How well does the BC550C work for the input Q1 & Q2 vs the MPSA18? I bought some of the MPSA's on Ebay but not that many to choose from for matching whereas I have over 100 BC550C's to match from. From what I have found they seem to work fine but does anyone have any experience using the BC550C's? I understand about the pinout difference.
Hi Wdecho, the BC550C is a good choice. It is very comparable to the MPSA18.
On paper the MPSA18 looks a bit better, but I have heard that the ON Semi MPSA18 is not as good as the older Fairchild version (betas are lower). Therefore, what you can get in the market today is quite equivalent to the BC550C.
Looking at the datasheets, the pin-out is reversed in one transistor vs. the other. Not a huge deal. Look at the datasheets for details, it is on the first page.
On paper the MPSA18 looks a bit better, but I have heard that the ON Semi MPSA18 is not as good as the older Fairchild version (betas are lower). Therefore, what you can get in the market today is quite equivalent to the BC550C.
Looking at the datasheets, the pin-out is reversed in one transistor vs. the other. Not a huge deal. Look at the datasheets for details, it is on the first page.
Hi Sandro,
The only MPSA18's that are available that I know of not counting discontinued stock are the ones from Central Semiconductor Corp. The ones I bought from digikey had a beta of about 550.
I have roughly 1000 onSemi MPSA18RLRAG which I bought because I knew that they had higher beta then the Central Semiconductor Corp ones.
The onSemi ones have a beta of about 630. If anyone wants some send me a PM.
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I think the MPSA18 is better choice if you can get them.
I ordered 100 BC550C from Mouser and 100 MPSA18 from Tayda. Most of the BC550's have a gain of <500 and they vary from 440 up to ~580. The MPSA18's are 650~700 and much more consistent. I would take Stuart up on the offer if someone needs a few, less risk than eBay. I'm also willing to share what I have.
Tony mentioned jfet, any thoughts on using 2SK30 for the LTP? Tayda has a bunch of the Y (1.2~3ma) in stock.
I ordered 100 BC550C from Mouser and 100 MPSA18 from Tayda. Most of the BC550's have a gain of <500 and they vary from 440 up to ~580. The MPSA18's are 650~700 and much more consistent. I would take Stuart up on the offer if someone needs a few, less risk than eBay. I'm also willing to share what I have.
Tony mentioned jfet, any thoughts on using 2SK30 for the LTP? Tayda has a bunch of the Y (1.2~3ma) in stock.
I am at the point of deciding which VAS compensation to use. I am undecided whether to go with the Conventional Miller Compensation CMC or the Transitional Miller Compensation TMC. I have read the build guide many times but would like some input from other builders. I am sure the answer of most favorite is in this thread but this thread is really big and it would take hours of reading to get an idea of which is favored.
Hi to all,
I have some questions about the honey badger.
1 : Will it fit in a modushop 3u 30cm cabinet? I have these.
2 : is there a need for matched transistors?
3 : when i order the power transformers at toroidy what is the one to take? 2 for dubble mono? Voltage ?
Best regards and sorry for the bad englisch.
I have some questions about the honey badger.
1 : Will it fit in a modushop 3u 30cm cabinet? I have these.
2 : is there a need for matched transistors?
3 : when i order the power transformers at toroidy what is the one to take? 2 for dubble mono? Voltage ?
Best regards and sorry for the bad englisch.
Short Answer, TMC is better as it gives you more local loop negitive feedback at low frequencies which increases stability. It also reduces distortion by putting more local feedback around the output stage instead of by just increasing global negitive feedback. At high frequencies it has the same stability and amount of global negitive feedback as CMC.
1: The HB board is 254x76mm, a TO-264 output transistor will need ~36mm more height, so it seems like it should fit but it will be snug.
I'll let others chime in on 2 & 3.
No worries on the english - just fine.
It not really about that it's about the size of the heatsink that you need to provide the right amount of heat dissipation.
Then make a case that will fit that and everything else.
My case is 430mm wide x 375 deep x 180 deep and as you can see it quite tight.
Conrad Heatsinks - Products
Then make a case that will fit that and everything else.
My case is 430mm wide x 375 deep x 180 deep and as you can see it quite tight.
Conrad Heatsinks - Products
Hi , thx for the answers.
The format of the pcb will fit but the heatsinks are to small form the job?
Yes, Even the heatsink that I have chosen is not sufficient to run this amplifier continuously at full power using supply rails of 64v DC.
Your choices are use a larger case so you can fit the heatsink that I show or reduce your supply voltage.
But be sure to caculate the heatsink that you need base on your expected output power.
3U300mm chassis will do the job just fine. I got 5 ch with 4U300mm sinks from modushop in one and the same chassis (inside the chassis) and have no problem with heat.
The differnce between 3U and 4U is minimal. If you dobble the hight (length of the sinks) you gain only 25% cooling capasity.
The differnce between 3U and 4U is minimal. If you dobble the hight (length of the sinks) you gain only 25% cooling capasity.
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Confusion on my part about the D BC option diode on the board. Is it necessary or like it says on the board an option? I have found nothing in the build guide or BOM about this diode. I have found some info in this thread but it is still confusing to me. I have ordered some obsolete BV20 diodes on Ebay.
