This is something I really like about these BA amps, and many people don't seem to exploit this feature. Can't put a shunt regulator on a Aleph J, F5, etc. front end....
The links from ZM's signature.
http://www.diyaudio.com/forums/pass-labs/119070-pumpkin-preamp-more-boring-making-thread.html
http://dl.dropboxusercontent.com/u/20665608/The Pumpkin & Shunty.pdf
The bias board takes its power from the output boards, you want the bias to modulate with the output PSU.
Thanks for those links. Shunty looks complex. Getting lazy. Just want to listen ASAP. Using Salas reg on one amp. Very good. Second Salas, not enough space in new amp.
With regard to bias board well if I run the front end from the main power supply that is connected to the bias board anyway so it will be drawing current from the same supply. Just happens that the way I have arranged things the bias board is right next to the front end, just a short wire away.
Chris
With regard to bias board well if I run the front end from the main power supply that is connected to the bias board anyway so it will be drawing current from the same supply. Just happens that the way I have arranged things the bias board is right next to the front end, just a short wire away.
Chris
Thanks Istmee. Is anyone running the bias board from a separate supply to the main power supply? Perhaps running the front end and the bias board together on a separate regulated supply. Didn't occur to me that one should. Is there any advantage?
On a different issue when passing mains cables through holes in a metal casing. Should all cables come and go through the same hole to prevent turning the chassis into a transformer core?
Chris
On a different issue when passing mains cables through holes in a metal casing. Should all cables come and go through the same hole to prevent turning the chassis into a transformer core?
Chris
When I said everything from one PSU, I meant front end, bias board and output; if your going to use two supplies, the bias board must be powered from the output stage supply.
Are you talking about multiple mains cables?
A single cable - the live and neutral leads must pass through the same hole.
If passing a cable in then out (as a loop through) to power other equipment (preamp?) then no, a separate hole is ok (as long as the live and neutral pass through the hole); earth is unimportant in this respect as there is no current flow.
Are you talking about multiple mains cables?
A single cable - the live and neutral leads must pass through the same hole.
If passing a cable in then out (as a loop through) to power other equipment (preamp?) then no, a separate hole is ok (as long as the live and neutral pass through the hole); earth is unimportant in this respect as there is no current flow.
ehh, not sure about it, but I don't think you can can seperate bias board from output stage that way
you should place it close to output stage anyway
Many thanks for all that and I have made adjustments accordingly.
I am putting two 200VA transformers into one box each with a 230V primary. I would like both primarys to be joined in parallel and to use the CL60 thermistor to delay the current inrush. Do I just use one in series between the mains input and one of the primary inputs?
Chris
I am putting two 200VA transformers into one box each with a 230V primary. I would like both primarys to be joined in parallel and to use the CL60 thermistor to delay the current inrush. Do I just use one in series between the mains input and one of the primary inputs?
Chris
take a look at F5 manual
power supply is show at the end of it
http://www.firstwatt.com/pdf/prod_f5_man.pdf
power supply is show at the end of it
http://www.firstwatt.com/pdf/prod_f5_man.pdf
Thanks tinitus but that is mostly the same diagram as for the BA-2 build. Nelson has shown two 120V primaries joined by the thermistor for a 240V supply ( I did this on the first build) but I have a single 230V winding. It seems logical to me to use a CL60 in series to this but I just want to be sure.
Chris
Chris
if you follow Nelson's curcuit with parallel primaries, there will be two thermistors, one on each winding
hey, I know no more than you, and what I see in the schematic
I have built several amps with a 500VA transformer and 400,000uF reservoir capacitance; one CL60 seems to be sufficient, I haven't blown a 3,15A mains fuse yet.
I thought the matter was settled, however, I have run out of CL-60 thermistors but I do have a mis-purchase left over from a previous order of several Honeywell ICL-15 devices.
They are rated at 5ohms at 25deg C and max current of 6amps.
Could I use one of these instead of the CL60 or even join two in series to match the 10ohm resistance of the CL60? How critical is the thermistor resistance?
They are rated at 5ohms at 25deg C and max current of 6amps.
Could I use one of these instead of the CL60 or even join two in series to match the 10ohm resistance of the CL60? How critical is the thermistor resistance?
The 10ohms of a CL60 matches well for transformers operating from 110/120Vac supplies.
For 220/240Vac supplies you get more appropriate values of current limiting using a pair of series connected CL60.
Four of your 5ohms would give adequate limiting for 300VA to 600VA, 240Vac transformers.
For 220/240Vac supplies you get more appropriate values of current limiting using a pair of series connected CL60.
Four of your 5ohms would give adequate limiting for 300VA to 600VA, 240Vac transformers.