Before we even get started here we need to address the MOST asked question about all Marshall DSL and TSL 50, 60 and 100 watt amps. Even though we always state right on our customer invoices that the V4 phase inverter tube is the closest preamp tube to the power tubes, our inbox and message machine continue to overflow with the following question."Are you sure the PI tube is closest to the power tubes? Because there is a cover on the tube farthest from the power tubes so that must be it!"The answer? YES! Yes, without a question of a doubt!!! We are sure! V4 is closest to your power tubes!!! The reason the V1 tube has an RF cover on it is to help shield it from noise and radio frequency interference because it is the most susceptible tube for these things.We tube almost as many Marshall amps as we do Fender amps. We see quite a few old ones but mainly we see 800's, 900’s, 2000’s and JVM’s. We do still see a few of the old 60’s and early 70’s Marshall's along with the mid 70’s Mark ll Master Volume amps. We will usually load them with the E34L's to get a better low end but we have also been using a lot of the JJ KT77's which sound great or the JJ Big Bottle 6CA7's which are quickly becoming a favorite. For the front end we almost always go with high gain ECC83S's and balanced phase inverter tubes but another real nice option is using the ECC803S in V1. If you're looking for a real fat sound from a 50 or 100 watt Mark ll the JJ KT88’s will do it! We’ve tubed a lot of them with KT88’s biased up to about 60 to 65mA and the tone is very thick and fat. The 800 series amps that come stock with 6550’s will really come to life when fitted with either the JJ 6550's or the JJ KT88’s and ECC83S's. 6550’s in general are very sterile and glassy sounding but that ended with the JJ 6550. These are hands down the best 6550 we have ever heard. They are very warm with a great clean tone and the breakup is raw, crunchy and gritty. If you want an Angus - AC/DC type tone then these tubes really deliver! They are simply a lot of fun to play. However, if power, headroom and ultimate thickness in overall tone is the mission then the JJ KT88's are it. The best sounding Marshall we’ve heard to date was an old Marshall Major P.A. head that came in with RCA 6550’s ( you can see pic’s of it in the gallery). We installed a quad of JJ KT88’s and some JJ pre's in it and it had the biggest, warmest sound we’ve ever heard! The only warning we have on the 800 series amps is, always play one before you buy one! They are the most inconsistent Marshall's ever made. You can line up 10 of them no matter which model, and you will find 2 or 3 that sound amazing, then 2 or 3 that sound really flat and sterile with the rest of them sounding pretty good, but not amazing. Good tubes and proper bias will help a few of the amps that fall in that middle ground but you will find that several will still sound mediocre at best even with good tubes and proper bias. Buyer beware! The 900 series Marshall's are Bob’s least favorite for which he apologizes (”sorry 900 owners”). He did elaborate on this saying, “I did not say I hated them, I did not say they were junk in fact they have a very good clean channel, but compared to most all other Marshall's they are just not my favorite.” Almost all of the 900’s that we tube locally leave with 6L6’s in place of the stock EL34’s. We always ask the owners if they would like to compare the tone of the JJ 6L6 with the JJ E34L or Winged C EL34. We don’t sell the =C=-’s because we like the JJ’s better but we keep them on hand along with every other brand for comparison purposes. I’d say 99% of the 900 players like the more balanced tone that the JJ 6L6’s provide. The KT77's and the Big Bottle 6CA7's are also a nice option because of their increased low end.The 2000 series Marshall's are a step up from the 900’s in our opinion and we almost always use the JJ E34L’s and the EL34II’s in them. The KT77's are also an option once again but because the 77's have more sizzle (presence) on the top end it's sometimes a bit too much if you're playing single coils so you will have to roll the presence back, with humbuckers the KT77's ROCK! The JJ Big Bottle 6CA7's are quickly gaining in popularity with our DSL, TSL and JVM customers. They are very fat and as close as you can get to combining a 6L6GC with a traditional EL34. They are BIG, warm and thick sounding.The ECC83S's do very well to tame the shrill high end and thicken up the mids and low end and a good balanced ECC83S in V4 for the phase inverter really helps these amps. Another option in the head versions of the DSL and TSL amps is to use an ECC803S which is slightly lower in gain but thicker in the mids and a little brighter in the highs. This does real well with humbuckers.As for the 201 and 401's they use the same front end and we use the JJ EL84's for power which will tighten up the low end and makes them real punchy and less boxy than the sovtek/EH tubes. The hand wired X84 amp is a nice addition but boutique pricey! These are biased real hot so cooler grades are necessary to get much tube life from them.We get LOTS of questions about biasing these amps and lots of players tell us they are going to take the amp in to get it biased. Our response is "don't waste your money!" These are very easy to bias and all that's necessary is a cheap simple multimeter. We use bias probes to bias these but the test points and a multimeter will do just fine. If after you read all the info below, you still don't get it or have the courage to bias the amp yourself then head on down to your local grade school and find a fourth grader to give you a hand, that's how easy it is!Now, since we put up the original info on bias we have still been getting emails and phone calls from you total newbies out there that don't know what a multimeter is, or you're just positive that you will die from electrical shock, so here is a new and improved description of biasing these amps. This is a multimeter! You can buy a cheapy at radio shack for about 15.00 to 20.00 and that is all you need. Any goober like the one in the photo can operate one.The bias trims on the DSL/TSL amps are VERY different than all of the past Marshall's. Once you remove the back screen cover you will find three gold plated wire prongs poking out from the back of the amp with two bias screws, one on each side. Don't see them? Careful, they'll BITE you! OPEN your eyes! For you combo amp owners you will find these prongs under a black rectangular plastic plug on the back panel. The center tap is ground and the left tap measures the two left tubes in a 100 watter and the right tap measures the two right tubes and a setting of 80 to 90 DC Millivolts is good. Marshall recommends 90 per side. Don't worry if you temporarily have the bias hotter than 90 while adjusting to a final setting. For instance if both sides are reading at 100 and you turn one side down to 80 the other side will hit about 110 so when you turn this side down, kick it down to about 75 and when you go back to the first side which will probably be at about 100 by now, back it off to about 90 and both sides will probably be very close. After you do this a couple times you will be able to hit it on the first or second adjustment.In a 50 watter the single tube on each side is adjusted by the respective trim pots and a setting of 40 to 45 is good. Marshall recommends 45 and it's the same scenario, when you adjust one side higher it makes the other side go lower so you have to jockey back and forth to get both sides the same. Now the biggest question we keep getting is "will I get electrocuted?" Why of course you will! It wouldn't be any fun unless you got electrocuted! So ok, we lied... No, you're dealing with Millivolts here so there is no possible way to get a shock of any kind period. Stop shakin in your boots and bias that amp!Just clip the black negative lead to the middle prong with the meter set to DC millivolts and then touch the red positive lead to the left prong to test and adjust the left side and repeat by touching the right prong to test and adjust the right side until both read about the same as explained above. This is done with the amp on and in the play mode with a speaker load on the amp. This does not mean that you set a speaker cab on top of the amp to put a load on it, it means plug a speaker cab into the amp!!!Now that you have read about biasing a 2000 series amp you can watch a video about it here! How to bias your DSL - TSL and JVM amp.Now about all those issues with the 2000 series amps... Yes, there are actually quite a few issues with these amps. The most common issues we have seen are cold solder joints where the sockets meet the board and where the trim pots are soldered to the board. Either of these can cause a tube on one side of a 50 watter or a pair of tubes on one side of a 100 watter to run away and red plate! This is a fairly common occurrence, we get phone calls and emails on this all the time here is a sample; "Bob, I finally got my Marshall back yesterday they said they had to re-solder the tube socket. All my tubes are still good too. NO CHARGE under the extended warranty. I am going to recheck the bias to make sure it's still in your guidelines. Amp sounds real good still. Any advise after this happening ? Is this a common problem ?""Talk to you later"JohnSo yes John, and all Marshall 2000 owners, unfortunately it is a common occurrence but fortunately it is an easy fix if it happens to be the solder joints from the sockets to the board or even more commonly the solder joints from the trim pots to the board. So if you're seeing lots of bias fluctuation or having tubes run away on you, check these things out first! We have found other cold solder problems, Eddie was working on a DSL100 that had a hole down and upon pulling the chassis one of the screen grid resistors was literally laying loose in the amp...Every time you push a tube in and pull it out it stresses the solder connection with PCB mounted sockets. We have found quite few connections which look like a perfect little cone of solder but when you push on the socket, the perfect little cone lifts right off the board! The reason is, the run on the board never reached a hot enough temperature for the solder to flow and adhere to the run, and only adhered to the socket connection. This is unfortunately the reason that amps with this issue can periodically red plate tubes.There are other problems such as resistors losing values when heated and a little investigation with a heat gun can confirm this. A good in depth write up on some of these issues was done by JC Maillet but is not available on his website anymore, we took the liberty of scraping the text of his article which can be found here; JC Maillet - Marshall TSL122 All credit to JC who is obviously very knowledgeable and spent the time to research and document the DSL/TSL bias issues. As for advice for after the fix, just clean your sockets when you change tubes and bias the amp. Then let it sit in the play mode for 10 to 15 minutes, check and set the bias if necessary. Remember, if you burn up or red plate tubes in one of these amps it's your problem!!The bias trim on the TSL 60 is very different and much simpler to adjust than the DSL/TSL 50's and 100's which have two trim pots. The center tap on the TSL 60 is ground and the left tap measures the left tube and the right tube and a setting of 80 millivolts is good. Just set your multimeter to DC millivolts and dial in the tubes.You guys with 201 and 401 amps have to take the amp apart to get the test points and trim pot. Here is a pic. Marshall recommends a setting of .675 volts for the 201 and 1.375 volts for the 401, we feel that the 1.375 is way too hot and recommend a setting of between .8 to 1 volt if you are using the test point and for the 201 between .400 to .500 is good. 201 401In the right pic you can see three test prongs, the middle one is ground and you can measure the left or right prong to measure the bias. You also need to be careful when changing tubes because Marshall chose to make the access holes in the chassis for the tubes VERY small. In fact we have to search thru all of the tubes that we send out for these amps in hopes of finding tubes that are skinny enough to fit! Never push on a tube to get it to go thru the access hole, its glass and it will break! In fact quite a few brands of tubes will not fit in these amps unless the access holes are ground or filed out, just make sure to vacuum out the debris when you're done. One of the best sounding newer Marshall’s is the Vintage Modern. This amp has more of the classic Marshall sound than any other Marshall going clear back to Silver Jubilee's and then the 1975 thru 1979 Mark II amps. The VM has a great sound right out of the box and although it's really just a single channel amp with a boost it can cover a lot of ground. It has a fat tone that is thick and complex with a great snarl in the boost mode. You can read a few reviews on the these amp over in our customer review section. When you replace the stock power tubes with the JJ KT66's which are real KT66's the harmonic complexity increases and and the slight mushiness the amp exhibits with the stock tubes turns into a warm powerful sound. We often use a real hot high gain ECC83S in the V2 position to get a bit more form the boost. The VM has internal bias test points but thankfully someone at Marshall talked some sense into the designers and they are using a single bias pot like the Marshall's of yesteryear. The left test point measures the left tube or pair of tubes in a 100 watter, and the right test point measures the right tube or right pair. There is a little disparity or error even with a dead on pair of tubes but it's only about 3mV. The only hitch with the VM is that Marshall chose to use the crummy Bear trap style tube retainers... The bases on the JJ KT66’s do not fit inside the factory Bear trap style tube retainers. In Fact the retainers barely catch the rounded bases of the chinese KT66’s and do not really hold them from pulling out. So to run the JJ KT66’s or the sovtek KT66’s or the sovtek tungsol KT66’s you either have to clip the retainers off or flatten them out. While it's not an issue to run a head with no tube retainers we would not run the combo version of the VM with no retainers. So for VM combo's we recommend removing the Bear trap retainers and replacing them with the spring and cap style retainers that hold the tube in from the top rather than the base. This is a pretty easy thing to do and can be done by removing one of the screws and then swing the stock retainer out of the way and screw in the first side of the spring retainer. Then you can remove the second screw along with the stock retainer and then screw in the second half of the spring retainer. Its well worth it because the JJ KT66's will really make a big difference.While the VM is Bob’s pick we must also say that players looking for more versatility should give the JVM a look. We think it's a step up from the 2000 series Marshall's in tone quality. So if four channels along with lots of "bells and whistles" are attractive to you should give it a listen.The bias in the new JVM four channel Marshall's is the same as the DSL/TSL amps but Marshall inconveniently moved the test points and trim pots to the inside of the amp so you have to remove the amp from the chassis where you will find the same three prong test point setup with two trim pots.