Normally you do not need too. In fact the thermistor use is more for the Mosfet driver than the output Mosfet (lateral mosfet does not require temperature compensation). Values of Resistors/thermistor arrangement are adjusted for heatsink temperature instead of Mosfet driver mainly to slow down reaction.
Fab
I did the biasing again and I got it all stable (at least for now).
both boards are set to 50mv bias with dc offset of 0.5-0.8mv ( sometimes it goes back and forth between 0 & 1mv ).
now that i have the heatsink vertical, the M1 and M2 temperature is identical on both boards, around 120 to 125F and the heatsink is around 115F
Thanks to Project16, that was a good point
I ll have it burn in and finish the tests and do the final biasing next few days
Thanks everybody for all the help and support and sorry ggetzoff for hijacking your thread.
please see the attachments.
both boards are set to 50mv bias with dc offset of 0.5-0.8mv ( sometimes it goes back and forth between 0 & 1mv ).
now that i have the heatsink vertical, the M1 and M2 temperature is identical on both boards, around 120 to 125F and the heatsink is around 115F
Thanks to Project16, that was a good point
I ll have it burn in and finish the tests and do the final biasing next few days
Thanks everybody for all the help and support and sorry ggetzoff for hijacking your thread
.please see the attachments.
Attachments
I haven't finish the tests yet, the bias is almost stable now, just a little tweaking after the last two times I set it.
I did however left it burn for like 8 hours, BUT, the impatient guy I am I couldn't resist and connected it to my old mp3 player and my test speakers (2.5" peerless fullrange), my very first impression was WOW ! very very detailed well separated, sweet sweet sounding amp ! I was impressed even through my test setup, very beautifully balanced class A signature, can't wait to hear it now !
thanks Fab for such great amp and thanks again everybody for help and support.
I hope to finish testing in next few days and start listening to this monster
Edit: I measured the temp, all the lateral mosfets on both boards are in the same temperature range at around 120-125F, the heatsink is about 140F all around after an hour and half through second round of burning in.
I did however left it burn for like 8 hours, BUT, the impatient guy I am I couldn't resist and connected it to my old mp3 player and my test speakers (2.5" peerless fullrange), my very first impression was WOW !
very very detailed well separated, sweet sweet sounding amp ! I was impressed even through my test setup, very beautifully balanced class A signature, can't wait to hear it now ! thanks Fab for such great amp
and thanks again everybody for help and support.I hope to finish testing in next few days and start listening to this monster
Edit: I measured the temp, all the lateral mosfets on both boards are in the same temperature range at around 120-125F, the heatsink is about 140F all around after an hour and half through second round of burning in.
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The USSA-5 is an amazing amp. Listening to this recording for the first time the other day was spooky (no-pun intended, so close to Halloween, that fun, but hokey holiday we celebrate in the states) It's a binaural recording. The USSA-5 renders this recording properly, with a wonderful headphone-like presentation. It's absorbing, and draws you in, recreates the recording space in your room-it's ridiculous! It's kinda like you are in the middle of recording itself, with acoustical elements apparating then dissolving in the room like wraiths.
Give it a listen (even if you don't have this amp)
Cheers,
Greg
Give it a listen (even if you don't have this amp)
Cheers,
Greg
I haven't finish the tests yet, the bias is almost stable now, just a little tweaking after the last two times I set it.
I did however left it burn for like 8 hours, BUT, the impatient guy I am I couldn't resist and connected it to my old mp3 player and my test speakers (2.5" peerless fullrange), my very first impression was WOW !
thanks Fab for such great amp
I hope to finish testing in next few days and start listening to this monster
Edit: I measured the temp, all the lateral mosfets on both boards are in the same temperature range at around 120-125F, the heatsink is about 140F all around after an hour and half through second round of burning in.
Hi Aatto
You are welcome. Keep us posted on your testing in your main system.
I suppose you meant 140F for mosfet and 120F for Heatsinks...
What is your final bias? Have you measured the damping factor of amp?
Do not forget pictures of completed amp and including your PSU.
Fab
Things have started
As I promised Fab, my build has also started. I got some time Saturday to start soldering and managed to kick quite a few goals (see the photo). The soft start, speaker protection and power supplies are pretty much done and I am up to the stage with the amp modules that I need to supply some power to test things. I'll test the power supplies and soft start when I have some time and a fresh mind and then progress with the amplifiers.
One decision that I have made this morning is that I will make my own case rather than buy one. I've always done it this way and even though it is a little extra work I end up with just the look that I am after, which is black and not drawing attention to itself. It also means that I get to lay things out exactly as I wish because I am in control of every part of the design, apart from the heatsinks. This morning some big heatsinks were ordered. They are 350mm long x 151.5mm tall with fins 48mm long and have a temperature rise of 0.21C/w so hopefully I can get this amp running stable and relatively cool while pushing out its 25w or so.
Anthony
As I promised Fab, my build has also started. I got some time Saturday to start soldering and managed to kick quite a few goals (see the photo). The soft start, speaker protection and power supplies are pretty much done and I am up to the stage with the amp modules that I need to supply some power to test things. I'll test the power supplies and soft start when I have some time and a fresh mind and then progress with the amplifiers.
One decision that I have made this morning is that I will make my own case rather than buy one. I've always done it this way and even though it is a little extra work I end up with just the look that I am after, which is black and not drawing attention to itself. It also means that I get to lay things out exactly as I wish because I am in control of every part of the design, apart from the heatsinks. This morning some big heatsinks were ordered. They are 350mm long x 151.5mm tall with fins 48mm long and have a temperature rise of 0.21C/w so hopefully I can get this amp running stable and relatively cool while pushing out its 25w or so.
Anthony
Attachments
Anthony,
Looks like your build is coming along nicely - well done!
The heat-sinks are from Conrad in Australia or other source?
The toroidal transformers look like Toroidy units? How much was the shipping for those to your place?
Neurochrome audio speaker protection and soft start boards, Project16/Prasi power supply boards - looks like we shall have pretty similar looking amplifiers once completed.
My USSA 5 project is sadly still lacking the transformers and some power supply parts...
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Yeah, the 400VA Toroidy transformers were pretty expensive once they got to me, but it was a time issue for me as the guy I normally get to wind my transformers locally is very busy and would have delayed the project. I would have preferred some of his big EI power transformers (good mains filters) but the toroids should be ok.
Yes, the heatsinks are from Conrad Engineering. They are a very good company to deal with and are machining in some rebates on my heatsinks to make assembly of the chassis easier. Those rebates will save me a fair bit of mucking around when building the chassis which is all time that is rather scarce for me these days.
Yes also to Neurochrome ISS and speaker protection.
Yes, the heatsinks are from Conrad Engineering. They are a very good company to deal with and are machining in some rebates on my heatsinks to make assembly of the chassis easier. Those rebates will save me a fair bit of mucking around when building the chassis which is all time that is rather scarce for me these days.
Yes also to Neurochrome ISS and speaker protection.
Hello acg
The dimensions of your heatsinks are perfect, on my USSA-5 they are smaller in height and length of flats and I have no problem controlling the temperature and you can certainly allow you to adjust a BIAS higher but Fab will guide you when the time comes.
The Toroidy are really great transformer, I have two 2x19V - 250VA in my USSA-5 and they are extremely quiet and no heating is worth noting.
Good continuation.
The dimensions of your heatsinks are perfect, on my USSA-5 they are smaller in height and length of flats and I have no problem controlling the temperature and you can certainly allow you to adjust a BIAS higher but Fab will guide you when the time comes.
The Toroidy are really great transformer, I have two 2x19V - 250VA in my USSA-5 and they are extremely quiet and no heating is worth noting.
Good continuation.
Hi Fab.
Will do post more pics when I get it up and running
and yeah I post the temps the other way, after 8 hours running yesterday it did not exceed 130F, and the transformer was barely warm.
my final bias was 49mv with 0-1mv offset but hasn't measured anything after yesterday burn-in session same goes for DF, haven't finish testings and measuring
will post as soon as I have some numbers.Hi
Guys the United Chemicon 4700uF 35V (EGVD350ELL472MMP1H) is a must? I already purchased Nichicon FG 2200uF 35V type, Now to keep those in my box and order 4 more capacitors for $40.
If is not necessary I would love to avoid to spend on those.
Did someone built the amplifier using a different type of capacitor at C5, C6 place?
Thank you guys
Just to buy some fancy capacitors if not necessary living on ODSP support for way less than the minimum wage. If is a must I will buy it otherwise I would love to avoid the extra spending.
Guys the United Chemicon 4700uF 35V (EGVD350ELL472MMP1H) is a must? I already purchased Nichicon FG 2200uF 35V type, Now to keep those in my box and order 4 more capacitors for $40.
If is not necessary I would love to avoid to spend on those.
Did someone built the amplifier using a different type of capacitor at C5, C6 place?
Thank you guys
Just to buy some fancy capacitors if not necessary living on ODSP support for way less than the minimum wage. If is a must I will buy it otherwise I would love to avoid the extra spending.
Don't remember if I heard any binaural recorded music, just some effects and demo stuff, very interesting, should be a new experience through headphones.
Thanks.
Please?
It would be some kind of urgent if someone could answer my question, is there is any sonic advantage to use the United Chemicon 4700uF 35V (EGVD350ELL472MMP1H) for C5, C6 VS another type?
I need to order other items also like Nichicon FG 220uF for the other project etc. While I was waiting all last week to ask this question, Mouser sold out the mention capacitors found out today morning.
Now I went over to Di-Gi Key they have some limited quantity on the stock, I afraid if I wait a week or so they will run out from stock also, after other option min order 500PC.
So I feel like sitting on needles until I get answered so I can place mine order.
Wery likely Fab can answer this question or someone who made an A/B comparison of other types of capacitors at the mentioned place.
Thank you!
It would be some kind of urgent if someone could answer my question, is there is any sonic advantage to use the United Chemicon 4700uF 35V (EGVD350ELL472MMP1H) for C5, C6 VS another type?
I need to order other items also like Nichicon FG 220uF for the other project etc. While I was waiting all last week to ask this question, Mouser sold out the mention capacitors found out today morning.
Now I went over to Di-Gi Key they have some limited quantity on the stock, I afraid if I wait a week or so they will run out from stock also, after other option min order 500PC.
So I feel like sitting on needles until I get answered so I can place mine order.
Wery likely Fab can answer this question or someone who made an A/B comparison of other types of capacitors at the mentioned place.
Thank you!