Anyone built a bass amp?

[selloutrr]

The Major is a great amp (200watts) but they really need NOS tubes to make them sing. I'm running a Quad of KT88 GEC Gold Lion in mine.

[RJ Guitars]

I'm a lover not a fighter ...

I understand... I am not really all that passionate about my thoughts on the topic. More fearful that it confirms I am getting old and losing perspective. It's a bit funny as I read my own words because I am not really known for holding back on the volume. I'm kinda like Mark Fowler in that it brings a big smile when I get to hear one of my amps cranked. Of course it depends on how big the venue is but for me the days or dreams of playing major venues and needing a 10K Watt sound system isn't likely. We usually balance our volume with the drummer and that still can leave the ears ringing at the end of the night.

Technically it might have something to do with high frequency hearing loss and all my ears are capable of hearing is the low end stuff when I really need that snare in my ear.

I love bass playing that is both the backbone of the band and yet is an intertwined piece of the melody. McCartney is one of my all time favorites. I know he plays with a pick and technically was not incredible but he just has such a great sense of melody and did all that while he sang.

rj

[rdjones]

So we never got any real feedback on what you guys feel is appropriate wattage for various venues. I don't know how bass amp SS vs. tube watts compare in a performance setting and so I'm having a hard time judging what will be "too much" for our bass player. Is a quad of KT-88's too much?

I've quizzed a bunch of my pro bass player buddies as to this very question.
"What is the minimum power level requirement for a tube bass amp to handle a majority of live situations?"
I have a Bassman 135, 4x6L6 ultralinear. I was hoping that it might fall into the acceptable category,
but most of the answers I got seemed to average in the 200-300 watt range.
Many players have either an SVT or 300-400 watt SS rigs.

Non-SVT tube amps I've seen being used for bass include old Sound City, Traynor Custom Special, and Ampeg V4B.
I also talked to a country bassist at a small gig using a Showman that he really liked.
But he said for bigger shows he really needed more power.

To answer your question, I think 4xKT88 (or 6550) is "just right".
Any less is seemingly inadequate for a majority of gigs, and anything more gets to be too heavy.
An SVT is too heavy for me, that is.

I have an OT that's a bit larger than the Bassman 135 that I'd like to work up with 4x6550 or maybe 6x6L6 ala StudioBass or SuperTwin.

rd

[rdjones]

I'm guessing 100-120 Watts would cut what 90% of us would need. It depends a lot on what kind of music you play, I would think a country bassist would not need as much volume as a funk bassist as his part is more in the background and subdued. A funk, Jazz or Heavy Metal player might disagree with me wholeheartedly on the 100 Watt theory.

Yes, the country player may not be as dominant in the mix but will be less tolerant of
distortion and clipping than most other genres, thereby requiring more headroom.

rd

[harryk]

As I earlier mentioned, I made a 250-300 W tube bass head with 4xKT-120 tubes. They sound pretty closely to KT88/6550. I made amp with UL and OT primary appr. 1 kohm. KT-120 is a pretty new tube but takes less space in chassis than 6x6550 etc.

[RJ Guitars]

As I earlier mentioned, I made a 250-300 W tube bass head with 4xKT-120 tubes. They sound pretty closely to KT88/6550. I made amp with UL and OT primary appr. 1 kohm. KT-120 is a pretty new tube but takes less space in chassis than 6x6550 etc.

That might get loud... http://www.newsensor.com/ProductHighLig ... ProId=1342

[bb5000]

Hi,

I built the Weber AB200 kit early this year, 6 KT88's at 650 Vp , around 300 W..it's just awesome !

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[M Fowler]

That kit looks to be of higher quality and only six KT88's huh!

Thanks for posting the pictures can't figure why Weber site doesn't have photos available for all the kits.

Mark

[bb5000]

That kit looks to be of higher quality and only six KT88's huh!

Thanks for posting the pictures can't figure why Weber site doesn't have photos available for all the kits.

Mark

Yup, 6 KT88's with PI transformer (old style) and 1 EL34 that operates in class A as an interstage, 2 12AX7's in the preamp. Good headroom !
The tube retainers are not included with the kit, the knobs are custom, and I've changed a couple of pots and customized the power supply since the power transformer was a different model than the original. The kit seems to be out-of-stock now (and has been for the better part of 2010)..

[Atmospheric]

Delay lines for time aligning cabs... that is serious commitment to tone. I bet that it sounded fantastic and could knock down walls if need be.

Who did you used to tour with?

I have an early Thunderfunk head that I like quite a bit. Still trying to find the ideal cab to go with it.

yes.
My main touring rig was:
'96 Stingray musicman 4 string / '98 G&L 2500-custom 5 string (w/Bartolini active elec)/ '67 Fender P-bass / '79 Gibson RD Artist / '81 Fender Fretless Jazz bass (w/bartolini Active elec).
I seldom used FX pedals - Sansamp / ProCo Rat / Boss Flanger / Dunlop Bass Crybaby / ibanez delay
SWR 220 studio Preamp (first generation)
Korg Rackmount Tuner
(True bypass mod) Peavey Dual 15 band graphic LED eq - not inserted but a good light show
Avalon U5 - Di
Urie 1176LN compressor
BSS Delay lines for time aligning the cabinets
Crown K2 (1 SVT cab pr Ch.)
(4) SVT 810e (2) SVT215e
(all cables Canarie / switchcraft connectors)
The head room is amazing and every note can bloom without bottoming out or becoming muddy. Every note on the fret board is balanced and you can go from clean to mean and not loose any detail.

[sparrott]

Just wrapped up this bass project for a friend of mine. It was fun, needs some tweeking to get some more clean headroom....

It makes around 160 to 180 fairly clean and 250+ full clipping....

octal preamp -> 6l6GC -> Fender 300ps phase splitter transformer -> single pair push pull 4cx250 output tubes.

[RJ Guitars]

Sparrott,

Very cool, and welcome to TAG. You have apparently been at this for some time. Tell us more about that circuit, it's unlike anything I've seen around these parts. I'd like to learn more about your phase inverter and those output tubes.

If you don't mind sharing a schematic, I'd be greatly appreciative.

rj

[TUBEDUDE]

Wow, real transmitter tubes. nice forced air tower! The phase splitting transformer looks huge. How much power does it have to deliver to the grids?

[sparrott]

I don't have an electronic version of the schematic right not, but I will at some point. Architecture is similiar to a Fender 300ps, which is what the above mentioned Weber AB200 is loosely based on.

Circuit is roughly this:

6sl7 preamp ->
James tone stack (with selectable mid-boost) ->
6sl7 effects loop ->
6sn7 driver ->
6l6GC interstage transformer driver ->
4cx250 output stage.

Simple controls.

Gain, Bass, Treble, Effects Level, Master Volume for knobs.

Switches for Deep, Bright, 3 level Mid-boost (gives GK versus Fender versus SVT tones).

The interstage transformer is from a Fender 300PS and with a triode strapped 6L6 should be able to deliver 2 to 3 watts to the grids of the output tubes (which is all they can handle). It is a bit "conservative" on power since the plate voltage is "only" 850 to 900 volts. 4cx250 tubes typically run @ 1500v or higher in RF duty. But I didn't want to play in that realm. I am still tuning on a variable feedback level network.

[bb5000]

I built another Weber during the summer, the 6S100. I didn't order the kit from Weber this time, I just used the schematic. Transformers and choke are Dynaco's (the original for Sunn 100S), I manufactured the chassis, faceplate and amp cabinet in my small workshop.

The extra stuff:

- a LCD volt meter (like the AB200 has) for plate voltage/cathode current readings
- more filtering
- balanced line-out
- flyback voltage diode protection
- NTC thermistors against inrush current

The original Sunn 100S tone stack values are used, the amp puts out ~80 W,


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