Bass Amp for a friend

[Colossal]

Hello friends,

I have a buddy who is in need of a bass amp. I am looking for recommendations of topologies and/or schematics. My friend plays a Rickenbacker 4001 which has a great, punchy and articulate sound. He likes players like Chris Squire, Geddy Lee, John Entwistle, and Sting for instance. The goal in mind is simplicity and purity of tone. My friend is not one for a lot of bells and whistles (nor am I). A single channel topology with a tone stack or tone controls placed along the signal path with a good, clear, and punchy presentation is what I'm after. Some natural overdrive with good touch sensitivity is desirable so long as the low end does not (ever) collapse into blocking distortion. Looking for punch, clarity, sustain, and string-to-string separation with a piano-like clang. 100-120W would probably be plenty of power but am open to any ideas. Speaker cab will likely be a 4x10.

Thanks for any ideas/suggestions/experiences.

[xtian]

Review my work here:

https://ampgarage.com/forum/viewtopic.php?t=22434

This is a SE amp with KT88 power, and a line out to feed external solid state power amp. Came out sounding very good; owner was happy with the design.

[Colossal]

Review my work here:

https://ampgarage.com/forum/viewtopic.php?t=22434

This is a SE amp with KT88 power, and a line out to feed external solid state power amp. Came out sounding very good; owner was happy with the design.

Well that is interesting. I actually have a very stout 2k SE OT. A tube preamp out to a solid state power amp might be a good fit as well. But think I will stick to an all tube design for now. Maybe a pair of KT88s in UL or something else.

[echuta13]

I've thought of doing a p-p KT-88 bass amp and I'd like to think that they would have enough umph to keep a bass player happy, plus KT88's seem to stay more linear than other tubes for the most part.
One of these days... I'll get around to it.

[didit]

Review my work here:

https://ampgarage.com/forum/viewtopic.php?t=22434

This is a SE amp with KT88 power, and a line out to feed external solid state power amp. Came out sounding very good; owner was happy with the design.

Well that is interesting. I actually have a very stout 2k SE OT. A tube preamp out to a solid state power amp might be a good fit as well. But think I will stick to an all tube design for now. Maybe a pair of KT88s in UL or something else.

Class AB KT88 UL with a dangerous HT voltage == clean solid thump. Need right output transformer, and won't be small or cheap. Aaron's suggestion of class D power off a tube preamp will be remarkably similar, and easier to build and to carry.

Best .. Ian

[Colossal]

Class AB KT88 UL with a dangerous HT voltage == clean solid thump. Need right output transformer, and won't be small or cheap. Aaron's suggestion of class D power off a tube preamp will be remarkably similar, and easier to build and to carry.

Best .. Ian

Yeah, a tube preamp into a SS power amp would make for a nice, compact rig that is hard-hitting with plenty of power. A pair of KT88s in AB U/L though...

[Stevem]

Your buddy will not get the tone and punch he's looking for out of a 4-10" cab for live usage in the average club, and certainly not if he plays or will in the future use a 5 string Bass!

I have played Bass in some 8 bands for over 48 years doing covers and originals and to cover all of that sonic ground I found that a 2-15" cab works best.

My cab is loaded with one EV Bass driver and one EV guitar driver and it's ported.

I got my first 4-10 cab near 20 years ago and I have used it twice ,once by its self at a small size gig and once along with my 2-15" cab when the stage had the room for it.

The only concideration is it heavy with those huge magnets of the EV drivers, but anyone who has ever played thru it when I lend it out smiles ear to ear in all of 3 seconds of play time!

My normal amp is a 125 watt RMS SS 1971 Kustom 250, and when I need more brute power when I play my 5 string then it's time for my 400 watt RMS Kustom.

Those low B strings sap up wattage like mad!

[Colossal]

Your buddy will not get the tone and punch he's looking for out of a 4-10" cab for live usage in the average club, and certainly not if he plays or will in the future use a 5 string Bass!

I have played Bass in some 8 bands for over 48 years doing covers and originals and to cover all of that sonic ground I found that a 2-15" cab works best.

My cab is loaded with one EV Bass driver and one EV guitar driver and it's ported.

Hi Steve, my friend has only ever played four string and that Ric at that. So I don't see him changing after all these years. That said, he hasn't chosen a cabinet(s) and he doesn't know he is getting an amp, so options are on the table. My goal is to build him a proper amp. He likes to play with friends on rare occasion as time allows and he has never had real tone, always sacrificing for his kids instead.

I got my first 4-10 cab near 20 years ago and I have used it twice ,once by its self at a small size gig and once along with my 2-15" cab when the stage had the room for it.

I had a roommate some 25 years ago that played a P bass through an SWR 400W tube preamp/ss power amp head into a 4x10 and that thing sounded like a piano. Very lush and present sound. My buddy will likely build a cab or cabs based on what I suggest he do, so a pair of 12s or 15s is certainly reasonable.

The only concideration is it heavy with those huge magnets of the EV drivers, but anyone who has ever played thru it when I lend it out smiles ear to ear in all of 3 seconds of play time!

Well, you can't argue with an EV. They sound great. What about a pair of TL606 ported cabs? My buddy is an ape of a fellow so carrying a ported cab with an EV in each hand would not be an issue.

My normal amp is a 125 watt RMS SS 1971 Kustom 250, and when I need more brute power when I play my 5 string then it's time for my 400 watt RMS Kustom.

Those low B strings sap up wattage like mad!

I'm thinking a pair of KT88s or a quad of EL34s is a good place to start for this project. Power supply will be SS with heavy filtering, maybe a CLC in front. I'm not penny pinching or wringing hands over cost here.

[TUBEDUDE]

Traynor made some nice bass amps with 6550/KT-88 pairs.

[Colossal]

Traynor made some nice bass amps with 6550/KT-88 pairs.

I saw a new 4xKT88 on Reverb for $1009 Surely that must be overseas manufacture?

I am looking at the Genalex KT88 datasheets and a pair running 560V B+ in Class AB U/L will put out 100W into a 4k5 load or at a more modest 460V B+ 70W into a 4k load. A quad would put out 140W into 2k. For a pair, a cathode/fixed bias switch might be useful for reduced power but also feel.

[lumox0013]

weber has a 2xkt88 kit , the 6s100 with 2k ? output not ul though might be a good starting point. I always liked the sunn stuff. cheers

[Colossal]

weber has a 2xkt88 kit , the 6s100 with 2k ? output not ul though might be a good starting point. I always liked the sunn stuff. cheers

Thanks for the tip on the 6S100. I checked out the schematic. That is similar to what I'm thinking.

[ER]

Just some ideas and opinions to throw out there.
Look for a Peavey T.B. Raxx pre for cheaper than you can build something and go through it, get an inexpensive SS or class D stereo power amp in what ever power class you need and build two cabinets, one for lows and one for highs. That would be something like a ported 15" on the bottom and sealed 2x10" on top, or like I made for my daughter, a 4 ohm 18" JBL in a TL505 type cab and a pair of Gauss 12"s in a sealed cab. Use the channel volumes on the power amp to further balance and EQ the sound, more low end, or more punch and clarity depending on which cab you dial in. I also put a T.C. effects unit in there so she has killer chorus, octave, and compression right there. We're only pushing 130 watts per channel and it's plenty for now.

I think Chris Squire used both a bass amp and a guitar amp with his ricky's stereo out, I look at it kind of like that. When I finish my Daughter's Alembic Bass I'm going to build a stereo pre for it so the bridge pick up will go to the 2x12 and the neck pickup to the 1x18, but with her fender type bass it sounds great with the single pre doing it this way for now.

If you need to lighten up the load use a class D power amp, neo speakers and 1/2" ply with glue, dados, and bracing for the cabinets. Stay with efficient speakers and good old fashioned big cabinets. Power is cheap these days, but 2000 watts going into a farty little inefficient cabinet is where I hear most bass rigs falling flat on their face these days.

[didit]

Traynor made some nice bass amps with 6550/KT-88 pairs.

YBA-3 CSa w. 4xEL509, which is similar to KT88. Rumour has it, it was seeing that amp that motivated Armstrong to design Ampeg's SVT.

A Dynaco A451 with +600V in UL with a pair of current KT88. For speakers two cabinet rig with 2x10" over a 1x15". Or do what Traynor originally had, which was a 6x10". And never worry about that perfect impedance matching thing again.

Best .. Ian

[Tony Bones]

There's a design for a 100W KT88 amp in the classic GEC book (as well as other tube amps up to 1100W.) For a bass amp, I wouldn't hesitate to use good quality "hi-fi" rated design and transformer. The extended frequency response is important.

http://www.tubebooks.org/Books/GEC_approach.pdf