2w Sub Miniature Express

[sst4270]

Dana,

Are you referring to this?

[UR12]

Yes that would be the one

[bancika]

This is very cool, congrats!
I'm in the middle of making a Mesa MarkIIC+ preamp with 6112 tubes and graphic EQ.
Cheers

[UR12]

This is very cool, congrats!
I'm in the middle of making a Mesa MarkIIC+ preamp with 6112 tubes and graphic EQ.
Cheers

Awesome!! let us know how it turns out

[wally19840]

Hi, where are you at with the new run of boards Dana?
Wally

[breakfastbuddy]

you guys make me confused , is it not so that the smaler you make this resistor , the less gain you get . so that 100k will give you less gain and more headroom ?
compared to the 150k

[UR12]

you guys make me confused , is it not so that the smaler you make this resistor , the less gain you get . so that 100k will give you less gain and more headroom ?
compared to the 150k

Yes that is exactly right. The original Express value was 150k. Unfortunatly this was a little much in the gain department for the smaller tubes and I changed it to a 47k to dump some of the signal level (LESS GAIN) and it cleaned up nicely. After going back and listening to the amp with both the 47k and the 100k I think I like the over the top barely controlable gain with the 100k. I am sure others may find a 47k, 68k or 82k as their favorite choice but you are not confused in your way of thinking.

Hi, where are you at with the new run of boards Dana?
Wally

It will be a while longer. I would guestimate about 4 weeks. I am set up to do a run of laser cut chassis on feb 2. New boards will be ordered to arrive sometime in late Feb. I have Tranny sets on order also that should arrive some time in a couple of weeks.

[moonrock]

I'd like to purchase one when available.
Bruce

[Richie]

wasn't there also a frequency chart for subbing different cap/resistor combination? So if you changed the resistor, you would also change the cap value? Although i have heard and played the little devil,and heard it again yesterday.. And it sounds very good as is.. I'm sure with the new tranny sets..and going from hammond..it will sound even better..

[Structo]

Maybe put a switch on the resistor so you can have either the 47k or 100k. Like a flavor switch.

[DHHZ]

Hi,
I'm thinking of building my own version of this, and I'm planning on using a cathodyne PI to keep if down to 2 tubes. Do you think that it would make a large difference to the sound? I know it would have slightly less gain, but that's OK with me.
By the way, yours looks fantastic!
Daniel

[kineteks]

I've tried a 100K resistor in the 3rd gain stage and it sounds great, a little muddy with my Les Paul, but absolutely the balls with Tele & fat Strat. I did a plug-in thing on the board and will be playing around with different values. I used a 64 pin DIP socket strip to make the resistor modules and the on-board socket. Included a shot of the hum-pot and heater dropping resistors, not pretty but I'll clean 'em up later.... The FET heat sink had the board-mount solder posts removed and the resulting holes tapped 4-40. It's screwed to the chassis right at the edge of the opening, pretty solid and the FET stays cool.

[UR12]

Hi,
I'm thinking of building my own version of this, and I'm planning on using a cathodyne PI to keep if down to 2 tubes. Do you think that it would make a large difference to the sound? I know it would have slightly less gain, but that's OK with me.
By the way, yours looks fantastic!
Daniel

That’s hard to say. The cathodyne will give you unity gain which translates to no gain at all. It would be interesting to try. I would guess that anyone else who has built a wreck style circuit using a cathodyne PI would have had the same results with a 12ax7 as you will with the 6111.

John
That looks cool as crap. If you think the 100k is a little much try a 82k.

On another note I took the day off from my regular job and ran a few chassis off for the Lil Devil. They are already pre punched with all of the holes. John supplied me with a Autocad file that he used on his chassis. I made a few changes for the new trannys spacing and added a few holes to mount the chassis on the bottom using #8 screws and clips. I will try and post some pics this evening. I ran them on a big laser cutting machine and had a blast operating the machine. We have a local place here that is setup with expensive CNC type machinery and exists to help small businesses, who can’t afford that type of equipment, rent it for small production runs. These are cut out flat out of 063 sheet aluminum. I stopped by Harbor Freight and bought a new box/pan brake. (Woohoo! New tools) I bent a few up last night and they came out perfect. The costs are only $5 more than what the sheet metal shop was charging me for bending up a blank chassis. I took a pic of "The Laser" machine in action

I also have the custom trannys in stock. I really didn’t like the Hammonds as the Power tranny was running on the edge with the 2 amp rating on the heater current with the tubes pulling 1.8 amps and there was no 240v winding. I had Heyboer build one that is rated at 3 amps on the heater and it also has a center tap so you don’t have to fool with the hum balance thing. They wound it with 2 120v windings that can be paralleled for 120v operation or series for 240v operation. The Iron was also chosen so it is compatable with 60hz or 50hz overseas operation and is a bit thicker in the laminations dept. This changed the mounting hole spacing compared to the Hammond. The OT was also redesigned. I had Heyboer bump the rating up to 4 watts. I wanted to get the inductance up a little also compared to the 125a as I believe more inductance helps produce a little lower frequency response. The Hammond 125a is rated from 150hz – 15Khz. In order to go with the higher inductance (more windings ) on the primary they had to go with 24 ga wire which was too small to be run on their winding machines. Soooooo they had to be hand wound and this increased the price a little more but I think the results are going to be well worth it. The OT had to be mounted in the bracket vertically meaning the wires come out the side. This was done to keep the same hole spacing to mount the OT on the board. It's a little bigger (taller)than the 125a. I should have a test report with the new OT in a few days. PM me if your interested in the pre punched chassis or the trannys.

[soma_hero]

So you start with a sheet of 063 and then CNC laser cut all the holes, and then you've been bending them at home? How easy is it to keep the sheet from warping as you bend it? There's that big cut out for the circuit board, I would be afraid of the metal bowing and not bending level.

They look great!

[UR12]

So you start with a sheet of 063 and then CNC laser cut all the holes, and then you've been bending them at home? How easy is it to keep the sheet from warping as you bend it? There's that big cut out for the circuit board, I would be afraid of the metal bowing and not bending level.

They look great!

No problems so far.. I bought one of these yesterday and it keeps everything straight as an arrow.

http://www.harborfreight.com/cpi/ctaf/D ... umber=5907

I'll post some pics tonight when I get home. I was more afraid of the metal cracking at the bends where the large cutout for the circuit board is but with the new sheet metal brake it is slick and clean as a whistle. They are actually pretty sturdy once you get the board installed.