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riksylvania
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Joined: 21 Jan 2003
Posts: 203
Location: Summerhill, PA
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 Posted: Tuesday Mar 06, 2012 |
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Hey bass players,
I was told that it can be bad/ dangerous to bridge a power amp when it's being used as a bass amp because of a threat of square waves ruining the amp. Do you guys (that use preamp/ power amp rigs) bridge your amps? I have a Crest amp that I have been running only through one side because of the small room that I practice in, but I will most likely bridge it in for shows.
Also, don't one of you guys use a BBE Max preamp? I was looking at new preamps. What do you think of it? |
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lonewolf
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Joined: 25 Sep 2003
Posts: 6249
Location: Anywhere, Earth
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| Posted: Tuesday Mar 06, 2012 |
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| riksylvania wrote: | Hey bass players,
I was told that it can be bad/ dangerous to bridge a power amp when it's being used as a bass amp because of a threat of square waves ruining the amp. Do you guys (that use preamp/ power amp rigs) bridge your amps? I have a Crest amp that I have been running only through one side because of the small room that I practice in, but I will most likely bridge it in for shows.
Also, don't one of you guys use a BBE Max preamp? I was looking at new preamps. What do you think of it? |
Do you mean that a threat of clipping could blow out the speakers? Square waves per se will not ruin an amp (otherwise, you'd have a problem playing analog synthesizers), but clipping will blow out speakers. Clipping is kind of like a square wave as the peaks of the signal are "clipped" off and appear flat.
The added headroom from bridging would actually help to prevent clipping at higher volume levels as long as you don't drive the amp too far. In the immortal words of Clint Eastwood: "A man's gotta know his limitations."
This is a case where a limiter between the preamp and power amp would be useful. (see the compressor thread).
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Last edited by lonewolf on Tuesday Mar 06, 2012; edited 1 time in total |
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313
Gold Member
Joined: 21 Feb 2003
Posts: 261
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| Posted: Tuesday Mar 06, 2012 |
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| riksylvania wrote: | Hey bass players,
I was told that it can be bad/ dangerous to bridge a power amp when it's being used as a bass amp because of a threat of square waves ruining the amp. Do you guys (that use preamp/ power amp rigs) bridge your amps? I have a Crest amp that I have been running only through one side because of the small room that I practice in, but I will most likely bridge it in for shows.
Also, don't one of you guys use a BBE Max preamp? I was looking at new preamps. What do you think of it? |
All that bridging will do is double your output voltage swing. That has nothing to do with generation of square waves. If you truly need the extra voltage swing to fully drive your cabs, bridging is fine (and is done by bassists). If not, that doubled voltage simply increases risk of damaging speakers - esp. for low impedance cabs.
Not sure if you have two cabinets, but if so you could just connect each cabinet to a separate channel and not worry about bridging.
Last edited by 313 on Tuesday Mar 06, 2012; edited 1 time in total |
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riksylvania
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Joined: 21 Jan 2003
Posts: 203
Location: Summerhill, PA
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| Posted: Tuesday Mar 06, 2012 |
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I always assumed that bass players bridged their power amps, and this kind of threw me for a loop when this guy told me this. Thanks, i just wanted to make sure that this person was full of it. I was talking about the amp being ruined, not the speakers. I have plenty of cab to allow the amp to be bridged, I just wanted to make sure I was being safe. It's a crest 660 or something like that with a Hartke Hydrive 8 10 cab (4 ohms).
Thanks, guys!
PS: What kind of preamps do you all use? |
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313
Gold Member
Joined: 21 Feb 2003
Posts: 261
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| Posted: Tuesday Mar 06, 2012 |
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| riksylvania wrote: | I always assumed that bass players bridged their power amps, and this kind of threw me for a loop when this guy told me this. Thanks, i just wanted to make sure that this person was full of it. I was talking about the amp being ruined, not the speakers. I have plenty of cab to allow the amp to be bridged, I just wanted to make sure I was being safe. It's a crest 660 or something like that with a Hartke Hydrive 8 10 cab (4 ohms).
Thanks, guys!
PS: What kind of preamps do you all use? |
I used a Fender TBP-1 in the past. Fantastic tube pre-amp. I think that both Sansamp and BBE both make pretty popular bass preamps also. |
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riksylvania
Gold Member
Joined: 21 Jan 2003
Posts: 203
Location: Summerhill, PA
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| Posted: Tuesday Mar 06, 2012 |
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| I heard that those Fenders and BBEs are good. I had this Carvin piece of junk that I am going to shoot in my back yard soon. It never worked right and sounded like garbage from day 1. I was also thinking about using an ART tube PreAmp. I've recorded bass extensively with them and they can be voiced very well for bass. Only down side about that is that I will need a separate EQ for it, which would mean a larger rack case. I use a very light compression, but it's not a necessity for my sound. |
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lonewolf
Diamond Member
Joined: 25 Sep 2003
Posts: 6249
Location: Anywhere, Earth
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| Posted: Tuesday Mar 06, 2012 |
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| 313 wrote: | | riksylvania wrote: | Hey bass players,
I was told that it can be bad/ dangerous to bridge a power amp when it's being used as a bass amp because of a threat of square waves ruining the amp. Do you guys (that use preamp/ power amp rigs) bridge your amps? I have a Crest amp that I have been running only through one side because of the small room that I practice in, but I will most likely bridge it in for shows.
Also, don't one of you guys use a BBE Max preamp? I was looking at new preamps. What do you think of it? |
All that bridging will do is double your output voltage swing. |
For linear power amps. For digital amps, the multiplier is the square root of two.
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bassist_25
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Joined: 09 Dec 2002
Posts: 6815
Location: Indiana
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| Posted: Tuesday Mar 06, 2012 |
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Bridging an amp will hurt the amp itself with a bass? Rik, I'm sorry to say that someone was trying to sell you some snake oil. That claim is even more asinine considering that some power amps have selectable 30hz low-pass filters. Why put a selectable low-pass filter in for an amp that can't even deal with those frequencies in the first place? I've bridged both QSC and Crown power amps as part of component bass rigs with great results. It's just like any other amp: Don't go lower than the minimum impedance load requirement, don't clip the amp or speakers, and you'll be fine.
I've used the solid-state version of the BBE Bmax for years. I've been using other amps for the past couple of years but keep the BBE as a backup. It's a great sounding unit and sound engineers seem to love it. I found it to be a consistent sounding preamp from room to room, and didn't require much EQing once set (which is a good thing, since it has an interactive EQ). The Sonic Maximizer made cheap cabinets sound good but actually worked against higher-end boxes. It has obscene amounts of high-end, so you'll never worry about not being present in the mix (of course, clank and fret noise can be problematic, even with good technique). The only thing I'd warn against is that the Bmaxes have a ton of gain, so it's easy to drive a sensitive power amp too hard.
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riksylvania
Gold Member
Joined: 21 Jan 2003
Posts: 203
Location: Summerhill, PA
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| Posted: Tuesday Mar 06, 2012 |
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| I did find that strange since I remembered that some of you dudes said that you did bridge them. Thanks for the input, fellers! |
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313
Gold Member
Joined: 21 Feb 2003
Posts: 261
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| Posted: Tuesday Mar 06, 2012 |
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| lonewolf wrote: | | 313 wrote: |
All that bridging will do is double your output voltage swing. |
For linear power amps. For digital amps, the multiplier is the square root of two. |
By "digital" I assume you are referring to the Class D power amps? If so, I see no inherent difference in the outputs of a Class D and a traditional power amp, whether bridged or not - and the bridged mode voltage output of the Class D amp should be double. Data on my Class D power amp support this assertion:
Crown XLS-1500 delivers 300W into 8 ohms single channel, and 1050 Watts into 8 ohm in bridged. |
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CMOR
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Joined: 04 Jun 2004
Posts: 367
Location: Right here.
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| Posted: Wednesday Mar 07, 2012 |
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Hey Dazzle, 
I'll chime in and agree with what the others have said. Don't worry about bridging a power amp.
As far as the BBE pre goes, I had one for about a year a few years back. Coupled it with a Mackie 1400i, running mono-bridged. Sounded good, but not quite right with my Acme LowB-4 II cab(one bada$$ m'er f'er of a powerhog). Paul pretty much nailed it with this quote:
| bassist_25 wrote: | | The Sonic Maximizer made cheap cabinets sound good but actually worked against higher-end boxes. It has obscene amounts of high-end, so you'll never worry about not being present in the mix (of course, clank and fret noise can be problematic, even with good technique). The only thing I'd warn against is that the Bmaxes have a ton of gain, so it's easy to drive a sensitive power amp too hard. |
I ended up dumping it to go G-K, then Mesa. May I recommend (and this hurts to say) an Ampeg SVP-PRO. From what you said you were going for sound-wise the other week, I think it would give you what you're looking for and a ton of flexibilty. They can hard to find at a good price, be warned.
Keep us updated, I'm looking forward to hearing you lay down some thick grooves.
Steve
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riksylvania
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Joined: 21 Jan 2003
Posts: 203
Location: Summerhill, PA
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| Posted: Wednesday Mar 07, 2012 |
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CMOR,
I am still in negotiations for 2 all tube heads in 2 undisclosed locations, both a 100 watt version for the studio and a 300 watt version to gig with , but I am still looking for a pre to round out my current rig. I think that playing with Stillwater will still require a cleaner sound than those tube heads are going to give me. I need to catch your band to hear that Mesa that you have been using! The Hartke cab has definitely made a cleaner sounding rig. (better for the upright, although the 2 15 Edens with my jazz bass sounded GREAT in those Stax and Motown songs)
It will be interesting playing bass out again, it's been about ten years since I've been the bass player in a band. It's still my first instrument and first love though for sure. Last year I retired the bass I used from 1995, Japanese Fender MB-4. This whole power amp/ pre setup is going to be fun. So many combinations possible! My last good rig was a 70s Acoustic head and Sunn 2 15 cab, so this whole "clean low end" thing is all new. |
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bassist_25
Senior Member
Joined: 09 Dec 2002
Posts: 6815
Location: Indiana
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| Posted: Monday Mar 12, 2012 |
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| CMOR wrote: |
May I recommend (and this hurts to say) an Ampeg SVP-PRO. |
Oh no, Steve! I'm also really digging on those micro PF amps Ampeg has out. Are we gonna become Ampeg guys?! 
Rik, check out this site:
http://basstasters.com/preamps/
It's obviously not the same as playing through each preamp yourself, but it will give you somewhat of an idea of the different flavors.
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riksylvania
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Joined: 21 Jan 2003
Posts: 203
Location: Summerhill, PA
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| Posted: Tuesday Mar 13, 2012 |
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Very cool! Thanks, Paul.
The 100 watt head i've been looking at is an ampeg, so we'll see if I become a convert over it.  |
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bassist_25
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Joined: 09 Dec 2002
Posts: 6815
Location: Indiana
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| Posted: Tuesday Mar 13, 2012 |
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Ahh, is it a V4 Rik? Those are actually highly sought after by some people, particuarly those who don't want the power of an SVT.
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riksylvania
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Joined: 21 Jan 2003
Posts: 203
Location: Summerhill, PA
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| Posted: Tuesday Mar 13, 2012 |
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| It is, same preamp as svt with a 100watt power section and half the weight. |
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bassist_25
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Joined: 09 Dec 2002
Posts: 6815
Location: Indiana
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| Posted: Wednesday Mar 14, 2012 |
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I've never had the pleasure of playing through a V4 but even as someone who isn't a big Ampeg guy, I can't deny the awesomeness of playing through the mighty SVT (I really like those Hertiage series ones). I think you'll dig it.
The idea of a smaller wattage tube head is appealing to me more and more everyday. I recently made some changes on the cabinet end of things, and now my speakers are almost too efficient for my 400+. I'm blasting stage volume before I can even get close to the sweet spot. Yikes.
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riksylvania
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Joined: 21 Jan 2003
Posts: 203
Location: Summerhill, PA
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| Posted: Wednesday Mar 14, 2012 |
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The 300 watt one is a Fender ps300. They are quite rare, but sound awesome. They have the same guts as the Sunn 300t. I spent quite a while playing on the one I am trying to buy and it sounds fantastic. The whole thing is point to point soldered. It probably took the guy in the Fender shop a month to wire one up. It has a bell-like chime in its tone that a 59 Bassman has with bass or guitar.
It does stay very clean all the way up to ear damaging levels, which is why I'm going after a smaller head too. I remember that guys who played Bassman 100s or 135s for bass were pretty dirty sounding in a loud rock band. I'm assuming that the V4 will be similar. Soon I am going to lug my Hartke cab in to the guy's house to wind it up, so then we'll know for sure what it does.
My solution to this dilemma is what I usually decide: if I have one of each then I don't have to choose. (Much to my wife's dismay)
Running low wattage amps is a very strict practice for me on guitar, but I think bass will be determined by the project I am in. |
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lonewolf
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Joined: 25 Sep 2003
Posts: 6249
Location: Anywhere, Earth
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| Posted: Wednesday Mar 14, 2012 |
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| 313 wrote: | | lonewolf wrote: | | 313 wrote: |
All that bridging will do is double your output voltage swing. |
For linear power amps. For digital amps, the multiplier is the square root of two. |
By "digital" I assume you are referring to the Class D power amps? If so, I see no inherent difference in the outputs of a Class D and a traditional power amp, whether bridged or not - and the bridged mode voltage output of the Class D amp should be double. Data on my Class D power amp support this assertion:
Crown XLS-1500 delivers 300W into 8 ohms single channel, and 1050 Watts into 8 ohm in bridged. |
Yep, my bad on that--wrong spec--bridging is just bridging. Class D, G and H all have 1/sin 45 when calculating power gain after cutting the impedance in half and also when calculating RMS to instantaneous peak power. Linear amps generally have a factor of 2 with these relationships. This is good to know when matching amp to speakers.
Thanx for bringing up the XLS series! I was looking for a power amp that had a rack depth of less than 8" to power a guitar cab. I ran across these a year ago and forgot about them.
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floodcitybrass
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Joined: 31 Jan 2003
Posts: 527
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| Posted: Friday Mar 16, 2012 |
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If you have a BBE, sell it on ebay. Don't take advice from anyone that uses/endorses a BBE.
Bridged amps are used on subs and bass rigs all the time.
Bridging doubles the power given the same load (ohms).
The reason you want more power is so that it does NOT clip. The flat parts at the top of the signal (shown below) are what is bad. However, it is bad for the speaker (not amp).
It tries to hold the speaker to in one fixed position for too long.
Other interesting info about bridging and amps:
-Doubling the power only gives you about 3db increase in loudness.
-Speakers typically have a continuous rating and a peak rating. Many speakers suggest powering it with an amp 1.5 to 2 times the continous rating. The extra bit of headroom in the amp allows the amp to go above the continous rating level without clipping.
-Often, amps are not spec'd to power 2 ohm loads in bridge mono.
-A speaker can usually take occassional clipped signals. So don't think if the clip light blinks on once that your speaker is fried. You don't want continous clipping.
-You can protect your speakers from clipping by using a limiter or a compressor with a high ratio. |
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bassist_25
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Joined: 09 Dec 2002
Posts: 6815
Location: Indiana
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| Posted: Friday Mar 16, 2012 |
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| floodcitybrass wrote: | If you have a BBE, sell it on ebay. Don't take advice from anyone that uses/endorses a BBE.
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John has contacted me before to do sub work with you guys. I respectfully declined as my schedule wouldn't allow it. Good thing I didn't play the gig, as my credibility would have been in question when there was a BBE preamp as the front-end of my rig.
It's cool if you don't dig their products or the sound they produce, but to indicate that anyone who would recommend their preamp is not credible is just asinine. Both BBE's solid-state and tube preamps are highly respected amongst players, and I've put many of smile on sound engineers' faces when I gave them my direct signal. YMMV
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riksylvania
Gold Member
Joined: 21 Jan 2003
Posts: 203
Location: Summerhill, PA
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| Posted: Friday Mar 16, 2012 |
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| floodcitybrass wrote: | If you have a BBE, sell it on ebay. Don't take advice from anyone that uses/endorses a BBE.
Bridged amps are used on subs and bass rigs all the time.
Bridging doubles the power given the same load (ohms).
The reason you want more power is so that it does NOT clip. The flat parts at the top of the signal (shown below) are what is bad. However, it is bad for the speaker (not amp).
It tries to hold the speaker to in one fixed position for too long.
Other interesting info about bridging and amps:
-Doubling the power only gives you about 3db increase in loudness.
-Speakers typically have a continuous rating and a peak rating. Many speakers suggest powering it with an amp 1.5 to 2 times the continous rating. The extra bit of headroom in the amp allows the amp to go above the continous rating level without clipping.
-Often, amps are not spec'd to power 2 ohm loads in bridge mono.
-A speaker can usually take occassional clipped signals. So don't think if the clip light blinks on once that your speaker is fried. You don't want continous clipping.
-You can protect your speakers from clipping by using a limiter or a compressor with a high ratio. |
I understand the principles of bridging amps, I was just told that bass guitar in particular could be harmful to a bridged amp, which was dis proven. Thanks. |
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riksylvania
Gold Member
Joined: 21 Jan 2003
Posts: 203
Location: Summerhill, PA
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| Posted: Monday Apr 30, 2012 |
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| My new-used Ampeg SVPCL preamp will arrive this week, and coupled with my Crest power amp (Bridged ), and the Hartke Hydrive 810 cab it should be a nice little tone monster! Full report to follow. |
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CMOR
Gold Member
Joined: 04 Jun 2004
Posts: 367
Location: Right here.
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| Posted: Monday Apr 30, 2012 |
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| riksylvania wrote: | | My new-used Ampeg SVPCL preamp will arrive this week, and coupled with my Crest power amp (Bridged ), and the Hartke Hydrive 810 cab it should be a nice little tone monster! Full report to follow. |
And there it is.
I never thought I'd be happy to hear of somebody buying Ampeg. That's twice now...
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riksylvania
Gold Member
Joined: 21 Jan 2003
Posts: 203
Location: Summerhill, PA
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| Posted: Friday May 11, 2012 |
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Pre came in, and now the power amp shit the bed. (Channel A, anyway) I ordered a new Crown XTi 1000 for power. The preamp sounds great, I just need more muscle to move those speakers now.
I have to find someone to fix my Crest LA601 now. My normal Johnstown guy said that I need to go to a Crest dealer. (Butler or Kittaning he thinks) |
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