Have you tried removing C6 capacitor?
I found this fixed my huge oscillation issue.
I had an output to input oscillation via the power system coupled by C6.
Removing C6 fixed it.
As the transistors are configured as a common base configuration acting as a cascode, shouldn't one end of C6 be grounded and the other end to the zener diode's cathode in parallel? At least thats the schematic in the LT Spice simulation. The zener just gives a regulated voltage with the C6 in parallel for the common base system and i fail to see how C6 can cause input oscillation via the power system.
Without a Doubt C6 was causing my oscillation. I could trace it from the output, back through the power bias traces, and back into the power input of the front transistors. I tried putting a 0.1uf cap from power trace to earth, it made the oscillation earth out so bad it burnt out resistors on the board. I actually found the oscillation cause by increasing C6 capacitance thinking it may be zener noise. It made the oscillation larger. So i removed C6 and the oscillation stopped all together and i can now use the amp luckily. I dont think one end of the C6 is earth out on the board, its on either side of the zener to snub zener noise. Its not needed at all for a good running amp circuit. This is what i found in my amp. Multiple boards were the same, and i used exact parts list for the current honey badger and the latest diy audio boards. I tried everything else you can think of to fix the oscillation, only removing C6 fixed it.
Yes, C6 is on either side of the zenner, and one side of the zenner (the anode) is grounded, while the cathode is used to bias the common base stage. Please have a look at the diagram below. i am surprised that the C6 which is just used to smooth out the zener caused oscillations.
I have no doubt that what you say is correct that C6 fixed your problem, but I want to know why it was the case when it should not be.
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If you look at the schematic on diy audio, the zener and C6 supply the front differential pair transistors with power and neither side is connected to earth.
Both side are are power traces.
One side main power, other side power to front transistors.
I dont know if something else caused the oscillation, but the main coupling was done by C6.
Has anyone else had this problem or was it a random occurrence just for me. I used the exact parts recommended by the build guide and assembled accordingly.
Both side are are power traces.
One side main power, other side power to front transistors.
I dont know if something else caused the oscillation, but the main coupling was done by C6.
Has anyone else had this problem or was it a random occurrence just for me. I used the exact parts recommended by the build guide and assembled accordingly.
I quote from page 8 of the build guide itself "The first is a zener referenced design. Omit R18, replace it with a 12V -15V zener diode and set jumper pad "C" to "Z" with a jumper wire. You will have a cascode reference of either 12 or 15V, depending on your zener diode choice"
When you set Jumper "C to Z", you are shorting 'C' which is anode of the Zener to 'Z' which is a ground trace.
When you set Jumper "C to Z", you are shorting 'C' which is anode of the Zener to 'Z' which is a ground trace.
I'm sorry, you are correct.
The schematic on the site is wrong then and misleading, it shows the setup for the link C to R only where a resistor is used.
And nothing about the zener C to Z link.
I have no idea why C6 caused the oscillation, could it be a massive earth loop oscillation.
Something i hadn't thought about since i was mostly referring to the schematic which was different to my selection on the board.
The schematic on the site is wrong then and misleading, it shows the setup for the link C to R only where a resistor is used.
And nothing about the zener C to Z link.
I have no idea why C6 caused the oscillation, could it be a massive earth loop oscillation.
Something i hadn't thought about since i was mostly referring to the schematic which was different to my selection on the board.
If a zener is biased too low it can have negative resistance and oscillate into the capacitor. Cascodes sometimes oscillate themselves and so another possibility is that the zener was acting as a sort of base stopper.
If the oscillation changed depending on source impedance or whether the source was connected, then that would suggest you may need base stoppers.
If the oscillation changed depending on source impedance or whether the source was connected, then that would suggest you may need base stoppers.
Are you sure? I've never seen any negative resistance in zener diodes' characteristics.
Best regards!
Figure 5, page 19 here:
https://www.onsemi.com/pub/Collateral/HBD854-D.PDF
Also here:
Negative resistance in Zener diodes - ScienceDirect
EDIT: Looking closer at this article, I'm not sure they're measuring what they think they're measuring. I do know I've seen other references on negative resistance in zener diodes.
https://www.onsemi.com/pub/Collateral/HBD854-D.PDF
Also here:
Negative resistance in Zener diodes - ScienceDirect
EDIT: Looking closer at this article, I'm not sure they're measuring what they think they're measuring. I do know I've seen other references on negative resistance in zener diodes.
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I have a question about this amplifier versus the Pass F3 version 3. Has anyone heard both amplifiers? My Snells are power hungry with a minimum 80 watts according to the manufacturer. My question is how much of a difference is there between the two amplifiers as far as sonic quality? I prefer the sound of tubes myself and have almost always found solid state amps to be dry and lifeless. In fact the only solid state equipment I've actually liked were made by Audio Research and Krell both of which are out of my budget. So can any one tell me how this amp stacks up to the F5V3 or to a Krell?
The HB amplfier is very accurate with very low THD's, and noise that it is essentially transparent. It does not add any audible significant harmonics, nor does it take any away. It's very close to the holy grail of the proverbial wire with gain.
The fact that you like the sounds of tubes means that you like a amplifier which adds second harmonic distortion. Second harmonic distortion is perceived as "pleasant", "wide sound stage" etc. Therefore it is unlikely that you will like the HB2 or the F3 at initial listening tests . The F3 is also a transistor amplifier with low THD 0.05% at 1 watt, which does not have much second harmonic distortion as a tube amp.
The good news is that if you do listen to a neutral amp like that HB2 or F3, your neural and auditory circuits retrain themselves (this could take days to a couple of weeks) and THEN you will appreciate the crystaline highs and the purity which only a neutral amp can bring. Neutral amplifiers sound good, have a look at the reviews for the Benchmark AHB2 ampifier, it has immeasurable distortion and is the quitest amplifier on the planet and every golden ear reviewer loved its sound. I would therefore suggest you build the HB2, it has far lesser distortion than the F3, it is many times quiter and more accurate than Tube amps and therefore I am certain it wont disappoint.
The fact that you like the sounds of tubes means that you like a amplifier which adds second harmonic distortion. Second harmonic distortion is perceived as "pleasant", "wide sound stage" etc. Therefore it is unlikely that you will like the HB2 or the F3 at initial listening tests . The F3 is also a transistor amplifier with low THD 0.05% at 1 watt, which does not have much second harmonic distortion as a tube amp.
The good news is that if you do listen to a neutral amp like that HB2 or F3, your neural and auditory circuits retrain themselves (this could take days to a couple of weeks) and THEN you will appreciate the crystaline highs and the purity which only a neutral amp can bring. Neutral amplifiers sound good, have a look at the reviews for the Benchmark AHB2 ampifier, it has immeasurable distortion and is the quitest amplifier on the planet and every golden ear reviewer loved its sound. I would therefore suggest you build the HB2, it has far lesser distortion than the F3, it is many times quiter and more accurate than Tube amps and therefore I am certain it wont disappoint.
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is this schematic included power supply? meaning i just have to connect the v-in to transformator,is it correct?
Hello guys I dont want to read the entire post so I am asking following:
I guess this A/B class amp is a great match for a Magnepan speakers or?
What do I need to change to get 400W @ 4 ohms? (suggested power transformer, caps per rail, voltage?, suggested output BJTs?, biasing for the output devices? Sound signature preference is a little on the warmer side!
I have a tube pre amp that would do the job to add a little warmth but anyway!
I have a 5U 500mm Modu case so there is a lot of space and possibility for a higher current bias!
Thanks.
I guess this A/B class amp is a great match for a Magnepan speakers or?
What do I need to change to get 400W @ 4 ohms? (suggested power transformer, caps per rail, voltage?, suggested output BJTs?, biasing for the output devices? Sound signature preference is a little on the warmer side!
I have a tube pre amp that would do the job to add a little warmth but anyway!I have a 5U 500mm Modu case so there is a lot of space and possibility for a higher current bias!
Thanks.
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