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NEKID PICTURES!! (Yamaha P120) #1439246
05/18/10 05:49 PM
05/18/10 05:49 PM
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dewster Offline OP
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Photos Of Naked Model On The Internet!

Yesterday I decided to take our Yamaha P120 apart. My interests were two-fold. Mainly, like any engineer worth his salt, I wanted to peer at the guts inside, write down some chip numbers, and look up the parts on the web - level one reverse engineering. But I also wanted to do my part to push any visiting techs over the edge into a nervous breakdown, so I'm sharing some photos of it here in this public forum. smile

I took it off the stand and set it on the studio rug on it's back. The application of one Philips screwdriver over a 10 minute time span and the dirty deed was done. Our Yamaha P120 laid bare before my eyes - make love to the camera, baby!

[Linked Image]
Here is the P120 disassembled. It turns out you really only need to remove the screws to the back section, not the sides or the front. The back section slides into slots in each end piece, to remove it just slide it back and then lift up once you hit the end of the slots. The left end holds all the connectors (a rather awkward and unfortunate design decision IMO). The whole deal is supported by a slab of aluminized MDF on the bottom.

[Linked Image]
A view to the left side of the guts. Here you can see the main processor board and the left speaker. Lots of wires. Must be somewhat labor intensive to manufacture.

[Linked Image]
A view to the right side of the guts. Here you can see the audio amplifier board (nice heatsink) and the right speaker. The speakers are rated 10W / 20W max. and as you can see are unfortunately not acoustically contained in any way, just flopping in the breeze. They actually point out the back of the DP, with a slot in the top permitting the backwave to reach the player. Pretty odd all around. Sounds about as good as you might expect for such an arrangement (i.e. not too good).

[Linked Image]
A better view of the processor board. You can see the wire harness to the keyboard, and a large RF-reducing ferrite doing double duty as a wire anchor. The upper board holds all the control buttons and blinking lights and stuff.

[Linked Image]
Key mechanism in the key-up position. Yamaha uses rods bent in a hairpin shape for the weight. You can kind of see the leaf spring there too.

[Linked Image]
Key mechanism in the key-down position.


On the audio board heatsink I discoved this IC:

LA4705N - 15w 2-channel Power Amplifier

And here are some of the parts on the main board

CY62256LL-70SNC - 256K (32K x 8) Static RAM
OKI MSM514260E-60TK - 256K x 16 DRAM
PCM69AU - Dual D/A, 18-bit
Yamaha X201110 - house numbered, most likely flash
Yamaha X201??D - house numbered, most likely ROM or key scanner
Yamaha ??947C0 - house numbered, most likely ASIC
TD62785F - Transistor array (8x)


I'm kind of surprised they apparently use ASICs as processors, they must make tons of these. Too bad the flash is house numbered, I would have liked to have known the size of the sample storage. Couldn't find any soul to speak of.

Afterward I buttoned it back up and checked all the keys - it seems no worse for the peek at the internal organs.

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Re: NEKID PICTURES!! (Yamaha P120) [Re: dewster] #1439304
05/18/10 07:19 PM
05/18/10 07:19 PM
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The keyboard looks mostly the same as the GHE/GHD in my CVP96.
The keyscanner is a single prozessor chip 40 pin DIL and is on the PCB that is beneath the keys. (when it is the same as I had seen)
If I counted correctly, there are 8 wires. Thats not enough for VCC,GND and 88*2 switches to decode, so it is probably the same ;-).


Did you check if the hammers can move independently from the keys? (I dont believe so)

For further questions ask here for the service manual.
http://www.wdgreenhill.com/

They have much more than listed, ask.
You get legal paperware only, no pdf's.

;-)

Peter



Last edited by hpeterh; 05/18/10 07:37 PM.

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Re: NEKID PICTURES!! (Yamaha P120) [Re: hpeterh] #1439333
05/18/10 08:10 PM
05/18/10 08:10 PM
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Thanks, Dewster. Nice photos. Always interesting to see the inside of these machines . . .

Re: NEKID PICTURES!! (Yamaha P120) [Re: hpeterh] #1439339
05/18/10 08:18 PM
05/18/10 08:18 PM
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Originally Posted by hpeterh

If I counted correctly, there are 8 wires. Thats not enough for VCC,GND and 88*2 switches to decode, so it is probably the same ;-).



They don't need to monitor all the keys at once. They scan the keys. Basically they ask each key switch in turn "are you closed?" Then the switch can report it's state using a "party line" shared by all the 88*2 switches.

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Re: NEKID PICTURES!! (Yamaha P120) [Re: Melodialworks Music] #1439341
05/18/10 08:21 PM
05/18/10 08:21 PM
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Hamamatsu, Japan
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Agreed - thanks for the pics dewster.

Do you know approximately when this instrument was manufactured? It would be interesting to compare the internals to the P140 which I believe replaced the P120, then the P155 which replaced that.

Hmmm...I wonder why Yamaha chose to name the product P155 - P160 would surely have been the more logical progression, albeit potentially confusing with the YDP-160.

Cheers,
James
x


Employed by Kawai Japan, however the opinions I express are my own.
Nord Electro 3 fan & occasional rare groove player.
Re: NEKID PICTURES!! (Yamaha P120) [Re: Kawai James] #1439344
05/18/10 08:26 PM
05/18/10 08:26 PM
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I've never really understood the numbering of various models of various manufacturers. I suspect that they've got a bunch of number and letter combinations on a giant dartboard. When it comes time for a new model, they throw a dart.

Re: NEKID PICTURES!! (Yamaha P120) [Re: hpeterh] #1439386
05/18/10 09:43 PM
05/18/10 09:43 PM
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Originally Posted by hpeterh
The keyboard looks mostly the same as the GHE/GHD in my CVP96.
The keyscanner is a single prozessor chip 40 pin DIL and is on the PCB that is beneath the keys. (when it is the same as I had seen)
If I counted correctly, there are 8 wires. Thats not enough for VCC,GND and 88*2 switches to decode, so it is probably the same ;-).

Good eye! Yes that's 8 wires going to the keyboard assembly. I believe the key scanner chip is a 48 pin DIP right there on the main board (interesting that it is socketed):

[Linked Image]

Maybe they use diodes and multiplex the heck out of it? Or perhaps there is a scanner on the key assembly and it sends serial (MIDI?) data? I should have investigated that more closely.

I didn't think to check the mechanical independence of the hammers, though I did take a movie of pressing a key, see what you think:

http://www.mediafire.com/?enjlzmowwz2

Thanks for the link!

Re: NEKID PICTURES!! (Yamaha P120) [Re: Kawai James] #1439390
05/18/10 09:47 PM
05/18/10 09:47 PM
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dewster Offline OP
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Originally Posted by Kawai James
Do you know approximately when this instrument was manufactured?

There's a chip in there with 2001 marked on it if that means anything. Perhaps the serial number has the date encrypted in it somehow, or there is a table of what serials were manufactured when somewhere?

Re: NEKID PICTURES!! (Yamaha P120) [Re: dewster] #1439440
05/19/10 12:28 AM
05/19/10 12:28 AM
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Fantastic breakdown of the keyboard dewster!

Originally Posted by dewster

I'm kind of surprised they apparently use ASICs as processors, they must make tons of these. Too bad the flash is house numbered, I would have liked to have known the size of the sample storage. Couldn't find any soul to speak of.


It doesn't surprise me that an instrument of this vintage has an ASIC. My guess is that there's probably a fair amount of full custom DSP to provide all the goodies including real-time effects with low latencies. They weren't going to use FPGAs of that era (nowhere near dense enough for the cost), and off-the-shelf DSPs were powerful enough but probably more expensive per unit than the ASIC (even considering ASIC NRE) and possibly more hungry for both board space and power. That's not including other things like the main micro, peripheral interfaces, etc. which they could do with an ASIC. Off-the-shelf System-on-a-Chip was still getting its legs at this point and was definitely not targeting this application.

Once again, hat's off to you for a great review!


RD-700GX + SN Piano Expansion
If you're playing and you know it, wash your hands! If you're playing and you know it, no sanitizer!
If you're playing and you know it, and don't want your keys to show it,
If you're playing and you know it, clip your nails!
Re: NEKID PICTURES!! (Yamaha P120) [Re: pianodilemma] #1439480
05/19/10 02:11 AM
05/19/10 02:11 AM
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The P-120 wasn't one of Yamaha's better moments...you'd be better off trading it in on a Roland RD-700 GXF...they look much nicer when taken apart...

Snazzy


Semper Gumby: Always flexible \:^)
Re: NEKID PICTURES!! (Yamaha P120) [Re: snazzyplayer] #1439485
05/19/10 02:25 AM
05/19/10 02:25 AM
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Quote
The P-120 wasn't one of Yamaha's better moments.


Snazzy, would you care to elaborate?

Cheers,
James
x


Employed by Kawai Japan, however the opinions I express are my own.
Nord Electro 3 fan & occasional rare groove player.
Re: NEKID PICTURES!! (Yamaha P120) [Re: Kawai James] #1439502
05/19/10 03:47 AM
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No need...Dewster is doing fine.

Snazzy


Semper Gumby: Always flexible \:^)
Re: NEKID PICTURES!! (Yamaha P120) [Re: snazzyplayer] #1439504
05/19/10 03:53 AM
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What have been the highest selling Yamaha boards in the past? Anyone know the numbers?

Re: NEKID PICTURES!! (Yamaha P120) [Re: dewster] #1439510
05/19/10 04:28 AM
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[Linked Image]

This one of the two keyboard - contact PCB's taken from CVP96 SM.
Because it has a quartz, it is probably a single chip CPU that actively scans and debounces the contacts and initiates interrupts and sends serial data to the main CPU.

I think this 40Pin DIL visible on your photos scans and multiplexes the front panel switches and LED's.

Last edited by hpeterh; 05/19/10 05:34 AM.

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Re: NEKID PICTURES!! (Yamaha P120) [Re: theJourney] #1439511
05/19/10 04:28 AM
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Originally Posted by theJourney
What have been the highest selling Yamaha boards in the past? Anyone know the numbers?


Yamaha's DX7 keyboard synthesizer reportedly sold 160,000 during the 80's, according to Keyfax 4.

Korgs's M1 has allegedly surpassed this figure (Keyfax 4 again).

Best selling piano was supposedly the P-250 (2002) from what I hear.

Snazzy


Semper Gumby: Always flexible \:^)
Re: NEKID PICTURES!! (Yamaha P120) [Re: dewster] #1439689
05/19/10 10:58 AM
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Originally Posted by dewster
... The speakers are rated 10W / 20W max. and as you can see are unfortunately not acoustically contained in any way, just flopping in the breeze. They actually point out the back of the DP, with a slot in the top permitting the backwave to reach the player. Pretty odd all around.


I think their design is more sophisticated than you give credit. I think they assume the piano will be placed up against a wall. They are using the wall, the internal volume of the P120 case and the slotted opening to shape the sound. They do a good job considering the very low cost parts used. It actually would have been easier for them to mount the speaker cones facing up and cut a speaker grill in thetop of the piano case. But then it would really sound like a toy piano.

There is enough room inside for you to "hot rod" the audio section maybe with some full range Fostex drivers and a better amp.

Re: NEKID PICTURES!! (Yamaha P120) [Re: ChrisA] #1439791
05/19/10 02:03 PM
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Originally Posted by ChrisA
They are using the wall, the internal volume of the P120 case and the slotted opening to shape the sound. They do a good job considering the very low cost parts used.

I've seen some pretty amazing stuff done with low cost parts. A decently flat mid-bass driver, a paper cone tweeter, an electrolytic non-polar capacitor, maybe a sandblock resistor, and a coil if absolutely necessary, all can be had for $10 to $15 per side retail. Put that in a proper sealed or ported enclosure and it can sound like way more than you paid for. But here all they have is an oval speaker, and they point the back of it at you through a slot in a big leaky box. They're not even trying.

Originally Posted by ChrisA
It actually would have been easier for them to mount the speaker cones facing up and cut a speaker grill in thetop of the piano case. But then it would really sound like a toy piano.

The flattest FR is almost always from the front of the driver on-axis. The backs of these speakers point into the entire cavity of the DP, which isn't sealed by any means. The L & R speakers even share the same acoustic space. In this leaky space the slot can't have any real tuning capability as in a ported enclosure. In such a scenario the main thing the backwave emerging from the slot would do is cancel out the frontwave, producing anemic bass. It's pretty clear Thiele & Small weren't consulted for this design.

Originally Posted by ChrisA
There is enough room inside for you to "hot rod" the audio section maybe with some full range Fostex drivers and a better amp.

It really could use a better set of sounds too, so beefing up the audio would be a diminishing returns thing. Easier just to buy something new with no built-in speakers as we're already using an external amp.

Re: NEKID PICTURES!! (Yamaha P120) [Re: dewster] #1439801
05/19/10 02:21 PM
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fascinating stuff... except i won't take my p155 apart.

Re: NEKID PICTURES!! (Yamaha P120) [Re: signa] #1439805
05/19/10 02:30 PM
05/19/10 02:30 PM
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<--- is hyperventilating.

This is my favorite thread for all week. laugh Loved the pics, and the commentary just as much. "make love to the camera, baby" [snorts with laughter]

Re: NEKID PICTURES!! (Yamaha P120) [Re: hpeterh] #1439817
05/19/10 02:49 PM
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Originally Posted by hpeterh
[Linked Image]

Interesting. They have 15 banks of 12, which gives 15 * 12 = 180.

180 / 88 = 2.0455

So there are two switch contacts per key, correct?

The XCK / ACK looks like some kind of handshake, S0 could be serial out. Series resistors on the outputs for signal integrity. And I agree that the crystal strongly implies a processor, particularly that humongous DIP.

Re: NEKID PICTURES!! (Yamaha P120) [Re: dewster] #1439842
05/19/10 03:53 PM
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I think some contacts are dummies or used to configure the keyboard.
At least one of the diodes must be cut for certain piano models.
I had a replacement keyboard and there where a instruction sheet that said this.

BTW, doesnt the Bosendorfer have 90 keys?
This keyboard was built around 1995. Did they already have the plan to buy Bosendorfer? That would explain something. Now we come from naked pictures into skandals and naked truth ;-)


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Re: NEKID PICTURES!! (Yamaha P120) [Re: dewster] #1439854
05/19/10 04:13 PM
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Originally Posted by dewster
..
The XCK / ACK looks like some kind of handshake, S0 could be serial out. Series resistors on the outputs for signal integrity. And I agree that the crystal strongly implies a processor, particularly that humongous DIP.


I doubt the keyboard scanner is a microcomputer. My guess would be some kind of programmable or custom logic. The crystal could drive a counter.

If it is a microcomputer you could ID it easy as few would have Vdd and Gnd on those four pins with clock on other specic pins

Re: NEKID PICTURES!! (Yamaha P120) [Re: hpeterh] #1439865
05/19/10 04:26 PM
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Originally Posted by hpeterh
Did they already have the plan to buy Bosendorfer?

My wife almost cried when she heard about that.

Re: NEKID PICTURES!! (Yamaha P120) [Re: ChrisA] #1439873
05/19/10 04:42 PM
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Originally Posted by ChrisA
I doubt the keyboard scanner is a microcomputer. My guess would be some kind of programmable or custom logic.

You could do it with logic, but the algorithm is sufficiently slow and complex that a dedicated low-end processor is probably the best solution. Chamberlin lists 6502 assembly code for a keyboard scanner in his book "Musical Applications of Microprocessors". There is a small state machine associated with each key to handle debounce.

BTW that's a truly fantastic (though dated) book - he even did all the illustrations himself using only the period character on a daisywheel printer. Truly an engineer's engineer.

Re: NEKID PICTURES!! (Yamaha P120) [Re: dewster] #1439876
05/19/10 04:45 PM
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Originally Posted by dewster

The flattest FR is almost always from the front of the driver on-axis. The backs of these speakers point into the entire cavity of the DP, which isn't sealed by any means. The L & R speakers even share the same acoustic space. In this leaky space the slot can't have any real tuning capability as in a ported enclosure. In such a scenario the main thing the backwave emerging from the slot would do is cancel out the frontwave, producing anemic bass. It's pretty clear Thiele & Small weren't consulted for this


You are thinking about stereo hifi. Musical instrument speakers use different rules. Same physic but different gaols.

Think of those speakers as an "open baffle" design. A lot of audiophile with small tube amps are finding that "open baffle" works well. These speakers have no box. Unconventional in the stereo world but...

Guitar players have been running "open back" cabinets for 60 years. These are just 5 sided boxes. Most who use them think the sound is better.

The advantage both for stereo open baffle and guitar over conventional boxed speakers is that sonically the speakers disappear and the sound seems to come from all around the room. If you push the piano up to the wall the wall itself becomes part of the speaker baffle.

I don't think the slot is a bass reflex port. I think it is a filter (bass can't get out a hole that size" and acts a bit like a line array. The sound would be dispersed in a direction perpendicular to the slot.

Same for the leaks n the case. That would kill most HiFi speakers but obviously the open box designs are not air tight

They are simulating what an acoustic piano does, sends the lows into the floor and the highs mostly upward

I think it is OK to let the left and right mix inside the cabinet. They are not trying to produce a stereo image as in HiFi. They are replaying samples that were sampled with mics inside the same piano case.

If you really want to see a set of speakers that don't follow HiFi rules look at the Yamaha N3 or N2. You have to think of those more are transducers replaying samples than as stereo speakers, then it makes more sense.

Last edited by ChrisA; 05/19/10 04:49 PM.
Re: NEKID PICTURES!! (Yamaha P120) [Re: Monica K.] #1439889
05/19/10 05:06 PM
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Monica, you have some very nice videos! I'm impressed that you are self-taught - did you use a method at first? And is that a Mason & Hamlin you're playing?


Re: NEKID PICTURES!! (Yamaha P120) [Re: ChrisA] #1439913
05/19/10 05:46 PM
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Originally Posted by ChrisA
The advantage both for stereo open baffle and guitar over conventional boxed speakers is that sonically the speakers disappear and the sound seems to come from all around the room.

Open-back speakers have a frequency response and radiation pattern that is highly dependent on how the backwave mixes with the front wave. For electric guitar this can be a good thing as the comb filtering can pep up what might otherwise be a drab sound, and it can increase efficiency and provide a pseudo stereo effect.

Sound travels about 1 foot per millisecond, so one would expect frequencies around 1kHz to "see" physical features on the order of a foot or more. This is the reason the "baffle step" happens in bookshelf speakers around this frequency, as the waves emitted from the drivers become able to interact with the sides and back of the cabinet, and not just the baffle board they are mounted on.

For 100 Hz the minimum interaction dimension is around 10 feet, and for 20 Hz this dimension is 50 feet. This is why bass guitarist don't generally use open box speakers - the dimensions of the box would have to be huge in order to keep all low frequency content from completely canceling out. And this is why 99% of all subs are in sealed or carefully designed ported enclosures.

Originally Posted by ChrisA
bass can't get out a hole that size

The port on a bass reflex enclosure is responsible for radiating the lion's share of the lowest frequency sonic energy into the room. Fourth and sixth order bass cabinets don't even expose the driver to the listening environment, 100% of the radiation comes from a port. So yes, bass most definitely can and routinely does get out of a hole that size.

Re: NEKID PICTURES!! (Yamaha P120) [Re: dewster] #1439924
05/19/10 06:14 PM
05/19/10 06:14 PM
Joined: Sep 2007
Posts: 14,430
Hamamatsu, Japan
Kawai James Online content
Yikes! 10000 Post Club Member
Kawai James  Online Content
Yikes! 10000 Post Club Member

Joined: Sep 2007
Posts: 14,430
Hamamatsu, Japan
dewster, when you eventually bite the bullet and buy a new instrument (CP50, RD-700GXF, or maybe even a Kawai...) to replace that ageing P-120, perhaps you should consider performing a few after-market alterations on your trusty Yammy - a kind of 'Pimp my DP', if you will... wink

Cheers,
James
x


Employed by Kawai Japan, however the opinions I express are my own.
Nord Electro 3 fan & occasional rare groove player.
Re: NEKID PICTURES!! (Yamaha P120) [Re: Kawai James] #1439966
05/19/10 07:32 PM
05/19/10 07:32 PM
Joined: Jan 2010
Posts: 792
V
Volusiano Offline
500 Post Club Member
Volusiano  Offline
500 Post Club Member
V

Joined: Jan 2010
Posts: 792
Originally Posted by Kawai James
dewster, when you eventually bite the bullet and buy a new instrument (CP50, RD-700GXF, or maybe even a Kawai...) to replace that ageing P-120, perhaps you should consider performing a few after-market alterations - a kind of 'Pimp my DP', if you will... wink

Cheers,
James
x

I think Dewster would not just pimp his DP but build his own DP if he could ((like how he built his own PC). Now only if they sell different DP components to assemble into a system like they do PCs.

Re: NEKID PICTURES!! (Yamaha P120) [Re: dewster] #1439985
05/19/10 08:08 PM
05/19/10 08:08 PM
Joined: Aug 2005
Posts: 18,311
Lexington, Kentucky
Monica K. Offline

Platinum Supporter until Dec 31 2012
Monica K.  Offline

Platinum Supporter until Dec 31 2012


Joined: Aug 2005
Posts: 18,311
Lexington, Kentucky
Originally Posted by dewster
Monica, you have some very nice videos! I'm impressed that you are self-taught - did you use a method at first? And is that a Mason & Hamlin you're playing?



Thank you! You're very sweet. My (only) method is "all new age, all the time." Not exactly pedagogically recommended. wink But I did have 7 years of accordion lessons as a child, so I'm only self-taught on piano.

And, yes, that's a Mason & Hamlin A. Great acoustic. But I do lust after a digital from time to time, especially when I am dying to play but the kids have just gone to bed so I need to be quiet. frown

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