# Bastardized '49 5b4 Super



## geekmacdaddy (Apr 10, 2020)

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.



View attachment 3924View attachment 3924


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## music6000 (Apr 10, 2020)

Looks Great, Is it an Aluminium Chassis?


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## geekmacdaddy (Apr 10, 2020)

music6000 said:


> Looks Great, Is it an Aluminium Chassis?


Thank you. Yes. Cut every hole (except the IEC) by hand.


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## jjjimi84 (Apr 10, 2020)

What a cool amp! Nice work


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## cooder (Apr 10, 2020)

Awesome, great job! 
I'm thinking of building a 5B6 early Bassman... got the octal tubes sitting here looking at me.


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## geekmacdaddy (Apr 10, 2020)

cooder said:


> Awesome, great job!
> I'm thinking of building a 5B6 early Bassman... got the octal tubes sitting here looking at me.


Oh, do it.


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## Chuck D. Bones (Apr 12, 2020)

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?


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## geekmacdaddy (Apr 12, 2020)

Chuck D. Bones said:


> 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?



Thanks Chuck. I'll share, but I went off the reservation a lot...


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## Mourguitars (Apr 12, 2020)

Man looks great GMD !

Mike


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## geekmacdaddy (Apr 12, 2020)

Mourguitars said:


> Man looks great GMD !
> 
> Mike


Thank you, Mike


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## Barry (Apr 12, 2020)

That's a good looking rig, maybe some sound clips?


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## MightySmallElectrons (Apr 12, 2020)

Too cool!!


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## geekmacdaddy (Apr 12, 2020)

Barry said:


> That's a good looking rig, maybe some sound clips?


Thank you, Barry. Wanted to do that today, but life happens...


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## Chuck D. Bones (Apr 12, 2020)

Those schematics I've seen.  I was asking for a peek under the hood of what you did.


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## geekmacdaddy (Apr 12, 2020)

Chuck D. Bones said:


> Those schematics I've seen.  I was asking for a peek under the hood of what you did.


I used this layout. As a starter. Cathode changed to 250Ω and bypass cap to 25/25 (i'd actully been using a 100uf/100v cap witht the 300Ω). Might try to squeak out a bit more cleanliness and go 240Ω...


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## Chuck D. Bones (Apr 12, 2020)

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.


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## geekmacdaddy (Apr 12, 2020)

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.


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.....


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## Chuck D. Bones (Apr 12, 2020)

Cool.  That 220K resistor will dissipate almost 1/4W, so Make sure it's at least 1/2W.


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## geekmacdaddy (Apr 12, 2020)

Chuck D. Bones said:


> Cool.  That 220K resistor will dissipate almost 1/4W, so Make sure it's at least 1/2W.


Yeah, but as stated, not gonna go there.


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## geekmacdaddy (Apr 13, 2020)

Chuck D. Bones said:


> Cool.  That 220K resistor will dissipate almost 1/4W, so Make sure it's at least 1/2W.


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.


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## Chuck D. Bones (Apr 13, 2020)

Are you talking about a power supply choke or a choke in the audio signal path?


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## geekmacdaddy (Apr 13, 2020)

Power supply.. high B+ and screens


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## HamishR (Apr 15, 2020)

I like to use a choke in the 5E3s I've built.  Tried one on a 5F11 Vibrolux but took it out because it stiffened the sound too much.  In a Deluxe it makes things a little clearer and less spongy. I use it to replace the 5K resistor between the first two filter caps.


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## geekmacdaddy (Apr 15, 2020)

HamishR said:


> I like to use a choke in the 5E3s I've built.  Tried one on a 5F11 Vibrolux but took it out because it stiffened the sound too much.  In a Deluxe it makes things a little clearer and less spongy. I use it to replace the 5K resistor between the first two filter caps.


Exactly what I don't like about the 5E3. You might have just given me the push to finally build one. What value for the 22k dropping resistor next to it? Thanks Hamish


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## HamishR (Apr 15, 2020)

My pleasure!  I've always left the 22K as-is, but also use the "PaulC" mod, which is to change the phase inverter to fixed bias, also known as the Ampeg mod. I'm sure you've heard of it, but you can google it easily enough. Maybe I should have thought about that - but the ams sound great!  I use 22µF filter caps - not really very outrageous I know.

The other big difference from stock is use a Mercury Magnetics "Fat-stack" power transformer. It's remarkable what a difference it makes. I've been told on other forums that it won't make any difference because the voltages are the same, but it's the amount of current available which makes the difference. It's very noticeable and makes the 5E3 a joy if you don't want all that mush.


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## geekmacdaddy (Apr 15, 2020)

[QUOTE="HamishR, post: 22315, member: 174"
The other big difference from stock is use a Mercury Magnetics "Fat-stack" power transformer. It's remarkable what a difference it makes. I've been told on other forums that it won't make any difference because the voltages are the same, but it's the amount of current available which makes the difference. It's very noticeable and makes the 5E3 a joy if you don't want all that mush.
[/QUOTE]

There are many choices. I'll be using Schumacher OT, pull from a lowery organ that was used for 7591's and 7868's. Which PT, andd what spec choke, if you don't mind me asking? Would a 4h 50mA do the trick, factoring possible SS recto?


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## HamishR (Apr 16, 2020)

Ha!  I don't know, but I use a BF Deluxe style choke. I would be careful with using a SS rectifier unless the Schumachers have a low enough B+. Maybe it's because of where I live - we have 240V 50Hz AC which often varies between 235 and 245V - but I often have issues with the B+ voltages being higher than spec. 

The power tranny I last used was the Mercury Magnetics FTDP-E-FS.  The E denotes Export I guess, which is what I need. The FS stands for Fat Stack which I am a huge fan of. You can also get Fat Stack output trannies but I find they suck all the character out - they're efficient and they do what they say but I don't care for the tone. But Fat Stack P/T? Yeah, I like 'em for Fender style amps cuz they seem to deliver enough current to produce low end and not fartiness. I don't really know why they work to be honest, but they do IMO.

I just looked at MM's range of 5E3 power trannies - man, they have a lot of options! I like the idea of a P/T with two different B+ windings.

The only reason I use MM is because of the options. One of the best sounding amps I have ever built was a '68 50W plexi clone with Marstran/Heyboer trannies - it sounded so much like a friend's '68 Plexi it was unreal. I don't have access to Lowery organ tansformers!

And I'm not in Chuck's league where tech knowledge is concerned - I'm a photographer, not an electronics guy.  But I have built a lot of amps!


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## geekmacdaddy (Apr 16, 2020)

HamishR said:


> Ha!  I don't know, but I use a BF Deluxe style choke. I would be careful with using a SS rectifier unless the Schumachers have a low enough B+. Maybe it's because of where I live - we have 240V 50Hz AC which often varies between 235 and 245V - but I often have issues with the B+ voltages being higher than spec.
> 
> The power tranny I last used was the Mercury Magnetics FTDP-E-FS.  The E denotes Export I guess, which is what I need. The FS stands for Fat Stack which I am a huge fan of. You can also get Fat Stack output trannies but I find they suck all the character out - they're efficient and they do what they say but I don't care for the tone. But Fat Stack P/T? Yeah, I like 'em for Fender style amps cuz they seem to deliver enough current to produce low end and not fartiness. I don't really know why they work to be honest, but they do IMO.
> 
> ...


Cool man. Thanks for sharing.


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