Inside Two VERY DIFFERENT EL84 Amplifiers | Rift Weekly Update

[@chokkan7]

Thanks for the tips, Chris; I learn something new every time I tune in. Happy holidays, enjoy your vacay.

[@Gavin-oq5tt]

Can’t wait for the concluding episode on the Marshall clone - it is really touching on the qualities that affect the sound (which is not often covered). Many thanks Chris for the great content and Happy Christmas!

[@benh7909]

Looking forward to the conclusion, nice video. 👍. Merry Christmas 🎄

[@DrKevGuitar]

Love the slowly dropping camera mount. Very cinematic! Thank you for everything Chris, you are the best channel in the KZbin amp world. Have a wonderful Christmas, and very best wishes for 2025 and beyond.

[@Anode230]

Morning Chris! Thanks for the interesting, entertaining content this year. All the best to you and yours for Christmas and the New Year!

[@Petaudiere]

Those older Vox vents break very easily, i would encourage you to tap them out slowly and evenly from the inside, there's a through hole, at leat that's how it is on mine. Or just replace the missing one.

[@southsidejohnny5624]

Morning Chris, great end to the season and, like all good soap operas, you finished on a cliffhanger to make sure we come back for the start of the next one 😂. It’s been very enjoyable since I found your channel earlier this year, thank you for your excellent content. You mentioned on the last video that there weren’t so many questions this time: could that be because you’re so good at explaining things as you go? I did have some electrical and electronics training many decades ago, including on valve circuits, but haven’t really used that knowledge since about 1980 but watching your fault-finding process has given me the confidence to have a go at trying to diagnose my brother’s Blackstar HT100 head which has a very mains-buzzy OD channel. We do have an authorised Blackstar tech near us so may well get them to do the actual work if it’s not an easy (and safe) fix. Have great break, you’ve definitely earned it, and see you after the holidays. 🫡

[@MyNameWasTecho]

Thank you for a great year of content. Always entertaining, always informative and always interesting. Wishing you and your family a very Merry Christmas and successful New Year. Ps if you fancy taking on an apprentice who is just the wrong side of 50, but is as keen as mustard, I know just the chap 😀

[@bambule5268]

Cliff hunger episode! Looking forward for 18watt part2. You tease!

[@joelkaplan8435]

You have been a wonderful addition to my youtube subscriptions. A few questions. I am/ have been working on my 1994 fender "The Twin", also known as the Evil Twin. Just a simple recap job and one burnt out resistor. The resistor was 10W 30K that was reading about 26k in circuit. I swapped it out for a fresh one but when I removed it it reads 30k. I thought it was fine to check resistors in circuit. maybe I'm missing something. There were no twisted pairs in the chassis which got me to wondering which wires in a valve amp should be twisted. The last question is is there a standard convention as to which preamp tube does what in the layout of an amp so I can tell what is V1 -V7 without reading a schematic and tracing it out? Love what you do keep it up and enjoy your holiday.

[@L0x0r]

Hi, Chris. Thanks for all the great videos this year, and for the awesome '69 fuzz pedal. I hope you and your family have a great Christmas. I was wondering though, if I wanted to get into building non-pcb based overdrive pedals, are there any books or other resources you would recommend for learning about circuits?

[@jamesunderhill1603]

Merry Christmas to you and yours as well Chris. Looking forward to the repair on both of these amps especially the Vox as it's the same age as me. Regarding filtering, can you put too much into a circuit and can you further explain ghost notes please, thanks, Jim.

[@DornAndGrant]

Another fascinating one - look forward to the resolution of the Marshall clone. Inspired me to go find a simple guide to how a guitar amp works just so I can follow it all better!

[@KevinVH-84]

So, what exactly have you fixed?

[@RiftAmps]

You’ll find out in the next episode that these amps are in!

[@hotdogpilot6319]

What happened with the mini Selmer? Did I miss it? Or was it small potatoes. I only ask because I have one....somewhere!!! Merry Xmas.

[@RiftAmps]

Parts on order, customer bringing it back in the new year 👍

[@hotdogpilot6319]

@@RiftAmps Thanks Chris....I'll be watching😁

[@ThomasB_N4G]

😎🤘💯

[@NINEWALKING]

There is nothing I like about that specific Bluesbreaker 18 Watt. Normally I love those amplifiers and I have my own version of BB18W. Normally I enjoy building amplifiers based on my own schematics and point to point topology but I do not mind building BB18W. I do not even know where to start regarding this amplifier. Let’s start at the plate voltage. I never go much over 300V for the plate voltages. Few volts above with the good EL84 tubes is OK but that amplifier has wrong power transformer. Especially with diode rectifier voltage will kill those tubes even if they were properly biased. It looks like someone built it for use with the 7189 tubes. Those can handle up to 400V. Now Old amplifiers used to have anything from 90 Ohms to 130 Ohms cathode resistors. At least that’s what you find in those. But nowadays with the higher mains voltages proper cathode resistor value is 150 Ohm with 10 Watt rating. It is bypassed with 100 uF cap. Now saying just 150 Ohm is right value is double edged sword. Looking from one side saying one value is correct sounds stupid because biasing of the cathode biased tubes should be at 90 and some people say even 100 percent of maximum plate dissipation. Contrary to 70 percent with fixed bias topology. Saying 150 Ohm not measuring plate voltage and plate current there fore leaves lot of variation for the bias value. But you can’t get wound power resistors rated 10 Watt in many values. So you get like 130 and 150 and 180 and 240 and so on. Some kits use 130 and those red plate often. 150 Ohms do not. 180 Ohm is most often to cold. Normal BB18W power transformer has 580V center tapped HT winding. Or call it 290 by two. With average EZ81 and proper first node capacitance it will land around 300V DC. Rectifier tubes have practically maximum capacitance that they should see directly at the first node. Often value used is 32 uF. That extra cap, if designed properly, should be used only with diode rectifier option. I would never add resistance in the rectifier circuit of the classic amplifier because I do not want it to lose its sag character. So that diode rectifier option and cap and that high voltage looks like someone wanted to have 7189 tubes and more like 25 Watt power. Maybe that’s why they used 180 Ohm cathode resistor although I can’t tell of top of my head what would be correct one with that voltage for the 7189 tubes. But definitely that voltage is way to high for EL84 tubes. Some people even cap at 280V. Many manuals say operating Voltages for EL84 is 250V and maximum is 300V. Good tubes can take 300V though. Changing power transformer is just to expensive especially for that kit quality. BTW that looks like China kit. That can cap and those sockets are tell tell signs. Tubes are done anyway. So I would remove that optional crap. I would get set of 7189 tubes and bias them properly. Once everything is grounded properly and as it should and noise level is still a bit to high I would add a choke and maybe some caps at further stages down the line. Like on plates of the V1. BTW I would change those sockets as well. I have only bad experience with such ceramic China sockets. 6 Belton Micalex cost like 15 to 20 bucks. Those are 1000x better. I would check all screws. Often you can create noise with loose screws as well. One could maybe notice that I am not a greatest fan of working on an amplifier built by the people who are doing it as their hobby. Most often it is faster to build an amp properly than go and check everything. I do not get surprised positively that often. Especially when people add mods and options. That tone stack defeat is old trick. Even Dumble used it. To be honest it does not fit BB18W in my opinion. TMB is signature thing of it so it is a part of the tone.