New 80 Watt Wreck done!

[drhulsey]

...Remember we have a lot of talent here...

100+ on the talent
So most of your tweakin' was done on paper and in your head
I never cease to be amazed

[Zippy]

I don't know if anyone might want to try this,but i'll suggest it anyway. And give an explanation about it.
I built a somewhat express amp about 4 years ago, using a blackface dual showman... I first used the express value resistors between the stages in the power section. The amp sounded great. But just for the heck of it, i switched it back to the standard fender values of the power section for this amp.

Now i know this amp used the blue caps, and CC resistors,fender trannys and a choke,and things like that, that are really not exactly parts a wreck used.
But even using those, not changing them..and just changing the values of resistors between the power stages..you could hear the difference.

Sounds like you might have been closer to the correct VOLTAGES with the Fender resistor values than you were using Express resistor values with the Fender iron.

Hmmm, imagine that. You came up with a great sounding amp even if you failed to use the right color parts.

Thanks, Richie, for sharing that. I don't suppose you measured and recorded your dropping string voltages with each setup?

[sst4270]

Allyn,

I have a tiny bit of spare time this week and so I'm doing a detailed layout of this amp. Presuming you don't mind, of course.
I should have it posted in a couple of days.
Obviously it'll have a few blanks, but maybe you'd be able to fill those in once a layout is up. It'll be done in the style of Asteroid/K60 layout that was previously posted. I noticed you followed a lot of those building techniques (i.e. grounding scheme) versus original Express.

Anyways that's it.

Regards,

Steve

[Richie]

Hmmm, imagine that. You came up with a great sounding amp even if you failed to use the right color parts.

Thanks, Richie, for sharing that. I don't suppose you measured and recorded your dropping string voltages with each setup

yes thats true .. sometimes you never know how something will turn out till you try.

I did take measurements, but thats been a long while back, i'll have to see if i can dig them up. The preamp voltage seemed to be just a bit higher,but nothing way different.. more along the lines of what the fender ran. But things like the 10k cathode will change things a bit compared to the fender..
But now the plate voltage on the power tubes and screens was a bit higher than what you would see in a wreck. Probably more like what you'd see in a concorde. Another reason it was very loud..

[Allynmey]

Allyn,

I have a tiny bit of spare time this week and so I'm doing a detailed layout of this amp. Presuming you don't mind, of course.
I should have it posted in a couple of days.
Obviously it'll have a few blanks, but maybe you'd be able to fill those in once a layout is up. It'll be done in the style of Asteroid/K60 layout that was previously posted. I noticed you followed a lot of those building techniques (i.e. grounding scheme) versus original Express.

Anyways that's it.

Regards,

Steve

No problem....didn't know there would be this much interest!

Most people complain they are too loud!

[rmb550]

What?? EH??? PARDON???? TOO WHAT???

[84k]

I always joke with Allyn and say the most brilliant thing KF ever did was be the first to make amps geared to the large lawyer/Orthodontist clientele!

They are in furniture cabinets that look like they should be on display not on stage, there is no back panel to protect the tubes for traveling to gigs and there is no handle!!! The other problem is I find is there is no where near enough volume from an express to play rock with a hard hitting drummer.

Allyn has delivered me the sound, volume, and other features that make his amp the 'Express for real situations.' He nailed it. Frighteningly so.

[sst4270]

Okay you guys asked (well, some of you anyways) so here it is.
I'm pretty sleepy now. Let me know if I made any mistakes.

... Like the speaker ground on the back of the chassis doesn't look right but I can't tell from the photos.

Steve

Edit:Revision 2-12-09**
Flipped Cathode bypass caps polarity
Corrected Resistor values/labels
Added parallel parts to power supply
Edited description of bias pot

Edit: Revision 2-13-09**
Corrected NFB to come from 4 ohm tap.

[Allynmey]

The 220K connected to the 25uF cap on V2 should be 2.7K the resistor next to it should be 10K like an Express. The PI snubber should be 50pF, don't forget the second 40uF under the board in parallel and the 1K/25W under the board in parallel. The entrance resistor in the bias is 180K not 220K, The bias pot is 20K 10 turns 3W. The bias resistor is 47K not 4.7K

Nice looking drawing though!

[tejastubes]

OH Yeah! Looks cool, although my opinion is that your first name should be on the amp. Allyn Amps,,,has a ring to it! Just like my express! I love it! Thank you!

Joshua

[paulster]

Nice looking drawing. First thing that really jumps out at me is the cathode caps for the preamps being round the wrong way.

This looks like it'll be a great fun amp.

Paul

[Allynmey]

Nice looking drawing. First thing that really jumps out at me is the cathode caps for the preamps being round the wrong way.

This looks like it'll be a great fun amp.

Paul

Good eyes...it was late. The bypass caps are the wrong polarity.

[gahult]

Also resistor on input jack needs to be labeled 1M.

Gary

[M Fowler]

I am liking this post more every day thanks for the great amp Allyn and sst4270 for working in the layout and 84k for wanting to drown out his drummer, kool.

Can't wait for the final layout on this so I can print it out and study. Also need to make my BOM. Allyn since you had the chassis custom made are you offering these?

Mark

[sst4270]

Thanks for the replies guys. I updated the layout based on all the input.
I have a couple of questions for Allyn:

Are the grounding nodes correct?
Are the speakers grounded to the correct spot? It looked like there was a grounding tab beside the cliff jacks, but no hardware was visible on the rear view. I suppose the screw head is underneath the rear faceplate?

Hopefully this'll be it... It would be nice to put the transformer specs on the page as well as the chassis dimensions. I took a guess at 20x9x2. Allyn, would you mind providing these?


Steve