Where do the tubes go?

Most of the tube units that come in for repair from my experience have failed because of poor design. Sometimes not enough room inside, sometimes poor circuit board thickness, and poor overall design to handle what a component should be able to deliver without breaking down. Even some of the higher priced units I see are made poorly.

Happy Listening.

"1. Would most people recommend an all tube system, or do you recommend starting with only a tube component or two.

2. What are the relative merits and disadvantages of placing tubes at various stations in a system CD-->pre amp --> amp ?"

The only way to answer those questions is to go out and listen for yourself. If you do otherwise, you'll probably waste your money.

Fair comments Newbee.

I've owned ARC tube gear for almost 10 years. Perhaps I'm lucky, but the only maintenance issues I've experienced related to blown bias resisters. Fortunately, there's an ARC authorized service tech near my house who also happens to make house calls for a small extra fee.

Can't speak about other tube amp models, but I think ARC gear is extremely well built and dependable. So except for the periodic replacement of tubes and occasional bias adjustments, no problems.

Your point about electrical matching has been a vertical learning curve for me. For others who may be interested in tube gear, pull some of my more recent posts. I've raised most of the relevant questions. And our more tech knowledgeable and savvy members have explained in plain English most of the key issues and theory.

Let me at least respond to one point you just raised. It's true that electrical impedance matching between a tube amp and speakers is a key consideration. Having said that, at least ARC uses some local negative feedback (partial cathode follower) to achieve low'ish output impedance.

For example, in the case of my amp, the ARC Ref 150, output impedance off the 4 ohm taps is just .55 ohms; and 1.1 ohms off the 8ohm taps. That corresponds to relatively tight output voltage regulation: +/- .4 ohms off the 4 ohm taps; and about +/- .8 ohms off the 8 ohm taps.

What that means in plain English is that my tube amp can perform somewhat like a SS amp. According to Ralph Karsten's white paper, SS amps typically have very low output impedances and present a constant voltage source to the speakers, a/k/a Voltage Paradigm amps. They produce power by generating current, have high damping factors and tight voltage regulation.

So, going back to my example illustrating the ARC Ref 150, while not a true low output impedance, constant voltage source type amp, it performs somewhat like one. Hence, the Ref 150 may have greater utility in driving a wider range of speakers than a tube amp that has higher output impedance, a low damping factor and a wider range of output voltage regulation.

So ..., as Newbee says, a little more homework is needed when going the tube route.

Happy Holidays.

Bruce

Relax and don't be stupid (get a reasonably powered amp with outputs at 8 and 4 ohms, plug it in, enjoy). Regarding reliability, there are FAR more tube guitar amps than hifi amps out there and they're often mercilessly dragged around, including combo amps with the speakers in the same physical space as the amp, tubes mounted upside down so all the heat goes up into the chassis (nearly every Fender amp ever made), and being used by people who don't care about the amp's inner workings as long as it powers up and doesn't quit in the middle of Louie Louie (more important than your listening room, how many tube amps quit at concerts with 15,000 plus people? Nearly zero...for years and years). Very similar circuits as hifi amps in most cases, but hifi gets the "precious/cautious" baggage attached. I recently had a new "Boutique" Class A hand wired all tube guitar head dropped by UPS so hard it bent the entire corner of the amp (heavy "lunchbox" style steel case) and after getting the kinks sorted with vice grips the amp works perfectly with no tube damage or any other damage. The myth of tube amp failure issues continues, and if you're too weak (disabled and extreme geezers excepted) to schlep a dead amp in for repairs or package it in the original box you should have kept, you're a wimp. Period.

Relax and don't be stupid (get a reasonably powered amp with outputs at 8 and 4 ohms, plug it in, enjoy). Regarding reliability, there are FAR more tube guitar amps than hifi amps out there and they're often mercilessly dragged around, including combo amps with the speakers in the same physical space as the amp, tubes mounted upside down so all the heat goes up into the chassis (nearly every Fender amp ever made), and being used by people who don't care about the amp's inner workings as long as it powers up and doesn't quit in the middle of Louie Louie (more important than your listening room, how many tube amps quit at concerts with 15,000 plus people? Nearly zero...for years and years). Very similar circuits as hifi amps in most cases, but hifi gets the "precious/cautious" baggage attached. I recently had a new "Boutique" Class A hand wired all tube guitar head dropped by UPS so hard it bent the entire corner of the amp (heavy "lunchbox" style steel case) and after getting the kinks sorted with vice grips the amp works perfectly with no tube damage or any other damage. The myth of tube amp failure issues continues, and if you're too weak (disabled and extreme geezers excepted) to schlep a dead amp in for repairs or package it in the original box you should have kept, you're a wimp. Period.