Layout 18 watt classic

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Bieworm
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Layout 18 watt classic

Post by Bieworm »

Hey

Since my TMB tremolo is finished I notice some difference in noise compared to my first build, the 18W classic. I am going to re-do the classic in the spirit of the way the TMB tremolo is wired and laid out. So I took the ceriatone layout and redrew the layout according to what I've learned.
I moved the PI from V2 to V3 and tremolo preamp from V3 to V2. This makes more sense like this anyway. There are a lot less wires crossing this way.
Going to put new components on the board. New tube sockets from Belton. New wiring all over.
Is this layout ok? Should I move the ground die the PI to the star ground too? Or is it ok at the preamp ground bus ?
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Re: Layout 18 watt classic

Post by JMPGuitars »

That's no good. The preamp ground bus should not go to the star ground. The 16μF filter cap should go to the preamp bus, not the power amp bus. That same filter cap should also be placed near the preamp cathode caps.

Read the Modern Ground Schemes thread, and follow the philosophy of my linked layout: viewtopic.php?f=4&t=25372

If you can be patient, I will eventually draw a classic layout also.

Thanks,
Josh
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Re: Layout 18 watt classic

Post by Bieworm »

JMPGuitars wrote:
Fri 04/24/20 7:06 am
That's no good. The preamp ground bus should not go to the star ground. The 16μF filter cap should go to the preamp bus, not the power amp bus. That same filter cap should also be placed near the preamp cathode caps.

Read the Modern Ground Schemes thread, and follow the philosophy of my linked layout: viewtopic.php?f=4&t=25372

If you can be patient, I will eventually draw a classic layout also.

Thanks,
Josh
I plan on connecting the preamp ground bus to the ground lug near the trem channel input.
My question was of I should connect the groundwire coming from the junction of both 470k resistors from the PI to the ground bus or to the star ground near the power transformer. If you look closer to my drawing you see the ground busses are separated between preamp and power amp sections.
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Re: Layout 18 watt classic

Post by JMPGuitars »

Bieworm wrote:
Fri 04/24/20 7:31 am
I plan on connecting the preamp ground bus to the ground lug near the trem channel input.
My question was of I should connect the groundwire coming from the junction of both 470k resistors from the PI to the ground bus or to the star ground near the power transformer. If you look closer to my drawing you see the ground busses are separated between preamp and power amp sections.
In your drawing that you made, you have a 16μF electrolytic capacitor connected to the power amp ground. That is bad. It needs to be moved, and connected to the preamp bus.

The 470K pair going to ground can be connected to the power amp bus.
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Re: Layout 18 watt classic

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JMPGuitars wrote:
Fri 04/24/20 7:36 am
Bieworm wrote:
Fri 04/24/20 7:31 am
I plan on connecting the preamp ground bus to the ground lug near the trem channel input.
My question was of I should connect the groundwire coming from the junction of both 470k resistors from the PI to the ground bus or to the star ground near the power transformer. If you look closer to my drawing you see the ground busses are separated between preamp and power amp sections.
In your drawing that you made, you have a 16μF electrolytic capacitor connected to the power amp ground. That is bad. It needs to be moved, and connected to the preamp bus.

The 470K pair going to ground can be connected to the power amp bus.
Ok. My bad
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Re: Layout 18 watt classic

Post by JMPGuitars »

I did start doing the docs. I might have them done over the weekend. We'll see. ;)
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Re: Layout 18 watt classic

Post by Bieworm »

Josh, are you familiar with the eminence ax75 ? Do you have an objective opinion?
It's confusing because as usual reviews are always black and white. My impression is that it's a darker sounding speaker...which I like. But is it bland and characterless?
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Re: Layout 18 watt classic

Post by zaphod_phil »

JMPGuitars wrote:
Fri 04/24/20 7:36 am
Bieworm wrote:
Fri 04/24/20 7:31 am
I plan on connecting the preamp ground bus to the ground lug near the trem channel input.
My question was of I should connect the groundwire coming from the junction of both 470k resistors from the PI to the ground bus or to the star ground near the power transformer. If you look closer to my drawing you see the ground busses are separated between preamp and power amp sections.
In your drawing that you made, you have a 16μF electrolytic capacitor connected to the power amp ground. That is bad. It needs to be moved, and connected to the preamp buss.

The 470K pair going to ground can be connected to the power amp buss.
Assuming we’re actually talking of the power tubes' grid resistors here, and not the PI 12AX7's grid resistors. Those should go to the Preamp&PI ground buss.
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Re: Layout 18 watt classic

Post by JMPGuitars »

Bieworm wrote:
Fri 04/24/20 4:01 pm
Josh, are you familiar with the eminence ax75 ? Do you have an objective opinion?
It's confusing because as usual reviews are always black and white. My impression is that it's a darker sounding speaker...which I like. But is it bland and characterless?
I've never used it. But I wouldn't use a 75 watt speaker if I could avoid it. I max out at 50 watt speakers for these amps.

BTW- the docs are done. I have to review and test them before I post them.

zaphod_phil wrote:
Fri 04/24/20 4:57 pm
Assuming we’re actually talking of the power tubes' grid resistors here, and not the PI 12AX7's grid resistors. Those should go to the Preamp&PI ground buss.
Correct, we're talking about the power tube grid reference resistors. At least I am. ;)

Thanks,
Josh
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Re: Layout 18 watt classic

Post by Bieworm »

zaphod_phil wrote:
Fri 04/24/20 4:57 pm
JMPGuitars wrote:
Fri 04/24/20 7:36 am
Bieworm wrote:
Fri 04/24/20 7:31 am
I plan on connecting the preamp ground bus to the ground lug near the trem channel input.
My question was of I should connect the groundwire coming from the junction of both 470k resistors from the PI to the ground bus or to the star ground near the power transformer. If you look closer to my drawing you see the ground busses are separated between preamp and power amp sections.
In your drawing that you made, you have a 16μF electrolytic capacitor connected to the power amp ground. That is bad. It needs to be moved, and connected to the preamp buss.

The 470K pair going to ground can be connected to the power amp buss.
Assuming we’re actually talking of the power tubes' grid resistors here, and not the PI 12AX7's grid resistors. Those should go to the Preamp&PI ground buss.
Indeed. The power tube grid resistors.
But they can also be connected to the preamp ground bus? Ceriatone does...
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Re: Layout 18 watt classic

Post by crgfrench »

Yes the power tube grid leaks should ground at the preamp bus rather than the poweramp bus.

The only components attached to the power amp bus are the first 2 filter caps, power tube cathode cap & resistor, and the HV center tap from the PT.

The PI grid leak resistors also connect to the preamp bus, via the tail resistor.
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Re: Layout 18 watt classic

Post by JMPGuitars »

Bieworm wrote:
Sat 04/25/20 2:31 am
Indeed. The power tube grid resistors.
But they can also be connected to the preamp ground bus? Ceriatone does...
They can be connected to either bus. That's basically the exception that's less important than most grounds. To me it makes more sense to the power bus, but it can go either way.

EDIT: I've posted 3 new versions of the classic, if you're feeling brave. ;)
viewtopic.php?f=25&t=25606

Thanks,
Josh
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Re: Layout 18 watt classic

Post by crgfrench »

buss
noun
\ ˈbəs \
Definition of buss:
kiss

bus
noun
\ ˈbəs \
Definition of bus:
1: a large motor vehicle designed to carry passengers
2: a small hand truck
3: a conductor or an assembly of conductors for collecting and distributing electric currents
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Re: Layout 18 watt classic

Post by Bieworm »

crgfrench wrote:
Sat 04/25/20 9:20 am
buss
noun
\ ˈbəs \
Definition of buss:
kiss

bus
noun
\ ˈbəs \
Definition of bus:
1: a large motor vehicle designed to carry passengers
2: a small hand truck
3: a conductor or an assembly of conductors for collecting and distributing electric currents
Ah... tomaitow, tomaahtow... ;)
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Re: Layout 18 watt classic

Post by Bieworm »

JMPGuitars wrote:
Sat 04/25/20 6:34 am
Bieworm wrote:
Sat 04/25/20 2:31 am
Indeed. The power tube grid resistors.
But they can also be connected to the preamp ground bus? Ceriatone does...
They can be connected to either bus. That's basically the exception that's less important than most grounds. To me it makes more sense to the power bus, but it can go either way.

EDIT: I've posted 3 new versions of the classic, if you're feeling brave. ;)
viewtopic.php?f=25&t=25606

Thanks,
Josh
Wow!!! Very clear!!!
Now I can ditch the normal channel and make room for reverb :P
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