Building a high gain amplifier part 1: The preamp

This has been a long time coming and will be the last ever Soldano influenced amplifier that I build.

All I'm doing here is rebuilding my original amp with a few tweaks that I have found that I prefer over the stock circuit.

First up we will start with populating the preamp board with the smaller components as it is always best to do it in height order to stop things slipping out and looking messy later.

So here we have the bridge rectifier for the channel switching circuit. It is the smallest component of the preamp therefore it is done first. Please note the polarity markings as this is critical for correct operation. The PCB also has a silkscreen that matches the markings so it's pretty hard to go wrong here.

 

And now it's time to go onto the bulk of the preamp which is the resistors. I am not going to go through these one by one as it will just be lots of repetition and there are no polarities to be concerned with so just solder away! One thing to keep in mind is that some resistors have very similar colour bandings so take your time and make sure you match them correct values up with the silkscreen.

 

 

With resistors I usually use a lead forming tool to help keep things nice and tidy.

 

And here is a nicely formed resistor ready to be soldered in. 

 

I've added a few extra shots of the preamp just for reference as to what it looks like as you go along.

In this last shot you will notice that I have left R14 blank. This resistor is the Soldano signature move, the cold clipper. It determines when the lead channel saturates and the amount of gain on tap. My reasoning for leaving this blank is that I am going to add a front panel toggle with the stock value and a lower value so that I can switch between two gain voicings as and when needed.



 

 



 

From here we are going to go onto the small value capacitors. For these I choose silver mica caps just because I like the way they sound over ceramics. However a cheaper ceramic cap will do a good enough job also it just depends if you want to spend the extra 30p or so.

 

These capacitors are unpolarised so again orientation isn't important here.

 

 

 

The last step that I am going to cover today are the three electrolytic capacitors in the preamp for the B+ & channel switching parts of the circuit.

 

These three capacitors are polarised and you really want to make sure that you get these in the right way as it isn't pretty if you power up with them the wrong way. Electrolytic capacitors failing can be very messy and sometimes dangerous. See this video for a demonstration.

 

 

 



 

As you can see the polarities are clearly marked on these capacitors making the chances of an error during installation very minimal as the PCB silkscreen also marks the polarity.

 

That is all for today but in the very near future I will be finishing the preamp in a bit more depth and also the power amp in the next post.

 

After that things will get a lot more in depth and also move into a more step by step manner as things get a little more complex.

 

If you have any questions just leave a comment and i'll do my best to answer you.

 







Hello!

Just thought I'd introduce myself as a new contributor to this blog, and thanks to Toe-Knee for inviting me in.

I've been playing guitar and have been in bands for about 15 years now and in that time have done hundreds of gigs with both covers and original material bands. I'm also a trained Live/Studio Sound and Recording Engineer, so you could say I've been round the block a few times!

I'm nowhere near as knowledgeable as either Toe-Knee or Bob on the technical side and inner workings of amps or pedals but have in my time owned alot of and, due to my work in the studio, have come into contact with alot of different types and brands of equipment, so I think I have a pretty good ear and idea for combinations of things that will and won't work together.

Most of my contribution will come on the gear review side and I'll leave the more technical information to Toe-Knee and Bob!

Musically I'm pretty much in the 70s Rock, 80s Rock/Metal, 70s Punk and Blues side of things, even though I have been known to listen to some heavier stuff now and again, so my reviews will mainly concentrate on gear that fits into those types of genres.

Let us know if there's anything in particular you want to know about or want us to write about and we'll do our best to cover it.

Thanks!

Merry christmas.

Hey guys. This is just a very brief one now that things have calmed down somewhat.

You may have noticed that we now have a new banner thanks to one of our new contributors (more on that in a bit) We have also changed the URL to WWW.BACKLINE.TK the old one will still work for a little while but be aware it isn't going to last forever so update your bookmarks.

There will be further visual updates over the next week as well as some introductory posts from our new contributors.

Saying that I would like to welcome Brow & Demonikol to the ranks which should hopefully make things a little more steady and also spread out the posts over a wider range of equipment as we all play differing genres of music therefore use differing equipment to an extent.

I hope you all had a great christmas and that you have a fantastic new year!

HAGO!
Tony

The future of this blog...

I have a few things planned for the next few months after a fairly long absence. Here is a quick breakdown of the future plans and also some information on how I plan on approaching this blog after the new year.

Upcoming pedal builds
1776 Rubadub Digital Reverb - In Progress
Naga Viper Influenced Treble Booster - Jan 2013
1776 Multiplex Echo machine  - Feb 2013

Upcoming amplifier builds
SLO influenced rebuild - In Progress
Krankenstein influenced amp - March 2013

As you can see from the above list I'm hoping to get back into a regular cycle. My goal is to get at least one pedal build posted on here each month unless there is a more time consuming build going on such as an amp build then that will possibly cover two months or so but there will be regular updates.

Update 23/12/02
I have been speaking with Bob regarding the future of this blog and we have come to the decision that the blog is going to be expanded to cover a wider area of guitar related equipment and not just DIY projects.

In light of the above you can expect equipment reviews of production gear and also there will be a bit of a visual shake up and obviously a new name. Watch this space!

1776 effects Rubadub Reverb Build

Well it's been a bit quiet on the personal DIY front. I've just done a few amp builds for people but nothing that hasn't really been covered before.

However I recently got around to starting building a digital reverb using the Rubadub reverb PCB from Josh @ 1776 effects

This build is now completed but I haven't boxed it up yet so for now there are just a few in progress pictures at the bottom.

The circuit is really nice and sounds fantastic on clean sounds which is primarily what I wanted it for.

I wont be boxing this up until the weekend and still haven't decided on the graphics for it. If you have any suggestions please feel free to post a comment.

Here is a quick clip with some incredibly shoddy playing due to an injury of my fretting hand. I'll get some better ones up as soon as I can play without getting cramps in my left palm.

Here is one with just the resistors mounted. I didn't have one of the required values so used two resistors in parallel to get it where it needed to be.

And here we are with it mostly populated minus one electrolytic cap. These newer Belton reverb bricks are now small enough to fit comfortably inside a 1590b.