#1
So I for example have a JCM 2000, and I am aware it is a 2 channel amp, fundamentally, does this mean the amp has 2 channels of amplification inside it? IE, it has 4 preamp tubes, so are there 2 preamp tubes for one channel and 2 preamp tubes for the other? and when you switch the channels it switches the sets of tubes/pots it runs through? Or do both channels run the guitar signal through ALL 4 preamp tubes and power tubes? 

I can't find any information out there, kinda trivial but I'm curious
#2
A two channel amp means you have 2 separate preamps with separate tubes for the separate gain stages on preamps.  The preamp valves function like 2 valves in 1 peice of glass so sometimes 2 channels with shair 1 valve but they will use separate sides of the same valve but I'm 99% sure the JCM 2000 doesn't do that.
Not taking any online orders.
#4
Yup.  The two channels will feed into the same phase inverter which sends the signal to the single power section
Not taking any online orders.
Last edited by CorduroyEW at Jun 14, 2017,
#5
that's not what it always means but for that amp yes. 
Some stages are shared, i think the first input stage and then the effects loop stages and phase inverter. 
Jumping on dat gear sig train.
PRS Hollowbody II / BKP Warpigs
Strandberg OS6T / BKP Aftermath
Strandberg OS7 / Lace Poopsticks
Skervesen Raptor 7FF / BKP Warpigs
Skervesen Raptor 6 NTB / BKP Juggernauts
Hapas Sludge 7 FF / Hapas Leviathan
Anderson Baritom / Motorcity Nuke BKP Sinner Anderson H2+
Warmoth Baritone / BKP Piledriver
Ibanez Rg2120x / BKP Nailbomb

Blackstar ID:Core Beam
#6
Quote by CorduroyEW
A two channel amp means you have 2 separate preamps with separate tubes for the separate gain stages on preamps.  The preamp valves function like 2 valves in 1 peice of glass so sometimes 2 channels with shair 1 valve but they will use separate sides of the same valve but I'm 99% sure the JCM 2000 doesn't do that.

We may want to get a tube amp innards expert to weigh in on this; I'm pretty sure that all channels can share all preamp tubes (not that they do, necessarily). 
I have a four channel preamp with nine preamp tubes (12 AX7s) that features up to eleven gain stages, depending on the channel. It adds gain stages as required, but several of the preamp tubes are shared and always used, no matter what channel is selected.
#7
Quote by dspellman
We may want to get a tube amp innards expert to weigh in on this; I'm pretty sure that all channels can share all preamp tubes (not that they do, necessarily).
I have a four channel preamp with nine preamp tubes (12 AX7s) that features up to eleven gain stages, depending on the channel. It adds gain stages as required, but several of the preamp tubes are shared and always used, no matter what channel is selected.


it depends entirely on the amp and the designer really...
how technically savvy the designer is and how much switching and stuff they are willing to do.
Jumping on dat gear sig train.
PRS Hollowbody II / BKP Warpigs
Strandberg OS6T / BKP Aftermath
Strandberg OS7 / Lace Poopsticks
Skervesen Raptor 7FF / BKP Warpigs
Skervesen Raptor 6 NTB / BKP Juggernauts
Hapas Sludge 7 FF / Hapas Leviathan
Anderson Baritom / Motorcity Nuke BKP Sinner Anderson H2+
Warmoth Baritone / BKP Piledriver
Ibanez Rg2120x / BKP Nailbomb

Blackstar ID:Core Beam
#9
Look at the circuit diagram to see the configuration of an amplifier. If you can't read the diagram, and you want to know about them, then I suggest you learn to do so. 

https://elektrotanya.com/marshall_jcm2000_tsl60_60w.pdf/download.html

Now, would someone please point out to me this "phase inverter" because I don't believe there is one between the preamps and the power amp.
Last edited by PSimonR at Jun 14, 2017,
#10
Quote by AcousticMirror
that's not what it always means but for that amp yes. 
Some stages are shared, i think the first input stage and then the effects loop stages and phase inverter. 

Actually yeah I answered too quickly and didn't check what I had wrote.  I had one way of explaining it in mind and then started a new thought without properly editing my original. Manny will share the 1st gain stage before they split into separate channels and things like reverb and FX loops are often shared too.
Not taking any online orders.
Last edited by CorduroyEW at Jun 14, 2017,
#11
PSimonR Should be V4?

karniboy98 Typically there will be some tubes shared between the channels, not completely different sets of tubes for each channel. An example of the typical VOX AC30: Channel 1 takes up half of V1, then goes to the PI which is V3, and then to the power tubes V4-V7. However, Channel 2 takes up the other half of V1, all of V2, and then to V3 and then the power tubes IIRC.

I often see V1 shared between a two-channel amp. But it does depend on the builder. For instance, you could just wire in multiple tone stacks, give them all knobs and a button to engage them, but use the exact same preamp tubes, and still technically have a multi-channel amp. I think.
Last edited by Will Lane at Jun 14, 2017,
#12
Will Lane good information....

How about marshal amps? Specifically the JVM...i think the previous user was right that the JCM has 2 dedicated channels with independent preamp tubes, but what about the JVM? I forgot but I think it has like a total of 9 channels?