Electric piano to hi-fi amp

[Guerilla]

Ive played a little guitar and sang with many guitarists. To me the good sound from tubeamps come from the powerstage. I would actually prefer an amp with transistor preamp and tube power.


Wouldnt a compressor to lessen the strain on tweeters be in order, if the output of the keyboard is so dynamic as described? Im not sure if the sound is not already compressed digitally. If not, some guitarpedal might do the job?

 

[Gnobuddy]

To me the good sound from tubeamps come from the powerstage.

My first good-sounding guitar amp was a Fender Super Champ XD, which has a transistor (op-amp + DSP) preamp, and a tube power amp section almost identical to the power section of a Princeton Reverb. I still have it, and still enjoy the tubey clean sounds from it, which come from only the tube half of the amp.

But what about the common practice of micing a small tube guitar amp and feeding it into the P.A. at a live event? Isn't the small guitar amp effectively a preamp in the signal chain, and the big P.A. the solid-state power amp? So clearly this can work to produce good guitar sounds, too. And the tube preamp / solid-state power amp topology allows you to overdrive the tube preamp without being forced to produce ear-destroying loudness levels in the process.

Wouldnt a compressor to lessen the strain on tweeters be in order, if the output of the keyboard is so dynamic as described?

Maybe it would work, maybe it wouldn't, maybe the compression would ruin the most distinctive characteristic of the instrument once known as the pianoforte, quite literally, "soft loud", itself a contraction of the original "gravecembalo col piano e forte", or "harpsichord with soft and loud". Take away the "soft and loud", and it isn't really a piano any more.

I can tell you for sure is that I knew a guy who did destroy his dome tweeters quickly by playing an electronic keyboard through them, in his tiny living-room. And I heard the same thing from a pair of professional speaker engineers who used to design speaker systems for a once well-known music electronics manufacturer.

It makes sens. Good Hi-Fi dome tweeters are incredibly delicate, as light as possible, and just barely strong enough for the job, like spider-silk. That job is to respond precisely and exactly to very brief, but very fast, musical transients, such as the sound of a cymbal crash in orchestral music.

Tweeters like this can tolerate brief power peaks, but very little average power. To tolerate more average power, you have to make the moving parts heavier and more durable - but this destroys the precise, fast response that makes it a good tweeter in the first place!

When you look at purpose-designed musical instrument speakers, you can see that the frequency response is usually heavily compromised in order for the speaker to survive the abuse it will experience. There may be no tweeter at all. If there is a tweeter, it will usually be a nasty-sounding compression tweeter with a horn. Sometimes it will be an even nastier-sounding piezo tweeter with a horn. When high SPL is a requirement, there really aren't that many other tweeter choices.

I have heard good-sounding compression tweeters, but only on speaker systems costing considerably more than $1000 USD per speaker. In my experience, the relatively affordable ones are always absolutely horrid.

I don't know what kind of speakers Rockola uses - he didn't say. But if they have good quality true Hi-Fi dome tweeters in them, they are not suitable for musical instrument use.


-Gnobuddy

 

[Guerilla]

Quote: Gnobuddy :" But what about the common practice of micing a small tube guitar amp and feeding it into the P.A. at a live event? Isn't the small guitar amp effectively a preamp in the signal chain, and the big P.A. the solid-state power amp?"

I feel thats different, cause then the guitaramp is already PRODUSING the right sound, and the following mic + PA REproducing it. Its a great idea and funny that it took so many years to come up with it. Could have saved a lot of ear-damage and saved us from a lot of bad-sounding concerts.
Take my opinions with a grain of salt. I never got to play enough guitar to learn to make an amp sound right. I was only singer in some bands and sold instruments and gear for some years.
Sorry for caps locks. I just dont know how to underline☺ You must be right about the tweeters. I just wasnt aware if the samples in electric pianoes had already had their transients lowered.


Sorry for all the off topic Rockola.��
Compresing might be what you need. That would make it more like what you hear on records at the expense of the dynamics of a live piano. Try to borrow one before buying or building, cause it might not be it.

 

[Gnobuddy]

I feel that's different, cause then the guitaramp is already PRODUSING the right sound, and the following mic + PA REproducing it.

Exactly - a small, low-power, tube pre-amp can produce the right sounds, whether we call it a "guitar amp" or not! The power amp can be inside the same box as the tube preamp, or it can be outside in a separate box and called a "P.A. system". And the preamp doesn't actually have to have a speaker and cab to make the right noises - it can just put out an electrical signal that goes direct to the power amp (or P.A.) with suitable speaker/cab emulation.

Here is an example, intended for professional use, with a tube pre, and a solid-state class D power section: Vintage British 800

Here is a much lower-budget product line with a similar (tube pre, SS power) topology, this time aimed at hobby players: MV50

I think the tiny little Vox MV50 series sounds about as "tubey" as my old SCXD, so it seems to me either approach (SS pre, and tube power, or the other way around) can produce usable results, as long as the concept is well executed. But the tube pre approach is more flexible in terms of managing SPL.

Take my opinions with a grain of salt.

Please take mine the same way. I find life is much more peaceful if I try not to take anybody's opinions, including my own, too seriously. 🙂

-Gnobuddy

 

[indianajo]

Compresing might be what you need. That would make it more like what you hear on records at the expense of the dynamics of a live piano. Try to borrow one before buying or building, cause it might not be it.

Compressed piano sounds like an ***-**** AM radio. If vendors in the hifi market don't want to reproduce piano, they should label their units "guitar & vocals only". I don't expect Rockola's home theatre system to have much capability for piano attack, it won't have the reserve watts. But I equiped a re-ecapped Allen 300 organ with KLH23 hifi speakers from 1976. The original Allen top end speakers were foam surround and that rotted away a decade ago. They sounded like **** in the donor church. In our church with the KLH23's, and amps restored to 100 W, organ sounds great. The KLH23 tweeters are 3" diameter with pasteboard cones, I hope you are wrong about them blowing up. There is a cap in series with each tweeter, and variable resistance controlled by a switch. I have the switch to minimum tweeter resistance, the ruling elder hates loud bass. So far, a year into it, so good. As a keyboard player I lucked out that hifi vendors pulled out of the Louisville market about 1980. Circuit City put everybody else out of business, and their specialty was buzz buzz in the trunk car systems. The only speaker left that any store would demo and sounds decent on a piano CD is Peavey, and they are a PA company. I scored a couple of used Peavey 1210 speakers about 1986 for my Ensoniq synth, which I played a lot of piano tracks on. They have triple Motorola piezo tweeters IMHO, and did fine. It was the amp I set fire to, a Dynaco ST-120 that wasn't up to four hour rehearsals at 10 W/ch. Not enough heat sink, no fan. Rockola, Peavey makes a special piano capable speaker system, the KB300, but it is mono with a 3 input mixer built in. Pricey even on the used market. btw the Ensoniq had standard 1.5 vac output. Pity Yamaha & Korg put them under.

 

[Gnobuddy]

If vendors in the hifi market don't want to reproduce piano, they should label their units "guitar & vocals only".

Live guitar and vocals through a typical good quality Hi-Fi or monitor speaker will also very likely blow the tweeters...maybe the woofers too. Recorded vocals and guitar are always carefully processed to limit maximum levels, but there is no such protection live. You never know when the guitarist is going to step on his "EarBlaster MaxCrunch Dirt Booster" pedal and blast out 20 dB more signal voltage than before, distorted into a square wave to make life even harder for the speakers. 😱

I don't expect Rockola's home theatre system to have much capability for piano attack, it won't have the reserve watts.

A few years ago I read about someone who measured the SPL of an actual grand piano in a living room, then tried to match it with an electronic keyboard and several large speakers. If I recall correctly, he ended up having to use about 150 watts of power to match the two SPLs when the piano was played with normal dynamics for a few typical classical piano pieces. That is a heck of a lot of power for a living room. 😱

The KLH23 tweeters are 3" diameter with pasteboard cones, I hope you are wrong about them blowing up.

Three-inch tweeters with pasteboard cones are a world away from a good 1" silk-dome tweeter with a flat response out to 20 kHz.

Three inches is big enough to beam treble heavily by about 2 kHz (3" is already a half-wavelength at 2.3 kHz), and pasteboard cones are too heavy and too floppy to go much above 5 kHz before response falls away.

But that may be exactly what you want to survive electric piano - a big heavy pretend-tweeter that is actually a brawny midrange speaker in disguise, able to handle far more abuse than a delicate, fly-weight dome tweeter.

...triple Motorola piezo tweeters

Those piezo tweeters were notoriously hard to kill. Some would say that was a bad thing, because they usually sound harsh and awful, and having them die would be a merciful release. 😀

A lot of cheap boom-box speakers in the 90's and later use a little piezo disc as the tweeter, often with a fake clear Mylar dome over it to fool the buyer into thinking it is a dome tweeter. There is no horn, and the piezo only works in the top octave or two of the audio band, say above 5 kHz. Used only way up there, and without the nasty horn resonances, it can sound pretty decent, and is still very hard to kill.


-Gnobuddy

 

[Shaun]

Coming in a bit late in this conversation, I want to share my own experience with a digital piano.

Dynamics
I find that typical hi-fi speakers don't do justice to the dynamics that such an instrument is capable of. My concern is not blowing tweeters, but rather how poorly the overall typical domestic system copes with the raw dynamic range. Musical recordings (i.e., albums, etc.) have dynamic range limitation (compression) applied in order to control dynamic range within practical limits for a domestic listening environment. This is one of the reasons that a piano recording never sounds like a live piano. (Note: this is apart from the controversial "loudness wars" that plague most modern recordings).

Audio Level
I have a Roland Integra 7 with a Roland A-88 keyboard. The Integra 7 is a sound module that also serves as a sound card for the small computer that I have it connected to. The sound from the keyboard is always lower than when I play music or other media from the PC through the sound module. My understanding is that this is due to the extended dynamic range that the instrument possesses. I believe that 0dB level is the same from both sources, but in practice you have to bang really hard on the keys to achieve 0dB level, while music albums (played form the PC) have a dynamic range that resides in a smaller band, which is on average on a higher level.

Speakers
I did not expect speaker selection to be an issue, especially since they would be positioned at the keyboard, effectively in the near field. I tried various speakers, but was always disappointed. The first was Quad L-ite, a small bookshelf model that I had been impressed with. It was a total let-down. I then tried another bang-for-buck speaker, Wharfedale 10.1. Better, but still not satisfying. I next tried my own 2-way DIY speakers that used an Adire Audio Extremis 6.8 mid/bass with Dayton RS28F tweeter. This was my last-gasp solution but, much to my chagrin, it was far from it! I resigned to using headphones for a while, until one day I stumbled upon a pair of Behringer Truth B2031A active monitors. Much to my surprise, they performed admirably. At last, a speaker that had enough dynamic headroom to not get in the way of the sound of the instrument! It is not a perfect solution, since its low end spec is 50Hz (there is a matching subwoofer available) but, finally, I was able to appreciate the difference between a hi-fi speaker and a pro audio speaker.

In conclusion: a pro audio speaker is the better solution for reproduction of musical instruments.

 

[indianajo]

Thanks, gnobuddy & shaun for the review of available technology. My speaker experience is somewhat limited to what I bought in this flyover state, where there aren't a lot of shopping choices & almost no stock in stores. Best Buy has a single driver Polk audio speaker, but they won't demo it on my piano CD the way the Peavey dealer would the SP2. Nice to know exactly what a dome tweeter is, since I never had any.
Yes, I love the dynamic range of my real Sohmer & Steinway wood (console) pianos. But I do listen to recordings a lot, many with piano prominent. My 70 W/ch ST-120 amp and 129 db capable Peavey SP2 speakers (15" + 2" horn) do just about satisfy me. Which is why I donated the KLH23's with the 3" cardboard tweeters - they weren't quite real. Organ without synth option has no frequencies over 7 khz, so the church will be fine with them. KLH23's were nice in 1976 when I made $8 an hour.
In future I'm hoping to upgrade my music room system with a 200 W/ch amp for even more thrilling peaks over my 1.5 vpp average volume. The SP2's will take 300 W rms, 600 W "program power". They are sensitive too, 101 db @ 1W 1m.
Yes, shaun, I found my Ensoniq synth was rather quiet unless I pounded on it: Even though my ST-120 had mega-gain for a hifi amp. I bought a Ampeg mono mixer to boost level up a little for my live synth performances. I sat on the mixer turned sideways (12" deep), and put the keyboard on an organ bench.

 

[Gnobuddy]

...one day I stumbled upon a pair of Behringer Truth B2031A active monitors. Much to my surprise, they performed admirably.

Keep in mind those Behringer Truth speakers are near-field studio monitors with a delicate, fly-weight dome tweeter - exactly the kind of speaker that produces accurate sound, but is likely to fry if you feed a live musical instrument through it (keyboards, guitar, etc.)

Earlier I referred to a fellow I knew who blew up his tweeters with his electronic keyboard - those tweeters were in a very similar pair of near-field studio monitors, made by Alesis.

Back then, Alesis made high-quality, well respected studio monitors. Sadly, the story is very different today. The original Alesis Corp went bankrupt in the early 2000s, and the name was sold to a completely different company. That company has since churned out a lot of mediocre toy products under the Alesis name.

I fully understand your preference for the much more accurate sound of studio monitors compared to consumer speakers. I heard my first near-field studio monitors in 1998, and the improvement over the supposedly Hi-Fi speakers I'd heard all my life up till then was shocking. I was hearing things on my old CDs that I'd never heard before, though I'd listened to those same tracks hundreds of times already.

As a result of that experience, for most of the last twenty years, my CD player and TV have been hooked up to a pair of Alesis near-field studio monitors. Except for the car, I do virtually all my music listening through studio monitors.

(But I never play my guitar or keyboards direct through them, only play back guitar or keyboard parts I've already recorded.)

In conclusion: a pro audio speaker is the better solution for reproduction of musical instruments.

Keep in mind there are two very different categories of pro audio speakers.

Your Behringers fall into the category of small studio monitors, designed for monitoring playback of recorded tracks during mixing. They are designed to get loud within a few feet of the speakers. The speakers are designed to be within a metre or so of the mix engineer's ears. But they are not designed to generate high SPL in a large acoustic space, or to tolerate the abuse of live musical instrument use.

The other, entirely different, category of pro audio speaker is intended for public address / sound reinforcement. These are designed with almost the opposite set of compromises compared to near-field studio monitors.

Sound reinforcement speakers are big (to generate high SPL in a large space, even outdoors), brawny (to tolerate lots of power and the abuse of live instrument use), sensitive (in the dB SPL per watt sense, in order to generate very high SPL), and tend to produce inaccurate and mediocre-quality sound. The tweeters in them are designed to be as tough as leather, and the treble frequency response is usually very poor as a result. Big screechy peaks and dips above 1 kHz, and nothing above 10 kHz, is common.

There are very expensive P.A. speakers that do produce pretty good sound, but the affordable ones tend to sound bad at best, and awful at worst.

For myself, I found a compromise. I run both my guitar and vocals through an Acoustic AG30, a wedge-shaped powered speaker designed for exactly this use. It uses a woofer and a Mylar dome tweeter - not as accurate or precise as a proper silk-dome or titanium-dome tweeter, but also not as fragile.

Sound quality is nowhere near as good as a studio monitor, but is much better than most P.A. systems with those horrid screechy horn tweeters.

The price paid for using the Mylar dome tweeter instead of the nasty-sounding horn tweeter is that max SPL is limited. It gets more than loud enough for what I do, with only 30 watts. But if you compare those 30 watts to the 500-odd watts found in even cheap powered P.A. speakers these days, you can see that those other systems get much louder, at the expense of sound quality.

When I bought the AG30, I also listened to similar products from various other big MI companies - Roland, Fender, etc. The Acoustic sounded far better than most of the other brands. The Roland sounded about as good, but cost twice as much. Easy decision, if you make it with your ears, and not your eyes!


-Gnobuddy

 

[thoglette]

There are very expensive P.A. speakers that do produce pretty good sound, but the affordable ones tend to sound bad at best, and awful at worst.

Nail that to the wall where you can see it, folks.

Once in a while a big brand puts out something genuinely noteworthy, (even at the price point), and we get a pile of me-too look-a-likes, which may or may not sound anything like the originals. To add to the confusion, different products from the same brands (or the "same" products sold years later) can perform completely differently, despite having nominally similar specifications.

 

[Kay Pirinha]

Sound reinforcement speakers are big (to generate high SPL in a large space, even outdoors), brawny (to tolerate lots of power and the abuse of live instrument use), sensitive (in the dB SPL per watt sense, in order to generate very high SPL), and tend to produce inaccurate and mediocre-quality sound. The tweeters in them are designed to be as tough as leather, and the treble frequency response is usually very poor as a result. Big screechy peaks and dips above 1 kHz, and nothing above 10 kHz, is common.

There are very expensive P.A. speakers that do produce pretty good sound, but the affordable ones tend to sound bad at best, and awful at worst.

Nail that to the wall where you can see it, folks.

Oh oh oh! Would you please compare this to the profund statements in the »PA Speaker for home HiFi use« thread?
Best regards!

 

[indianajo]

I took gnobuddys statements about sound reinforcement speakers for an observation of the market where peaky screechy woofer + 1" horn units are outselling 2" horn driver units 10 to 1. My SP2 with 2" horn driver & 15" woofer are very smooth at 1 W and sound great from 13' away on poles in my living room. I tested them with piano CD before I bought them.The 2" horn driver in the SP2 makes for a nice crossover. But I don't see those used by stage bands, til you get to top line acts . I was too far away to see what Lynyrd Skynyrd was using to amp up their piano in November, but it sounded good.
Monitor speakers are fine for sitting between a pair playing your electronic keyboard, but my sound reinforcement speakers are for when the CD or LP is playing in the living room. I use real wood & steel when I play piano, or a hammond organ with its own speaker. The SP2 are cool when I put Leslie simulator (digital) on the auxillary out of the hammond. The hammond is between the SP2 poles but the sound bounces off the plaster wall 15' away very nicely.

 

[thoglette]

Oh oh oh! Would you please compare this to the profund statements in the »PA Speaker for home HiFi use« thread?
Best regards!

I've run down enough rabbit holes already😀

There's a few PA speakers I'd happily have in the home*: just about anything by Danley Sound Labs or a properly designed/tweaked modern VOT (see here for thousands of pages of discussion)

Both are "not cheap".

*if one ignores the one key parameter they fail on: SAF (Spouse Acceptance Factor)