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Old 19th November 2012, 08:47 PM   #21
SY is offline SY  United States
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Quote:
Originally Posted by tinitus View Post
hmm, how about electrically compensated BSC, like done with actice crossover (sometimes) ?
I suspect the OP is after extra harmonic distortion and soft limiting, the effects often called "tube sound."
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Old 19th November 2012, 08:51 PM   #22
tinitus is offline tinitus  Europe
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Quote:
Originally Posted by SY View Post
I suspect the OP is after extra harmonic distortion and soft limiting, the effects often called "tube sound."
yes, as many others have
since the OP only posted once, its easy to check
and it could be so, but doesnt say, directly
but if listening to a PC soundcard, I can certainly understand why he would want that

but maybe its due time he tells what it is he actually wants
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Old 20th November 2012, 02:40 AM   #23
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I like to build stuff. In the long run, I will make both, a neutral one and an effects box just to see how they compare. Right now, I am looking for a reasonably neutral one.
Why I want to make a tube one is because I have nothing with tubes, its all ss. Once this is ready, I will move the B1 to the other system.

Now my turn to ask questions, since its either effects box or a SS like neutral without tube characteristics (read 2nd harmonics), why do you guys use tubes. Why not just use solid state and save a lot of cash, its easier too, no output transformers, no high voltages etc. If a gear is going to be indistinguishable from SS, why use tubes et al.
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Old 20th November 2012, 03:17 AM   #24
TheGimp is offline TheGimp  United States
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I wouldn't go so far as to say indistinguishable from SS, unless one cranks in large amounts of global negative feedback. The amps I've built so far are reasonably neutral, but are quite different from my ss amps.

I build tube amps because (1) I used to play around with tubes when I was young and I like the nostalgia, (2) I find studying tube theory to be interesting, so it keeps me thinking, (3) I like to do things a little differently.

Also, its not just second harmonic distortion that plays a part, but a broad spectrum of harmonics and their amplitude relationship that determines the characteristics of the amp.

Last edited by TheGimp; 20th November 2012 at 03:32 AM. Reason: note on 2nd harmonic ist.
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Old 20th November 2012, 03:32 AM   #25
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First of all, it's a pretty rare guitar effects box that uses really good quality parts and is flat 20HZ - 20kHZ. I wouldn't go that way for my Hi-Fi. Tube amps are art objects. People like looking at them. They typically have a distortion spectrum that is arguably more natural, perhaps more like how the ear-brain mechanism distorts. The distortion as measured by conventional bench techniques seems low enough that there shouldn't be any noticeable difference, yet many say otherwise.

If you put a tube in the signal path that is outside any kind of feedback loop, you'll have its more natural distortion spectrum dominating the distortion spectrum of most decent transistor products elsewhere in the signal path. If tube distortion warms up the sound, this should get you most of the way there.

Personally I'd use 6SN7's with current sources in place of the plate resistor in the case of a gain stage, or in place of the cathode resistor in a follower buffer stage. Not only does the current source increase gain (when applicable), linearize the tubes transfer curve (less distortion), possibly reduce noise, but it gives the stage much better power supply rejection factor, which means less hum.

Personally I'd put tone controls in any preamp I built, which is why I'd have voltage gain stages. Those who think tone controls are evil must not have had a decent one. Shelving is wrong. Baxandall is good. A four section Baxandall is excellent.

The early "James" style topologies would go between gain stages. Since the gain stages typically had no negative feedback (which can cause instability (spurious oscillations)), some think they might sound better. Most of the classics from the 1950's used this approach. Starting in about 1960 most companies switched over to the "Baxandall" topology which puts the tone circuit elements in a feedback loop around one or two tubes that are set up to have substantial voltage gain. These gain stages had feedback through the tone control parts, and sometimes separate from that. If you hate using negative feedback, you might want to try the James type.

Duncan makes a decent circuit simulator for the James topology. You vary the elements and it shows the resulting frequency response. It's a freebie. Google should get you to his page. All the classic early guitar amps used a variation of the James. The Baxandall is easier to make be accurate (flat when pots are centered). The James requires some tweaking to get flat when pots are centered.

As a musician, I can't imagine ever NOT having tone controls. It's about what sounds good, not what is imagined to be more accurate based on lab tests or whatever. Nobody listens to music in an anechoic chamber, and recording engineers spew all kinds of variations of tonality. The way any speaker interacts with the listening room acoustics will have a large effect on tonality. It's typically pretty significant. Pretending flat is always best is foolish.

Last edited by Bob Richards; 20th November 2012 at 03:38 AM.
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Old 20th November 2012, 05:55 AM   #26
aeandm is offline aeandm  Ukraine
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Hi, I do not use a common negative connection
only local, as a necessity, transistor noise
never be compared with the tube, the lamp itself is a geometric
electrode shape, no two identical frequency and amplitude
response will always be different, and therefore the sound,
Art to bring you a minimum of feedback,
this is the Hi-Fi. I do not believe in simple circuits "the smaller details
the better "is out of ignorance of physics and electrical engineering.
In a good model, all in place, the remaining 50% is the selection
lamps to minimize noise and background (leakage between the filament and cathode)
saw this making corrector RIAA.
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Old 20th November 2012, 09:57 AM   #27
Gost22 is offline Gost22  Bolivia
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Quote:
Originally Posted by flatheadmurre View Post
For the best "tube sound" buy a guitar pedal .
Bravo, you discovered America!
I asked for advice on how to get a subjective evaluation of the tube/valve sound and you gave this answer,...
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Old 20th November 2012, 11:50 AM   #28
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Check out the Broskie Akido boards - quite popular around here so lots of help is available.
GlassWare Line Stage & Headphone Amplifiers Kits and PCBs

another option: search for the diytube Budgie PCBs that can be used as a phonostage or low gain linestage. Wallwart power supplies.
diytube.com :: View topic - diy*tube budgie PCBs for sale (Updated 10/28/11)

on the more expensive side, I had good results with the Ultrapath transformer-coupled linestage, but that requires a good clean power supply. At least the gain is low.
Electra-Print.com The Ultrapath

One of my favorite - though very high gain - linestages is a triode-connected EF86 dc-coupled to a 6922 white cathode follower. It has enough oomph to drive a pair of (high-z) headphones. However as stated, the gain is fairly high, so it's best used with an amplifier with low sensitivity.
6th Street Bridge: Triode Connected EF86 linestage and headphone amplifier

for a truly "tubey" sound - a Dynaco PAS or any vintage preamplifier with out-of-spec parts will suffice
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Old 20th November 2012, 10:17 PM   #29
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Quote:
Originally Posted by kstagger View Post
One of my favorite - though very high gain - linestages is a triode-connected EF86 dc-coupled to a 6922 white cathode follower. It has enough oomph to drive a pair of (high-z) headphones. However as stated, the gain is fairly high, so it's best used with an amplifier with low sensitivity.
6th Street Bridge: Triode Connected EF86 linestage and headphone amplifier

I used an EF86 (the JJ version) in the front end of a guitar amp I built, and it has a voltage gain of about 240, which was more than I wanted. The good news is that a resistive attenuator at it's output might cut noise from the tube more than the noise it ads.
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Old 21st November 2012, 06:36 AM   #30
Gost22 is offline Gost22  Bolivia
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Quote:
Originally Posted by kstagger View Post
Check out the Broskie Akido boards - quite popular around here so lots of help is available.
GlassWare Line Stage & Headphone Amplifiers Kits and PCBs

another option: search for the diytube Budgie PCBs that can be used as a phonostage or low gain linestage. Wallwart power supplies.
diytube.com :: View topic - diy*tube budgie PCBs for sale (Updated 10/28/11)

on the more expensive side, I had good results with the Ultrapath transformer-coupled linestage, but that requires a good clean power supply. At least the gain is low.
Electra-Print.com The Ultrapath

One of my favorite - though very high gain - linestages is a triode-connected EF86 dc-coupled to a 6922 white cathode follower. It has enough oomph to drive a pair of (high-z) headphones. However as stated, the gain is fairly high, so it's best used with an amplifier with low sensitivity.
6th Street Bridge: Triode Connected EF86 linestage and headphone amplifier

for a truly "tubey" sound - a Dynaco PAS or any vintage preamplifier with out-of-spec parts will suffice
Hi kstagger!
How would I create the only preamp with tube EF86 [url=http://6streetbridge.blogspot.com/2008/11/triode-connected-ef86-linestage-and.html] first stage and the output capacitor of 2.2uF-MKP.
Or to put the output buffer with ECC88 (6922) first stage after the EF86?
What I got gein and that the output impedance Zout for first stage?
thank you!

Last edited by Gost22; 21st November 2012 at 06:43 AM.
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