Marshall DSL40CR arrived, is this correct?

[Mikelamury]

This amp is advertised as having 4 tubes in the preamp and 2 in the power amp. But as I was looking in the back of the amp I can only see a total of 3 preamp tubes and 2 power amp tubes. The spot where the fourth tube would go has a metal piece coming out of it that doesn't look like it has a tube inside. I'll try to get some pics. Do your see 3 or 4 preamp tubes? Check out this new gretsch I just got too!

 

[Ewizard]

That si 100% normal and correct. That tube with the metal shroud on it is the V1 first stage tube. Your amp only has two power tubes and it appears to have 4 preamp tubes.

 

[Mikelamury]

That si 100% normal and correct. That tube with the metal shroud on it is the V1 first stage tube. Your amp only has two power tubes and it appears to have 4 preamp tubes.

Ok thanks, my first tube amp and didn't know what to expect. Glad it's all good. Thank you for the help

 

[Top-L]

That metal cap can be screwed off to reveal the tube underneath. I believe it is to shield the tube from noise, electrical and mechanical.

 

[Mikelamury]

That metal cap can be screwed off to reveal the tube underneath. I believe it is to shield the tube from noise, electrical and mechanical.

Ok it doesn't even look like it has anything inside of it. Is the tube sticking up into the amp?

 

[dave74]

No it's the same as the others. Just has the shield on top to reduce noise. To remove (if ever needed) you just push down gently then rotate about 1/4th turn and it will pop-up from the spring tension. To put it back on just push down and rotate again.

It's kind of like opening a pill bottle from the pharmacy.

OK, looking again these might just screw on and off like a normal screw,,,,,,,,,,on my mesa stuff they are always spring-loaded.

 

[Top-L]

Ok it doesn't even look like it has anything inside of it. Is the tube sticking up into the amp?

Well, its possible there isn't a tube in there. Not clear from the picture.

You could take a pencil (eraser end) and probe to see if you can touch the tip of the tube. It should go to the same height as the others without caps.

 

[Obsessive Compulsive]

Nice. I love tubes...lol.

Looks like it's spring loaded cause I see that little thing on the side. Be careful when you put the cap back on, you might crack the top open.

Aren't all preamp tubes supposed to be shielded? The cans are there to thwart electromagnetic interference or so they say...

 

[beaubrummels]

Just unscrew the cover and take a look. Harmless. I'm sure it's like Top-L and dave74 said. The side view shows that cover is twice as tall as the other 12A?7 type tubes poking up. It easily has a similar tube under there. Just take a look then put the cover back. My SL-X came with covers on all 4 pre amp tubes.

 

[Obsessive Compulsive]

I think can see the top of the tube inside the can. If it's empty you will see the socket.

 

[JMP/HBE]

*predict "help my amp doesn't work" thread by the end of next week.

 

[Mikelamury]

Well, its possible there isn't a tube in there. Not clear from the picture.

You could take a pencil (eraser end) and probe to see if you can touch the tip of the tube. It should go to the same height as the others without caps.

Confirmed with a pencil there is a tube in there... I don't know why I was worried about my new amp not having a tube in it but...it's settled. I'm now never removing the back again until it's time to change tubes because I've already got JMP jinxing me and I'm definitely not going to mess this amp up. Thanks to everyone for the info and advice.

 

[Ewizard]

The metal ( aluminum ) shield is to reduce RF noise and help stabilize the tube ( so it doesn't rattle ). It can also be used as a way to take a little bit of edge off the tube's sound. The shield is grounded and interacts with the tube like a capacitor. The added capacitance the shield provides can roll off some of the highs. Perhaps not as noticeable when there is only one shield, but more so when there are shields on all of the preamp tubes.

 

[ErikH]

My Marshall JCM 900 MkIII 2100 head the shield on all the preamp tubes and the phase inverter. They simply twist and come off and have a spring on them to hold tension when twisted and in place over the tube. The other 3 have a hard rubber grommet to keep them from rattling and keep them snug. Not uncommon to see. Those should last a very long time anyway.

In the second picture, the tube at the upper left, away from the others, I believe is the phase inverter, and is actually part of the power amp section. Yes, it's a pre-amp type type, but serves a different purpose than the other 3, which are the gain and recovery stages.

It's never a bad idea to learn how tube amps work.

 

[Obsessive Compulsive]

My Marshall JCM 900 MkIII 2100 head the shield on all the preamp tubes and the phase inverter. They simply twist and come off and have a spring on them to hold tension when twisted and in place over the tube. The other 3 have a hard rubber grommet to keep them from rattling and keep them snug. Not uncommon to see. Those should last a very long time anyway.

In the second picture, the tube at the upper left, away from the others, I believe is the phase inverter, and is actually part of the power amp section. Yes, it's a pre-amp type type, but serves a different purpose than the other 3, which are the gain and recovery stages.

It's never a bad idea to learn how tube amps work.

How does it work? The phase inverter preamp tube is V1 I think on my Ironheart. It's closest to the volume knob, a different brand from the other three.

 

[ErikH]

How does it work? The phase inverter preamp tube is V1 I think on my Ironheart. It's closest to the volume knob, a different brand from the other three.

Umm, no. V1 will not be the phase inverter in any amp. The phase inverter literally lives in the power amp section. It splits the signal from the preamp in to two different AC signals of opposing phase to each other. This gives a good explanation and diagrams. Now, in the diagrams, the "signal from guitar" is what is coming from the preamp, and after the tone stack.

https://www.mojotone.com/blog/what-does-this-thing-do-phase-inverter

There is no rule that says that V1 needs to be the same brand as the others. In fact, none of them need to be the same. It may be that way because that is what works best in that specific amp. Most people use the same in all positions because that's what's been done over the years. But, it's also not uncommon to use something different and even lower gain in V1, like a 12AU7 or 12AY7, regardless of brand.

 

[Aceman]

Dude....deep breath's.

When you plugged it in and turned it on did it power up?
Did sound come out of it when you played?

If yes, rock out, and enjoy. It's fine. No need to futz, fidget, and fiddle with it.


It's an amplifier, not a Ferrari. It doesn't need all tuned up and checked out all the time unless it doesn't sound good or right. Plug in and experiment with everything on the front, except turning the master volume up to 10, and you'll be fine. And even that will probably be fine for a while unless you are slamming it with something really loud/hot.

 

[solspirit]

You bought it new, right? You should expect it to be fine for a while. No harm in reading up on how it works and preventive maintenance and whatnot, but don’t forget to play it.

Instructions and manuals
pfft. . . .

 

[Mikelamury]

Dude....deep breath's.

When you plugged it in and turned it on did it power up?
Did sound come out of it when you played?

If yes, rock out, and enjoy. It's fine. No need to futz, fidget, and fiddle with it.


It's an amplifier, not a Ferrari. It doesn't need all tuned up and checked out all the time unless it doesn't sound good or right. Plug in and experiment with everything on the front, except turning the master volume up to 10, and you'll be fine. And even that will probably be fine for a while unless you are slamming it with something really loud/hot.

I get it. I've got a good EQ going with the gain on 8. I can't put the master volume past 1 so it's LOUD. I know where I'm going to put my pedals. I was just being cautious I guess but nevertheless thanks for the feedback and I pleased to announce the amp Is sounding great. Thanks again to everyone.

 

[Top-L]

I get it. I've got a good EQ going with the gain on 8. I can't put the master volume past 1 so it's LOUD. I know where I'm going to put my pedals. I was just being cautious I guess but nevertheless thanks for the feedback and I pleased to announce the amp Is sounding great. Thanks again to everyone.

If you want to get more range out of the volume knob, if the FX loop does not have adjustable level, is put a pedal in there that cuts the level. Most pedals with level at noon is unity gain, so you can reduce output. EQ pedal is good candidate for this as its always on.