Rhysh,
A slot for the fan protection is not necessary, however, incorporating a place to mount a relay on the psu board would be nice. We then could have several options for turn on/off, ie, remote low voltage, overheat overload protection, parallel soft start with thermistors which could be switched out by small timer.
Also adding pads for high quality rectifiers, instead of stock bridge units, would also be nice. There are numerous comments on this forum regarding the improvements good quality high speed rectifiers impart to the overall build. I do not believe stock full bridge rectifier blocks have these particular qualities.
If you use the LM317 as stated above for the power supply regulator would it have to be supplied a lower voltage source than what the LM3886 will be using. Would zeners in series work here? They can handle higher voltages. I think the LM317 is limited to 30+ volt supplies. Please correct me on this if I am wrong.
Tad
A slot for the fan protection is not necessary, however, incorporating a place to mount a relay on the psu board would be nice. We then could have several options for turn on/off, ie, remote low voltage, overheat overload protection, parallel soft start with thermistors which could be switched out by small timer.
Also adding pads for high quality rectifiers, instead of stock bridge units, would also be nice. There are numerous comments on this forum regarding the improvements good quality high speed rectifiers impart to the overall build. I do not believe stock full bridge rectifier blocks have these particular qualities.
If you use the LM317 as stated above for the power supply regulator would it have to be supplied a lower voltage source than what the LM3886 will be using. Would zeners in series work here? They can handle higher voltages. I think the LM317 is limited to 30+ volt supplies. Please correct me on this if I am wrong.
Tad
I was going to use pads for rectifiers yes, not whole bridges. A relay is also possible, but there is a point when it is worth keeping some parts off the board to keep costs down.
The LM317 would just be used for refrence for the power transistors, i belive the max input to be around 37V.
The LM317 would just be used for refrence for the power transistors, i belive the max input to be around 37V.
HaLo6 said:
As far as I know regulated supplies dont need a huge trafo, not as big as you would have on a non-regulated PSU.
The designer of the 'poweerreg' advises 120VA for a 2 channel LM3875. At a guess that's half the average VA rating most go for on non-regulated chip amp PSU's. Im thinking 250VA should do in terms of the BPA300 on a regualted supply. I could be totally wrong though....
Rhys?
Hi,
to get 300W (24.5V) into 4r0 during testing you need 30V and the average (rms) current delivered to the load.
For a 30V regulated supply you need approximately 28Vac to 30Vac transformer. This produces a DC voltage before rectifiers of ~40V.
The power supplied by the transformer during the 300W test will be 300 * 40/24.5 ~ 490W.
The transformer should be de-rated to ~70% when feeding a capacitor input filter.
The VA required for continuous 300W testing ~700VA. This is higher than a conventional unregulated PSU VA requirement due to the extra losses through the regulator.
For domestic music listening your 250 to 300VA recommendation will probably be adequate where average listening levels are -20dB ref max power i.e. 3W (3.5V average) delivered to the 4ohm speakers.
to get 300W (24.5V) into 4r0 during testing you need 30V and the average (rms) current delivered to the load.
For a 30V regulated supply you need approximately 28Vac to 30Vac transformer. This produces a DC voltage before rectifiers of ~40V.
The power supplied by the transformer during the 300W test will be 300 * 40/24.5 ~ 490W.
The transformer should be de-rated to ~70% when feeding a capacitor input filter.
The VA required for continuous 300W testing ~700VA. This is higher than a conventional unregulated PSU VA requirement due to the extra losses through the regulator.
For domestic music listening your 250 to 300VA recommendation will probably be adequate where average listening levels are -20dB ref max power i.e. 3W (3.5V average) delivered to the 4ohm speakers.
PCB received yet
Has anyone received a pcb yet? I have been waiting for a month after payment?
Have I missed something?
Has anyone received a pcb yet? I have been waiting for a month after payment?
Have I missed something?
There was a lead time with the pcbs as they had to be ordered from china, this is allways the case with group buys. The boards arrived here last week and started shipping straight away.
Kit Update
All the kits are ready to go, except C1. I have had to order these from a small hifi supplier who is waiting on the stock from the manufacturer. I have been told they should be with me on friday, so all the kits should be out on monday. I will send emails out RE shipping arrangments to confirm everything.
All the kits are ready to go, except C1. I have had to order these from a small hifi supplier who is waiting on the stock from the manufacturer. I have been told they should be with me on friday, so all the kits should be out on monday. I will send emails out RE shipping arrangments to confirm everything.
just for giggles what would be the lead time on the PS you are designing, I am interested but I'd rather pay for shipping twice if it will be a decent amount of time in between builds , this way I can get the amp laid out and then just drop in this awesome PS your planning.
Are you going to use the XAR with your BPA build?
I found a sweet case over at Par Metal for mine since I have those gigantic Conrad MF35-151.5 heatsinks I will be using for the sides.
Will there be enough thermal capacity if I slide the LM3886 all the way to one side of the heatsink and use the other half for your PS as i think someone stated it will release a healthy amount of heat too!
Are you going to use the XAR with your BPA build?
I found a sweet case over at Par Metal for mine since I have those gigantic Conrad MF35-151.5 heatsinks I will be using for the sides.
Will there be enough thermal capacity if I slide the LM3886 all the way to one side of the heatsink and use the other half for your PS as i think someone stated it will release a healthy amount of heat too!
Hi there,
It might be another month or so before i actually have the boards with me, as i am still not certain what exactly i want from this PS.
Yes, i will be using the XAR with the bpa300, thats what i was designing it for. Im going to get XAR boards ordered next week, but i will only have 5 or so and they will not be cheap becuase of the small quantity, around $20? The XAR is still no way near finished, but it will be by the end of this weekend.
Yes, it should be fine. Have you calculated your heatsink requirments for the 6 x LM3886?
It might be another month or so before i actually have the boards with me, as i am still not certain what exactly i want from this PS.
Yes, i will be using the XAR with the bpa300, thats what i was designing it for. Im going to get XAR boards ordered next week, but i will only have 5 or so and they will not be cheap becuase of the small quantity, around $20? The XAR is still no way near finished, but it will be by the end of this weekend.
Yes, it should be fine. Have you calculated your heatsink requirments for the 6 x LM3886?
It woould be great if someone smarter than me could calculate this for both 3 and 6 chips and then tell us simpletons approximateley what size Conrad heat sink is required for 3 chips and then for 6 chips.
kestrel200 said:
Im no good at heastink calculations either, i couldnt do one to save my life, nevermind for 6 chips in total!
I have two of them , one for each side of the amp. I know each one would be fine for the trio of 3886's, i was hoping that the heatsink could do double duty for the PS as well, which i think it should be able to do!
Kestrel200 and others,
Like Rhysh said Alexw88 used rather small heatsinks and enclosed them INSIDE the case. Of course Jeff Rowland used the entire milled out aluminum structure for there amps. Alex dreamed up with this scheme and seems to have had good luck with it. If you go to his website, shine7.com, you can get some idea of the size of the heatsinks. Also, search for bpa300 finished and measured on this forum. There are some great specs recorded by Alex on his amp, of which this is a clone. I believe that Rhysh's boards are a little bit heavier than Alex's original boards. (I think they are)
Rhysh, If you were willing I would prepay for a couple of the XAR boards when you order. I really like that layout.
You are going to email us when you have shipped the BPA boards.
Tad
;
Like Rhysh said Alexw88 used rather small heatsinks and enclosed them INSIDE the case. Of course Jeff Rowland used the entire milled out aluminum structure for there amps. Alex dreamed up with this scheme and seems to have had good luck with it. If you go to his website, shine7.com, you can get some idea of the size of the heatsinks. Also, search for bpa300 finished and measured on this forum. There are some great specs recorded by Alex on his amp, of which this is a clone. I believe that Rhysh's boards are a little bit heavier than Alex's original boards. (I think they are)
Rhysh, If you were willing I would prepay for a couple of the XAR boards when you order. I really like that layout.
You are going to email us when you have shipped the BPA boards.
Tad
;
Yes, i would be willing to do that. At the moment im working on adding input and output buffers to the PGA, and using DIP PGA's instead of SMD.
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