - with Babysitter - you'll be good, no need to relocate anything
math - simple - 2 1R resistors in parallel giving 0R5
as I=U/R , calc is easy - Iq=0V67/0R5 = 1A34
so you can easily calc whatever you want to meet or you're going to meet while chasing 55C at sinks
precision and sense for details is much needed, but we are still not dealing with Dialysis equipment, as Pa is used to mock us
670mV across 0R5 means 1A34 of Iq, little less than I'm used but no biggie
make simple Babysitter and see where you can push it regarding Iq to still have no more than 55C at sinks
simple as that .....
Boyz form Store - as I'm preaching all these years - made somewhat wrong decision to choose 4U/300 as Store Swiss Knife case, simply because 4U/400 is so much better not just heatsink wise but also giving 100mm more of precious space inside - easier to work, better for more air between modules, better fopr more space between Donut and things which can be influenced with
so, in short - with Babysitter - you'll be good, no need to relocate anything
math - simple - 2 1R resistors in parallel giving 0R5
as I=U/R , calc is easy - Iq=0V67/0R5 = 1A34
so you can easily calc whatever you want to meet or you're going to meet while chasing 55C at sinks
precision and sense for details is much needed, but we are still not dealing with Dialysis equipment, as Pa is used to mock us
not yet
multitasking these days got better of me; sometimes I'm finding my self working all the time, assembling and preparing and packing, but somehow just not being able to catch P.O. working hours
not counting on fact that delivery of (regularly trivia) itsybitsies is somewhat erratic ..... fact that I' ordering new quantity (and always bigger number) almost when I get one, is not particularly helping
it seems only EMP effect would be worse than present situation
yesterday I got 200pcs of ULN2803 ...... it'll last at least few years, but what the heck ...... I did learn some from Mighty Pa - when you see them cheap, buy Drekload and laugh
multitasking these days got better of me; sometimes I'm finding my self working all the time, assembling and preparing and packing, but somehow just not being able to catch P.O. working hours
not counting on fact that delivery of (regularly trivia) itsybitsies is somewhat erratic ..... fact that I' ordering new quantity (and always bigger number) almost when I get one, is not particularly helping
it seems only EMP effect would be worse than present situation
yesterday I got 200pcs of ULN2803 ...... it'll last at least few years, but what the heck ...... I did learn some from Mighty Pa - when you see them cheap, buy Drekload and laugh
Oooooooooooooh - I saw your trade on the forum. I was hoping they might go into this project. You are in for a real treat. 😀 😀
Yes I hope this too
And I'm hoping for a review like the USSA-5. Maybe even with a comparison of the two... 😎
And I'm hoping for a review like the USSA-5. Maybe even with a comparison of the two... 😎
Choky,not yet
multitasking these days got better of me; sometimes I'm finding my self working all the time, assembling and preparing and packing, but somehow just not being able to catch P.O. working hours
not counting on fact that delivery of (regularly trivia) itsybitsies is somewhat erratic ..... fact that I' ordering new quantity (and always bigger number) almost when I get one, is not particularly helping
it seems only EMP effect would be worse than present situation
Good, and don't worry about time as I have plenty of projects in the interim....
it's better with smd critters
more, the merrier
save those TO92s for something where you don;t have a choice
more, the merrier
save those TO92s for something where you don;t have a choice
I think I'll try 170s to start and go from there....maybe I want more distortion....maybe not. That's the fun of this hobby!as I promised (to my self , in first place ) , today I did change pair of 2SK170BL in input LTP position , for 2+2 pcs of 2SK2145BL
previous idea was to up LTP current from 10mA to 20mA , resulting in healthy 50mW per tiny bugger , but later decided to try Papa's approach , of doubling input JFets , while Iq keeping at same level as for single pair
that way - due to increased combined xconductance , OLG is rising , and without change of NFB network , NFB is rising , so we can expect lower level of THD
is it good thing or not - sound wise , who cares ...... I have all the time left to humanity to try that ...... later
My first sound test was a failure.
The amp is humming/buzzing through speakers like crazy.
I had been working out issues with case work and etc after I fired it up to equilibrium a few times last week.
Before I hooked up a source and test speakers I fired it again today and monitored offset.
The amp seems to function…music plays from my phone through my test speakers… but is making a loud humming/buzzing noise as I said.
I started moving wires to see if anything changed in the sound.
There was a difference when I placed my hand over one of the transformers and minor changes when shifting the supply wires around.
I can rotate the transformers a bit…but it made no difference.
The transformers do hum a bit…and there is a slight change to the hum if I short the inputs.
At one point I was playing music through one channel and I went to test the offset on the other channel…for some reason, as soon as I touched the DVM probe to either binding post the noise dropped drastically.
I don’t really know where to start here…kind of distraught after so much work to get to this point.
The amp is humming/buzzing through speakers like crazy.
I had been working out issues with case work and etc after I fired it up to equilibrium a few times last week.
Before I hooked up a source and test speakers I fired it again today and monitored offset.
The amp seems to function…music plays from my phone through my test speakers… but is making a loud humming/buzzing noise as I said.
I started moving wires to see if anything changed in the sound.
There was a difference when I placed my hand over one of the transformers and minor changes when shifting the supply wires around.
I can rotate the transformers a bit…but it made no difference.
The transformers do hum a bit…and there is a slight change to the hum if I short the inputs.
At one point I was playing music through one channel and I went to test the offset on the other channel…for some reason, as soon as I touched the DVM probe to either binding post the noise dropped drastically.
I don’t really know where to start here…kind of distraught after so much work to get to this point.
