DIY How to Bias a Marshall DSL 40c Guitar Amplifier Using a Multi-Meter DSL40c Measure Plate Voltage

[@nogripes]

Marshall DSL40C Tubes on Amazon - amzn.to/2P89PNx Affordable Multimeter on Amazon - amzn.to/2nUAsan

[@rivy1994]

my husband doesn't have an account but wanted me to leave this comment for you. i also thank you for making sure he didn't electrocute himself :D "thank you very much, you saved me a whole tonne of time and money. i'm an automotive mechanic but i managed to bias my amp."

[@Driven5.7]

I'm glad you got down straight to business this was very detailed and simple. I appreciate that you didn't give a 40min science class before doing the job

[@bc47791]

Thanks a Million Mark! A dude in SF, CA is much obliged, thanks to your time and generosity of spirit.

[@allboutthemojo]

@@nogripes what should the bias measurement be for a dsl 20 cr amp? Also, if you know about the speaker would appreciate some input. My dsl came with the 70 80 speaker which most say is garbage. I can hear that it does not have a tight sound . What would you recommend for a tight sound, playing crunch sound not super high gain. Thx

[@dennisk9307]

Was able to bias my amp in 30min. Makes for swapping tubes much easier. IMO every guitarist needs to know how to do this. Thanks again!!!

[@TheDoogman]

so far the best biasing video I have ever seen

[@TheDoogman]

I was wondering if new tubes will help my 40C, it has a swirling hiss sound on the red channel even if no guitar is plugged in

[@andybrown1439]

Agreed.

[@pikeysrock]

DUDE, you're so nice to do this for us! thank you

[@shredhed572]

Mark, I followed your instructions on my dsl40c. Couldn't have been easier. I considered clipping the c19 bright cap, and spkr swap I decided to do one mod at a time... One tube was dead on 40mA Second tube was 36mA Set them at 40 I was thinkin this won't do much.. Omg. It's a fire breathing now! Even with the 70/80. Thank you! You made it so easy for me. I was considering trading it off. Now, it ain't goin anywhere!

[@jmabs5096]

Finally a video of actually pulling the chassie!

[@nogripes]

Hope it helped! Thanks for taking the time to leave a comment!

[@aaronanten8707]

Thanks Mark! I thought new strings were satisfying... then I re-tubed and re-biased my DSL40C! (Sounds great!!)

[@PeterDad60]

Mark, You covered everything I needed to know in a clear, concise way. You mentioned the Weber Bias Calculator that I had forgotten about. I created a new folder called "How to Bias my Marshal DSL40C" and saved your video and the Weber on line Calculator in it. I also saved the Weber Calculator into my existing "How to Bias my Fender Hot Rod Deville III" folder. Fender sets the bias at 30 mA (half of the actual 60mA) as you bias both of the 6L6GC tubes with only one "pot". I had the Fender biased at 57mA for a year and the clean channel would never break up even at max volume. Very loud. Two nights back I biased it at 65mA and all the clean was gone when I strummed a chord even at lowish volumes. The lead notes were still clean. But the change actually surprised me. I may go back down to the factory 60mA. I have read that you can bias the Hot Rod DeVille amps at 80--85-90mA and they will still work and they will sound very lively and hot. But the tubes may not last very long. I have a $49 Chinese made "Line-R 1200 APC which conditions (attenuates) the power down by @10% or up @10% from my house current measured at 117 VAC last year. My house voltage at the back of the "Line-R 1200" measured at 103 VAC. This @10% attenuation allows for a nice "brown sound" even on an amp that may be biased on the cool side. So when you do not use the Line-R 1200 APC your amp will go back to a clean amp. In this way I do not have to bias my amp for every mood change and feelings that I may have as I play. I highly recommend the APC. Sweetwater sells the AmpRX Brownie line of products that each have 3-4 different voltage choices which is very nice but they cost $249, $349 and $1,049. Yes I would rather have the $349 5A Voltage Attenuator, but my Line-R 1200 APC does the same thing, but only with a @10% reduction, no other choices. It works just as well however. Maybe when I have a cash surplus I will pop for the AmpRX Bronie $349 model. Mark, I hope I have helped you as much as you have helped me. I joined/subscribed. -Peter

[@PeterDad60]

I should add that I am expecting delivery of my own new Marshall DSL40CST on July 11, 2017 or just a few day's from tonight.

[@ChrisLeaton.]

Hello. I just wanted to give a quick thanks for this video. I've had no experience opening up and biasing an amplifier, but with this video I've just biased my first amp. Thanks again for clear, concise direction. It is appreciated.

[@robpayne9500]

You're the man. I've done tech work on guitars for years, changed preamp tubes,and power tubes on amps with self bias circuits. You made it look easy and it was. My factory power tubes were biased at 52 way to high, I believe that's why they burned out so fast. Threw in Mullards biased them at 39 and my amp sounds great. Thanks for the knowledge.

[@timbeckett6970]

Mark, I just purchased a "used" DSL 40 and it sounded fine. I watched your video and decided to crack mine open and wow! One tube was set at 46 mv and the other was at 36 mv. Set them both at 38 mv and voila! What a difference! Thanks

[@timbeckett6970]

Me too, my neighbors hate me!

[@MrRandalllowe]

1st video for biasing the DSL40c. Good job!

[@jeffwatt6196]

Just biased my new DSL40C quickly, safely and confidently, thanks to you, Mark! Both tubes were biased around 45 mv from the factory, and are now calibrated at a sweet 37.7. Much appreciated.

[@robd754]

thanks for making that make sense.. cant seem to ask that question without a 20 minute description of how complicated it is

[@sambezious]

Just bought this amp and was wondering about the biasing process. Thank you for sharing your knowledge! Great video. ~Sam

[@papadoogie1730]

Congrats , thank you for this info , I've changed the bias & replaced speaker with England made Vintage 30 , fantastic sound , what I've been looking for ...

[@hossak88]

Thanks Mark. Stock, my DSL40C tubes were biased at 35 and 40 out of the box. Checked plate voltage and did the pot adjusments based on the Weber calculator...I just have probes, and the rig you have would make it much more efficient. Putting it back together to see how it sounds. Right now I'm running a G12-80 from the late 70's, and I'm throwing a new G12H-75 in tomorrow.

[@paulkielt9301]

You don't have to wait 50 minutes on Standby, because after 60 seconds your heater filaments voltage won't change. You can adjust your bias after few minutes and re-check it after about one hour of playing, if you want!

[@niptodstan]

Good video. Well explained. Those 3 prongs where you connected the multimeter. Couldn't you have the female of them with soldered wires for easy(safe) connection?

[@george25199]

With the DSL 2000 they had trim pots and bias adjustments on out side the amp

[@kenaiello4851]

With my plate voltage at is 475 or so the amp sounds best at 30ma, my tech set it once he's been doing amps for 35 years. I decided to set it 34 then played loud Sat and there was something off. It wasnt as fat sounding on the red 1,mids were hotter sounding and a bit unpleasant! was kinda pissed so took it apart and set it back lower. Even the stock speaker isnt near as bright with these settings so keep in mind people these amps are mostly preamp distortion so running it hot makes it sound worse! Its sounded actually tighter now.

[@one1sol]

Fantastic and concise explanation of plate voltage reading and biasing process. Thank you so much. I have a question that I can't clearly put into words, so instead I'd like to ask if there are any major differences to do these tests on a Jcm 2000 dsl 50. Thanks again for your time.

[@JWEmbry-wc7qi]

Brilliant job Mark, and some of the clearest video quality I've seen on YT. Thank you sir!

[@AussieCornerStudio]

Thanks Mark, keep up the info much appreciated. All you non qualified techs out there please use caution you can see it looks easy but if you place your hand or finger in the wrong spot you can "die" Don't attempt anything your not 100% sure of, I watched a tech drop his guard by not removing his bling chain around his neck. While telling everyone to be safe his done the classic mistake "i've done this a 1000 times ........ What happened next the chain made contact with the chasis while his other hand was touching live 480 volts. Warning never be complacent minimise the risk take off all your rings chains anything conductive, even sweating on your skin will make a conductive arch. Keep it safe a tech can does this for x amount of dollars if your not 100% certain

[@colinstrydom9377]

Just want to give another thanks for this video. Just biased my first amp today. Marshall DSL40c, original tube failed, replaced with Mullards, 38mv. Was a lot easier than expected, but really nerve racking. My AMP sounds amazing once more.

[@blackdog19-64]

EH tubes seem to run a bit cooler and give this amp a Killer tone! I added a Celestion Creamback 65 speaker as well and it went from stock to rock! Sounds like a 2k Handwired sits on a amp stand in a corner and projects stellar tones (just blown away) by this little critter.

[@giantsfan6055]

Thanks for this video Mark! Anyone know how often you should be biasing this amp? Just looking for a general rule of thumb, this is my first tube amp got it a few months ago. Thanks in advance!

[@djgilevans]

Thanks for this great tutorial.

[@rauschhubert]

perfect, i have to say. very easy to do it yourself, thanks Hubert from austria in europe

[@jeffdoney1274]

You explained it perfectly, thank you so much

[@rockkstah2550]

Mr.Jenkins Thank you for your awesome video on this Marshall DSL 40 concerning bias. I would like to see a video concerning Biasing a Blackstar HT club 40 1x12. It seems like blackstar is very secretive about there amps.

[@ijamsum]

You should lower the bias to 36 or so if the voltage is 116vac because the voltage will be higher at times so best to be safe for your tubes ! I run my home variac abit low at 116 vac for practice but 120vac to bias the tubes or checking the bias !

[@O5wa1d]

Thanks for this. Excellent instructions.

[@allenkosanovich2143]

Great video mark. Huge help! Just replaced the power tubes in my dsl40 and thanks to your video, biased myself. Sure it saved me a few bucks but most of all I understand my amp a lot more now. Btw, I also swapped the speaker for a creamback and wow what a difference. Just couldn't get the stock speaker to sound right. Anyway, keep the videos coming!

[@AudioStorm1980]

Allen Kosanovich hey I just put a creamback in mine......did u go 8ohms or 16?

[@scottarmstrong239]

Great video you just saved me £100 every 6 months thanks

[@Kwarde.]

So I just made my first fuckup ever. I've been doing modifications to amps and pcs for years (including measuring), raised with it. Only yesterday I needed to change the bias again after replacing tubes (did it before) and there it went wrong. I wanted to measure the tube PC (the red wire) and I touched the red ánd the orange at the same time. Lots of blue light, smoke and then silence. Now as far as I can tell only the FS2 fuse has been burnt (I don't have any on spare). Measured the entire amp, and even put a wire on one good fuse (and put this fuse on the fused one) for quick testing. Now it looks like everything is okay (but I can only be sure after fully testing with a new fuse) but just a friendly reminder to always be carefull. And thank god tubes can take alot of voltages if not for too long.

[@Kwarde.]

Mark Jenkins My heart was approx raised tenfold (not really though- that would probably be fatal). And yep I can relate that holy s**** feeling hahaha. And feeling a bit like a loser like, how the helll did I manage to make such a stupid mistake? (I guess it was being too confident and wanting to go too fast)

[@tizmo57]

Thanks for posting this Bro, looks easy enough, Gonna give it a shot. Will post up the outcome...

[@tizmo57]

does it matter if it is on Triode or Pentode?

[@SMFLiveForMusic]

Thanks, excellent video, what do you think would be an ideal value for a DSL 100HR? about 75mV?

[@franciscoguinazu4810]

Hey man, nice vid. Thanks for taking the time. Got one question though. Im in europe, here we have 220v so do i still need to bias my tubes to around 37, 38 mah or will it be different cause of the voltage? Thanks

[@supermel9]

+Francisco Guinazu Yes, plate voltage will be around 450/460 also, so bias is the same.

[@kjmh67]

Great video Mark.. easy to understand. Ive just biased my DSL40c :D by following your video (39.7 & 42.4) to 38.3mv Quick question for draining caps (if necessary) as ive only had the DSl a short while..... Are the caps self draining? Ive seen on various forums that they are and if you click the standby button on, that will also drain the caps (after a while) Many thanks matey Kev

[@kc6671]

Thanks for the video. Tried doing this but the transformer on the left is too big and won’t allow the unit to pass the cabinet to come out. Tried to loosen it to slide it over a bit to get it out but that was a no go. Seems like I need to dismount it to allow it to pass or modify the cabinet. Any suggestions?

[@coscokolwiek]

Very informative and usefull. I should overcome my fear of being burned by electric shock and do it the way you show. Last year I modded the cabinet of my DSL40 so now I should try to touch something inside electronics. I can hear pretty loud "wind noice" when I turn volume know above 5 - recently I try to get power tubes break up instead of preamp break up so I turn volume about 8-9 but noice is too loud. I wonder if I make the amp cooler (or replace powet tubes) does it help?

[@Raiders757]

Where can I find a video like this for the Marshall haze 40? It kind of surprises me that I can't find anything similar considering how many people seem to own one.

[@BMeeley22]

Add my thanks to the pile. Been meaning to check bias for a while. Had the amp for a year. Discovered wall voltage was hot at 124+, bias was 38.7/41.3. Plate voltage 473. Weber says 36.9. Got mine leveled out at 36.5. Curious to see if it has changed much. cheers!

[@theoriginalparamutant2429]

I was having some artifact noise issues with my amp at volume . I sent it to an authorize "Marshall" service center. They couldn't reproduce the issue and they wanted to replace the tubes and bias for almost $300 to rule out the issue. I had them send it back to me. I purchased some Mullard tubes. I check the bias on the existing tube; they were 20mV below optimal. I changed the tube and bias myself after watching your video. The artifact noises are gone and the amp sounds even better than before. Thanks !!!! I'm changing the speak next, the low end "Farting" from the stock speaker is driving me nuts

[@blueeyedmaleusmc7569]

This is a fantastic video. Much appreciated. How do you like the Vintage 30 in this amp?

[@mahmutyldz214]

One of the trimpots can't go beneath 40mv.I turned it all the way clockwise and the final voltage can't go under 40. Is there something I can do.Thanks for the video it helped a lot.

[@tomjones5418]

You ever figure out why those pots aren't oriented like the tubes? The one on the right is the bias current pot, the left is a divider for sending that current in different amounts to either bank.

[@billwilliams6338]

MARK JENKINS, When you're biasing the power tubes in an amplifier circuit how do you bias the compression of the power tubes the 1dB compression point of when the power tubes start to compression? because its say to bias tubes at a 30mA bias current per tube to be safe but how do you know when the tube is compressing?

[@tonefingerz2021]

this amp is amazing. you can put and eq pedal b4 and or in the loop and the tones are 1000 times better. i have a question donyou have to re bias it when you change the tubes?

[@tonefingerz2021]

dang. the meters on aliexpress like 5 bucks and tips a dollar and solder iron i think y buks. anyways yes man i promise to GOd and ew in the loop is an absolute must for this amp. man i promise i have A Bd it 100 times it is so frikn nice the tones bro. i recomend a boss ge 7 band with the level lever cuz you can turn the level lever all the way down almost and turn all knobs to 10 or put the last lever up and barely turn the amp up and the tones are so glassy. dsl40 is so amazing with it. oh and make a soft v with the levers or smiley face. thx a million

[@tonefingerz2021]

Mark Jenkins shoot also bro does the dsl 40 come with good tubes and can i put the tubes from my evh lbx in it

[@ChrisLeaton.]

Thank you. Lots of great information. I appreciate it. Thanks again!

[@chrismoore4496]

Thanks man I'm on the fence about this because of the biasing but this video helps me feel more positive about getting one is the head the Same way?.

[@jccarlinhos7472]

Há alguns mods que as pessoas estão fazendo para o DSL15C que o tornam realmente bom? Tipo send return isso e possivel?

[@jasonricketts4055]

Hi, great video, just one question, what mode did you have the amp in? Was it in standby mode, or play mode. Also did you have the amp in triode or pentode mode and Does it matter for this procedure. Thank you

[@nousebig]

hello friend, great video, thanks for sharing your knowledge !, look have a head dsl100h, I do this same procedure, how to do? , 38.9 leave on each side pair of EL34? the plate voltage here is 470 v, here are 4 ewl34 two pairs, so my doubt is place the multimeter in mv scale and take up the 38.9? Thank you if you can answer

[@JPDESS]

+Henrique Guitar hi you should bias the 100w head by 74.5mv by duet at 470v for 70% dissipation. Good luck

[@juanalvarez1846]

is there any modification to match the volume of the clean channel and the crunch channel?

[@LMDAVE29]

Hi Mark, can I ask you a general electrical question about this amp? If I checked the resistance from the (-) ground of my guitar cable to the ground on the plug of the this amp (unplugged from wall), should that be zero? I get about 100 Ohms. I didn't know if the guitar signal ground is connect directly to the wall earth ground.

[@madmoe70]

Thanks for posting, just biased my amp and it sounds 10 times better!

[@БогартХамфри-ф2е]

Mark Jenkins, Have you measured the voltage drop between the cathode and ground and then just used the values as amperages?

[@БогартХамфри-ф2е]

Sorry) I found out that Marshall used to place a 1 kOhm resistor in between those pins...then everything is fine!)

[@silasfatchett7380]

@@БогартХамфри-ф2е It's actually a 1 Ohm resistor connected between cathode and ground. When you measure the voltage across it, the voltage in mV is numerically equal to the current flowing through it (i.e. the current flowing in the tube), e.g. 35mV corresponds to 35mA.

[@MadMike-8511]

Do you need to have the speaker plugged in when you bias it?

[@sonny6string822]

Thank you so very much for this video, it's greatly appreciated. I have the newer DSL40CR, i'm thinking to bias it, it would be the same... any insight you could give me as to if it may be the same test pins and bias trim pot would be welcomed.

[@andybrown1439]

Dsl40cr us way easier...check out oldguyjammin's video if this is still something you need to learn...

[@jawsrock1]

Good video. I bought one of these a while ago and love it, but I run the heck out of it. Good to have this info. Thanks. Can you do a Fender Deluxe Reverb RI?

[@MindFullCheeseburger]

going to try this for myself thanks!

[@stephenbarton2625]

Any chance you would do a video for a tube change on this exact amp?

[@stephenbarton2625]

Mark - that would be amazing! There is not one video out there for this exact amplifier. Awesome work on these videos by the way!

[@70mcnevin]

Thanks Mark. Excellent Video!

[@kixretrosjumpman2580]

Hello I have a marshall haze 15 and I'm planing to bias my amp but my problem is my amp don't have a stnby switch....so should I clip the alligator pin in the bias test point first and then turn it on or vice versa????thanks

[@jccarlinhos7472]

My friend, I am Brazilian, I would like to know without any possibility of making an adaptation return return in DSL 15c ... and pocivel?

[@chadlove3443]

Mark, does the plate voltage change with tube age, different tube models, or a hot or cold amp? I'm asking because I would like to check it only once and then write it down on the inside of the cabinet, but if it changes then I would have to check it everytime.

[@jccarlinhos7472]

My friend, I am Brazilian, I would like to know without any possibility of making an adaptation send return in DSL15c ... and possivel?

[@ksenodoxio]

Dude, could you please bias a Marshall DSL 100h?

[@marioroman4248]

Thank you, very interesting and great help for me.

[@moss-mop1363]

Would the dsl 15 also be a class AB amp like this one, or would it be a different class? It has 2 6v6 and 4 ecc83 tubes. I need to find the milliamps for each output tube, and I'm not sure which class I should choose.

[@SilkAirGamesPS4Gaming]

What's the bias range of the DSL40? Will it run hot enough for KT88's or should I go with EL34s or KT77s?

[@gregagnello7828]

Great video Mark, two questions. Are these amps biased from the factory cause I like mine the way it currently sounds, and if you accidentaly touch the black to red probes across the pins will you cook the amp? Thx

[@alexts4920]

any tips for values about DSL100H? i would like to know the bias values, should I double that value since I have 2 power tubes on each side?

[@alexts4920]

Great video though!!

[@Kwarde.]

That should be the same. There are amps where there is just one bias trim and that sets the value the same for both/all tubes (that's why you always should use the same tubes). My guess is that if you have two trims (and it should) they both control two tubes. Tubes are basically a push and pull for the speaker. With four tubes you have two pulls and two push tubes so that's why. If I am wrong, anyone, please correct me.

[@danelectr]

Hi, I have a question. I have a laney irt60 212. I read the manual and it say V1 12Ax7 for the pre amp and V10-11 6l6 for the power. Im confused with the versioning the V1 and V10-11. Does it matter? I cant seem to find the versioning in the tube store. Can you please explain what it means? Thanks

[@zsolttoth6948]

Very helpful video ...Thanks for taking the time for it!!!Greetings from Austria!;-)

[@70mcnevin]

Would there be any good reason Marshall would bias to 60mA and 30mA respectively? I was suprised to find mine that far apart.

[@stephenbarton2625]

What type of tubes can be used as a replacement for the dsl 40c?

[@TheWeidj]

Hello Mark, I hope I'm not a bother but I just bought the same AMP from the US where the voltage is 110V and now I'm in a country where the voltage is 220v. Do you if there's anything I should do to adjust for this change? Thanks

[@superbeast4287]

New to this....have a dsl 40c and Les Paul.....what is this bias about?

[@PeterDad60]

One question. I assumed that the plate voltage is 450 Volts when you set the mA to 38.7 for each tube during the bias demo. You mentioned your were going to measure the actual plate voltage. Anyway, is the plate voltage for the EL34's supposed to be close 450 Volts for the Marshall DSL40C?

[@PeterDad60]

Oh, I got my DSL40CST yesterday and it's a keeper!

[@flashg5454]

Hello, in the process of doing the biasing on dsl40. I see alot of people doing the c19 mod. have you done that yet? While I'm biasing I'm thinking of covering that aswell Do you have any concerns in doing that mod? i.e.. will it negatively impact the amp. Thank you

[@user-sn3cs2hd8r]

This is a good enough reason to select the Dsl40cr over the C.

[@EddieKirkbyGeddes]

Hey if I want to do the cap mod on my amp do I have too use a soldering pencil to break the C19 or can I cut with something?

[@scottm382]

One tube is giving me normal mv readings and the other is over 20 volts. What do suggest?

[@Shawn-rq4py]

I’m a Complete newbie to amp repair. I have a Marshall DSL 40c and I’m having trouble w sound. Popping, humming, hissing etc. My amp Is about 6 or 7 years old and haven’t used it all that much until about 6 or 9 months ago when I started playing my electric guitars more. The research I’ve done says it’s the tubes that are the problem and I plan to replace all tubes since it’s older. After I replace the tubes do I then follow your tutorial? Is that correct? Are these the only two that need to be biased? Or do all of them need it? I’m trying to save money and don’t want to take it to a repair shop unless I absolutely have to. I do have experience in electronics. I have completely gutted both a Les Paul and a Stratocaster and replaced all pickups, wiring, volume, tone pots and switches. So I’m not a total newbie to electronics but for this type stuff I want to understand it as much as possible before committing to it. It took me months of research before I tackled my guitars so I don’t want to skimp on my expensive amp. I’ve seen some videos that say just pop out one tube and pop in the other. I read an article stressing the bias on new tubes and that’s when I found your video. Thanks for sharing this knowledge. It’s invaluable to folks like me who are disabled and trying to save every penny possible . The less money I save from paying techs to do something I can do the better!

[@daveyboy8907]

Thank you... It's time that I check mine..

[@jsm147]

Great video - thank you!

[@peterodriguez6408]

Great job, very informative, useful thnx!

[@timothyjay2012]

Great video dude! I subscribed!

[@timothyjay2012]

Ive never seen the inside of one of these DsL's. Id like to have one of these flipped right side up in a head box!! Really nice Gigging Amp!!

[@timothyjay2012]

***** Hahaha!! Absolutely KewL!

[@hamdan949]

Do marshall DSL20HR have trim pot to rebias..

[@josephliptak]

When I saw the insides of your amp it reinforced my commitment to stay with my 50+ year old tube amps and their point to point hand wiring and solid pine wood cabinets.

[@Brian-gz8xt]

I believe it actually reinforced the fact that you are a D-Bag. Why would you watch a video on amp technology that you claim to hate. the answer is --> D-Baggery

[@smartacus88]

Joseph Liptak These are good pcb tube amps. The board is only 1/16 thick but it has good stress relief and good trace layout. The tubes and pots are chassis mounted. This is as sturdy as any vintage amp.

[@TestedTwice]

Would you know if this would apply to the DSL40CR?

[@daveyboy8907]

Are they biased from the factory???If so about what do they run??? Thanks

[@American-dy5jk]

Great DIY, thanks!

[@felixvalentin00]

i got one question... was the amp on standby while you measured the plate voltage?

[@silasfatchett7380]

No. The output tubes need to be conducting while making the measurements.

[@Chilinoploppy]

do you think a transformer swap in the dsl 40 would be a significant upgrade?

[@kenaiello4851]

prb would !