Vote for Ike in 2008

[dhuebert]

Ampzilla! Push pull parallel! All octal! A quartet of KT88s a side! Effects out for optional tone controls and recovery stage. I'm countin' on ya , buddy!

Don

[EWBrown]

And a somewhat more "modest" 6L6GC PP axe amp could probably go pretty much stock on the Rev A boards, just suitably lower the B+ voltage and adjust the grid bias as needed, and probably leave out the NFB loop for that great "tone".

IIRC, Blair's "big amps" are close to the Ampzilla concept, but with six packs of 6550Cs or KT88s, I'd call them "the hexapods" perhaps ;-)

Recently saw a nice clean looking Tremolux II at a local "everything" shop, but the owner wants "real" money for it. I told him I can repair and modify tube amps, and gave him my name and contact info, and mentioned diytube.com as my "references". He told me the local musicians here really want and need a local guy to do the tube "tech work" rather than having to travel 100 miles to Asheville. We'll see what transpires...

I told him I'd do SS amps "only under duress" ;-)

/ed B

[Shannon Parks]

Looking at a Rev A board this morning I had a revelation. The biggest obstacle was reusing the snap mount caps. They really add a lot to the price of the project, and the ground plane snugs up close to where the cap lug overhangs (leaving an airgap fixes this violation, fwiw). But I still do have gobs of these Nichicon 220uF, 250V caps left from the original ST35 project. They are fantastic caps with low ESR, and their radial leads are a perfect match. Limits us to 500V, but I was planning on lower voltages anyway. Throwing the caps in with the boards would save maybe $60.

Off to a funeral.

[dhuebert]

500 volt B+ would give around 100 watts which would be OK, but... The problem is that until the tubes warm up and start drawing current the B+ would probably go to ~ 540 Volts which would stress the caps heavily and lead to reliability issues. This means your B+ couldn't be much higher that ~460 volts making maybe 60 or 70 watts, not enough. Time to scratch think. 535 volt B+, 6550 or KT88, has to be a quartet to keep damping factor low... I guess I've said all this before, don't mean to sound like a broken record but the idea of a line amp with effects out for optional tone controls and phono preamp and a real 100 watt output all with DiyTube logos all over it seems really worth doing. Enough of the clones, it's time to jump out of the perfectly good airplane.

Having said all that.. I have enormous respect for what you have already accomplished. And in spite of all the advices, you have to find the right road for you and I have every confidence that whatever you come up with will be top drawer.

Don

[dhuebert]

What about moving the caps off-board to the chassis? I have used the JJ caps that tubesandmore sells with excellent results. They have a cap that is 800uF @ 375 volts for $14, a quartet of those will do the job admirably. Although $56 for just the caps per channel might be a little daunting! Just a thought.

Don

[nineno]

The Eiclone is one of my two major focuses for 2010 (a phono stage is the other). One tendril of the Ike will be re-tooling a design using the Rev A boards and probably 1625s. The other tendril is a bit unfocused, though Ikezillas remain a possibility. What do the guitar amp guys want?

It sounds like a lot of guys have good and more informed opinions here that I have. So, take the rest of what I have to say about guitar amps with a grain of salt. ; )

First, I don't play guitar - I have a few friends that do; they're in a band together; somewhere along the line I became their sound guy.

3 or 4 of the guys in the band have heavy metal backgrounds. The guitar player used 100w Marshall heads through one or two 4x12 cabinets and the bass player used an Ampeg SVT Pro with six 10s for their early part of their career. Now that they're older family guys - they're finally learning to play with the volume set lower than 11.

The (much younger) lead singer/rhythm guitarist is playing through a Mesa Boogie Lonestar Special 12" combo - he loves that thing. The lead guitarist played his first gig through a Fender Tweed Deluxe last weekend and he was actually OK with it.

The bass player tried using some 20-pound 15" digital amp thing - it had plenty of volume but sounded flimsy, so he's not buying into the 'less is more' concept just yet.

So where could Ike fit into this? Here are a few thoughts...
- A nice 15-35w all octal all tube amp
- Generally setup to be a head (using a stock sized Hammond or similar chassis)...but someone could certainly make it a combo if they wanted to.
- It's REALLY nice, as a sound guy, when the guitar players have a Lead Boost foot switch. Incorporating that would be amazing. Have a rhythm gain and a lead gain...it could be as easy as toggling the same input signal through two different attenuators or it could be as complex as having an additional gain stage to get more distortion. I really don't know how Lead Boosts are normally integrated, but certainly someone here does.
- In addition to a Rhythm and Lead gain, then have a master volume...duhh, right?
- Taps for a tone section would be great. No need to incorporate them on the board, but just have traces on the board to a screw terminal pad that allows the builder to insert a passive tone stack...easy-peasy (says the guy that is not designing anything.) ; )

Now here's some pie-in-the-sky stuff that would be awesome, but perhaps way outside of the reach of this project...
- Multiple power settings (like the previously mentioned Lonestar Special). If the amp had a high and low power setting, like 15w/30w or 20w/40w, that'd be awesome. Take a pair of P-P power tubes out of the circuit and have the remaining two do the work. But, I assume that would require a multi-tap transformer and a lot of messy signal and HT switching.
- Diode or tube (Weber Copper Caps??) rectification selection
- Input tap for spring reverb tank..?
- The ability to build a bass or guitar amp from the same board with different components...even crazier -> same amp that's switchable between bass and guitar. Ok, that might be impractically hard and not very valuable...
- Hi-Z or Line level output...

So there's a laundry list of things that would be really neat in a mini-head. After writing that all out, it seems like the amp I've proposed has far too little in common with Ike for that to be a realistic starting place. This may also include features that are too boutique or specific for things a sound guy - not a guitar player - want in an amp.

As for the phono-amp PCB: I'll buy one.

Drew

[jonnyeye]

For guitar use, I personally would like an output stage only board (one which takes nominally 0.7VRMS input for full output power) and then let the end user choose their own preamp. The board could then also be used as a hi-fi amp as well (like the Ike). I may be an exception in this.

Then, I'd like to see a power supply hookup like this:



which is configurable for full wave centre-tapped (use B, D, and E); full wave bridged (use A and E tied together, B and F tied together); and full wave doubler (use C, and B and E tied together).

Also, make the screen supply switchable (probably using an onboard jumper) from X to Y. This is for sweep tubes - for instance, the 6W6 which have the same pinout as the 6L6, and the 6BQ6 and 6DQ6, which have almost the same pinout as the 6L6 (the difference being the plate is tied to pin 3 on the 6L6 but goes to a plate cap on the 6*Q6). These tubes are all pretty cheap (as little as $1 each for 6BQ6, about $6 for 6DQ6Bs), make good power (35W is easy with 6BQ6s, 60W from 6DQ6s) and plentiful.

With these two in place, amps from 15-100 watts could be built on the same board, using 6AM/7S/7AC/8ET based tubes (6DG6/6W6, 6V6, 6EY6, 6EZ5, 6BQ6, 6DQ6, 6L6, EL34, KT88...)

Other things which might be nice include active screen regulation (for hi-fi or bass amp use) and more output tubes (although more than a quad would probably start pushing the board price a bit high, due to all the board area required).