Boyuurange / Reisong A50 300B Tube Amp Advanced Mods Part Two

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In this multi part video, we complete one channel doing the advanced modification of this amp. This is rewiring the front end 6SN7 driver to a cascode design to drive the 300B correctly.
The tubing I use in the video is: 1mm ID 2mm OD PTFE Tubing
The next video we will test these modifications and report back how this mod sounds vs the original design. I have plan for further mods to increase the reliability and some cooling issues I see.
After what I learned from mods to my personal DIY 300B build, this A50 should turn out sweet! I'm going to use a LED/resistor combo for bias on the cascode + add gridstopper resistors etc.
Please subscribe to stay tuned!

Опубликовано:

11 сен 2024

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Комментарии : 20

@greghardy2676 2 года назад

This A50 video has been my favorite to date, so much good info and DETAIL...one of the BEST!

@frankfrank9711 3 месяца назад

Truly enjoy your wealth of knowledge. Keep the modifications coming 👍

@davidnguyen5028 8 месяцев назад

Pretty cool to see you’re showing your soldering work.

@user-uq3wt8dc8z Год назад

First, I'm genuinely impressed by your wealth of knowledge. I truly wish more people were as generous with their expertise. I come from an IT background, so some specifics fly over my head. Just a quick one - I've got this stock amp, and I'm considering replacing the original tubes to enhance its sound. Got a budget of around $1500. Suggestions? One of these days, I'll muster the courage to DIY this mod! Thank you!

@greghardy2676 2 года назад

Love ur tips and tricks...

@christiantudor-williams1184 Год назад

I've completed all the mods and have the Mundorf paper in oil and Audio Note caps on order. 2 questions. I've used a small red led for bias, where can i get one like you've used. Also, with cascode there is a lot less gain. Is there a way round increasing the gain. Great work BTW, love your channel and excellent explanation.

@SkunkieDesignsElectronics Год назад

Yes the gain is lower but before, the amp would go into clipping/distortion at less than 1/3 volume with normal sources. Yes, you will have to turn the knob more to get the same SPL, but the whole range is usable. You can get that LED at mouser HLMP-Q150

@brycejeannotte7699 2 года назад

I noticed that you changed the B+ resistors, now using 8.2K ohm units. Unless there was a problem with your camera, you had 100 ohm resistors in place before.

@SkunkieDesignsElectronics 2 года назад

Unfortunately some of the video was shot out of order, the schematic is correct.

@douwebakker3707 3 года назад

Hello, it seems to me better to connect the grid leak resistance just as close to the tube base than the stop resistance.

@SkunkieDesignsElectronics 3 года назад

Interesting, I've always heard that since the grid stopper is there to halt oscillations, it was the one that needs to be close to the pin. I do slip up a couple of times in the video and call the grid stopper "Grid leak" but I corrected it with a speech bubble. The grid stopper is the resistor in the signal path to create a low pass filter, the grid leak is there to reference the grid to ground for biasing. Hope this helps! www.aikenamps.com/index.php/grid-resistors-why-are-they-used

@douwebakker3707 3 года назад

@@SkunkieDesignsElectronics I generally mount the leakage resistor on the other side of the stop resistor

@danielemorgani7459 2 года назад

@@SkunkieDesignsElectronics in the final schematic posted on your website it shows the grid leak resistor tapped off the input before the grid stop resistor, in the video you wire it directly from the tube pin to ground, effectively putting it after the grid stop resistor? Is there a difference between your schematic and the way you actually wired it? Would it matter which comes first?

@SkunkieDesignsElectronics 2 года назад

@@danielemorgani7459 It really doesn't matter. The grid stopper is there to stop oscillations that might be in the input signal. You are not going to have any oscillation from the ground, where the grid leak resistor is located.