Marshall Dsl40cr Bias?

[Djmindtrip]

Mine has 406v plate voltage very surprised this low anywho i rebiased to 40mv @ 65%

 

[Djmindtrip]

full power and half power makes the different reading.

 

[tschrama]

a good sounding bias current is only related to tube type, and not related to plate voltage..

Hence the 70% myth is BS

 

[cspencer]

a good sounding bias current is only related to tube type, and not related to plate voltage..

Hence the 70% myth is BS

+1
I have a pair of NOS Siemens and they sounded great at 34mV. Another pair of Mullard XF2 sounded great at 38mV. Factory Tung Sol EL34II sounded great at 34mV. Russian Mullard sounded great at 35mV. Dunno.

 

[slingblade]

Thank you all for this article. My amp fell off the dolly while going to a gig. Yep, a tube didn't survive. Had to play the gig with my guitar plugged into the sound board. Lot's o fun there! Going to the store to pick up a new set of ecc83s. Hopefully the EL34s survived. If I have trouble, i'll let you know, but you all have described the tasks at hand very well. Thanks again!!!! btw I'm going to try the JJ's. Nothing fancy. Hopefully they'll do the job. I was never happy with the low end out of this amp so maybe the bias was off from the factory. We'll see soon.

 

[slingblade]

Good news bad news. I picked up the tubes and replaced them. Here's the strange part. The amp is clearly labeled DSL40C on the front and back, however after taking the amp out of the box there are no adjustments as seen in most everyone's photos. There are two EL34 tubes, but 4 holes in the metal plate that appear to be for two more tubes for different model I guess. Four ECC83 tubes and yes one was broken completely. Looking on the top of the amp where the circuitry is, there are 2 trim pots for the main voltage I assume. The board is labelled DSL 100/60/00 model 1, so I guess this must be a really early version of the amp. So....how do you adjust the bias on these? I'm going to contact Marshall in the meantime. I'll post what I find out.

 

[slingblade]

Ah! mine is a dsl40c, not a CR. lol so that explains it.

 

[Lukas]

I have been unable to find any meaningful how to's with respect to the DSL40CR bias process using the test points and a multimeter (i.e. not one where you have to go inside the amp chassis). Do you know of one? Or if someone here in the know would write up a step-by-step that would be great. I was recently told by Marshall that these are biased to 35mV from the factory.

I checked the bias on my brand new DSL 40CR just today. Power tubes were set at 32mv, so mine wasn’t at 35. It sounded great regardless. I bumped it up to 35 as I read anywhere between 32-38 is good. I wanted to check the plate voltage and actually calculate it the proper way but I found no info on where to actually check this on the 40CR. If I burn up these tubes I got a new spare set but it sounds great at 35mv also.

 

[Troy T. Blues]

When I posted this originally, I biased the stock power tubes (Marshall/JJ) to 35ma. I recently changed the tubes to an older pair of Groove Tube EL34/6CA7 and I maxed out on the bias adjustments to ~28ma. Sounds great though.

 

[Matopotato]

There are several threads about biasing I think. I answered my findings here in "Dsl40cr - OD pedals into clean channel at home volume"
DSL40C is different in the details and requires you getting behind the inner cover I think, but the idea should be similar.
There are also different thoughts on if plate voltage should be considered or not when biasing.
My postings are all based on 40W setting when biasing.

Perhaps obvious but before getting new speaker, I would bias it. Has quite an impact. I had 32/35 mV. Tried 33mV on both, sounded worse. Went for 35mV quite nice and very different from 33. But best would be to measure the plate voltage first and calculate your own bias values. But be careful, like really careful since that is in the 500V area and potentially lethal.
I chikened out so far and got the 35 ideas from this forum and YT vids.

UpDate:
I now did a plate measure on 40w, and got 426/427. Googled to figure out which pin is nr 3. We pried/wiggled the tubs up enough to reach with a pointy probe. That way no need to unscrew the metallic casing. Blth showed same voltage. Went for 65% in some formula I found here wich told me 37mV. Can't say I hear any difference from first biasing to 35mA. But I was surprised to see that before biasing they had floated off from 35/35 to 42/37. So perhaps this needs to be repeated? Any others who experienced that bias "moves away" over time?

 

[s76yu12]

Plate voltage on these amps are lower than average. Another comment stated that plate voltage should be 440v and above....it's around 425v-430v for DSL40CR's and some are less than that. 60% dissipation would be 34.8mv...very close to the recommended 35. 70% however would be more like 40mv. I bias mine to between 35-38mv as a compromise. I don't want to go up to 40 because of tube life. The higher the bias, the quicker they can blow. Other than that most info on this amp in this thread are pretty accurate...especially the one with pics and instructions on what to do.

Full power/half power matters. If full power, the bias would be around 35mv. At half power it would be double that. The reason for the volume off and all of that jazz is to lessen interference. The more interference you have, you will not get readable readings. For instance, plug your guitar cord into the amp but disconnect it from the guitar. When you insert your multimeter probes you'll find an impossible to determine reading....it'll jump between low and high numbers.

Lastly, I warm up my tubes in standby for a MINIMUM of 20 minutes before playing or biasing. They say you only have to have it on standby warming up for like 30 seconds....it's absolute bullshit. Your gain output and sound will suffer horribly if you only allow a minute or so. I've found with virtually any Marshall warming up for around 20-40 minutes does wonders for the sound of the amp. If you don't believe me test it! Turn it on and then wait less than a minute and turn standby off and play. Turn the amp completely off for around 30 minutes and then turn it back on and let it sit with standby on for 20-30 minutes. You'll notice more gain and a crisper sound or at least you should. When I turn the amp off, I go in standby first for around a minute or so and then I turn the amp off. I do this to avoid the pop noise.

I also read people saying you should cool the tubes down by putting it in standby for the length you warmed it up....that's bullshit. The purpose of standby is to warm up the tubes, not cool them down. Therefore, the only way to cool them down is by turning the amp off.

Just some tips from a veteran marshall user =D

 

[Hackingthestrings]

I just purchased a used DSL40CR and really like it but am looking for an edge on my friend who has one also. I have a pair of low hour matched Ruby power tubes I can use along with four different preamp tubes: Electro-Harmonix 12AX7 gold, a ruby 12AX7HG (hugh gain) and two Thetubestore 7025 preffered series tubes. What positions would you use what preamp tube in?

As for biasing after I put the Rubys in do I need to worry about plate voltage or just go for it?

Thanks for the hand friends!

UPDATE: She was biased HOT!! at 41.2 both sides, yowza! Anyway brought both sides back down to 35.6 with the Ruby Power Tubes installed. This was with a solid 40 minute warmup session so the tubes were very hot. I am still undecided on what order to run the preamp tubes, input appreciated.

 

[TheKman76]

I think experimentation is the key. Try different valves in different position and see what works.
Personally I've never really appreciated the difference this makes to tone and tend to focus on EQ staging instead.

 

[Andytones74]

I did a lot of tube rolling in my dsl, eventually ended up with the stock ones back in.
V1 tube will make the biggest difference with regard to tone/ feel.
Mine sounds best biased at 35mv.
Have fun experimenting!

 

[SkyMonkey]

Hi @Hackingthestrings and welcome to the MF

Most talk of preamp tube rolling with a DSL40CR is about whether to put an ECC823 in V1 instead of an ECC83.
It is generally agreed that the 40CR and a humbucker bridge produce far to much gain for the amp to cope with Ultra Gain @ 10.
It gets increasingly mushier and more compressed after you pass about 5-6 on the gain dial.
Someone here reckoned it was because the 40CR/100HR gain circuit boosts lower frequencies too much.

An ECC823 has an x17 triode (normally x100) and an x100 triode (as normal).
That makes it half ECC82 and half ECC83, hence the 823 designation (82/3).
The differences in gain of the unequal triodes come into play because the 40CR (and several other Marshal amps) only use both V1 triodes in the Ultra channels.
The Clean and (I am pretty sure) the Crunch channels only use the x100 triode, so they are unaffected.
But the Ultra Green and Red get a gain REDUCTION from having an x100 and an x17, instead of two x100s.

An ECC823 won't fix the gain issue, but it reclaims about two notches on the Ultra gain sweep so that you can fine tune gain better and get a bit closer to 'everything on 10'.
Not to be confused with an ECC832, where the triodes are reversed!
JJ Electronics are the only manufacturer. See the ECC823 footnote.

JJ Electronic - ECC832 - 12DW7

JJ Electronic - Vacuum tubes, Capacitors, Amplifiers

www.jj-electronic.com

Other lower gain tubes like an ECC82 (both x17) and a 5751 (both x70) will lower gain too, but will do it to all channels.

But to absolutely max out the Ultra gain (as I often do) the best results are from taking the Ultra gain to within a hair of mush/compression and boosting (within reason) with an OD pedal out front.
It just works better than getting all the gain from the preamp.

 

[Hackingthestrings]

Hi @Hackingthestrings and welcome to the MF

Most talk of preamp tube rolling with a DSL40CR is about whether to put an ECC823 in V1 instead of an ECC83.
It is generally agreed that the 40CR and a humbucker bridge produce far to much gain for the amp to cope with Ultra Gain @ 10.
It gets increasingly mushier and more compressed after you pass about 5-6 on the gain dial.
Someone here reckoned it was because the 40CR/100HR gain circuit boosts lower frequencies too much.

An ECC823 has an x17 triode (normally x100) and an x100 triode (as normal).
That makes it half ECC82 and half ECC83, hence the 823 designation (82/3).
The differences in gain of the unequal triodes come into play because the 40CR (and several other Marshal amps) only use both V1 triodes in the Ultra channels.
The Clean and (I am pretty sure) the Crunch channels only use the x100 triode, so they are unaffected.
But the Ultra Green and Red get a gain REDUCTION from having an x100 and an x17, instead of two x100s.

An ECC823 won't fix the gain issue, but it reclaims about two notches on the Ultra gain sweep so that you can fine tune gain better and get a bit closer to 'everything on 10'.
Not to be confused with an ECC832, where the triodes are reversed!
JJ Electronics are the only manufacturer. See the ECC823 footnote.

JJ Electronic - ECC832 - 12DW7

JJ Electronic - Vacuum tubes, Capacitors, Amplifiers

www.jj-electronic.com

Other lower gain tubes like an ECC82 (both x17) and a 5751 (both x70) will lower gain too, but will do it to all channels.

But to absolutely max out the Ultra gain (as I often do) the best results are from taking the Ultra gain to within a hair of mush/compression and boosting (within reason) with an OD pedal out front.
It just works better than getting all the gain from the preamp.

Well ok, that sounds great, just ordered one will see how it goes thanks! By the way I assume ECC832 is correct not ECC823 as I could not find an ECC823 as a JJ product.

 

[Hackingthestrings]

This little DSL sounds amazing, it is really growing on me, combos sure have come a long way in 20 years. If Marshall made a DSL40 head version they would sell a bunch, not sure why they dont.

 

[SkyMonkey]

Well ok, that sounds great, just ordered one will see how it goes thanks! By the way I assume ECC832 is correct not ECC823 as I could not find an ECC823 as a JJ product.

No, No ,No, No, No!!!!

The 832 is the opposite of the 823. I did state that in my post.
The JJ ECC823 is a hard tube to find off the shelf, due to it's limited applications.
That's why it is a footnote on the JJ ECC832 page.
I live in the UK and had to order mine from Denmark!
I don't know where you live BTW.
If in the USA, did you try Eurotubes? They stock them.

 

[Hackingthestrings]

No, No ,No, No, No!!!!

The 832 is the opposite of the 823. I did state that in my post.
The JJ ECC823 is a hard tube to find off the shelf, due to it's limited applications.
That's why it is a footnote on the JJ ECC832 page.
I live in the UK and had to order mine from Denmark!
I don't know where you live BTW.
If in the USA, did you try Eurotubes? They stock he link you sent was the 832 guess I wasted $40

The link you sent was 832 so that is what I bought, guess it was a wasted $45 lovely. And nope you did not say the 832 is opposite in your post

 

[SkyMonkey]

The link you sent was 832 so that is what I bought, guess it was a wasted $45 lovely. And nope you did not say the 832 is opposite in your post

Not to be confused with an ECC832, where the triodes are reversed!
JJ Electronics are the only manufacturer. See the ECC823 footnote.

Read my post again.
I mentioned the 823 designation SIX times.
The single reference to the ECC832 was to warn: "Not to be confused with...".
There is no JJ ECC823 webpage, only a footnote on the ECC832 webpage, as I stated!



I'm sorry you got the wrong end of the stick, but I'm not sure how I could have made it clearer.