• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Tubes and Solid State Overview

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Hi all,

I'm just starting to get into the audio world. My experience is basic stuff, HS electronics course, hands on with computer hardware, circuit repair, with lots of reading :D

The books I own at the moment are:
Dickerson's Loudspeaker cookbook
Rosenblit's Tube Audio Design
Some of my dad's old electronic books like:
Navair Volume 1 Electronic Circuit analysis (Airforce tech manual) :D
Navair Volume 2 ELectronic Circuit analysis (Airforce tech manual) :D
Basic Electronics by Paul Zbar (McGraw-Hill)
Industrial Electronics by Paul Zbar (McGraw-Hill)
Basic Electricity by Paul Zbar (McGraw-Hill)
Eletronic Instruments and Measurements by Paul Zbar (McGraw-Hill)
Ordered books that are on the way:
Morgans Valve Amp. Ed. 2
Active filter crossover cookbook
Tube preamp cookbook

Yes, that's it. I typed all that out to give you some backround and show you I'm serious about this.

So, I've been reading this board for months now and I feel I'm ready to start designing a schematic for a preamp.

If I may outline my thoughts of tubes vs solid state:

+untouchable detail
+low DF(debatable)
-High voltage
+soft clipping & "pseudo-Loudness" (due to 2nd/3rd Harmonic distortion)
+lower Current
-extra heat
-initial finacial outlay
-replacement of parts more frequent

Solid State
+Lower Voltage
+Less expensive in initial outlay and maintanence
+High DF (debatable)
-higher current capacity of transistors
-Hard clipping
-Live stage effect not there (detail)

What I want to do is have a preamp with 8 output channels
(2front, center, 2 rear, two side, and a sub)
Sorry Audiophiles, I like my AC3 and DTS

So this thing would be a monster.

I want to go the tube route, just because of detail and pure sexiness. But, it would be more expensive.

1. I guess my question is, what are the pros and cons of tubes vs. Solid.

Is my reasoning sound or not?

When reading Bruce Rozenblit's book I found it funny that one could make a UL or Cascode amp and have it so pure that one did away with the tubes main salvation; that of detail or presence.

2. Ignoring heater elements, do tube give the same amount of power per watt that solid state does?

3. And giving the Voltage to Amp ratios between tube and solid state, does one eat more energy?

I apologize for the long post and the extraneous material. I want you to know where I'm coming from. I have been thinking about this for a few weeks and can't seem to put straight in my head to, what I've been reading.

Quite truefully, the initial expense of tubes and their subsequent maintanance, along with those impressive voltages, scare me just a tad.

So what say ye?



P.S. I hope I haven't stirred up hornets nest too much?
Years ago, in high school, I watched my friends build basic electronic projects using transistors and circuit boards. I helped quite a few of them remedy damaged boards, cold solder joints, and damaged components.

I found the old chassis punches, terminal strips, tube sockets, and genuine braided-cover wire deep in the workshop catacombs. I never attempted a project that didn't involve valves and transformers, and point-to-point wiring.

I will never forget the satisfaction of the warm smell of tubes and power resistors...or the sweet music that resulted.

You can achieve excellent results with either transistors or tubes, but my heart lies with the latter. Over twenty years later, I still fondly remember the smell, the sound, of the venerable valves.

In the early days of transistors, the real serious power handling applications were the domain of tubes. The advent of power transistors, devices capable of handling progressively larger currents, changed all that.

You specify an interesting application requiring eight channels. Though the requisite circuitry would require some real estate for tubes, it is definitely possible. I'd suggest looking at your required gain, and lay out the alternatives.
If I was starting from scratch, I would go for a hybrid design, use small dual triode tubes for preamp and use a transistor (bigass mosfets) for power amp. This cuts down on the cost for valves, you dont need much in the way of transformers for small signal triodes, they dont run very hot at all and they can last for ~10 000 hours before replacement.

You would get the benefit of a valve "influence" on the sound, along with high power and reliability. It would also look great!! Transistors don't glow (much!)

That is going to be my next project one of these days. :D
I believe that for the wattage input that tubes are less efficient, that heat you feel is a lot of energy. Once you get it on and warmed up the difference shouldn't cause as much difference on your bill as the soldering will when you build. As far as building an 8 channel preamp the cost of the tubes is going to be way down on the list compared to RCA plugs, potentiometers and switches. As a beginner advising a beginner getting the layout is just as difficult as the schematic. Use a large chassis so alterations and additions are easy to do and use good solid wire to build with. Do a to scale layout on graph paper before you begin, it will really help with the building.
One BIG + you left out is tube rolling. The differences you can make by changing out your tubes is something you can't do with SS and I think is a big part of the fun.

All of you who replied. You've been a big help. My thoughts are a little less random now. You've given me a lot to thing about. I think the hybrid system is the way to go. I'm going to start designing one soon. That idea about the chasis and graph paper will save me a lot of frustration later.

I appreciate your responses

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