Handwiring the Tube Town JTM45 Kit! - Is it worth the effort?

Thinking about a Tube Town JTM45 Kit? Get some tips, see my conclusions. Perhaps it helps you to make your desicion. Have fun!

[@JayWye52]

I kinda wondered why so many builders used a TUBE rectifier when silicon diodes are SO much more reliable and low cost,but then i remembered the tube rectifier acts as a time-delay for the B+ voltages to the amp tubes,giving their filaments time to warm up before applying B+ to the tubes. (the old TEK 500 series tube scopes I worked on all had time-delay relays.) I would also be tempted to make a printed circuit board for the Rs and Cs and bias pot,then you won't have to deal with too-short component leads. it might help with hum suppression,too.

[@MrJLobster]

Seems a good Idea for an addition... Thanks for your comment!

[@JayBeBerg]

I recently built this EL34 kit, but with a lead spec board with mostly nos components. I am floored at how good it sounds. There were a few weird solutions that I modified and the amp is not a JTM 45 clone now but the tone is amazing. Just the right amount of volume and gain. Takes pedals if needed, very little hiss, looks good. Just plug in the guitar and ride the volume knob. So glad I built it!

[@jeanmichelk3629]

I have also built a TTjtm45 So satisfy with it Amazing. Tube-Town so professional. I recommend

[@os6997]

Very very nice job ! And nice sound ! Congrats ! And thanks for the video, very instructive ))

[@MrJLobster]

Thanks for your comment!

[@fenderblues100]

Mate, I really dig that catchy little tune right at the beginning!

[@TempoDrift1480]

Well either way you did a real nice job on it.

[@williambock1821]

Why of course it is! It’s a blast!!!

[@kraid80]

I'm going to build my first 18w kit very soon, this video is very helpful. Thank you.

[@MrJLobster]

Thanks - you´re welcome!

[@guitarshackbr]

Great vid… tks for taking the time to do this… I’m looking for a compact cab like yours. I play at small venues and taking the half stack JTM45 is not an option, so I go by the Studio SV20 head and a matching either 1x12 ou 2x12 cab. Would love to get a compact head cabinet so I could use my JTM45 chassis on it, matching my speaker cabinets.

[@michaelknight4041]

Man that's a great looking job! I remember the first amp that built was a pretty high gain preamp into a single ended power stage with one EL84, made about seven or eight watts. I had it looking really pretty but when I fired it up it was noisy as hell! 😂 I had to rework a lot of the grounding and a few other things before I finally got it to an exceptable level.

[@NoOne-sn2si]

Hi, my comment is a bit late... The reason that the signal never completely turns off at the input is NOT because of the potentiometer, it is because the first preamp tube (V1) has a shared cathode to ground. This causes the signal from one triode in V1 to cross over into the other triode of V1. This is common and normal behavior for JTM45 type amps. Thanks for the video

[@MrJLobster]

I know this effect. I had checked the pot and it was iffy. It didn´t short to ground there was always some resistance. Changed the pot - completely silent...

[@allanpennington]

@@MrJLobster Is there a way to check a pot before to is put in place and wires soldered to it?

[@MrJLobster]

@@allanpennington Yes there is. But you need a good multimeter (an analog one if possible) to measure the taper. It should have the required A B or C type taper and not exceed or fall below more than 10% of its value. The zero point have to be zero =0 Ohm. Check the housing of the potentiometers if there is any loosenes in the construction especially if you use it as a grounding point in your circuit. Check this again if you have soldered/heated up the pot.The expensive ones doesn´t always have the best tapered curve. Good luck!

[@qddk9545]

A few ideas: Try to leave the dark channel as it is, and try a Treble Booster with variable input caps on the dark channel for Classic Rock tones. For the stand by switch: It seems to be a real problem with newer tube rectifiers, and the current spike does not do any good to the rest of the amp either. I have not tried it yet, but putting a NTC (Thermistor) in series after the stand by switch could be a solution, or maybe better use a 2 stage standby switch, with a resistor in the first stage, that functions like a soft start on a HiFi amp. You could also use a soft start in a separate box, and have the standby switch on, when turning the amp on. But then you can not use the standby switch afterwards.

[@MrJLobster]

Thanks for your comment and your added knowledge! The problem cured itself after a while. In addition I shorted all the soldered wire strains at the rectifier tube solder lugs to bare minimum be completely flush around the lugs and bend them to get maximal air clearance to another. Could have had possibly an effect I´m not shure but the sparks in the rectifier tubes are long gone...

[@roncarter2188]

I don't like the standby switch, problematic is what they are good for. On my old Marshall amps I just use the power switch only. Nice build, very nice and neat work, well done!

[@MrJLobster]

Thanks for commenting! Thanks for your interest!

[@cgavin1]

Great video dude! Really enjoyed it. :) PS: Nice oscilloscope. PPS: No homo. PPPS: Good use of silver mica. I have exhaustively A/B'd them with ceramics and I much prefer them.

[@cozmovox]

Tube Town are the BEST kits you can get in europe ! THey're much cheaper than Tube Amp Doctor, they give you the best parts only , they're super safe and reliable. I built their bassman and it's a jewel ! you can trust their own output transformers, they sound GOOD ! Even the screws and bolts are top quality !

[@MrJLobster]

Thanks for your comments Cozmovox!

[@jernejkurincic9050]

Tube Town has been a place where I started my audioelectronics 12 yrs ago. I love their way of doing things, which is somewhat harder then some others (for most projets you get just the schematic and layout, no step by step guides), but helps you learn much more. They regulary tackle problematic issues of circuits. Their prices are nice. You can feel the community being in the background. Now I mostly do orders at bigger catalog vendors, but regulary return for the items they stock at good prices.

[@lowcountrythrash2874]

Your wire work is classy bro. I am a lineman/electrician, so I never encounter smaller components of this fashion, but I know quality work when I see it. I watched this video a few times as I found it well presented. I hope you put more of this out in the future. I’ve been a guitar player all my life and am just now getting interested in kit amps. I’m not sure yet how the best way to start a build is, but I am probably going to start with the most simple designs and progress from there with kit difficulty levels. Do you have any tips for a day 1, from the ground up, builder?

[@qua7771]

I was an electronics tech in the 90's that never encountered the small components that are used today in SMD.

[@odgeUK]

I bought the Tube Town FX Loop for my JMP 2203 and it was terrible. My tech could not get it to work right, and pointed at the design as being flawed. The loop would clip with some digital delays and had very little volume increase when using a clean boost in the loop. When I asked Tube Town for help, they would not help me until I sent a schematic! In the end, we put a Metropoulis FX loop in and that was absolutely perfect in every way. I think I would be inclined to go for a Ceriatone kit over TT...

[@MrJLobster]

Interesting experience, thanks for pointing that out for us. I personally don´t use fx-loops but a lot other do probably consider to do so.

[@jmc12fr7]

I used the 6112 kit in 3 differents amps, My TTX45, My Dumbleish Clone, and a 2112 Jet City. It's working really fine. You have to pay attention at the input level of the loop, and the value of the dropping resistor depending of the voltage you use...when using the // FX wiring, you have to get rid of the out of phase effects, cos they soak the level...When used in serial mode,it's working fine since you set correctly the send and return levels..

[@odgeUK]

@@jmc12fr7 It was the LND150 I used, the non-tube FX Loop.

[@jmc12fr7]

@@odgeUK the active ones, dumbleator or 6112 are active and you got a cathode follower for the first stage, I think it's a lot better than a passive loop

[@professornat]

How to correctly install knurled nuts: @5:00 Get something called "Guitar Nut Cube" or a "Uni Wrench". Both help a lot with removing pots too.

[@EnmandsBand1]

thank you for this video, I am considering to do this kit as well as I would like a handwired JTM built with quality components as a pedal platform. Also, the kit is smaller and lighter than a Marshall JTM 45 which is nice (and the MArshall doesn't fit on top of my new Zilla 1x12 cabinets 😀

[@MrJLobster]

I also like to get the 1x12 zilla cab - but importing it to my residence seems a little over the top if there are enough alternatives around - have fun with your amp projekt Jim R! The amp is an exeptional good pedal platform!

[@EnmandsBand1]

@@MrJLobster thanks, I am finishing my second Tube Town AC18 kit at the moment and making new housings for both heads with the same tolex and speaker cloth that I have used in my 2 homebuilt 1x15" Celestion Fullback cabs. When I'm done with that epic stereo setup I will consider building another kit.

[@MrJLobster]

@@EnmandsBand1 Good Luck Jim R! Respect! I didn´t dare the Fullbacks until now. But - I ´ve currently stocked up my woodworking tools to (hopefully) be able to produce headshells myself in the future....

[@gordonstanley7802]

This is really nice to see, thanks. Once thing I did not quite follow. You said not to ground the shell of the pots to the "star ground". Is that to avoid hum? Should you not ground the pots shells at all?

[@MrJLobster]

Yes Gordon you're right. And it is a messy and destructive thing if you have to remove one of the pots

[@eldredjoyner2556]

Nice quality build!

[@allanpennington]

What is the width and length of the turret board? You said it was too wide between the turrets for the resistors. What was the distance between turret centres along each axis?

[@giulioluzzardi7632]

Best tip yet! Use alligator clips to prevent damaging delicate parts while soldering! Why has no-one else mentioned this, it's was one of the 1st steps I was taught for soldering electronics?

[@jmc12fr7]

end of last year I built a TTX45 , with the TT jtm45 Power supply. I was not OK with the standby wiring, so I rebuilt it like the old fender Bassman. I get rid of R107, added a 0.047 to the ground, added two Diodes just after R108 and R109, and wired the output of the GZ to the first 32MF cap placed before the standby, I also adde a 330k resistor for bleeding this cap . So that way I take B1 after the standby and I don't have any sound when the standby is off The GZ just see 32MF when first powering the amp. This way there's no stress for the GZ34. I used a 3 way stand by switch to be able to get a triode or penthode mode.

[@MrJLobster]

Thanks for your comment! Very great Idea! In this configuration I would remove R108 /109 cause they where not needed anymore (with the 2 Diodes you have already added 330R forward resistance) and they can be an additional source of error. Definately worth trying. Does the amp hum OFF standby?

[@jmc12fr7]

@@MrJLobster there's a very little hum, but it's not bothering, and not more than my 1970 JMP. If you want I can send you my schematic. I asked tube town the reason of their wiring leaving an amount of current charging the filter caps even with the standby off, and so the amp is never silent. They told me that it was to protect the GZ34 from a big stress when the stanby is switched on. Anyway, that way my amp is really good and I don't see a big difference with a reissue . I used a push pulls pot to have the choice in between JTM45 or Plexi wiring with the separate cathodes on V1, and a push pull pot to boost the mids , I switch the TS slope resistor from 56k to 33k (with a 82 k //), and a 680 Pf // on C6, the treble cap. I also used another Push pull pot to have the choice having or not the C4 Bright cap. It's working very well.

[@gastaxxx]

@@jmc12fr7 Hi JMC, I have my jtm45 (with some mod like the original jtm 32-->16 cap and Sovtek GZ34), I removed R107 whit no bump or problems with rectifier and I'm asking how R108 and R109 change the sound and if them are needed respect the original jtm45 scheme.

[@jmc12fr7]

@@gastaxxx Hi. I didn't remove those two resistors, and added two diodes like I said in my first post. I like the idea of this voltage drop, lowering the main a la EVH variac... May be it's helping to get a brown sound.... Recently I added before the PI an active FX loop, serial or //, it's the 6112 kit of tube town.

[@atech9020]

It's not the JJ rectifier issues that you are seeing, it is the standby circuit design issues that cause things to go poopy. There is a very easy fix with just a couple of diodes that will solve the issue. Merlin of valve wizard fame has a solution to that problem listed on his site.

[@MrJLobster]

No it is not. It is poor contact quality in the switch. I put in a higher quality switch and the popping is gone. The standby circuit of the amp in the video is done like any other marshall vintage or reissue is done and worked until today. So no complaint about that. Any decent made GZ34 should work flawlessly. The "trick" in the article from Valve Wizard if read presicely refers to silicon rectifiers only. Doing so with a valve rectifier would nullify the benefits of a valve rectifier to some degree. TT added two resistors (which btw could have bin one if it was better thought out) in series to raise the impedance of the GZ34 because as they tell you of the bad behavior of "some" JJ rectifier tubes.

[@atech9020]

@@MrJLobster I’m not sure what you read, but the addition of a couple diodes in the tube rectifier circuit does not affect the sound or operation at all, acting as nothing more than a protective solution to the problem you mention. The resistor that goes around the standby switch is there to help take off some of the current through the switch by slowly charging the remaining power supply caps reducing the propensity to pop. There is no doubt a potential that the switch quality or style does matter. However I still don’t think it is a JJ tube only issue. The why is quite simple. JJ makes about 1/3rd of the worlds tubes. There are only 3 tube manufacturers in the world and JJ is one of them. They make tubes that are rebranded by several other names you know. I don’t buy the convention that x tube is just bad at x task. There is usually a reason why the tube is doing what it does and the circuit design is usually a part of it. The circuit in the jtm 45 is not A typical for Marshall. Most of their circuits have diode rectifiers. And since TT is making a copy, without A/B Ing the two circuits, I can’t tell you exactly what the differences are? Most of TT’s circuits are in the likeness of the inspired amp. So who knows what they change. Glad you got it fixed though.

[@MrJLobster]

@@atech9020 I use JJ tubes since almost 20 years now because I like their sound. I had problems in perticular with tubes from TT as a tube vendor. The JJGZ34 does act funky so TT came to a conclusion you can read only on the german description of the kit: "...Die Widerstände R108 und R109 in den Zuleitungen zur Gleichrichterröhre sorgen für eine bessere Anpassung des Netztrafos an die Gleichrichterröhre. Insbesondere bei 5AR4 / GZ34 Röhren aus aktuellen Produktionen ist uns immer wieder aufgefallen, dass diese empfindlich in JTM45-Verstärkern arbeiten auf Grund des oft zu niedrigen Innenwiderstandes der Hochspannungswicklung. Dieses Problem wird normalerweise durch die beiden genannten Widerstände beseitigt...." -So they know about the problem. Changing the standby switching circuit and adding R107 parallel to the switch didn´t change anything to the arcing noise of the switch.

[@edparker3549]

Thanks for the video. I'm in the UK, do you have any experience or knowledge of good kits? I'm really interested in doing a 50w JCM 800 or JMP but don't want to spend a lot of money on something that may not be good. Any help would be appreciated, thanks

[@MrJLobster]

The parts from tube town are ok not special but ok. I´ve ordered a regular Drake output transformer to hear it in the amp. It was louder clearer (which was to be expected as it had different impedances) but the tube town OT sounded little nicer to me and the attack of the notes (with EL34) is a little faster. As for the tubes from TT I had no luck until today - there was always a lemon included. But I have access to old parts and tubes in my stock from years ago so I do rely on that. The sockets are very good which is critical. The chassis meh- a matter of taste. TT does make custom faceplates what is definately to consider and the quality is fine. All in all it will be the best way to order a standard kit and customise it with upgrade parts from the beginning - I don´t buy from TubeAmpDoctor unless I need pharamacy.... but they´re tubes are really good.

[@MrCoolerdave]

Thanks for posting this. I have been considering building a kit. I was looking into the KDL's until I watched this. I don't own an O-Scope and while I understand what you were saying I could never figure the engineering aspects out on my own. Do you think Mojotone or Stewmac take out some of the troubleshooting aspects so the cost might out weigh the high probability of actually completing a working and usable amp?

[@MrJLobster]

Welcome MrCoolerdave! I think Mojotones or Stewmac will deliver you a very satisfying kit as TT does. There are a few problems to be expected as far as tubes and part tolerances go nowadays and I don´t think they will sort that out... but as long as the transformers are fine you should get a great sounding amp to work with. Good Luck

[@MarkSchuster-ym3iy]

Why didn’t you use the CTS pots instead of the inferior alpha pots?

[@MrJLobster]

Thanks for your comment Mark! Have you ever compared the taper of a cts pot to an alpha? As crappy as they may look like the taper is much much smoother while the cts are comming on very aprupt. This isn´t a good thing for amps. So I tend to stay with the alphas.

[@stringlocker]

My only question is what do I do with the leftover parts.

[@dietmargroe-wietfeld6543]

Beatyfull

[@stephanbriansoares3370]

what is the first song played?

[@mca1960]

@ 9:13 your hear also the green grass growing ?

[@johnsimms3957]

Do you prefer the sound of a tube rectifier over a solid state one? I'd rather go with a solid state one myself.

[@gordonstanley7802]

It is not so easy to change that for the JTM45 from what I have heard. You are better off going to the JTM800 which has that by design. The JTM45 circuit relies on the sag of the tube rectifier to avoid overloading some components (I am not sure which - I am not an expert, but just passing this advice on).

[@marcomeloni9626]

hey beautiful video! i just ordered a px18 kit, figured a jmt would be too loud to play at home...just one question about the wiring of the trimmer pot. on the diagram its soldered to the two back turrets and then it looks like something comes out from the left turret to the front of the trimmer but doesnt connect to anything. could you shed some light on this dilemma? thanks in advance!

[@MrJLobster]

Shure Marco Meloni - the positive (yes the positive!) lead of C 106 is going to the output lug of the trimmer pot on the turret and to the ground bus. R107 is going to the wiper and to the input lug of your trimmer pot. It is a little filigree thing and you should not mess up this part. I think the part in my video shows only a certain state where the trimmer pot wiring is not quiet complete yet. Good luck and success!

[@marcomeloni9626]

@@MrJLobster thank you for the fast answer! thats weird because thats what it looks like in my diagram(PX18). When i look at JTM45 diagram, it looks like C106 is going to the output lug and then to the input...weird..

[@MrJLobster]

@@marcomeloni9626 it makes no diffence cause the trimmer pot is linear. Therefore it behaves the same in both cases. It acts like a variable resistor either way and not like a divider,

[@marcomeloni9626]

@@MrJLobster cool! i guess theres a whole lot i need to learn...

[@marcomeloni9626]

Hi, i was finished building my PX18 and it sounds absolutely killer. the only issue is that when i turn the presence control all the way up it makes this weird kind of frying noise. only when its all the way up. turning the treble down does help a bit. I tried poking around with a chopstick but didnt help...Have you had any experience similar to what im experiencing?

[@MultiGolonka]

Do you think it's reasonable to build a variation of Jose / Cameron mod JCM800 from ground up? Fortin used to sell them as their own amp, but those are discontinued, and also riddiculously expensive. I got hyped and I am considering building one or ordering custom built from a local amp builder. I'm not in a hurry by any means, since I would have to save some cash before hand, but I'd like to hear your thoughts on that matter.

[@MrJLobster]

If you think about modding a TT JTM45 kit in the J/C direction - I wouldn´t do it. The JTM45 is waaay to loud as a basis. Believe me it distorts around 7 -8 on the dial and it doesn´t sound very much like the usual marshall´s do. The OT transformer of a JTM45 isn´t right suited for something like that. I wouldn´t use any 4 hole marshall kit either for something like that. I´d think about the Pink Taco (TT PI 18) Kit or a JC18 as an alternative starting point in the direction. Maybe a cathode biased EL34 power amp with a 3,4k OT seems reasonable.

[@MultiGolonka]

@@MrJLobster I meant from the ground up, no kits involved - first gather parts and then build the whole thing from scratch. As of now it seems like a tall order for me due to lack of experience, but I'm reading a lot. Also I consider saving a little more and giving it to someone with a proper experience, but estimate is around 1.000 USD which is a whole lot of cash for me

[@MrJLobster]

@@MultiGolonka It is a whole lot I know. I would consider to get a broken real one or a reissue to begin with which is not too hard to find here in europe. Good Luck!

[@yaniv-nos-tubes]

NOS tube set for jtm 45: v1,v2 ,v3: 1959-1964 mullard i61 shortplates

[@dietmargroe-wietfeld6543]

Nice, SUPER

[@unboxedtravels]

@MrJLobster thank you for the video, very interesting ! I've just started looking into building my own amp and don't really know if I should buy a kit similar to this one or find a schematic and buy my own parts. Can I save money by doing that and if so, is it worth it (amount saved VS the trouble of finding parts) ? I'm in Canada, do you know a good kit seller (besides TT) and where I could find a schematic for something in the 15-20 amp range ? Thank you so much !

[@MrJLobster]

Thanks for your comment Sebastien! Isn´t Trinity Amps located in canada? Well respected company for they´re Amp Kits. If you´ve just started into building amps I would definately recommend to start with a kit. You will not safe enough to justify all the hassle finding decent parts.... and it is time consuming. I think a nice 18W marshall tremolo is a very satisfying projekt to begin with.

[@unboxedtravels]

@@MrJLobster yes they are ! I read about them and saw their website, very nice. But a bit expensive for a first time build. I'll try and find a small kit somewhere to start "slow and easy". ;-)

[@timofenimem2481]

Is it worth buying and assembling this tube amplifier?

[@MrJLobster]

14:25 13:34 13:14 it depends on you skills, expectations and your financial savings. Please take a closer look at the timelines.

[@timofenimem2481]

@@MrJLobster thanks. But the problem is that I don't understand English.

[@bouillefabien1195]

Great video, thank you! I know how to solder, how to use a multimeter, i learm quickly but honestly I do not have amp skills so if there is something wrong I won't be able to fix it, I thonk I will get a tweed pedal....bouahahahahah......

[@MrJLobster]

Thanks for watching fabien thanks for your comment!

[@geezberry8889]

why not 5881's or kt66?

[@MrJLobster]

Because I had some nice NOS EL34´s in spare....

[@russellesimonetta3835]

I hear the Ceriatone amps DON'T dissapoint at all. But for international builders source your own iron! l

[@MrJLobster]

I also tried a TAD 3k6 50W Drake Style OT in this build but I have to admit the 6k6 /8k TT OT (from Italy btw) sounded a little bit richer to me and it wasn´t as loud right away.

[@paologisela]

@@MrJLobster yes from Italy, good quality

[@MrJLobster]

@@paologisela Thanks for you comment Paolo! I used american transformer replicas in the past. Did a test in this amp with a drake type OT (the M50A from TAD) Of course with all the "correct" impedances for a 1987. The stock italien OT in this kit sounds nicer!

[@xtidnab]

you "must" mechanically splice your leads, the solder joint "will" fail otherwise... a proper solder joint will be "shiny", if it's got a "dull" look it is too "cold" and will fail... do not use lead-free solder, it will fail...

[@eldredjoyner2556]

This is one kit I will pass on

[@gregj.gotham4402]

Doesn’t seam like a good kit no matter how much you saved in dollars. There are better kits for the JTM45. I’ve seen them come with everything with no issues.

[@MrJLobster]

It depends on which part of the world you live in. If you live in usa it should be possible to get a quality kit from elsewhere. Living in europe (which real marshalls are comming from btw.) the TT Kit is a good option. Why? All parts from Europe NO parts from china. JJ tubes are from CZ. The chinese had once good tubes now all the factories seems to have closed. Russian tubes shouldn´t get on the market or should be banned... the word is getting more and more complicated. Good Luck Take Care!

[@jutukka]

A very expensive, unreliable and inefficient tube rectifier does not make any amp sound any better than an amp with properly designed same output voltage power supply using solid state rectifier. If you want that voltage sag and power loss caused by quite large inner resistance of a tube rectifier, just add to a ss rectifier a series resistor with a value matching the inner resistance (which, TBH, is not absolutely linear but quite close) of tube rectifier.

[@MrJLobster]

@@jutukka you can also buy a new JCM800 or JTM. Seems to be the better investion nowadays. I know exactly what and why I'm doing the things the way I do. I would not encourage anyone to do it the way I do. Enough out there pretending to do things much better and much more reliable than Fender or Marshall did of which the amps lasted only 60 or 70 years. And I haven't got the deep sonor voice of truth...

[@jutukka]

@@MrJLobster I of course have amps using tube rectifiers, and I never, for many reasons, mod them to use ss rectifier, because I have a bunch of NOS Miniwatt GZ34's etc. But when I have built new tube amps and tube reverbs etc., I haven't used tube rectifiers any more for many years because IMHO there is no good reasons to use them anymore. P.S. Your videos are excellent and very enjoyable to watch. 👍

[@MrJLobster]

@@jutukka Thanks for your comments. Fender also skipped the rectifiers on a bunch of reissue amps like the vibrolux 68 for example and they sound just fine... so you´re right it is not the rectifier that forms the sound of an amp...but they do glow nicely ... when you can afford it...

[@geoarthur6593]

Horses for courses .. weighing up everything, nope ..