X, I have a question regarding the BB. I have my boards and supplies completed. Fired everything up, found a builder error, so no sound yet. I have repaired my error and before applying power again, I doubled checked to make sure the CPU cooler was not connected to the boards by the bolts.
In my checking I discovered both the V+ and V- tabs appear to be connected to the vias that are right above them. I am using an ohm meter to check. This is true of both boards I have constructed.
Is this normal?
Thanks
David
In my checking I discovered both the V+ and V- tabs appear to be connected to the vias that are right above them. I am using an ohm meter to check. This is true of both boards I have constructed.
Is this normal?
Thanks
David
Hugh, I found and corrected my build error. I powered one of the boards and was able to play some music through it, however at a very low level. I am guessing due to my construction error and powering the board I burnt out the two KSA992 transistors (V101 & V105)
Would I be correct in understanding the circuit that these two transistors supply the initial amplification?
Thanks
David
Would I be correct in understanding the circuit that these two transistors supply the initial amplification?
Thanks
David
Hi DrPro,
Sorry to hear your BB had some shorts due to vias. I think I mentioned that in the thread that CPU coolers needed insulating washers to prevent a short. I used felt washers. Always a good idea to check for shorts between a heatsink and rails with DMM before adding power. Was that your build error? If so, normally just blows fuses on the PSU. The amp normally survives that as current is shunted straight to ground - or from positive to negative rail and doesn’t flow through components.
Main thing to check: are you getting the usual 3A of bias current through the MOSFETs? Measure voltage across R145/6/7 - should have 3A and they will be warm. MOSFETs will be warm.
If weak sound, then maybe input connection is bad or reversed in polarity?
Next is check if you have about 2mA bias current through the LTP. Measure acrosss R104.
If both above are good, you should have sound.
Other possible thing to check is V111, sometimes that can get damaged or is wrong sex. Then you won’t have bias current and DC offset is huge(24V) in one direction but MOSFETs not hot.
Sorry to hear your BB had some shorts due to vias. I think I mentioned that in the thread that CPU coolers needed insulating washers to prevent a short. I used felt washers. Always a good idea to check for shorts between a heatsink and rails with DMM before adding power. Was that your build error? If so, normally just blows fuses on the PSU. The amp normally survives that as current is shunted straight to ground - or from positive to negative rail and doesn’t flow through components.
Main thing to check: are you getting the usual 3A of bias current through the MOSFETs? Measure voltage across R145/6/7 - should have 3A and they will be warm. MOSFETs will be warm.
If weak sound, then maybe input connection is bad or reversed in polarity?
Next is check if you have about 2mA bias current through the LTP. Measure acrosss R104.
If both above are good, you should have sound.
Other possible thing to check is V111, sometimes that can get damaged or is wrong sex. Then you won’t have bias current and DC offset is huge(24V) in one direction but MOSFETs not hot.
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Hello my name is Antonio. I live in the south of Spain, in Malaga. I'd like to do an alpha BB. Although Maty already warned me that produces a lot of heat and here where I live 15 degrees in winter and 30 or 32 in summer. That HP radiators with fan I recommend to cool as much as possible and not make a lot of noise. My level of English is bad, if you do not understand something of what I say is by the translator of Google.What radiator do I buy? To remove the maximum heat possible. A greeting
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Antonio,
Welcome to the ALPHA thread!
One of the minds behind the ALPHA BB, xrk971 uses the cooler described (with link) in this post:
https://www.diyaudio.com/forums/sol...id-aleph-alpha-amplifier-203.html#post5419258
Maybe X can chime in too.
Welcome to the ALPHA thread!
One of the minds behind the ALPHA BB, xrk971 uses the cooler described (with link) in this post:
https://www.diyaudio.com/forums/sol...id-aleph-alpha-amplifier-203.html#post5419258
Maybe X can chime in too.
Hello Alephotos,
Yes, the ALPHA20 and BB pcb’s are available here:
XRKaudio https://www.etsy.com/shop/XRKAudio
Hi,I'm trying to build a point-to-point test version before taking the PCB, I have almost all the components throw on the diagram there is C114 near C113, in BOM C113 is indicated 18pF or 22pF, but C114 not is in BOM and only the dielectric is written on the diagram, what capacity value should have C114?
Thank you