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Author Topic: So you need a preamp - here are your options  (Read 49295 times)

joecool85

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So you need a preamp - here are your options
« on: April 25, 2006, 08:47:57 PM »
1. Line out from your amp
2. Build a preamp
3. Buy a preamp

I know it seems basic, but it is important to remember.  Just a power amp is not a guitar amp.  Not even close.  You need a preamp not only for tone, but also to boost the signal so you can get full potential out of the power amp.
Life is what you make it.
Still rockin' the Dean Markley K-20X
"New" amp: Fender Frontman 25 DSP (FM25DSP)
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Fixr1984

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Re: So you need a preamp - here are your options
« Reply #1 on: June 18, 2006, 12:06:59 AM »
Would something like this be useable. Or is a 9v powered unit
not enough output to be useable.
http://aronnelson.com/gallery/Mihkels-layouts/MarshaValveTube

Is there a good DIY preamp? GGG and Tonepad show some projects as a preamp
but they are really just a booster. That couldnt be used right?

el mo

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Re: So you need a preamp - here are your options
« Reply #2 on: June 18, 2006, 04:54:31 AM »
hi,
i wouldn't say that any project couldn't be used per se. if it works always depends on the input sensitivity of your power amp and, to a degree, on the supply voltage of your circuit;

many of the projects at www.runoffgroove.com can be converted to being good preamps
especially if you run them on 18v or 30v.
there are some useful links in the schematics section of the forum as well,for example
under " various schematic websites"

DreamSeller

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Re: So you need a preamp - here are your options
« Reply #3 on: June 18, 2006, 05:19:50 AM »
If I use a flipster as A preamp on a LM3886 Poweramp, What is the best voltage to run it at, I would need a seperate transformer wouldnt I?

Would It have to be a toroid or will a normal transformer do?
 
-Dream
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joecool85

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Re: So you need a preamp - here are your options
« Reply #4 on: June 18, 2006, 07:31:03 AM »
You can use power off the other transistor, but its not really recommended, and its easier with a separate one.  A regular CT transformer should be fine.
Life is what you make it.
Still rockin' the Dean Markley K-20X
"New" amp: Fender Frontman 25 DSP (FM25DSP)
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DreamSeller

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Re: So you need a preamp - here are your options
« Reply #5 on: June 18, 2006, 09:02:18 AM »
Sweet I think that will be the go then, Can you add a mid pot to the flipster.

And does anyone know what the mid contour switch on the fender FM65R changes, It sounds way better with it on, I always use it

-Dream
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el mo

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Re: So you need a preamp - here are your options
« Reply #6 on: June 19, 2006, 07:20:28 PM »
you can add something like this ( sorry about the bad drawing )

make both caps something like10n or 15n. you could also use your favourite marshall/fender-style tonestack.

another thing: i guess the flipster is able to drive a poweramp easily with 9v; playing with different voltages
can be fun though because you can use it to fine-tune the way the preamp responds to picking and the volume pot of the guitar. there have been some complaints on other fora because some people felt that the ROG designs were not loud enough; i suppose that's partly because the speaker sim filter in the end is a little lossy.
« Last Edit: June 19, 2006, 07:21:43 PM by el mo »

DreamSeller

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Re: So you need a preamp - here are your options
« Reply #7 on: June 21, 2006, 11:36:15 PM »
Thanks a few questions though.

-Where would you put that mid control in the circuit

-What is the highest voltage the flipster can take

-Will this Run Off Groove design be loud enough for the purposes that I want to use it for

Thanks

-Dream
A Broken Clock Is Right Twice A Day
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Wynand

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Re: So you need a preamp - here are your options
« Reply #8 on: June 27, 2006, 03:55:15 AM »
"Would something like this be useable. Or is a 9v powered unit
not enough output to be useable."

I recon a 9V preamp is more than enough, depending on the gain of the power amp.

Let's take a power amp with gain of 22 (a lot of gain-clones use this).  Power rails of +-25VDC.

Maximum output voltage of the amplifier will be less than the rails, lets take 24 as an example.  With a gain of 22 we get 24V/22 gain = 1.09 V input signal for max voltage.

Now your preamp has 9V, If you use op-amps you'll get 4.5 volt rails.  Your output only needs do be 1V thus you have headroom of 3.5 volts depending on the op-amp.

This is all really simplified I know but it gives the idea

Wynand

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Re: So you need a preamp - here are your options
« Reply #9 on: June 27, 2006, 03:59:09 AM »
"Would It have to be a toroid or will a normal transformer do?"

There is no difference exept that the toroid is usually smaller than a normal El transformer.
Toroids also have a bigger inrush current.  In a preamp you won't be using a 300VA transformer so it's not a problem.

For a preamp the transformers are small enough to give you with both options open.

joecool85

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Re: So you need a preamp - here are your options
« Reply #10 on: June 27, 2006, 07:14:55 AM »
I wouldn't go with a toroid for a preamp simply because they are more expensive and also don't normally have ratings under 90VA or so, and you don't need anything that big for a preamp.
Life is what you make it.
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Bob N

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Re: So you need a preamp - here are your options
« Reply #11 on: June 27, 2006, 09:06:13 PM »
a 9v circuit is plenty big enough depending on it's design.... my DR Boogie and JCM800 emulators are more than enough to push my solid state DuKane 60 watt amp that I use from time to time, with no other preamp circuits at all... Matter of fact, I have to turn 'em down because they get to be almost too much of an input for the amp...

ildar

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Re: So you need a preamp - here are your options
« Reply #12 on: August 10, 2006, 06:54:15 PM »
At the moment I'm using a Thunderchief as an outboard preamp with a TW Mosvalve power amp. Drives it with no problem all by its lonesome. Put a booster or OD in front, and it becomes a monster. I've done the same with the ROG 18, even the Fetzer, and will soon have the English Channel up and running for the same purpose. I wonder about those who have problems with ROG circuits not being loud enough. I'm guessing the problem is with the way they try to use them (as stand-alone amps maybe?), or problems with their gear.
« Last Edit: August 10, 2006, 09:39:09 PM by ildar »

Dr.Beat

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Re: So you need a preamp - here are your options
« Reply #13 on: September 20, 2006, 04:55:52 PM »
I'm thinking I'd like to use an external preamp setup on the 3886 I want to build, but how would I go about this? Do I simply run my guitar thru the offboard preamp like i would a pedal, into the 3886 poweramp with another patch cable?

Also, how would I go about adding a line-out to my amp? I'd like to use it as a preamp until I can get the money and time to build a preamp.

joecool85

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Re: So you need a preamp - here are your options
« Reply #14 on: September 20, 2006, 06:13:23 PM »
Yup, thats exactly how you would use it.  As for the line out, it depends, what do you have for an amp?
Life is what you make it.
Still rockin' the Dean Markley K-20X
"New" amp: Fender Frontman 25 DSP (FM25DSP)
thatraymond.com

 

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