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Hi Everyone,

I'm planning on rewiring my self-built amp head to Soldano SLO 100 Specs, I'm doing it to try and get more tonal versatility out of it, currently the preamp is configured like a Mesa/Boogie Mk 1, and the power amp is configured like that of a 50 Watt Marshall, as it is, I'm getting a good clean sound out of it, but I don't get much tonal variation when I'm in Hi-Gain mode, and I've managed to work out why....


A Mesa/Boogie Mk 1 Preamp is basically a Fender circuit with an additional tube gain stage tacked on the front end, when it is running in clean mode, the guitar signal get's amplified by 1 12AX7 gain stage before it gets to the tonestack, the tonestack appears to lose some signal due to the 10K Mid control, from the tonestack the signal get's amplified by a second 12AX7 tube gain stage which feeds a third gain stage through a resistive divider made up of a 220k resistor and a 2M2 resistor, the 220K resistor is bypassed with a 10pF capacitor, this lets some highs through to the fourth 12AX7 gain stage, from the fourth gain stage the signal goes to a master volume control and then on to the power amp....

When you plug your guitar into the high-gain input,this switches in an extra 12AX7 gain stage and an extra volume control, as you turn this volume control up, the signal overdrives the next gain stage producing distortion, the signal is fed through the tonestack as before, as we increase the volume control that's after the tonestack, the two proceeding gain stages heavily clip the signal so that no matter how we tweak the tonestack controls, the end result is a squarewave, this I believe, is the reason why I am not getting much tonal variation,I need to shift the position of the tonestack so that it can work more effectively to control the tone of the distortion I'm getting, so that inspired me to try rewiring the amp to Soldano SLO 100 Specs....

Below is a pic of my Amp Head as it currently is.....

Hi drnormis,

I don't go for the, I'm gonna mod this into that by swapping a few components. My guess is unless you go the whole circuit it will leave you more confused. Those SLO Amps need to have the whole EFX setup as *that* forms part of the nature of them. Sure mod it but don't expect success if only doing part of it.

All these Amps tend to suffer tone loss.
Old Marshalls where a classic in this regard when cranked the tone controls where hardly working. They basicly had one tone so you loved or hated it and moved on. Quite frankly I see no point in rows of triodes to attain certain sounds.
Sure it can be done but it's an expensive exercise and at the end of the day most of it can be done with pedals or outboard devices.

It's only the power tubes/output section of a Valve Amp you need to keep. Having run the guanlet of building Valve Amps (long story I won't bore you with) I ended up with reverting back to one of my first Valve Amps which is a 2 knob Valve unit,, one Ax7 preamp,,, all the rest is done via simple cheap SS outboard gear.

I have no doubt that my simple setup has more tonal variations than Wanker Brand name gear worth $$$ more.
I've used my setup next to some big names and I'm wanting for nothing.The thrash/speed metal tone that is now so popular is just tone shaping and darn hard to do if you are not a Valve guru.

Again far far cheaper to do that with *Off Board Gear* than trying to trick up an existing circuit.

The modern music sound is ALL Preamp fuzz anyway and triodes fair only marginally better than SS fuzz so why would you waste the money.

All this tone nervana wank is actually quite simple if you grasp what is actually happening. You can spend $ thousands in this game and get nowhere but understand a very basic principal and you will have more tone than you ever dreamed.

And Apparently I'm not alone;
http://www.amptone.com/truesecretofamptone.htm This will give you the basics.
A snippit;
""It's a shame that most guitarists try all sorts of things other than the secret weapon that gets straight to the point:
the eq>dist>eq pedal chain, which you can put before any guitar amp""

My setup is all home built and for my Wanker SLO 100 tone control I use a HiFi Realistic Graphic EQ,, S/Hand cost me $8
Is it any better than a real one? proly not but in a live pumping *real venue* believe me no one will notice.
I've played live against Super Reverbs, Cyber Deluxes,, Carvin Legacy's not to mention all the redneF Dumblux's.

If you just can't live without Valves then pop in a Schematic of your amp along with the mods you intend and I have no doubt that with all the talent here you will get some great advice.

I can give you a 3 knob outboard tone control that will make your Amp tone stack look and sound like the cheap toy that it really is.. Any interest then let me know.

Tone control is not 3 knobs on the front panel *It's the Amp system as a complete whole*.
That said,, bear in mind that One part in the wrong place and you are back to crap sound.
Cheers, Phil.

phatt wrote:Hi drnormis,

I don't go for the, I'm gonna mod this into that by swapping a few components. My guess is unless you go the whole circuit it will leave you more confused. Those SLO Amps need to have the whole EFX setup as *that* forms part of the nature of them. Sure mod it but don't expect success if only doing part of it.

All these Amps tend to suffer tone loss.
Old Marshalls where a classic in this regard when cranked the tone controls where hardly working. They basicly had one tone so you loved or hated it and moved on. Quite frankly I see no point in rows of triodes to attain certain sounds.
Sure it can be done but it's an expensive exercise and at the end of the day most of it can be done with pedals or outboard devices.

It's only the power tubes/output section of a Valve Amp you need to keep. Having run the guanlet of building Valve Amps (long story I won't bore you with) I ended up with reverting back to one of my first Valve Amps which is a 2 knob Valve unit,, one Ax7 preamp,,, all the rest is done via simple cheap SS outboard gear.

I have no doubt that my simple setup has more tonal variations than Wanker Brand name gear worth $$$ more.
I've used my setup next to some big names and I'm wanting for nothing.The thrash/speed metal tone that is now so popular is just tone shaping and darn hard to do if you are not a Valve guru.

Again far far cheaper to do that with *Off Board Gear* than trying to trick up an existing circuit.

The modern music sound is ALL Preamp fuzz anyway and triodes fair only marginally better than SS fuzz so why would you waste the money.

All this tone nervana wank is actually quite simple if you grasp what is actually happening. You can spend $ thousands in this game and get nowhere but understand a very basic principal and you will have more tone than you ever dreamed.

And Apparently I'm not alone;
http://www.amptone.com/truesecretofamptone.htm This will give you the basics.
A snippit;
""It's a shame that most guitarists try all sorts of things other than the secret weapon that gets straight to the point:
the eq>dist>eq pedal chain, which you can put before any guitar amp""

My setup is all home built and for my Wanker SLO 100 tone control I use a HiFi Realistic Graphic EQ,, S/Hand cost me $8
Is it any better than a real one? proly not but in a live pumping *real venue* believe me no one will notice.
I've played live against Super Reverbs, Cyber Deluxes,, Carvin Legacy's not to mention all the redneF Dumblux's.

If you just can't live without Valves then pop in a Schematic of your amp along with the mods you intend and I have no doubt that with all the talent here you will get some great advice.

I can give you a 3 knob outboard tone control that will make your Amp tone stack look and sound like the cheap toy that it really is.. Any interest then let me know.

Tone control is not 3 knobs on the front panel *It's the Amp system as a complete whole*.
That said,, bear in mind that One part in the wrong place and you are back to crap sound.
Cheers, Phil.

Hi Phil,


You have some good points there, and I myself have said in another forum thread that it is easy to add more 12AX7 tubes, but very hard to get a good tone out of them, so I'm aware of that, my intentions are to implement the complete SLO 100 preamp, including the FX loop, I've got the complete Schematics here with me, and I have had a good look at them, the Power Amp section in my amp Head is similar to the SLO 100, except that it uses a couple of 6L6 Power valves, whereas my amp Head uses a couple of EL34 Power Valves, I already have a couple of spare 9-pin valve sockets amongst my bits and pieces, I don't think it's going to cost me much as I also have a 50W EL34 Output transformer too...

I'm not trying to go for tone nirvana, just trying to make the amp a bit more tonally versatile, but I do appreciate your advice since it is making me think about this, I'll let you know how it all goes.....

make sure you head over to http://www.slocloneforums.com/ and have a good look around too.
there is a wealth of soldano based info there!

dellamorte wrote:make sure you head over to http://www.slocloneforums.com/ and have a good look around too.
there is a wealth of soldano based info there!

Thanks mate, will do...

Okay... Time for some updates......

I went over to the SLO Clone website and downloaded/printed-out some schematics, that website has proven to be really useful to me by the way, and I've made some progress on my amp rebuild.

I've decided that, since my amp head already uses two EL34/6CA7 Output Power-Pentodes, I'm going to re-build my amp as an SLO-50, I managed to scrounge 5X 9-pin Tube sockets for the re-build, and I only had to make two extra holes in the chassis for them, I also made one extra hole in the back panel for the FX Loop In/Out sockets (there was already one hole that had a pot mounted in it), and two extra holes in the front panel for the extra control pots, this gives a total of 9 control pots all-up, one of the extra pots is for the presence control, the other is for the Depth(Resonance) control.

I also replaced all the heater wiring with some Black Heavy-Duty 7.5Amp rated wire, yeah I know it's a bit over-rated for the job, but it should work fine.

Now, according to the Power-Supply schematic, I needed a total of 6X 200uF/300V Electrolytic Capacitors, the closest ones I can get from Jaycar Electronics are 100uF/400V Electrolytic Capacitors, so, I may need to buy more of them to make up the needed capacitance, if I put two 100uF caps in parallel, I'll effectively have a 200uF/400V capacitor.

I was never really happy with my amp's power supply design, and always thought that it needed beefing-up, so that's what I'll do, I think I can still use my current power transformer since the HT winding is rated for 200mA, and that's what's needed for the SLO-50 version...

I've gone through both the main and power supply schematics and compiled a list of parts that I need to buy to build all the circuits.

I'm thinking of building the circuits on some SRBP FR2 0.1 inch perfboard, which I happen to have ten 6inch X 2 and 3/4 inch sheets, I was a bit concerned about how much DC voltage these can handle, so I did some internet research, from what I've read, the SRBP material used to make these seems to be able to withstand up to about 740V DC, but I may be wrong, I've included a pic to show what the perfboard sheets look like

And for those who're interested, here's a pic of the amp on my workbench, with it's chassis temporarily put back in it's wooden frame...

I just found this:

http://www.ampbooks.com/home/classic-ci ... -preamp-1/

Thought it might be of interest?

rackham wrote:I just found this:

http://www.ampbooks.com/home/classic-ci ... -preamp-1/

Thought it might be of interest?

Sure is of interest to me, thanks for that, I've bookmarked the website.... cheers....

Hi Dr Nomis,

All Soldano designs, either 50 or 100 watts and some preamps, have in common a particular gain stage that uses a 39K resistor, as you can read in this link: http://www.ampbooks.com/home/classic-ci ... -preamp-3/

Even in a design that Yamaha has bought for his models T 50 and T 100, designed both by Soldano, this same approach also was used.

It's a tube stage that produce a very distorted output waveform, but not have too much gain so the noise floor isn´t increased severely, and has a good tonal quality.

Looks to be the fire stamp of this designer...

Cheers,
Jose

ppluis0 wrote:Hi Dr Nomis,

All Soldano designs, either 50 or 100 watts and some preamps, have in common a particular gain stage that uses a 39K resistor, as you can read in this link: http://www.ampbooks.com/home/classic-ci ... -preamp-3/

Even in a design that Yamaha has bought for his models T 50 and T 100, designed both by Soldano, this same approach also was used.

It's a tube stage that produce a very distorted output waveform, but not have too much gain so the noise floor isn´t increased severely, and has a good tonal quality.

Looks to be the fire stamp of this designer...

Cheers,
Jose

Thanks Jose, I actually had a good read through of that article, I've got more of an understanding of how the circuit works from reading it, quite interesting too...

Peavey use the same "trick" in their 5150 model AND Randall Smith uses it in his Messy Dual Rectum frier.
Fender also uses it (10k though) in their Protube Custom shop twin amp.
Engl doesn't use it though
bajaman

ps: it sounds awful without the following gain stage

bajaman wrote:Peavey use the same "trick" in their 5150 model AND Randall Smith uses it in his Messy Dual Rectum frier.
Fender also uses it (10k though) in their Protube Custom shop twin amp.
Engl doesn't use it though
bajaman

ps: it sounds awful without the following gain stage

Cheers bajaman, I went to the SLO Clone website and downloaded a PDF of the schematic, and made a hard copy printout of it, I'm going to do a complete circuit build from the schematics...

It seems that the basic architecture is a popular design amongst those manufacturers.....

One question, do you know for sure if FR2 SRBP Perfboard can withstand the high DC voltages without breaking-down?, just want to make sure that it's safe to use, I've got an Audio Express magazine that has an article in it for building a Tube Hi-FI Amp that uses 4 KT88 Tubes, and some of the circuitry is constructed on perfboard...

Thanks in advance mate...