diyAB Amp The "Honey Badger" build thread - Page 441

stuartmp · 22nd November 2020, 04:00 AM

Quote:

Originally Posted by rephil

Hi stuartmp

Now the base of Q3 and Q4 are connected to Vcc

Best regards

rephil

Hopefully this is the last one.
Updated as noted

Dirttracker73 · 23rd November 2020, 01:56 AM

Thanks stuartmp for creating updated and easy to see schematic. Your note about cascode voltage reference shows the zener option using 15K at R19. I'm pretty sure I have 68K for R19 with zener D3 option. I don't see this in the build guide but it has been several years since I built it. Should I change R19 to 15K?

stuartmp · 23rd November 2020, 04:53 AM

Quote:

Originally Posted by Dirttracker73

Thanks stuartmp for creating updated and easy to see schematic. Your note about cascode voltage reference shows the zener option using 15K at R19. I'm pretty sure I have 68K for R19 with zener D3 option. I don't see this in the build guide but it has been several years since I built it. Should I change R19 to 15K?

A few people including myself experienced oscillation on start up.
This was found to be the current through the zener was not high enough.

You can do some more reading here.
AN008 - How to Use Zener Diodes
And
AN007 - High Power Zener Diode

Basically you need to have about 20% of the zeners current handling capacity going through it to get a stable output.
The 15k is based on 65v rails and may need to change depending on your supply rails. Search back for my posts and you'll find more info to.

Harry3 · 23rd November 2020, 06:24 AM

Easy to read - well done Stuart.

thompsontechs · 10:05 PM

If anyone needs MPSA18, let me know I just matched 100-pc of them for Hfe and Vbe

Hfe is in the 700-800 range, tell me what ou want and I'll ship ya some.

JT

thompsontechs · 23rd November 2020, 10:02 PM

Quote:

Originally Posted by stuartmp

A few people including myself experienced oscillation on start up.
This was found to be the current through the zener was not high enough.

You can do some more reading here.
AN008 - How to Use Zener Diodes
And
AN007 - High Power Zener Diode

Basically you need to have about 20% of the zeners current handling capacity going through it to get a stable output.
The 15k is based on 65v rails and may need to change depending on your supply rails. Search back for my posts and you'll find more info to.

Yes, nice job, it's easy to read and helpful.

Thanks!

JT

Dirttracker73 · 24th November 2020, 08:46 PM

Quote:

Originally Posted by stuartmp

A few people including myself experienced oscillation on start up.
This was found to be the current through the zener was not high enough.

You can do some more reading here.
AN008 - How to Use Zener Diodes
And
AN007 - High Power Zener Diode

Basically you need to have about 20% of the zeners current handling capacity going through it to get a stable output.
The 15k is based on 65v rails and may need to change depending on your supply rails. Search back for my posts and you'll find more info to.

Thanks for the info. I looked back to post 4132 and found the discussion. Will definitely look at what I have for D3 zener. Its been several years since building the HB and I've always had a tiny audible "hiss" with this amp. Back to the workbench, as soon as I finish one more thing....

AudioSan · 24th November 2020, 09:09 PM

I used 12V 0.5W zeners for +/-60Vdc rails. That worked great.

jerome86 · 30th November 2020, 07:59 PM

Hello Guys,

Do you you know where I can find resistors R40 -> R45? I can't find them on analogmetric.

Summitp · 30th November 2020, 08:50 PM

I used these for the 0.22R at r43-r48 (need 12 of em to fill both boards)
https://www.mouser.com/ProductDetail...r8JX1RDQ%3D%3D

and for the 2.2R at r37-r42 I used this (again, need 12 to fill both boards.)
https://www.mouser.com/ProductDetail...UyrvVwng%3D%3D

These have worked fine in my second HB build for months now with daily use.

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23rd November 2020, 01:56 AM	#4402
Dirttracker73 diyAudio Member Join Date: Jun 2010 Location: Rural, NY	Thanks stuartmp for creating updated and easy to see schematic. Your note about cascode voltage reference shows the zener option using 15K at R19. I'm pretty sure I have 68K for R19 with zener D3 option. I don't see this in the build guide but it has been several years since I built it. Should I change R19 to 15K?

23rd November 2020, 06:24 AM	#4404
Harry3 diyAudio Member Join Date: Mar 2005 Location: Sydney - Australia	Easy to read - well done Stuart.

24th November 2020, 09:09 PM	#4408
AudioSan diyAudio Member Join Date: Feb 2009	I used 12V 0.5W zeners for +/-60Vdc rails. That worked great.

30th November 2020, 07:59 PM	#4409
jerome86 diyAudio Member Join Date: Dec 2017	Hello Guys, Do you you know where I can find resistors R40 -> R45? I can't find them on analogmetric.

30th November 2020, 08:50 PM	#4410
Summitp diyAudio Member Join Date: Oct 2019 Location: Capital City of Salt, UT USA	I used these for the 0.22R at r43-r48 (need 12 of em to fill both boards) https://www.mouser.com/ProductDetail...r8JX1RDQ%3D%3D and for the 2.2R at r37-r42 I used this (again, need 12 to fill both boards.) https://www.mouser.com/ProductDetail...UyrvVwng%3D%3D These have worked fine in my second HB build for months now with daily use.