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pre-amp or ruby amp + mod

Started by hasss, December 10, 2009, 05:25:35 AM

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Hello guys! I want to build a simple practice combo. I have a power amp with lm3886 chip and i want a pre -amp. I want something clean with a tone stack and a little bit of overdrive. Can you suggest me something?

There is another option, but i need some help. I have a ruby amp built and i like it a lot. It has the clean tone and the overdrive, but there is no tone control or tone stack. I have a couple of 250 log pots and 100 log pots and i want to make a fender tone stack and add it but i don't know where. Can you suggest me an active tone stack and tell me where to put it?

I have an idea to make a tillman preamp-->ruby amp + tone control-->lm3886. Is it a good idea? If there is such topic i'm sorry. Oh and sorry for my english. :D

I want to keep it simple and i have a small amount of money, that's why i want help.
Any opinion on ROG design with fets?

J M Fahey

If you like your Ruby, you can add *after* it a passive tone control, either a Fender, Marshall or Phil/Phatt's excellent version of the classy Hiwatt; the volume pot you use after that (connected straight to the input of the LM3886) becomes your master volume. The result will be excellent.
You can replace the Ruby's speaker by a 1K resistor, and the output 220uF cap for a 10uF.


Thanks a lot. You are the first how gives me an exact answer in three days and i posted a lot of topics.

I may use the Hiwatt tone control thanks.
And after the tone stack i doesn't need to boost the signal with transistor?
And is it good to use the tillman preamp in front of ruby?

J M Fahey

Start as simple as possible: your Ruby -> passive tone controls -> 3886.
It often is enough, because the 3886 is a sensitive amp.
If it's not, you can easily add a 1 transistor booster later.
Where are you writing from?


Hi. Thanks a lot. I'm writing from Bulgaria.

Yesterday i saw the Phil/Phatt's hiwatt but now i cant find it.
Can you give me a link or something?


I found it. I think i'll use it but i want to know, can i cut it after the C6 and use it without the op amp?And should i use C6 in this case?

J M Fahey

Right. Use C6 so you are independent from what the next stage has.


When i cut it after C6 and put it after the ruby, should i power supply the tone stack?

J M Fahey

Hi. The tone stack itself, being passive , is not powered.
I don't imagine *how* you could apply power to it.
Of course, the Ruby/preamp and the LM3886 must be powered.


Hi hasss, 
         Just thought I better comment as there are some traps here I think.
Running a passive tone circuit *Straight into a chip PowerAmp* maybe a big let down.

I'm not familiar with the chip mentioned but most of those poweramp chips have a rather lowish input Z (input impedence) and as such are not capable of working well with any of the Tree type Hi Z passive tone circuits, including HiWatt.

My guess, The PhAbbtone circuit will be a waste of knobs, it will still pass a signal but the loss will likely be massive. :'(

As the PhAbbtone is my own design/ concept I hope you can appreciate/ understand that if you change it to much I can't promise a good result. 8|

There is a lot of voltage loss (signal strength) in All these passive tone systems but nearly ALL the Valve circuits have very high impedence (including the power amp stage) so the loss is not as noteable when used in Valve circuits.

SS amps often use an *Active tone setup* which has no loss and can be used in low Z circuits but as is often noted some of the *Valve magic* is due to the Hi Z tone circuity used in the amps of old days.
Hope I did not dampen your obvious desire to DIY.
Have fun, Phil.


Thanks for the answers.

Any proposals on a good tone stack?

I really like the hiwatt and the baxandall because they have a good mid boost when the knobs are down and of course your tone stack is really great.

Because i don't know much about tone stacks i would like to ask something.  Why your tone stack is passive when there is a op amp? Sorry for the stupid question.


Hi Hasss,
Q1/ "Any proposals on a good tone stack?"

I believe I've given you one already.
PhAbbtone built *AS Shown* will be better than most circuits found on the net.

Any Hi Z tone stack between the Ruby and LM3886 with no Extra active commponents will likely not be rewarding. There is every possability that the results will be dismal. Signal will pass through but the output will be quite low and tone controls will not work effectively.
I can't promise great tone if you try to short cut my circuit.

Q2/  "Because i don't know much about tone stacks i would like to ask something.  Why your tone stack is passive when there is a op amp? Sorry for the stupid question."

The only dumb question is the one not asked.

Yes it is somewhat confusing, My circuit is a *passive tone control circuit* and is also a *Passive input* device. ie, no *Active preamp* in front as is the normal case.

The word *passive* here is being used here to decribe 2 different situations.
Re the baxendall, they work in a diffent manner,, some folks like them but for me they don't work as I would like.
If my memory serves me correctly my reading remembers that *James* was a passive tone circuit and *Baxendall* was a James circuit used in a feedback loop and does actually have some gain.
(The word Baxendall has stuck and is used to decribe both.)

Just google some of these trems and I'm sure you will get some indepth pages of interest to read up on to better understand these things.

My PhAbbtone circuit is Odd/ different simply because it has no active front end like most amp circuits use.

So having built all the common tone stacks, Valve powered and SS powered.
I've come to understand that the active front end is not really needed with modern hi gain magnetic pups used in modern guitars. Most player use floor pedals or processors anyway so it will make little difference.
It will struggle with an acoustic *Peizo Pup* with No Onboard preamp when used alone but as most Acoustics today impliment onboard preamps then again it's unlikely to be a problem.

As you wish to use the Ruby in front then none of this will ever be a problem.


Awesome answer(s). Thanks a lot.

Now i know what i wanted.
I will use your tone control version 2 which i think you posted in the end of the topic.