Bastardized '49 5b4 Super

geekmacdaddy

geekmacdaddy

Well-known member
Just got the speaker cab in yesterday to complete this (still gonna change the cathode to fixed bias) project which sounds great. Nothing like fat octal preamp tubes. Never been a fan of the Fender tonestack so went with Baxindall and I'm digging that. Kinda Fender meets Ampeg thing. Bit messy in this tight 12" head cab, but it functions quiet and nice. new supergutz.JPG Super 3.JPG View attachment 3924View attachment 3924 Super 1.JPG super tubes.JPG Super 2.JPG
 
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Damn, that is beautiful. Those metal-case tubes are hard to come by. Vintage Tung-Sols? You must have spent some bux on tubes.
Would you be so kind as to share the schematic?
 
Thank you, kind sir!
Strictly speaking, that tone stack is James, not Baxandall. James looks a lot like Baxandall, except Baxandall is an active tone stack inside a feedback loop with symmetric component values and B-taper pots. Insertion loss is 0dB. James is a passive tone stack with 10x ratio (typically) component values and A-taper pots (you used B). Insertion loss is ~20dB. Ampeg and Orange used James tone stacks in most of their amps. I like what you did with the MID control.

Where are you going to get your fixed bias voltage? does the PT have a winding tap for that? I see you went with DC filaments for the preamp & PI tubes. Because you're using a peak rectifier, the DC filament voltage is higher than 6.3V. You might want to insert a small resistor (something around 10Ω maybe) in series with the AC input to the bridge rectifier to bring the DC voltage down and improve tube life. Make sure that resistor is at least 1W.
 
Chuck D. Bones said:
Thank you, kind sir!
Strictly speaking, that tone stack is James, not Baxandall. James looks a lot like Baxandall, except Baxandall is an active tone stack inside a feedback loop with symmetric component values and B-taper pots. Insertion loss is 0dB. James is a passive tone stack with 10x ratio (typically) component values and A-taper pots (you used B). Insertion loss is ~20dB. Ampeg and Orange used James tone stacks in most of their amps. I like what you did with the MID control.

Where are you going to get your fixed bias voltage? does the PT have a winding tap for that? I see you went with DC filaments for the preamp & PI tubes. Because you're using a peak rectifier, the DC filament voltage is higher than 6.3V. You might want to insert a small resistor (something around 10Ω maybe) in series with the AC input to the bridge rectifier to bring the DC voltage down and improve tube life. Make sure that resistor is at least 1W.
Click to expand...
Decided to stay with cathode. I love the way it sounds. I'll put my fluke on the heaters next time I have'er open, but I don't recall getting more than 6v...if so, will take you up on your suggestion :) thanks. No bias tap on the PT so if I did fixed bias, this is what I'd do.....


High_Voltage_Bias_Tap.png
 
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Chuck D. Bones said:
Cool. That 220K resistor will dissipate almost 1/4W, so Make sure it's at least 1/2W.
Click to expand...
Chuck, I'm going to experiment a bit. Got these schumacher OT pulls from a Lowery Organ that fall into range, curious to hear. I built a bunch of Gibson BR6f type circuits with schumacher OT's from Conn organs, with great success. Also going to put a small choke on the front end for shites and giggles. 2 Schue.JPG
 
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