Why?

[bahern]

I have to admit that I am electronically challenged. I was looking on the net today to learn about the pros and cons of wiring in series, parallel, and both. I incorrectly assumed that 8 ohm speakers were easier to drive than 4 ohm speakers. I have found differently. Then comes the question. These tube amps that put out small amounts of watts will often require 16 ohm speakers. Why? Would that not make a small amp have to work even harder in order to drive that load?

[cjd]

Lower impedance takes more current.

[bahern]

> Lower impedance takes more current.

Are you saying that resistance and impedance are not the same?

[thylantyr]

>These tube amps that put out small amounts of
>watts will often require 16 ohm speakers. Why?

Dinosaur technology :)

Soon a big meteor will hit earth and all tube
amps go extinct.

[davidyohn]

> Are you saying that resistance and impedance
> are not the same?

That's correct, resistance and impedance are not the same. Resistance is based on the DC characteristics of a medium. Inductance adds to that and resistive components contributed by the inductance and capacitance of the medium when conducting AC, and changes with the frequency.

Impedance ratings of loudspeakers are usually averages, or measured at a specific frequency.

Higher impedance loudspeakers are "easier" to drive because, as implied above, they draw less current from the amp at a given voltage.

[bahern]

> That's correct, resistance and impedance are
> not the same. Resistance is based on the DC
> characteristics of a medium. Inductance adds
> to that and resistive components contributed
> by the inductance and capacitance of the
> medium when conducting AC, and changes with
> the frequency.

> Impedance ratings of loudspeakers are
> usually averages, or measured at a specific
> frequency.

> Higher impedance loudspeakers are
> "easier" to drive because, as
> implied above, they draw less current from
> the amp at a given voltage.

Thanks.

[jtaylor]

> Dinosaur technology :)

> Soon a big meteor will hit earth and all
> tube
> amps go extinct.

I had an old Visual System on my Flight simulator that used Tubes to drive the High Voltage section, TUBES SUCK... We had more maintenance problems with them tubes than anything else on that simulator. We replaced the tubes every 90 days whether they needed it or not so they wouldn't blow up a bunch of other stuff when the tubes died. We also had to keep them turned on 24/7 so they would stay stabilized and not require a daily alignment.

When the Headquarters finally decided to spend the money to go solid state, we were in heaven. No more tube failures or major component damages from tube problems. We hardly had any problems with the visual once we were rid of them dang tubes. We didn't have to adjust the heater voltage and anode amps on an almost daily basis once the tubes were gone. Tubes are also ungodly expensive, and Solid state is the only way to FLY.

J. Taylor

[davidld]

> Thanks.
To successfully drive a low-impedence speaker to loud volumes you need a robust and expensive power supply. Most modern amps simply warn you to use 8 ohm speakers than to spend the extra money to build. However, many vintage amps successfully power 4 ohm and sometimes even lower impedences.

David

[envisionelec]

> When the Headquarters finally decided to
> spend the money to go solid state, we were
> in heaven.

Was this last year? *snicker*

[waynew]

My own personal preference is Solid State, but I get a lot of enjoyment out of listening to music and basking in the warm light of my glowing Svetlana's and Tesla's. I also like tinkering with the Bias and comparing it to my Musical Fidelity. Sure,they have their up's and down's, but that doesn't mean that they are the devil's handmaiden.

[wg_ski]

> Sure,they have their up's and down's, but
> that doesn't mean that they are the devil's
> handmaiden.

Yes they are. The blue halo on the inside of the glass is actually the Dark side of the Force, and sends you subliminal messages that say "Build more tube amps... Spend money you don't have...."

[waynew]

> Yes they are. The blue halo on the inside of
> the glass is actually the Dark side of the
> Force, and sends you subliminal messages
> that say "Build more tube amps... Spend
> money you don't have...."

Hmm...now that you mention it, it does look like the lightning that the Emperor used to fry Luke Skywalker with. Maybe I am walking a fine line on the edge of the Dark Side

[Pete Schumacher ®]

> To successfully drive a low-impedence
> speaker to loud volumes you need a robust
> and expensive power supply. Most modern amps
> simply warn you to use 8 ohm speakers than
> to spend the extra money to build. However,
> many vintage amps successfully power 4 ohm
> and sometimes even lower impedences.

> David

If you're going to drive a 4 Ohm load with a linear amp, you'll be dissipating quite a bit more power in the output stages, raising the junction temperature quite a bit. The weak link in most amps is handling the heat. If you want low impedance capacity, you need more than just a big power supply, you need a big heatsink to keep the output devices from failing.

Yeah, raw sine-wave power requires a large power supply, as well as large heat handlers. But a 250W amp under music loads will only see between 25W and 50W RMS power before clipping occurs. That's not a problem with the amp, but the nature of the signal. Music is NOT a sinewave. Which means you don't NEED a power supply to be able to provide a continuous 250W to an amp rated at 250W when it's driving a full-range musical signal without clipping.

[kene]

> Hmm...now that you mention it, it does look
> like the lightning that the Emperor used to
> fry Luke Skywalker with. Maybe I am walking
> a fine line on the edge of the Dark Side

I've been on the Dark Side for a while now, but never before in the realm of tubes. I shall soon expand my training as a Sith apprentice.

[Andy_G]

> I've been on the Dark Side for a while now,
> but never before in the realm of tubes. I
> shall soon expand my training as a Sith
> apprentice.

I am sort of toying with the idea of building the very best 35-50w tube monoblocks amps I can.

Anyone know where to start ?? A really good kit for instance ??

ps: I still love my Dynacos :-))
just wondering if I can do even better in the tube amp realm.

[damkor]

> ps: I still love my Dynacos :-))
> just wondering if I can do even better in
> the tube amp realm.

Are you saying that you love the solid state Dynacos, like the ST-70 or ST-120? You can certainly do better than that, SS or tube.

[Andy_G]

> Are you saying that you love the solid state
> Dynacos, like the ST-70 or ST-120? You can
> certainly do better than that, SS or tube.

I have a pair of Dynaco MkIV tube mono-blocks at the moment. Just wondering if it is possible to make something toob, that is even better.

[jtaylor]

> Was this last year? *snicker*

What is the "SNICKER" all about? Actually the Visual solid state update took place about maybe ten years ago. It's a little hard to remember as I haven't worked in about ten years as I battled Social Security to get my Disablity Payments for over four year years and just started receiving payments. You better thank your lucky stars that you remain in good health and don't have to battle the system to get your money to live on. I really miss working and having to live on Drugs to handle the chronic pain I now suffer.

J. Taylor

[envisionelec]

> What is the "SNICKER" all about?
> Actually the Visual solid state update took
> place about maybe ten years ago. It's a
> little hard to remember as I haven't worked
> in about ten years as I battled Social
> Security to get my Disablity Payments for
> over four year years and just started
> receiving payments. You better thank your
> lucky stars that you remain in good health
> and don't have to battle the system to get
> your money to live on. I really miss working
> and having to live on Drugs to handle the
> chronic pain I now suffer.

> J. Taylor

Oh, just that government contracts sometimes involve using outdated technology well past its use-by date.

I REALLY HOPE you didn't think I was snickering at YOU.

[filmboydoug]

Yup. Everybody knows solid state is superior. Tubes just sound better.

> Dinosaur technology :)

[damkor]

If I had a little more FU money, I would probably make the Bottlehead SEXAMP and get four Fostex FE206e. Put two drivers per cabinet, maybe one pointing out back, some sort of horn perhaps, filter one of them at 500Hz or so, according to the baffle step, filter the front one maybe a tad to equalize the treble, and get a true 97dB system. Maybe play with a super-tweeter.

[jtaylor]

> Oh, just that government contracts sometimes
> involve using outdated technology well past
> its use-by date.

> I REALLY HOPE you didn't think I was
> snickering at YOU.

Actually at that time the company was owned by General Electric and I had the only remaining field site left. They slammed the doors shut on our 747 in Newark, New Jersey when it quit being a gold mine for the company. Since we were the only Flight Simulator in the Company pulling in a huge profit, they didn't want to spend money to improve it.

The Visual System and the Main Frame Computers were so old they were almost antique. When they finally did most of the upgrades, GE sold the company off, and the Canadians Stole our simulator and dumped everyone on the spot. Of course we got Severance pay for all our years of service, 25 and a half for me.That was the last time I ever went to work.

If you want to "Snicker", go and apply for disability benefits. What a Government nightmare that is. I'm glad I had prepared for the timely process, I had to live of the money I had saved to last over 4 years before my payments started. At least in the end they paid me retroactive to all the way back when I first filed.

J. Taylo