Soldano SLO100

This review is for a May 2004 SLO 100, bought new in December, 2004. Let me begin by saying I do not gig for a living, I do not teach guitar for a living, and I have no relationship with Soldano or any OTHER manufacturer for that matter. I'm an Airline Captain, but appreciate the best quality I can find, and this SLO 100 is by itself in that category. Let me also say, I have owned several Soldano amps in the past too, but for hi gain, nothing compares.

The SLO is a 100 watt class AB tube amp using Sovtek 5881's in the power amp section and 12AX7's in the preamp section. It is a 2 channel amp with master and gain for each channel. It has a shared eq and presence control but the clean side has a bright, and a clean/crunch switch for it. It has a really good +4db effects loop, slave out, impedence selector for 4, 8, or 16, channel selector, and best thing is the layout of all the above. If you run a big pedal board like I do, it's nice to have all the inputs/sends/returns etc. on the same side of the amp. In this case it is on the left rear side of the amp. Great for using a ready made snake from your pedal board.

I ordered mine from Pete's Amps in Valdosta, Georgia, like I've always done in the past. His service is superlative. This amp was in stock, black, and exactly like I wanted, NO MODS DONE. If you want the Warren Haynes mod or depth scoop, knock yourself out, I wanted nothing to do with affecting this amps change in original tone. It is PERFECT right out of the box, and with me being a perfectionist, that is hard to say.

I find the reviews on this site about the SLO's clean side a little misgiving. No amp other than maybe a 60's Fender/or Dumble has a fabulous clean channel, other than the Lucky 13 from Soldano, but I own one too like I said earlier, and I can't see a major difference in clean gliss etc.. between the Lucky 13 and my SLO, and both are 100 watters. Ths SLO is very clean for me especially in a live setting.

No, this isn't my first boutique amp that I've owned or played intensely. That list includes a 71' Marshall 100 watt super tremolo, Acoustics, Lab Series, THD, Bad Cat Mini Cat, Trem Cat, Cub II, and Hot Cat 30R, Bogner Uberschaul, XTC, Shiva, and Metropolis, SMF, Star, Rivera, and a host of others.

I use this amp at home and can gig with it if I choose, but let's face reality, this amp needs volume but NOT like an old Marshall which is either off or on 10. I do use a Hot Plate heat sink with this amp in either 4 or 8 db attenuation which does the trick. Then it purrs but doesn't break glass at unbelievable volumes.

Ok, it isn't a Dumble clean or an Uberschaul dirty, both of those are one trick ponies, but it is by far the finest amp I've ever touched or played. I've been left speechless with this one. Just to make sure it stays perfect even though it is incredibly well made, I'm buying road case for it. I can't imagine not playing with this one.

I'm a Skynyrd, Velvet Revolver but not all of the heavier stuff, Gov't Mule, Frank Marino kinda guy on the humbucker side, but on the clean side, I'm an SRV, Trower, and Jimi kinda guy. I own several vintage to new or custiomized Fender Strats and Gibson Les Pauls. I use a custom pedal board I made housing Fulltone, SIB, Ibanez, Peterson, and Ernie Ball boutique effects. Amp is very quiet.

The overdrive channel is something that unless you've heard it, you have no idea what it sounds like. It is amazing and can do it all. I was told I'd probably never give up the clean my Lucky 13 amp has, but I've already boxed it and selling it as we speak. Tremendous amp and incredibly versatile, but for crystal clean I have a small Bad Cat, and for overdrive, it has to be this SLO.

Built better than any amp I've seen incorporating a lifetime transferable warranty except for transformers and tubes. I can't imagine it ever breaking.

Mike Soldano and Bill Sundt are very available if you need. Sure, they are busy making great amps but will get back to you just give them a couple of days.

I've played on and off for 28 years, but fly for a living. I'd freak if ever stolen and would buy another one immediately to replace it. If I had to choose one tiny thing it had, that might be a foot switchable option for the clean/crunch switch, but that is splitting hairs folks, just flip the switch for crying out loud, and rock on.

Expensive amp, but once you buy an SLO 100, your search for the best "TONE" will be over. Nothing compares.

Basic features, two channels effects loop and EQ. No big deal, less is more in the amp world.

All kinds of mod are available for the amp. In my opinion, an amp this pricy (new) should receive any and all updates free, or better yet, be designed properly from the start. I know that is many times impossible, but $3000 as a baseline is way too much already if the amp needs mods to sound truly high end. That's why I waited to find a used SLO, so I didn't get too pissed off about having a boatload of cash wrapped up in one amp.

I play classic rock, heavy metal and some blues. This amp is actually pretty flexible. You can get a really cool sounding searing lead tone or just a nice crunch. Clean isn't too bad considering the monster that lurks within. All that or anything in between. Very midrangey!

If you dial the preamp gain much beyond 3, it loses it's articulation and sounds some what compressed. I tried JJs and Svets which help quite a bit, but still the character of the high preamp gain is still present in which to say the notes seem to lose definition. I think the best tone in this amp is to crank the master with minimum pre on the lead channel and let your pick attack dictate when the amp overdrives .... basically let your fingers bring out the tone just like you would do on a Marshall super lead.

Compared to my early Mesa DR, the Mesa has more attack and is much more crisp sounding, but it can get slightly more buzzy with the pre cranked way up compared to the SLO..... who with the same setting, just compresses the hell out of the tone. Its a toss up, both amps have their strong points. The SLO has a way better clean than the DR.

Built like a tank. Excellent attention to detail. Michael followed the tried and proven method of flying leads off the pots and chassis mounted tube sockets. Simple and neat looking. The only thing better is probably a Hylite era Hiwatt DR. Probably could play it for years with no probs.

Never had a problem, so no comment.

I've been playing 18 years. I have a 74 Marshall superlead, a JTM45 reissue, a 93 Mesa DR, a 71 and an early 81 Hiwatt DR103, a Hiwatt clone-Sound City amp, a few Voxs amps, Ampeg bass amp and I think that is it. Guitars... my favorite is a newer USA Tele with a fat neck. I have a 84 LP Custom, a 03 SG, 90 MIJ 62 reissue Strat, 2 Ernie Ball Axis, Fender Pbass and some acoustics.

Yeah, the SLO isn't a bad amp. It is fun to play around with and has it's place, but my old Sound City just stomps it in the tone dept. The Hiwatts too, especially the 71 has such a warm even tonal balance, you just don't realize how good until you compare amp to amp through a common cab. Of course the older amps have to be crank and attenuated to get that nice lead tone. Preamp gain just isn't the same as power tube distortion, but it is fun to play around with just for something different. Another plus is you don't blow your hearing out with a SLO quite as fast, although it is a pretty loud amp.

If it got stolen, I would probably go out and check the new Mesa Stilettos out if I wanted another high gain amp. I would certainly consider another SLO too for the right price.

Over all, it is a good amp for what it is. I love the tone from the 70s amps when the power tubes did the talking, but the SLO style amps are cool because you can still get a good sound and good sustain at a low volume. I put a few NOS Mullards in the pre and finished em off with JJ ECC83s tubes! Wow ! what a nice change in tone. Sovteks are crap and I have no idea why they come standard in a $3000+ amp ??

Anyway, Cheers !

I own a 2004 with modifications. And this is meant to be a review free of DRAMA. Unlike many reviews offered on this website. Here goes. VERSATILITY. The SLO 100, in my opinion is made to SOUND great. As many may know or believe, to add features increases the chance of sound being tainted. I believe this to be true having owned a Bogner Ecstasy and multiple Marshall products. The SLO 100 has two channels, but they share preamplification settings. The EQ just has to do. And I think that it does. It gives you bare bones for the ability to change drive or volume levels save independent clean and overdriven volumes. But I think anyone can make it work. It's about priorities on stage. In the studio it roars, has great flexibility, and loves to have it's picture taken. And that #1 priority certainly represents itself live. It offers an FX loop, but it has high standards. I think that it only works with +4 FX. -10 for me resulted in a slight loss of volume, but loads of high end was taken and was too crippling. If it is going to hurt the tone only slightly, you will most likely hear it very well. So unlike me who found out the hard way; if you are looking to buy it... but also use Delay and Reverb live, you'll need a serious processor or rack. The SLO packs a mean punch. Physical. Only serious equipment can interact with it's levels. I use it live and in the studio. Haven't tried Diezel yet unfortunately. But for me, anything else will have to measure up to the SLO.
It is certainly loud enough for any venue. More cabs might help improve coverage on big stages, but my single 4X12 is plenty in clubs/universities.
TONE. It has a mouth and vocal chords. I'm sure that sounds a little...dramatic. But truth be told, you'll never be able to recreate it through blends of other gear. I feel that certain amps can be referred too. Enough to create the same emotional reaction that the amps of influence did. But Soldano has harnessed a so far immortal voice. And the SLO is probably the most well heard.
Tight humping low end. Quick enough to be tight, but not immediate and ruining the 3D image.
Flexible throaty mids. But you need to be careful with the Treble and Presence. They have great impact on how the mids sit.
I can only try to give you a taste of how much attitude this head has.
In the world of competitive tone, this head has the pink mohawk. But it also has intelligence superceding other competitors. It covers a wide spectrum. Climbing from sorrow, evil and manipulation, it can reach heights of incredible joy and optimism. It amplifies what and more importantly, how you play. If you hurt, it will cry for you.

Right now I'm playing a Gibson Les Paul, and a Fender Telecaster.
The music I write is predominantly heavy, groove oriented patterns. Coupled with eccentric clean passages most usually laced with either sorrow, or learning.
The SLO has a flexible enough "clean" channel that I can ride it live through the set and cover all of my needs. The overdirve channel allows me countless paths to achieve the energy I need to convey. Plus it's ability to cut through the din makes solo concentration easy to achieve.
It's only noisy when you make it look in the mirror through your guitar. About three feet at live volumes is all you get unless you have a bypass.
The clean channel distorts. Not a cleaniac's amplifier. But it can be incredibly relaxed and smoothe. From my perspective, any clean track ever recorded could be replaced with the SLO, and the recording would probably benefit.
The distortion isn't buzz saw, but I think of it as switch blade. Classic... yet dense. Certainly enough to represent great power.

Soldano pride themselves in the reliability and housing of their product. It's military. No really. I have to really want to hurt this amp to cause failure. And if I succeed, something tells me a paper middle finger is going to pop up as a last remark from somewhere in the chassis.
I can't afford a back up. But I'm not BIG time yet. If ever I can I will. But my ease of conscience is only due to this head's structure and reliability.
It has not broken yet. And I do not expect the mortal parts to go soon save the tubes. It's really relaxed. You can hear it's pulse. Though always ready to go over the edge, it breaks no sweat.

I bought mine on ebay. Thinking that the FX Loop was always stock, I was bummed when I recieved it and had to have it installed for more $$. The heads that are special ordered only have an FX loop if specified. While having the install done, the service and support was unbelievable. Bill is an amazing man for those who are new to the product. The warranty is lifelong save the transformer. And they represent their product.

I've said enough.

Well, after approx 11 years use, I have to make a short review of the SLO.
After reading the last review below, I just had to laugh. Seems like this guy has gone totally wrong with his SLO. A "Tube-screamer" for leads when using a SLO is IMHO a waste. The SLO needs to be cranked a bit to sound its best. When You "know" this amp, its capable of KILLER tones.
The features are well covered from other posts, a simple yet very versatile amp. For my playing style, all I need.
I play in three diff. bands, a blues band, a "classic rock" band, and a metal band. The SLO covers all styles great.
I've got two SLO's, a '92 and a '99. Yep, that says a lot. I really like this amp compared to a LOT out there.
It gets a 9 for features, but if it had a crunch & lead boost it would be a def. 10.
No amp is "perfect".

I'm using mostly LP's, and from time to time strats.
LP's: 59'Historics with Tom Holmes 450/455, and orig PAF's, a '68 LP and a 1980 LP Heritage 80 with Lindy Fralins, and my main LP, a 1970 LPC with Duncan Custom in the bridge. The SLO tranfers all the guitars diff. tones excellent. Change to another pup, and You'll hear it instantly. Plug in a strat, and You'll have strat-tones in spades.
Clean-ch:
I've never used the clean-ch that much of the SLO, but the clean is good. You can even max it for a nice warm breakup tone. Compared to say a BF Fender Super, Matchless DC-30/JJ-30, Bruno Coowtipper etc, the SLO clean-ch is not "that great". But good enough for a "high-gain" amp. IMO, better than my long gone Bogner XTC and Ubers clean-ch's, which were cool enough.
Crunch ch:
A great crunch, from slighly break-up to AC/DC and old VH. I love this ch. For some blues gigs, I used this ch alone, and just used the guitarvolume for leads.
Lead-ch:
What can I say? The industry std, Fat, fat, fat. It cuts great within the band-mix. I've never played an amp with fatter mids than the SLO, it growls.
Beeing an old Marshall-guy, it's all I could ever dream of reg. a "hot-rodded" old Marshall. Exellent string to string definition, and this amp stays CLEAR even with the most gained-out tones.
This ch covers groovy ZZ-Top, VH to Pantera tones.
Or....smooth Warren Haynes tones are easy on tap.

I've had both my SLO modded with the WH-mod, which takes away some topend "sizzle" on the lead ch. IMO, You also loose a tiny bit gain with the WH-mod engaged (I have a switch on the backside of the amp). This mod is not a "must", I use the SLO more or less witout it. But, cool to have it if You "need it".
I've also another mod with both SLO's, a fixed bass-boost (sim. as a depth-mod). This mod gives the amp(s) just the "right" added bottom end. I feel the SLO is a tiny bit thin on the lower reg. without it.

What's always real cool, is to hear the SLO through a PA. It find its place easy in the mix, and what "might" seem like an amp which could use more bottom end, all questions just dissapeared. It barks through a PA, and usually (in my experience), no need for any eq on the board. Let the bass-player handle the extreme bottom end.
Hehehe, regarding "bottom-end", I could never that good tone with my Uber or old Dual&Triple Rects.
Same goes with recording, it records great!
I could go on "forever" comparing it with other amps, all I can say:
The SLO gets a SOLID 10.
(Despite the clean-ch, which would get a 7 if I used it).

It's built to last. Transferable lifetime warranty. Take a look inside, and You'll see that the amp would not have any issue with reliability. I've used the SLO many years, without ANY problems whatsoever.
I can not say that very thing for a couple of other well-known manufacturers out there.
The SLO has always delivered killer tones. And I think it will last "forever" if not run over by a truck or something.

Every time I've been in contact with Soldano, I've got great customer support. They stand behind their products 100%, real nice and knowledable people.
My questions have been related to diff. tubes and mods, and they've been very helpful.

The SLO is a bit "finchy" about the "right" tubes and speakers. I've used Svets EL-34's, and the NOS Sylvania tubes for the "best" tones.
I tried out some KT-66's which were nice. Sort of a mix between the EL-34 and 6l6, big headroom and more power. But I felt they were too "clean". I like the power-section to break up more, without being "insane" loud. The stock 5881's were to hard&glassy, but they have a tight good bottom end.
For my taste that is.
This amp can sound good to GREAT. IMO, it depends on the right match with tubes / speakers. I've found old GB's (G12H30's or 25W's) to be the best. Old 412 Marshall or Bogner cabs, are a very good match.
IMO, even better than Soldanos own 412's. I still use a straight Soldano 412 with old GB's on the top, and Matchless-mod V-30's on the bottom. Sounds good, but still, Marshall/Bogner beats it.
I sold off my slant Soldano 412, a bit "thin" compared to the above cabs. Hmmm, then again it was great for small stages. And it's very easy to transport. The straight Soldano 412 has a bit more bass, and sounds fuller. Its a keeper.

I've been playing approx 29 years, and I've never been "that" pleased with any other amp. I've been through many great amps, including a couple which I still miss, like the Bogner XTC or a BadCat BlackCat. I actually sold off my XTC amp to get another SLO. No regrets, but I "wish" I could have kept them all. Heheh, I'm not "that" rich.

My old Marshalls been collecting dust some time, but I use a '69 Marshall 50W JMP with the SLO for some rock-gigs. A great combination.
For the heavier stuff, I use two SLO's or one SLO running with a BadCat HotCat-100. This is the best two-amp combo I've used "so far".
The SLO's great cut and fat mids combined with a very greasy&woody tone from the BadCat sounds IMO KILLER.

No need to list "all" my amps, but a Mathless Phoenix 35 is my "no-1" for the blues gigs. A Matchless JJ-30 is at home, too great to sell off. Etc.... Anyway the SLO is still "it", and that's the amp I grab when just going for it.
If I lost the SLO, I would def. get another, have the mods done, and get rolling again. I can't really find something to "hate" about it, I'm just that pleased. And I have been for a looong time. Some know I have said a lot about the SLO on the HCAF. I'm happy to know that one amp actually can "do it all".

Anyway, the SLO is not the amp for everyone. Spend some time with it. It needs to be played a little "loud" to open it up, and to get the best tone. Its not a "bedroom-wanking" amp, the power-section needs to be cranked a bit to have it "bark & growl". Still, I use it sometime at home also, and yep, nice tones.
Btw, I use only a BuddaWah with the SLO , no other fx's. This amp does not IMO need any fx to "clutter" its great tone.
Last, I "hate" to give 10's. No product is 100% perfect, still I feel the SLO truly deserves it. Hype? Nope, just a stellar amp still going strong after 16 - 17 years.
Real cool!!!

Well, it's pretty simple to use but I find it very limited. I wish there was at least a reverb.

This is where I have a problem. I bought this amp because I like the sound that Warren Haynes gets but he must have a much different setup than I do. I use Tube Screamers for my gain and very little of the built in gain from the amp. The amp is very crusty sounding yet at the same time way too midrangy. It's almost like missing the right spectrum of sound frequencies. No EQ helped with it. I don't mean to offend anyone who has had good results with this... I'm glad for you. However, when I compare it to my 1965 Fender Twin or my Mesa Boogie Nomad 100 through the same cabinets, it just doesn't sound pleasant to me at all. I think that it is way overpriced. I have decided to sell it since I can't stand to plug into it anymore. If anyone might be interested in buying a used SLO-100 my email is TreyPhanDobbs@aol.com. After this glowing review, I'm sure that I'm hurting my chances of selling it but I want to be honest. Nothing about this amp sounds anything like the tone that I want. Period.

It's built great and I doubt you would ever have a problem. I just changed the power tubes to try and get a better tone, and it just got worse. Oh well.

I've never really dealt with them.

Like I said, I don't mean to offend anyone who loves this amp, but I can't stand it. I would love to sell it. I wish I had saved the money and bought two better amps instead.

2 CHANNELS.MANUFACTURED I BELEIVE IN 1988. MINE HAS LOOP BUT I PREFER THE SLAVE FOR DRY SOUND AND EFFECTS. GOOD FOR ALL VENUES. PLENTY LOUD.

I USE FENDER AND GIBSON HUMBUCKERS AND SINGLE COILS.( ACTIVE AND PASSIVE) WORKS WITH THEM ALL.SOME NOISE ON VERY HIGH GAIN BUT NOT ANY WORSE THAN ANY OTHER HIGH GAIN AMP. DISTORTION CHANNEL SMOKES, CLEAN CHANNEL NOT PRISTINE BUT CLEAN ENOUGH IF YOU KNOW WHAT YOU'RE DOING.

I'VE BEEN USING THIS AMP SINCE 1994 AND THE ONLY THING THAT EVER HAPPENED IS I BLEW A FUSE TWICE AND OF COURSE SEVERAL RE-TUBES.

CUSTOMER SERVICE IS AAA. BILL IS VERY HELPFULL. I HAVE A LIFETIME TRANSFERABLE WARRENTY BUT IT DON'T LOOK LIKE I'M GOING TO NEED IT.

I'VE BEEN PLAYING PROFFESIONAL FOR OVER 25 YEARS IN ALL KINDS OF PROJECTS. FROM JAZZ TO BLUES TO ROCK AND HEAVY METAL AND THIS AMP HAS SHINED ON ALL STYLES. I OWNED ALL KINDS OF MARSHALLS AND FENDERS AND OTHERS AND THIS AMP KILLS THEM. SOMETIMES I WISH IT HAD A SPRING REVERB BUT I GUESS THAT WOULD EFFECT THE TONE. IF LOST OR STOLDEN I WOULD BE OUT A COUPLE OF GRAND FOR A REPLACEMENT.

I'm starting to get really pissed off with some of the reviews. I have spent a lot of time playing around on a fully-modded, and on a non-modded, slo, and I thought it was the best amp ever. I don't want to hear any of that bullshit about the clean channel sounding thin or flat, play with the knobs. If you still don't like it, buy a fucking equilizer. The crunch channels carries enough "umph!" to keep any bright distortion fan happy. It isn't for nu-metal, but those people don't deserve anything other than a Crate, anyway.
P.S. Learn to spell Wylde, dumbass.

I wrote a review down there somewhere. I cant help but want to come back and comment after I read and hear so much hype and bullshit in so many different places. Im not a bedroom jammer. So everyone knows where Im comming from. Last year I played 190 dates. Ive been paid to record many tracks. Heres an update. Im still using my Soldano when called for but not because its in any way my ultimate tone. Not close.

#1 - The clean channel is nothing special. Thats right. Its not bad in any way. But Im going to scream if I hear one more person somewhere tell me the Soldano clean is like a Fender. Ugh!! I can tell that most people would find it an addequate clean sound. Some would feel its just fine. But many would, and do, hate it. Especially players who are used to nice, dynamic, touch responsive clean sounds. Not here. What is here is a great clean channel for a high gain channel switching amp. Its a clean sound for when most of your music is heavy. I never thought that Clapton or Knopflers tone through a Soldano was that great at all. Dont be fooled just because their good players. If you really listen you can hear just how thin and sterile that clean sound is compared to when either of them use a Marshall or a Fender. But if you want that sound its here. Like they say be carefull what you wish for.

#2 The crunch or lead channel in no way sounds like a Plexi or other marshall. This amps gain sounds are reminiscent of modded marshalls, but in no way do they sound like Marshalls. I own many marshalls. Not the new stuff. I have a few JMPs, a Superbass and a 2203. They sound different. Period. You want Tom Morello, Zakk Wyldd or anyone who usses a JCM800, get a JCM800. Their much cheaper. This amp cleans up resonably well with the volume knob for a high gain amp (despite whove used them and the hype these things are saturated high gain amps.) The gain has this really present bite to the high end. Its got this really metallic, thin bite especially with alot of gain. You can really hear it on the lower strings. This amp can sound very thin. I would say that comes hand in hand with having an amp this saturated and still this tight. It is tight. If you want the opposite of a Dual Recto when you chug a muted power chord on the low strings this is it.

Describing just what the gain sounds like is difficult. Im not a big Aerosmith fan at all but I was listening to that Big Ones CD a while back. I was curious because one song reminded me so much of my Soldano. I went home and looked it up and sure enough, Joe Perry and the other guy used Soldano all over the album that song is from. The song is #1 on the Big Ones CD. If you listen you'll get a great idea of what the Soldano sound is. That song is such a good example that the first time I heard the song, without knowing, I said thats got to be a Soldano. It has that metallic bite to the notes especially when you play open notes on the low strings. You can hear this real well. Listen to that song.

I would say the eq is totally balanced and clear. It doesnt have that creamy midrange like many british amps. It can and does cut. It cuts well for this much gain. No sound man should ever say he has a problem getting a nice clean and clear sound from it. Id never call the amp muddy. Its very bright and present. But it has no vintage vibe. Not in any way. My personal belief is if your into cleaner or overdriven sounds, and your used to amps of that type or have good ears, you will ultimately not be pleased with this amp. If you like Nu-metal I dont think youll be into this amp either. Its much to thin, bright and tight. I usually dime the bass (since this amp is so thin and tight the bass on 10 will not fart out or be "too" much) and thats something I never do on any amp. I leave the treble at noon and the presence low. This tone stack is not that interactive with the tone. Its more like a stereo eq. I believe thats because the tone controls come after the preamp and before the output s

Two foot-switchable channels with separate gain & master volume controls. The Bass-Mid-Treble tone stack is shared by both channels. It also has a +4 dBu effects loop, which may be too hot for some gear.

The clean channel sounds pretty flat - I would appreciate a bit more mid scoop, as Fenders offer. The overdrive channel sounds similar to vintage Marshalls at low gain settings, but gets an overwhelming amount of presence as the gain is increased.

Built well, with quality components. However it is a bit finicky about preamp tubes. The first stage (V1) requires a low noise tube like a 7025, or equivalent low noise 12AX7. The overdrive stages (V2) require a durable 12AX7 that can tolerate the 350V plate voltage on V2b, referenced to its cathode.

Excellent support with very fast response - one of the best in the business.

I've been playing guitar for many years, and I'm also an Electrical Engineer.

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One thing that really surprised me about this amp is how close the SLO's overdrive channel circuit is to the "Orange-Normal" channel on the Mesa Dual Rectifier. The key difference being that the Mesa has a presence pad circuit on the Master Volume pot. This filters out the 'fizz' or 'insect-like' presence that is produced by the cascading gain stages. Adding this to the SLO makes the overdrive sound much better & more useful to me. The presence pad consists of a 22k-ohm resistor, coming off the Overdrive Master pot, in series with a 0.003uF cap to ground. You can download both the SLO & DR schematics for reference at: http://www.mif.pg.gda.pl/homepages/tom/schematics.htm

Also, consider reducing or removing the 120pF treble-boost cap on the clean/crunch channel's second stage. This cap comes after V1a and is in parallel with a 2.2M-ohm resistor. It adds a treble peak to the clean/crunch channel. I found that changing it to 39pF works well to offset miller capacitance without adding any peak in the response. Or simply remove it for a darker sound.

Both of these mods are simple & very effective. They are also easy to reverse. PLEASE DO NOT ATTEMPT ANY MODS UNLESS YOU ARE QUALIFIED TO DO SO - TUBE AMPS CONTAIN LETHAL VOLTAGES!!!
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I submitted a review of the SLO years go. I've had mine since winter 90-91. I still love this amp. For 14 years it's provided consistent amazing tones, especially in the crunch to lead/overdrive modes. No problems at all.

Today I was in a boutique music stored and played Bogner, Diezel, Peavey XXXX (not very boutique), Dr Z, Victoria, and a few others and I am sooooooo glad I have my SLO. Nothing comes close to it. Granted the SLO can't do things other amps can but when it comes to tube overdrive with harmonics, tightness, sustain, clarity, and relative transparentnesss where you can here the tonal differences of all your guitars and your playing nuances, well, it's pure joy.

And for those who say the lead channel is too fizzy or bright, play with the controls. Try mid and treble at position 1-2 (not oclock but position or knob value), prescence to taste, bass cranked, and slowly increase mids and treble to taste.

And with my stat I get pure Eric Johnson overdrive tones. I can't play as well as Eric but... And with the right cab and guitar you get pretty darn close to EVH but so much of Eddie's tone is his hands and not the gear.