What are the values of R81-82-83 and 84?
Did you think about having the largest value always in the circuit and then shunting this with say a 2 pole dip switch?, this gives you 4 bias settings with only 2 switches.
Did you think about having the largest value always in the circuit and then shunting this with say a 2 pole dip switch?, this gives you 4 bias settings with only 2 switches.
Nice progress Borko.
How much off-board output capacitance are you using per channel?
Do you plan to bump up psu voltage to 45vdc?
I’m looking forward to your “stereo” listening impressions.
How much off-board output capacitance are you using per channel?
Do you plan to bump up psu voltage to 45vdc?
I’m looking forward to your “stereo” listening impressions.
Bogdan,
I was using 3/32" brass or plated eyelets. You can get them from Digi-Key (Keystone brand), as well as tools to seat them - it's a special punch that rolls the edges of the eyelet. The right eyelets are also available on Ebay. What you need to ascertain before you lay your money down is whether the eyelets in question are actually solid brass. I've been burned in the past by eyelets that were actually brass-colored aluminum, which of course won't solder worth a hoot...
I was using 3/32" brass or plated eyelets. You can get them from Digi-Key (Keystone brand), as well as tools to seat them - it's a special punch that rolls the edges of the eyelet. The right eyelets are also available on Ebay. What you need to ascertain before you lay your money down is whether the eyelets in question are actually solid brass. I've been burned in the past by eyelets that were actually brass-colored aluminum, which of course won't solder worth a hoot...
Thanks Wrenchone.
Vunce I still don`t know what power supply voltage I`ll use it depends of dissipation I`ll see when I make chassis and check thermal cap. Once, VR6 is set, it works on virtually any voltage.
Off board capacitance... diode bridge and 15mF/63V for power supply, nothing special.
Vunce I still don`t know what power supply voltage I`ll use it depends of dissipation I`ll see when I make chassis and check thermal cap. Once, VR6 is set, it works on virtually any voltage.
Off board capacitance... diode bridge and 15mF/63V for power supply, nothing special.
Ok, sounds good. Boards are ordered 😀
I have some trafo options to get me between 30-42vdc and have a pair of single rail capMx psu’s ready to go. I’ll start gathering parts in the meantime. Looking forward to this build.
I have some trafo options to get me between 30-42vdc and have a pair of single rail capMx psu’s ready to go. I’ll start gathering parts in the meantime. Looking forward to this build.
Nice SE Class A fun! I have all of these parts in my bins already. 🙂
I love the the DIP switch selectable settings in bias.
Nice schematic and layout, Prasi.
Nice SE Class A fun! I have all of these parts in my bins already. 🙂
I love the the DIP switch selectable settings in bias.
Nice schematic and layout, Prasi.
Max power version would be +45V DC and 1.4A bias, for 25W at 8 Ohms, like standard Fist Watt amps power range. That`s 63W dissipation per channel and about max. reliable power dissipation for these output devices.
Prasi made nicer PCB, with wider distance between output devices, and that is generally better, for spreading heat over heat sink.
I started collecting boards ready
20200708_163843.jpg - Google Drive
20200708_185907.jpg - Google Drive
20200708_193114.jpg - Google Drive
20200708_163843.jpg - Google Drive
20200708_185907.jpg - Google Drive
20200708_193114.jpg - Google Drive
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I put together a Mouser Project parts list for Bogdon Borko’s SE CFA Amplifier.
When you view it, please add it into your cart before editing it. The list will build one amp board, so double it for a stereo build.
I added a CoilCraft 0.5uH fixed inductor, the legs need to be bent to fit into the pcb. Or if you have the enameled wire eliminate it and wind your own.
Hi Borko,
Just wanted to double check the adjustable bias resistor values:
RB1 = 5K6
RB2 = 6K8
RB3 = 8K2
RB4 = 10K
HAPPY AMP BUILDING 😀
Mouser Electronics
When you view it, please add it into your cart before editing it. The list will build one amp board, so double it for a stereo build.
I added a CoilCraft 0.5uH fixed inductor, the legs need to be bent to fit into the pcb. Or if you have the enameled wire eliminate it and wind your own.
Hi Borko,
Just wanted to double check the adjustable bias resistor values:
RB1 = 5K6
RB2 = 6K8
RB3 = 8K2
RB4 = 10K
HAPPY AMP BUILDING 😀
Mouser Electronics
Hi Vunce,
i think the values are as follows
RB1-4 values :
0.5A 39K
0.8A 47K
1A 51K
1.2A 56K
1.5A 64K
1.8A 78K
Hi Prasi,
I have two sets of conflicting values, the figures you just posted and the ones that are in my post.
I will wait until Borko’s confirmation and edit the Mouser list as needed. 😉
I have two sets of conflicting values, the figures you just posted and the ones that are in my post.
I will wait until Borko’s confirmation and edit the Mouser list as needed. 😉
Hi Vunce, i referred Bogdan's bom posted in post # 89 and values posted by him here Single Ended cfa
The values posted by you seem to an order less.
Nice and comprehensive mouser project. I am sure it will be useful to many current and future builders.
regards
prasi
The values posted by you seem to an order less.
Nice and comprehensive mouser project. I am sure it will be useful to many current and future builders.
regards
prasi