Cornwalls II and a 5 wpc tube amp

[big_shooter]

Hello,

I purchased my corn 2's about 7 months ago and am very satisfied. I've been running them with a 1950's 5 watt Magnavox stereo tube amp. I've heard of speakers being better off with more power than less. Is that the case in this situation?

Thanks

[Coytee]

I personally think it depends on how you like to listen.

If you are usually in the room with them then you will have a certain loudness that you will never go for. If however, you do as I do at times and turn things on so you can be downstairs/upstairs or even outside with a window open, having a larger amp comes in handy. I would never use the same levels that my system is capable of while sitting in the room. Using it like that when I'm outside helping the wife mulch her )(#$#*(_|+ flowers, it sounds pretty fantastic.

[Colin]

Amplifiers for Cornwalls

Is five tube watts enough? Yes and no.

In general, recommendations for amplifiers for Cornwalls should be the same arguments for amplifiers for other big ole horns. Yet they are NOT.

The more sensitive a loudspeaker is, the easier an amplifier can provide musical headroom. Twenty watts is all the power that most big ole horns need for many types of music in average size rooms. (BTW, the current of five tube watts is about the same as the current of 20 to 25 solid-state watts.)

The lower the power requirements of a loudspeaker, the more important the quality of the FIRST FEW WATTS. Lower cost tube amplifiers can do just as well – or better - with big ole horns as superlative Pass Laboratories Supersymmetry™ Balanced Single-Ended Class-A X250 monster amplifiers (http://enjoythemusic.com/magazine/archives/).

A wide, flat and dynamic frequency response sounds the best in the long-run. Yet, low or wild impedance curves can indeed give a typical tube amplifier a hard time. The overall frequency response of the loudspeaker is shaped by the driver impedances – because the amplifier can’t control the woofer. Therefore, the bass is often weak.

On the Cornwall, the lowest impedance value is 5-ohms at 20 and 100 Hz and the highest value is 75 Ohms. Nominal impedance corresponds to average "8 Ohms" value. But, according to the Belgium audio site on Cornwalls, it might also be defined as "6 Ohms" as well. Nonetheless, a 5-ohm low is NOT too bad for a good tube amplifier to drive. Ya see, horns LOVE tubes!

Yet, the big 15’ vented woofer of my super-sensitive walnut-oiled Cornwall 1s, with their B2 crossovers, was something special. It gave a broad bump to the 80-100 Hz range. This bump should offset the impedance weaknesses of most tube amplifiers.

I heard more powerful tube amplifiers on big ole horns and one of the most noticeable differences is the bigger (more boomy, usually not tighter or deeper) bass. Therefore, you might consider a more powerful tube amplifier. I didn’t because I loved the delicacy of the 2A3 tubes.

Therefore, I think Cornwalls are EXCELLENT choices for low-powered, but great sounding, solid-state receivers (such as the 70’s vintage Harmon/Kardon twin-transformer, 430-930 series) and low power tube amplifiers.

If it had NOT been for the high-frequency bounce at 5-9kHz, I might never have upgraded my Corns to classic Klipsch corner Khorns – they sounded great, even at loud volumes in a large room with flea-powered tube Bottlehead 2A3 Paramour amplifiers (rated 3.5, 6.5 watts maximum).

1) I did however, add first one, then another, Klipsch sub-woofer to my Corns. That created another problem and I finally ended up with a far more powerful ACI Titan sub with dual crossovers, so the sub only puts out the really deep stuff. A powered sub gives you cheap, class D, solid-state muscle to power the energy hungry deep end. Though adding a powerful sub might be more expensive than steps 2 and 3 below, a sub really adds impact to suspense and thriller movies. Plus it is easy to do. The next two steps are not so simple:

2) Because of the 5 to 9-KHz bump, you might consider upgrading with forum posters ALK, Bob Crites or DeanG crossovers. I heard them and can recommend them highly. They really do smooth out the spectrum. An active crossover can reduce this bump, but it also flattens out the dynamics of the signal. Make sure the new crossovers can be wired with dual amplifiers.

3) Then scout around for a very heavy, solid-state amplifier to drive the bass. Bi-amping has the effect of ten times more power. Bi-amping with tubes allows the better sounding amplifier to power the critical mid and high end. Bi-amping with solid-state allows the more powerful amplifier to drive the low impedance and power hungry low end. A wonderful combination.

Whew! What was the question? Try a friend’s amplifier on your system for a week, see what you like and don’t like…

[Colin]

BTW, I don’t know anything about your Maganvox tube amplifier. It might be a jewel, it might be paste. You should seriously consider having frequent forum poster NOSvalves.com take a look at refurbishing it. It might be worth thousands compared to new tube amplifiers. While he is doing that, either get a used solid-state receiver for a song, or the Trends Audio class T chip amplifier for about $100 to listen to while NOSvalves works his magic.

[big_shooter]

great info fellas,

i appreciate it

[Blvdre]

That looks like the model 196. I just picked one up myself. The seller claims it was fully functional, and that he was currently using it in his shop, but I'd like to refurb it before installing in my system. I was directed to the Magnavox users group forum on yahoo for info. I was able to print out a nice UA and schematic from the files.

[big_shooter]

I'm not exactly sure what model this is. I do know that it has a pair of 5 watt tubes. I pulled this unit from a 1950-60's Magnavox console. It sounds amazing.

Thanks

[big_shooter]

This particular Magnavox amp has the three speaker terminals: C 1 & 2. Before I started using the amp I've never come across this stereo set-up before. I know the "C" is common the others are L R channels. Here is the way I currently have the speaker cables hooked up. Anybody recommend something different?

Thanks

[mike stehr]

Hello, I purchased my corn 2's about 7 months ago and am very satisfied. I've been running them with a 1950's 5 watt Magnavox stereo tube amp. I've heard of speakers being better off with more power than less. Is that the case in this situation? Thanks

Do you want more power?

That's one of the finer examples of the Magnavox single ended 6BQ5 console amplifiers.

The 196 series, uses a choke in the power supply, and has the larger output transformers with a thicker lamination stack/core. That means better bass. Not all of them had the OPT's with thicker laminations.

It was more of simple design with respect to the driver stage. I have the 8600 series of the Magnavox SE 6BQ5 amplifiers. These used a 6CA4 rectifier tube, with a CRC power supply. The output transformers are more smaller, and with less bass of course. They do have good top end bandwidth. The driver stage has a tone compensation network that was connected to the pre-amp's tone controls, and worked around the speakers used in the consoles in the day. Something like that......Some of the 196 series may have been the same with the tone compensation.

But it's only about 4.5 watts per side max. They are great for low to medium level listening in a smaller/small room, like a single ended triode amp I guess.......

Did you buy the amp online like eBay or something? It's appears to be in good shape. Did the seller mention working on the amp?

Is it noisy? Does it hum? Does it sound really objectionable? If it doesn't, then why would someone want to fix something that isn't broke? You may want to maybe replace the aluminum multicapacitor can sometime, and the coupling capacitors, if they haven't been replaced already. A peace of mind kind of thing, and the amp will last many more years.

You can buy four 5-way binding posts, and mount them off the back side of the unit. You would have to drill holes to mount them, and isolate them from the chassis so the posts won't ground to the chassis. Some binding posts have the plastic washer/isolators with them. You can use two common binding posts, and just connect the common wire to both posts, so one can connect the speakers up like a normal stereo.

I have no idea why Magnavox put the speaker connectors right under the PS transformer, it may have because of the way it was mounted in the console.

That little maggotbox 196 is a keeper amp to me. But in the event if you are searching for more power and decide to get rid of it, let me know. I'll buy it. : )

[bkrop]

Are you sure that is a stereo amp and not a mono set up for a tweeter and woofer?

Just asking not trying to cause trouble.

[mike stehr]

Are you sure that is a stereo amp and not a mono set up for a tweeter and woofer?

Just asking not trying to cause trouble.

Ways to tell are the two inputs, channel one and channel two. Two similar looking output transformers, which a choke would probably look different. The 196 amp in the thread has the PS choke underneath the unit.

Two speaker outputs, (channel one and two) with a common ground for the speaker negative.

Magnavox did make a 6V6 (push-pull?) mono console unit which used kind of a similar chassis. The large 6V6 Magnavox console amplifiers set up for bi-amping used a larger chassis.

[bkrop]

Thanks! I look for transformers above board and thought they were chokes along with pairs of splitter/[reamp tubes.