Escaping the heat while recovering from a 200km bike ride yesterday and I got some audio work done.
I have a long way to go to reach the level of some of you, but I'm sort of getting the hang of this! 🙂
As usual, all schematics, layouts and code will be published on Github on the off chance that anyone cares.
Now I just need to build an enclosure.
- Assembled the first prototype of Bog on a Plate, a 200W plate amplifier based on my Bog Standard concept (which in turn is based on Blameless).
- Finished the breadboard prototype and code for my digital sub filter
- Added a mono low-level output to my main amplifier (also a Bog Standard, of course)
- Hooked it all up, Frankenstein-style and... it works!!!
I have a long way to go to reach the level of some of you, but I'm sort of getting the hang of this! 🙂
As usual, all schematics, layouts and code will be published on Github on the off chance that anyone cares.
Now I just need to build an enclosure.
It’s a grounding issue caused by crappy breadboard connections. I’ll get it sorted out once I’ve put the filter on a PCB. Without the filter it’s nice and flat.
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The voltage rate of BD139/BD140 is not enough for the VAS here.
Some other minor issues.
1. If you decide to include MOSFET protection, D4, D5, D6, D7 should be placed at the base of Q13, Q14. Usually, I run without these protection.
2. C8, C9 are kind of overkill. Usually, a pair of 100 Ohm base stopper resistors for Q13, Q14 could eliminate any parasitic oscillation from EF2. Although yours is a MOSFET output, they are similar. Try removing C8, C9.
Some other minor issues.
1. If you decide to include MOSFET protection, D4, D5, D6, D7 should be placed at the base of Q13, Q14. Usually, I run without these protection.
2. C8, C9 are kind of overkill. Usually, a pair of 100 Ohm base stopper resistors for Q13, Q14 could eliminate any parasitic oscillation from EF2. Although yours is a MOSFET output, they are similar. Try removing C8, C9.
Yup. BC139/140 are just a the limit (maybe a bit past it). I'll switch to TT(A/C)004 once they arrive from Mouser,
1. Why? I tortured this thoroughly in SPICE and it seemed to do the job. R22 and R23 will help starving the gates of voltage once the zeners start conducting.
2. Yes, I've been tempted to remove C8 and C9. It's probably time. 🙂
1. Why? I tortured this thoroughly in SPICE and it seemed to do the job. R22 and R23 will help starving the gates of voltage once the zeners start conducting.
2. Yes, I've been tempted to remove C8 and C9. It's probably time. 🙂
Output with a clean sine wave from function generator instead of my breadboard rat's nest.
My last unexpected oscillation from a MOSFET amp is about 50mVpp @30MHz. I really had to zoom in to catch it.
IRFP240 is pretty robust. It would blow up your power transformer before Vgs goes out of range. I don't bother to protect them. Parallel them is also overkill.
Overall, it is a nice amp. Do you have audio analyzer to verify the THD?
IRFP240 is pretty robust. It would blow up your power transformer before Vgs goes out of range. I don't bother to protect them. Parallel them is also overkill.
Overall, it is a nice amp. Do you have audio analyzer to verify the THD?
The QuantAsylum is on my wish list. I'm just finding it hard to justify $600 just to see how many orders of magnitude below audible my distortion is. 🙂
Thanks! It's really nothing special. Just my take on the classic Blameless. This is the fourth iteration and it's a darned solid design that's hard to make misbehave even if you try. Kudos Mr. Self!