Audio Note Kit 4 6v6 Tube Amplifier Clone with Heyboer output transformers and auto bias board

[@johnmenzies6865]

Great build.... will go to ure website fir all the details.

[@verderandy9161]

Hey Electrico, Very impressive build !! The chassis is gorgeous also, underside with a really neat layout. Good info on the auto-bias boards and their use. Thanks for sharing, Randy/GA

[@electricroo]

Thanks, I made another improvement. I swapped out the Edcore output transformers for better oned from Heyboer Transformers.

[@joes3485]

Nice design and construction! I have had a H-K A300 integrated amplifier since the early 1960s. It used 7408 tubes which are just low noise 6V6GT tubes. I have enjoyed it for many years and recently replaced all coupling caps and electrolytic sections with new internal individual caps inside the original cans. I had a set of 6V6GT tubes in the outputs, but did find a set of new 7408 tubes to install and did so. I don't really hear any difference in the sound of the 7408 tubes versus the 6V6GT tubes. The amp is rated at 15 watts per channel. I use it with some high efficiency speakers that I have modified myself. I also have a H-K A-500 integrated stereo amplifier which uses 7355 push pull output tubes and 25 watts per channel rated. However, I like the sound of the A-300 amplifier better! My best system is a Dynaco PAS-3X, ST-70 driving two sets of AR-2Ax speakers connected to the 4 ohm taps in parallel. 6V6 tubes have been around for a long time. They were introduced in the 1930s and many manufacturers used them in high quality radios and phonographs. You mentioned Magnavox, but also Capehart and various others used them including some with the 4-tube push-pull parallel circuit for more power out.

[@cobar5342]

Thank you for a great video

[@petersimmons1360]

I TOTALLY AGREE...the 6V6 is by far the BEST-SOUNDING audio tube ever made. ALL of the "EL" tubes don't even BEGIN to approach the beautiful-sounding 6V6!

[@bertroost1675]

It's smooth for sure but for my money I prefer the EL84, it has more sparkle on top. But for over all performance and cost the 6L6 is best. Most other tubes are too expensive. They certainly sound good but I prefer a nice sound with a nice cost. I think most amps made today use the more expensive tubes not because of the sound but because of some type of cooperation between tube manufacturers and amp makers.

[@eugenepohjola258]

Howdy. Very nice. One comment though. I would advocate using matched pairs. Technically only idle matching does not necessarily deliver the best fit. What we would like is to get the gain profiles to be mirror images, like positioning two overhead films on a projector for best resemblance. And this may happen at different idle currents. Gain profile matching is a cumbersome undertaking for DIYers, which is why I would recommend using matched pairs. I understand these are full profile matched by the manufacturer. Idle current matching should thus deliver profile matching too. Best regards.

[@electricroo]

I agree matched tubes are of a benefit in many cases. But using the auto bias board keeps the current in each push pull pair equal throughout the operation of the output stage eliminating the need for matched tubes. Especially as the tubes age. If it cannot keep the current stable it will shut down the offending tube. There are 4 led's on the board that show the operational status of each output tube. If the board shuts down a tube the indicator will go out. I have since extended the LED's to the top of the chassis as they are in my ST-70 clone. Those two amplifiers with the auto bias boards perform nice. Just another way to try something different to see the results!

[@eugenepohjola258]

Howdy again. Aha. Real time conductance matching. Very interesting. I didn't think of that. Regards again.

[@electricroo]

Menno Vanderveen came up with the circuit back in 2008 in conjunction with Tentlabs. The Tentlabs / Vanderveen bias supply is designed to bias (output) tubes, such that their operating point(s) remain stable, independent of tube age, mains voltage variations and music signals, without affecting the musical and technical qualities of the amplifier. Information here; mennovanderveen.nl/index.php/nl/producten/valve-electronics/supportive-electronics/valve-bias-supply-detail Look at the "Automatic valve bias module" manual and page. I'm using the upgraded version. The North American distributor for these is Erhard audio. A bit pricey but I wanted to try something different. I got mine from the EU distributor before I knew about Erhard. www.erhard-audio.com/AutoBias.html

[@eugenepohjola258]

@@electricroo And again howdy. OK. Fair enough. Thanks. And again Regards.

[@karenwasson8252]

I like to listen to your posts. Very informative.

[@tee-jaythestereo-bargainph2120]

Love the passion ! Thank you for the Video

[@SirLoinMagroin]

Hope those IC caps last.They have been prone to fail [prematurely] in many guitar amps. Be hard to see any leakage smooge as they seem hard on the board little or no air gap unless you remove and flip the board to see. Meter check I guess. Your work is very neat and professional. Would love to see a turret style hand wired 4-6V6 guitar amp with a deluxe circuit but more headroom with 2 more output tubes than the original.

[@electricroo]

Actually, I mounted and connected the PC board in a way that enables removal in case any of the power supply capacitors fail. Probably not in my life time though LOL!

[@simaolopes1797]

Fantástic job! I'm trying to build a kit four my self but i'm finding it very dificult to get a correct schematic. Could you please Share your tested and proven ones?

[@electricroo]

Here is a link to my K4 schematic. www.dropbox.com/s/a0lyjrphlh7thki/K4%20Schematic.jpg?dl=0

[@simaolopes1797]

@@electricroo Thanks a lot! Keep up the good work.

[@nmps28274]

Thank you for sharing, good stuff.

[@interesting7906]

Solid copy on that cap snake oil! No blind tests will ever be conducted as it would put people out of business. LOL

[@gnoter2]

Lol. You need a new set of ears or a new hobby! Snake oil my foot! 😴

[@interesting7906]

@@gnoter2 I would actually be very interested in someone coming up with a measurement that quantifies differences in electrical parameters of passive components. Then one would be able to sample the extremes and pick a personal preference. They have developed all kinds of distortion and speakers impulse response measurements that really describe the character of the amp or speaker. Yet, nobody will ever do that for passive components as there are enough gonzo like yourself out there that go by how much gold plating and how much it costs.