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Author Topic: Hybrid project started.  (Read 13208 times)

armstrom

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Hybrid project started.
« on: January 15, 2009, 02:04:50 PM »
I just finished the first stage of my hybrid combo amp. My plan was to build a complete low-wattage tube amp, run it through a dummy load (probably a weber MASS speaker motor) and tap the speaker level to drive a passive tone stack followed by a DSP effects processor and finally into my LM3886 power amp. The combo will likely use a single 12" Lil'Texas neo speaker to keep the overall weight down.

I have completed the first phase of my master plan :) The tube amp is done and tested. It's a firefly from www.ax84.com
If anyone is curious I have a 2mb sound clip of my friend noodling around on the amp. Keep in mind that the amp was only driving a 5" Jensen MOD speaker so the bottom end is kinda muddy. Strange, who knew a 5" cone didn't do so well in the low range  :P. The guitar is a Gibson ES 335 with stock humbuckers.

http://www.mr2-power.com/firefly%20test%201.mp3

-Matt

phatt

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Re: Hybrid project started.
« Reply #1 on: January 23, 2009, 09:43:01 AM »
I just finished the first stage of my hybrid combo amp. My plan was to build a complete low-wattage tube amp, run it through a dummy load (probably a weber MASS speaker motor) and tap the speaker level to drive a passive tone stack followed by a DSP effects processor and finally into my LM3886 power amp. The combo will likely use a single 12" Lil'Texas neo speaker to keep the overall weight down.

I have completed the first phase of my master plan :) The tube amp is done and tested. It's a firefly from www.ax84.com
If anyone is curious I have a 2mb sound clip of my friend noodling around on the amp. Keep in mind that the amp was only driving a 5" Jensen MOD speaker so the bottom end is kinda muddy. Strange, who knew a 5" cone didn't do so well in the low range  :P. The guitar is a Gibson ES 335 with stock humbuckers.

http://www.mr2-power.com/firefly%20test%201.mp3

-Matt

Good on ya for having a go at it.
As I may have already perfected what you are trying to achieve I figure I may be of some help.

The problem with the fire fly is the triodes,, sadly they just don't have what it takes.
Look up the transconductance of some Pentodes for a start then compare it to the triodes you are using.
I use Pentodes [6GW8], a small 10 watt Push Pull into a resistive load then tap off to a line level.

I found this to be a very good read if you are trying to get your head around what is often made unnessicerily complex. http://www.amptone.com/truesecretofamptone.htm
Hey look no maths  :tu:

My setup is just expanding on this basic idea.
my input EQ module is TRUE passive input  [HiWatt style] > tubeamp > ReAmp box [or power soak] > 5band graphicEQ +-6Db > 120watt SState poweramp.
Graphic is 100HZ > 330HZ > 1kHZ > 3k3HZ > 10kHZ.
 
Assuming an 8 ohm output from say a pair of EL84's in PP,,The big soak resistor can be made from three paralelled 33R 10 Watt Wire wound resistors giving about 11 ohms. Exact ohms is not super critical a little more than 8R is likely to be better but don't go crazy.
If you want to spend the time with inductors, Caps or silent speakers at this stage feel free
but there are easier ways to get around the loss problem via EQing. [Read the above Link]

Here is a mud map of the basic setup I use.
Cheers, Phil.


armstrom

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Re: Hybrid project started.
« Reply #2 on: January 24, 2009, 06:49:41 PM »
Can you elaborate on what you mean by the trides not "having what it takes"? To do what? I'm under the impression that if an amp sounds good driving a speaker it will produce a similar sound (give or take) when driving a dummy load and "tapping" the output with a following stage. Using a reactive speaker motor go even farther toward replicating the signal driving a speaker.

phatt

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Re: Hybrid project started.
« Reply #3 on: January 25, 2009, 09:41:14 AM »

Ok,
   If you simulate a triode Push pull output stage [firefly] you will notice the waveform becomes rounded at full power but NEVER Flat topped as It does not possess the grut needed to do so.

Pentode PPull is a very different animal,,
it just square waves with very slight rounded corners.
If you have access to one of those fancy tube amps that has
a triode/pentode switch on the output tubes then
see which one sounds full to you? Yes it works but is that what you want?

One reason the pentode was perfected was to get around this very problem,, so to me it's kinda going backwards to use triodes for a power stage.
Oh I admit I wanted that firefly amp to work but I'm glad I took the time to read stuff first.

TC [transconductance] for EL84 is about 11,200
now try and get that from a small signal triode.

I did listen to your little clip so if your content with what your getting
then disregard my ramble.
Also if your happy with Attenuators alone then that's ok too but
a whole new world awaits those how want to go the extra mile.

If you wish to hear this Reamp concept taken to the extreme then
go have a listen to the Guytron GT100 Amp.
It's a pair of EL84's pp driving a resistive load then Reamped via
a EL34 quad output stage, effectivly giving you 2 tone stacks and jezz
if that one does not prick your interest then nothing will.

Your last sentence tells me you may have missed something in the link. "The whole point is about EQ",, In fact EQ tweaks are sitting at every stage in those old tube circuits.
If you're content with the mass thing fine but it's a whole lot simpler my way. You obviously wish to process with DSP anyway so the mass is hardly worth the effort.
Just my two cents,,

Cheers Phil.

Brymus

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Re: Hybrid project started.
« Reply #4 on: October 09, 2009, 02:50:41 PM »
How is your project coming ?
I missed this thread somehow,but I had the exact same idea.
Re-amping a Firefly type amp with a lm3886.
I recently heard a Firefly that used ECC99 for the output tube and it was SO much better sounding than the 12AU7 version the guy built it out of.
But the ECC99 is a new tube and there isnt much on the web about it.
I would love to see a schemaitc of a 10 watt PP amp using 4 ECC99 tubes(sorry off topic)
Also I like the idea of the NEO spkr.
I want to build a light weight amp using toriodal trannies and a NEO spkr,aluminum chassis,
And Pine cab shouldnt weigh much like that.

Zappacat

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Re: Hybrid project started.
« Reply #5 on: October 10, 2009, 12:13:29 PM »
Hey Phatt, can you elaborate a little on what "semi-passive" tone stack means in your diagram?  Thanks!
I put my pants on just like the rest of you - one leg at a time. Except, once my pants are on, I make gold records.

phatt

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Re: Hybrid project started.
« Reply #6 on: October 11, 2009, 07:31:07 AM »
Hey Phatt, can you elaborate a little on what "semi-passive" tone stack means in your diagram?  Thanks!
Sorry for any confusion ,,,It's the very same one I've posted here under schematics and Layouts.. *The PhAbbTone box*.

I only used the phrase *semi passive input* simply because only the input is passive the output is of course *Active*. Since posting my tone circuit I've realised that by calling it *Passive tone * some may see it as bending the truth :-[

That little gem of a circuit just saves a whole lot of stuffing around with the needless complexity of a whole front end preamp.  Heck who wants the cost and work of wasting a whole triode stage when this simple trick does the same job.
Cheers, Phil.

phatt

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Re: Hybrid project started.
« Reply #7 on: October 11, 2009, 07:42:49 AM »
How is your project coming ?
I missed this thread somehow,but I had the exact same idea.
Re-amping a Firefly type amp with a lm3886.
I recently heard a Firefly that used ECC99 for the output tube and it was SO much better sounding than the 12AU7 version the guy built it out of.
But the ECC99 is a new tube and there isnt much on the web about it.
I would love to see a schemaitc of a 10 watt PP amp using 4 ECC99 tubes(sorry off topic)
Also I like the idea of the NEO spkr.
I want to build a light weight amp using toriodal trannies and a NEO spkr,aluminum chassis,
And Pine cab shouldnt weigh much like that.
Brymus,
           I have no doubt that the firefly would work as you describe but 10 watts from a quad of small signal triodes (ECC99) I very much doubt?
From my understanding  these are still ONLY a small triode.
I've already stated in my last post why the firefly may not be the ticket some dream of but hey,,,I've been wrong many times before.
In my experience even a small Single ended Pentode like a Fender champ would Eat a triode PP amp for crunch.
Phil.

Brymus

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Re: Hybrid project started.
« Reply #8 on: October 11, 2009, 12:57:37 PM »
Phatt the data sheet for ECC99 lists a quad for 10 watts in PP or 2 for 5 watts a single ECC99 is 2.5 watts in self split PP on the Firefly.
This is a new tube developed by JJ for use as a headphone amp as a driver in an amp like 300B or for low wattage PP designs.
It has been getting rave reviews for audiophiles and guitar gear junkies alike.
« Last Edit: October 11, 2009, 01:00:20 PM by Brymus »

J M Fahey

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Re: Hybrid project started.
« Reply #9 on: October 11, 2009, 01:21:02 PM »
Personal opinion/taste: I hear overdriven triodes "bland/soft" sounding compared to overdriven pentodes.
In a preamp (which usually tends to provide "buzzy" distortion), a triode may be the way to soften that somewhat, and that's what's used by 99,9% of makers (with a few notable exceptions), and not forgetting their low cost, abundance, ease/tolerance of biasing and the fact that they usually come "two per pack"; but for *power* distortion pentodes beat them all the way.
A humble 6BQ5/EL84 or 6V6 beats any triode to death.
I often use an EF184 directly driving power MosFets with very good results.
Juan Manuel Fahey

Alexius II

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Re: Hybrid project started.
« Reply #10 on: February 17, 2012, 12:47:04 PM »
I recently made a small self-split push-pull tube amp using not the 12au7 but quite similar russian 6N1P (dual triode). It is very similar to the G2 kit from madamp and sounds quite nice (clean to crunch). I stumbled upon this thread and decided to post a short recording of severely distorted output... maybe it will help someone decide to (not?) build this thing :lmao:
Most will find this type of sound disgusting, so be advised :duh

Guitar signal was boosted with ROG Thor.
http://www.box.com/s/ik3s6erp5otdufbr5jjh

joecool85

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Re: Hybrid project started.
« Reply #11 on: February 17, 2012, 03:25:21 PM »
I recently made a small self-split push-pull tube amp using not the 12au7 but quite similar russian 6N1P (dual triode). It is very similar to the G2 kit from madamp and sounds quite nice (clean to crunch). I stumbled upon this thread and decided to post a short recording of severely distorted output... maybe it will help someone decide to (not?) build this thing :lmao:
Most will find this type of sound disgusting, so be advised :duh

Guitar signal was boosted with ROG Thor.
http://www.box.com/s/ik3s6erp5otdufbr5jjh

Thanks for sharing, VERY distorted like you said.  Not my sound, but I'm sure it might help someone.
Life is what you make it.
Still rockin' the Dean Markley K-20X
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Alexius II

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Re: Hybrid project started.
« Reply #12 on: February 18, 2012, 08:14:47 AM »
Yeah, I'm a metal-head, but this is way too dirty even for me  :duh

The amp does however sound quite good when using a distorted preamp and driving the output tube just a bit over the clean area. Nice compression and gritty character. This is how I use it most of the time, and the great thing is - it does this at bedroom level, as it produces only 1 or 2 watts  8)

I will be making another similar amp with the full tonestack, as it really has a BIG effect on how nice/bad the output tube sounds when overdriven.