My first step into building pedals. DIY Carvin Legacy Driver.

[briandress]

Hey guys.

I want to build a tube preamp because I can't actually afford these 12ax7 boxes that are on the market. It would also be super cool to learn how to apply my electronic skills towards the guitar fx industry...maybe even bring some cool stuff to my fellow local broke musicians lol.

So looking at the tube stuff makes me think that to get a real tube sound we need to work with high voltage. I am a bit rusty on my skills so I want to work up to that. I have seen some "starved plate" stuff but thought maybe it would be more prudent to start with some transistor work just to knock the rust off.

So I am looking around and found some threads on the Carvin Legacy driver and thought to take a swing at that. In reading the schematic I have a few questions.

First off, if there are any resources on how to actually produce a parts list from a schematic and how to learn how to lay it out that would be helpful.

I have attached the schematic I found if you guys are open to helping me learn what I need to put together to build this.

I assume "Input" would be a jack right?

"Volume 1" "Bass" "Mid" and "Treb" "presence" "drive" are all pots right?

cant quite seem to find where the output is here.

Thanks for your help guys. I will be taking extensive photos of the build process so maybe it will be helpful for new people like me.

[EBK]

I assume "Input" would be a jack right?

Sort of.  Typically, you would wire the input to a stomp switch so you could bypass the effect with your foot.  There are plenty of resources out there.  I'll dig up a link if no one else beats me to it. 

"Volume 1" "Bass" "Mid" and "Treb" "presence" "drive" are all pots right?

yes.  There are also four trimpots on that schematic.

cant quite seem to find where the output is here.

middle terminal of your volume pot here (unlabeled, but there is a dot there....)

[briandress]

Hey cool. Thanks for the input. I am going to try to put together a list of parts I need. I am trying to find a place that has everything in one place. What vendors do you use to source parts?

[briandress]

Ok so some parts

A500k "Drive" is a 500k A style potentiometer?
A25k "Mid" is the 25k A style Pot for Mids?

Not sure what these B1Ms are

or the "Gates" are these like and and nand gates?

[EBK]

A and B refer to the taper of the pot.
A is audio/log taper.
B is linear taper.

So, B1M is a 1 megaohm linear taper pot.


The gates are one terminal of a JFET (junction field effect transistor).  The other terminals are source and drain.  You can try 2N5457 JFETs....

[EBK]

Hey cool. Thanks for the input. I am going to try to put together a list of parts I need. I am trying to find a place that has everything in one place. What vendors do you use to source parts?

If you're in the US, I'd suggest buying everything from smallbear, especially since this is your first build.  I typically source my parts from Smallbear or Mouser. 

smallbear-electronics.mybigcommerce.com

www.mouser.com

You might also consider a kit build to get your feet wet.  There are tons of great kits out there.  Actually, I'd very highly recommend you do this and save that schematic for a future build, but it depends on how confident you feel, and whether you enjoy the challenge of debugging too.

[briandress]

You might also consider a kit build to get your feet wet.  There are tons of great kits out there.  Actually, I'd very highly recommend you do this and save that schematic for a future build, but it depends on how confident you feel, and whether you enjoy the challenge of debugging too.

thanks for the rec there. Will totally check out those suppliers. I am so shocked that with most of the components in a cart (and buying resistors in sets of 10 lol) only has come up to about $5 so far. This is incredible to me. What savings.

I won't go with a kit. Part of the fun for me is sourcing the components. I do have extensive experience with pcbs and RF circuits. I was IPC3 certified technician but at my job they had super powerful RF powered soldering stations and great tools making the job so easy. I will probably pick up a weller LMAO.

What kind of iron are you using? I never had to purchase one for myself.

[briandress]

oh hey what type of caps and resistors do you recommend?

I see metal film or carbon film resistors. 1/4 W, 1/8w, 1/2 w etc


lots of Cap types. electrolytic, silver mica, etc.

Is there a difference in tonal quality with these components? Are they just different like apples and oranges or is it more of a quality difference?

[EBK]

thanks for the rec there. Will totally check out those suppliers. I am so shocked that with most of the components in a cart (and buying resistors in sets of 10 lol) only has come up to about $5 so far. This is incredible to me. What savings.
I won't go with a kit. Part of the fun for me is sourcing the components. I do have extensive experience with pcbs and RF circuits. I was IPC3 certified technician but at my job they had super powerful RF powered soldering stations and great tools making the job so easy. I will probably pick up a weller LMAO.

Ah, I see. 

If you really enjoy sourcing your own parts, Mouser will give you millions of choices.  Smallbear has done much of the homework for you and stocks the stuff you would specifically want for building pedals.  Prices are generally similar.

What kind of iron are you using? I never had to purchase one for myself.

I personally use a Hakko FX888D.

[briandress]

some of these caps really are not clear as far as their values are concerned.  like a 47 is 47 farads?

.01 is .01 farads?

i see 47 and .047 as well. are they definitely different?

[EBK]

oh hey what type of caps and resistors do you recommend?

I see metal film or carbon film resistors. 1/4 W, 1/8w, 1/2 w etc


lots of Cap types. electrolytic, silver mica, etc.

Is there a difference in tonal quality with these components? Are they just different like apples and oranges or is it more of a quality difference?

I'd recommend 1/4W metal film 1% tolerance for resistors.
The caps with the plus sign next to them in the schematic are polarized electrolytics. 
For the other caps, in general go with some type of film cap wherever possible.  For tiny values (in the pF range), use ceramic caps in film caps are unavailable.

As far as the tonal quality, opinions will vary wildly.... 

[EBK]

some of these caps really are not clear as far as their values are concerned.  like a 47 is 47 farads?

.01 is .01 farads?

i see 47 and .047 as well. are they definitely different?

That schematic could use some improvements.  For caps without units, they are in microfarads.

47 is a 47uF electrolytic cap.
.047 is a .047uF (47nF) film cap.
Definitely different.

[briandress]

some of these caps really are not clear as far as their values are concerned.  like a 47 is 47 farads?

.01 is .01 farads?

i see 47 and .047 as well. are they definitely different?

That schematic could use some improvements.  For caps without units, they are in microfarads.

Ok maybe a different schem is in order


Sent from my iPhone using Tapatalk

[EBK]

I am so shocked that with most of the components in a cart (and buying resistors in sets of 10 lol) only has come up to about $5 so far. This is incredible to me. What savings.

If you source your parts through Mouser, definitely pay close attention to those price breaks.  Occasionally, I've needed only 5 of something, but found 10 to be cheaper in total (i.e., not just cheaper per unit). 

Before you know it, you'll be up to your eyeballs in tiny plastic bags those parts come in.   

[briandress]

I am so shocked that with most of the components in a cart (and buying resistors in sets of 10 lol) only has come up to about $5 so far. This is incredible to me. What savings.

If you source your parts through Mouser, definitely pay close attention to those price breaks.  Occasionally, I've needed only 5 of something, but found 10 to be cheaper in total (i.e., not just cheaper per unit). 

Before you know it, you'll be up to your eyeballs in tiny plastic bags those parts come in.   

You know as I look at these schematics more this doesn't seem all that difficult as long as you get the right components. I might even jump right into a 12ax7 build


Sent from my iPhone using Tapatalk

[briandress]

this looks just as easy to put together.

[EBK]

You know as I look at these schematics more this doesn't seem all that difficult as long as you get the right components. I might even jump right into a 12ax7 build

Makes me think of this quote:
"It's easy to play any musical instrument: all you have to do is touch the right key at the right time and the instrument will play itself." -- Johann Sebastian Bach

[briandress]

You know as I look at these schematics more this doesn't seem all that difficult as long as you get the right components. I might even jump right into a 12ax7 build

Makes me think of this quote:
"It's easy to play any musical instrument: all you have to do is touch the right key at the right time and the instrument will play itself." -- Johann Sebastian Bach

if i put the components in the right place it will work on its own lmao

[EBK]

If you jump into a tube build, much of what I recommended component-wise may not apply.... 

[briandress]

i can definitely understand that! see my ultimate goal is a tube preamp like the two notes le preamp series. and then to use a cab simulator for DI, either through an interface and PC or through a two notes torpedo cab or similar pedal that loads impulse responses.

the le preamps are really cool two channel preamps. They run at high voltage and are wicked cool. but pricey as well. so I am gonna just make one lol