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Post subject: NAD Start of Build Thread
Posted: Mon Jan 09, 2012 8:46 pm
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Rock Star
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Got a new amp...1969/70 Bantam Bass Amp. Going to use it as a project amp. Going to clean it, revamp it with a new baffle board and replace that Styrofoam Yamaha speaker with two 68 Jensen C12N's. This should make a sweet 30 Watt 2X12 amp. Here are a few pics.

If anyone has any input to this re-build let me know. I invite everyones ideas and helpful hints to follow. These are I guess my before pics. This may take me a couple of weeks or a month maybe. I will be taking it apart and cleaning it thoroughly this next week or so.

And lastly, anyone have a schematic for this one? Been having had a hard time finding one.

T2

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Post subject: Re: NAD Start of Build Thread
Posted: Mon Jan 09, 2012 9:10 pm
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I've never understood the reasoning behind that speaker,I mean.....styrofoam!!
Otherwise the amp looks to be in great shape.


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Post subject: Re: NAD Start of Build Thread
Posted: Mon Jan 09, 2012 10:12 pm
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Here's the layout:

http://elektrotanya.com/fender_bantam-b ... nload.html


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Post subject: Re: NAD Start of Build Thread
Posted: Tue Jan 10, 2012 7:57 am
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BTW... new Yamaha speakers and "fix-it" kits are near unobtanium, these days. I would pull that speaker and the baffle. Get or build another baffle for a 15-inch speaker. And store the Yamaha in a cool enviroment, maybe even seal it in clear wrapping plastic.

I would not use it. Or even expose it to any enviroment that could damage the styrofoam.


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Post subject: Re: NAD Start of Build Thread
Posted: Tue Jan 10, 2012 4:49 pm
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Reb and SK...yeah who'd a thunk it...Styrofoam! I think that one has CBS Corporate written all over it...something like the following...CBS VP..."I was talking with this guy from Yamaha corp at lunch yesterday and they have this revolutionary speaker, said we could have it cheap if we order like 500, that will cut the costs of speaker procurement by a third for our division". "I am going to propose this at our next sales meeting".

...and low and behold Fender ends up with the goofiest frickin speaker ever made...I don't ever remember seeing Yamaha use it in any of thier guitar or bass amps! I could be wrong about that, but then again, Yamaha ain't known for thier great Amps!

BMW...thanks for the advise on taking it out and making a new baffle, exactly what I intend to do with it. I just don't know if I want to go with 2x12 or a 1x15. The 1x15 would be easiest, but would really like to go 2x12. And also thanks for the Schematic!

This is going to be a whole new chapter for me.

T2

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Post subject: Re: NAD Start of Build Thread
Posted: Tue Jan 10, 2012 5:40 pm
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T2Strat... remember those old funky speaker drivers that supposedly could make your entire wall a speaker? For that "Wall of Sound" tone? That was the idea behind the Yamaha speaker. Notice how the styrofoam is flat and not a cone? Why they chose styrofoam... you'll need to read Japanese and dig up some early 1970's Yahama brain-trust files. :lol:

Two problems. Styrofoam breaks easily. And the VC and driver need to be on the weak side... to prevent the speaker from blowing out, while in the showroom. Really, that speaker should be rated for about 10 watt RMS---MAX. And certainly nothing below 400Hz. Which makes the whole thing really crazy in a bass amp.

But, there are American Picker type nuts out there that value the real OEM stuff. Even if it didn't work. So SAVE that Yamaha relic!


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Post subject: Re: NAD Start of Build Thread
Posted: Tue Jan 10, 2012 7:23 pm
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BMW2002Ti wrote:
T2Strat... remember those old funky speaker drivers that supposedly could make your entire wall a speaker? For that "Wall of Sound" tone? That was the idea behind the Yamaha speaker. Notice how the styrofoam is flat and not a cone? Why they chose styrofoam... you'll need to read Japanese and dig up some early 1970's Yahama brain-trust files. :lol:

Two problems. Styrofoam breaks easily. And the VC and driver need to be on the weak side... to prevent the speaker from blowing out, while in the showroom. Really, that speaker should be rated for about 10 watt RMS---MAX. And certainly nothing below 400Hz. Which makes the whole thing really crazy in a bass amp.

But, there are American Picker type nuts out there that value the real OEM stuff. Even if it didn't work. So SAVE that Yamaha relic!


BMW...I do vaguley remember that "Wall of Tone" stuff back in the day. Nope don't read Japanese and as for the Yamaha brain trust files...I think those got flushed, used for TP or both:!: :lol: That post of yours have me rolling, funny stuff :lol:

10 Watts sounds about right.

I am going to keep the speaker and put it up along with the baffle board for "Posterity" some crazy nut might just want it one day! :shock:

Thanks again.

T2

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Post subject: Re: NAD Start of Build Thread
Posted: Thu Jan 12, 2012 8:44 pm
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Well I took the amp all apart tonight with the exception of removing the grill cloth, which I plan to reuse. I have decided to go with a Vintage 15 inch Jensen with Bell Cover for my speaker.

The cab was in good shape, but some of the hardware is a little ruff, so going to replace the guides and corners with some NOS parts. The tilt legs cleaned up good enough to keep so they will go back on. Here are a couple pics of the chassis and cab. Still need to clean the grill cloth, that is on the agenda for tomorrow...along with removing it from the baffle for reuse.

Image

Image

Image

Image

T2

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Post subject: Re: NAD Start of Build Thread
Posted: Thu Jan 12, 2012 9:31 pm
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T2Strat, you know that amp kinda looks similar to the Bassman 10. Here's the schemo. May help a bit:

http://www.webphix.com/schematic%20heav ... _schem.pdf


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Post subject: Re: NAD Start of Build Thread
Posted: Fri Jan 13, 2012 4:41 pm
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BMW...Thanks for the schematic. It does look kind of close, although I am no expert at reading schematics. How far apart from a black face bassman do you think amp is? 30 Percent difference maybe?

I was just reading through Dave Funks Tube Amp Workbook Vol I (Fender) and it say the Bantam was derived from the Bassman but with one less pre-amp tube. Then it says due to the speaker it was discontinued and the Bassman 10 was derived from the Bantam but used 4x10 conventional speakers with a closed back.

I am getting ready to go remove the grill cloth...wish me luck!

T2

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Post subject: Re: NAD Start of Build Thread
Posted: Fri Jan 13, 2012 11:51 pm
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T2Strat, in my opinion... this amp is pretty close to the older BF circuits, than say the UL Fender amps. A new speaker(s) --- whether one 15-inch or two 12 or 10-inchers (if you're doing lead stuff)... I think you'll have a pretty nice combo amp.

No reverb or vibrato can be ok. Just need some foot action. :D


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Post subject: Re: NAD Start of Build Thread
Posted: Mon Jan 16, 2012 5:33 pm
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Time for an update. Grill cloth cleaned. Used 409 cleaner and let it sit for about 15 minutes then rinsed it out in the utility sink...wow talk about dirty water! But it is much cleaner, not new looking but much better. Got the baffle board cut...now have to wait for the 15 inch Jensen Speaker, some glides and corner pieces to arrive from source in southern AZ before I begin the speaker cut out and test mounting.

I did have to do some touch up work to do on the cab, a couple of bit of the tolex is coming loose on the front and back at the bottom and one small section at the top.

Image
Pic of the re-attachment of the tolex and the rear edge will get the same tomorrow evening...
Image

I am thinking this amp either got some water damage or sat some where that was damp as the only tolex problems with coming undone was the bottom. Well...that is it until my parts arrive...sorry the pics are not the best.

T2

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Post subject: Re: NAD Start of Build Thread
Posted: Mon Jan 16, 2012 5:53 pm
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T2Strat, those are great pics. I always thought the Bantam and Bassman 10 would make good platforms. Your project should turn out great! Art

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Post subject: Re: NAD Start of Build Thread
Posted: Mon Jan 16, 2012 7:51 pm
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aclempoppi Me Too! I had a line on another Bantam, but it got sold before I could make it over to look it over real good. But this one was in better shape on the outside, so I guess I was supposed to wait...

I like the Bantam because you get the extra Middle control for a little extra knob twiddling that you don't with the other Bassman derivatives.

I can't wait til it is done, I laid out my plan so I would have to take my time and pay attention to the details. I have done all I can for now, waiting on parts to come in the mail.

T2

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Post subject: Re: NAD Start of Build Thread
Posted: Sun Jan 22, 2012 1:07 pm
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Update time. This is the speaker I chose, and it should arrive anyday now, and I can move forward and get this build completed. Anyway here is the speaker...

Image

This will be the first amp I have with a 15 inch speaker in it and am looking forward to sonic difference over my SFSR.

T2

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