JohnAudioTech

I decided to unlist my last video about the Douk Audio H7 Pro amplifier XLR signal level issues. Although I found it behaving as I'd expect, it is not following standards for audio signal levels and may lead to issues with sound levels when used with the XLR inputs. I still think it's a good budget product. Perhaps it would be better to use the space on the back for more RCA inputs rather than XLR. I question the need for XLR inputs on budget consumer gear. It is really not necessary, imho.

7 months ago | [YT] | 42

JohnAudioTech

Hi everyone. Apologies for not having any new content since June. My brother passed away after a long battle with cancer. He lasted 3-1/2 years after diagnosis of stage 4 lung cancer. He took a turn for the worse and passed yesterday evening.

With other projects demanding my time, my YouTube efforts suffer. I have ideas for new videos and projects to finalize, like the JAT801, but have to put these on hold for a while until things settle down. Sorry to be so brief.

1 year ago (edited) | [YT] | 177

JohnAudioTech

Speaker collaboration project

I've been thinking of designing a speaker. There's a lot of attention given to small bookshelf speakers these days if you check the reviews. Small speakers have issues. For one they have low sensitivity (measured sensitivity is often lower than what is published in the specs). If you want to play them louder, you need more power and that leads to another problem. If you ever cranked up the volume on a small speaker, you might have noticed that the bass becomes weaker and/or distorted. This is due to compression. The small cone area of these woofers are inadequate to move enough air and the extra power exceeds their limits. This is why it is common to pair them with a subwoofer.

I'd like to design a speaker that is somewhat larger (cab. volume around 1 cu ft or 28L) that can stand on its own (no sub needed) and sound good. No, it's not going to blow the roof off the house, but it will be something to sit down and enjoy the music to and not sound too compromised if you want to turn it up a little. It will match up well with chip amps like in the power range of the LM1875, or more power of the JAT501 amp.

I've been playing around in box modeling software with a few different drivers. I think we'd need an 8" woofer ported or a 10" if we go sealed. I'd rather go with a budget and build friendly design rather than something more exotic like a transmission line. I did find an 8" driver around $60 that gets a reasonable F3 in the 42Hz range and low group delay, all in a cabinet of 1 cu ft. As for the tweeter, I'd like to go with a dome type. I'd design for a reasonably flat response but may color it a bit to my tastes.

So, what about the collaboration? Well, someone with wood working skills and perhaps someone who can properly measure speakers could join in. We can sort it all out if there's enough interest. Comments?

1 year ago | [YT] | 110

JohnAudioTech

50K Subscribers & JAT501 project completion!

It took me long enough, but I've finally hit 50,000 subscribers. This channel will be 10 years old this summer. Big thanks to all the supporters / subscribers.

In the next video, I'll release of the gerber files and other documentation for the JAT501 audio amplifier project which marks its completion (It took me long enough on this too!). There will be more videos on the JAT501 in the future, but I consider the release of the files to be the completion of the project. Time to move on to something else. For one thing, I'd like to get a decent power supply designed for the amp. I'd plan to do a collaboration. I have a big list of videos I want to produce. No, I haven't forgot about "The Son of EZ amp". Stay Tuned!

2 years ago | [YT] | 198

JohnAudioTech

Exercise bike with car alternator
https://youtu.be/mbvIw1hIWWk
A friend dropped in for a visit and filmed me and my modified exercise bike that generates electricity. I originally constructed it in 1991 but use it as a part of my exercise routine since 2001. BTW, the magnetron you see in the video will generate microwaves at reduced power when hooked up to the bike. I can make another video of me powering up things if you want to see that.

3 years ago | [YT] | 17

JohnAudioTech

Snickers' final goodbye

I know some of you liked to see Snickers in my videos so it is only fair to let you know what is happening. I had to make a very hard decision this morning. Snickers has been in declining health. He lost his vision and much of his hearing. He has increasing trouble with his hind legs. Over the weekend, he's gotten worse and now he has stopped eating no matter what I try to give him. I had to make the grueling decision to have him euthanized today.

It was 15 years ago this month that I first met him. He started showing up at my parents house out in the country. After a couple weeks, and a bit of coaxing from my mom, I decided to take him home but not before my mom gave him his name "Snickers".

The photo is the first one I have ever taken of him. Before I decided to adopt him, I'd go walking in the woods and Snickers would follow me.


Farewell my friend. Death is absolute but I will always have the memories.

3 years ago | [YT] | 324

JohnAudioTech

The JAT501 amplifier project circuit description is posted on my Patreon page. It is available for everyone to see (don't need to be a member to see it).
Patreon www.patreon.com/user?u=12254451
Thanks everyone for the well wishes for Snickers!

3 years ago | [YT] | 71

JohnAudioTech

I will no longer have a PO Box after the end of May 2021. It is just too expensive to rent one around here. When I started 4 years ago, it was $41 for six months. The prices have been increasing almost every time I renew. Now they want $73. I don't get enough use out of it to make it worthwhile so it's gone. A big Thank You to everyone who sent something in to review or use on the bench. I'm a bit behind on videos I want to make and have an amplifier board that was sent in a few weeks ago yet to review.

3 years ago | [YT] | 79

JohnAudioTech

Hi Everyone! If you would like, join me in listening to the "Wax Carnival" radio show 8-11pm every Wednesday (Eastern US time). daytonoldies.org On the right side of the page under "How to listen", you can stream it. On the show they play "deep cuts" from albums, mainly from the late 60's through the 70's of various genres. WSWO-LP is a nonprofit low power (100 watt ERP) with volunteer DJs. They do various radio shows through the week. I like the Wax Carnival and listen to it while I work.

3 years ago | [YT] | 43

JohnAudioTech

Hi Everyone! Later today I will release my next video, an IC amplifier "done right". I have a lot of amplifier topics to cover in future videos as I get time to make them. Stay tuned!

I have a YouTube rant about the increased advertising. They went through my catalog of videos and stuffed them full of mid-roll ads. I said I wasn't going to have mid roll ads in videos less than 20 minutes but they forced it otherwise. In a 15 minute video, there are several ad breaks. THIS RUINS THE VIEWING EXPERIENCE!! Why in the heck would they do this? In my new videos, I will put one mid-roll ad. Hopefully they won't tamper with that. Having none may make them not promote my videos for ones with more ads. This is one reason why I'm leaning more on Patreon for support. Unless I make three videos a week and stuff them with ads, I will not earn enough revenue to make this worthwhile.

4 years ago | [YT] | 119