Bass preamp kits: anybody ever build one?

[EddieG]

I'm thinking about buying a preamp kit to fiddle around with. I've known about the Acoustic 360 kit for a few years now, and it appeals a lot but the guy who makes them doesn't seem to be doing so any more. There's also the London Power preamp with 3 band eq, but they're apparently revamping all their kits with PCBs for 2008.

Anybody got any other recommendations of kits you've maybe heard of, or even had a bash at putting together?

[SoComSurfing]

Lneal built a pre that I believe he calls "Magnum" that looked really interesting. I think PassinWind (sorry if I got the name wrong!) has done the DIY thing, as well.

[Passinwind]

Originally Posted by SoComSurfing

Lneal built a pre that I believe he calls "Magnum" that looked really interesting. I think PassinWind (sorry if I got the name wrong!) has done the DIY thing, as well.

Larry (Lneal) and I both have done a few DIY ones. A9X and fdeck also know a ton about this stuff. Some of mine were based on existing circuit boards that I bought and modified or embellished on, but not from full-blown kits per se. Here's one full kit that looks promising: http://www.madamp.biz/bp1mk1.htm .

Thread on my solid state one that I gig with all the time: DIY rack preamp.

My most recent tube one, based on TubeCAD's Aikido circuit: DIY tube line driver.

There are many more DIY preamp threads on Talkbass as well. I'll be happy to answer any questions that I can here too.

[EddieG]

Thanks Charlie. I was actually admiring your little preamp before, very clean indeed. And sounds good too!

I know absolutely nothing about designing circuits from scratch, but I've put little bits and pieces together before, can read circuit diagrams and know how to solder. Consequently, any option that I go for would have to be all inclusive, and be a PCB as opposed to perfboard.

The Madamp one looks very nice indeed, if anybody has any experience with that, please jump in.

[Passinwind]

Originally Posted by EddieG

Thanks Charlie. I was actually admiring your little preamp before, very clean indeed. And sounds good too!

Thanks! I need to do some new sound clips though. I've done quite a few tweaks to that preamp since I last posted to that thread, and I also now have much nicer pickups in the bass I used for the clip. I should do some EUB clips too -- that preamp kills for that, although I never built it with that in mind

I'd recommend that you spend some time reading through the ESP website, if you haven't already. Rod makes some nice boards for many of his projects.

[A9X]

Originally Posted by EddieG

I know absolutely nothing about designing circuits from scratch, but I've put little bits and pieces together before, can read circuit diagrams and know how to solder. Consequently, any option that I go for would have to be all inclusive, and be a PCB as opposed to perfboard.

The Madamp one looks very nice indeed, if anybody has any experience with that, please jump in.

If you can read a schem and solder, whay not just scratchbuild a copy of an existing design? With tubes I never use PCBs except for ancillary ccts such as regulators. I do everything point to point with turret boards. I dislike tube sockets mounted to PCBs as the flexing of the board (unless well supported) leads to cracking and failures when changing tubes.

Alembic F2B is easy to clone (I have cct and PSU schematics) and easy to mod/update.

What do you want this preamp to do in terms of features?

The Madamp kit is the best I've seen suggested so far.

Originally Posted by Passinwind

I'd recommend that you spend some time reading through the ESP website, if you haven't already. Rod makes some nice boards for many of his projects.

Rod's site is excellent, but everywhere he has a TL072, replace it with an OPA2132.

[Passinwind]

Originally Posted by A9X

Rod's site is excellent, but everywhere he has a TL072, replace it with an OPA2132.

+1

Rod himself mentions this quite frequently, FWIW.

[EddieG]

Well, I got rid of my existing gear, and so after Christmas and New Years is out of the way I'm going to put together a whole new rig for myself; pre, poweramp and cab. I guess what I'm looking for is the nice, raunchy sound you'd get from a tube amp, but with the extended volume a power amp gives you. To that end, the Madamp is looking increasingly attractive.

[BassmanPaul]

Originally Posted by Passinwind

Larry (Lneal) and I both have done a few DIY ones. A9X and fdeck also know a ton about this stuff. Some of mine were based on existing circuit boards that I bought and modified or embellished on, but not from full-blown kits per se. Here's one full kit that looks promising: http://www.madamp.biz/bp1mk1.htm .

Thread on my solid state one that I gig with all the time: DIY rack preamp.

My most recent tube one, based on TubeCAD's Aikido circuit: DIY tube line driver.

There are many more DIY preamp threads on Talkbass as well. I'll be happy to answer any questions that I can here too.

I built a two channel pre based on the front end of my B15 turned out well. Passing Wind's preamp thread and A9X introduced me to the Aikido concept which I fell in love with. I am working on a design featuring this circuit. It's all on hold at the moment 'cos I got hit with a stroke on Dec o5 that has me coffined to my home. Still parts are on their way.

If the OP is serious about building a pre, a kit like Kevin O'Connors' London Power kit would be an ideal learning tool. Don't worry about using a PCB in a preamp. Although I do prefer point to point wiring you have to have some experience to do it ptoperly and a properly designed PCB eases construction a lot.

Merry Christmas to one and all and a happy new year!!!

Paul

PS Did Larry (Lneal) ever post his schematic????

[fdeck]

If you are mainly interested in experimenting and learning, and are going solid state, I suggest using a cheap solderless breadboard strip. I have done a lot of my audio prototyping with breadboard. At one time I had a breadboard inside a metal case with holes for pots and jacks. I could even attach the cover and take it to a gig, so long as I was careful.

[A9X]

Originally Posted by BassmanPaul

It's all on hold at the moment 'cos I got hit with a stroke on Dec o5 that has me coffined to my home.

Paul, I'm sorry to hear that. I hope your recovery is speedy and complete. All the best.

[BassmanPaul]

Originally Posted by A9X

Paul, I'm sorry to hear that. I hope your recovery is speedy and complete. All the best.

Thanks for the well wishing my friend. It was most unexpected - I'm on enough blood thinners it shouldn't have happened! It's actually my second, the first in 05 left me with a hole in my vision that has gradually cleared up and this one is very close to the last so not much change really. I'm still in here and I can still play and THAT'S the important thing.

In the preamp thread with Lneal you suggested he use I think Sowter iron for his OPT. I was wondering if you can suggest a suitable model number? I was thinking o Jensen or Lundahl (SP) but being an ex Brit I kind of fancy using something from the old UK.

Thanks

Paul

[A9X]

Originally Posted by BassmanPaul

Thanks for the well wishing my friend. It was most unexpected - I'm on enough blood thinners it shouldn't have happened! It's actually my second, the first in 05 left me with a hole in my vision that has gradually cleared up and this one is very close to the last so not much change really. I'm still in here and I can still play and THAT'S the important thing.

I'm glad you're feeling better.

Originally Posted by BassmanPaul

In the preamp thread with Lneal you suggested he use I think Sowter iron for his OPT. I was wondering if you can suggest a suitable model number? I was thinking o Jensen or Lundahl (SP) but being an ex Brit I kind of fancy using something from the old UK.

Thanks

Paul

Glad to, but I'd need to know the detail of the CCT before I could comment. Got a schem for me?

[BassmanPaul]

Originally Posted by A9X

I'm glad you're feeling better.

Glad to, but I'd need to know the detail of the CCT before I could comment. Got a schem for me?

You all readdy got it - I'm going to use the Aikido.

Paul

[A9X]

Originally Posted by BassmanPaul

You all readdy got it - I'm going to use the Aikido.

Paul

I'm not a big Sowter user as I get Lundahl iron at good prices and love it. That said, I like the looks of the 9900
http://www.sowter.co.uk/2preline.htm
but it's a bit exxy. Brian will normally wind something for minimal additional cost if you ask. I bet he has hundreds of other designs on files that aren't in the std product lineup.

From Per's stable I would suggest the 1660 (reversed 2.25+2.25:1+1). 1674/6, 1680 or maybe even 1538XL. Depends on the turns ratio you need. The 1680 would be most flexible as I can see several ways to wire it parafeed for different TR's (9+9:2+2, 9//9:2+2 or 1+1)

I was recently going to buy some 1680's as parafeed autoformer outputs for a dynamic headphone amp, but found one of my existing OPTs worked nearly as well. I have some 1660S on order as interstages for hifi amps.

[BassmanPaul]

Having another look over my last posts, mmmm Coffined in my house - if that ain't a freudian slip Idon't know what is!!!

I have no drawn-up schematic as yet it's all in my mind. Basically a two channel preamp using the Aikido circuit. Each output leg doubled one leg to drive the power amp via OPT and the other a transformer isolated DI. Power will come from a specially designed toroid wound by a local company. No EQ at all, I run all the ones I have flat anyway. One rackspace with the tubes wired to the Aikido board via pigtails.

The DI section is still questionable. At the moment I am leaning towards mic'ing my cabinet and thus the DI will become a Mic preamp instead, still Aikido though.

That's where i'm at at the moment.

Paul

[Passinwind]

Originally Posted by BassmanPaul

Having another look over my last posts, mmmm Coffined in my house - if that ain't a freudian slip I don't know what is!!!

That's exactly what I was thinking!

Best of luck with both your health and your project. By all means PM me if you want any gory details about any of the stuff I used in my two Aikido based builds. I used tube-specific Jensen iron on both the input and output of one (it only takes two days to get in-stock Jensen trafos to my house), while the other one is just capacitively coupled. The second one will get a major makeover sometime next year, since it's currently done in a very ugly terminal strip-plus-true-PTP fashion.

[BassmanPaul]

Originally Posted by Passinwind

That's exactly what I was thinking!

Best of luck with both your health and your project. By all means PM me if you want any gory details about any of the stuff I used in my two Aikido based builds. I used tube-specific Jensen iron on both the input and output of one (it only takes two days to get in-stock Jensen trafos to my house), while the other one is just capacitively coupled. The second one will get a major makeover sometime next year, since it's currently done in a very ugly terminal strip-plus-true-PTP fashion.

Thanks on both counts Charlie, I may well take you uo on that offer.

Paul

[jar240]

Originally Posted by BassmanPaul

No EQ at all, I run all the ones I have flat anyway.

I'm curious... by "flat" do you mean you have all the passive EQ controls turned up to max, or set to half (12 o'clock)?. If you leave the (passive) EQ section out of your preamp, your tone will be equivalent to turning all the tone controls to full , plus more gain due to the lack of EQ section losses. Am I out to lunch on that?

To the Original poster: I've built London Power's BPK (bass preamp kit) and the 13VA power supply. This is definitely more advanced than buying a PCB kit. Kevin does chart out the schematic and layout for the components, but they're based on a point-to-point circuit card. You have to cut the circuit card, transfer & scale the component layout, drill holes for the eyelets, apply the eyelets using a staking tool, try to drill equal spaced holes for mounting the circuit card to a chassis that you have to do all the metalwork on and plan the overall layout. I put about 20 hours into mine. It sounds really good, but may require a little more circuitry (i.e. a buffer) to make the output impedance more universal.

The rest is the same effort as a PCB kit.

Having said that, it really was a lot of fun, and a learned a lot more than I would have if I'd gone with a PCB kit where the components are ready solder/assemble.

Come to think of it, I ordered two of these kits, and have a complete kit untouched if you're interested. PM me.

I'm working on building a 120W KT88 "BFA" tube amp that this fellow Canuck built:
http://www.diytube.com/phpBB2/viewto...asc&highlight=

Chris

[A9X]

Originally Posted by jar240

I'm curious... by "flat" do you mean you have all the passive EQ controls turned up to max, or set to half (12 o'clock)?. If you leave the (passive) EQ section out of your preamp, your tone will be equivalent to turning all the tone controls to full , plus more gain due to the lack of EQ section losses. Am I out to lunch on that?

There are no tone controls in Broskie's Aikido. Not installing any simply means a flat response, which is not what you get with some tone stacks set to 10; download the Duncanamps.com Tone Stack Generator and experiment to see how they actually work. Gain in the Aikido is basically determined by the gain of the first stage, ie what tube chosen.