possible, but why do it?
we bias the VAS so that it has enough current to drive the output emitter follower stage...
small incremental changes are all that is needed..
I hope as well. Ha was not posted anything on the fb, about his journey, since middle of June. I tried to contact with him, but it was unsuccesful
Sajti
Three channel Honey Badger with DSP build
Hi all,
A first post to give a few details about my three channel honey badger build, and share a few experiences.
I've built a three channel asymmetric honey badger amplifier (actually the second of three I will complete) intended to drive a set of three-way active speakers which are yet to be built and will be documented separately.
The honey badger amplifiers are Rev 2.2 boards built roughly in accordance with the recommended specs and build guide. I've used three NJW0281/NJW0302 transistor pairs and a 15V zener reference. The output pairs were selected as representing the most well matched response curves and sufficient output capacity.
In the box I have placed two HB modules on one heatsink (in two parts) and one HB module on the other heatsink. As these are for active speakers I've designated the single module as reserved for driving the bass driver.
Additionally, I've used a few cheap off the shelf modules from connexelectronics - a pair of speaker delay and protection modules, three linear power supply modules, and a transformer soft start module with 12v output. I've used a 625VA transformer from element13 to power it all.
The last component is a MiniDSP module, providing an integrated filter and crossover. Case is from vt4c.com as it was about the cheapest I could get to Australia in a size I was happy with.
The first effort had some earthing issues and I've done significantly better in this second build. I'll strip the first and rewire a couple of components to improve the result as time allows (already a multi-year project).
I've built it in two layers, with an aluminium plate supporting the upper components.
Further details in later posts, and some of my lessons learned.
Hi all,
A first post to give a few details about my three channel honey badger build, and share a few experiences.
I've built a three channel asymmetric honey badger amplifier (actually the second of three I will complete) intended to drive a set of three-way active speakers which are yet to be built and will be documented separately.
The honey badger amplifiers are Rev 2.2 boards built roughly in accordance with the recommended specs and build guide. I've used three NJW0281/NJW0302 transistor pairs and a 15V zener reference. The output pairs were selected as representing the most well matched response curves and sufficient output capacity.
In the box I have placed two HB modules on one heatsink (in two parts) and one HB module on the other heatsink. As these are for active speakers I've designated the single module as reserved for driving the bass driver.
Additionally, I've used a few cheap off the shelf modules from connexelectronics - a pair of speaker delay and protection modules, three linear power supply modules, and a transformer soft start module with 12v output. I've used a 625VA transformer from element13 to power it all.
The last component is a MiniDSP module, providing an integrated filter and crossover. Case is from vt4c.com as it was about the cheapest I could get to Australia in a size I was happy with.
The first effort had some earthing issues and I've done significantly better in this second build. I'll strip the first and rewire a couple of components to improve the result as time allows (already a multi-year project).
I've built it in two layers, with an aluminium plate supporting the upper components.
Further details in later posts, and some of my lessons learned.
Attachments
Three channel Honey Badger with DSP build - Results
So reporting results of testing my Honey Badger amp. This is two of three channels connected, no load on the output channel being tested. Two channels should highlight any earth loops or other fundamental issues with my build or layout.
The attached samples were done using a PC running visual analyser 2014, using a spare probe set at 1x from my digital oscilloscope. The audio spectrum looks clean but there is evidence of HF noise from the miniDSP being passed into the amplifier on the oscilloscope. A simple filter cap across the amp input reduces the HF noise considerably. I used 100nF but this caused the frequency to roll off from about 1kHz so I'll need a smaller value which I'll determine later.
The tests were recorded with an output voltage from the amplifier of about 1.1V pp with a 1kHz sine wave as measured on the rigol oscilloscope (with some error for the noise mentioned above). This appears to be the peak un-distorted input level for my PC onboard soundcard. I've included my sound card noise floor for reference.
The summary is that the noise floor of the honey badger is significantly lower than the output of the miniDSP 2x4. After amplification, I get a noise floor of about -80 to -90 db relative to the 1.1V approximately 0db (measured as -0.88) level.
Peak drive level from a miniDSP is 0.9V RMS, or 2.55Vpp. With my gain stage, that's a peak output of +/- 35.0V, somewhat under the peak possible using the 35V secondary which should give me almost 50V peak.
Taking a conservative -75db noise floor figure, that gives a dynamic range of approximately 110dB or so if I have my figures correct. Quite acceptable for me.
I'm hoping to build active speakers approximately 90dB/W/m sensitive, with 8 and 6 ohm drivers. With the miniDSP it should give me a noise floor perhaps around 15dBA at 1m, or less at the listening position. I'd hear some hiss very close to the speaker but nothing in regular listening. I can hear the hiss on a cheap speaker from about 10-15cm in an office with a few fans in the background.
Peak system output of my current setup would be about 75W into 8 ohms. I could increase it by changing the system gain but I'll wait and see how this goes for now. I may need more power into the bass driver of my planned active speakers and the increase in noise floor should be acceptable for a bass driver.
Thus ends the stupidly technical part for now. Note that I haven't measured the honey badger amplifier module directly as I don't think my quick and nasty measurement setup would do it justice, and a quick look shows it's significantly cleaner than the DSP. If someone really cares then I may do some direct measurements with a better quality setup.
Perhaps more to follow on general build issues, if I get the enthusiasm
So reporting results of testing my Honey Badger amp. This is two of three channels connected, no load on the output channel being tested. Two channels should highlight any earth loops or other fundamental issues with my build or layout.
The attached samples were done using a PC running visual analyser 2014, using a spare probe set at 1x from my digital oscilloscope. The audio spectrum looks clean but there is evidence of HF noise from the miniDSP being passed into the amplifier on the oscilloscope. A simple filter cap across the amp input reduces the HF noise considerably. I used 100nF but this caused the frequency to roll off from about 1kHz so I'll need a smaller value which I'll determine later.
The tests were recorded with an output voltage from the amplifier of about 1.1V pp with a 1kHz sine wave as measured on the rigol oscilloscope (with some error for the noise mentioned above). This appears to be the peak un-distorted input level for my PC onboard soundcard. I've included my sound card noise floor for reference.
The summary is that the noise floor of the honey badger is significantly lower than the output of the miniDSP 2x4. After amplification, I get a noise floor of about -80 to -90 db relative to the 1.1V approximately 0db (measured as -0.88) level.
Peak drive level from a miniDSP is 0.9V RMS, or 2.55Vpp. With my gain stage, that's a peak output of +/- 35.0V, somewhat under the peak possible using the 35V secondary which should give me almost 50V peak.
Taking a conservative -75db noise floor figure, that gives a dynamic range of approximately 110dB or so if I have my figures correct. Quite acceptable for me.
I'm hoping to build active speakers approximately 90dB/W/m sensitive, with 8 and 6 ohm drivers. With the miniDSP it should give me a noise floor perhaps around 15dBA at 1m, or less at the listening position. I'd hear some hiss very close to the speaker but nothing in regular listening. I can hear the hiss on a cheap speaker from about 10-15cm in an office with a few fans in the background.
Peak system output of my current setup would be about 75W into 8 ohms. I could increase it by changing the system gain but I'll wait and see how this goes for now. I may need more power into the bass driver of my planned active speakers and the increase in noise floor should be acceptable for a bass driver.
Thus ends the stupidly technical part for now. Note that I haven't measured the honey badger amplifier module directly as I don't think my quick and nasty measurement setup would do it justice, and a quick look shows it's significantly cleaner than the DSP. If someone really cares then I may do some direct measurements with a better quality setup.
Perhaps more to follow on general build issues, if I get the enthusiasm
Attachments
Does anyone have an up to date BOM available or suggestions for alternative as several of the parts listed in the BOM are obsolete:
Q1/Q2 - ON SEMICONDUCTOR (VA) TRANS NPN 45V 0.2A TO-92
D1/D2 - NXP USA INC (VA) DIODE GEN PURP 100V 200MA ALF2
C3/C10/C12/C14/C16 - EPCOS INC CAP FILM 0.1UF 5% 100VDC RADIAL
I know little about the properties of these components and what would make a good substitution.
Apologies if this has been covered already in the thread, I couldn't find it.
Q1/Q2 - ON SEMICONDUCTOR (VA) TRANS NPN 45V 0.2A TO-92
D1/D2 - NXP USA INC (VA) DIODE GEN PURP 100V 200MA ALF2
C3/C10/C12/C14/C16 - EPCOS INC CAP FILM 0.1UF 5% 100VDC RADIAL
I know little about the properties of these components and what would make a good substitution.
Apologies if this has been covered already in the thread, I couldn't find it.
Finally finished!
After a alot of problems with soft starts from ebay and a broken screw in the heatsink my badger is finally done
I ended up creating my own soft start based on a micro controller (PIC16F1508) switching some some relays with NTC resistors. It's not the most advanced soft start but it works.
I'm now running the badger in dual mono on +/- 62VDC with 400VA transformers and a total of 240000uF. As you can see in the pictures the build is tight. Far tighter than I initially expected.
I may move to it to a bigger case in the future for easier bias and offset adjustments(very noobish of me to build it this way, I know).
The result is a very quiet amp that sounds fantastic! Feeding it directly from my Hegel HD12 dac the sound is very dynamic and full of details. It's a lot of fun to listen to
Only a slight hiss is audible with my ear ~25cm from my tweeters. I'm not bothered by this at all and honestly I think it could have been worse since everything is so tightly packed.
I want to say thank you to everyone that helped me and to OS for this wonderful design. I hope you are feeling better wherever you are
Some pics
After a alot of problems with soft starts from ebay and a broken screw in the heatsink my badger is finally done
I ended up creating my own soft start based on a micro controller (PIC16F1508) switching some some relays with NTC resistors. It's not the most advanced soft start but it works.
I'm now running the badger in dual mono on +/- 62VDC with 400VA transformers and a total of 240000uF. As you can see in the pictures the build is tight. Far tighter than I initially expected.
I may move to it to a bigger case in the future for easier bias and offset adjustments(very noobish of me to build it this way, I know).
The result is a very quiet amp that sounds fantastic! Feeding it directly from my Hegel HD12 dac the sound is very dynamic and full of details. It's a lot of fun to listen to
Only a slight hiss is audible with my ear ~25cm from my tweeters. I'm not bothered by this at all and honestly I think it could have been worse since everything is so tightly packed.
I want to say thank you to everyone that helped me and to OS for this wonderful design. I hope you are feeling better wherever you are
Some pics
Attachments
very good work... thank you for sharingAfter a alot of problems with soft starts from ebay and a broken screw in the heatsink my badger is finally done
I ended up creating my own soft start based on a micro controller (PIC16F1508) switching some some relays with NTC resistors. It's not the most advanced soft start but it works.
I'm now running the badger in dual mono on +/- 62VDC with 400VA transformers and a total of 240000uF. As you can see in the pictures the build is tight. Far tighter than I initially expected.
I may move to it to a bigger case in the future for easier bias and offset adjustments(very noobish of me to build it this way, I know).
The result is a very quiet amp that sounds fantastic! Feeding it directly from my Hegel HD12 dac the sound is very dynamic and full of details. It's a lot of fun to listen to
Only a slight hiss is audible with my ear ~25cm from my tweeters. I'm not bothered by this at all and honestly I think it could have been worse since everything is so tightly packed.
I want to say thank you to everyone that helped me and to OS for this wonderful design. I hope you are feeling better wherever you are
Some pics
After a alot of problems with soft starts from ebay and a broken screw in the heatsink my badger is finally done
I ended up creating my own soft start based on a micro controller (PIC16F1508) switching some some relays with NTC resistors. It's not the most advanced soft start but it works.
I'm now running the badger in dual mono on +/- 62VDC with 400VA transformers and a total of 240000uF. As you can see in the pictures the build is tight. Far tighter than I initially expected.
I may move to it to a bigger case in the future for easier bias and offset adjustments(very noobish of me to build it this way, I know).
The result is a very quiet amp that sounds fantastic! Feeding it directly from my Hegel HD12 dac the sound is very dynamic and full of details. It's a lot of fun to listen to
Only a slight hiss is audible with my ear ~25cm from my tweeters. I'm not bothered by this at all and honestly I think it could have been worse since everything is so tightly packed.
I want to say thank you to everyone that helped me and to OS for this wonderful design. I hope you are feeling better wherever you are
Some pics
Nice build Ejje.
I see you are using toroids from Poland. How do they perform? Are they quiet? How much did you pay for these? I'm asking as I was considering buying 800VA toroids from Toroidy-Poland but was not sure if they were good and quiet.
What caps are you using?
cheers,
I have used Toroidy power transformer a few times now. They were always good.
What speakers are you using? What brand and model is the tweeter? Does that hissing occur with other amplifiers?
Thanks guys
I'm glad you enjoyed the pictures.Thanks
As mbrennwa says, the toroidy transformers works very well. I bought mine with mounting plates which also comes with rubber to reduce vibrations to put between the trafos and mounting plates. Not sure how big of a difference they make but my setup is very quiet. I payed 657 zł for 2 audio grade trafos (2x45VAC secondaries) and mounting plates.Only thing that bothered me was that the primary voltage wires where quite thin (~0.5mm if I would guess). Works great but it would have felt more robust with thicker wires, maybe a 800VA model has thicker?
But I must disclaim, this is my first build
I have zero experience with other brands or kinds of transformers. I'm sure there is a lot of people here that are more capable answering transformer-related questions The caps are KEMET ALS70A203KF100
My speakers are DIY. They are called "LTS F1-2V".
It's an old 2-way design from a swedish speaker designer named Ingvar Öhman.
The tweeters are:
Seas H534
Yeah, it's always some very faint hissing from what I can remember. Never thought to much about it until I built my own amp
Knowing that Toroidy does not scimp on copper, then 0.5mm diameter equates to a Primary VA of ~ 140VA or a bit more.
Effective secondary would be ~133VA to maybe 150VA
That indicates quite a small transformer.
I have a pair of 600VA Toroidy and they have 1mm diameter solid core primary leadouts. They have a Primary VA of ~600VA if 3.3A/sqmm
1mm primary matches the rated VA.
The one thing I would appreciate are flexible stranded wire leadouts.
Maybe his current production are flexible, mine are quite old.
with most speakers and Power Amplifiers we do not hear hiss (noise).
A power amplifier rated to produce 100dB @ 1m when near but below clipping will have a noise output at least 100dB below that.
i.e. a S/N ratio of 100dB will give a 0dB spl at 1m. We cannot hear that at 1m. We might be able to hear it in a completely silent room if you stop breathing and you move in to 50mm listening distance.
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