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Old 9th April 2009, 03:43 PM   #1
rtill is offline rtill  United States
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Default tube-like SS power amp

Just curious if there is any SS power amp out there that may have a tube-like warm sound or qualities.
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Old 9th April 2009, 03:47 PM   #2
roender is offline roender  Romania
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Can you please define those qualities?
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Old 9th April 2009, 03:50 PM   #3
rtill is offline rtill  United States
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looking for that natural tube-warmth sound. Guess I'm looking for maybe an emulation of a tube power amp using SS parts. Maybe a type of FET power amp....
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Old 9th April 2009, 03:57 PM   #4
roender is offline roender  Romania
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Well, you see, someone may or may not consider a warmth sound a quality of a power amplifier.
A well designed and constructed SS amp sound almost like a very well constructed tube amplifier
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Old 9th April 2009, 04:07 PM   #5
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Read O.H.Schade (RCA 1939) "Beam Power Tubes"

Same technique when applied to a MOSFET results
in what Nelson Pass calls "Zen". A triode emulator.


There are two factors that local negative feedback
might linearize. Voltage or Current. Take your pick.
Can shoot for something inbetween, but can't have
it "perfect" both ways in one stage.

NFB from resistance below the emitter/source/cathode
tends to increase current linearity collector/drain/plate
with resulting increase in dynamic resistance/impedance.
You gain control over current, but lose control of voltage.
Your curves tend to look like a Transistor or Pentode.

NFB from a network tied to the anode voltage has
quite the opposite effect. It linearizes output voltage,
but lose some control of output current in exchange.
This drastically lowers dynamic resistance/impedance.
And your adjusted curves tend to look like a Triode.


Here, Schade feeds back 1/10th of 6L6 plate swing
back into the G1 grid. The curves look very similar to
a Triode strapping. But the screen actually tied high,
just as a MOSFET today might behave...
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Old 9th April 2009, 05:48 PM   #6
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The Alephs and AKSA55 should get you very close.
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Old 9th April 2009, 05:50 PM   #7
teemuk is offline teemuk  Finland
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Take a look at guitar amplifiers. Various examples of getting "tube-like" sounds (whatever that means in each case) have been made since early 1970's. Just too much stuff to discuss in a single post but basically you'll find:
- high output impedance (usually achieved with current feedback)
- various soft clipping circuits
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Old 9th April 2009, 05:51 PM   #8
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In addition I found the following quote from Mr.Pass in the Feastrex thread:

The whole point of the F3 was to emulate a triode with a power JFET
operating in the "linear" triode-like region. A fine SET would be the
go-to choice, and by "fine" I mean something with .1% thd or less
at 1 watt.
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Old 9th April 2009, 07:56 PM   #9
Bigun is offline Bigun  Canada
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ahhh, this is my 'next' project, a simple amp with complex sound.

I am on the same learning path.

I have become a believer in the opinions of others that the tube-sound can only be approximated with SS and that a key to this includes the nature of harmonics generated. In this case 2nd and 3rd are good and higher are bad.

There are several ways to achieve this, no one circuit topology has the monopoly. But of all the devices, the JFET has the closest operating characteristics to a tube.

Why not build a hybrid, with tube input stage and SS power output stage for best of both worlds?

AKSA55 is commercial, you can't have the schematic and component values nor can you buy the kit anymore !!! but the circuit topology is (I believe) very similar to many other amplifiers presented on this forum and the harmonic profile is controlled through the imbalance of current flow through the two legs of the input Long-Tail-Pair.

I'm trying to make an AKSA55 here: TGM Amplifier ?
"The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed." Robert M Pirsig.
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Old 9th April 2009, 08:21 PM   #10
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Default i know that ......

you are going to kill me with what i am going to say ....but i am going to say it any way .......

been constructing a gozilion amps .... tubes fets bjts name it ive done it ( be aware now i said constructed not designed ) .....

a well constructed BJT sziklai bootstraped and over biased will be my suggestion ....

many will not agree but i going to place my point for anyone interested ....

i would go for an amp that has amazing sonics than an amp that is too square and too perfect ....

i would go for something more everlasting than an amp that has limited life

i would go for efficiency than an amp that is a toaster

just last night i finished a ZCA ( zero component amp ) by mark houston ..... took me about 6 hours to finish it all from scratch

then i listen to it for another six .......

it was the most nice 1.5 watt i ver listen to my life .... ( in few words totally pointless)

thats my opinion .....

an amp designed arround original 2SA1302-3281 with rugged psu abit of overdesign and a bit of overbiased is simply unbeatable !!!!

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