Scratch build head(s)...

Have been pondering the idea for the past few months on doing a scratch build amp...

On the current wish list is 1/ all tube audio path design with 6L6 finals, 2/ 40 to 50W output, 3/ an EF86 clean input channel, 4/ a Marshall'esk crunch or Soldano'ish OD channel, 5/ possible tremolo, 6/ bass, mid, treble and presence controls, 7/ master volume control, 8/ effects loop, 9/ maybe a built in spring reverb, 10/ 4 and 8 ohm outputs, 11/ footswitch control of channel, and if fitted tremolo/reverb,

The physical building isn't the problem. What is the problem is the style of tone that would be most universally useful, by which I mean 'is a Soldano style OD through a Fender 6L6 type final worth listening to'? My gut says the EF86/6L6 combination will produce very interesting cleans, as will the near universally used 12AX7/6L6 combination will produce very useful Fender type crunch tones ... And other things like what frequencies should the tone controls be set around.. Fender or Marshal frequencies, or something else?

'Universally useful' is ambitious, probably too ambitious... but guidance through wonderful examples would be immensely helpful. Even loves or hates about existing amps can have a important role in how this one turns out ....

As a start I'm looking at a Fender Hotrod Deluxe style amp as the starting point and adding the EF86, and then tinkering the design from there... If it all works out then I might make a few of them and offer them for sale... ;)

Comments anyone???

I seem to remember reading somewhere that the Soldano SLO 100 came from the factory with 5881 power tubes installed, or I could be wrong, being an American made amp, it most likely also came fitted with 6L6 power tubes, and from studying the SLO clone schematic, the Soldano SLO 100 is basically a Hotrod-modded Marshall circuit, for the typical Fender/Marshall tonestack you could incorporate a toggle switch, or a rotary switch to switch in different capacitor and slope/resistor values to get either the Fender tonestack or the Marshall tonestack with the Marshall pot values, it should be possible to do so.

Fender Tonestack:

Treble Cap: 250pF

Bass Cap: 100nF (.1uF)

Mid Cap: 47nF (.047uF)

Slope Resistor: 100k

Treble Pot: 250k Log

Bass Pot: 250k Log

Mid Pot: 10k Log


Marshall Tonestack:

Treble Cap: 470pF

Bass Cap: 22nF (.022uF)

Mid Cap: 22nF (.022uF)

Slope Resistor: 33k

Treble Pot: 250k Lin

Bass Pot: 1M Log

Mid Pot: 25k Lin (or could be a Log).


Note that in a Marshall amp the tonestack is driven by a cathode follower, whereas in a Fender amp it is driven by a common cathode stage.

Without considering the technicalities what about considering one of Ken Fishers fabulous Trainwreck designs as a reference as well.

Take a look at some of Egnators designs too.

You should look in to the Soldano Lucky 13 as a reference. This is a dual channel with Fender tonestack on the clean channel and a hot rodded Marshall type of OD channel. It runs 6L6's in the power section. There is a guy on eBay that sells PCB's for these out of the Ukraine if you are willing to wait about three months for it to arrive. I have one that I am about 80% completed, I have a blank chassis that needs to be drilled out sometime over the next few weekends....

Ooooh.. Ahhh.... Soldano Lucky 13... Can you post a copy of the circuit here? A link to the circuit on the net?

I'm doing a search for the Soldano Lucky 13 schematics right now, so far haven't found anything yet.

Yeah Doc, I can find references and photo's of the Soldano Lucky 13, but nil circuit which for me provided it's drawn correctly gives the critical info to do anything as a tech.

Repair or bias or copy, the circuit is the key. Fumbling around without a circuit is simply asking for trouble.... Maybe Soldano want this amp to only be returned to the factory for maintenance. Sadly that kind of attitude doesn't help sales, particularly outside the USA ...

Interestingly, Roy, the guy I'm working with at the moment has earned himself a bit of a reputation fixing Stanton equipment.... Even people in NZ are sending him gear. That's alongside all the LG electronics stuff that comes to him from across the country. So it's not unheard of to have gear shifted to get to the fewer and fewer repair guys.
Our throw away society has developed a downside which is in the future on faulty gear if you paid more than $1k for it then it might get fixed under warranty, less than $1k and it will simply get replaced, and if the warranty is over then good luck finding anyone that has the skill or can get the parts to fix your item...
An example - Panasonic HDMI recorder with netflix etc for $850 at uncle Hervey's.... Warranty 12 months, unit is 15 months old and HDD died. Nil spare HDD's in Australia, Only 15 spares held in country of manufacture being Taiwan for $450 ea. Model is superseded, HDD is specific to the recorder and nil more to be made... Too bad if you're the 16th person in the WORLD with one of these recorders to have a HDD fail.!!.. and we all know how often that happens...

I would have to agree with you there Marcel, trying to fault-find and fix a piece of equipment without a clearly read-able circuit diagram is like trying to solve a mystery blindfolded....been there and done it lots of times in the past, I think a lot of these manufacturers are worried that other competing companies will steal their intellectual property, and profits by copying their product designs, that's probably why they're being coy with circuit diagrams, but as you say, it leaves us poor service techs in a bit of a lurch when we have to repair things.


The rationale seems to be going along the lines of deliberate "Planned Obsolescence" in order to keep making money, meanwhile electronic equipment that's deemed un-economical to fix ends up as e-waste, something that I reckon is not good for the environment we live in, there are some quite dangerous chemicals used in the electronics industry, as I'm sure you know, which is where the ROHS standards come into play.

The back door of any techs workshop has little regard for any well meaning ROHS standards...

Dead $8k plasmas stacked against equally dead $100 Kogan LCD's... it's all a little sad when we fill the tandem trailer with the un-repairable gear for the once a month trip to the dump. All too often there are 3yo TV's making the journey due to the failure of a single component that is not held in stock and no longer in production... and nobody wants to pay for or is setup to do the recycling that the community at large thinks is happening. It's no longer like the old days where a toolbox full of parts (most often tubes) could fix every electronic item in the house... The things in electronics that break are so vastly different from job to job. Over the last 6 months I can count on one hand the number of times where the same exact part was used to fix more the two different jobs. I mean that we can get 5 Samsung TV's in for repair, and all can have the exact same fault, yet due to changes during manufacture maybe only 2 will use the exact same item to be fixed.... Did you know there are at least 4 different versions of the Playstation IV and not including production/manufacturing changes all have totally incompatible electronics inside...

Tube amps make a tech's life so much simpler...

wow, that's a real eye opener Marcel. I suppose keeping corpses for parts scrounging is out of the question with so many variables.
(Sounding like the Franken lab now)

We scrounge a few things that we think have a high probability of being useful.. But the workshop is only so big, and rent for a bigger place is not available....so most of the truly dead stuff goes to the dump..

Yeah, that $8k 4yo 85" plasma.... we could trick it to light up and the picture was great, but the CPU that controls the set had let go of the magic smoke inside so it didn't respond to the remote control. No replacement CPU board available due sold out months earlier.... Very sad to see it go, but very exhilarating giving it the 'Wun-too-heave-ho' at the dump...

Quote:

---

Originally Posted by Marcel

The back door of any techs workshop has little regard for any well meaning ROHS standards...

Dead $8k plasmas stacked against equally dead $100 Kogan LCD's... it's all a little sad when we fill the tandem trailer with the un-repairable gear for the once a month trip to the dump. All too often there are 3yo TV's making the journey due to the failure of a single component that is not held in stock and no longer in production... and nobody wants to pay for or is setup to do the recycling that the community at large thinks is happening. It's no longer like the old days where a toolbox full of parts (most often tubes) could fix every electronic item in the house... The things in electronics that break are so vastly different from job to job. Over the last 6 months I can count on one hand the number of times where the same exact part was used to fix more the two different jobs. I mean that we can get 5 Samsung TV's in for repair, and all can have the exact same fault, yet due to changes during manufacture maybe only 2 will use the exact same item to be fixed.... Did you know there are at least 4 different versions of the Playstation IV and not including production/manufacturing changes all have totally incompatible electronics inside...

Tube amps make a tech's life so much simpler...

---

I didn't realise this was the case, though it explains why so often the few friends I have who do try to get things repaired cant manage to.

It is a sad story... An unseen by-product of mass production combined with built in obsolescence and a public community with a fast growing 'throw away' mindset.

To add insult to injury there is an association that most Australian and NZ based TV/microwave repair guys are members of... 10 years ago membership was well over 3000 individuals/companies, but today the number is fast going South of 400... I've never been a member as fixing domestic TV's and microwaves has up until now not been part of my skill set, and I'm still not sure if it ever will become a factor in my career...

Oh, and I got reminded today that there is actually 6 different incompatible versions of the PlayStation IV....not the 4 versions I had said previously...

We have an Asian guy local to us that repairs pretty much anything, always got guitar amps and other musical gear in there along with TVs etc.

I do hope he stays in business for the foreseeable future because the local music community depends on him and his prices are most acceptable

Attachment 25069
here is a really crappy hand drawn version of the Lucky13. I have been using this as a basic reference for my build.

Certainly a bucket load of gain in the OD channel on that Lucky 13 tiltbell...also quite a bit of tone shaping in each stage too. As I'm looking to generaly build a Fenderish clean amp I'm not sure I want a Soldano tone that much as to add an extra stage or three, but others may see than need differently...

I did lots of amp building years and years ago with not too many actually working... duh! Though the ones that did tended towards being simple and over the years I've kinda realised why and essentially it's, for me, come down to patience and not letting ideas get ahead of curiousity and ending up with incredibly complex builds where the amount of potential tweaking to get it right would send me straight to frustration land.

Anyway, that's my story, sad but true, and I'm thinking very seriously about hauling all the gear out, I managed to sequester quite a load of choice gear, and going back in. Now that I am contemplating doing it again I'm going to make it easy on myself and what that mostly means is driving smaller amps harder in the output section because it seems that where the really nice sounds are. 6V6's, el84's etc.

On one of my very last amps, which sounds suspiciously like yours, I kinda designed this system whereby each tube in the preamp section had it's own little tagboard style etched circuit board upside down so I could solder in and out resistors and caps way easy. I had them upside down so I could read the circuit real easy and also test voltages as well.
Attachment 25105
This isn't the specific amp but a much smaller one where I used the etched board procedure as I knew such weird little radio valves would need lots of tweaking to get right... though I never got around to it.

Hi Artyone... I've seen that build method often, using small PCB's to build up to a much larger project.

There is method to the madness of putting the components on the track side of the PCB, and quite often in the SMD arena that is the only way to get the job done. A few years ago I was involved in repairing gear that operated at 10GHz range which had double sided and multi layer boards for the sections that worked below 1GHz and single sided teflon/Brass PCB boards for everything above 1GHz which made life as a repair tech so much easier.

On my tube amp builds I tend to stay away from PCB's preferring instead to only use tag strips. It's seriously old school, not suitable for any kind of mass production, and easily filled with lots of wiring errors, but I like the results and I consider it to be the real 'hand wired' art form .... I can see a lot of me in every tag strip build that I don't see in a PCB or turret board based build. As the photos show even in my AC18W build that used two of one type of turret board both of these turret boards were treated as if they were only slightly more than glorified tag strips. The one big advantage that PCB and turret boards have is that they can be built to a formula, a preset construction plan that is executed in production stages which of course is ideal for mass production.

On a transistor/FET/IC build the only way to go is using a PCB. I'm hopeless at making them so it tends to be the 'pre made by others' variety that I tend to build.

In the photos are a partially complete AC18W (EL84) build that used a type of turret board as tag strips, and the 2203 clone (EL34) build that uses only old school tag strips.

This EF86/6L6 amp will get built similar.... actually, due to cost constraints I'm giving serious thought to rewiring the 2203 build and using that chassis as the basis for this "new" amp.

Cool Marcel, I did lots of that too, tagboard, and basically just found it cheaper and more kinda non linear I guess to etch my own boards.

I suppose when the builds sorted and works it's a easier way, the tagboards, but if it's work in progress all those places where two resistors and maybe a signal cap are all bent in and soldered... they're a bugger to change. That's all, each to his own bro!

One thing I might do, this time around, is actually shape copper foil over wooden molds and then glass it to make my own three dimensional curved and sculptural circuit boards...

3D sculptural boards... that would be interesting... I can't see much application for it in an amp build but my imagination is certainly having a party using the technique with a bunch of coloured LED's.... ;)

Just for interest, and a carry on from an earlier post in this thread.... we only took a small trailer of "throw a ways" to the tip last Saturday.

A few plasmas, a dead OLED screen and a bunch of LCD's .... Electronics might be getting smaller but our fascination with bigger screens is endless....

It's amazing how much time you spend browsing catalogues looking for parts when doing a scratch build project. And then you spot something and your thinking takes a huge leap sideways and the need to re-visit every catalogue and some forums strikes again...

So, as it stands, my next scratch build, will be...
EF86 input pre-amp, with possible 12AX7 alternate switching (similar to a Morgan 20).
6L6 finals, most probably a 40W hot rod deluxe inspired formula.
Most probably a JTM45 style chassis...
Best price so far just for transformers and chassis is just a little over AU$400. Add to that tubes and every other knob, pot, resistor and capacitor.... I think I need to lay down for a while... (quietly strums acoustic while pondering options)....

Distracting myself from the amp build with YouTube... I happen by chance to watch that German Dude trolling that Canadian sound guy over the Line6 Spider V, plus a few of the Canadian dudes rants on certain gear.... And I couldn't stop myself from remembering what it was like for me as a budding young teenage guitarist in the late '70's and comparing that to what is available today.
Back then I had a solid state 5W (if that) Princeton amp with tremolo and a 8" speaker and it was great (Actually I still have it in my shed). It was mine and it made noise, electric guitar noise at that. Today, up against a Line6 Spider V it's crap, utter unadulterated garbage. Seriously why bother even turning it on type crap!! I was in the school band and had a school owned JC120 and a Fender Jazz bass in that rig that I got to take everywhere, but at home in my bedroom it was a 'cheapest in shop' Strat copy and the Princeton and that's what I learned on, and the teenage world I lived in was marvellous. I had all I needed and learned everything Beatles, Rolling Stones... etc..etc...etc... everything I could get my hands on up until the end of 1979 when I left my guitars at my parents home an set off for a career in the big bad world...
So after my time in the Air Force for a few years I did the roadie/sound guy touring thing for dozens of nameless bands plus that gig called Expo 88, got into commercial radio and worked a few shows with people like LRB, Warren Zevon and NoiseWorks... Jumped ship to TV and saw what Leilah, Lisa Miller and the Stefanovic brothers do off camera... and, anyways after many years in various professional arenas with the kids all having departed the nest here I am the last couple of years relearning what the 'guitar world' has to offer and I must honestly say that there is an unbelievable amount of good, great, and unbelievably fantastic gear around today, and the Line6 Spider V as a home bedroom practice amp is a far better stating point for a beginner than I ever had. Kids (and us oldies) learning guitar never had it so good...
I have to agree with Henning that it's not a gigging or studio amp (which upsets Glenn so much in that some people think they are studio grade amps) but it is a great starter amp to learn on ... As is the VOX VT, or the Katana or the Mustang, or any of the myriad of modeling amps... None are perfect yet for what they are they're great. Great tools to learn (or re-learn) on.
I don't understand though why some professionals get so butt-hurt when confronted with someone who is inexperienced. Some un-learned dude fronts up with what they think is their best only to be shouted down by the Pro for no other reason than a prejudice held by the so-called Pro... It may well be a well founded prejudice but there is nil reason to go nuclear about it. Or is it all just an act? An act of 'going postal' simply to score views....

You can go back to sleep now... My rant is over...

Nice rant Marcel and right on the money.

I actually stopped watching both those guys. One has become a "look at all my famous friends and watch my reviews on stuff I'm getting paid to promote" and the other is just an ego driven mucho fest aimed at 18yr old metal heads.
I will say it easy to get drawn into that rarified world of high end gear. I have a friend who runs a very successful mastering studio (Casey Barnes , Amy Shark) and I have learned NEVER to ask his opinion on gear. it usually goes something like "Oh yea, you can pick up a cheap one for 2 or 3 K", or "really you bought brand x? They always crap out on tour" Yea, but I play in my lounge room! He asked why the hell I bought a valve amp in this day and age...........

Yep, can totally relate to your comment there Dedman. I do watch quite a bit of content from both these guys and on some things they are exceptionally correct, but their presentation is all too often tainted to score views. Although there are exceptions I suppose the same could be said for most of those 'content providers' ...

As for tubes.... they have their issues, but damn there is nothing better in certain situations... The trick is in knowing which situations...

The mastering studio chap might have been referring to the drift of session musicians away from valve amps and to the good modern modelling amps like the Kemper, Line 6 helix and Fractal Axe units. Personally I'm still in favour of using real amps, but I don't need to play several types of music styles in a day, every day.

Actually Simon, I think the Canadian had a gut full of young kids coming into his 'Pro studio' with tiny practice amps to record Metal sessions, so in disgust and in a release of frustration put out a video of him destroying a Line6 spider using actual explosives at a firing range. He has since done similar to a Marshall Code25 by throwing it off a building and then taking to it with a sledge hammer. All done under the banner that neither is worth of being in a Metal type song....

The essence of the German dude was to rebut the Canadian and make a (pretty good) Metal type track mostly only using the Line6.

I will say that the videos were entertaining though at the same time very annoying... Anyone with nil brain can destroy something, but it does take a little of that something special to be able to truly create something. And in creating it if other people wonder and guess in how it was done then you certainly have something special in your grasp. There are few with ears so Golden that they through listening alone can tear apart any musical track and then advise the world the specifics on how each sound within that track came into existence. Most just listen and indulge in the experience....