Recent Posts

Pages: [1] 2 3 ... 10
1
The Wurlitzer Electric Piano / Re: Some DIY reflections
« Last post by Jezza on Today at 03:30:43 PM »
The feeler gauge while tuning is a great idea. Like Steve I just hold the reed in place with my other hand while tightening it. That usually works fine, but for more fussy reeds the gauge might help. You would still have to hold the reed in place somehow to adjust front to back, so I imagine the gauge is an unnecessary complication most of the time.

Paleophone, thanks for the tip about the steel drum sound. I have a couple of notes that sound that way, and I'll check to see if perhaps I just need to center the reed better. (I think they're just funky reeds, but who knows...)
2
Thanks for this.

There is a bit of 120Hz hum, but it's dominantly 60Hz. The heaters are a more likely the main culprit than the power supply.

The image below is how the heaters in this amp are wired. The idea of using both sides of the transformer wiring and adding a hum balance pot is a good one. It would be a little nuisance to implement, but maybe I'll try it. Many thanks for that suggestion.

Swapping the tubes helped a little bit, and changing the power supply caps to slightly nicer ones helped a bit also. The amp is in pretty good shape, so it's a matter of finding little degrees of improvement wherever I can.

Your hum balance pot suggestion probably addresses the problem more directly than creating a star ground scheme for the whole amp in hopes of fixing something unknown.
3
Right?! I am going to remove this post tomorrow, maybe Ill take some time to make a video to compare the SV1 to my rhodes and wurli and upload to youtube.
4
This amp uses only one leg of what's presumably a 12.6V winding to create the 6.3V for the heaters. The other leg is grounded, so there's nothing to twist the heater wires with. I have shielded them with foil tape and pressed them into corners as best as I can.

Your mod to your 140 volume pot is interesting. I just tried shorting Hot-Wiper and got nothing but 60Hz hum. Perhaps I should swap the pot before I do anything else more serious.

Thanks for the Uncle Doug video. I remember it from years ago and I actually watched it earlier today too. As far as I can tell, it confirms that I do not have tube noise.

I'm confident it's a ground loop, and I'm hoping if I can protect the preamp section from loops that perhaps I won't have to mess with the rest!

There are so many potential causes for hum, no one could possibly predict with confidence what would ameliorate your issue unless they had solved the identical problem with the same model piano.  One thing you mentioned that is almost ALWAYS a source of hum is heaters powered by a grounded AC power source.  The usual way to power tube heaters is through an isolated transformer winding that is configured to have equal and opposite voltages at the connections to the tubes.  There are typically 2 ways of achieving this result.  One is to use a center-tapped winding, whose center tap is grounded.  The other is to connect the isolated heater voltages to ground through equal resistors, or to use a pot whose center tap is grounded.  I have a tube amp I sometimes use with my Rhodes piano that has a so-called hum balance control, which is, in fact, a pot connected across the heater windings.  When set just right, amp hum almost completely disappears.  Setting the pot to one end of the other results in plenty of hum.  One reader mentioned Uncle Doug's dissertation on hum.  One point is germane to your problem.  Hum from a full-wave rectified power supply is at 120 Hz.  Hum from an unbalanced heater connection is at 60 Hz.  Good luck!
5
I am 99.99% sure that 10Meg input impedance is not the reason for the quietness of the Countryman DI.

My empirical experiments are pretty strong evidence that is hard to dispute.  I don't know what is inside the Countryman other than ad copy claiming it has FET input stages, and the electronics are encased in epoxy. 

In fact I learned of the trick on Gearslutz from Mr. Jim Williams, an audio engineer with a long history of improving audio equipment for a few decades including some major name recording artists from the 1970s.

Quote
All versions of the stage piano have input impedances at least 10X lower than 1Meg.

No, you're confusing input impedance with output impedance.  Stage piano outputs have an output impedance.

Quote
I have several amp heads, 1 tube and 3 SS, all with 1Meg input impedance, and all are dead quiet.

As do I.  But guitar amps cut off at about 5K because guitars don't do any higher, so that 5K upper limit is filtering off the noise.

The big difference is the OP wants to record his Rhodes without a guitar amp and direct into a recorder, which is full bandwidth out to 20K where the noise will now be clearly heard.

In my experiments with various DIs and amps, the pickups on the Rhodes are very sensitive to loading from input impedances.  Another member here on EP forum graphed the frequency response of the pickups with varying input impedances and it is very revealing, pretty much mirrors my results.  Their tone changes, and the noise varies.  The pickups seem to be happy with an optimal input impedance.

Actually, I'm not confusing input and output impedances.  The impedances of the suitcase pianos I referred to are the input impedances of the preamp circuitry they used, not the output impedance of the harp.  Sorry if my writing wasn't clear.  As for amp frequency response, all my amps are flat out to beyond 10 kHz, and not more than 2 or 3 dB down at 20 kHz.  A Rhodes piano doesn't put out much signal beyond 5 kHz or so, anyway.

In a double-blind test, properly set up, I claim that no one would be able to distinguish any tonal or noise difference between a preamp having an input impedance of 1 meg ohm and 10 meg ohm.  Also consider that the capacitance of the cable that connects the harp to the preamp of choice filters out some highs.  If we assume a cable capacitance of 200 pF, which would account for the cable from the harp to the front panel, and the front panel to the preamp, the impedance of that capacitance at 10 kHz is about 79 k.  That impedance, along with with the fairly low output impedance of the harp, makes it's just a bit hard for me to accept the idea that anyone could hear a difference between 1 and 10 meg ohm preamp input impedance.  I simply don't believe it.  There could be any number of reasons why the Countryman sounds better.
6
The Wurlitzer Electric Piano / Re: Wurlitzer leg paint color
« Last post by pianotuner steveo on Today at 07:22:40 AM »
Rhodes brand. Lol

7
I am 99.99% sure that 10Meg input impedance is not the reason for the quietness of the Countryman DI.  All versions of the stage piano have input impedances at least 10X lower than 1Meg.  I have several amp heads, 1 tube and 3 SS, all with 1Meg input impedance, and all are dead quiet

hey there! would you mind sharing a clip of your rhodes with the highs boosted. Ive already thrown money at several boxes with no improvement. and before i spend money on the countryman it would be nice to hear yours! thanks
8
The Wurlitzer Electric Piano / Re: Wurlitzer 200 amplifier noise
« Last post by John Steel on Yesterday at 04:52:11 AM »

Thanks for your reply Electrickey - That's also great advice. I think I had better invest a high quality iron! Best wishes John.

John if you can, use a good grade of solder. The Wurli deserves the TLC.

Cardas brand gets a lot of thumbs up for audio, easy to flow. It is available in the UK.




You can get 100 gram spools as well. It's a meld of silver, copper, tin & lead.

Or a 3m length sold by xaudiodesign on eBay for about 5 pounds.

https://www.ebay.co.uk/itm/CARDAS-QUAD-EUTECTIC-SOLDER-3m-length-Silver-Copper-tin-Lead-Rosin-core/112317914369?hash=item1a26ab5d01:g:JEAAAOSwjMJXCORu




Thanks again Electrickey - It hadn't occurred to me that the type of solder would make a difference!
9
The Wurlitzer Electric Piano / Re: Wurlitzer 200 amplifier noise
« Last post by Electrickey on Yesterday at 12:56:38 AM »

Thanks for your reply Electrickey - That's also great advice. I think I had better invest a high quality iron! Best wishes John.

John if you can, use a good grade of solder. The Wurli deserves the TLC.

Cardas brand gets a lot of thumbs up for audio, easy to flow. It is available in the UK.




You can get 100 gram spools as well. It's a meld of silver, copper, tin & lead.

Or a 3m length sold by xaudiodesign on eBay for about 5 pounds.

https://www.ebay.co.uk/itm/CARDAS-QUAD-EUTECTIC-SOLDER-3m-length-Silver-Copper-tin-Lead-Rosin-core/112317914369?hash=item1a26ab5d01:g:JEAAAOSwjMJXCORu

10
The Wurlitzer Electric Piano / Re: Wurlitzer 146 noob thread
« Last post by conke on August 14, 2018, 11:37:50 PM »
@Paleophone,

Thanks for all of the help. I separated the piano and amplifier to work on electrical repairs, and unfortunately was unable to dig out the piano again before leaving for college. I'll be sure to get you more pics and stamp codes, but it will probably be a hot minute.
Pages: [1] 2 3 ... 10