The Official Marshall DSL40c Information Thread

[MarshallDog]

As always, sounds good Mitch! Like the Gibson T also!!!

 

[Mitchell Pearrow]

As always, sounds good Mitch! Like the Gibson T also!!!

I thank you brother, thought it was fitting for the song!

 

[Patrick1959]

Just trash it not worth the time and money to get it repaired in my experience!!

Thanks, done.

 

[KraftyBob]

Thanks, done.

As MarshallDog said, not worth it. I was going to to try and re-cone the speakers (had two bad V30’s) myself just to learn how to do it, but it wasn’t worth the cost of the supplies I’d have to buy. Then I checked into a guy about an hour away and he wanted $45 each to re-cone. Probably not a bad deal if I really wanted these speakers but since I’m not a fan of V30’s my plan would be to then sell them. Add my time, gas and the fact that I’d have to sell them cheap since they were re-coned it was not worth it.

They are still sitting in my basement. I have a friend that might be interested in getting them re-coned so I’ll just give them to him. Otherwise I’ll likely toss mine too.

Good to see Amazon did right and refunded your money.

 

[Bownse]

Just trash it not worth the time and money to get it repaired in my experience!!

Or scrap it for parts. Those magnets are great!

 

[Micky]

Or scrap it for parts. Those magnets are great!

Agreed. Unless of course you want to re-cone it...

 

[Patrick1959]

I did salvage the magnet from the speaker. I also ordered a replacement V 30 from Mesa Boogie. They sell UK made Celestion speakers. The speaker I trashed was made in China. Not sure that has anything to do with anything, but had I known before hand, I would have bought from the Ipswich location. It arrived today and it will be Monday before I can put it in the amp. Maybe this one will work. Cheers!

 

[CincyPaul]

Big riffin' this morning with some fuzz, a strat, and a Marshall DSL40x:

 

[Exojam]

I have been the amp recently and had been meaning to check the bias on this one since I had not after the last modification I made for the 6550 power tubes.

Needless to say I am glad I did as one had drifted by 8-10ma.

I had a plate voltage of 427 so my original bias was on the cool side so this time I went up to 60ma. I left the amp on for a few hours and it stayed solid so I decided that was enough time.

Right now I am going through all my preamp tubes to decide what I want in there. I will decide that tomorrow and update this and see how it sounds.

No big rush since I am putting new strings on the Gothic SG.

 

[Micky]

I set mine at 50 and haven't checked it in a while...

 

[Exojam]

That is what I had originally set mine to but I checked a bias calculator and for the tubes I have and the plate voltage I read, 60 was right in the middle so I figured I would give it a try.

 

[cspencer]

I have gone over this before, and in some other threads as well, I wish I could find the reference to that particular post in this thread. No way am I gonna sift thru almost 300 pages of posts... So here goes:

You need to remember that preamp tubes (most of them) such as the 12AX aeries are actually 2 tubes in one glass envelope.

Also, the DSL40c is a 2-channel amp, with 2 'modes' for each channel, effectively giving 4 different voices.

V1a is the input buffer for both channels of the amp. V1b is the first gain stage of the Ultra Channel. V1B is bypassed for the Classic channel.
V2 is strictly a cascaded gain stage tube, the output of V1 feeds V2a, and that output feeds V2b. This is essentially the difference between Classic and Ultra, Classic goes V1a->V2a->V2b and Ultra goes from V1a->V1b->V2a->V2b. Follow me so far?

From V2 onward, both channels go thru basically the same path, with only slight variations.

V3 is what some call the 'tone stack' as the EQ controls are located right after the circuitry of this tube. It essentially is yet another 2 gain stages, as the output from V2b feeds V3a, which in turn feeds V3b. The EQ controls come next, and then the reverb circuitry. After this is the Master Volume (MV) for each channel. Yhen, just before V4 is the FX Send and Return.

V4 is actually NOT a preamp tube, it is part of the power section. Commonly referred to a the Phase Inverter (PI) it is what allows the signal from the preamp to push the power tubes in a Class A/B (Push-Pull) operation. It splits the signal into 2, and then flips one side out of phase to feed the finals.

I know there may be inaccuracies in this long-winded reply, so deal with it. It is an explanation for the majority of us... In all reality, I think I did a much better job earlier on in the thread. Maybe someone can find it and PermaLink it here.

Hi Micky,

Following up on this post.

If V1b is activated by the ultra channel, then shouldn't V1 be equipped with a tube that has better compression/dstortion? Other Marshalls seem to use V2 as their ultra channel and better compresstion tubes are recommended there; cleaner tubes are recommended for V1.

Has Marshall changed its ultra channel in the DSL40CR to V1b and the rest of the tubes, including V2, are cascading channels? I hope my reasoning is correct. Your comments are always informative and is really appreciated.

Thank you.

 

[Micky]

I can follow up on this tomorrow...

 

[Lukas]

Has anyone experimented with different preamp tubes in these?

I used the factory tubes for about a month then installed 2 matched SVETLANA EL34’s power tubes and a tungsol preamp tube in V1, preffered series 7025 in V2, EH in V3, and another preffered series 7025 in V4. Can’t say I notice to much of a difference. The Marshall branded JJ’s that my 40CR came with actually sounded damn good, they are newer spares now. I did this mainly because the SVETLANAS sound absolute killer in my JVM and thought I’d try them in the DSL 40CR. Also I wanted to know how to bias this amp as I do that myself also. This amp was biased on the cooler side at 30mv. I did a bunch of reading before hand and biased mine at around 36-37mv. Some info I could not find was pics measuring the screen and plate voltage and where to do that & and actually calculate this properly. I tried a higher mv setting than stock and played it and it sounded great and just left it there, that was about 6 months ago and it still sounds killer. I’m assuming the preamp locations and functions are the same as a JVM? V1 & 2 being gain stages and 3 effects loop etc? I hope so cause that’s what swayed my decision on tube placement. But once again couldn’t find any damn info on this. I will add that I think perhaps the 40C differs in biasing as you need to remove the head from the cab to access the trim pots where the 40CR the trim pots and probing pins are on the outside just behind the screen. No need to remove anything but the back screen to access them. I could be wrong tho as I have a 40CR and not a 40C.

 

[cspencer]

I can follow up on this tomorrow...

Hi Micky,
I'm not sure if this video has been posted here or not. Check out the the first part where he looks inside and describes how the circuit board works.

 

[Micky]

First, I wouldn't depend on this guy to explain anything.
It's obvious he is guessing about a lot of the stuff he is pointing out.
He really has no clue about what is what, calling relays 'solid state' and ic's 'brain'.
The real indicator that he is clueless is that the TubeStore told him to use JJ's and he believed them.

First of all, the preamp in the 40c and the 40cr is virtually identical.
Except for the controls (master volumes, etc.) the component values are almost the same.
There are a couple slight value changes in the coupling cap RC circuit on the output of V1b but it doesn't really affect tone.

To address your post, V1b is not 'activated' by the Ultra channel.
V1b is 'bypassed' in the Classic channel.
The important thing to remember is that V1a is the input buffer, and lo-noise is what you are after.
'Clean' so to speak is more a lack of gain as far as I am concerned more than anything else.
If clean is what you really want, then a 12AT7 or 12AY7 would be better served.
(the DSL was designed for 12AX7's in the preamp section)

Everything after V1a is amplified further down the circuit, so a noisy tube here will just add needless noise further down the line. Higher gain tubes tend to have more noise, so it is a very fine balance to find a tube that has the proper amount of gain as well as lo-noise. As far as Current Production (CP) tubes are concerned, a 7025 works well here.

V2 is just a cascaded gain stage in both channels. This needs to be a heavier-duty tube in order to handle the higher voltages. V3 is the tone stack and V4 is the Phase Inverter (PI) which is actually part of the Power Amplifier section. The master volumes sit between the tone stack and the power section, as does the FX loop and reverb.

On the 40cr, the board that is mounted perpendicular to the motherboard is the digital reverb. It is obvious from the A/D chip that this bozo in the video calls the 'brain'. On the 40c the board is mounted parallel to the motherboard and covers the IC that controls switching.

To address the last part of your post, the 40c and 40cr are virtually identical in their layout as far as the preamp section is concerned. There are a couple slight value changes but their operational signal path thru to the PA is the same. Marshall hasn't really changed much of anything...

 

[cspencer]

First, I wouldn't depend on this guy to explain anything.
It's obvious he is guessing about a lot of the stuff he is pointing out.
He really has no clue about what is what, calling relays 'solid state' and ic's 'brain'.
The real indicator that he is clueless is that the TubeStore told him to use JJ's and he believed them.

First of all, the preamp in the 40c and the 40cr is virtually identical.
Except for the controls (master volumes, etc.) the component values are almost the same.
There are a couple slight value changes in the coupling cap RC circuit on the output of V1b but it doesn't really affect tone.

To address your post, V1b is not 'activated' by the Ultra channel.
V1b is 'bypassed' in the Classic channel.
The important thing to remember is that V1a is the input buffer, and lo-noise is what you are after.
'Clean' so to speak is more a lack of gain as far as I am concerned more than anything else.
If clean is what you really want, then a 12AT7 or 12AY7 would be better served.
(the DSL was designed for 12AX7's in the preamp section)

Everything after V1a is amplified further down the circuit, so a noisy tube here will just add needless noise further down the line. Higher gain tubes tend to have more noise, so it is a very fine balance to find a tube that has the proper amount of gain as well as lo-noise. As far as Current Production (CP) tubes are concerned, a 7025 works well here.

V2 is just a cascaded gain stage in both channels. This needs to be a heavier-duty tube in order to handle the higher voltages. V3 is the tone stack and V4 is the Phase Inverter (PI) which is actually part of the Power Amplifier section. The master volumes sit between the tone stack and the power section, as does the FX loop and reverb.

On the 40cr, the board that is mounted perpendicular to the motherboard is the digital reverb. It is obvious from the A/D chip that this bozo in the video calls the 'brain'. On the 40c the board is mounted parallel to the motherboard and covers the IC that controls switching.

To address the last part of your post, the 40c and 40cr are virtually identical in their layout as far as the preamp section is concerned. There are a couple slight value changes but their operational signal path thru to the PA is the same. Marshall hasn't really changed much of anything...

Hi Micky,
I was wondering too why he used words like IC's and brains. Hilarious.

Thanks for your reply. It answers a lot of questions. I get it now, when you say V1b is bypassed in classic channel (Edit) as opposed to activated by ultra channel (/Edit). That makes a lot of sense and it helps me understand the circuit.

I've tried tubes in V1 and didn't really like them. It ranged from Mullard M8137, Brimar CV4004, to I62, f92 and more. In the end I preferred I63's and really loved one that's lopsided 100%/125%. I also like a Heerlen I65 that tested 60/65 (32 is 65%).

I've understood V3 and V4 from earlier posts so I won't repeat them here.

 

[krb813]

Can someone recommend a good bias level for the DSL40CR. I'm getting ready to check it.

Thanks

 

[cspencer]

Can someone recommend a good bias level for the DSL40CR. I'm getting ready to check it.

Thanks

34. It also depends on what tubes your using. I've biased it at 36 for a long time but now prefer a less nasally sound at 34.

 

[Jon C]

@Micky …… Hi there …… Do you happen to know the value of the Treble Bleed Cap for the Ultra Gain Channel in the DSL40CR ?