I took the advice from your videos and bought the EH 7025 right off he bat. After I painted the unit, I installed cheap coax style interconnect cable. Shielded, but not ideal. I will look for that cable you get from guitar stores. I have some but it is too big and hard to work with. The caps on the amplifier board were blown on one channel, and I replaced all on that channel and the two low voltage caps just for good measure. I checked them with my capacitance meter, they were a few pf, instead of 22uf. Do you think I might need to replace any other caps? Good to know about the 14 awg. I have 18 in there now. At normal listening levels there is no hum now.. I am thinking of printing up a insulator washer like the rca jacks use for the input gnd stud . Isolate that so it's single point gnd, without multiple paths through chassis. One day...no rush, as I am pleased. The problems were good learning experience. Made me feel good to figure it out, even if it was to figure out my own mistakes like the reverse polarity on the audio signal. That made serious hum. I have already moved on to the next project in my head. Trying to down select to what type of amplifier to build. Thinking El34 or KT88, like one of the designs from the GEC or Mullard application notes. But also thinking I should make a smaller less expensive one for my first amp.

I had a lot of hum. First problem was I had polarity swapped on the inputs to the preamp board. That makes a very , loud hum. If you touch the phono ground or the metal on the rca jack and the hum changes, then this is probably the biggest source of your hum. I then had some residual hum. Looking at the pictures and diagrams on the lenco heaven website, I noticed they payed very close attention to single point grounding techniques. I do not see a chassis gnd wire from the power supply to the chassis, but maybe it is on the other side. This knocked down the hum in my unit to where I can only hear it at very loud volumes with no music...barely there. A diagram is here from Jessica k. https://www.lencoheaven.net/forum/index.php?topic=20984.180 https://i.imgur.com/fzYCgJx.png Jay has a better diagram later on. He also shows a transformer for MC, but shows the phone input chassis gnd. Ignore the SUT part. https://www.lencoheaven.net/forum/index.php?topic=20984.345 https://i.imgur.com/q7lEod8.jpg I suspect if you have your audio signal polarities correct, and follow the gnding in the diagram above, that the hum will go away, it did at least for me.

Here are some updated photos. The hum in my unit went away by correcting the grounding. I think I still have more to cleanup, as I have a ground loop between my phone input gnd to chassis and the input board, and the gnd on the ps broard. I did not have the single point gnd position on the power supply board connected to chassis. There are lots,of good diagrams on the lenco heaven website about how to do the grounding correctly. Regardless, hooking up the power supply board from the gnd with a triangle point on the board to chassis made the the hum go away except at very high volume. I was hearing the sound of the needle dragging on the record. I think from the bad ground it was generating static as my records were suddenly sticking to the mat on the platter. I made some mistakes reassembling the unit. I hooked up the b+ backwards on one side of the board. I guess it was good at that point I did not have the ps gnd connected to chassis. Eitherway it made let the smoke out of the 22uF caps. So I replaced all the caps on that side. I always order a few extra, and just happened to have the 3 40pv caps as spares. I then had a weird, ridiculous strong hum on one channel. Just touching the rec jack would cause the hum to change. The other channel was fine. Turned out I had the polarity swapped on that channel where the input connects to the board. Swapped the polarity and the hum was back to lower"3vels of the prototype stage. Again, that was later cleared up by connecting the power supply board gnd point to chassis. I think I need to isolate my phone input ground from chassis, and take it back to the single point ground on the power supply board. But even with the ground loop through the chassis, it it pretty quiet. I guess I will not bother with the metal bulkhead. The holes were not centered around my tubes. So I elongated them with the hole punch. The curtain rod rivets have a large enough lip to cover the gaps and make it look perfect. Thanks for that great idea in your videos. The mids still sound a little harsh and have like a static to them. But my HIVI speakers seem to have that quiality, so I need to do more listening to more records and hook up my other speakers. I will probably continue playing with this seeking diminishing improvements. But I suspect my next improvement should be upgrading my cartridge on my $299 Audio Technia turntable. Always love the rustoleum "hammered" paints for finishing electronics project boxes. It was a cold 50 deg day, so I used multiple layers of quick dry filling primer, and then put one coat of the rustoleum hammered black paint, and then put it on my propane grill with only one burner on low, and baked the paint on at 150 to 200 degrees for a couple of hours. I would have been waiting a week or two in this weather for the paint to harden up and not scratch off during assembly. It is a great trick, just do it outside, and make sure the temp is low and stable so it does not catch fire and ruin the chassis, and away from your house in case it does catch fire. But inside a metal closed grill, it should be fine. I did this in the house oven once,, the resulting fumes are not recommended. Hence the propane grill outdoors. Bondo auto body filler fixes accidental holes and the dimples and gaps on the ends from the spot welder.

I just listened to blood sweat and tears, spinning wheel, and they sounded really good. I am not a very good objective listener.

I wanted to add auto sound reading material. I have some in storage, need to get it and install. The note I listen to these the more I find I am wanting something more from them. Teeeter sounds very good. The mids occasionally sound harsh to my ears. I have a very challenging room for bass. So not sure it is the speakers or my room with regards to bass. I asked the vendor's support desk about the cross over build. There was conflicting information about the values of R1 and R2. I never got a reply. I looked at your videos Stephie, and it looked like you made them just like the picture as I did, And swapping the components does not seem to make sense. Does my schematic for the crossover look correct? Which resistor should be mounted next to the small inductor, and which next to the large? I made mine just like the image of the assembled cross over shown in the manual. 1.5 ohm resistor physically adjacent to the larger capacitor and larger inductor.

Thanks, I watched a YouTube video of the stock vinyl going wrong and I knew that was beyond me. Since you had broken corners, I would use auto body filler, and sand them till they are flat and square corners before trying to veneer them. Paperbacked veener would have been easier, but it is more expensive. Apply the glue to one side of speaker, than dry glue with hair dryer or gently with a heat gun till glue is transparent, or just wait if you are patient. The raw wood veneer would want to curl up and become unmanageable with glue applied. What I found worked well was using a sewing cutting mat, covering that with parchment paper, then putting the veneer on top, then tape the veneer and parchment paper to the cutting mat. Apply glue evenly with a putty knife or glue roller, then gently dry glue with heat gun or hair drier till it just becomes transparent. Then turn the speaker over and place on top of the veneer. Press down and then trim excess off with carpet knife or utility knife as close as you can without cutting into it. Like 1/8} extra is good target. Then flip over after all 4 sides trimmed, and iron on with gentle heat with parchment paper between iron and wood. Paper keeps glue from gluing to table if there are wholes, and protects wood during ironing. Cotton setting caused splitting, I think I did wool or silk, then let dry for 30 minutes then trim remains edge with veneer trimmer, or just sand flush with a sanding block carefully to not sand through corner, or router with trim bit. Once finished and complete, find the pre drilled holes and drill the veneer, and drill wide just through veneer layer, or screws will try to lift veneer. Glue. I used grill a gorilla glue carpenter's glue. In theory this can loosen with age, but will probably be fine for these small speakers. There is glue that is made specifically for the iron on method. I think it is called hot press. Do not, I repeat do not use cold press glue with iron on method, it takes too long to dry, and does not tack well. Hide glue works well, but needs to be heated up in water bath first, will slide around while wet, and it really needs a day or two to cure before doing the next panel. I reinforced my screw holes with CA glue (superglue). Picture below is what veneer looked like with glue applied, and dry to touch, ready to mate with other dried to touch glue on the cabinet. Trimming the veneer for the openings was done with a trim bit in a router, but the recessed areas had to be trimmed slowly and carefully with hobby knife and then used miniature cylinder drum sanding bits in drill to sand to edge. This took 3 weekends to veneer and finish, probably should have taken 4 weekends to not rush. I made lots of mistakes along the way.

I published before I was ready. Thank you so much for doing this series. This was a great introduction to tube amps, not sure you like rebuilding these inexpensive amps, but please know that you gave joy to many people who followed along. Thank you. Going to continue to read the books you recommended, specifically "Vacuum tube amplifier basics",by Ej Jerich. Then decide on which of your projects to tackle next. Thinking phono pre amp or one of the simpler home brew amps. Thanks again!

I just purchased an R8 in June 2023 from Amazon. It shipped from China to Mississippi behind the scenes and then domestically shipped to my address via UPS. Cracked the cover off this morning to look at the power supply caps to source a replacement. I found the same thing. 500Volt 330uF 105degC caps. Some of the resistors in my amp look pretty bad. They look to be different than what was in the videos, but still similar appearence issues. No infamous green resistor. My amp also has the hum. I have to put my ear up to the speaker to hear it, and it is worse on the pre-amp input like in the videos. But the amp sounds great to me in ultra-linear mode, but this is my first audio tube amp.