New 2550X build (will be 2555X) + soundclip + highgainclip

[jcmjmp]

Unplug the B+ AC supply between the PT and the board and measure the AC RMS voltage right at the PT. What is the reading?

Theoretically, your absolute maximum DC voltage cannot exceed the AC RMS value x 1.414. After that, you have to take into consideration the number of filter caps, their values and current draw to get the estimated DC value.

If the voltage is too high at the PT, you could add a couple of extra diodes to bring the voltage down. With zeners, you could bring the voltage down by pretty much any value.

[mat]

Thanks jcmjmp for the advice. I got another advice to use the 240V tap instead of the 220 tap and that lowered the voltages on plates to 450V.

After I get the bug (od gain pot seems to do almost nothing) on od-side of the amp sorted I'll try to make a clip of the amp.

Thanks, Mat

[mat]

The build is ready. I like the sound very much but the mid pot works on higher mid range than I expected. I would like it to operate on a lower frequency. Would this be as simple as to change the value of the cap on the mid pot middle lug ?

Link for the schem: http://home.comcast.net/~mamp17/Jubilee%20Layouts.html

Thanks,
Mat

[Structo]

If you want to shift the whole spectrum that the tone stack operates you can change the value of the 100K slope resistor.

To change just the mids you can go to a bigger mid pot (250K) or change the value of the .01uf mid cap.

[mat]

If you want to shift the whole spectrum that the tone stack operates you can change the value of the 100K slope resistor.

To change just the mids you can go to a bigger mid pot (250K) or change the value of the .01uf mid cap.

Thanks Tom for the answer.

The bass pot seems to be in a good range. The treble is almost at zero all the time.

I'll try smaller value cap for the mid-pots .01.

I would also like to add a mid-boost for the amp. Maybe something like on the Dumbles...

Mat

[Structo]

The mid boost is real easy to implement.

You add a small cap in series to a treble cap with and a resistor to reference to ground.
A switch or relay is used to either jump the cap or allow it into the circuit.

This is how the Dumble ODS does it.

In the example below the .002uf cap is the treble cap and the 390pf cap is the one added in series to the .002uf cap when the switch is open. When the switch is closed the 390pf is bypassed. (mid boost)
The 4.7M resistor is the ground reference for the boost.

[mat]

I tried a 3n3 on place of the 10n going to middle lug of the mid pot. On od-side it was an improvement but when in clean side it was too muddy.

I'm not quite sure how to put the dumble-style mid boost in 2555, but what I did I got rid of the clean/crunch option (didnt like that at all) and used the switch to bypass the 220p cap going to treble pot.
Really nice option ! A slight volume + mid boost clearing the sound in a very nice way !

Mat

[mat]

I finished the amp and I like it a lot ! The first Marshall style amp I have. I did a soundclip (horribly long-5 and half minutes of noodling ) Sound chain is Gibson ES-339 to amp + Spring King on the loop. Recorded with old Zoom hand held recorder. http://soundclick.com/share?songid=8300020

The amp couldnt be further of the really cool builds I have seen on these pages. I went with a smaller chassis and used metal film resistor trough the build. I used the head box I built for my Trainwreck build. Never liked the Express enough to keep it.

Cell phone picture attached.

Big thanks for everyone who helped me on this one

Cheers, Mat

[Structo]

Sounds great!
Did you put a relay for the OD or are you just using the front panel switches?

Cool looking cab, is it maple?

[mat]

Sounds great!
Did you put a relay for the OD or are you just using the front panel switches?

Cool looking cab, is it maple?

Thanks Tom, yes there is a 5V relay for the OD. The cab is Finnish birch.

Mat

[RagnarMarGunn]

Mat,

Sounds great, can't wait to start my 2550X, part are on the way.

[mat]

Mat,

Sounds great, can't wait to start my 2550X, part are on the way.

Thanks Ragnar ! Are You building the Ceriatone one ?

Btw. anyone know what kind of mid boost is on Category 5 JB-100 model ?

Mat

[mat]

btw. the cab was a diy 2x12 with 2555 driving a single Eminince Delta Pro 12A speaker.

Mat

[RagnarMarGunn]

Mat,

Sounds great, can't wait to start my 2550X, part are on the way.

Thanks Ragnar ! Are You building the Ceriatone one ?

Btw. anyone know what kind of mid boost is on Category 5 JB-100 model ?

Mat

No, no Ceriatione for me, ground up custom. I'm building SDM TL2550X. Most parts from Metro. I'm gutting a Marshall 5210 transistor 1X12 combo and replacing all of the parts and doing some mods, extra tube, dual PPIMV etc. I wold love to hear another clip with some more gain

[mat]

[quote="RagnarMarGunn
No, no Ceriatione for me, ground up custom. I'm building SDM TL2550X. Most parts from Metro. I'm gutting a Marshall 5210 transistor 1X12 combo and replacing all of the parts and doing some mods, extra tube, dual PPIMV etc. I wold love to hear another clip with some more gain [/quote]

Ok, SDM's layouts are very nice and easy to follow. Good luck for the build, would like very much to hear it when it is ready.

Btw. what trannies are You going to use ? Metro ? MM ?

I'll record another clip with the gain full when I find time to go to the reherseals place of ours (busy at work right now.)

Anyone know of the midboost of the Category 5 JB100 ?

Mat