Mikey R

We've been forgetting our very own Jim Fleeting over in Harrogate: [url="http://jimfleetingguitars.com/"]http://jimfleetingguitars.com/[/url]

Are the depth and drive knobs actually rotary switches? Billy, did I play your rig at a bass bash the other year?

[quote name='charic' timestamp='1373531575' post='2138589'] How about £0.11 a watt [url="http://basschat.co.uk/topic/211499-1600w-quantum-matrix-poweramp-l175/"]http://basschat.co.u...-poweramp-l175/[/url] [/quote] If we dont want all off the watts, are you willing to split? (Someone was bound to make that joke!)

Ive been burned - £26 per watt for my rig! But these are big round Barefaced Ashdown valvey watts, as my neighbours will confirm

[quote name='bluejay' timestamp='1373190359' post='2134431'] Bump because this is a brilliant thread, and here is a photo of Happy Jack with his new Matamp, taken at the Junkyard Dogs' gig last night. The amp (as well as the bass and cabs!) sounded awesome [/quote] OMGOMGOMG - a Matamp on top of two Barefaced! Thats got to be absolute heaven! Jack must be Happy indeed! For the top end, you might be able to give the Matamp lads a call and get them to change the tone caps and / or alter the gain of the input stage. They should be able to make you the exact amp youre after. If you do, bring hobnobs.

Valve amps have switchable impedance. If, for example, you are used to plugging two 16 ohm cabs into the amp, then the amp should be set for 8 ohms. If you only plug the one cab in, then you should switch the impedance selector to 16 ohms.

My brother is a pro keys player and uses a Triton, and still uses it after nearly a decade. The downside is that they are still incredibly expensive, compared to what you might get from Roland or Yammy.

I was playing around with a design this morning, its actually going to be a hybrid design, with valve input stage, solid state EQ, and a valve overdrive section (the second valve section from the Bassman, with the directly coupled cathode follower). I was unsure about whether the EQ should precede or follow the overdrive section, but Ive figured out a way to make it work how I want. The bass frequencies bypass the overdrive section, so you always get the low frequency thundering presence. The bass control just controls the gain on this path (+15dB, to - infinity). The treble control, when set to boost (up to 15db), boosts pre-overdrive to really drive the valve hard. When you wind it down to cut (down to - infinity), it cuts post-overdrive, so you can cut out all the fizziness if needed. Its a modified Baxandall, with one half of the pot forming part of a potential divider controling the gain directly, and the other half a part of a potential divider controling the negative feedback. I still need to prototype it on breadboard to make sure it'll work, but you can do things with opamps that wouldnt be practical with valves. EDIT: Heres the gain curve for the bass and treble pots, +15dB to -inifity:

Of course, the other option is to take a balanced out from the solid state preamp. This would also simplify the build, as the global negative feedback components would be mounted to veroboard instead of tagboard.

I need to check my values, but Im pretty sure theres tons of headroom on the concertina so the output valves will be driven way into class AB2 by the time the concertina starts to clip. And at that point, its going to be LOUD! If the load of the concertina is perfectly resistive, or close enough, then you get better balancing than you would with a long tailed pair. Adding another trim pot into the design is just something else to forget to tweek when youre servicing the amp over time, and is something I dont want to have to worry about - I would much rather it was well balanced by design. Yeah, Im starting to have doubts about the power supply. However, John gave me the design, its pretty much the bass amp he's been building for clients for years, and Im willing to bow to his experience here.

Hey Umph, will post it when Ive got it to hand. The power amp is based losely on the bastard child of a Marshall Major (concertina phase splitter driving a long tailed pair) and a Hiwatt 405 (cathode followers driving the grids of the output valves). I'll add individual biasing for each output valve on the advice of John. Ive recalculated the values using the curves from the Chelmer Valve ECC81/2/3 datasheet, and pretty much followed the recommended operation from the 6550 datasheet for class AB1. If you look at the schematic for the Hiwatt STA preamp, its not so far to change the cathode follower of the ECC83 into a concertina, by splitting the load resistance (100k in the schematic below) between the cathode and anode. If you do this, then, since the ECC81 has such a high input impedance, each grid will see perfectly equal but opposite polarity siginal, therefore you dont need to use different load impedances (33k and 39k in the schematic below) on the anodes. Regarding the layout, yes it was a compromise. I had a choice between orienting either the PT or the chokes at 90 degress to the OT, the only way to have all three orthoganal would be to use a lay down type power transformer and that would have come with its own difficulties. From what Ive read, chokes tend to be noisier than transformers, so they were the critical component to be 90 degrees to the OT. Im not concerned, since the Hiwatts, as well as the big Orange and Matamp chasisse that Ive seen picture of have had their PT and OTs in the same orientation.

[quote name='umph' timestamp='1368987165' post='2083731'] Looks good, just wondering why you went for a choke on both the power supplys? Resistors would've been fine and saved a lot of space. [/quote] There would be quite a bit of current flowing through those resistors, so I wouldnt be happy with the dessipation or the voltage drop. Next one I build probably wont have dual chokes, but this is an experiment in overengineering.

Ive 5 at the last count - a couple of basses that just wouldnt be worth selling, another one thats still broken after 15 years and still not been fixed, and one Ive lent to Mert. And then Ive got The One, my blue P bass I built at Jon Shukers gaff. Its not perfect, but its mine. And soon to have some home wound pickups too.

[quote name='JapanAxe' timestamp='1367829523' post='2069776'] That's very tight! Maybe MDP will lend you his big triangular 'zero fret' file to create some more clearance? [/quote] Yeah, it was too tight for comfort, I bought a bigger punch and widened out those holes, theres plenty of room now. [quote name='VTypeV4' timestamp='1367855404' post='2070262'] Can't believe I've missed this till now..! Looks like a great project, Beavis on steriods eh!? Great project, keep the pix and info rolling! [/quote] Cheers dude, its going to be a bit of a slow project, Im feeling my way dead slowly and making sure Ive got it right. The big Sovtek 6550 output vavles have arrived in the post Bigger than an EL34 but a little smaller than a KT88, I was worried they wernt going to fit in the small space behind the transformers, but its ok theres loads of room. EDIT: Just took a quick shot to show the scale of these mahoosize components, thought I'd share it here too: Thats a 50 pence piece for scale

Rather than start a new topic, thought I'd post this in here. Ive been reading through some threads in Amps and Cabs, and there seems to be a trend. In the late 90s, I used to play with quite a loud rock rap band. We had a hard hitting drummer and the guitarist used a 4 x 12. Because of the hip hop influence, most of our songs were driven by the rhythm section so were kinda bass heavy. All of this, and I kept up with my old (new at the time) Trace Elliot GP7SM 150 watt combo. This had the slotted front port and the smaller (10 inch maybe?) driver, so was probably far less efficient than a modern Neo loaded cab. Since I wasnt using an extension speaker, this was probably putting out around 80 watts. So why, as bassplayers, are we feeling the need for a half kilowatt stack for the low end? Are we competing with guitarists with terrible scoopy tone? Do we just like the headroom?

cheeky git - I hope youre looking after the brown bass!

I decided to stop procrastinating and start on the metalwork for the chasis. First will be to build the power supply and verify that works, so I started cutting the holes for the transformers, chokes and the big caps. Marking out, the old school way using paper templates. I really should have drawn these out on sqaured paper to ensure I got everything square and in perfect alignment, but I got pretty damn close using a lower fidelity method: Last minute check to make sure everything fits: And with the bulk of the holes cut: I still need to deburr these holes and cut the holes for the bridge rectifiers and circuit boards mounted inside the chasis. Still, its a good start. Checking that the holes are in the right place for the capacitor mounting clips: And the inside of the chasis: Its a little tight, and theres not much space between the terminals and the chasis. I can either file out a little around the terminals, or fill the void with hot melt glue. I'll probably do a bit of both, I dont want sparking here.

[quote name='MiltyG565' timestamp='1366896454' post='2058708'] Nope, that's not potato bread! [/quote] But its still breakfast. [quote name='Jack Cahalane' timestamp='1366910339' post='2058988'] I live on the Isle of Man Okay no I don't. [/quote] Bits of England arent on the mainland...

[quote name='richardjmorgan' timestamp='1366734146' post='2056609'] As someone who plays guitar in a metal band that lost its bass player earlier in the year and, as such, has been doing a fair bit of playing with just two guitars, drums and vocals, it makes a BIG difference. Funnily enough, it's given us a much clearer idea of exactly how we want the bass to work within the band, part of which is for it to be a lot more prominent in our overall sound. [/quote] Since youre a bass player, why not reorchistrate your songs for one guitar and bass? Playing bass in the three piece is awesome fun, you get to fill out the rhythm line AS WELL AS playing the bassline. [quote name='simes' timestamp='1366742820' post='2056764'] But what is the best bass for metal, that is the eternal quest.......... [/quote] Easy answer - MINE. But any way, back on topic - potato pancake, you make it with last nights leftover mash and some grated onion, eat it with egg, bacon and beans. The correct way to make it is plate sized and put the other stuff on top. Propper breakfast.

All the best looking people wear glasses. Just tie them to your head, you can headbang all night.

Just compare the guitar tone from Metallicas "Justice for All..." album with the black album three years later. Sure, they spent alot more on the studio, they layered more, and Bob Rock brought alot to the sound, but fundamentally that huge sound is from the guitar being supported from below by the bass played in unison. On Justice, the guitars are boomy and undefined, because James Het was boosting his own low end trying to get that huge sound without a bass player.

Cheers guys, I reckon its going to be the ones from Bluebell. I need to nail down the circuit first though, and I really seem to be procrastinating over that.

[quote name='Mr. Foxen' timestamp='1366292150' post='2050602'] Gas soldering iron exhaust is what I generally used. I've got a fitting for one of my gas irons for the purpose too. [/quote] Cheers Oli! Any suggetions on where to get turrets?

Cheers for the suggestions gents. Yep, hot air gun is the orthodox way to shrink your tubes (!) but I didnt have one handy, I dont think the hair dryer would be hot enough. But I didnt think of using a soldering iron - good suggestion bartelby! So ignoring the heat shrink for the moment (which might not even be necessary) I had a play with how the wiring would look on the actual bases: This single strand wire holds its shape niecely, I dont think the PTFE stuff will be quite so well behaved.