Tubes to change ....

[DesertRose]

Hi

I'm due for tube change.
I don't believe that all 5 pre amp tubes gives you the best of sounds.

i just need to know which ones to change which will affect the clean channel.
I'm using a JCM800 combo, 50 watts, reverb.

The picture is as such taken from the top:

From right to left, my gut feel is to change just the 1st 3 from right to left.
I never touch channel 2 (OD) at all.

Any advise?
thanks

 

[tonefreak1527]

Re: Tubes to change ....

Change 1,3,and the phase inverter and power tubes

 

[Brown Note]

Re: Tubes to change ....

try either an at7 or au7 as the first tube from the right. For completely clean sound neither the powertubes nor the phase inverter makes a lot of difference.

 

[Jeff_H]

Re: Tubes to change ....

Pre-amp tubes are cheap enough to experiment with a new one in every position. For new tubes I like the GT-12AX7-C. Grove tubes makes several different types. The Mullard reissues are good as well. V1 position usually makes the largest difference in tone, along with the PI position, IMHO. Get a couple of new tubes and start one at a time changing the tubes and see how you like the tone. It won't take you long to figure out what sounds best to you.

For power tubes, I like the SED Winged C's. If you like a slightly darker tone, JJ's are a good choice.

 

[DesertRose]

Re: Tubes to change ....

Hi guys

thanks for the input.
I will scout around.

Yeah I've just stuffed in a pair of SEDs. Sounds great, no regrets.

How about tungsol 12AX7? Any users?
I could try the AU7 or AT7 ... i think i have some of them around in my storeroom

 

[Ascension]

Re: Tubes to change ....

Hi guys

thanks for the input.
I will scout around.

Yeah I've just stuffed in a pair of SEDs. Sounds great, no regrets.

How about tungsol 12AX7? Any users?
I could try the AU7 or AT7 ... i think i have some of them around in my storeroom

Yep on the Tungsol 12AX7's. IMO they are the best of the new production 12AX7's right now. I have a set in my Zinky. All my NOS tubes were too microphonic in that circuit at volume in the combo but the TungSols were dead quiet. Nice fat and big sounding.

 

[zzmoore]

Re: Tubes to change ....

Kind of a crazy schematic.....
This is one of those single input, "split channel", reverb amps?
I agree with what has been said already. TungSol AX7 in V1 and V3. If you have an AT7, I would definitely drop that in the PI (V5). Sounds like you have a good set of power tubes. SED is about as good as it gets for modern day stuff.
Careful with V2. Those TungSols do not last long in a cathode follower. But maybe you do not use the "Boost" anyway.
Nice speaker By The way.......
Good Luck

 

[DesertRose]

Re: Tubes to change ....

Yep on the Tungsol 12AX7's. IMO they are the best of the new production 12AX7's right now. I have a set in my Zinky. All my NOS tubes were too microphonic in that circuit at volume in the combo but the TungSols were dead quiet. Nice fat and big sounding.

Thanks for the recommendations.
As what was mentioned, preamp tubes are cheap enough to be experimented.
I will try starting with the tungsols ... then prolly Mullards ... etc .... shuguang ...

Kind of a crazy schematic.....
This is one of those single input, "split channel", reverb amps?
I agree with what has been said already. TungSol AX7 in V1 and V3. If you have an AT7, I would definitely drop that in the PI (V5). Sounds like you have a good set of power tubes. SED is about as good as it gets for modern day stuff.
Careful with V2. Those TungSols do not last long in a cathode follower. But maybe you do not use the "Boost" anyway.
Nice speaker By The way.......
Good Luck

Yeah, split channel reverb.
I'll experiment on the tungsol.

By the way, what does the phase inverter (V5) do?
Any of the Vs has a relation with the reverb?
Need some enlightenment here.

thanks

 

[zzmoore]

Re: Tubes to change ....

Looks like the reverb involves half of V3 and both sides of V4.
Phase Inverter does kind of just what it says. For a push-pull amp, it splits the signal into two equal signals that are 180 degrees out of phase. The OT combines the phase after it is amplified, and it also attempts to match the impedance of the speaker(s) with the impedance of the power tubes for optimum performance. It is more complex than that of course, but that is the basics.....
Good Luck

 

[Andrew Lamprecht]

Re: Tubes to change ....

From right to left, my gut feel is to change just the 1st 3 from right to left.
I never touch channel 2 (OD) at all.

Any advise?
thanks

WAIT! You have a JCM800 and you don't use the OD?????? Banned I say! Banneded!!!!!

 

[DesertRose]

Re: Tubes to change ....

Looks like the reverb involves half of V3 and both sides of V4.
Phase Inverter does kind of just what it says. For a push-pull amp, it splits the signal into two equal signals that are 180 degrees out of phase. The OT combines the phase after it is amplified, and it also attempts to match the impedance of the speaker(s) with the impedance of the power tubes for optimum performance. It is more complex than that of course, but that is the basics.....
Good Luck

I see.
sounds very technical here.
Haha .. thanks bro.
I'll just try a AU/AT7 on V5 and check it out.
Sometimes volume is failing ... maybe its the phase inverter.

WAIT! You have a JCM800 and you don't use the OD?????? Banned I say! Banneded!!!!!

haha .. sorry to break your heart bro.
Sadly to say that the treble, bass and Mid pots are toasted for the OD channel.
Needed immediate replacement.
Its kindda tedious to change those, which I did it before on the other amps.
So KIV until further notice.