Hi Jean !
I am also using bd139 on small heatsinks, they only get warm ?
Hi Echowars,
I do not use the 100k-pots, for biaspot i use 50k, and for dctrim
i use 10k with additional resistors. I like using smaller pots for
adjusting, this makes it easier to adjust as you have more movement
possible for exact adjusting.
Why insist on +/- 3mv ? I think, as long as it stays below 50mv
everything is fine...
The schematic shows mjl21196, but i used mjl21194...
I've built the doz only for evaluating, i wanted to know how it
sounds, to have some kind of reference.
I even don't use regulated supply, just a 0.5kw toroid with
2x22000uF. But it did not show any symptoms like humming, noise
or ticks from the powernet. I skipped fuses to avoid resistances
from PSU to output and used short cables.
My heatsink was too small, i had to add a small fan...
Mike
I am also using bd139 on small heatsinks, they only get warm ?
Hi Echowars,
I do not use the 100k-pots, for biaspot i use 50k, and for dctrim
i use 10k with additional resistors. I like using smaller pots for
adjusting, this makes it easier to adjust as you have more movement
possible for exact adjusting.
Why insist on +/- 3mv ? I think, as long as it stays below 50mv
everything is fine...
The schematic shows mjl21196, but i used mjl21194...
I've built the doz only for evaluating, i wanted to know how it
sounds, to have some kind of reference.
I even don't use regulated supply, just a 0.5kw toroid with
2x22000uF. But it did not show any symptoms like humming, noise
or ticks from the powernet. I skipped fuses to avoid resistances
from PSU to output and used short cables.
My heatsink was too small, i had to add a small fan...
Mike
An externally hosted image should be here but it was not working when we last tested it.
Here it is, one channel up and running. Next is chassis work and a bigger transformer . I am using mje15030s and they are getting HOT !
0 Noise, sounds very good
power supply board
As a DIY noob I need use pre printed boards. I am very interested in making the DoZ as simple class A amps seem a very good place to start- class A=good / simple=good for me!!
The power supply is the only thing I am struggling with. What board is your power supply. Sourcing parts is not a problem. Its designing or making circuits that I grind to a halt.
Any help very welcome
As a DIY noob I need use pre printed boards. I am very interested in making the DoZ as simple class A amps seem a very good place to start- class A=good / simple=good for me!!
The power supply is the only thing I am struggling with. What board is your power supply. Sourcing parts is not a problem. Its designing or making circuits that I grind to a halt.
Any help very welcome
To Jean
I'll second MikeB in adding heatsinks to the BD139. They get hot as hell (even with the small heatsinks but now they can at least radiate this energy). I use smaller heatsinks for the output transistors (MJ13003) and they get too warm too touch. However the chassis is taking up a lot of heat and can just be touched for a few seconds. I will post some actual temperatures soon but I would suggest that it must be somewhere between 70-80 degrees Celsius at max. That means a cool breeze for power transistors IMO.
For something slightly different I was just wondering if rewiring the ground from the input to a central groundstar would further decrease noise. In your picture it is twisted and soldered to the DOZ board. Let me know what you think.
I'll second MikeB in adding heatsinks to the BD139. They get hot as hell (even with the small heatsinks but now they can at least radiate this energy). I use smaller heatsinks for the output transistors (MJ13003) and they get too warm too touch. However the chassis is taking up a lot of heat and can just be touched for a few seconds. I will post some actual temperatures soon but I would suggest that it must be somewhere between 70-80 degrees Celsius at max. That means a cool breeze for power transistors IMO.
For something slightly different I was just wondering if rewiring the ground from the input to a central groundstar would further decrease noise. In your picture it is twisted and soldered to the DOZ board. Let me know what you think.
Looks good Jean
I'll add my 2 cents worth seeing I have just got my DoZ going.
I have bigger than recommended heatsinks on the driver BD139 and they do get quite warm though not hot. I have used the same heatsink as Jean (actually the ledge version he used in his P3A) for my output transistors (2N3773 TO3) although I have mounted both amps on the one heatsink. It gets hot, very hot but nothing self destructs even after 3 or 4 hours.
Hi JRKO
Get the DoZ PCBs from Rod Elliott. (P36)
The only comment I have for a first time builder is they get hot, and I found this a little scary the first time I turned it on.
As far as using the BrianGT PSU I would be tempted to add an RC network on the output as recommended by Rod to reduce noise.
I'll add my 2 cents worth seeing I have just got my DoZ going.
I have bigger than recommended heatsinks on the driver BD139 and they do get quite warm though not hot. I have used the same heatsink as Jean (actually the ledge version he used in his P3A) for my output transistors (2N3773 TO3) although I have mounted both amps on the one heatsink. It gets hot, very hot but nothing self destructs even after 3 or 4 hours.
Hi JRKO
Get the DoZ PCBs from Rod Elliott. (P36)
The only comment I have for a first time builder is they get hot,
and I found this a little scary the first time I turned it on.As far as using the BrianGT PSU I would be tempted to add an RC network on the output as recommended by Rod to reduce noise.
Thanks guys!
Since I am using the single rail version, one psu board is just perfect for two channels and grounds are seperate. There is no noise that I can hear when the RCA cable is connected, no hiss, no hum in the speakers.
Power supply diodes are only getting warm, nothing like the drivers on the amp board itself. Once I get the chassis done i'll see what difference there is by running rca ground to the psu instead of the board. I left this amp running for about 2 hours last night and so far so good.
Since I am using mje15030s for the drivers, I can't fit small heatsinks that I have on them...and I am not used to Class A amps just yet
Since I am using the single rail version, one psu board is just perfect for two channels and grounds are seperate. There is no noise that I can hear when the RCA cable is connected, no hiss, no hum in the speakers.
Power supply diodes are only getting warm, nothing like the drivers on the amp board itself. Once I get the chassis done i'll see what difference there is by running rca ground to the psu instead of the board. I left this amp running for about 2 hours last night and so far so good.
Since I am using mje15030s for the drivers, I can't fit small heatsinks that I have on them...and I am not used to Class A amps just yet
hi JRKO,
That heatsink JRKO is using looks like one of these:
http://www.conradheatsinks.com/products/flat100_350.html
I'd guess the MF30-75 rated at 0.37C/W.
That heatsink JRKO is using looks like one of these:
http://www.conradheatsinks.com/products/flat100_350.html
I'd guess the MF30-75 rated at 0.37C/W.
JRKO,
Sorry for not getting back to you earlier, been busy with work and my other hobby (autoX).
It's pretty simple, that psu board is basically like having two full rectifier bridges and a capacitor on each. Since DOZ only needs a + and - (one rail), you can just use one side of the PSU board per channel.
With one transformer, with dual secondaries, and one psu board you basically end up with a dual mono amplifier.
I blew one channel, so currently only one works and I'll probably use my heatsinks for another amplifier instead.
-Jean.
Sorry for not getting back to you earlier, been busy with work and my other hobby (autoX).
It's pretty simple, that psu board is basically like having two full rectifier bridges and a capacitor on each. Since DOZ only needs a + and - (one rail), you can just use one side of the PSU board per channel.
With one transformer, with dual secondaries, and one psu board you basically end up with a dual mono amplifier.
I blew one channel, so currently only one works and I'll probably use my heatsinks for another amplifier instead.
-Jean.
2N3055 PNP or NPN?
I am just ordering my 'bits' for this amp but am stumped by the difference between PNP or NPN for the 2N3055 transistors.
is it pos-neg-pos or neg-pos-neg or what?
Also as there are only two legs on these devices I assume that the case or body is the third contact.
Am I gonna kill myself with this amp?
I am just ordering my 'bits' for this amp but am stumped by the difference between PNP or NPN for the 2N3055 transistors.
is it pos-neg-pos or neg-pos-neg or what?
Also as there are only two legs on these devices I assume that the case or body is the third contact.
Am I gonna kill myself with this amp?
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