BFPR AA1164

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eddiejg
Senior tube assistant
Posts: 232
(2/25/04 2:15 pm)
 BFPR AA1164
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 I finished building my AA1164 last night & only killed 1 bias cap because I installed the diode backwards (why does the schematic indicate the cathode with a + sign on the layout).
Even so, I was pleasantly surprised that that was my only problem considering the poor readability of the schematics & layouts fo this amp.
Anyway, now that I finished the amp, I'm trying to figure out how to properly bias the amp, since this is my 1st 'fixed' bias amp.
Am I right to understand that the most important factor overall is still actual plate dissipation & not so much milliamps & volts?
I'm setting the bias voltage to -34 (pin 5 to ground) & getting ~32mA (across each 1 ohm cathode resistor) & 420 volts (pin 4 to ground).
That comes out to ~13.5 watts (including the screen current) & no red lining.
I'm reading in the Torres book that this amp should be -29 volts & ~18mA.
I'm never going to get that.
Should I care?
-Ed
 
Casey4s
Senior tube assistant
Posts: 137
(2/25/04 2:28 pm)
 Re: BFPR AA1164
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 It would make life easier to install a bias adj. pot.

Where you set your bias dictates what % of the tubes max dissipation you are using.

I just built a DIY BFPR last spring, and I put a bias pot on mine that is accessable without pulling the chassis. I also installed bias test jacks and a Plate Voltage test jack.

Good luck with your project...

My DIY BF Princeton Reverb

Casey4s
 
eddiejg
Senior tube assistant
Posts: 233
(2/25/04 2:37 pm)
 BFPR AA1164
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 Casey-
Nice amp!
Yes, I did install the bias adjustment pot.
But, I put it on the internal board with the rest of the bias circuit.
Not a big deal, I could always re-locate it, but I think I'd rather have it inaccessible.
I'm mainly trying to get some real-life #'s from people right now.
What voltages & amperages do you have yours set at?
Also, what speaker did you go with.
Thanks.
-Ed
 
Casey4s
Senior tube assistant
Posts: 138
(2/25/04 2:46 pm)
 Re: BFPR AA1164
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 I used a 12" Alnico speaker.

If your plate voltage is 420vdc, and a 6V6GT is max 14w max dissipation.

divide 14 by 420 = .0333 amps or 33ma (100%) to get say 60% then multiply 33 x .60 = 19ma. I run mine at 70%.

Casey4s
 
eddiejg
Senior tube assistant
Posts: 234
(2/25/04 3:57 pm)
 BFPR AA1164
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 Yeah, I'm testing it with an Eminence 1228P & a Jensen P12Q.
I think the P12Q wins with this circuit.
I was playing around with the bias using an old set of EH 6V6's.
I recently got a set of the new JJ 6V6's for this amp, so I installed them, re-adjusted the bias & now have around -36 volts, 430 volts & 22 mA.
I think that works out OK.
I think the JJ's are supposed to be able to handle that.
We'll see.
-Ed
 
Casey4s
Senior tube assistant
Posts: 139
(2/26/04 12:28 am)
 Re: BFPR AA1164
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 I'll be looking forward to seeing some photos.

What are you going to do for a cabinet?

BTW, my speaker is an Emminence Alnico 12" (35 Watt), I think it sounds damn good, and it only cost me $39 + $5 SH.


Casey4s
 
eddiejg
Senior tube assistant
Posts: 235
(2/26/04 12:58 am)
 BFPR AA1164
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 Casey-
I built a pine cab with a birch baffle-board.
I'm using a black vinyl laminate for the covering.
Where did you get the Eminence for that price?!?!?
I really like those speakers, but usually pay $60 for them.
I've also enjoyed the 10".
The 20 watt 12" I have right now I hadn't tried before.
It sounds fine, but I thought the Jensen had cleaner bass.
And with the limited clean on this, I'll keep the Jensen in this amp.
At least until I get to try some mods, like the Paul C. mod & a couple of master volume setups.
I think for a master volume to be useful, it will have to be something that adds to the overall power/gain.
Otherwise, the MV pot is always going to be on 10.
Did you make any mods to yours?
-Ed
 
Casey4s
Senior tube assistant
Posts: 140
(2/26/04 3:55 pm)
 Re: BFPR AA1164
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 Eddie,

I got the speaker from Dave at Avatar cabs last year.

Other than the stuff in the bias circuit, the only changes I made was to add a "MID" control, a "Presence" control, and a "Dwell" control for the reverb.

Casey4s
 
HotBluePlates
I only work on Fender's
Posts: 694
(2/29/04 10:18 am)
 Re: BFPR AA1164
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 I used to own a blackface PR, and before I knew anything about fixing amps, I took it to Dave Funk (back when he had a shop in Nashville). He set the bias for 22mA of idle current.

From the math above, that looks like about 70% dissipation at idle.
 
tubenit
Junior tube assistant
Posts: 35
(3/1/04 9:42 am)
 Re: BFPR AA1164
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 I noticed the comment about difficult to read schematics for the AA1164. About a year ago, I found a very clear/crisp easy to read schematic for a PR with boost pedal. If you ignore the boost pedal section and notice the cathode section on the 12AT7 and a cap/resistor that is different than the 3.3K w/10pf ....... it matches up real well with the AA1164. Also I used a ruler and caliper to make a close to real size layout for the circuit board. Then I re-drew the layout so it is around 11" x 2&3/4" (then I digital photo'd it so I could put it on a disk). I'd be happy to e-mail of post those if someone could offer some direction on how. I am quite new using this amp forum. While I don't remember the original web source, I do have a copy on a floppy disk. The schematic I found was:

Fender/Rogers/Rhodes
schematic domestic and export Princeton Reverb Amp with boost pedal Part 014875

I have e-mailed the above mentioned schematic to schematic heaven today hoping they will post it. It's very easy and clear to read.However, I would be happy to e-mail it or post it another place if someone wants to give me directions on how to do that?

Edited by: tubenit at: 3/1/04 12:06 pm
 
eddiejg
Senior tube assistant
Posts: 238
(3/1/04 3:05 pm)
 BFPR AA1164
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 Casey-
Thanks.
I'll try him when I go to buy my next speaker.

HBP-
I wound up at 20-22mA.
Works well, sounds great!

Tubenit-
I'd like a copy.
I was considering adding a boost switch.
eddiejg*@hotmail*.com*.
Take out the *'s.
Thanks.

-Ed
 
tubenit
Junior tube assistant
Posts: 36
(3/1/04 5:47 pm)
 Re: BFPR AA1164
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 I will try and mail this to you from home tonight. & then from work tomorrow as that might work better. tubenit
 
 
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