New amp project... 18 watt marshall clone

[toejam]

Re: New amp project... 18 watt marshall clone

Pete, you could paint happy little trees, happy little clouds and pretty little mountains on your amps! [img]/images/graemlins/laugh.gif[/img]

[Twisteramps]

Re: New amp project... 18 watt marshall clone

Mine would be angry devils, angry red clouds and angrier black skeletons on an abysmal plain. [img]/images/graemlins/smile.gif[/img]

[toejam]

Re: New amp project... 18 watt marshall clone

There ya go! I'd buy one then, and so would Bill. [img]/images/graemlins/laugh.gif[/img]
Any interest in tackling that mini Marshall head I've got?

[Twisteramps]

Re: New amp project... 18 watt marshall clone

Still thinkin' about it Joe. I have an idea of what circuit/layout would fit in there, just have to see how big the transformers/etc would be.

Pete

[toejam]

Re: New amp project... 18 watt marshall clone

Okay, cool. I was thinking maybe a two-channel deal (footswitchable?), keep the Gain 1 for clean, Gain 2 for high gain distortion (think Slayer), let them share the same bass, middle and treble eq controls, keep the master volume and reverb, maybe turn the headphone, line out and cd input jacks into an effects loop send, return and level control. I was thinking EL84s or something that would be cool for low playing levels as well as louder jamming levels, soundwise like a cross between a Marshall and Mesa.

[rstites]

Re: New amp project... 18 watt marshall clone

Pete,

I'd thought about going the shielded cable route. Infact, I'd wondered if this would be pretty much mandatory with high gain preamps or can that be managed without the shielding? I definitely have some wires crossing each other the way it's laid out, but I'll have to check when I'm home whether it's the main signal wire. I tried not to do that, but you know how it is before you really learn to lay these things out properly. I may also have issues with exposed lead length on some caps and resistors going to/from the tone controls. I should probably use wires for those rather than suspending the comment between the terminal strip and the pot. Anyhow, I need to work through this some before I start building the next amp. I do have my schematic done and will start sourcing parts by the end of the month.

I think for most parts I can do a bulk order through Mouser and another through Antique Electronics (whose prices on many items now is better than Mouser), but neither carrys the boards so I'll google your source when I get back to civilization. (56k connections suck fyi! [img]/images/graemlins/smile.gif[/img] ) Interestingly Mouser does carry the standoffs/turrets and sells them in bulk...

The only other thing is transformers and I'm thinking about trying the Heyboers (sp?) from GDS. I just need to get ahold of the data sheets on them and look them over. I'll probably run a ss rectifier and am probably going to run fixed bias in the power amp...still thinking on those two right now.

Ross

[Twisteramps]

Re: New amp project... 18 watt marshall clone

I look at it like this regarding shielded cable - it's not that much harder to do, and it makes the amp quieter. What's not to love? [img]/images/graemlins/smile.gif[/img]

I never had that many problems with the tone control leads... Just anything that goes to pin 2 or 7 on your preamp tubes, shield em! Boogie put caps to bleed off treble here and there in their old amps instead of using shielded cable... I've always wondered what would happen if you found say a Mark I boogie and properly shielded it and got rid of the 'band-aid' capacitors. [img]/images/graemlins/smile.gif[/img]

If you run a SS rectifier, you'll need a way to throw away quite a few volts... You may want to get the heyboer output, and get a hammond power transformer that's the proper voltage once you've rectified it. a 290-0-290 transformer will put out roughly 406v with solid state, and 327v with a 5Y3GT. I don't know what the voltage loss is with the EZ81 rectifier tube, which is what all the 18 watts have... but I'm sure it's as bad or worse than the 5Y3GT. This is why I like building amps with octal rectifiers when I have room - you can swap out the rectifiers and change the voltage easily. It's like a variac that's safe!

Pete

[horns666]

Re: New amp project... 18 watt marshall clone

Pete...how much..I want YOU to make my amp...that 450 wt all 6550 or KT88 or 5881 powersection and , ..and a 17 tube 12AX7 preamp gain stage...it could be done...and you can do this..and with a glory hole just for "GP"..

and all a box with razor wire and spikes...that would be purdy!

I have money...I will give to you..

will you take my measily Uber as down payment..

and only one channel...not two...that will just confuse me.. [img]/images/graemlins/laugh.gif[/img]

and instead of calling it the Bill Z Bub model can you call it someting cooler like the "F - U - N - Z - A model or somethin'..why beat around my bush.. [img]/images/graemlins/laugh.gif[/img]

I need this!

we aLL need that!

so what if it cost over 1000 dolars to re-tube...it's worth it! [img]/images/graemlins/grin.gif[/img]

[Twisteramps]

Re: New amp project... 18 watt marshall clone

Bill, I'll build you an amp that uses 6L6s for PREAMP tubes! It will breathe fire and piss gasoline!

[Deneb]

Re: New amp project... 18 watt marshall clone

Pete, you better be building 2 of those [img]/images/graemlins/smile.gif[/img]

Seriously, in your work, do you like carbon resistors, or Metal film? I've read that metal film are quieter than carbon, but on my work on wah pedals, it doesn't seem to make a difference (at least that I can hear).

[horns666]

Re: New amp project... 18 watt marshall clone


"Bill, I'll build you an amp that uses 6L6s for PREAMP tubes! It will breathe fire and piss gasoline"



[img]/images/graemlins/eek.gif[/img] [img]/images/graemlins/eek.gif[/img] [img]/images/graemlins/eek.gif[/img] [img]/images/graemlins/eek.gif[/img] [img]/images/graemlins/eek.gif[/img] [img]/images/graemlins/eek.gif[/img] [img]/images/graemlins/eek.gif[/img]

DO Dat Chit!!!!! [img]/images/graemlins/laugh.gif[/img] [img]/images/graemlins/toast.gif[/img]

[Twisteramps]

Re: New amp project... 18 watt marshall clone

[ QUOTE ]
Pete, you better be building 2 of those [img]/images/graemlins/smile.gif[/img]

Seriously, in your work, do you like carbon resistors, or Metal film? I've read that metal film are quieter than carbon, but on my work on wah pedals, it doesn't seem to make a difference (at least that I can hear).

[/ QUOTE ]

metal film. less noise and they don't change resistance when they get hot like carbon comps will.

Pete

[Infernal Death]

Re: New amp project... 18 watt marshall clone

[ QUOTE ]
that 450 wt all 6550 or KT88 or 5881 powersection and , ..and a 17 tube 12AX7 preamp gain stage...

[/ QUOTE ]

Bill what you need is an amp with this tube:

http://www.cpii.com/eimac/catalog/169218.htm

With a max plate voltage of 22500 volts and 125A it's no wonder it puts out some wattage [img]/images/graemlins/grin.gif[/img]

Man this would be a cool amplifier. The whole city will know when you play guitar as none other will have any power once you switched your beast on [img]/images/graemlins/headbang.gif[/img]

Flo

[Deneb]

Re: New amp project... 18 watt marshall clone

8974/X-2159
The 8974 is a power tetrode designed for very high powered frequency or high frequency broadcast service and very low frequency communication in the megawatt power range. The 8974 has a two section thoriated tungsten filament mounted on water-cooled supports. The two sections may be fed in quadrature to reduce hum contributed by an arc ac power source. The maximum anode dissipation rating is 1500 kW steady state. Large diameter coaxial terminals are used for the control grid and the RF filament terminals. Filament power and filament support cooling water connections are made through three special couplings with threaded clamping rings.



--------------------------------------------------------------------------------

Characteristics
Plate Dissipation (Max.) 1,500,000 Watts
Screen Dissipation (Max.) 15,000 Watts
Grid Dissipation (Max.) 4,000 Watts
Frequency for Max. rating (CW) 30 MHz
Amplification Factor 4.5
Filament/Cathode Thoriated Tungsten
Voltage
Current 16.3 Volts
600 Amps
Capacitance Grounded Cathode
Input
Output
Feedthrough 1600 pf
250 pf
6 pf
Capacitance Grounded Grid
Input
Output
Feedthrough 675 pf
260 pf
1.0 pf
Cooling Water and Forced Air
Base Special Coaxial
Air Socket ---
Air Chimney ---
Boiler ---
Length 23.75 in; 60.30 cm
Diameter 17.03 in; 43.30 cm
Weight 175.0 lb; 80.0 kg

[Deneb]

Re: New amp project... 18 watt marshall clone

If one of those tubes weighs 175 pounds, just imagine what the amp would weigh...then the power supply for it! Jesus, then your roadies WOULD have something to bitch about.