Let’s Test A Heathkit Preamp • P6 How Good Can It Possibly Be?

In this final episode, I test all the preamp's functions, test its frequency response, harmonic distortion, signal to noise ratio and more. And I demonstrate it working in an audio system. This is a multipart series, where I build, fully-test and demonstrate a vintage, unbuilt, NOS preamplifier kit. In parts one through five, I discussed the history of Heathkit’s pro series components, unboxed the 40 year-old new-old-stock kit, built the circuit boards, removed the corrosion, painted the chassis parts and completed the build. If you missed those episodes, you may want to go back and check them out.
Also discussed: What's the difference between a moving magnet and moving coil cartridge? What is a loudness control and how should it be used? What is a control preamplifier or control amplifier?
#electronicsrepair #stereo #stereorepair #preamplifier

[@jblesser]

Such an impressive build done by a true professional. Really enjoyed watching your work flow. Thank you for providing these videos.

[@FluxCondenser]

Glad you enjoyed it!

[@bigfoot4000]

One of the most unique features of this preamp is the L-R feature which removes all of the common mode audio from the mix leaving only the audio that is NOT recorded in the center field of the mix. This is invaluable for separating instruments and more subtle elements of the recording by eliminating bass, kick drum, lead vorcals etc. allowing one to hear individual background vocals, instruments and stereo effects. The balance control can be used to hightlight different instruments based on their location in the stereo field. This out of phase content is what was used to simulate the rear channel content back in the days of quadraphonic.

[@FluxCondenser]

bigfoot4000 Thanks for that. Your description of the usefulness of L-R mode is far better than what’s described in the manual or my video. Indeed, the mode shifts the phase to cancel common info in the left and right, leaving only info that’s uncommon. I probably should have done additional tests of this feature to fully demonstrate what it does to the signals. Still, the result I showed was pretty interesting. As there was no common info between L+R (a different signal was applied to each channel), the result was both test signals appearing on both channels. I really hadn’t thought of using the L-R control the way you describe to isolate musical elements so will have to play with it a bit more with that in mind. Thanks for the excellent contribution.

[@bigfoot4000]

@@FluxCondenser If you inject the same signal into both channels and flip the switch to L-R, the audio will cancel out and totally disappear. What one hears when listening in L-R mode is what gets cancelled out when a stereo mix is summed mono (L+R mode). This out of phase content is the first to suffer attenuation when a stereo mix is rendered into compressed audio formats. Yet another reason why all of the music on my portable devices is never compressed. No mp3's for this boy! :)

[@FluxCondenser]

No that’s not quite right. Nothing is cancelled when switching to L+R mode. That’s simply a mono selector and both channels are summed. There is no phase shift, so there is no cancellation. And yes, as I said, the L-R shifts the phase to cancel common info in the left and right, leaving only what’s uncommon. By common, I’m not referring to negative, I simply mean sound that appears on both channels and is “common” to them. MP3s have their place, but yes, they absolutely do throw away information and the results can be horrible. There are better algorithms for compression.

[@JK-pv6tu]

Loved this series and thanks for making it. That amp is really special and would love to build something like that.

[@FluxCondenser]

Glad you enjoyed it!

[@curiosity2314]

Cool kit and an amazing video series.

[@FluxCondenser]

Thank you.

[@FAKECARL]

Beautiful amp... Great sounds

[@fabieneldridge3414]

HealthKits we’re always known for their great sound ! High quality kits !

[@fabieneldridge3414]

It really sounds Great ! 👍

[@FluxCondenser]

Thanks. Yeah it’s a decent amp, really.

[@larryhallas386]

Very nice video and nicely detailed. It brings back memories. I bought the preamp kit in 1982 as well as the AA-1600 amplifier. Built both at that time and still use them to this day. No issues to date. While using a turntable it is nice to listen to an all analog signal from start to finish. I remember at the time, that the AA-1600 amp at 125w per channel at less than .05% THD was hard to beat. Still wonder who actually designed the amp and pre amp.

[@FluxCondenser]

Thanks for the comment and sharing your experience with these Heathkits, Larry. Wonderful to hear that your builds are still giving you pleasure to this day. All my research points to these units being designed in-house by Heathkit. The Harmon stuff came later.

[@pjimmbojimmbo1990]

Really enjoyed your build, it brought back a lot of Memories of building my Heathkits. I see you are using Realistic MC-1000s, I used those with my AD-27a for over 4 yrs. Little 8 in Woofer and a Foam Surround Tweeter. I thought they were good Value for the Money, as I was in Grade 10 when I got them in Jan of 75. I got the AD-27a a couple of Moths later The preamp you built performed very nice

[@FluxCondenser]

Glad you enjoyed the build. I picked up those MC-1000s on ebay awhile back as they’re in nearly flawless condition and look as though they were never used. Nothing special, sound-wise, but not bad and as you say, a good value. Especially with the real wood veneer which is a nice touch. Take care and thanks for watching.

[@darthbubba866]

Wonderful series. Just wish I could find the earlier Heathkit vacuum tube preamps and amps as unbuilt kits.

[@FluxCondenser]

I hear ya, they’re hard to come by. Keep your eyes peeled, though, as I’ve had some luck finding unbuilt vacuum tube kits from Dynaco and Eico.

[@dalemettee1147]

Before I left high school, I built a Heathkit receiver for my dad and ordered a complete Hi-Fi system for him. Later, I ordered a Heathkit RtR tape recorder from them. The electronics was great, the mechanicals, not so much. A friend got the color TV. I liked the fact test operations were also installed so that you could align and test other operations.

[@FluxCondenser]

Thanks for the memories, Dale. I really like hearing memories of Heathkit gear. Too bad about the RTR being finicky mechanically. Was that a kit, too or pre-built?

[@dalemettee1147]

@@FluxCondenser It was a kit. I also got a Knight tube tester. Not a big one, like you see in the stores, but one that tested the tubes I needed.

[@Agamemnon2]

Ohh, I was wondering this whole series why this thing had speaker outputs as a preamplifier. Thanks for answering that :D

[@FluxCondenser]

My pleasure. Yes, often times preamps that are labeled as “control preamps” or something to the like have speaker control capabilities. They’re rare, but they’re out there.

[@FAKECARL]

Best sounding preamp

[@FluxCondenser]

Yeah, it really is an impressive component.

[@cdavidhord]

I really enjoyed your explanations of all the features of this vintage preamplifier. The testing was very informative. Great Job and thank you! What software were you using in the evaluation?

[@FluxCondenser]

Thanks, Dave. Love to hear comments like these. I’m using SpectraPlus software with a Spectra DAQ 2000 interface. Not cheap, but highly recommended. www.spectraplus.com

[@JD-lk7im]

Please can you made these videos with a stereo audio track.. It would then be perfect. Great build BTW.

[@anthonywebb3760]

Nice..

[@Truckguy1970]

Awesome build! Do you also work on cars and motorcycles? It seems like most electronic techs that I know also have mechanical abilities.

[@FluxCondenser]

Thanks, Truckguy1970. Glad you enjoyed it. I actually have little knowledge or experience working on cars, motorcycles or engines, but they do fascinate me. As you might imagine, my automotive experience leans more towards installing car stereos and even there I’m no expert. I am mechanical, though, and can fix many things around the house and I’m especially good with bike repair. Mostly out of necessity as cycling is a hobby of mine. Another passionate interest of mine is music and that’s largely driven my curiosity and desire to work on radios and stereos since I was a kid. Thanks for your interest and checking out the channel. Take care.

[@Truckguy1970]

@@FluxCondenser That's cool. I work on cars and a lot of other mechanical equipment and I also have a lot of experience with residential and industrial electrical wiring. I don't have much experience with electronics except for the basics because I don't have the instruments or tools to do electronic work but some day I hope to learn more. These days car stereos are a PITA to install because vehicles today have the Canbus system and you have to also purchase wiring adapters and modules to fool the ECM into thinking that the vehicle has the original stereo system still in it which usually has to be done with proprietary scan tools for each manufacturer. If you try to install a stereo in today's cars, the vehicle might not even start lol.

[@neverknowit11]

How can you hear the two test tones if your KZbin video is in mono? As you narrated one tone in left channel the other tone in the right channel.

[@geraldgerdes5675]

That’s quality from the 70-80 age

[@soundman2604]

I have one of these not in as good condition obviously. It’s souls is not as good as my NAD 1600. I wonder if mind needs to be escaped. Also now you need to find a matching amp AA1800. Mine sounds very good but I do have a few amps that sound a little better not by far.

[@FluxCondenser]

I didn’t use any of the electrolytics that came with the kit and there were a few supplied components that tested bad. Is your Heathkit equipment due for a checkup? Most assuredly.

[@sguttag]

What test software/hardware were you using, if I may ask?

[@FluxCondenser]

Sure thing. In this video I’m using SpectraPlus software with a Spectra DAQ 2000 interface. Not cheap, but highly recommended. www.spectraplus.com

[@sguttag]

@@FluxCondenser Thank you so much! I've thoroughly enjoyed this set of videos. In the rather distant past (1970s, mostly) I built a LOT of Heathkits...many of which are still with me . I appreciate your extreme attention to detail and craftsmanship in assembly that goes way beyond just slapping parts together. The results of that level of care and detail are evident in the final result. Very well done.

[@FluxCondenser]

Thanks, appreciate that!

[@gregsz1ful]

That cant be good to switch power amp AC power from preamp switch.

[@FluxCondenser]

Why not? As long as the amp’s power draw is within the outlet’s rating (total 1500 watts) it’s absolutely fine. For some larger amps, yes, they will go over that rating and should not be used. This is standard stuff.

[@gregsz1ful]

@@FluxCondenser should be a specified in manual.most amps will dim room light on turn on.

[@FluxCondenser]

What’s specified in the manual? As I stated, the preamp’s outlets are rated for 1500 watts total.