Ceriatone JTM45/100 with EL34's question ?

Kelia

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Hi guys, I got a JTM45/100 clone yesterday that has EL34's instead of KT66's,
the amp really sounds good , the clean is bold and with a humbucker guitar it gets into crunch territory , what are the pros and cons of leaving the EL34's in versus installing KT66's ?
Transformers ok for 34's ?

The previous owner had a London Power Tube buffered effects loop installed , works great but I'm a little lost with the send and return levels , never had in and out loop levels before .
Lots of carbon comp in there , don't know if it was there when the amp was wired or a previous owner had this done .

Thanks for the help !

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Kelia

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That is a nice build !
Thanks ! to be honest , this thing is awesome .
I have Metro JTM45 with Gec's and all the goodies and while it's a wonderful amp ,
I am really surprised on how great this one sounds ! and also fun to play while beeing quiet .
 
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yladrd61

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Thanks ! to be honest , this thing is awesome .
I have Metro JTM45 with Gec's and all the goodies and while it's a wonderful amp ,
I am really surporised on how great this one sounds ! and also fun to play while beeing quiet .
Nice amp !!! I ordered one a few months ago, still waiting for it to get here.
 

Kelia

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Nice amp !!! I ordered one a few months ago, still waiting for it to get here.
Awesome , think you'll be in for a treat ! So curious on how KT66's would sound
in this thing since it was designed for those but for some reason ,the EL34's sound great in mine.
 

yladrd61

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Awesome , think you'll be in for a treat ! So curious on how KT66's would sound
in this thing since it was designed for those but for some reason ,the EL34's sound great in mine.
I have been waiting over 6 months now I ordered a complete Amp less tubes.... In the mean time I ended up getting another nice pro built JTM 45/100 clone !!!!
Super 100_1.jpg
 

Kelia

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Calling @neikeel , Neil , should I install some KT66's in this amp or leave the 34's in ?
What are the pros and cons of leaving them in ?

Thanks in advance for your time Neil !
 

neikeel

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I like KT66 in mine. The correct OT for a 45/100 is 4K primary (half that of a traditional two valve JTM45). They sound good but not 100w.
The EL34s work best with primary of 1.7 to 2.2 if you want max power (100w plus) so if it has EL34s you will have been using the 16ohm tap selection into an 8ohm cab thus far?
So to use the KT66 you can now match your amp setting to cab normally.
 

Kelia

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I like KT66 in mine. The correct OT for a 45/100 is 4K primary (half that of a traditional two valve JTM45). They sound good but not 100w.
The EL34s work best with primary of 1.7 to 2.2 if you want max power (100w plus) so if it has EL34s you will have been using the 16ohm tap selection into an 8ohm cab thus far?
So to use the KT66 you can now match your amp setting to cab normally.
No , I haven't , went 16ohm out to 16 ohm cab , I'll try it tonight with two
16 ohm cabs and see what happens , I guess I should hear a difference ? I've read this so many time
and completely forgot to do this mismatch for myself .

Thank you Neil for you help !
 

Blake K.

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I’ve run both KT66 and EL34’s in my best friend’s 8000 series original 45/100 with the 4K primary 1202-84 OT. I like the EL34’s a bit more, they compress nicely and introduce some more harmonics. Also, the bass will be a bit tighter and the overall sound a little more balanced. The primary impedance really has nothing to do with whether or not you can use a certain tube. Tubes want to see an ideal primary for ideal frequency response. But as long as your power transformer will put out enough current, in this case 45/100 PT’s are rated at around 7A which is plenty for either type, and the tube pinouts are the same, you’re generally going to be okay. EL34’s have a much lower screens voltage spec at around 450v and larger screen grid resistors will be needed to get it down to a safe level. My friend’s original runs at 560v with tubes loaded. I think Ceriatone specs their 45/100 at the typical modern clone spec of 500v, so ideally you’ll want 1.5k ohm screen grid resistors for EL34’s in your amp, unless you have a 20H choke, in which case your screens voltage is probably okay.
 

neikeel

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Ymmv.;)
Depends on which make of tubes too as to which can cope with high screen voltages, 1k5 makes very little difference to the voltage or screen current when pushed.
Wonder why Marshall went to trouble of the -119 then -132 and subsequent Dagnalls?
I guess you go with what you are comfortable with. :agreed:
 

Kelia

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I like KT66 in mine. The correct OT for a 45/100 is 4K primary (half that of a traditional two valve JTM45). They sound good but not 100w.
The EL34s work best with primary of 1.7 to 2.2 if you want max power (100w plus) so if it has EL34s you will have been using the 16ohm tap selection into an 8ohm cab thus far?
So to use the KT66 you can now match your amp setting to cab normally.
Hi Neil, finally had my tech install a matched quad of Gold Lions and the amp sounds pretty good , he told me
that the previous tech who install the London Power effects loop didn't know what he was doing , it was connected before or after something and was
the wrong way to do but don't remember what he meant , he also said that because it was a tube buffered loop , it was installed
at the wrong place in the chassis because it was interfering and making noise , ( Man I wish I was a Tech and speak the language )

The Pre master volume had a 250K instead of 1Meg so he changed it to the right value.
Anyway to make a long story short , my tech Denis Rozon will draw a loop circuit board to match the holes drilled
on the amp , the two knobs will become small toggle switches , one for +4 / -10 db and one on-off.
He did a few tweaks and now the amp is quietier than before and behaves better with the loop disconnected ,
the right pot value for the master volume and a nice quad of KT66's. Even though he is surprised on how good the amp sounds now ,
he is not sure about the quality of the transformers and said that he often replaced those orange caps for leakage so he thinks there not
too good, apart from that , the amp has wonderful cleans and growls when you tweak knobs.
 

_Steve

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Hi Neil, finally had my tech install a matched quad of Gold Lions and the amp sounds pretty good , he told me
that the previous tech who install the London Power effects loop didn't know what he was doing , it was connected before or after something and was
the wrong way to do but don't remember what he meant , he also said that because it was a tube buffered loop , it was installed
at the wrong place in the chassis because it was interfering and making noise , ( Man I wish I was a Tech and speak the language )

The Pre master volume had a 250K instead of 1Meg so he changed it to the right value.
Anyway to make a long story short , my tech Denis Rozon will draw a loop circuit board to match the holes drilled
on the amp , the two knobs will become small toggle switches , one for +4 / -10 db and one on-off.
He did a few tweaks and now the amp is quietier than before and behaves better with the loop disconnected ,
the right pot value for the master volume and a nice quad of KT66's. Even though he is surprised on how good the amp sounds now ,
he is not sure about the quality of the transformers and said that he often replaced those orange caps for leakage so he thinks there not
too good, apart from that , the amp has wonderful cleans and growls when you tweak knobs.

FWIW I found the Gold Lions (you got new production I assume) really squishy in my 45/100. Fine if you are going for that EVH thing but personally I hated them. I really like the JJ KT66s in mine. YMMV.

Congrats on the 45/100! I hope you love it as much as I love mine.
 

Kelia

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FWIW I found the Gold Lions (you got new production I assume) really squishy in my 45/100. Fine if you are going for that EVH thing but personally I hated them. I really like the JJ KT66s in mine. YMMV.

Congrats on the 45/100! I hope you love it as much as I love mine.
Thanks for the input , I have four nice Gec's here but they are not matched , would be nice to have them in !
 

_Steve

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Thanks for the input , I have four nice Gec's here but they are not matched , would be nice to have them in !

Throw 'em in! Unmatched isn't as big a deal as people make out. If you really want, you could match them into two pairs so that the combined current of each pair (ie each side of the output tranny) is similar.

Vacuum tubes are super tolerant. You were just running EL34s at TWICE their design impedance and it sounded great!
 

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