Guitar Amp Design / Build

[MJL21193]

In keeping with another current project (Stratocaster build) I'm building a guitar amp.
Many of the other aspects of it's construction have been decided and I have started by selecting the drivers (two Eminence Legend 1258) and building the box to house it all. Details on this to follow but first the issues that need attention: preamp design and power amp choice.

First, the preamp that I have put together with inspiration from Rod Elliott's design:

GUITAR PREAMP 1.pdf

Basically buffer, gain, tone, gain, buffer.

Room for improvement here? I'm new to this type of thing and any input would be greatly appreciated.

[Bone]

You might want to put a single pole switch above or below R14 to disable the diode clipping.

Tony

[teemuk]

The input buffer seems pointless and has a too low input impedance to begin with. You want input Z to be closer to 1 Megaohm, like in the second stage.

Overall, I don't like the Elliot's preamp design and there are several reasons for this. The clipping diodes are a joke because due to the large bandwidth of the preamplifier they will only develop annoying buzz and fuzz. The only decent tones you'll get from this preamp are clean ones. I would seriously consider ditching this design and taking a look at the preamplifier circuits in some of the guitar amplifiers you are fond of. Study them for a moment and you'll begin to realise how awful the Rod's design actually is for this kind of application.

[MJL21193]

Thanks Tony,
Good idea. Any others?

I thought about making the gain adjustable on the input buffer and make away with the hi / lo inputs. What do you think?

[MJL21193]

Hi teemuk,
In my usual haste to get things done, I overlooked other designs. I will take a closer look at some of the schematics I've found.

Any recommendations? Remember, I don't know any guitar amps and I don't even know how to play yet.

[nigelwright7557]

If your looking for harmonics in the design then consider a soft limiter.
This will give a range of tones similar to a valve amp in overdrive.

[MJL21193]

How about this one:

117.jpg

Gibson G50A. It has the features I want. It is mostly discrete but that isn't an obstacle.

[tinitus]

OK
Made me look at these one more time
http://www.guitarmusician.com/tradit...uitar-amps.php

[Wavebourn]

Hi John; if you design for a lead guitar you need a harmonic enhancer that makes sound brighter when louder, and softer when it decay.

Here is the main idea: Si diodes in feedback (Log. converter), Ge diodes after (Exp. converter). The pot is a pedal ("Expression"): push the pedal and get more drive.

[Terry Demol]

Originally Posted by MJL21193

In keeping with another current project (Stratocaster build) I'm building a guitar amp.
Many of the other aspects of it's construction have been decided and I have started by selecting the drivers (two Eminence Legend 1258) and building the box to house it all. Details on this to follow but first the issues that need attention: preamp design and power amp choice.

First, the preamp that I have put together with inspiration from Rod Elliott's design:

Attachment 142195

Basically buffer, gain, tone, gain, buffer.

Room for improvement here? I'm new to this type of thing and any input would be greatly appreciated.

I would forget the IC topology and do an all tube design.

If your preference is for heavily overdriven sounds then look at some of
the early Marshall master volume model schematics. If you are more of a
clean twang sort of guy then a Fender front end is the way to go.

I also recommend a spring reverb unit, these sound really great and if you
can stretch it a tremolo circuit as per early Fenders.

Good luck

T