Ceriatone Forum

I'd like to hear some opinions of the JTM45/100 that Nik produces.

What cabs go great with this?

Marshall 4x12 with G12T-75?

I've had Niks' 45/100 for almost a month now and I really like the tone.I use my over 30yr. old strat style Ibanez guitar on the neck pup and a fuzz that I keep on all the time,I also jump the channels which gives me a deep rich sound. with a turn of my guitars' volume knob i can go from clean to distortion.It's not a heavy metal amp,it lets your picking technic and dynamics come through.
It's a classic rock amp so that if I want long singing sustain and feedback with my setup I have to turn it it up to about 5 or 6 which I haven't done too often because this amp is loud,I mean very,very loud. I LOVE IT.Nik installed a PPIMV which I use at home but at band rehersals I run it out of circuit because I don't need it and it seems to have a slightly better tone.He also installed an external bias so I can check and set the bias myself with no problems.I have heard it said that when you turn a 45 up the bass gets flabby,I haven't had this problem.I have noticed that when I do turn the volume to about 6 I begin to hear faint ghost notes.I haven't asked Nik about this yet because I wanted to do as much research on it before I bothered him with questions about what if anything can be done about it.
This amp has the volume and tone I've been looking for,this is classic Hendrix.
   As far as cabs go I use a Marshall HW1960b which is a great match for me.
I don't know if the 45 has the same tone as the 45/100 just at a lower volume,but again let me warn you if you thinking about getting this amp.
   It is very,very loud.

I have the JTM45, am looking to get the 45/100 in the near future.

The ghost notes is probably the speakers, rather than the amp?

I think the speakers in the HW 1960B are G12H30 Heritage.
Ouch! 120W handling, probably the cause of the ghost notes.

Have you tried it with a regular 1960B? Those loaded with G12T-75s. Those are rathed 300W handling.

Btw, thanks seekers.

 Yeah, I didn't like the scooped mids of the regular 1960b cabs and when I use my fender super reverb to push my HW1960b I don't hear the ghost notes.But like I said earlier it's very faint and at 6 i'm extremely loud. Also if I just run through a single channel at that high volume the ghost notes are even harder to hear.I love the sound the HW1960b gives me with this amp so if it turns out to be the cab then I am going to have to live with it because to y ears they were made for each other..

Time to pair in a 1960AHW :P

seeker -
Nice review.
If the ghosting continues, you may want to try/get Nik's opinion on increasing the B+ filtering.
Good Luck

lightice thanks for this thread and yes  the HW1960A cab is what I want next.
  hired hand thanks for your words also.
 Nik and his people built this kit and did a great job,but what I want to do in the future is order an unasembled kit and have the satisfaction of building it myself so that when builders like hired hand talks about B+ filtering I'll know what he's talking about (HA,HA).
      I've been reading the forums that have builders talking about different aspects of mods and repairs to learn as much as I can because I don't want to ask questions about something you guys may think I should already know.
 Again lightice thanks for starting this thread and hired hand for your insight,hopefully others will chime in and my knowledge will grow.

NP, I too wish to learn like you.

Its great that you've contributed to this thread.

I have no idea where B+ is located in any amps, but from what I've gathered, its the voltage supplied to the circuit.

I've a couple of Nik's amps and would like to get the JTM45/100, just that I'm not sure what to pair it with.
And Nik doesn't make 4x12s, so getting a suitable cab and speaker combo here is kinda tough.

Btw Seeker, are you or any amp tech in your area able to measure the RMS and peak output of this beast?

B+, an explanation from someone who 2 yearsa ago thought it was an essay grade!

The rectified output from the power transformer is still a bit AC'ish in that its not a constant voltage, with residual peaks and troughs. The smoothing caps aim to do just that, remove these peaks and troughs and allow the supply to the amp to be a smooth DC.

Thanks hywelg,

Btw, I gather that a JTM45/100 B+ should be high, 500V? Or thereabouts, but I see the PT in nik's layout  supplying 360V, noob question, but how did 360V get to 500+? I think this is the plate voltages.

I know after rectifying, you get whatever is put into the rectifier circuit. Albeit peaky and what not which requires filtering.

lightice from what I understand these old school amps are generally rated at RMS. In other words a 45/100 would be anywhere between 80 and 100 RMS,hope that helps.
  Also the comments of hired hand and hywelg have led me to not only to research B+ filtering but also what role the choke plays in filtering.
 I guess I'll check the choke size and ma. at a later date after more research since it seems that it along with the filtering cap could also be the culprit.

Yup, they're rated at RMS, but there's a way to calculate the actual output. George from metro did run thru it before. Something about using some meter on the output and sending a sine wave thru the input.

Then doing some calculation.

If you every do get to find out what's wrong, please do let Nik know, he continues to develop and refine his products based on customer feedback. I'm sure he'll want to know what's the problem and help you solve it.

Have you checked your bias lately?  A mismatch in the output tubes can cause this problem.  Not a mismatch of 4 or 5 MA, but something a little more extreme.  Does not matter how new your tubes are, they can take a shit on you at anytime.  By the way, have you tried a different set of tubes?
Again, I would not hesitate to contact Nik. He seems to have a genuine concern/interest in his customers.  I am sure this problem can be fixed.  Especially considering how pleased you seem to be with this amp; it really needs to get corrected.
Good Luck

hired hand the highest ma is 40 the lowest 34 on the power tubes.
 I'll try another set of tubes as soon as I can make up a believeable lie,I mean reason to my wife for spending another hundred plus dollars on tubes. I'll also see who sells tubes that are matched..
  I want to add that like I said earlier the ghosting is faint and and unless it gets very annoying it's not a big deal so I'm going to approach this as a teachable moment on amp building and troubleshooting...

Isn't that bias values v high for a JTM45/100?

Here are some replies on the same topic on the metro forum:

http://forum.metroamp.com/viewtopic.php?f=15&t=16926

Might wanna ask Nik what the plate voltages are, then from there work out the bias values.

For 560V plate voltage on the JTM45/100, at 70% , they recommended 30mA. So first e-mail I'll do is to shoot Nik asking him for recommended bias values on his circuit.

No,Nik said when he gave me directions on biasing that he liked it to be between 38 and 40 so I biased to the hottest tube to keep in range..

Ah alright, thanks.

I think "lightice" may be leaning in the right direction.  But I am pretty confused at this point, probably my own fault.  So if you don't mind me going back over some common ground......

1.  I am not familiar with these amps at all, so pardon me for asking.  This amp uses 4xKT66 in the output and is SS rectified, is that right?

2.   Are you saying that you see 550VDC on your plates, and your current is between 34-40 MA?

3.  I am not sure if the KT66 is a 25 or 30 watt tube, but at 34MA your power is almost 19 and at 40MA your power is up at 22.  Even if the 66 is a 30 watt tube, your 70% mark would be 21 watts, obviously at 25 watts that mark moves down to 17.5 watts.  So I am thinking that maybe you are pushing the limits of what would be an advisable bias.  But it all hinges on what numbers you are seeing at the plates.

Can you confirm you plate voltage one more time?

hired hand just got back in town and saw your question so i doulbe checked Nik's e-mail.
 He did say he likes to see between 38-40ma on the kt66 tubes.I know just enough that I can bias them lower to see if that makes a difference but as far as plate voltage if you want to give me instructions on how to check it I'll be more than happy to and give you the results.
  I'll try biasing them lower  and crank my amp tomorrow if I have time and see if that makes a difference and let you guys know.

If you're using Shuguangs, which are real KT66s. Here is the datasheet from analogmetric .

It's a 25W tube, but max plate voltage stated is 500V. So I'm not sure exactly what Nik's got on the plates for his 45/100.

(http://www.analogmetric.com/forum/attachments/Shuguang%20KT66%202_vchaLfaEgXsH.jpg)

Hey seeker -
How is it possible you know how to read plate current, but not voltage? :) :) :) :)
Which makes me wonder, are you measuring plate current from the cathode that is grounded via a 1 ohm resistor?
Anyway... to measure plate voltage, set your meter to VDC, clip on to chassis ground, put your probe on pin #3 and see what you get.  This will give you the other half of the power equation.  
Plate voltage or plate current by themselves is somewhat "useless".  It is important to know both numbers.  So let's see what you get......

Actually Nik can make external bias probe sockets to read bias current easily.

I can do that on the JTM45, but I'm rather apprehensive about opening up the chassis and checking anything, especially probing around knowing there's 400+ v in the circuits. Due to my lack of electronics knowledge, I rather not get shocked to death.

If there's anything wrong, I can usually just bring it up to Nik, but as yet nothing's gone wrong.

Thanks hired hand for the info for reading plate voltage,and what lightice is saying is one of the mods I had Nik do for me which is an external bias(probe sockets and an adjustable pot on top of chassis) since when I say i'm new at this I really mean it,so I'm really trying to live another day.
  What I'll do is bias it colder and see if that makes a difference report back and then follow your instructions on reading plate voltage..
 But like I said earlier the ghosting is very faint, only occurs at extreme volumes and not annoying,but this troubleshooting might be of help to someone else because it's definitely giving me a better undertanding of how this amp works...
 Just did a quick read on Metros' forum in the tube section and if I read correctly 400v*40ma would give me 16watts which would be 64% on my 25 watt Shuguangs.If my understanding is correct then that would mean that the 38-40ma range that Nik recommended would be just right.
 Hopefully you guys will check my math and let me know if i'm missing something. :-[

The max plate voltage that the shuguangs can take is 500V , from the data sheet.
So I'm not sure, I guess the only way we can find out is to actually take a measurement on the plates itself.

If Nik made the amps run at 500V, then its a tad too hot. If I'm not wrong the shuguangs are very robust tubes. But I think Nik would probably run the amps lower. I haven't e-mailed him about them, although I'm sure he's already measured them. He probably has the values off his head, but if you know how to check, it'll be great.

Please be careful and ensure all safety precautions are taken, there are highly dangerous voltages in the amp that can kill, even when switched off, as the caps still have high voltages unless drained.

Btw, seeker, thanks for the constant updates. Its a great learning process.

seeker -
Your math is correct, if your assumption about a 400V plate voltage is accurate.  I have a feeling, however, that you will find it is higher than that.
Let Us Know

Just checked :Plate voltage 485 which would mean that altough I might be running a little on the hot side of the bias it's not bad.
 Also tried running it biased colder but could still hear the faint ghosting. But do remember I only bearly hear it and then it's only at stadium levels,and i'm not joking we're talking very,very loud.
   It also sounds slightly better in the 38-40ma range.
 So, in the end I rebiased to Niks recommendation.



 

I see, thanks seeker.

I guess next to look for is what hired hand has recommended, to increase the value of the filter caps.
Have you discussed with Nik the possible recommendations on his part?

I think that for the moment i'm going to leave it alone and enjoy playing it.
 If you knew how loud it has to be to hear the ghosting and how faint it is you would see why I say i'm not going to worry about it.
 I'm just going to keep reading to gain more knowledge and ENJOY!!

Have you considered less efficient speakers?

Something in the 97db sensitivity range. The G12H Heritage are 100db sensitivity.

If volume was an issue, I'd go with less efficient speakers.

Volume,s  not an issue at all, I love loud...
 Now it's just time for me to sit back and enjoy the tone and the volume....

Have you compared it to the JTM45?

I do want to build a 45 in the future for the knowledge but have not compared it to the 45/100.
  Was trying to give you an idea about the great tone and quailty of the45/100 in my first post.
 I researched Niks 45/100 before I ordered it and knew it was what i wanted. As I said in the first post the 45/100 with the mods Nik put in is perfect for me.This is my dream amp!My search for my perfect amp is over.
  I'm more than satisfied...

I actually already have 3 amps from Nik.

The JTM45, DC30 and 18TMB.

I've visited Nik before, exceptional guy and his staff are v friendly and helpful.
His builds are reliable and very well done. I couldn't be happier with the amps from him.

I wouldn't consider anyone else to get amps from because he provides so much value for the money.

But his website has so many great sounding amps its difficult to choose, an easy solution would be to buy everything, but as with everything, $$$... lol.

seeker -
Sounds like you are all set.  If you start to feel like it bothers you, or maybe it is getting worse, you can make a change.  You might get a lot of relief from just replacing the first filter cap after the rectifier.  Sometimes it does not take a whole lot.
Good Luck :)

hired hand, thank you for your help.
      If you have any books or anything else to suggest that would help in the learning process of terms,locations,functions of parts or anything that you think I need to know,Iwould appreciate it.
             Again,Thanks..

 Just a quick update since it's been a year. My 45/100 is still sounding great with no problems and I plan on taking it in the stuido within the next couple of months

Thats cool man, let us know how it turns out for the album!

Thanks!

Nik

Nik I'm the dude that e-mailed you (hence the name lol)

Just bumping this thread in case anyone wants to give me more info about the way this amp sounds haha. I already pm'd seeker though.

Good Luck in the studio. Would love to see some video, or maybe a few sound clips at least......keep in touch.

Hi Cam!

Welcome!

Sure thing, hope you hear from seeker, and if any questions (tech, etc), do email me.

Chip  :),

The plate voltage is abt 470-490V.

Originals did go higher.

But I wont subject my clients to using NOS tubes only (GEC KT66s wow these are crazy pricy now!).

So we lower it a bit.

I am not sure what JJ KT66s, or other new brands can take. Anyone know if those can go higher, voltage wise?

I like the Shuguangs though but will try those Gold Lions (sovtek) soon, see how those sound like.


Thanks!

Nik

my new genalex kt66s have been running at 510v (65% heat diss) for one and a half year without any problem. they sound better than the shuguangs to me

 Well, unfortunately i don't know how to post a soundclip. Can someone help? I appreciate it.
  Hopefully this falls under "there is no such thing as a dumb question".

Hi seeker

I think it usually needs to be hosted somewhere?

How big is the file?

Maybe if OK, you can email to me, and I can upload to my website, and then will link from here for people to see.

Thanks!

Nik

Hey Cam,
          Nik has a coupe of my clips posted on his site now.
   The first is clean,fuzz,clean
   The second is from my bands rehearsal
    Hope this helps
                              seeker

Well it's been over two years and wanted to say that this amp is still going strong, no problems. and when my cab speakers finally got broken in, it really shined!Th PPMV lets me play it in the smallest of venues and when I can crank it, it kills! If you want to hear it in action check my Bands youtube page.
Rannons' Call..Thanks again Nik!!

seeker

hey man, thats very cool, glad to hear you're still loving it.

As for ghosting, it happens indeed. it's a trade off, I guess, between stiffer filtering, and lower. The tone does change, if you tweak the filters but i guess it's a matter of balancing both.

Thanks!

nik

I sent you in pm