Noob Bass Amp Build Need Input

[Ed_Chambley]

Since the only tube bass amp I know I like are old Ampegs, I am considering building one.  I really do not know much about them, but I have repaired a few.  I am looking at a quad of 6550 or KT88, but open for suggestions.  I have found that OT's are not plentiful and only see them in Mercury Magnetics.  They are expensive.  I have heard of using 100 watt JCM 800 OT, but I question this decision.

I am looking at about 200 watts and have looked at a few old Ampeg schematics, but I do not really know the differences.  Seems like that 72 has 4 power tubes, but what I am finding is 6 tubes which makes sense.  Bass amps have changed a lot since 1972 which is the only bass amp I have ever owned excluding fender bassmans.  If my memory serves it was a SVT blue with 8, 10's.  It had 4 inputs and some switches above the knobs.  Sounded really nice, but it may not with today's sounds.

What I am asking is if you were to build a tube bass amp, around 200 watts, what would you consider?
 

[PRR]

> if you were to build a tube bass amp, around 200 watts, what would you consider?

Tube preamp and a 400 watt store-bought transistor amp.

I understand the attraction of tube sound. And the robustness of a GOOD large tube amp. I used to haul 800 watts of the stuff around.

But my back never really healed. And somehow I got older. And today the guitarist makes so much noise, bass subtleties are lost.

Tube-amp parts ARE cheaper (in terms of gas, cigarettes, rent) than ever before. But a big tube amp is still a large project; and still prone to smoke violently. (I got those tube amps because a sixth caught fire.)

THAT's what I'd be thinking.

You are welcome to other thoughts. I know I won't stop thinking about big tube amps. But for gigging, I sure would turn to the devil's devices. Much lighter, and you can get a warranty.

[Ed_Chambley]

I am not a bass player, but I have played bass many times.  I have borrowed a SWR 700 working man and their SM-900 which has thermal problems.  The are very cool amps with the limiter and aurial enhancer.  I am probably having euphoric recall, but my memory tells me the old Ampeg I had sounded better.  Probably not in reality.  Right now I have a SWR readhead (borrowed) with 2 10's.  It is impressive.

What tube preamp to you favor?

[smackoj]

ed; I would agree with PRR on the SS power section. I only know of two cos. as of now that are building 300+ watt tube bass amps (prob more out there though). I'm sure that those two guys thought long and hard before they decided to build one of those.

In regards to the SS amps, I found a guy selling a 350 watt Ashdown bass amp on sqeabay as "needs repair" . It had been dropped and all that I found wrong with it was a vol. pot that was shorted because of the drop. I bought it for under a 100 and put about 4 bucks in parts in it. It's a great amp and worth hundreds more than I paid. You could also find dozens of high quality SS power amps for sale that need repair and should be "fairly" easy to repair because of the quality of the amps. Then, as PR said, build a nice tube pre and get busy blowin' out the bass notes!

 

[Willabe]

If you go with a SS PA, why not use the pre from a B15?

http://www.el34world.com/charts/Schematics/files/ampeg/Ampeg_B15N.pdf


            Brad     

[6G6]

Hey Ed,
PRR is, as always, exacly right, from a practical standpoint.
Since we are here talking about building tube amps, I can assume
that we have mostly moved on past practical , resonable, etc. 

You weren't imagining it, the SVT was and is a grreat sounding bass amp.
It's not something you want to build.

You can build a Sunn 2000S.
They are simple, sound good and the parts are all available.

If you do decide to go pre + SS power amp, the Alembic pre has been a mainstay for years.
It is nothing more than the normal channel pre of an AB 763.

...then you get to deal with coming up with a bass speaker cabinet.
One can of worms at a time.

[Ed_Chambley]

If you go with a SS PA, why not use the pre from a B15?

http://www.el34world.com/charts/Schematics/files/ampeg/Ampeg_B15N.pdf


            Brad     

Curve ball.  I like the idea of this and the ss/preamp idea.  I always could hit a curve tho.  Thanks for the input Brad.

[Ed_Chambley]

Hey Ed,
PRR is, as always, exacly right, from a practical standpoint.
Since we are here talking about building tube amps, I can assume
that we have mostly moved on past practical , resonable, etc. 

You weren't imagining it, the SVT was and is a grreat sounding bass amp.
It's not something you want to build.

You can build a Sunn 2000S.
They are simple, sound good and the parts are all available.

If you do decide to go pre + SS power amp, the Alembic pre has been a mainstay for years.
It is nothing more than the normal channel pre of an AB 763.

...then you get to deal with coming up with a bass speaker cabinet.
One can of worms at a time.

I do need this to be practical as this will be for my wife.  She plays bass and keys.  The cabinet is not that difficult, but wrong place to discuss. 

[Ed_Chambley]

OK, now for the dumb part.  I have some QSC and Crown amps.  More than I need for most gigs. 
You guys talking about a preamp feeding something like this? 

If so, it is the best idea as it will allow for different amps like practice, 100 watts or small room.  Decent size room I guess 400.  Big room, balanced line out with monitor.

SWR bass amps claim to be hybrid, but they have a single 12Ax7.  I have not looked at it close, but I don't think it really does anything.

I found this Alembic schematic.  It looks simple.  A little different than an AB763.  I would think the AB763 mid scoop may not be good for bass, but what do I know.  Might be great.  This will be interesting to do.  I know exactly what I want from guitar amps, but I need to get some education on bass tone.  I always liked Barry Oakley's tone.  I just need the basics and them I can tweak it to what she wants.  She is into Rush, Yes and progressive sounds like Dream Theater.  Right now she has an Ashdown 500 watt with a Goliath III cab, 4 ohms, 800 watt.  The cabinet weighs about 90lbs i would guess.

Whatever it turns out to be, I need it to be a combo but that is nothing more than using decking screws through the amp into the cabinet.

Thanks for the input folks.  Now what to do with that PT I've got.   I have a growing need for a 100 watt plexi.  Just started needing it.

[Willabe]

I found this Alembic schematic.  It looks simple.  A little different than an AB763.

They just added a bright shift switch and changed a few part values. They tweeked it to their liking.

Mid pot in the TS changed from 10K to 250K. No more scooped mid if you don't want/need it.


             Brad      

[Willabe]

I do need this to be practical as this will be for my wife.  She plays bass and keys.

She is into Rush, Yes and progressive sounds like Dream Theater.  Right now she has an Ashdown 500 watt with a Goliath III cab, 4 ohms, 800 watt.  

Wow Ed! Very nice. I don't recall you telling us this before.


           Brad      

[Ed_Chambley]

I do need this to be practical as this will be for my wife.  She plays bass and keys.

She is into Rush, Yes and progressive sounds like Dream Theater.  Right now she has an Ashdown 500 watt with a Goliath III cab, 4 ohms, 800 watt.  

Wow Ed! Very nice. I don't recall you telling us this before.


           Brad      

I haven't mentioned this I do not think.  Sort of strange,  really.  I am a chicken picker.  You should hear us play Trees by Rush.   No really, she is a player and not into the mechanics.  We play together often, but I have to play zepplin and things like that.  She says Country music bores her on bass, but likes to play piano and organ on country.  I like playing rock as well, but it is not my favorite.  She has a fairly good voice as well.  It is nice as I never hear "Can you turn that down".

[HotBluePlates]

I tend to agree with PRR. And from what you're describing of your wife's playing and preferences, she'd probably be plenty happy with a SS amp.

A friend of mine when I lived in Nashville played gigs with some small solid-state amp head (maybe SWR, maybe another brand) and a Hartke 4x10 cab, and you could feel his bass lines punch you in the chest as you walked down the sidewalk leading up to the club he was playing. The high power and tight damping of the speakers punched through, and you could easily hear every note he was playing clearly.

A different friend had an Ampeg B-15N. Great sounding amp, very round but I don't recall it having the same sort of punch. Would be perfect for Motown-style playing where you feel the bass but aren't conscious of distinct bass lines unless the arrangement leaves space to hear them.

I also repaired a 6146-equipped SVT for yet another friend while I was there. That amp head was brutally heavy, and of course the 8x10 cabinet is a pain to transport unless you have a big truck and someone else to do the lifting for you.

It just seems like if you need a bass amp to have solid-state-like tight, fast response, ample power reserve and tight damping of the speakers, you're better off just using solid-state than trying to build a crazy-big tube amp that you try to force into behaving in a solid-state fashion.

Sidebar: Also note the Alembic is basically a Fender preamp with some extra tweaks. Never did understand why bass players thought Alembic was something special, and it is funny they basically built Fender preamps which were then plugged into solid-state power amps. You could experiment with either the Fender approach or the Ampeg approach in your preamps (Ampeg typically used James tone circuits with a little bit different response).

[PRR]

> I need it to be a combo

Bass waves are BIG.

To get the air to shake with bass, you either need a BIG amp or BIG speakers.

(Or both.)

"Usually" this leads to a 2-part construction, because otherwise it's too much for your roadies.

> this will be for my wife

I have a niece could probably roadie a combo DC300 and two-15" box. But even she would break-out the saw after the first gig.

I sure would not screw a 200-watt tube amp to any bass speaker worthy of that kind of power.

You sure your bassist really cares tube or transistor? Most don't. Others keep the old SVT in the garage and carry the G-K or SWR or Hartke to shows-- after the 3rd drink, the audience sure doesn't know the difference.

> she has an Ashdown 500 watt with a Goliath III cab, 4 ohms, 800 watt.

Does it suck? Back in the day, we woulda creamed our jeans with a rig like that.

> an Ampeg B-15N

Great amp; but won't do Yes in any venue larger than a cellar. Roundabout is a lot about the running bass-stomp, little of Yes is bassless. I imagine in the early years, Yes had trouble getting a live sound in large rooms which compared to what was on vinyl. Big _reliable_ transistor amps (and piles of speakers) was the answer.

> having euphoric recall, but my memory tells me the old Ampeg I had sounded better.

I think we had better drugs then. Even the beer was better (my beer is Rheingold).

.

[Ed_Chambley]

> I need it to be a combo

Bass waves are BIG.

To get the air to shake with bass, you either need a BIG amp or BIG speakers.

(Or both.)

"Usually" this leads to a 2-part construction, because otherwise it's too much for your roadies.

> this will be for my wife

I have a niece could probably roadie a combo DC300 and two-15" box. But even she would break-out the saw after the first gig.

I sure would not screw a 200-watt tube amp to any bass speaker worthy of that kind of power.

You sure your bassist really cares tube or transistor? Most don't. Others keep the old SVT in the garage and carry the G-K or SWR or Hartke to shows-- after the 3rd drink, the audience sure doesn't know the difference.

> she has an Ashdown 500 watt with a Goliath III cab, 4 ohms, 800 watt.

Does it suck? Back in the day, we woulda creamed our jeans with a rig like that.

> an Ampeg B-15N

Great amp; but won't do Yes in any venue larger than a cellar. Roundabout is a lot about the running bass-stomp, little of Yes is bassless. I imagine in the early years, Yes had trouble getting a live sound in large rooms which compared to what was on vinyl. Big _reliable_ transistor amps (and piles of speakers) was the answer.

> having euphoric recall, but my memory tells me the old Ampeg I had sounded better.

I think we had better drugs then. Even the beer was better (my beer is Rheingold).

.

The Ashdown and cab are nice.  Very good.  It will be kept as well.  Hauling is the problem and it stays at the church most of the time.

I was just kidding about screwing an amp down on the cabinet.  I have a rack case already.  What I want to do is put together 3 pieces to move.  A Rack and 2, 2-10's cabinets.  Then all 3 pieces will weigh about 35lbs each.  In a lot of cases you would only need one speaker cab if you have a line out.

This is why I was thinking a simple head.

[6G6]

OK, try a 2 channel pre.
B15 on one side
AB 763 (or variation)
on the other.
Add an AB box
and run it to the SS power amp of your choice.

The reason the Alembic was such a big deal was that
it would drive a DC 300A, which weighed 45 pounds
and meant not having to move an 85 pound SVT.

Would till sound as good today, but there are any number of
10-20 pound power amps that can put out more power, now.

[Ed_Chambley]

OK, try a 2 channel pre.
B15 on one side
AB 763 (or variation)
on the other.
Add an AB box
and run it to the SS power amp of your choice.

The reason the Alembic was such a big deal was that
it would drive a DC 300A, which weighed 45 pounds
and meant not having to move an 85 pound SVT.

Would till sound as good today, but there are any number of
10-20 pound power amps that can put out more power, now.

You read my mind.  If I cannot decide on one, do both, right!

[teisco88]

Hey, guys:

I have been playing guitar for 50 years, bass for 45 and building amps for about 40.  During that time SO much has changed.  40 years ago, you needed a large bass amplifier in order to be heard.  Heck, 20 years ago you still needed such an amp.  I would have gone out with as much as 500 watts of bass amplifications, and a couple of 6 x 8 cabinets in order to fill a venue with bass energy.

Today, PA systems are so good that it's better to think "what sounds best?" and let the PA take care of filling the room.  The warmth of a B15n (if that's your cup of tea) is quite practical these days.  A Sunn 200S amp would be a great build and the 60 watts it puts out would be perfect for stage volume.  The 2 x 15 cabinet it came with sounded great and put out lots of sound. 

Today, it is very practical to consider building one of those amps and using them in _any_ venue--given the reality of modern public address systems.