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Author Topic: What do you think of this hydrid preamp?  (Read 7282 times)

adamn

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What do you think of this hydrid preamp?
« on: June 08, 2010, 05:08:24 AM »
Found this hybrid preamp that run on 12v dc.Was think of building this for my DIY guitar amp project.
http://www.sugardas.lt/~igoramps/grass_preamp.htm
Sound clean on the sound clip for me.Was thinking to change the tone section to marshall tone stack.
The power amp section will be LM3886.
1.Was wondering,the cap c3 &c8 still needed, if i replace the tone section to marshall tone stack?
2.Should i add a gain between the tube?

Any help?

phatt

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Re: What do you think of this hydrid preamp?
« Reply #1 on: June 08, 2010, 09:28:59 AM »
Hi adamn,
              First Q/ Are you wanting clean,, inbetween rattle rock tones,,
or full on metal?

IMExperience, The valves are being wasted setup like this. :'(
My suggestion, Google *Mesa Boogie Vtwin schematic*

It will likely run on the 60 VDC you have and it's about the best tube preamp on the planet.

I only ever built the *Clean section* and of course it should obvious that you do not need all the extra stuff.
Makes for an easy project.

If the Vtwin schematic is hard to understand I can search through my old files and find the setup I built many years back.
Good on you for having a go at something that is not easy to do. :tu:
Phil.

Jack1962

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Re: What do you think of this hydrid preamp?
« Reply #2 on: June 08, 2010, 12:49:46 PM »
you may want to change the values of C3 and C8 but I would have caps there.
that 12ax7 should drive that or most any tone tank just fine.

adamn

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Re: What do you think of this hydrid preamp?
« Reply #3 on: June 09, 2010, 02:41:19 AM »
Hi adamn,
              First Q/ Are you wanting clean,, inbetween rattle rock tones,,
or full on metal?

IMExperience, The valves are being wasted setup like this. :'(
My suggestion, Google *Mesa Boogie Vtwin schematic*

It will likely run on the 60 VDC you have and it's about the best tube preamp on the planet.

I only ever built the *Clean section* and of course it should obvious that you do not need all the extra stuff.
Makes for an easy project.

If the Vtwin schematic is hard to understand I can search through my old files and find the setup I built many years back.
Good on you for having a go at something that is not easy to do. :tu:
Phil.
Thanks Phatt.I like to have the preamp in between of clean and rock.
Have search the wed for Mesa Boogie V twin.Look interesting for me.If it's possible to trouble you send me your file?
Your help is much appreciate.Thanks

adamn

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Re: What do you think of this hydrid preamp?
« Reply #4 on: June 09, 2010, 02:45:08 AM »
you may want to change the values of C3 and C8 but I would have caps there.
that 12ax7 should drive that or most any tone tank just fine.
Thanks Jack1962 for the advice. Will still build this preamp amp.It's a very simple amp for fun build.
Thanks again.

phatt

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Re: What do you think of this hydrid preamp?
« Reply #5 on: June 09, 2010, 10:15:38 AM »
Hi adamn,
Here's the schematic for my take on the Vtwin.

The Amp is long gone so don't hold me to exacts but I'm sure it won't take you long to find what works for you.

I deleted the optional bright cap (20pF) as the HiWatt Tone setup is already quite bright. If you are driving a SS poweramp then excessive treble will be harsh.

*Note the mistake* in the *Original Mesa drawing*
That being R24=270k is just insane,,, Try 27k, wink.

While bread board testing I found I did not need all the extra add on bits as it was built into a combo Amp chassis.
This makes it very straight forward to build.

The dirty channel was tested but frankly it sounded no better than some SS pedals.

Running this dirty channel Through to a Valve Amp may work better as a lot more high frequency hash is lost through some Valve Amp circuits but when driving into a SS poweramp you have to watch out for the dreaded diode hash. :'(
Upon reflection a Cab sim circuit *After* that part might have been the go when working into SS pwr stage.
No matter cause you want the cleaner sounds. :tu:

My Valve part ran on 240VDC so try it out with 60VDC and see if it works.
My guess is you may need closer to 100 VDC,, but hey if it works for you then go with it.

Re the tone part;
Look if you want to replicate an *Exact* tone shape then just drop the HiWatt tone but IME you won't find a tone stack as powerful as the HiWatt.
Even the fabled *Dumble tone* circuit with all it's fancy switches is no match. 

Though it's No better than fender or marshall for treble and bass the *mid cut* ability of HiWatt tone just eats ALL the others.
I've built and tested most of them (side by side test) so I do know how they perform in the real world.

No other passive tone circuit I know of can pull the mid notch like HiWatt.

Note; All these tone circuits need to be looking into a BIG impeadence and the FET circuit on your link *Can't deliver the goods* It suffers great losses.
(been there done that).

It seems like a good idea but it became obvious to me that a simple opamp buffer works far better and minimises any loss (and potential noise) at this *Critical point*.

So don't delete the buffer opamp after the tone stack otherwise you will run into lots of trouble and the circuit will be wasted. 

Have fun with it all, Phil.

Jack1962

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Re: What do you think of this hydrid preamp?
« Reply #6 on: June 25, 2010, 10:00:44 AM »
Great advise and a fine schematic , however I have a few Hiwatts and 1 Dumble and the HiWatt doesn't even come close to the tone of my Dumble.

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bry melvin

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Re: What do you think of this hydrid preamp?
« Reply #7 on: June 25, 2010, 12:39:15 PM »
Quote
No other passive tone circuit I know of can pull the mid notch like HiWatt.


Curious  if that included the on guitar circuit board and tbx  (Eric Clapton signature strat)

I build (or have built) all of my strat type guitars with that circuit

I've never used a HiWatt.

Yes I know that's an "active" guitar setup...just curious of the comparison if someone has tried.
« Last Edit: June 25, 2010, 12:41:49 PM by bry melvin »

phatt

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Re: What do you think of this hydrid preamp?
« Reply #8 on: June 26, 2010, 04:01:12 AM »
Quote
No other passive tone circuit I know of can pull the mid notch like HiWatt.


Curious  if that included the on guitar circuit board and tbx  (Eric Clapton signature strat)

I build (or have built) all of my strat type guitars with that circuit

I've never used a HiWatt.

Yes I know that's an "active" guitar setup...just curious of the comparison if someone has tried.

I understand the confusion as it's rather hard to get your head around these tone shapes.
In short NO Clap Strat tone circuits are dead. a mere hump of about 5/6 Db from memory. (someone here a while back asked about TBX and I simulated it for them. Sorry no time to search at the mo)
If you feel those onboard tricks bring positives to your sound then by all means use them but bare in mind that it's often only that one guitar an so what you gonna do when you bust a string 2 min before you walk on stage and you are forced to use a bog standard Axe.

I always look at it from a live gig situation/ on the road so to speak.
When you are famous you can have anything you want,,, heck they will come to you then. ;D

Meanwhile having built all the famour tone circuits (In Amps) there is Absolutly none that can do a true *Notch Mid Cut*

Side note:
Jack1962 ,, observation is (I assume) talking about the AMP As A WHOLE.
Whereas I'm refering to *Tone Stacks* as a *Seperate Entitey*
Entirely observed on there own merit.
It would be an eye opener if Jack inserted the HiWatt Tone into the Dumble,,
He would be in for a big suprise.
That said if smudgy tone is your thing then I have no arguement.

For me the *notching effect* is far less lossy that big sloping curves.

Heres how it works:
LOOK carefully at the pic,
If you make any CUT in freq broard and shallow then you also pull out a lot of energy in the signal path. (some could argue that with the power of a Dumble POWER matters little,,, yeah right and like EVERYONE OWNS an Dumble???)

Meanwhile back in the real world.
Where was I?
By implimenting a steep notch when cutting the mid you achieve better results as you suck less energy from your signal. You are wasting less energy this way.

I can't find the snap I wanted of a HiWatt / Dumble shootout so this will have to do tonight. It will give you some *Visual idea* of what is happening.
Notice the *Tonemender has a soft dished effect on the sound*.
This is the classic Fender mid scooped effect.
Now look at my Modded HiWatt tone !!!! Trust me this is stunning in front of a simple fuzz box like a TS9.
And I'm sorry to say that the Clapton or TBX tone circuits can only dream about these tone shapes. 8)

Hope it helps,,Phil
« Last Edit: June 26, 2010, 04:04:53 AM by phatt »

Jack1962

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Re: What do you think of this hydrid preamp?
« Reply #9 on: June 26, 2010, 07:07:26 AM »
I fully understand the that your are speaking of the tone tank brother , and yes I was speaking of the entire amp. Here in "the real world " why would I insert the tone tank from a $300 amp into a $15,000 amp.  :lmao:

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phatt

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Re: What do you think of this hydrid preamp?
« Reply #10 on: June 28, 2010, 11:50:11 AM »
Quote
No other passive tone circuit I know of can pull the mid notch like HiWatt.


Curious  if that included the on guitar circuit board and tbx  (Eric Clapton signature strat)

I build (or have built) all of my strat type guitars with that circuit

I've never used a HiWatt.

Yes I know that's an "active" guitar setup...just curious of the comparison if someone has tried.

The post about TBX circuit was here,,, you may wish to read it.
http://www.ssguitar.com/index.php?topic=1416.msg8896

I doubt the test pics are still there but if it helps a good friend owned a *Strat Elite* but eventually sold it and went back to stock units.
The only useful trick active circuits can do is the Volume acts as a gain knob which is a nice touch as it allows more distortion control over the passive Volume knob setup.
But then a good pedal may work out more user friendly.
Depends on your style of playing and how you wish to work with the gear you have.

Same chap now uses a stock guitar and a little tone box I invented I very much doubt he would go back to onboard ideas now.:tu:
Phil.