Anyone familiar with 6146A?

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Ears
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Anyone familiar with 6146A?

Post by Ears »

Is anybody familiar with using this beam tetrode? It has no mention in my RCA manual RC-28.
But RCA 6146A NOS is seemingly readily available from the mainsteam supplier RS Components. A quick look at the attached datasheet (from PMillett's) seems to indicate a versatile very high power tube in a small package (can get 70W from a pair into 5K5 load, Va=500V or 120W, 8K, Va=750V).
I could put up with the top caps, (actually they look cool).
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joebob
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Re: Anyone familiar with 6146A?

Post by joebob »

That tube and it's several variations are a mainstay transmitting tube for Hams, has been for many many years. I have never used one in a guitar amp but on another forum someone built an amp with 2 and was pleased, that was awhile ago.

My first ham transmitter I built used one, excellent tube. The pix shows another variant, a JAN 6146W. I was going to build another xmitter but never got around to it.
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tubetek
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Re: Anyone familiar with 6146A?

Post by tubetek »

The original Ampeg SVT used six of these to good effect. I'm not sure why
they switched to 6550. Anyway, if you can get them at a good pricem build away. (i'd probably lay in a few extra)
Tom
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Ears
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Re: Anyone familiar with 6146A?

Post by Ears »

joebob wrote:That tube and it's several variations are a mainstay transmitting tube for Hams, .
And that also explains why its not in the receiving tube manual!
Thanks for the information :)
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jaysg
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Re: Anyone familiar with 6146A?

Post by jaysg »

tubetek wrote:The original Ampeg SVT used six of these to good effect. I'm not sure why they switched to 6550. Anyway, if you can get them at a good pricem build away. (i'd probably lay in a few extra)
Tom
I picked up the Ampeg story book at BookStar and read the SVT story. They intended it for Bill Wyman only, and were horrified when they found Richards cranking it with a guitar. All the 6146s were red-plating. At least one guy was there the whole tour, keeping the amps alive, doing mods on the road. I think Ampeg learned how hard touring is on the hardware, and they had trouble keeping the plate wire/caps intact. That's a lot of voltage flopping around on a long wire. I don't know if they lowered B+ for the 6550s, but you can usually run a much higher B+ with the cap approach.
Andy Le Blanc
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Re: Anyone familiar with 6146A?

Post by Andy Le Blanc »

6550's has a max plate dissapation of 35 watts..... more watts less hassel
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Ears
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Re: Anyone familiar with 6146A?

Post by Ears »

Andy Le Blanc wrote:6550's has a max plate dissapation of 35 watts..... more watts less hassel
Reading replies to this thread caused me to re-read O'Connor on the SVT.
He writes that two issues surrounded the change to 6550A in the SVT, firstly that the 6146, being a transmitting tube, increased liklihood of high freq oscillation problems, as the FB loop was across 3 gain stages . Secondly, the screen voltage is very much lower than the anode voltage in the 6146 (250V vs 750V), this was a result of the tube architecture which allowed such a high gm and sensitivity. He implies it's much easier to design a supply when you can run the screens close to the plates.

[5 Aug. Edited an error in number gain stages stated in the original post and better clarified my reading of O'Connor.]
Last edited by Ears on Mon Aug 04, 2008 8:28 pm, edited 2 times in total.
Andy Le Blanc
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Re: Anyone familiar with 6146A?

Post by Andy Le Blanc »

sounds like a need to balance practicalities...... SVT was and is a beast
a friend used to slep one through Harvard and Cambridge Mass.. on the T ..
at the time it was worth it...... if it had had other issues .... may be not....
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FUCHSAUDIO
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Availability

Post by FUCHSAUDIO »

According to a few people I know from the early days of Ampeg, it came down to availability of quality 6146's.
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skyboltone
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Re: Anyone familiar with 6146A?

Post by skyboltone »

There are a ton of transmitting tubes that are better at audio than a 6146A. Like 811s or 813s. In quality AM transmitters the audio is layed directly on the plates of the output tubes, creating two "sidebands" which are the sum and difference of the audio frequency and the carrier or broadcast frequency. This is called modultation. I have never seen 6146s used as the modulator tube. At that power level, usually 807s which are a pretty crappy audio tube. We used to replace the 807s with 6CA7s for a much more punchy and full frequency modulator.

One problem of using transmitting tubes in audio applications is the voltage used. If you happen to catch 450VDC across your hand, or worse, from hand to hand, you'll usually be ok. Depends on the condition of your heart. But if you catch 2000 volts through the heart, it's so long baby. These tubes are really out of place in a hobby amp builders arsenal. My opinion. YMMV

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David Root
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Re: Anyone familiar with 6146A?

Post by David Root »

The 6146B has the same Pa rating as the 6550, 35W. The other 6146s (-A and -W) are 25W.

I have looked at the 6146B as a good hi fi amp choice, when plate and screen each have their own supply, because you can then play with diodes on the screens to force more AC signal into the plates, and other esoteric stuff. +100W from a single pair is easy. Plus, they're a LOT cheaper than NOS 6550s! Downside, as one of us mentioned earlier is you typically run around 1kV plates which requires safety measures like enclosed chassis with the cover locked.

6550s make more sense to me for MI use. No cap/HT cord, (safer), screens can be run much higher.
arska
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Re: Anyone familiar with 6146A?

Post by arska »

Project amplifier Tremelo King2 :

Two Raytheon CK6146A in normal Fender style output with bassman 50W
output transformer, anode voltage 365V and screen grid voltage 180V.
Use Zeners for making 180V. The sound is tight, focused and different
than 6L6, worth of trying!!!!!

I might send schematic if anybody like to try.

Arska
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