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Old 2nd August 2004, 11:14 PM   #1
zix is offline zix  Sweden
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Default physical layout of 6B4G PP amp?

I am trying to figure out a good physical layout of a PP amp (it is the Ralph Powers´design but with ECC99 at the input like Stigla did some time ago).
Ever since trying to make a valve preamp work (and failing miserably concerning hum + noise levels) I have been feeling very humble about the actual building part of the DIY valve amp game. Or perhaps "nervous and disillusioned" covers my feelings better
However, I recently bought Morgan Jones new title "Building valve amps" and that made a lot of things clear and also brought my courage up a bit. It can´t be impossible, can it? Anyway, to cut the crap, I have two suggestions here for physical layout of those big things (transformers, valves and stabilizers) and would very much appreciate comments on these alternatives.
Alternative 1 is "everything on one chassis". Alternative 2 is separate chassis for signal and power supply. Both are for one channel only but I am open to suggestions for stereo layouts too.

Did I get the orientation of the transformers right? Or should I rotate some of them? (arrow is the axis of the core, thus windings are at right angles to the arrows)

The placement of the parts, are those OK or have I got things wrong? I am a bit worried about the power supply choke inducing hum in sensitive parts. And the OC3/VR105:s, if they belong on the power supply chassis/half or as I have put them, near the IT transformer?

Many questions, I know. The circuit I am going to try to build is this one. Any good hands-on or knowledgeable or encouraging tips are welcome!
/Mats
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Old 2nd August 2004, 11:27 PM   #2
G is offline G  United States
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I can suggest a few things Zix. Firstly you want to keep the regulator tubes away from your signal tube. You also want to have the laminations of your choke perpendicular to the laminations of your power transformer. Try to put the output transformer on one end of the chassis and the power supply on the other. The regulator tubes are part of the power supply so keep them close to it. I hope that helps. You have certainly picked a difficult circuit for a first project. I hope it turns out well.
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Old 3rd August 2004, 09:43 AM   #3
zix is offline zix  Sweden
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Thanks a lot, G!
Having another try at it, I came up with this suggestion. It is only approximate, like the first suggestions, in sizes or distances between parts, one or two chassis and so on.

OC3/VR105 is now moved to the power supply half and the orientation of the choke and other transformers is changed. Also, I moved the rectifiers in front of the choke, which would mean a little longer cable runs from the mains transformer to the rectifiers, but shorter runs from the capacitor bank (I thought to put them underneath) to output valves, and the OC3:s are still in the vicinity of the IT (since they are regulating HT for the input ECC99 I thought this might be good). Plus it looks a little better now...
What say you good people? Better or just different? Other tips?
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Old 3rd August 2004, 09:52 AM   #4
dhaen is offline dhaen  Europe
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It's the interstage (driver) transformers that will be most susceptible to picking up hum. Locate these with even more caution than the output transformers.
Also it's desirable, but not essential that the choke laminations are perpedicular to the mains transformer and the signal transformers; - yes, it's possible, we live in a 3 dimentional world (AFAIK)
You might like to post a sketch of your layout before you start drilling. There may be slightly differing advice from various members, but it'll give you a "feel" for right and wrong, so you can make an informed decision.
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Old 3rd August 2004, 10:04 AM   #5
dhaen is offline dhaen  Europe
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I just noticed the standby switch. You'll need something better than a mains switch if you want it to last any time. Alternatively, fit a "quench" circuit across the contacts; something like 100n 630v in series with 100 ohm 2w.
Otherwise, I quite like the circuit
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Old 3rd August 2004, 10:25 AM   #6
morfeas is offline morfeas  Greece
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Your last layout looks fine.

Build a good star ground on each chassis, avoid ground loops and it will be quiet as dead.

Enjoy
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Old 3rd August 2004, 10:50 AM   #7
G is offline G  United States
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Quote:
Originally posted by zix
Thanks a lot, G!
Having another try at it, I came up with this suggestion. It is only approximate, like the first suggestions, in sizes or distances between parts, one or two chassis and so on.

OC3/VR105 is now moved to the power supply half and the orientation of the choke and other transformers is changed. Also, I moved the rectifiers in front of the choke, which would mean a little longer cable runs from the mains transformer to the rectifiers, but shorter runs from the capacitor bank (I thought to put them underneath) to output valves, and the OC3:s are still in the vicinity of the IT (since they are regulating HT for the input ECC99 I thought this might be good). Plus it looks a little better now...
What say you good people? Better or just different? Other tips?
That looks good Zix. Let us know how it goes. Also look up some info on star grounding and signal wire routing for tube amps. Enjoy and be careful.
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Old 3rd August 2004, 07:38 PM   #8
bau is offline bau  United States
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Default Good looking

HELLO
After you done , can you let I know how is it sound .
I build one & used 6c45pi as an input last year
My amp have no bass
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Old 5th August 2004, 10:01 PM   #9
zix is offline zix  Sweden
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Quote:
That looks good Zix. Let us know how it goes. Also look up some info on star grounding and signal wire routing for tube amps. Enjoy and be careful.
Oh, good! Star grounding and hardwiring is what I had in mind, I will try not to make too big a mess out of it. Will probably be back here for more advice when that time comes

Quote:
just noticed the standby switch. You'll need something better than a mains switch if you want it to last any time. Alternatively, fit a "quench" circuit across the contacts; something like 100n 630v in series with 100 ohm 2w.
Otherwise, I quite like the circuit.

It's the interstage (driver) transformers that will be most susceptible to picking up hum. Locate these with even more caution than the output transformers.
Also it's desirable, but not essential that the choke laminations are perpedicular to the mains transformer and the signal transformers; - yes, it's possible, we live in a 3 dimentional world (AFAIK)
You might like to post a sketch of your layout before you start drilling. There may be slightly differing advice from various members, but it'll give you a "feel" for right and wrong, so you can make an informed decision.
Thanks, dhaen! I will try rotating the choke and the IT:s and OPT:s in many planes with an oscilloscope attached to them before soldering. As long as they don´t need a supporting subchassis directed along the fourth dimension axis I am game... well, more or less. Again, I will probably be back here (hopefully not in tears) in a couple of weeks with the first layout questions.

Quote:
Your last layout looks fine.
Build a good star ground on each chassis, avoid ground loops and it will be quiet as dead.
Aha, star ground on both chassis! Errr... You mean both power supply and signal chassis, or both left and right channel chassis?
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Old 7th August 2004, 12:04 AM   #10
zix is offline zix  Sweden
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Quote:
HELLO
After you done , can you let I know how is it sound .
I build one & used 6c45pi as an input last year
My amp have no bass
Sorry to hear about the lack of bass, bau. I have heard good things about the 6c45pi, but don´t have the designer capabilities needed to redesign Ralph Powers/Gary Dahls design, as Stigla could do - at least not yet. However, the ECC99 has good rep too, so I will follow Stiglas circuit.
I will of course let you, and anyone else that wants to, know how it sounds when, and if, I get it working.
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