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phatt's Schemo Collection

Started by phatt, May 14, 2010, 09:23:54 AM

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rodriki1

Hi,

some time ago i have done some experiments with the Idea of LXH2 site.

i have made the LOW VOLTAGE power AMP (as they stated, genuine power amp
distortion with low power) using op amps as preamp and
two El84 as pushpull output...

i live in small apartment and i still found it was too much sound
for a low power amp (i used a generic 12" speaker i found in a store here)...

besides that a made another amp based on the LM388 chip using
a preamp with two simple diodes for distortion (just like boss DS1,
MXR distortion,guvĀ“nor and so on). I used 1n4148 diodes.

I decided to compare the sound of the two amps.
i was expecting to have a HUGE diference.
but for my surprise the simple SOLID STATE AMP  sounded quite
the same thing.
The El84 amp was more fat and bright...
but i think that the cost of the tube based circuit was very much higher.
considering that i wired the output transformer with my own hands, it was
too much work...
to make my sound test i used one mp3 player as the input of those two
amps (playing some guitar riffs) and recorded the samples of output....
I swear i could make a blind test using those amps and people
would very hardly capture the diference.

I ask my self if could tell from the results i got, that tube amp for lower voltage have a cheap sound???
Or that we can really get the sound that we want from solid state????

thanks

the amp from LXH2:
http://home3.netcarrier.com/~lxh2/lowpsch.html

the sample of the amp with lm388
http://ladelec.com/practicas/circuitos-analogos/336-amplificador-para-radio-de-am-con-lm388.html




J M Fahey

QuoteOr that we can really get the sound that we want from solid state?Huh
Well, there's these crazy :duh guys from SSGuitar, which claim that it can be done.
Maybe they have something.  8|

rowdy_riemer

There's obviously a lot of convincing ss circuits out there. After building a dr. boogey, it's hard to imagine forking out $2000 for a similar sound. Of course that's all preamp distortion. And of course, there's good emulation of power stage distortion. After getting a tube amp, I really like the way it sounds clean, especially with single coil pickups. It's the clean triode sound that I think might be hard to emulate. But then again, my experience with different amps is limited.

phatt

#18
Attn *rowdy_riemer*
Re "suggestions for a re-amping setup"
----
Good Your little 5watt is a perfect candidate for soaking and ReAmping:)

Attenuators look appealing as it's a simple add on but they are very limiting.

I've found them painfully frustrating till I understood you can bypass most of the issues surronding the losses with attenuators by simply running a soak and tapping the signal off to another Amp.
(The 2 ideas are very similar and it often gets confusing)
The *Second Amp* drives the speaker (The UA does this all in one box)

A simple resistive load soaks the power tubes and via simple voltage division is converted back to line level.
Run this soaked output through a simple Graphic and into a SS power Amp of your chosen wattage and you will be way ahead for a very small outlay.

Now you can go crazy and not annoy the folks next door. ;D

The pics should tell you most of it but may require some explaintion.
The load resistor for your 5Watt amp need only be 10Watt (you can go smaller but the cooler things run the better)
The box here runs only warm with my little 10Watt Amp.

The ground Lift will come in handy as you will no doubt have a second amplifier that is also grounded ,,trust me this sw will come in handy.

The Load R;
Assuming 8 Ohm output from tube amp then an 8 Ohm resistor will make for a very flat compressed output.
running 24 Ohms delivers a far more realistic dynamic response but will still need tonal adjustment to make up for losses.

Sadly there is probably no *perfect system* there will always be some loss when implimenting these things.

SS or Valves, you will loose some realisum when you turn the SPL down to very low levels but Any loss is far out weighted by the amount of tricks you get to do with this.
Have fun, Phil.



rowdy_riemer

Cool, thx for the info. I'll definitely give this a shot. BTW, I just picked up a stereo eq yesterday at the thrift store. Only $5.

phatt

Quote from: rowdy_riemer on May 18, 2010, 08:52:58 AM
Cool, thx for the info. I'll definitely give this a shot. BTW, I just picked up a stereo eq yesterday at the thrift store. Only $5.

Arrh, That's what we like to hear,,, *Cheap* ;)
I just mount 6.5 sockets in the back panel and install internal jumpers across to the RCA sockets otherwise it's a pain to work with RCA

The other channel is obviously not used,, So a spare eq for something else maybe.
Just watch out for the top line models with the *stereo wide function*.
I have one like that and it does funny things when engaged as you are only using one side and hence mono signal.

If you happen to have a rack processor (with stereo out) or similar gear you can now do all the fancy time effext *post Power tube* into a stereo power Amp and two speaker boxes.

I think you will have a lot of fun with it.
Cheers Phil.

Jack1962

first thanks for posting the schematics , those are very good circuits. Now for the The tube amp tone.

      That tube tone (compression, and everything else ) is acommplished as a effect of the entire system not just a single component or group of components. the best compression I have heard myself was from a old Marshall JCM 800 2204 if memory serves me, but if you check out just about any vintage tube amp most components are well out of the 20% tolerance , yes sir 20% , that is also another one of the factors that give ya that tube mojo lol . Then you have the xformers which greatly alter tone as far as that goes experiment with some simple inductors in these Solid Stae circuits it will surprise you the tone you can get out of them. As fair as the filtration goes guys it's really pretty simple in a tube amp there is far more filtration goin on in solid state amps , however with that said yep that influence's the tone too lol lol . as for the vintage cabs I'm sorry folks , but a cab made out of pressed wood with the same dimensions and with a good quality guitar speaker(driver) will give ya just as good tone as that old vintage cab.

          Now , as for the tube amp emulation , yes there are some out there that get fairly close , close enough , most people don't ave a clue as to the difference in tone. However , I'm sorry guys if you what it to sound like a Marshall or any other tube amp , buy that amp , no emulator is going to sound exaclty like that amp.



                                                   Rock  On
                                                     Jack

J M Fahey

QuoteNow you can go crazy and not annoy the folks next door. Grin
Now this advice should be taken with a grain of salt, considering that in Australia "the guy next door" may very well live 450 miles away, so a 1200W amplifier could be considered "a bedroom amp".
Ever heard of "The Outback?  :lmao: :lmao: :lmao: :lmao: :lmao:

phatt

Hi JMFahey,
                Very good,, very funny,, I'll pay that one, LOL.
I live on the north side of the fence,, the Dingo side.

BTW Not ALL of Australia looks like this,, Though the centre is very much a no mans land in places.
Some roads out there you can drive at 140 MPH for hours,,,  DEAD Flat straight.
It's quite errie at night.
Cheers Phil.

J M Fahey

Yea, I know. Mind you, in Argentina we also have a-couple-hundred-miles-straight roads and places compared to which, the Outback looks like a tropical garden
Just for kicks:

,

,

and

,
As a side note, I am not writing from Australia (or Canada or even the US), simply because at Liverpool docks, my family boarded "the other" ship.

bry melvin

Out of the way places are handy for a working/practicing guitarist

This album art was taken in my yard http://sunsets.arivacaart.com/home/back%20cover.jpg?attredirects=0

rowdy_riemer

The eq I picked up had a dead left channel, which would be fine since I only need one. But I just hated having a dead channel, so I pulled it apart and tried to diagnose the problem. None of the electrolytic caps looked bad. I couldn't see any problems with cracks in the pcb. But I did notice that each channel had a 4558 dual op-amp. On the left channel I could detect a signal on pin 6(+ input), but there was only a 60 Hz signal on pin 7 (- input) and pin 8 (output). Well, I knew that wasn't right, so I pulled that 4558 off the board, and soldered in another one. That did the trick. I know that's a fairly simple fix and not too big a deal, but being that that was the first factory-built audio appliance I successfully trouble shooted and fixed, I was pretty happy about it. :)

J M Fahey

Congratulations. That's about it. Good troubleshooting skills !!  :tu:

rowdy_riemer


dogbox

Hi Phatt, thanks for sharing these schematics and all your other info. I plan on breadboarding the Phabtone soon when I get my hands on some TL072's (next trip to jaycar). I was digging around and checking out some your old posts - Your sound clips sounded great!!!

A couple of newb questions...bear with me  as I don't have any history of electronics. Just what I have read on forums, books for past few months.

You mentioned on some older posts that the tone stack section was from a Hiwatt amp.

1. Would it be possible to take the input/tone stack section, say everything from the left of C6 in your Phabtone schematic and add that to ANY low watt SS amp circuit? For example, looking at the runoffgroove schematic for a Ruby amp (apologies if you don't have one handy) - could I take your input section and wire it to pin 2 of the lm386 used in the ruby - kind of in the way there is a Fetzer ruby or Marsha ruby?

2. How would either the tonestack or whole phabtone go as the pre for a LM3886 amp?

I should state that i'm looking for clean(ish) amp tones and tend to use pedals when i want distortion. Is the phabtone what I should be looking at?


cheers
Steve
p.s
Nambour hey ;)!! Not much desert there, in fact the soil is sooo good just look at how big the pineapples grow:)
Also the birthplace of our former Primeminister - Kevin 07 - lets not go there shall we :'(