Hello and hello,
I sure am enjoying the conversation! I've got very little DIY experience, (tweaks to my ST70) and some Pass Labs stuff, but I would like to build a smallish tube amp for my son's bass. He want some good warm tone. I do have access to a machine shop for the physical construction, but would probably not attempt trannies. Are there any suggestions for a relative first timer? Should I copy a known commercial amp?
Thanks,
Charles BL
I sure am enjoying the conversation! I've got very little DIY experience, (tweaks to my ST70) and some Pass Labs stuff, but I would like to build a smallish tube amp for my son's bass. He want some good warm tone. I do have access to a machine shop for the physical construction, but would probably not attempt trannies. Are there any suggestions for a relative first timer? Should I copy a known commercial amp?
Thanks,
Charles BL
how much power do you need?
once we get that done I can start rattling off some ideas
If you want <20w, we could probably put something decent together for cheap, especially if you can scrounge parts from the junk bin.
more power and we'd have to jump the cost some (mostly because of the larger output tranny required..)
once we get that done I can start rattling off some ideas
If you want <20w, we could probably put something decent together for cheap, especially if you can scrounge parts from the junk bin.
more power and we'd have to jump the cost some (mostly because of the larger output tranny required..)
I'm actually a jazz bass performance major....
I have a tubed '70 fender bassman that i really like, but tube amps tend to be for a more round, warm, retro sound. If you want slap'n'pop kind of bass playing, the amps i really enjoyed playing through were solid state: AMPEG, mesa boogie, SWR...coupled with a decent compressor, i think these were more suited to my playing style.
I suppose if it's just a practice amp, it doesnt matter much....but if you told me what style music, and what kind of bass he has, i could give you an ideal amp model and we could dig up the schematics.
I have a tubed '70 fender bassman that i really like, but tube amps tend to be for a more round, warm, retro sound. If you want slap'n'pop kind of bass playing, the amps i really enjoyed playing through were solid state: AMPEG, mesa boogie, SWR...coupled with a decent compressor, i think these were more suited to my playing style.
I suppose if it's just a practice amp, it doesnt matter much....but if you told me what style music, and what kind of bass he has, i could give you an ideal amp model and we could dig up the schematics.
WHAT HE SAID (Magnetmaz)...
Although, I have heard an amp with multiple pairs of 6550's built for bass (I think it was an ampeg). It had a good dynamic sound, even though it did lean toward the warm side.
What about a hybrid? Tube front end, solid state output stage. Could be the best of both worlds, if done right.
-NS
Although, I have heard an amp with multiple pairs of 6550's built for bass (I think it was an ampeg). It had a good dynamic sound, even though it did lean toward the warm side.
What about a hybrid? Tube front end, solid state output stage. Could be the best of both worlds, if done right.
-NS
I could be mistaken, but Ashdown (think that's their name) have gained much fame in the last couple years for building outstanding amps and cabinets. They are big bucks, though. I believe they are tube front end and solid state back end, ....they have huge analog VU meters on the display, and they look like something out of a WWII bomber.
I've played them, and they were a 'best of both worlds' sort of solution....but i dismissed them as too expensive.
I've played them, and they were a 'best of both worlds' sort of solution....but i dismissed them as too expensive.
Alright...my knowledge of electronics is pretty limited to what i've learned on this board in the last month. I'm not quite sure the difference between class B and A/B amp types, nor am i familiar then with what class a bass amp typically uses. Enlighten me, please...
as far as the question i CAN answer : i use a seperate, rack mount DBX 166 stereo comp/limiter/gate. I have my bass gear plugged into one channel for compression, and my Marshall full stack plugged into the other and am using it as a noise gate.
as far as the question i CAN answer : i use a seperate, rack mount DBX 166 stereo comp/limiter/gate. I have my bass gear plugged into one channel for compression, and my Marshall full stack plugged into the other and am using it as a noise gate.
Most solid-state bass amps are AB. There are although some people using the Crown K-type PA amplifiers together with a bass preamp.
Most bass (pre) amps have built-in limiters. I have even seen a schematic of an earlier Trace-Elliott bass combo where they used zener diodes in the feedback network of the power-amp section to achieve some kind of soft clipping !!
Regards
Charles
Thanks for the replies. I would have thought that a lot more manufacturers would switch to a "digital" type amp, but I know it wouldn't be good for tone.
As far as amp classes go, here's a basic run down-
It all has to do with how the output stage operates:
Class A- Output devices (tubes or transistors, or whatever) are on all the time- always conduct current.
These can use just 1 output device, or two (or more), pushing and pulling against each other. They will always be turned on and conducting though.
Class B- Uses two devices (or multiples of 2, in pairs). One device turns on and conducts for half of the wav, the other picks up the other half. This boosts efficiency. Because it is impossible to really match up the waveforms exactly, there is always a little overlap, where each device conducts a little more than half. This is called class AB (which, really all push pull amps that aren't class A are). Most people call the amps that are really close to being "perfect" b types b, and the ones that conduct a little more, class AB. I haven't ever seen a set-in-stone cutoff point for B to AB... maybe someone else can define that.
switching output stages- turn on and off at a high frequency to approximate the signal. when you filter the high frequency out, it averages out to an audio signal. Very efficient.
BTW, dbx compressors have always been my favorite...
Have you ever heard Doug Pinnick from King's X? he biamps, and runs the lows through a bass amp, and the highs through a fender guitar stack. Very unique sound.
-NS
As far as amp classes go, here's a basic run down-
It all has to do with how the output stage operates:
Class A- Output devices (tubes or transistors, or whatever) are on all the time- always conduct current.
These can use just 1 output device, or two (or more), pushing and pulling against each other. They will always be turned on and conducting though.
Class B- Uses two devices (or multiples of 2, in pairs). One device turns on and conducts for half of the wav, the other picks up the other half. This boosts efficiency. Because it is impossible to really match up the waveforms exactly, there is always a little overlap, where each device conducts a little more than half. This is called class AB (which, really all push pull amps that aren't class A are). Most people call the amps that are really close to being "perfect" b types b, and the ones that conduct a little more, class AB. I haven't ever seen a set-in-stone cutoff point for B to AB... maybe someone else can define that.
switching output stages- turn on and off at a high frequency to approximate the signal. when you filter the high frequency out, it averages out to an audio signal. Very efficient.
BTW, dbx compressors have always been my favorite...
Have you ever heard Doug Pinnick from King's X? he biamps, and runs the lows through a bass amp, and the highs through a fender guitar stack. Very unique sound.
-NS
Magnetmaz,
He's playing Jazz, Ska? grunge?... He goes to sleep listening to Miles Davis, does school performances in the Jazz combo, does club gigs (just starting) in ska? He plays a fender jazz bass soon to have a Warmoth fretless neck. He'll probably use my Washburn w/active Duncan when he does'nt want the fretless sound. He say's he wants the tube sound, but I'm not entirely sure he identifies it correctly. However, I'm all for it.
Thanks
He's playing Jazz, Ska? grunge?... He goes to sleep listening to Miles Davis, does school performances in the Jazz combo, does club gigs (just starting) in ska? He plays a fender jazz bass soon to have a Warmoth fretless neck. He'll probably use my Washburn w/active Duncan when he does'nt want the fretless sound. He say's he wants the tube sound, but I'm not entirely sure he identifies it correctly. However, I'm all for it.
Thanks
Hi Charles
IMO a good compromise (which isn't actually one at all !) would be to build a decent tube- or hybrid- preamp which he can use with a weak amp now and also with a "paint-stripper" later on (don't forget to add a headphone output !).
In a bass-preamp I built 10 years ago I used a triode as the first stage (the rest was all op-amps). I could set the bias of the tube from the front-panel to get more k2. This gave some warmth to the tone of my fretless but was annoying with my fretted bass.
Regards
Charles
IMO a good compromise (which isn't actually one at all !) would be to build a decent tube- or hybrid- preamp which he can use with a weak amp now and also with a "paint-stripper" later on (don't forget to add a headphone output !).
In a bass-preamp I built 10 years ago I used a triode as the first stage (the rest was all op-amps). I could set the bias of the tube from the front-panel to get more k2. This gave some warmth to the tone of my fretless but was annoying with my fretted bass.
Regards
Charles
I would agree with that... it would be a good idea if you could seperate out the preamp and power amp. It makes your possibilites open up a lot.
You could build a solid state P-P amp, mosfet or IC, cheaper than a tube amp, and it would put out much more power. A tube preamp would be nice. Make it with a pre/post gain setup so you can get a very clean or a slightly dirty sound. One thing that would be beneficial with a solid state preamp is that you could easily implement active EQ without needing another power supply... passive tone controls don't do much, in my experience. By seperating out the amp from the preamp, you could also easily insert an outboard EQ, or later build an active cross over and use the wimpy amp for the highs, and build a bigger amp for a future bass cabinet. Just some ideas.
-NS
You could build a solid state P-P amp, mosfet or IC, cheaper than a tube amp, and it would put out much more power. A tube preamp would be nice. Make it with a pre/post gain setup so you can get a very clean or a slightly dirty sound. One thing that would be beneficial with a solid state preamp is that you could easily implement active EQ without needing another power supply... passive tone controls don't do much, in my experience. By seperating out the amp from the preamp, you could also easily insert an outboard EQ, or later build an active cross over and use the wimpy amp for the highs, and build a bigger amp for a future bass cabinet. Just some ideas.
-NS
Fender preamp link
http://www.taosnet.com/f10/fender_pre.htm
This is close to what the Alembic f2b is/was and you may find the Alembic scheme online (it has been around and I'm trying to find it) You could use a bridged LM3886 amp (about 160w into 8) in an "active enclosue" with a single 15/12 or 10. I've rebuilt Polytone amps with the 2x3886 amp and they work amazingly well. Add the Fender preamp on top as a head, you can build more powered speakers if you need more level. This would be super cheap to build and sound great.
http://www.taosnet.com/f10/fender_pre.htm
This is close to what the Alembic f2b is/was and you may find the Alembic scheme online (it has been around and I'm trying to find it) You could use a bridged LM3886 amp (about 160w into 8) in an "active enclosue" with a single 15/12 or 10. I've rebuilt Polytone amps with the 2x3886 amp and they work amazingly well. Add the Fender preamp on top as a head, you can build more powered speakers if you need more level. This would be super cheap to build and sound great.
I would recommend using a regulated supply for the preamp stage. It should make it easier to get the low frequency roll off down to an approprate cut off point without motorboating. You may want to watch out for guitar amp designs as they often have a very high low frequency rolloff, which you don't want for bass. If it were me, I would consider using a mosfet front end (possibly jfet input stage for lower noise). Put a tube somewhere in the gain path for a little character (split the gain path off to the tube, and make it so you can blend it in... that would be cool). You could probably get away with running it at a low voltage, since you want the harmonic distortion in this case, so you could use the same power supply as the mosfets.
As far as IC amps go.... yeah, it's easy and cheap, but when they "hit the wall", it's really ugly. And, they WILL hit the wall often with a bass guitar! It require a lot of power. A soft clipping circuit would help things out tremendously on a lower powered amp. Why not an A/B Mosfet push pull? adapt one of Aussieamps designs, or something similar. To build it right either way, the majority of the $$$ will be spent on the power supply, so why bother with IC amps?
It all depends on what you want to do with it, of course. If it's a practice amp, and you won't be competing with loud guitars, drums, etc. or in big rooms, then the criteria changes.
Oh, and BTW, consider using multiple drivers to increase the efficiency- free SPL (kind of).
Hope this helps.
-NS
As far as IC amps go.... yeah, it's easy and cheap, but when they "hit the wall", it's really ugly. And, they WILL hit the wall often with a bass guitar! It require a lot of power. A soft clipping circuit would help things out tremendously on a lower powered amp. Why not an A/B Mosfet push pull? adapt one of Aussieamps designs, or something similar. To build it right either way, the majority of the $$$ will be spent on the power supply, so why bother with IC amps?
It all depends on what you want to do with it, of course. If it's a practice amp, and you won't be competing with loud guitars, drums, etc. or in big rooms, then the criteria changes.
Oh, and BTW, consider using multiple drivers to increase the efficiency- free SPL (kind of).
Hope this helps.
-NS
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