The Official Marshall DSL40c Information Thread

[solarburn]

I have a bias probe but don't use it with the Marshall, since I have the chassis out I just use Marshalls test points.

The DSL50 has the bias pots outside with the test points. Wonder why Marshall opted to put the bias pots inside so the chassis needs pulling... I was disappointed with that. It was an easy check if you wanted to see where your power tubes were after a tube change. I liked checking them a few times after playing a few sessions and as they get hours on them.

 

[frankyfal]

lol I did the same thing I had 2 of them fall out!

I remember. It was your post and pic that showed me how.

 

[J.LaGrassa]

The DSL50 has the bias pots outside with the test points. Wonder why Marshall opted to put the bias pots inside so the chassis needs pulling... I was disappointed with that. It was an easy check if you wanted to see where your power tubes were after a tube change. I liked checking them a few times after playing a few sessions and as they get hours on them.

Yeah I rember that from when i had the DSL50 definitely a lot more convenient.

 

[Swede]

Swede do you notice a sound difference with the new power tubes??

Hopefully the next new amp I buy will have bias test points and a potentiometer easily accessible on the back panel. Even better. A digital display next to the pot with an on off switch so you can see the voltage when needed and just slip a small screwdriver in and adjust.

I honestly dont know....It sounds GREAT, but better, Im not sure. When I changed tubes in my plexi I could tell pretty easy it got better, granted I changed from 6CA7's to EL34's so maybe that is slightly more of a difference.

 

[ken361]

Rocked out the DSL at my girls condo,it kicks ass and roars.

 

[USAPatriot]

The DSL50 has the bias pots outside with the test points. Wonder why Marshall opted to put the bias pots inside so the chassis needs pulling... I was disappointed with that. It was an easy check if you wanted to see where your power tubes were after a tube change. I liked checking them a few times after playing a few sessions and as they get hours on them.

Being able to check the PV and adjust bias externally is nice and convenient but I suspect that amp makers also look at it as a liability issue. I'd like to externalize it all on my DSL40C, for sure, but also recognize that it's another potential hazard. -Rod-

 

[Micky]

Being able to check the PV and adjust bias externally is nice and convenient but I suspect that amp makers also look at it as a liability issue. I'd like to externalize it all on my DSL40C, for sure, but also recognize that it's another potential hazard. -Rod-

If done properly it is actually much safer. There was someone here that did it, and it looked professional to me...

Think abut it - You have millivolts on a connector on the back panel. You have 2 locking trimpots there as well.

There is no need to remove the chassis so the potential for electrical hazard is minimized, and the wear and tear on the nuts bolts and other stuff is gone. Plus, you don't risk damaging anything on the chassis because you aren't removing it.

I would love to do it to ALL my amps...

 

[jimmyjames]

I'm considering getting this done,+ Ultra 1 mods, to my 15H

 

[Skylarkpilot]

Hi Guys,
I know we've been around the block a few times on the subject of bias but.....
Today I actually had loads of time on my hands so I was doing a re-bias and swapping some tubes around. I use the same TAD EL34Bstr tubes as Micky but I noticed over the space of about an hour my PV was slowly changing between around 425 at the lowest and 440 at the top end. Is this down to wall voltage variation do you think, or should I be looking a bit deeper into the beast ?

 

[USAPatriot]

If done properly it is actually much safer. There was someone here that did it, and it looked professional to me...

Think abut it - You have millivolts on a connector on the back panel. You have 2 locking trimpots there as well.

There is no need to remove the chassis so the potential for electrical hazard is minimized, and the wear and tear on the nuts bolts and other stuff is gone. Plus, you don't risk damaging anything on the chassis because you aren't removing it.

I would love to do it to ALL my amps...

I remember seeing that pic and it was great work. I wish I knew where it was. I knew I should have saved it. But...externalizing the PV isn't the same as just having bias pots out there with a few dozen mV. It's 400+ volts and just too accessible to people that maybe shouldn't have access to it, be they inexperienced owners, snoopy relatives or a dog sniffing around. *I* wouldn't have a problem with it but ya can't say that's universal. Pulling a chassis is like handling rattlesnakes...we know the hazard is there. An innocuous set of sockets on the back of an amp...some people will be unaware of the hazards, even if they have no business with their nose back there. Just sayin' -Rod-

 

[USAPatriot]

Hi Guys,
I know we've been around the block a few times on the subject of bias but.....
Today I actually had loads of time on my hands so I was doing a re-bias and swapping some tubes around. I use the same TAD EL34Bstr tubes as Micky but I noticed over the space of about an hour my PV was slowly changing between around 425 at the lowest and 440 at the top end. Is this down to wall voltage variation do you think, or should I be looking a bit deeper into the beast ?

Did you check the wall voltage? If you live in an older area and if heaters are running in the cold, your voltage could definitely be pulled down or let back up. I'd redo it and chart the voltage at the plate while also checking the voltage at the wall. It should be easy to spot a correlation. You expect some variation over time but 15V in an hour seems a bit much, at least in my house. If your oven or furnace is on the same circuit, you could be doing it to yourself too. I'd look into that before I looked deeper into the amp. -Rod-

 

[rpinon69]

Hello

Just got a deal on a Eminence CV-75 on eBay but it is 8 ohm!

Just to make sure after installing all I have to do is connect it to one of the 8 ohm inputs, which I assume are for a multijack cabinet in stereo or two separate cabinets. Is this correct?

Thanks Guys!

 

[Micky]

Hello

Just got a deal on a Eminence CV-75 on eBay but it is 8 ohm!

Just to make sure after installing all I have to do is connect it to one of the 8 ohm inputs, which I assume are for a multijack cabinet in stereo or two separate cabinets. Is this correct?

Thanks Guys!

Yes.

 

[Micky]

I remember seeing that pic and it was great work. I wish I knew where it was. I knew I should have saved it. But...externalizing the PV isn't the same as just having bias pots out there with a few dozen mV. It's 400+ volts and just too accessible to people that maybe shouldn't have access to it, be they inexperienced owners, snoopy relatives or a dog sniffing around. *I* wouldn't have a problem with it but ya can't say that's universal. Pulling a chassis is like handling rattlesnakes...we know the hazard is there. An innocuous set of sockets on the back of an amp...some people will be unaware of the hazards, even if they have no business with their nose back there. Just sayin' -Rod-

No need to bring that voltage to the back panel.
It is not like it changes enough to have to re-calc the bias.

Measure it once. Figure your bias range. Set the bias in that range.

This isn't rocket science...

 

[rpinon69]

Yes.

Thank you!

 

[manofsteel2397]

Anybody experience a speaker thumping sound when cranked up is this normal thinking I have two much bass in the eq or have a bad amp I do have the 65 creamback upgrade from Sweetwater

 

[rpinon69]

No need to bring that voltage to the back panel.
It is not like it changes enough to have to re-calc the bias.

Measure it once. Figure your bias range. Set the bias in that range.

This isn't rocket science...

http://www.marshallforum.com/marsha...dsl40c-information-thread-67.html#post1140306

Is this the post?#1984

 

[rodd]

http://www.marshallforum.com/marsha...dsl40c-information-thread-67.html#post1140306

Is this the post?#1984

Is it possible to shift the external testpoints and trimpots inside the cab so access is after taking the back panel off. Otherwise I'd like that mod done to mine .

 

[chheww]

Does anyone know if the classic gain and ultra gain are opposite polarities/phase?

 

[rodd]

Can we drill holes into the bottom of the chassis and pcb board to access the trimpot adjustments