Needing to build, mod or buy a bass amp...suggestions on a postcard please!

[Jennings]

I've got a potential project seed forming in my head, so figured I'd declare open season and post here for your input and advice...

...I've just started playing bass more (been a six-stringer up until now!) and my new love affair is a Gibson SG Bass that I have tweaked by drilling a new jack hole, moving the Vol, Vol, Tone and using the now vacant hole by the pick guard to mount a varitone.  Replaced the tone cap with a PIO, the Gibbo bridge with a Hipshot, and the strings are 45 - 105 flats.  I'm still toying what to do about the TB neck pickup.  However I have christened the thing "Spirit of EB3"!  Loving the bass...now I need an amp!

I'm looking to either build something, or modify something, to plug my beast into.  I mostly play at home, jam with friends and do small gigs...guitar wise I'm usually OK with my home built 18w and AC30 style amps, so that gives you an idea of the volume.  I was guessing that 50 - 100w maybe would therefore be OK bass wise?  I also envisaged the amp would either be a compact head/cab or a combo for portability and ease of fitting into the home...probably a 2x10, a 1x12, or even a hybrid two speaker cab with one 10 and one 12 in it.

OK...so what do you folks think?  I'm open to any ideas or suggestions, from the amp style, circuit or design, to speaker and cab choice.  Or even turn me on to something that might already exist that seems to fit the bill!

[sluckey]

I'm thinking Ampeg B15 (several choices between fixed or cathode bias) or Sunn 200S, Solaro, Sonic, Sonora (all same circuit just different iron, output tubes, and speaker cab). The Ampeg is 30 to 40 watts and the Sunn is 40 to 60 watts. Either circuit is simple and easy to build and would work well in a small to medium size venue. A 1x15 would be my choice.

BTW, my first build ever back in '68 was the Sunn Sorado head with a 2x15 cab. I played country bass (and sometimes guitar) with it for about 4 years then sold it to a friend to use for PA and music in a medium size skating rink. It was still going strong 20 years later.

[Ken Moon]

I've tried my hand at building a few bass amps, but never have been satisfied with the results.

I have an Epi EB-3 and access to a Precision Bass as instruments.

The problem is a mudiness and lack of "snap" with my tube attempts, when compared to off-the-shelf SS bass amps. I tried a $350 300w Acoustic brand SS head through the matching 1x15 cab with a horn, and it just kicked my amps' asses, whether using the same cab or an old 4x10 bass cab I have. I also tried an old blackface Bassman amp, and it sounded muddy to me too.

Anybody else notice the same thing?

[kagliostro]

If you like the idea of an Ampeg B15, here you can find good documentation for a derived amp (Layout - chassis measures - etc..)

http://ctgelectronics.weebly.com/custom-amplifier---fcn-51-b.html

and here an enanced version

http://ctgelectronics.weebly.com/custom-amplifier---fcbn-51b.html

K

[Jennings]

It's like sluckey and kagliostro can tap into my mind, and my valve boxes!  I know very little about bass valve designs, but the B15 idea looks to not only be the right power & size, but also I have a load of 6SL7 and 6L6 tubes sat about doing absolutely nothing, so it would be an idea supply for the amp.  Straightforward looking build too.  Looks like a good contender.  Anyone know whether anyone builds a suitable pre-punched chassis?  That'll be the tricky part for me to do at home.

Oh, and thought I'd mention that I have a little 1 watt Torres Tiny Tone Marshall style amp with a Jensen P10R that I love my guitars through, but actually it makes a great little friend for the bass too...which made me wonder about using some alnico 10s somewhere for bass.

[Ed_Chambley]

I built a 2, 12 Bass Cab suing Eminence Neo magnets and atop a head.  The head is basically a Sunn/Dynaco, UL OT.  P purchased the tranny set Triode sells.
Link: http://www.triodeelectronics.com/mk3trbuwfrch.html

The schematic attached.  I did use a Ef86 input and have zero micro-phonic problems.  With the KT120 output tubes over the KT88 allowed me to achieve a tighter bass.  I really like the pentode tone on Bass.  Great tube tone and outputs 76watts.  Great for practice or small club, but it gets lost on a large stage if the sound system is lacking.  It does not sound muddy at all.  However, it is ss rectified and voltages are very high.  So much so I really don't trust current production kt88.  I have a pair of Valve Art (Chinese) I ran in it for a good while and they held up.

The great thing about this build is it is very Guitar friendly and when cranked does a very hard crunch that chest beating.

The best Bass amp I built IMO is a Ampeg preamp B15 feeding an old Crown amp that is 800 watts at 4 ohm.  The neat thing about building just the preamp is you can use different PA's.

My wife is a bass player and likes these builds on a 4 string, but on her 5 and 6 string basses she has a SWR 700 and a Ashdown.  Even the low B is not muddy, there is just not quite enough watts to make your eyeballs vibrate in their sockets.

[sluckey]

Couple of questions, are you planning a playing a five string bass with the B0, bottom string? OT selection very important.

I believe he said Gibson SG.

[kagliostro]

@ Ed_Chambley

Ciao Ed

I'm not able to open your schematic

nor using JSChem or Eagle (the two programs I've that opens .sch schematics)

Franco

[Jennings]

Thanks for the continued replies folks.  I don't seem to have a program which opens that schematic either though sadly Ed.  The Triode transformer set does look good though...price seems OK too, although I guess I'll have to add a bit for UK tax and shipping.  Actually I might also see whether Danbury (UK manufacturer which the likes of Marshall, Vox etc have used) have anything equivalent.  I've liked the sound of their Vox-types before.

I think the sound I'm after is something woody and rich.  Not muddy, but I'm not desperately trying to get the sort of modern P-bass/J-bass and SS amp treble snap or scooped tones.  I like a more organic and vintage feel to both my guitar and bass sounds.  That's why I was wondering about the alnico 10s as part of the speaker set up, as I have that kind of alnico stuff going on in the guitar amps I use, and the bass sounds great with the 1w amp and P10R.  I can get a fair bit of presence with the speaker response, plus the amp is geared for guitar so it's not mud heavy.  I've only got the SG Bass for now, so short scale and buckers, but I may expand a bit in the future.  However, as a 6-stringer and general bass Luddite, I have no idea when it comes to bass set ups really!  I'm not likely to go the 5 or 6 string bass route in the near future though...I'll probably be more the general 4 string groove type!

[John]

ExpressSCH is the program you need; free download, fairly easy to learn. Invaluable tool. :)


Ed, interesting circuit, nice and simple just like I like 'em. One question: what is the ||-> (1) over near your EF86?  It right at the 1000pf (bright?) cap at the bass pot.

[kagliostro]

Thanks Ed

I downloaded and installed ExpressPCB (ExpressSCH is in boundle) and now I'm able to open your schematic

Ciao

Franco

[Ed_Chambley]

ExpressSCH is the program you need; free download, fairly easy to learn. Invaluable tool. :)


Ed, interesting circuit, nice and simple just like I like 'em. One question: what is the ||-> (1) over near your EF86?  It right at the 1000pf (bright?) cap at the bass pot.

It is stray crap I failed to clean up.  That is the first time using Express and since it does not have copy and paste I was opening other things to copy from.  I was learning it because most of you guys use it.

I have attached a revised version.  I am much better with Visio and Illustrator.

Here is the major question I have with the amp design.  It is stolen from DR Z Route 66 with some cap sizes enlarged.  Merlin's book and many other say EF86 is a poor choice for tonestacks and UL designs are stiff for guitar.

Well this tonestack is extremely responsive, so much I have used it on SE builds with great results using the 6sj7.  If you increase the treble using a guitar you begin to get distortion.  I have also used the same preamp, PI and used 6V6 which fit perfectly in a 5E3 chassis with great results, but needed some NFB.  Of course there is no need for a master volume and the tone is very similar Octal preamp using a EF86 pentode.

I was hesitant to build it because so many said the EF86 is a poor selection for tonestack, but Dr Z disagrees and now I do as well.

Sorry for the error, that is the first one I have ever made.

[skeezbo]

have you considered  building a Showman? I had both a blackface showman 1x15 and a B-15. I never took the Ampeg out. Not enough usable headroom. I also used an old Bassman 100 with a 2x12 cab with Eminence neo speakers. Very nice old school tone. The B-15 was a great recording amp, but I think you might need the 4 power tubes to get enough clean volume for a gig.

[TubeGeek]

Ampeg B-15 kit:  http://www.trinityamps.com/Product_Kits_Triptop.htm

[DummyLoad]

ed, the EF86 is wired as a triode. not sure that's what you want but g2 and anode are tied together... i edited the schema. see attached. 


i ran a sim and made mods to PI; up B+ to PI, changed PI tube, also made PPIMV mod, NFB mod.


--pete


 

[Ed_Chambley]

ed, the EF86 is wired as a triode. not sure that's what you want but g2 and anode are tied together... i edited the schema. see attached. 


i ran a sim and made mods to PI; up B+ to PI, changed PI tube, also made PPIMV mod, NFB mod.


--pete

That was an error on the ef86. These changes make it more bass friendly. I have tried an at7 in the pi, but did not change any values.


What changes does the sim show in making these revisions?y

[DummyLoad]

increased output swing, more symmetrical output, with at7 slightly more gain into ~100k load.


not a fan of the PPIMV. if i have one, it's full up or so near to maximum to not matter.


--pete

[tompagan123]

I purchased an old  Fender Super Twin 2x12 combo amp to convert into a  bass amp.  It has 6 x  6L6, 180 W,  4 band RLC active eq, great sounding direct out for recording / sound reinforcement.  We put it into a head cab.  I'm using the 2 x 12 CTS / Fender Special Design speakers in an old Ampeg VT22 extension cab;  the old compo amp cabinet is not finger jointed and was starting to fail, so good riddance to it.   The rig sounds reminiscent of a smaller SVT.   It's NOT light in weigh, super loud or super efficient, but it does keep up with a band, sounds really nice, records *great* and has tons of vibe.  ;-). 

[Ritchie200]

+1 for Ed.  The KT120 will have loads of headroom.  UL will be perfect for bass.  UL to stiff for guitar?!?!?!?! Maybe the Fender version   Marshall got a UL version quite right IMHO....

Jim

[kagliostro]

Some are these







K

[Ritchie200]

Yup, Kagliostro got it!  The Major is UL.  I would encourage you to listen to any Deep Purple MKII albums as well as Made In Japan for a reference.  Especially the Roger Glover bass solo on Pictures of Home.  Here is a video showing Roger's one Major head pushing two 4x15 and two 2x15 reflexes.  Notice the cone movement.  I like the tone.  I saw them live back in '72 and Roger's tone was fantastic.

Here is another link about the cabinet and setup: http://el34world.com/Forum/index.php?topic=13247.0

Here is the video:

https://www.youtube.com/watch?v=7mCK05dgwgU

Pictures of Home:

! No longer available