Thank you! I had a huge collection of Robotix motors sitting around and this video has helped me with bringing them back to life. I would clean the battery packs thinking that was the issue, then I found your video. Liked and subscribed. Thank you so much!
@@Edgarbopp Call me anal, but I also despise inductor DCR also. I know in the end there are practical balances required, never mind limits, but I still hate heat waste!
Thank you so much for your videos about impedance! They are so helpful. Can you make something else related to impedance in the future? Maybe a DI box project to better match impedance of the guitar output and line input for those sound cards that don't have a Hi-Z instrument input, or a simple mic preamp to reduce impedance of a high impedance electret mic capsule or piezo element.
How are the batteries holding up? And what is your club car battery tray made out of (underneath your seat)? My club car only has metal bars down there but I’d love more of a floor to block water and such
Hello love the tube amp videos, so educational and easy to follow @ 19:31 I would speculate that the aparent lower power compression below 1k has to do with the distortion behaviour of the output transformer. Looking at the distortion plots there is increased distortion below 1k, I would argue the core is saturating and the aparent lack of compression measured is the rise in distortion where the core is active (<2k). I am by no means an expert and could likely be very wrong :)
It's not just variations in current drawn from the supply that cause reservoir cap voltage to vary. Here in South West England, my mains supply voltage varies a few percent with a regular pattern to it. It's like two or three simultaneous things varying the voltage, each having a different frequency in the range one to three Hz. If you concentrate you can see brightness fluctuations in an incandescent lamp, and also hear the same variations in the magnetostriction hum of a large transformer.
Having just watched the movie, this barely even resembles it. They completely cut Harry and Alex, the destruction of the Palomino, Kate's near-lobotomy, and removed any personality from the cast. Oh, and the scene with the meteor chasing the crew across the bridge was mirrored. I know they had very little run time on the record, but yikes! I grew up with this record, but wow, it's very very inaccurate. 😂 Edit: Thanks for uploading, I'm glad I could hear this again!
Good explanation of the different supply options. How does this final circuit differ from "capacitance multiplier? To my untrained eye it does not. I'll try the last one out. Is it necessary to filter it further with an inductor or can I pass it straight to plate?
The final circuit has a voltage reference created by a shunt regulator. In this case it’s a resistance and a Zener. That locks the MOSFET gate at a specific voltage. So it’s more like a regulator than a capacitance multiplier at that point. The output may feed the output tube plates directly. It will be very well filtered
@@Edgarbopp Thanks for explanation. Can I use high voltage NPN silicon transistor instead of a MOSFET? There are also 150v and 200v zeners available - how do I set the voltage for the transistor with it? I need like 250V in the output with up to 100 mA of current.
@@MarkErikEE a BJT can be used but the base will require current unlike a mosfet. To generate your reference voltage you will need to create a shunt regulator with a resistor and a Zener or a string of zeners. You will need to supply a minimum current to the Zener for it to drop its specified voltage. That should be in the data sheet. Chose the the resistance by understanding that the remaining input voltage that is not dropped by the zeners will be dropped by the resistance.
I keep coming back to this as it's one of the best explanations of this circuit in a practical application that I know of. However MOSFET pass device that R4 needs a better explanation. Am I right in R4 drops more than 6.4v then that's current limiting?
This is a series Voltage Regulator versus a Shunt Regulator, many prefer a voltage source feeding a Shunt Regulator for Audio Electronics as it is more stable to powers line fluctuations. A Shunt Regulator would have the Drain going to ground and the Source near the incoming voltage..
It’s just an inexpensive Hantek and works very well. The signal gen is also a cheap unit from AliExpress. Honestly anything decent will be ok, we’re just doing audio frequency work after all.
You make these "cheap" russian tubes work for hifi, fantastic! For negative bias Voltage I often use a small 1" by 1" print trafo 230V/9V and hook it up the the 6,3V ac heater winding (or to mains and use a voltage doubling bridge depending on -V needs). My local supplier has these small trafos for 0,95€ and they're light and small enough to be placed under the chassis.
Nice circuit! I especially like the power supply. Most people either use no MOSFETs at all or go crazy with super complicated transistor circuits. I just checked and the FQP10N60C is very affordable and available.These should also work as mosfet followers in the signal chain. Some ideas: No input transformer and use a 6N2P with higher gain for preamp tubes, Ra 120k with Va about 200V should give nice swing. And add the CCS tail could to your -22V supply. 6H8C only has a datasheet-µ of 21,5 , real life v/v of maybe 15.. Do you think this will work well with a 6N2P/12ATX or does the GU17 need the beefier driver with more current capability?
Hard to say until you give it a try. Those little input transformers are inexpensive and available on AliExpress though. In regards to the 10N60c I’ve actually just designed a A2 cascode output stage amp that uses one to drive the cathode of the output tube! When I get it finished up I’ll make a video about it. It’s 10wpc with a single el34 per channel SE.
@@Edgarbopp I might just do that - I have all tubes and parts on hand..Regarding the sand-assisted cathode drive, yes I have read about it on diyaudio. Looking forward to that video as I have experimented with a screen-grid driven 6P45S SE amp (I have nice unused op-iron for it) during covid but struggled to get the driver right and it sits unfinished
Love your educational videos especially this one and the load lines one! Very easy to follow and understand. Regarding transformers, output ones, I am looking at trying a 5k:5ohm LL1682 but my speakers are 8ohm, was wondering what problems would that cause like maybe bandwith issues. Need a good 10k:8ohm in my circuit but 8k would work. My output tubes are 6p1p in push pull A class. Thank you for posting all this great stuff and looking forward to new affordable tube discoveries and projects. PS: Russian 6H7C are very cheap preamp tubes with good linearity and paraleled are capable to drive interstage trafos, could be an affordable alternative to 6SN7 with a little less gain. They where intended for class B output stages. George.
if I wanted to calculate the output power that the amplifier provides before switching to class B, how can I do it? that is, I want to know the power only in class A. thanks
Good question! Because the output transformer is an inductor it has a reactance not a resistance. It supplies the voltage above supply. Inductors supply voltage to preserve current. They’re a type of current source.
@@Edgarbopp That's incredibile, so when the tube oscillates in class A, before the cut-off at the bottom, it always reaches that extra voltage? Thanks for these clarifications
I have 2 transformers that do not have markings or data sheet. Only a schematic of where it belongs. Do you mind if I email you some questions to help identify the pins of primary/secondary? Thank you.
Just wanted to say I enjoyed this video. I already have a OTL amp based on this tube (16 of them!). Hope you give some detail about the output tranformer. Not sure what EM label near mosfet signifies. Does it mean encasement mode?
Dude, do everyone (including yourself) a favor and write a script. Its really hard to watch and understand your videos with all the "uuhh" and "uuummm" in that monotone. The content is cool, the execution is rough.
