807 Stereo SET "Little Jewel" Amplifier

Description of amplifier, voltage readings, square wave testing and differenced in output power and THD with vacuum tube rectifier and solid state rectifier.
Below are unlisted links to individual sections of the video.
• Stereo 807 SET "Little... - power and THD differences with vacuum rectifier vs solid state rectifier.
• Stereo 807 SET "Little... - Square wave testing.
• Stereo 807 SET "Little... - Voltage measurements.
• Stereo 807 SET "Little... - Overview of amplifier

[@drdyna]

I kinda like the tung sol 6sn7s also, I use them in the cathode follower spots in my freya, using older sylvanias in the gain spots. Great tubes! Can't say the same for the tung sol kt120s though.

[@tedcollins4684]

Thank you for all you do sharing the entertaining and educational videos.

[@ElPasoTubeAmps]

I can not explain that low harmonic profile at about 16:00. I must have had a lose connection. It seems to have gotten normal at about 17:20.

[@diabolicalartificer]

Nice workmanship, grand layout. I like the simplicity of this amp. Re the bias of 6SN7 @ 0.5v, I would have thought that's a bit low, 1 - 2v being more normal to prevent grid current, though it depends on the sensitivity. I was very surprised at how low the HT/B+ ripple was, it's normal to read something like a few mV or less if poss. Also why did the 8H have sort of a sideband, noticed it too on lower harmonics; an artifact of the SA? Lastly I'd be interested in how much crosstalk you have, what the waveform looks like at 20hz & the frequency response in general + THD at other frequency's. Thanks again for posting & sharing your work.

[@kgsalvage6306]

Glad you built yourself an SE amp. I knew if you had a good one, you would enjoy the sound. All you need to do now is connect it to ARTA or TrueRTA. I finally got my setup all finished. The free version of TrueRTA doesn't let you get the full resolution unless you get the membership. I probably will, but also was still able to download ARTA. The free version of it works much better. The Tascam probably works about the same as your Fosrite. The noise floor is about -140db. THD on the unit is 0.003%. Might have to build an 807. I went through my stash and have quite a few. I have some nice 5692 red base I could use in it. I'll wind my own transformers for it. Excited to do that. I need to order some cores and laminations. Be Safe! Talk to you next time.

[@dennisgouveadeazevedo6238]

Thanks for another great video. I’ve been doing nothing but SE amps for the last 10 years too. If you like the way it sounds now, you should definitely try Ultra Linear Single ended with el34’s you’ll be amazed. You can get 6w rms per ch below 1% THD and, if the output transformer is right , you can get that from 18-20.000Hz. And all of that using a single tube in the front end (usually a 12at7 or a 6sl7). For those figures, you’ll need beefier capacitors and a pair of silicon diodes instead of the 5u4G. Thanks again for taking the time to share your videos with us. I learned a lot from your videos.

[@bennoheritt8154]

Thanks for another great video

[@WECB640]

One of the tricks we use in FM broadcast, is to add a sprinkling of EVEN harmonics to the top end of the audio. This is done when our target audience is predominantly female only. Females hear differently than most males, in that they often prefer a bit of additional even harmonic energy as they find it quite pleasing and "sweetening" to the shimmer of the sound. It's subliminal, sort of like the delicate difference between chicken and duck where duck has a richer taste. Odd harmonics are generally perceived by both males and females as objectionable and slightly irritating. Males are a different animal altogether. They often couldn't care less with the top end of the spectrum or any added even harmonic energy there. What they do enjoy is a hard hitting sub bass that often extends into the infrasonic area. This VLF can also be limited quite hard with no ill effect. The average male will put up with a slight bit of clipping whereas the female will find any clipping to be objectionable. I share this here because of the tube swap and how each sounds slightly different. The measurement of harmonic energy is SPOT ON and a wonderful example. I think if you were to play each tube to a male and then again to a female, you might find that each prefers the opposite tube because their hearing and processing of what they hear is often quite different. Now if we could find a tube that attenuates the odd harmonics, we just might have a holy grail. Keep up the excellent work! 73 OM

[@lambrosratchis3062]

I love what you doing I would like to build one what transformers do you use so I can order the same ones thanks

[@brianmoss5483]

I have a we 422 rectifier and can hear a difference.

[@jimholloway9949]

Oh boy...I'd love to build one of these! I think I have some transformers on hand that would work. Where can I find the schematic?

[@paulpaulzadeh6172]

7:e harmonics looks strange, it seems it has dubbel there , why is that ?

[@railgap]

I just took a ham to task for having no pride in his workmanship, an embarrassing chassis, lousy (no) wire dressing, etc. I could (should) just show him your work, as an example of what to aspire to. Buuut, what's up with those aluminum electrolytics on the tube bases? Referring to the schizmotic, at least one of them appears to be within the signal path. Surely not? I must be misreading something.

[@Steven-pv1xr]

You do nice work KA5WZY. Yes. Yes. About 4 to 8 db is great. I usually use 6db of neg feedback. I agree with you. Also a little capacitance across FB resistor to limit any rf that gets in there. You are on track