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A DIY 500 Watt Bass Head

#101
Passinwind said:
And now, Round 2. Since it ain't broke, I'm just going to have to fix it anyway...

Got in the Rev 1.1 boards and stuffed the HPF daughter card this afternoon. This one should integrate more neatly with the preamp module and clean up some wiring clutter, and it also has a few different volume control config options to optimize gain staging. I tried a number of mods on my older standalone preamp and hope/expect to see a modest improvement in signal/noise ratio and distortion ratings as well. I will also be trying the PEQ out with a nominal frequency sweep range @ 200-2KHz this time.

HPFPEQ_1_1.jpg
Click to expand...


You, sir, are a DIY Jedi Master. I hope that my hacks turn out half as well as your projects.

I also like your colorful graphs. You could put that EQ graph in an art gallery.
 
#102
Woodstockz said:
You, sir, are a DIY Jedi Master. I hope that my hacks turn out half as well as your projects.

I also like your colorful graphs. You could put that EQ graph in an art gallery.
Click to expand...

Those EQ sweeps are a nice feature of LTspice. It'd be fun to work some up specifically for artistic purposes, now that you mention it.

Thanks so much for the kind words. I can use them right now as I go through the long, tedious process of debugging and refining -- the proverbial one step back, (hopefully) two steps forward. Took a day and a half to install the new board and get it working reasonably well, then all day yesterday re-installing the old one to leverage what I learned, then late into the night reworking the Spice model. It turns out that I probably will need to replace both preamp section boards at the same time to make my latest design work optimally. I do have a Rev 1.1 preamp board ready to build up too...Rev 1.0 is nearly at end-of-life after all the mods I've thrown at it.<sigh>. On to Round 2.1 today, a gig tomorrow, parts order Monday, rinse and repeat! And after all that, I may easily decide that Rev 1 was better. At least I've finally learned to document mods and keep old board revision files archived.Link Removed
 
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#104
beans-on-toast said:
Looks very nice Charlie. How does the daughter board attach on the new board? Does it simply plug in or are standoffs used that fasten it to the mother board?
Click to expand...

It mounts just like the older one pictured upthread, on the same standoff centers as the main preamp module. It's a bit of a kludge using it with the original main board, but should be be pretty slick once it's mated up with the newer version.

I'm also working up a modular build that will fit nicely on smaller cabs like my TC112. The preamp box will be 8" X 8" X 3", and I'll do a power amp in the same size box, or possibly a slightly deeper one for 700-1000 watt class modules. Stackable, or the power amp can just live on the floor, or maybe in the cab in some cases. Also adaptable to 1/2 rack mounting in a 2RU case. There are lots of nice cheap padded bags out there that could hold both modules, plus cables, a tablet, etc. Here's one (very rough) mockup of the preamp with a 1/2 rack space faceplate, there could be many many other options though, both solid state and tube:

PW7B_halfrack.jpg


And here's the power supply prototype:

PWBPS.jpg
 
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#105
I like the blue color on the mockup. I found a good local powdercoater. I hope to never paint again.

A modular build is nice. You have extra shielding that way and it makes it easier to swap in different pre-amps.

I like the power supply. I see the caps across the diodes. Do you use regular or ultrafast diodes? I tend to use UF4007's since they cost about the same.

Any issues with heat radiated from the heat sinks onto the caps?

Soldering the transformer wires directly to the board helps with road worthiness.

I use Gator Cases G-MIX bags. Good quality and value.
 
#106
I'm thinking blue anodized front panel to match the trim inserts in the case I bought, but powder coating is a definite possibility too.

Ultrafast diodes, just used what John Broskie did in the power supply kit I bought from him -- MUR415.

The heat sinks will most likely never get warm at all at the puny load I built this for, but I still did use 105 degree caps. I expect I could easily just leave the heat sinks out with no issues, but I wanted to play with as many factors as possible since this is a prototype. I'll do a bigger version with more spacing for cooling and more/bigger value caps when the need arises.

Those Gator bags were already on my radar, nearly bought one last night actually. Might take a trip to GC and scope some other candidates too. As always, thanks for the useful feedback!
 
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#107
Passinwind said:
I'm thinking blue anodized front panel to match the trim inserts in the case I bought, but powder coating is a definite possibility too.
Click to expand...

Anodized is good as well.

I'm just done with painting and the associated fumes. I use zinc chromate undercoat on aluminum so that the paint will adhere well. It works well but that stuff is really nasty health wise and requires a lot of precautions. The fumes from enamel paints hang around for days. I realized that it costs less to simply send the work out. Like you do with your cases and circuit boards.
 
#108
All back together now and in the 'WAF rack', and ready for a casual local gig tomorrow night. It's only 5 blocks away, doubt I'll bother to rack it in the SKB unless the weather turns really nasty.

PW8B_BSX.jpg


I managed to work out nearly all the mods I wanted to try even while still using the original daughter card. The volume and master pot tapers feel a lot more intuitive now, the PEQ frequency range is shifted a little higher (200-2KHz), there's more overall gain available but more headroom in the front end as well. When I get the small format preamp built I'll go all-in on trying a bunch of other mods that look promising enough in sims to make me want to take a shot.
 
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#110
JGR said:
Good stuff, look forward to the gig report! Please come over afterwards and help me get rolling again. I will supply coffee and frozen yogurt.
Click to expand...

Mmmm...coffee! Looks like you're back on track just fine on your own anyway though.

So, the gig went well and looks like it will be ongoing. I am now calling this amp at final spec and yesterday I gooped up a few connections and components and I will button things up today and hopefully just enjoy what I've built for a good while. For my tastes this amp works better for EUB than any of the usual well respected suspects that I've owned or tried over the last decade -- not bad for a "practice amp"!

An on to the next adventure...
 
#112
Passinwind said:
Mmmm...coffee! Looks like you're back on track just fine on your own anyway though.

So, the gig went well and looks like it will be ongoing. I am now calling this amp at final spec and yesterday I gooped up a few connections and components and I will button things up today and hopefully just enjoy what I've built for a good while. For my tastes this amp works better for EUB than any of the usual well respected suspects that I've owned or tried over the last decade -- not bad for a "practice amp"!

An on to the next adventure...
Click to expand...



Looks great Charlie! Post some sound clips when you get a chance.
 
#114
Passinwind said:
I'm also working up a modular build that will fit nicely on smaller cabs like my TC112. The preamp box will be 8" X 8" X 3", and I'll do a power amp in the same size box, or possibly a slightly deeper one for 700-1000 watt class modules. Stackable, or the power amp can just live on the floor, or maybe in the cab in some cases. Also adaptable to 1/2 rack mounting in a 2RU case.
Click to expand...

And now, there's a separate thread for that build as it wraps up: A DIY 1/2 Rack Bass Preamp | TalkBass.com
 
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