martin manning wrote:Yes, those first two radial caps do look big enough to be 220uF. Your schematic shows a GZ34, so that's what I assumed you assumed. I agree the bottle in the picture does look like a 5U4. The 5U4 has both a lower series resistance requirement and a larger voltage drop, so the purpose of the series resistors is still a bit mysterious.
Did you get a primary resistance for the PT?
I never know the best way to update the schematic. I'll start putting them in the first post of the thread. I just changed my mind on the rectifier tube to 5U4 yesterday when I was rummaging through my tube box and came across one.
I have been playing the amp this AM but I'll check and post the primary resistance.
IC, looking at the Manzamp pic I think this is the exact rectifier in the Manzamp. At first I thought it might have been the fat bottle GZ34, but the getter spacing at the top of the envelope is different. So like you guys said, it appears to be 5U4.
TM
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To be quite honest I have a rather hard time believing that HAD used 110uf on a 50w Bassman modded amp with a tube rectifier..That to me is borderline silly.. Either you want sag or you don't ..Dumble used all kinds of filter caps in all his builds..Sure the ones in the pic look big but when it comes to caps that doesn't always give you a clear idea about there values..Perhaps if we knew there type and voltage rating but in this case we have neither.With 110uf you could risk loosing some sustain/bloom and harmonic content (ripple is a part of tone in a Bassman) I would think..
My .02 cents
Tony
Last edited by talbany on Sun Feb 10, 2013 9:25 pm, edited 3 times in total.
" The psychics on my bench is the same as Dumble'"
To be quite honest I have a rather hard time believing that HAD used 110uf on a choke loaded 50w 34 Bassman modded amp with a tube rectifier..That to me is borderline silly.. Either you want sag or you don't ..Dumble used all kinds of filter caps in all his builds..Sure the ones in the pic look big but when it comes to caps that doesn't always give you a clear idea about there values..Perhaps if we knew there type and voltage rating but in this case we have neither.With 110uf you could be loosing some sustain/bloom and harmonic content (ripple is a part of tone) I would think..
Good thought on the capacitor. I don't have any pictures or schematics of 50W Dumble amps with Precision power supply. Anyone?
The capacitors selected were based on the picture.
The 100uf /350v Nichicon sold by Mouser are 5mm smaller than the ones in the Manzamp pictures. The 220uf/350 and all the others match.
"You feel like you're floating on a football field filled with marshmallows." -Dumble
Beautiful build!
Today the caps have much more capacitance per size than already a few years ago, so estimation of capacitance based on size will likely be an over-estimate.
Why would HAD put a Precision Power Supply in a Bassman amp if he wanted more sag? Maybe to save space? Why not just use a power supply like #102, with less reservoir filtering? The clips sounded very good, maybe IC assumed right. What ever the case may conclude, I think the amp has some great sonic characteristics.
At this point I'm going to say that the amp I build does not beak-up and distort when pushed. It sustains but it is acting more like a Fender Twin or other amp with clean headroom.
I don't know if the original Manzamp was supposed to be like that.
Some big potential differences:
My Replica Manzsamp: Higher power aftermarket PT giving pretty high voltages all over.
Original Manzamp: Looks like vintage original Fender Tweed Bassman PT with thin cloth covered wires.
My Replica: 110uf first filter stage
Origina Manzampl: Lower? Half that? As others pointed out capacitors could have been the same diameter and just shorter or a different composition. Capacitors on the market do seem to get smaller and smaller each time they re-design them.
My own thoughts are like CHIP pointed out. Why mess with the 5f6a circuit and put a precision power supply on it anyway? For my replica, it works out great in that the amp sounds better than my other amps with distortion pedals going into it and has really nice cleans.
So, I'm going to keep this current build pretty much like it is.
I have posted the layout for the PC board. Maybe JazzGuitarGimp or someone else can manufacture some PC boards. I think with a pre-made PC board and a larger chassis, someone should be able to build one of these pretty quickly.
Last edited by ic-racer on Tue Feb 12, 2013 3:39 am, edited 1 time in total.
"You feel like you're floating on a football field filled with marshmallows." -Dumble
Got my "Manzamp" build ready.
I had to adjust the psu dropping resistors to get the voltages near to the bassman values. Now they are near but not perfect. My plates are around 427v right now with Telefunken EL34's. I tried it with other EL34's and plates were about 3v higher.
I'm not sure should I alter the dropping string values to get the P.I voltage to bassman or Dumble specs?
First impressions (with tele and strat into 2x12" 72' greenback semi open cabinet):
It has kind of bright tone in it and I'm experiencing a lack of bass a bit. There supposed to be plenty of it available?
Also the mid pot seems to be very interactive and I'm getting kind of only upper mid boost with it.
The midrange doesn't sound very pleasing to me at the moment, kind of "hard" on the mids.
Is the skyliner supposed to sound like that?
I was expecting more of a fuller, sweeter sound and some deep bass.
It totally has lots of clean sound available.
Never played with skyliner eq before so I don't know what to expect from it and how it "should" behave.
But hey, it works!
Now just the endless fine tuning procedure...
I'll post some pics when I get my camera to my workshop.
ic-racer wrote:I have posted the layout for the PC board. Maybe JazzGuitarGimp or someone else can manufacture some PC boards. I think with a pre-made PC board and a larger chassis, someone should be able to build one of these pretty quickly.
Hi IC,
My specialty is in PCB Layout. If I need a board fabled, I send it out to a fabrication house. My layout software is not curve-friendly enough to emulate your beautiful curvy (groovy 60's) traces; it likes to keep things on the straight and diagonal. So, I could create a layout, but I could not make it look the way yours does. Whether or not that would affect the sound of the amp couldn't be known until someone built one.
I am totally stumped as to why someone would take an Old classic great sounding circuit such as the Bassman and do this to it..
Up the voltage
double the plate filtering and keep the rectifier
Use Orange drops
Rip out the old boards and put in all PCB
use EL34's on an amp modded to be clean
No doubt he was going for clean headroom..I would think there are better ways to go about..Just me I guess
Tony
" The psychics on my bench is the same as Dumble'"
talbany wrote:I am totally stumped as to why someone would take an Old classic great sounding circuit such as the Bassman and do this to it..
Up the voltage
double the plate filtering and keep the rectifier
Use Orange drops
Rip out the old boards and put in all PCB
use EL34's on an amp modded to be clean
No doubt he was going for clean headroom..I would think there are better ways to go about..Just me I guess
I'm sure there are better ways to go about adding more clean headroom. but if it sounds good go with it.
I wonder what HAD did when he put the Ultraphonic mod in a Fender classic amp? Anyone know?
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