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 Post subject: Re: On the 12th Day of Christmas An Amplifier Came to Me
PostPosted: Jan Wed 09, 2019 1:37 am 
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That amp underbelly makes any radio look like a rat's nest. Enjoy!

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 Post subject: Re: On the 12th Day of Christmas An Amplifier Came to Me
PostPosted: Jan Wed 09, 2019 2:05 am 
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'BELL"
Is this the same as bell telephone company ?


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 Post subject: Re: On the 12th Day of Christmas An Amplifier Came to Me
PostPosted: Jan Wed 09, 2019 4:26 am 
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yes, there is lots of room under that chassis for an excellent restoration.

as for "bell", idk if it has anything to do with the telephone company or even the "bell" record label.

steve

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 Post subject: Re: On the 12th Day of Christmas An Amplifier Came to Me
PostPosted: Jan Wed 09, 2019 5:52 am 
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From the Radiomuseum site:


Bell Sound Systems; Columbus (OH)

The Bell Sound model PA3725-B and 3725-B are AC operated 4 channel 25 watt audio amplifiers.
We don't know the difference between PA3725-B and 3725-B. The 4 channels are for 3 microphones plus phono.

6AU6 6AU6 6AU6 6SF5 6N7 6L6G 6L6G 5U4G


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 Post subject: Re: On the 12th Day of Christmas An Amplifier Came to Me
PostPosted: Jan Wed 09, 2019 10:01 pm 
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i saw somewhere that the next level down amp that uses 6V6 in pp, also uses 7B7 and a few other loktal tubes in the preamp and phase splitter.

i bet that made for some nice noisy amps as those stinking PITA pins corroded.

if this were to have loktals, i would have passed it up in a heartbeat.

i wish the 6AU6 tubes were 6SN/L/C7 tubes though. i just like octal tubes the best.

steve

edit: spelling on corroded

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Last edited by Dutch Rabbit on Jan Thu 10, 2019 2:55 am, edited 1 time in total.

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 Post subject: Re: On the 12th Day of Christmas An Amplifier Came to Me
PostPosted: Jan Thu 10, 2019 12:57 am 
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Dutch Rabbit wrote:
i saw somewhere that the next level down amp that uses 6V6 in pp, also uses 7B7 and a few other loktal tubes in the preamp and phase splitter.

i bet that made for some nice noisy amps as those stinking PITA pins corroaded.

if this were to have loktals, i would have passed it up in a heartbeat.

i wish the 6AU6 tubes were 6SN/L/C7 tubes though. i just like octal tubes the best.

steve

I don't have a great many sets w/loctal tubes... but I've never encountered any particular pin-contact problems.
The pins fit as tightly as any 7 and 9 pin tubs ...plus there is a locking lug.

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 Post subject: Re: On the 12th Day of Christmas An Amplifier Came to Me
PostPosted: Jan Thu 10, 2019 4:43 am 
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Pbpix wrote:
Dutch Rabbit wrote:
i saw somewhere that the next level down amp that uses 6V6 in pp, also uses 7B7 and a few other loktal tubes in the preamp and phase splitter.

i bet that made for some nice noisy amps as those stinking PITA pins corroaded.

if this were to have loktals, i would have passed it up in a heartbeat.

i wish the 6AU6 tubes were 6SN/L/C7 tubes though. i just like octal tubes the best.

steve

I don't have a great many sets w/loctal tubes... but I've never encountered any particular pin-contact problems.
The pins fit as tightly as any 7 and 9 pin tubs ...plus there is a locking lug.
I've bought NOS Loctals that had corroded pins, have to be polished up before using. Exposure to damp air, probably.
The other issue I've had is the Loctal sockets with phenolic discs as found in some Philcos. The discs are cracked and broken, maybe from people struggling to remove the tube.
As far as replacing a damaged Loctal socket, I wouldn't hesitate to put in a common octal socket. But it would have to be a nicer than average radio to begin with.
Finally, the price we need to pay now for a 7B7 seems to indicate they are becoming scarce or in high demand.

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 Post subject: Re: On the 12th Day of Christmas An Amplifier Came to Me
PostPosted: Jan Thu 10, 2019 5:18 am 
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i have a few radios with loktal tubes in them. i bought a beautiful crosley bakelite set last summer and threw up a little bit in my mouth when i saw that it was loaded with loktals. it is a beautiful set though and i could not pass it up.

due to past experiences over nearly 4 decades, i have no time for those pain in the hind-end tubes and their sockets that go with them.

yes, the 7B7 and a few other loktals have really skyrocketed. i have a pile of NOS 7B7 tubes. i'm glad i kept them for whatever reason.

the last time i needed a 7C7 for a phlco PT-xxxx radio, their price seemed to be high too. both of these tubes aren't 3-4 dollar tubes anymore.

steve


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 Post subject: Re: On the 12th Day of Christmas An Amplifier Came to Me
PostPosted: Jan Thu 10, 2019 5:40 am 
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I have never used anything with a 6N7 tube. I can't wait to hear how it sounds coupled to those 6L6g outputs.

can anyone tell me about the 6N7 tube and their experience with it ?

reading on the internet, it is a great sounding tube in this application.

steve

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 Post subject: Re: On the 12th Day of Christmas An Amplifier Came to Me
PostPosted: Jan Thu 10, 2019 6:46 pm 
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Dutch Rabbit wrote:
I have never used anything with a 6N7 tube. I can't wait to hear how it sounds coupled to those 6L6g outputs.

can anyone tell me about the 6N7 tube and their experience with it ?

reading on the internet, it is a great sounding tube in this application.

steve
My experience with a 6N7 tube was a shocking experience! A 1939 Cadillac/Lasalle model C-8 car radio uses a 6N7G tube as the audio output. Can you see where this is going? Someone had replaced the “G” version with the metal version, and I found out that this is not a good idea in this case as pin one was used as a tie point for B+. Once bit, twice shy!

Once repaired (and with a 6N7G tube), the radio was a good performer with a claimed 6 Watts undistorted audio output.

http://www.nostalgiaair.org/pagesbymode ... 002525.pdf

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 Post subject: Re: On the 12th Day of Christmas An Amplifier Came to Me
PostPosted: Jan Thu 10, 2019 7:53 pm 
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Very nice amp Steve! I understand about the having to have it in that condition :)

I have many nice looking P.A. amplifiers from that era, but still have yet to acquire a Bell, though that design with the illuminated knobs has always appealed to me...I have not been able to afford the shipping, as few are found west of the rockies.

The 3725B left as is circuit wise would make a excellent instrument amplifier for guitar,keyboard, etc at 25 watts.

Are those red caps "tiny Chiefs" in there or something else? Hard to tell from photo...

Kent


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 Post subject: Re: On the 12th Day of Christmas An Amplifier Came to Me
PostPosted: Jan Thu 10, 2019 10:50 pm 
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IDK what the capacitors are. the cover is back on it.

i am wondering what the 6N7 is going to sound like into those 6L6 tubes. one of the warmest, but yet robust and full of tone combinations that i ever heard was the 6P5 into a 6AC5 in a big emmerson ingraham table set with an 8 inch speaker. it was good for a nice 4-6 watts i'd say. it had such little distortion.

if i get the same sound with the 6N7 and 6L6 configuration, it is going to sound so warm, yet deep, yet crisp, and wonderful.

steve

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 Post subject: Re: On the 12th Day of Christmas An Amplifier Came to Me
PostPosted: Jan Fri 11, 2019 2:35 am 
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Yes, those look like the infamous "Tiny Chief" capacitors. Seeburg and DuKane used them as well; they are just as bad as the "Black Beauties", if not worse.

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 Post subject: Re: On the 12th Day of Christmas An Amplifier Came to Me
PostPosted: Jan Fri 11, 2019 3:43 am 
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All those "Tiny Chiefs" or Gen Ind. red caps would need replacement, Steve, if you really want to hear what the 6N7/6L6G combo sounds like...
Tim is right, in my experience the large .47's and such definitely need upgrading at very least and the caps around the 6L6's,
especially in it's "mint" condition", probably means it wasn't used very much in service so caps have hardened over time...

I had to replace them all in the DuKane 1U/460 type amplifiers I restored a bunch of, years ago, after modifying them for recording before they would sound like anything worth preamping with Hi-Z outputs...

Used to own a Stromberg Carlson that used a 6N7 (metal) , it sounded pretty nice...have a few tube preamps that use that tube as well.


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 Post subject: Re: On the 12th Day of Christmas An Amplifier Came to Me
PostPosted: Jan Fri 11, 2019 3:55 am 
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thanks guys

it will definitely receive a full restoration. resistors will be considered as well, expecially the ones that took a beating. i have lots of room to work with and it will be as neat and perfect as it is now.

i will have lots of time to do it this summer.

steve

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 Post subject: Re: On the 12th Day of Christmas An Amplifier Came to Me
PostPosted: Feb Mon 11, 2019 4:04 am 
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I've never had a problem with or using the standard 59-99 cent yellow capacitor in any of my radios or other high fidelity amplifiers.

they have given me absolutely no problem whatsoever and I was always very satisfied with the tonality.

since this amp is quite the find, especially in the condition that it is in and if I were to want to go a "one up" over the yellow capacitors and get better low value capacitors, what would I use ?

i am certainly not into the "auracap" "janzden" or other high priced audio capacitors.

any suggestions ?

thanks

steve

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