Early '90's SLO mod or not to mod?

procos

Gold Supporting Member
Messages
5,348
I thought about selling my SLO but came to my senses. I have owned close to 6 or 7 SLO's over the past 10 years. I end up selling them and then always end up buying another one a few months after selling because I miss it. Have tried to use a Bogner XTC and XTC classic in it's place but just can't get that same tone. So I have decided that better just keep my SLO.

So mine is a 1992 and I love everything about it but I have the bass on 7 and still feel I could use alittle more bass. Once you start taking the bass above 7 it doesn't seem to add much. Also I'd like the OD channel to stay as thick as the crunch channel. On my SLO when I engage the OD channel some of the thickness from the crunch channel seems to disappear.

So I was thinking maybe if I send it to Soldano and have them add the Depth mod and Haynes mod it might address these issues. What do you think? I just wondering if it is a bad idea to have such an early SLO modded even if it is done by Soldano.

BTW here are my settings with my SLO most of the time. The numbers indicate the numbers on the dial(11 being the highest) not on a clock.

Normal switch
Crunch switch
Gain Crunch: 10
Gain OD: 5 1/2
Bass: 7
Middle: 9
Treble: 1
Master Normal: 4
Master OD: 4 1/2
Presence: 5

The reason I put the OD Master 1/2 higher is my Normal channel is louder on the same number for some reason. Really weird. If I send it to Soldano I am going to have them look at the masters to see what's up.

Thanks,

Chuck
 

stark

Silver Supporting Member
Messages
3,271
So mine is a 1992 and I love everything about it but I have the bass on 7 and still feel I could use alittle more bass. Once you start taking the bass above 7 it doesn't seem to add much. Also I'd like the OD channel to stay as thick as the crunch channel. On my SLO when I engage the OD channel some of the thickness from the crunch channel seems to disappear.

So I was thinking maybe if I send it to Soldano and have them add the Depth mod and Haynes mod it might address these issues. What do you think? I just wondering if it is a bad idea to have such an early SLO modded even if it is done by Soldano.
The depth mod messes with the feedback loop of the power amp. I personally don't like what the mod does to the bass. Turning up the amp for sure will fatten up the bass. Maybe an attenuator a couple of notches down will do the trick. NOS 7581'A's will get you a much tighter bigger bass.
On the one I had (93'), if I put all the knobs at 12'oclock, crunch switch on and bright off, the channels sounded basically the same with the lead channel having slightly more gain and vol. Newer one's I have tried had a huge difference between the channels when set this way. Preamp tubes can also have a big effect on differences between the channels. I would recommend not modding the amp. Clean unmodded amps are becoming harder to find.
 

procos

Gold Supporting Member
Messages
5,348
Thanks Adam. I have tried a bunch of different preamp tubes and didn't really hear much difference. Maybe I am putting them in the wrong slots. From what I remember looking from the front of the amp the 2 slots that matter the most are the first to from the left. I believe they are V1 and V2. I did try the attentuator trick today and it helped but not enough to put out another $350 for another Alex. I currently have my Alex dedicated to my Orangutan. Do you know do I have to rebias if I buy some 7581's? I know Soldano recommends Sovtek 5881's and I have a brand new pair in that have about 20 hours on them. I didn't have to rebias for those according to Soldano.

I agree with the modding because I was thinking the same thing just wanted some opinions.

The depth mod messes with the feedback loop of the power amp. I personally don't like what the mod does to the bass. Turning up the amp for sure will fatten up the bass. Maybe an attenuator a couple of notches down will do the trick. NOS 7581'A's will get you a much tighter bigger bass.
On the one I had (93'), if I put all the knobs at 12'oclock, crunch switch on and bright off, the channels sounded basically the same with the lead channel having slightly more gain and vol. Newer one's I have tried had a huge difference between the channels when set this way. Preamp tubes can also have a big effect on differences between the channels. I would recommend not modding the amp. Clean unmodded amps are becoming harder to find.
 

procos

Gold Supporting Member
Messages
5,348
Also I owned a '89 which I wish I wouldn't have sold that had KT66's in it and that amp smoked. The guy I sold it to then sold it and the guy who owns it now(who is a forum member) is well known for jacking the prices up on his gear. He has every right to do it and probably always gets what he wants but I am not willing to pay alot more for something I sold cheaper. I wouldn't mind owning a another SLO with KT66's in it. Those seem to fatten the tone up.

Chuck
 

fusionbear

exquirentibus veritatem
Platinum Supporting Member
Messages
10,864
Hello Chuck, another vote to keep the amp as is. The KT66's will fatten up the tone, but you will lose bottom end tightness. I also would vote for putting in the NOS 7581's. These will keep the bottom end tight.
 

stark

Silver Supporting Member
Messages
3,271
Do you know do I have to rebias if I buy some 7581's? I know Soldano recommends Sovtek 5881's and I have a brand new pair in that have about 20 hours on them. I didn't have to rebias for those according to Soldano.
You need to rebias with any tube swap. It's super easy, just get a bias-rite or something similar. Bias to 32ma and you are good to go. 5881's won't get you the bass you are looking for. The lack of bass you are feeling is a plus when you are cranking the amp with gain and you want to maintain articulate notes in the low register. Think Holdsworth or Van Halen with a big 4x12.
 

procos

Gold Supporting Member
Messages
5,348
I thought that as well but the guys at Soldano told me I didn't need to bias if I bought 5881's. If I buy the bias-rite does it give instructions? I have rebiased my Onyx but it has external bias jacks and a bias screw. Not sure how to do it inside the chassis.

You need to rebias with any tube swap. It's super easy, just get a bias-rite or something similar. Bias to 32ma and you are good to go. 5881's won't get you the bass you are looking for. The lack of bass you are feeling is a plus when you are cranking the amp with gain and you want to maintain articulate notes in the low register. Think Holdsworth or Van Halen with a big 4x12.
 

stark

Silver Supporting Member
Messages
3,271
I thought that as well but the guys at Soldano told me I didn't need to bias if I bought 5881's. If I buy the bias-rite does it give instructions? I have rebiased my Onyx but it has external bias jacks and a bias screw. Not sure how to do it inside the chassis.
With the Onyx all you need is a digital volt meter set to "ma". Turn the screw till it reads the number you want "32ma". You stick the probes into the jacks :drool. With the bias rite, you plug a tube into the socket then into the amp. Then the digital readout will show you "ma". You need to remove the chassis. The bias pot is a little wheel on the circuit board. Make sure you have a load "speaker" connected and the vol and master pots all the way down. It's really easy once you do it.
Weber Bias Rite Page
 

lespaul6

Senior Member
Messages
1,335
Treble on 1....I dont know, maybe you can play around with the eq settings and get the master up to 6..that is where the amp goes into a tight pushback with plenty low end etc. What amp(s) are you coming from? Sounds like you prefer darker voiced amps?
 

Jim S

Platinum Supporting Member
Messages
15,060
You need to rebias with any tube swap. It's super easy, just get a bias-rite or something similar. Bias to 32ma and you are good to go. 5881's won't get you the bass you are looking for. The lack of bass you are feeling is a plus when you are cranking the amp with gain and you want to maintain articulate notes in the low register.
:agree

I have three SLOs heads. One is stock and two have scoop and crunch modes. They range in year from 1990 to newer. That being said my opinion based on experience and conversations with Mike and Bill at Soldano:

  • DEPTH MOD: has no effect on tone when turned off; to my ears it's like it's out of the circuit. I only use it home and rarely. Live or recording it has never ever been on.
  • TUBES make a relatively mild to modest difference
  • SPEAKERS make a huge differeence (a thread on this was bumped last week yours truly)
  • CRUNCH channel never seemed to change for my ears as you have experience.
Also I'd like the OD channel to stay as thick as the crunch channel. On my SLO when I engage the OD channel some of the thickness from the crunch channel seems to disappear.
I am confused. YOu can only listen to one channel at at time.
Are you saying you turn the amp on and first playinto the CRUNCH and get sound A, switch to OD and back to CRUNCH and it sounds like B? It's not your years going back forth responding to different tones or volumes?
Seriously.
 

flcmcya

Member
Messages
3,431
Haynes mod is quick and easy to change back........my 4x12 is really bright but I just gave up an cut back on the treble like you rather than clip a cap......my 2x12 sounds way fatter just due to speaker choice so that too could be an option.......bias rite is the way to go ;)
 

joolzriff

Member
Messages
2,171
i have no problems w/ bass with my un modded SLO... we may all use different speakers here and play different music so advice only goes so far.
i would maybe turn my mids to 4 or 5 instead of your 9......treb 4.....bass 6.....pres 4 or 5
i love the jj 6l6's! and chinese pretubes with an OLD RCA in V1..
also use a soldano cab and a bogner cab w/ greenbacks...plenty bass fr a guitar
had a haynes mod in another slo i had and hated it,made the sound dull not crisp and that sucked on my neck pickup,made it all woolly,horrible.
as for the 2 channels sounding way different...try backing the gain down on the lead channel to 2.5 or 3 and that tends to just thin the gain a bit to match up w/ the normal channel a bit better and then adjust amp tone controls to fill her up again.....if u noticed the gain gets thicker and thicker the more u turn the pre up(not just more gain)...moving further away from the normal channels sound.you have yours on 5.5 and thats getting thicker

BY THE WAY i always have to chime in on a SLO thread...you gota keep em alive
 
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SgtThump

Silver Supporting Member
Messages
7,887
I'm on the other side of the fence from these other guys. I bought a new SLO with no mods and it lacked low end BIGTIME at home. It didn't sound good to me at all at lower levels. It was alot better with the band filling out the lows and stuff, but still not where I wanted it.

I got the depth mod on it and the amp rocked tons more for me. The depth mod somehow not only added low end, but also smoothed out the highs. In my opinion, that mod is much needed for the tones I like.

So yes, I highly recommend it. Judging from what you said in the original post, I think you'd like it.
 

SReynolds

Silver Supporting Member
Messages
1,662
I'm on the other side of the fence from these other guys. I bought a new SLO with no mods and it lacked low end BIGTIME at home. It didn't sound good to me at all at lower levels. It was alot better with the band filling out the lows and stuff, but still not where I wanted it.

I got the depth mod on it and the amp rocked tons more for me. The depth mod somehow not only added low end, but also smoothed out the highs. In my opinion, that mod is much needed for the tones I like.

So yes, I highly recommend it. Judging from what you said in the original post, I think you'd like it.
I had the same experience. I also recommend it. I'm pretty deep into SLO withdrawals at the moment. Played one for 3 years. The only amp that sounded so good I actually gave myself goose bumps.:beer
Now that's an amp.
 

JasonP

Member
Messages
135
That and you can put the depth pot in say the slave out hole if yours doesn't have it. It is also a very simple mod.
I personally would figure out what you want to change or add, take away and go from there. I willing to bet there is just one or two things that need to be changed and be worth it to you as this amp is your go to keeper amp.
 

Tony Foran

Member
Messages
7,557
Chuck, I just bought a Bias-Rite after all these years of setting the bias by ear and it's as simple as can be. As long as you are aware of the potentially lethal shock you could receive, if you happen to touch the wrong thing and know where the bias pot is located. I don't know why I've waited so long to buy one.
 




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