Using woofers for Bass Guitar Amplifier

Hi

As above.

I've seen most pro equipment has regular guitar speakers used as bass amps. Maybe larger, but essentially stiff, low Xmax 10" or 12" speakers much like the regular PA stuff.

Question: I have A couple of spare pairs of 12" woofers laying about. Not very good for Hifi, but cabinets are expensive so I was wondering if I could use the woofers for the Bassist (he doesn't have an amp, and he ruined one of mine by playing bass through it). Throw in a couple of TDA 7294 Amps, and pray to God they don't blow in the middle of a show.

Whaddya think??

Pinkmouse?

Anybody?

Thanks pinkmouse.

No I can't get any parameters for the drivers. 150L sounds about right, I may look at picking up a cheap compression driver for it.

I have one TDA 7294 laying about, it should give me about 40 watts into 8 ohm, should be enough for light practice duty. I'll be making a separate head with that amp (The chip is rated at 70 W/4 ohm, and I have a spare 225VA Xformer for it). That way I'll have a pair of 200 watt/4 ohm capable cabs which have enough grunt to take on a quality amp later.

Thankx.

Sangram

How things change in a few days.

Happy 2003 BTW. I'll open with a question: How much gain should a typical guitar signal have so it can reach amp-driving level? I thought about x100, but I'll wait for responses.

I spent new year's day on my gear.

Repaired a combo, whose speaker had blown at the last rig.

Finished the PSU and poweramp of the Bass amp. I see it as a small home practice unit as opposed to a big rig.

I now see it as a small head into which three guitars can plug in, including a bass, as opposed to a dedicated bass amplification system.

I see that the 7294 would not have been powerful enough to drive the 2x12 cabs.

So I built a speaker using a leftover 8" Philips woofer rated at 60 W RMS, and a horn tweeter of unknown antecedents. Extremely high pressure, so sounds very bright when playing music, but seems OK when playing a regular guitar through. Yet to try with bass.

The head is a 7294 based amp. I'm a little worried about heatsink size being on the smaller side, it's about 5" and I have no clue how much heat it can sink. I've used a CPU cooling fan to blow outside in onto the heatsink, more for insurance. I'm hoping the thermal cutout of the 7294 can save it in case of any emergencies.

It's very noisy, though, So I'm going to consider using a thermal switch for the fan, or run it off the 9V supply for the preamp instead of the 12V winding of the trafo.

The supply voltage is now at about 27V under idle 4 ohm load, since I got a new 120VA trafo for it with a 40V CT winding instead of the 50V CT 225 VA trafo earlier.

I'm still rigging up the preamp. For the moment, I'm going with an assembled microphone preamp, which takes a mixed input from three emitter followers, one for each channels. I plan TL074 based preamp in the near future, to check if the JFET in the opamp helps the tone. I need to know gain figures, though. I had planned 2 stages of x10, one for each stage and one final summing amp, that way a TL074 gets fully utilised.

I wish I had a Digicam. Actually, no. The chassis is pretty flimsy but it's only meant for in-home practice. I will rig up some cabs and a good 200W RMS amp for it. That's now a later project.

Should be rocking on Sunday's jam.

Cya

Done!

All done, it's rocking!

First run with the bass guitar is tomorrow.

Even if it doesn't go through there, I have a rocking acoustic guitar amp and cab. I've never heard such great acoustic sound plugged in, sounds like a real miced acoustic.

Weight of bass is amazing, with the picking and damped plucking. The entire amp is covered with silicon sealant to damp vibrations etc.

Three inputs, two with regular 40 dB gain and one with monster 60 dB gain for really quiet stuff.

I love this profession. Total cost of parts (excluding stuff I already had) was about $20...

Dude, the amp rocks.

I was at the first succesful practice yesterday. The bass never sounded so good. Never.

On the first attempt, I had forgotten the wire. We bought some lamp cord which caused some horrible feedback.

There are three inputs now, the bass is on one of the low inputs. I'm using the single high-gain input to mic one of my backup singers. This has freed up my guitar amp and should ensure its speaker last longer than a few sessions...

We practiced for about three hours yesterday but the amp never even got warm....

Hi

Our band is called Vayu. We basically do classic rock - 60s through 80s. Well, mostly...

We just got together, three months ago in fact.

My bassist used my little cube for his bass work. Obviously, the speaker blew up. Actually it didn't but the surround (these are those full range speakers with the edge of the cone doubling up as a surround) got torn. As a result my guitar tone was sounding bad.

I guess a P3A type amp will be good. Just be careful of the voltages - the fake transistors are a little dangerous. I would suggest thermal protection or cutout, as a fan + relay + a few components is generally cheaper than a large heatsink.

I guess an amp like that would be great for guitar, though. Guitar doesn't need much power - I can barely listen to a 30 Watt guitar amp at full blast, whereas my 7294 at full blast (close up to 80 watt) on a bass guitar sounds just pleasantly loud...

Just check how high the 12" will go, though. About 6 KHz should be fine. I would also be doubtful about the ability of the coil after you've got the speaker repaired. I wouldn't actually try to put more than 30 watts into it.

Thanks halojoy for your interest in our band. I like halomatics!!

Unfortunately our band does not yet have a website. We need a good place to put up our profile and our philosophy, and we are looking out for a host but not very high priority.

We have started very recently and are still having very little equipment, and also no original music. We have a few band videos etc. which are being digitised, and as soon as they are done we will look for a place to host them...

As for original music we do not have any compositions down yet but we are going to do some very interesting covers, like a death metal version of Beatles' Norwegian wood, and so on. We hope to graduate to compsing our own stuff soon, as soon as we find our feet while playing covers.

I am taking the liberty of adding you to our mailing list, though, so when the site is up you'll be the first to know. I will also put links to our music.


Corbato:

Thank you for your kind words. Sonodyne is now being run by Anindya, his son. Obviously the philosophy and products have changed somewhat. LPs are still selling at Rs. 15 on Dharamtala street and free School street, some very rare ones also.

On tubes, I have found RCA original 6L6 tubes at 375 bucks each, a steal if you ask me, but unfortunately no transformers, either output or power transistors. I have however been thinking of a hybrid with a tube pre using 12 AX7 (for which I believe 300 volt lines are easy to generate off a low V supply) and a solid state 100 watt section. Unfortunately my numerous excuses have got the better of the intention for now, so I am still waiting to transform that into action.

Standard robotics is the guy who supplies the sound to all the Kolkata gigs. He's unmissable...

Thanks for your interest and encouragement. It really means a lot to us.

I don't like using this board for stuff like this, but our email id is vayu@@musician.org Remove one of the @s to send a mail.

Thanks for the offer... I might just take you up on it, though. I travel pretty regularly to Delhi.

Yes I remember the old Sonodynes. Those were amazing amps by any standards, even their combination player+amplifiers were extremely high fidelity. I have not seen many of those amps in circulation in the second hand market, but plenty of Kenwood and Sansui. The Sonodynes are where they were intended to be: In homes...

We're going majorly off topic here, so here's something to close this...

I have ready access to some of those schematics, actually there is one guy in Cal who is selling kits based on those vintage Sonodynes - 50 watt RMS transistor based amps, excellent stuff compared to most local amps but in no way even close to the Sonodynes. Even after building them with 1% MFRs, tantalums etc. they are sonically different.

There are few points of view, chiefly that the transistors are no longer available so they are being substituted with equivalents. This is the chief reason, also the PCB does not have the exact same layout, and cap values etc have been somewhat changed. Power supplies have changed over the years, and the overall design is more 'efficient' than the 70s builds.

I have tried to build about ten of these amplifiers, and whereas I can say they are excellent amplifiers they do not hold a candle to the real thing. However for one who is bored with the 3055 based '60 watt' amplifiers this is a major step up.

And I am not saying they are different from the point of view of copyright issues only (these of course exist and no one will claim copying a design from Sonodyne, or anyone else for that matter.