Power Amp Pre-Amp Combos?

[srxplayer]

I use a BBE BMax-T / QSC GX5 combo. I can give a little insight into using this set up. Of course the interpretation of the tone out of this thing is my personal opinion/taste.

I love the tone of the BMax-T. It's warm and tubey but it doesn't overdrive like you would expect a tube preamp would. Even with the gain dimed it doesn't overdrive much at all. I feed my Sansamp into front end for overdrive is I need it.

The EQ is passive. Bass and Treble are boost only and mids are cut only. It's a typical Fender style tone stack. Once past 4 on the treble and bass the boost is minimal. There is a semi-parametric mid that works well but it effects the the bass and treble slightly. The mid shift works well adjusting to rooms.

It has a built in soft knee compressor that works well and a built
in Sonic Maximizer that I like. I use it like another EQ. The S.M. technology is debated on TB but I like the feature and I use it all the time so I have drank the cool aid on the S.M.

The negative side of this preamp can be the passive EQ and it's limited boost. Depending on how you approach EQ and what your needs are that could a big negative. If you want lots of overdrive you won't get that either. The last negative (again depending on your needs) is the D.I. The Bmax was originally designed as a recording preamp. It has a Jenson D.I. it sounds awesome on recordings but it does not have a separate output level. The D.I. output is determined by the master volume. That may be a negative to you. I use my Sansamp BDDI for a direct out or a Radial J48. A direct out level control on the Bmax would be nice.

I have used my BMax with several different amps and never heard any difference in tone. The only difference was headroom depending on the amount of power the amp had.

Hope this helps.

[Got2SadowskyNYC]

Chucko, Crown would disagree with you're opinion on Dampening factor. I don't think they sell one with less than a 10,000 rating now.

You can really hear a difference. I was really surpised and I was useing a K1 with a lowly 3,000 rating.

By comparison, most bass amps are 500.

[mjac28]

Get a Meatsmoke pre and pair it with anything and you will be blown away they are on sale til the end of the year.

[chucko58]

Pulled from Crown's XTI 2 series data sheet: "Damping factor 20 Hz to 1 kHz: > 500"

Note that Crown doesn't mention the load impedance at which DF was measured.

I'm not going to argue with what someone else hears. I'm just skeptical that damping factor was the reason for the difference you heard. And I maintain that the speaker cable is a critical contributor to the DF in actual use, and usually swamps the amp's contribution.

For those who aren't familiar with damping factor, check out the Wikipedia article.

[BassmanPaul]

I'll agree with the recommendation for the Carvin DCM series power amps. i'm using the 1000L in my main rig that I've found to be wonderful. Using it i note no difference in "feel" from the lead sleds it replaced and I can lift the rack case with two fingers.

Sizing the power amp is important. You have to bear in mind what your speaker system needs and can handle. If you have one cabinet you'll need to run it from one channel of the amp or run in bridge which is something I don't recommend. I run a pair of cabinets and run one from each channel so my needs are somewhat different.

Pre-amps can be as simple as an ART TubeMP series if you have EQ on your instrument. The ART Tube Channel 259 is a very nice pre if you can find one used. The Alembics and others use the "Fender" tone stack I dislike intensely but it is a personal preference.

[topcat2069]

My Fave Pre is the Peavey Max Bass Preamp... discontinued but I still have one... I use it in my studio now (the Tube tends to fall out) but with any power amp it's a killer head !

[vgbob]

Originally Posted by CL400Peavey

To the OP, there are a ton of really nice power amps out there. One spec that is kind of a mis-label but very important is "sensitivity". This is the voltage that is needed to fully drive the amp. So lower sensitivity is better in the case of power amps. Make sure what ever pre amp you choose has enough guts to drive what ever power amp you choose. If not you may end up feeling a bit under powered regardless of your amp's rating.

This is very true. In the past I have tried to use a power amp with a pre that did not supply the voltage needed to reach a
decent volume. Not a defect in either of the units, just that they weren't correctly matched. And once you have them, you just can't make an adjustment to fix it. Although I do believe there are some power amps with a selectable sensitivity.

[Downunderwonder]

Originally Posted by nanymoa

I have a Crown XTI amp which I use for PA, soon i think to couple it with a Joemeek SixQ preamplifier to use as pre+amp combo for my basses. What do you think of that pre? Anyone uses it?

I've got its baby brother 3Q optical compressor DI pre. Nice bit of gear. I haven't tried it as a bass pre but I expect it would be sweet clean and trying to get grind out of it would be futile. The sixQ should make a good parametric.

[Tuned]

For bass guitar purposes I would argue that a lower damping factor would be favorable. It lets the speaker add more of its flavor. Tube amps have very low damping factors, like 10-20, thanks to the output transformers.

I wouldn't recommend a mic preamp for bass unless it had a tunable HPF. All bass preamps have a ~30Hz HPF to protect the speakers. I can get away with fretless using an EQ pedal for a preamp, but with fretted the cones really jump unlike when playing fretted through my SVP-CL, which has no shortage of low end. If a mic preamp has a fixed HPF it will be too high, 75-100Hz.

[Foz]

Finding the right preamp for your tastes is likely to be a life-long challenge. I've cycled through 5 or 6 already.

+1

Currently loving this one...

NAD - ART Pro Channel II

Can't be beat for the $ - but it needs a swap to better tubes and make sure the ground screw on the main board is tight.

Waiting for delivery on this one...

http://www.talkbass.com/forum/f15/**...ne-***-926928/

Good luck in your search!

[Codger]

Originally Posted by chucko58

Pulled from Crown's XTI 2 series data sheet: "Damping factor 20 Hz to 1 kHz: > 500"

Note that Crown doesn't mention the load impedance at which DF was measured.

I'm not going to argue with what someone else hears. I'm just skeptical that damping factor was the reason for the difference you heard. And I maintain that the speaker cable is a critical contributor to the DF in actual use, and usually swamps the amp's contribution.

For those who aren't familiar with damping factor, check out the Wikipedia article.

In the referenced wiki article:

Effect of voice coil resistance

This is the major factor in limiting the amount of damping that can be achieved electrically, because its value is larger (say between 4 and 8 Ω, typically) than any other resistance in the output circuitry of an amplifier that does not use an output transformer (nearly every solid-state amplifier on the mass market).

A loud speaker's flyback current is not dissipated only through the amplifier output circuit, but also through the internal resistance in the speaker itself.

Even if the resistance of the speaker cable and of the amplifier is 0 Ω, the speaker still faces the resistance of its own voice coil wire.

Therefore, damping factor values above 50 or so are not meaningfully different from 50. For higher values of speaker damping than about 50, actual speaker damping no longer increases in any way that can be confirmed by a double-blind A/B listening test, or measured.

[Tuned]

That passage does not explain why damping factors over 50 are no better than 50, apart from the blind A/B test. Was that test done with just a pair of speakers, where damping factor is of little consequence, or was it done with a room full of cranked powered PA speakers?

[seamonkey]

It would be very unlikely that differences heard between SS amps had anything to do with their DF. These new breeds of power amps with DSP have Gain and EQ on them that can even out any differences.

[Codger]

Originally Posted by Tuned

That passage does not explain why damping factors over 50 are no better than 50, apart from the blind A/B test. Was that test done with just a pair of speakers, where damping factor is of little consequence, or was it done with a room full of cranked powered PA speakers?

This waaay off topic but...

It has to do with the effect that the various system electrical resistances have on the system Q. And of the system electrical resistances Re, the voice coil resistance is dominant. All of the electrical resistances external to the speaker, i.e. amplifier output resistance (DF), wires, connectors, inductors, all can be summed with Re in the system model.

Consider two systems, identical except for the amplifier: Amp1 has a DF of infinity, Amp2 with a DF of 50. Amp1 output resistance is 0 ohm, Amp2's is 0.16 ohm (8 ohm ref). The two systems are equivalent except that system 2 has an Re that is 160 mohm greater than in system 1.

For an Eminence 3015, Re would increase from 5.31 ohm to 5.46 ohm. That is a 3% increase. I doubt Eminence would sign up to a 3% tolerance on their drivers.

Moreover, run two WinISD simulations using the same T/S params for both, but where the second has Re increased by 160 mohm. I tried it on a 3015LF, 3ft^3 @ 45Hz. The two traces, one for a system with a DF of infinity and the other with a DF of 50 virtually overlapped.

I suspect the "50" in the wiki article was just a number that produced a reasonably insignificant result for practical cases.

Edit: WinISD, not necessary to do two models. It has a box for adding series resistance.

[wcriley]

If having a damping factor in the 4 to 5 digit range is so important for low frequency reproduction, why do so many audiophiles like the sound of tube power amps?

[Project7Bass]

Thanks for all the feedback. To answer one question...I was considering doing this because I wanted to experiment with something different. No real motive behind it other than that. I like be comfortable with as many aspects of gear as I can. So it would be more of a learning experience for me. Got a lot of great info from all the posts. I'm gonna check out some preamps first I think. Then pair it with a power amp. Leaning towards the Peavey gear. Seems to be a solid performer for the money.

[NOVAX]

I'm rocking an ISP Bass Vector 15 (Bowlus approved) and I've cut out the power amp middle man. Now the colours and flavours of the basses and the preamps, compressors and equalizers come through with stunning clarity.
Demeter HBP-1
Groove Tubes studio bass pre
Ampeg SVT-IIP
Peavey Max
BBE Bmax
Joemeek SixQ
Universal Audio LA-610
Tech 21 Bass Driver
MXR M-80
DBX 160A
DBX 166XL
Boss, DOD, Ibanez stombox eq's and comps

[Downunderwonder]

Damping factor? Plug it in and play it. What power amp has anyone ever sent back because it didn't have good damping factor?

You need matching input sensitivity from the amp for your preamp of choice. Pick a preamp and see what it needs from an amp.

[popgadget]

I had a disappointing experience with a Crown XTI 1002. When it ran out of power it made some awful noises, even with the limiters set.
However the 2002 does a great job. I have a few preamps that I like, my current favorite is the Demeter HBP1. Waiting in the wings are An Alembic and Yamaha. All are good, but at the moment the Demeter is my fave.

[chadds]

Originally Posted by popgadget

I had a disappointing experience with a Crown XTI 1002. When it ran out of power it made some awful noises, even with the limiters set.
However the 2002 does a great job. I have a few preamps that I like, my current favorite is the Demeter HBP1. Waiting in the wings are An Alembic and Yamaha. All are good, but at the moment the Demeter is my fave.

SS power amps make ugly when they distort at the end of their watt limits. It's quite surprising to folks who grew up on tube amps or integrated SS amps that reach their limits differently.