New 20 watt SD build

[Gainzilla]

Aaaaaaaah, ok got it! I had only given your schem a quick look and missed that tiny detail. Lol

I'm looking for an excuse to build something in the JCM800 split channel donor amp I've got... Maybe I'll give that a go alongside a fender clean channel.

Thanks!

[fusionbear]

Here is the latest and final revision (I hope...LOL...)

V1b Cathode went from .1 to .047 to .22
V2a Cathode went from .47 to .33

PI Couplers went from .047 to .066

Also, in the first schematic, I forgot to draw the 100pf across the input jack.

Thanks!

[IMG790]http://i169.photobucket.com/albums/u223/fusionbear/Super%20Drive%2020%20Build/CCI12132015_zpstoajiyiq.jpg[/img]

[caps8419]

thanks for the update Carl.

Do you think a 272DX PT would work well in this build? slightly off from the ceriatone PT you used but close...

How much current do you think the choke needs to be able to handle as built?
should 150ma be sufficient?

Also do you have your last schematic revision available as a PDF?

Thanks!

Michael

[fusionbear]

Pdf as requested....

When I have some extra time, I will make the sch. doc.

[10thTx]

When I have some extra time, I will make the sch. doc.

FusionBear,

ONCE you repost a correct GIF version, I will edit this post and remove the schematic so there is not confusion.

Schematic edited & posted by FusionBear

With respect, 10thtx

[10thTx]

FusionBear,

Some things to check on the schematic that I am unsure of:

1) cathode resistor on FX return is 470R? I would think it would have been
a higher value such as 1.5k ?

2) please review the bias to see if it is drawn correctly?

3) the presence set up doesn't look right to me, but maybe it is?
I am used to seeing a resistor going to the OT rather then the .001 cap

There may be other errors so consider this a DRAFT version.

With respect, 10thtx

[caps8419]

Pdf as requested....

When I have some extra time, I will make the sch. doc.

thanks Carl!

[fusionbear]

thanks for the update Carl.

Do you think a 272DX PT would work well in this build? slightly off from the ceriatone PT you used but close...

How much current do you think the choke needs to be able to handle as built?
should 150ma be sufficient?

Also do you have your last schematic revision available as a PDF?

Thanks!

Michael

Yes, the 272DX is well within specs,

[fusionbear]

FusionBear,

Some things to check on the schematic that I am unsure of:

1) cathode resistor on FX return is 470R? I would think it would have been
a higher value such as 1.5k ?

2) please review the bias to see if it is drawn correctly?

3) the presence set up doesn't look right to me, but maybe it is?
I am used to seeing a resistor going to the OT rather then the .001 cap

There may be other errors so consider this a DRAFT version.

With respect, 10thtx

Yes, you have correctly identified the circuit.

1) I have the 12AT7 in parallel so the 470 is correct. I am going to experiment and make in just a single triode tomorrow. Merlin shows a 1K on the Cathode and I will use a 100k on the plate. If that works better, I will let you know.
2) I will review tomorrow as I will have some time.
3) Yes, that is the SD Presence circuit. It is definitely different than we are all used to.... LOL... But it works in this amp.

[fusionbear]

Sometimes simple is better. I converted the loop to a single triode on the 12AT7 with a 1k/20uf on the cathode and 100K on the plate and it sounds much better!

But, don't kill me guys, I converted the amp to a 2204.... Ah, fickleness...LOL...

[IMG768]http://i169.photobucket.com/albums/u223/fusionbear/20%20Watt%202204%20Build/IMG_0651_zpssyhlfak1.jpg[/img]

The Super Drive circuit sounds awesome, but I feel it is a one trick pony and it doesn't take pedals well. It is a great one trick, but in the end, I prefer the versatility of the standard 2204 preamp... It takes fuzz, Octavia, vibe clones, and wah much better IMO...

[dorrisant]

Are the modulation effects better in the loop than dirt boxes etc.? Nothing good when you front-end them?

Thanks for the insight! ...and again, great looking build as usual.

[Structo]

Good looking amp Carl.

Do you ever get RFI when using a lower value (10K) on the V1a grid?

[fusionbear]

Are the modulation effects better in the loop than dirt boxes etc.? Nothing good when you front-end them?

Thanks for the insight! ...and again, great looking build as usual.

Effects in the loop are no issue. But the SD does not take pedals in front very well IMO. The 2204 takes just about anything in front...

[fusionbear]

Good looking amp Carl.

Do you ever get RFI when using a lower value (10K) on the V1a grid?

No sir, plus the 100pf on the input jack helps too.

I left the 10k in the 2204 conversion. No issues. If they come up, it is real easy to increase the resistor to 33k or even 68k.

[fusionbear]

Even though I converted the amp to 2204 specs, I edited the schematic. It is the final version. The SD circuit is a awesome sounding amp in its own right, but in the end, I prefer the classic 2203/2204 preamp in a 20 watt 2-6V6 power section package.

I want to particularly thank 10thTX for starting the draft and saving me a ton of time. Really! Thanks!