18 Watt Mazerati GT?

[benoit]

For those familiar with this amp, would it work to build this with 2xel84 instead of 4, and if so, what would need to change besides simply substituting one power section for another? Obviously its not going to sound exactly the same but It'd be cool to maintain as much character as possible.

[Phil_S]

Don't know this particular amp, but assuming 4 x EL84 show a plate load of 4K, then 2 x EL84 will show a plate load of 8K to the output transformer. This means your secondary taps are also doubled, so your 4 ohm speaker tap is now 8 ohms, etc. If it has a 16 ohm tap, that becomes a useless 32 ohm tap unless you've got a 2x cab with a pair of 16 ohm drivers, which you could rewire from parallel to series to make it 32 ohms. I think this gives you the picture.

You might consider a different output transformer. You might also consider a power transformer with a lower VA rating, as you can probably cut 100mA off the B+ circuit requirement when you omit two tubes. This might save you a few dollars. Once you start changing the iron, you run the risk of changing the tone.

[benoit]

Don't know this particular amp, but assuming 4 x EL84 show a plate load of 4K, then 2 x EL84 will show a plate load of 8K to the output transformer. This means your secondary taps are also doubled, so your 4 ohm speaker tap is now 8 ohms, etc. If it has a 16 ohm tap, that becomes a useless 32 ohm tap unless you've got a 2x cab with a pair of 16 ohm drivers, which you could rewire from parallel to series to make it 32 ohms. I think this gives you the picture.

You might consider a different output transformer. You might also consider a power transformer with a lower VA rating, as you can probably cut 100mA off the B+ circuit requirement when you omit two tubes. This might save you a few dollars. Once you start changing the iron, you run the risk of changing the tone.

Thatnks for the input. The PT/OT I was thinking of using is actually a PT I pulled from and organ amp that was running a pair of el84s and 4 or 5 12ax7s, plus a rectifier I can't remember at the moment. I was originally thinking I'd build a carmen ghia, and I guess I still could.

[paisley_tele]

do you ahev the layout for this amp

[Phil_S]

The PT/OT I was thinking of using is actually a PT I pulled from and organ amp that was running a pair of el84s and 4 or 5 12ax7s, plus a rectifier I can't remember at the moment. I was originally thinking I'd build a carmen ghia, and I guess I still could.

Whether it's right for the particular design, I can't say, but it seems totally appropriate for the tube compliment.

[paisley_tele]

could some one make that into a layout.

[M Fowler]

MAZ 18 Jr.: 1-GT12AX7S, 1-GT12AX7S, 1-GT12AT7 C, 1-GT 12AX7R1, 1-GT12AX7R2, 1 Pair GT EL-84-S, 1-5AR4.


Mazerati: 1-GT 12AX7S, 1-5751, 1-Quad GT EL-84-S, 1-5AR4

See the attached schematic and gut shot

Mark

[jimistheman]

I thought the Maz GT ran two 12AX7's--the diagram seems to indicate three. Is it too early and am I cross eyed?

Thanks!

[benoit]

You're lookin at the labels instead of the schematic, I think. It does say "12ax7" 3 times, but really the first two gain stages are one tube and the PI is one tube, two total.

[jimistheman]

Thank you sir!

[invalidcd]

Hello , Im the who made that schematic I notice that i forgot to label the second cathode resistor, its a 2k7 but anyway i have built this and it is an amazing amp , it has quit a lot of gain so you will have to use your guitars volume knob to achieve a clean tone. this is not one of his vox rip-offs and it
does not sound like the old mazerati so if you want the vox sound or a clean amp this is not it. but what i did was add an ef86 channel to mine and ran it parallel to the 12ax7 (so i could blend them) then added a relay switch to turn off the 12ax7 channel so the ef86 would be my clean channel. This set up worked very well and should work well in an 18watt set up with little changes. i hope this helps ,sorry im not very articulate when it comes to post comments.

[benoit]

Hello , Im the who made that schematic I notice that i forgot to label the second cathode resistor, its a 2k7 but anyway i have built this and it is an amazing amp , it has quit a lot of gain so you will have to use your guitars volume knob to achieve a clean tone. this is not one of his vox rip-offs and it
does not sound like the old mazerati so if you want the vox sound or a clean amp this is not it. but what i did was add an ef86 channel to mine and ran it parallel to the 12ax7 (so i could blend them) then added a relay switch to turn off the 12ax7 channel so the ef86 would be my clean channel. This set up worked very well and should work well in an 18watt set up with little changes. i hope this helps ,sorry im not very articulate when it comes to post comments.

No, that's cool, that info helps. What kind of plate voltages do you get in your amp?

[M Fowler]

invalidcd

Do you have more files or information on building this amp because I want to build one. Did you make your board or where did you get one and BOM on this. I could just go through the schematic but if you have that would be cool.

Mark

[rhinson]

this amp is essentially a single ch komet constellation (different parts values in the pre of course)----and that is essentially a tweaked tweed champ pre run into an ac30 power section. rh