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Old 18th January 2013, 12:17 PM   #171
ncg2013 is offline ncg2013  United Kingdom
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Thanks Andrew, that’s cleared that up. Wires crossed!

But if I wanted to work out the power from a transformer is it something like this:

40 Vac x 1.414 = 56.56

V squared over R gives 800 watts! not right I think, where have I gone wrong?
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Old 18th January 2013, 04:20 PM   #172
ncg2013 is offline ncg2013  United Kingdom
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Default Choosing transistors...

Beginner question...
I am going through the BOM and ordering transistors on mouser and a few of the parts have more than one option. take Q5 it is specified as KSA992, but on mouser there are a few different types. Some with a suffix of FBU and some FTA and FBTA and FATA. The KSA992FTA has Gain Bandwidth Product of 100MHz, is that needed or do they all have this? They do look mostly the same!

A conclusive answer to this would be appreciated.
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Old 18th January 2013, 04:24 PM   #173
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Question:
For a Honey Badger monobloc with 3xMJL3281, 3XMJL1302, and a load of 2.6DCR, then what what is the maximum transformer (in amperes) that will safety throttle before the outputs could be harmed?

Specifically, I'm looking for the "maximized power" figure, such as 45+45vac in case of 8 ohm speakers, but need an answer in amperes to hold back the power in the case of 4 ohm speakers so that output device SOA cannot be exceeded. Assume worst case, music production use (digital organ, 32' stop, young caffeinated organist). How many amperes transformer is safe in these conditions?
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Last edited by danielwritesbac; 18th January 2013 at 04:28 PM.
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Old 18th January 2013, 05:01 PM   #174
tsip is offline tsip  Greece
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Quote:
Originally Posted by ncg2013 View Post
Beginner question...
I am going through the BOM and ordering transistors on mouser and a few of the parts have more than one option. take Q5 it is specified as KSA992, but on mouser there are a few different types. Some with a suffix of FBU and some FTA and FBTA and FATA. The KSA992FTA has Gain Bandwidth Product of 100MHz, is that needed or do they all have this? They do look mostly the same!

A conclusive answer to this would be appreciated.
Althoung i am not that more experienced than you, i think this project might be to complicated for you at the moment. I would suggest you leave this aside for a while, build something more simple like a gainclone and then take this up. This project has several pitfalls, i dont think that it is intended for a complete beginner and if something goes wrong, except from the components cost, it might put you off from the hobby altogether.
Just a friendly suggestion.
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Old 18th January 2013, 05:28 PM   #175
mattmcl is offline mattmcl  United States
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It is my understanding that the intention of this amp was to provide something a beginner could easily complete. As a beginner myself (though with a few projects under my belt) it has been confusing to match the BOM to Mouser parts. I believe someone is working on a BOM with Mouser part numbers, or in fact a parts kit to sell here. Either of these would solve the issue.

Personally I'm waiting for one of these two to happen before moving forward.
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Old 18th January 2013, 06:26 PM   #176
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Default throttle before the outputs :D

Dan -The fuses "throttle" the outputs.

TSIP - My first projects were an ampslab project and quasi's Nmos amp. I acknowledge this amp is a little more complicated , but it can be done by a beginner.

If this is built right up to the drivers(don't put the expensive outputs in yet) and Q14/15's emitters are tied to the output (L1) with 68R resistors (temporarily omit r36) , you will not blow anything -hopefully.

Adjust R30 (Vbias) for 1.2V between the emitters of Q14-15 and this amp is ready for the outputs. I use this for OEM repairs and all my builds (frugalamp , etc) ... only fried a couple of devices with probe slips and other stupid mistakes .


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Old 18th January 2013, 06:31 PM   #177
ncg2013 is offline ncg2013  United Kingdom
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Thanks for the suggestions but I will persevere. I have matched most parts already.
When I have the complete list I will post it up and maybe someone who has built one can add comments or suggestions.

BTW - not a complete beginner I made my own amps at the age of 14, 33 years ago. There has just been a 33 year gap. I am pretty sure there were not so many transistors then at my friendly electronics store... maplin.
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Old 18th January 2013, 06:32 PM   #178
ncg2013 is offline ncg2013  United Kingdom
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thanks for the encouragement OS!
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Old 18th January 2013, 06:41 PM   #179
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Quote:
Originally Posted by mattmcl View Post
It is my understanding that the intention of this amp was to provide something a beginner could easily complete. As a beginner myself (though with a few projects under my belt) it has been confusing to match the BOM to Mouser parts. I believe someone is working on a BOM with Mouser part numbers, or in fact a parts kit to sell here. Either of these would solve the issue.

Personally I'm waiting for one of these two to happen before moving forward.
In a few weeks I will order from mouser.
I could just make a saved BOM in the meantime w/mouser and submit that.
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Old 18th January 2013, 06:53 PM   #180
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Quote:
Originally Posted by ncg2013 View Post
Beginner question...
I am going through the BOM and ordering transistors on mouser and a few of the parts have more than one option. take Q5 it is specified as KSA992, but on mouser there are a few different types. Some with a suffix of FBU and some FTA and FBTA and FATA. The KSA992FTA has Gain Bandwidth Product of 100MHz, is that needed or do they all have this? They do look mostly the same!

A conclusive answer to this would be appreciated.
The FBU is ideal. I think they all have the same Ft (100mhz).
The Fxx is the gain (F=300-600 /P= 200)
The "BU /BT/AT" is the lead style. All would work (even the P Hfe).
"P" would just give a small decrease in loop gain (according to simulation).

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