Elekit TU-8200 DX Headphone/Speaker Amp Review

[Lasollor]

I have not done anything like this with my amp (yet), but have done it with other equipment powered by massive transformer and rectified with huge caps and then had to rebuild vaporized traces in the power supply. A wire hanging out or a careless move with a screwdriver is all it takes to short things. This is why I apply PTC thermistors to all power lines when I design my own stuff. Of course when you replace components that don't fit into allocated space you have even more risk so need to think through both electrical isolation and thermals.

I don’t know anything about electronics or how amps work and sometimes I wonder where did I find the courage to try to build an amp like this. (I think this thread was the main reason) I even had to but the screwdrivers and every tool new just for this project. So I messed it up a few times. Then read about it and made it right. I’ve learned a lot on the way and it was really fun.

 

[Dimu]

I don’t know anything about electronics or how amps work and sometimes I wonder where did I find the courage to try to build an amp like this. (I think this thread was the main reason) I even had to but the screwdrivers and every tool new just for this project. So I messed it up a few times. Then read about it and made it right. I’ve learned a lot on the way and it was really fun.

In that case make sure you stay away from those orange wires hanging off the output tubes- there is more than enough voltage there to zap your heart for good. And keep kids away if you have any around.

 

[Dimu]

Good tubes will make a bigger difference than switching output topology.

Speaking of output tubes- swapped EL12 spez back in after long time with TT21. Both are awesome but I had impression I liked TT21 sound better right after I pulled them. Having said that I had a bit of similar feel when I swapped EL12 spez out for TT21. Spent couple hours listening to different records and swapping tubes and there are situations where EL12 spez sounds better than TT21. TT21 sounds great in that case, but EL12 spez sounds really special and engaging. I guess EL12 spez is going back into the amp.

Been checking on tube supply recently. E80CC is probably never going to be plentiful again. They are still around but low quantities and expensive. Same story wtih EL12 spez- price has doubled in a year and supply is very low. TungSol 6550 and GEC KT88 are nowhere to be found as are 211/845 tubes that I wanted to find for a different amp project. I already have lifetime supply of NOS tubes for this amp but I will definitely grab more tubes when I find some reasonably priced ones.

 

[Lasollor]

In that case make sure you stay away from those orange wires hanging off the output tubes- there is more than enough voltage there to zap your heart for good. And keep kids away if you have any around.

I’ve read that a couple of times but thanks for reminding me again. I do plan to build some kind of cage for it. I try to be as careful as I can be, I made a cable with a big resistor to discharge the caps every time I open the amp etc.

I picked up 6 pairs of Valvo E80CC for cheap when I had the chance. How long these tubes would last in this amp in your experience?

 

[Dimu]

This is how far Fluke pen picks up- it is rated from 90V and it is designed to be inserted into an outlet to touch the wire...

 

[Dimu]

I picked up 6 pairs of Valvo E80CC for cheap when I had the chance. How long these tubes would last in this amp in your experience?

If those are new you are set for life! They are formally rated at 10000 hours. Even if they last half that long you have multiple decades of daily enjoyment ahead of you

caps will have to be replaced many time before you wear out 6 pairs of E80CC. Many caps are rated at 1000 hours only. Even really good ones are 3000 hours. So you will need to replace caps at least 20 times before you have to buy more E80CC

 

[Effusion]

Welcome to the club @Lasollor!

Congrats on tackling this kit for your first project, impressive! It sounds like you've learned a lot while building/tweaking it, and I know while it must have been very frustrating at times, it was fun and rewarding in the end. I'm glad the thread helped so much too!

Wow, you've done a ton to it! Thanks for sharing all your experiences... now you, in addition to @Dimu, are making me want to rip the top off my unit and go to town as well. Some nice E80CCs sound like a good idea to me right about now! Just got to go for it in the end right... I've always thought about a separate unit to drive some proper single drivers in a different area, so maybe I'll just start fresh and keep this one the way it is eventually.

I also wish the availability/prices of good NOS weren't such big issues for many tube types as well... we just need more quality new production manufacturers to figure out where they are going wrong currently, make them as good or even better than old stock, and produce a ton of variety! Wishful thinking I know, but at some point the demand will be too high to just be ignored any longer, plus with what some are willing to pay currently, prices would be there as well to justify doing it right. Really just too bad it is so hard to manufacture them correctly and that with the dying of the art decades ago, also soon comes the dying of the knowledge in a way as well. As a side note, I recently meet a woman owner of a piano show house and she mentioned her son makes all the tubes for his amps at home in his garage... sounded crazy to me at the time, but now I want to learn more!

Anyway, cheers to the amp and thanks for posting!

 

[Sir Gaben]

Elrog are suposed to be a good quality brand, but they manufacture 211/845 and 300bs only at 1500 dollar a pair.

 

[dawktah2]

Being a newbie, I grasp concept of "tube rolling," but do you have let tubes cool first or just turn unit off so there's no power?

 

[Sir Gaben]

Being a newbie, I grasp concept of "tube rolling," but do you have let tubes cool first or just turn unit off so there's no power?

I usually let the tubes cool off for 5 min or so before I switch tubes.

 

[Dimu]

I pull the tubes out as soon as I can hold them. When tubes are in a big socket that does not get hot I pull the tubes immediately after powering off the amp. For tubes that have no cool base I let them cool down, unless I am impatient in which case one of my socks comes off to get slipped onto my hand to grab a hot tube

 

[sunneebear]

I pull the tubes out as soon as I can hold them. When tubes are in a big socket that does not get hot I pull the tubes immediately after powering off the amp. For tubes that have no cool base I let them cool down, unless I am impatient in which case one of my socks comes off to get slipped onto my hand to grab a hot tube

Yeah I do the same. I just give it about 10 seconds after powering off just in case something needs to discharge. After that I use a microfiber cloth that is used to clean the tubes to pull them out and put them aside to cool.

 

[dawktah2]

Ok, resoldered the connector in post #896 in this thread. I disassembled since crackling was getting worse and this is what I found.

 

[dawktah2]

So I removed all the prior solder and cleaned the pad. Fluxed the pad applied solder and desoldered it again. Recleaned it and applied flux second pic. Then resoldered third pic.

What component(s) could have been damaged by the initial pad going unsoldered that I should consider replacing? I will post again in about an hour if crackling is still present. Unit has been warming up for about 30 minutes.

--Chris

 

[dawktah2]

Crackle all but gone can still hear very very slight. Any ideas?