Variable echo times from fixed-motor reel-to-reels

Some reel-to-reel recorders do not have DC-driven motors and as such aren't easy to make into something with variable speed, hence variable delay times when set up to do echo. Others do, but you might not want to mod them.

Place a musical-sounding digital delay (Lexicon LXP-5 and others) at the input and route/mix the return/feedback into its input. Viola, variable-delay tape echo =character=, but the feedback will sound a bit different and you won't be able to do analog delay time modulations. Digital distortion also of course factors in so a limiter at the input might help.

Please to experiment.

A bit more vintage from your JH Living VCOs

JH: "I've never heard better drones than from three EMS VCOs running at almost the same frequency, and beating against each other in an ever changing pattern."

I've owned VCS 3s and Moog Modulars, and the early Moog oscillators, drifting away, outdo the EMS for a musically interesting varying tone. I don't mean out-of-control, but as he implies, something that is pleasing to hear.

If you want "more" of that from your LVCOs, consider installing a switch for the oscillator core capacitor, as the EMS (and even the Moog 901b) utilize vintage Mullard mylar capacitors, not polystyrene/polycarbonate.

C3, 2.7nf, is the polystyrene core capacitor, yes?

http://tinyurl.com/4fajblg

How to? This applies:

"Ideally, each Oscillator should have the two capacitors on the pcb joined at the current input end, to keep this sensitive point a short path. Fly a screened twisted pair cable wired to the other end of each capacitor to a panel switch such that it switches the larger capacitor in parallel. Ground the screen from a nearby panel control. "

http://www.hinton-instruments.co.uk/ems/emsmisc.html

"I've chosen the same noisy 4-transistor exponential converter that EMS used in the VCS3. I'm not overly scientific about it - I just like the sound of it."

Then why change anything at all about it if it sounds good as it is/was?

Adding the less-accurate cap may increase liking the sound of it- it's up to you. I remember Dean Hinton's original EMS mods page mentioned that its lowly vintage power supply had something to do with the "bad" behaviour of the instrument; you may wish to use a less-than-Kosher power supply to help regain the desirable character...I also note that when I sampled a VCS3 all those years ago, that the tip of each sawtooth waveform had a different overshoot, meaning that each cycle was slightly different. I don't know how that will turn out at audio frequencies but it has to be yet another aspect of Difference from the modern. I don't know how to re-create this, or if it is the same on all EMS oscillators. (I posted this at TGS many years ago; someone took my statement incorrectly, imagining that I meant that I could somehow hear each wavecycle at audio frequencies, and differentiate them...certainly not the case, but you can see the difference in a sample. I'm not sure about the cycle-to-cycle homogeny of the LOs, but it's worth considering.)

You may want to make sure that it has the same exponential .32V/Octave response (or so) for deep exponential FM.

Also, part of an interesting drone/its overall interesting character may be Oscillator 3. It doesn't, in the several images I've seen online, have 2C746 matched, single-housing trannies, which aid in heat transfer/stability. The 2N5172 pair which appear to be used in its core instead of the 2C, are sometimes (perhaps always) epoxied together without heat-transfer compound. This may produce more drift than the same oscillator with a 2C746 or other matched, single-housing pair.

"Back to the crow, back to the stone age!" -March Violets. Yes, I'm suggesting that on at least one of your LOs, that you install a matched but heat untreated pair. All of your oscillators don't have to sound like a bomber squadron, but one with a bit more drift will increase interest and perhaps get you closer to what sounds good about the original. Consider two-oscillator patches and use the third oscillator for FX. Sometimes, use all three for the different character. The Minimoog is also set up in this manner, however its Oscillator 3 is likely (haven't looked) of equal stability as the first two.

You can also put the Tempco resistor on a switch, DPDT, to select between it and a resistor of the same measured value but standard carbon comp or metal film. See the above link and considerations per switching core capacitors.

But of course, just ignore me; no one actually likes those old instruments or why they sound and act the way they do.

And to those who leap to fear any time I discuss the facts as I am learning them, get a life. Just get a life.

Loudspeaker design is an art and a science.

By Michael Fremer • Posted: Apr 18, 2004 • Published: Apr 1, 2004
"Loudspeaker design is an art and a science. Anyone who tells you it's only one or the other is probably building or listening to some awful-sounding speakers. Design a speaker in an anechoic chamber for the "theoretical" world, and there's no guarantee it will sound good in the real one. Even building a speaker that excels at "real-room" measurements doesn't guarantee that it will sound all that convincing when reproducing music. We can't measure everything, and what we can measure can't be reliably ranked in terms of what's important to most listeners."

http://www.stereophile.com/floorloudspeakers/404aerial/

CD/DVD Player Oversampling DACs

I had purchased a Sony CDR-375 due to having seen a plug about its character...it definitely has a crystalline top end, smoothed midrange, and an overall strangely shifted character. I noted that it has a 4558 op amp in the output, which is old and slewy (which is great for certain things). Definitely not a "wide bandwidth/clean" opamp, for program purposes...

This machine must be oversampling. I've since acquired a few older Sony CD players, and note timbral differences, with the 1993 unit being pretty honest (but a bit gritty in the top).

Discussion in the DIYaudio.com fora pointed to oversampling as the culprit. Two to four-times oversampling seems to shift upwards the overall spectrum, due to increased timbral density. Even congas and female voices seem to have a slightly higher fundamental (or the energy is upwardly shifted due to new overtones??). I found that this messes with the balance of a drumset (real or electronic). Dead Can Dance's "The Fatal Impact" has a nice balance between synth conga and synth kick drum, a nice, stumbling dread. I did not enjoy how it changed on an oversampling machine. I tap my toes and move a little to this beat, I like it a lot; don't mess with it, don't change the original intent of the music.

I note that some things benefit (the guitar and overall "snap" of Diana Krall's wonderful "Live in Paris"), but other things do not, as might be concluded/expected. C-Tec's "Cut" will peel the skin and hair from your face and skull. You didn't need that anyway.

One DIYer posted that a friend brought over a CD of his drum playing. Upon hearing it on the other system, he stated bluntly (and truly), "That's not my drumset." The DIYer had a setup allowing for the selection of sample rates, and upon selecting 44.1/16, the player was satisfied. I will surmise that this is the rate and depth at which it was originally recorded, etc.

Some players have SPDIF and optical out, allowing the use of external DACs; some of them are specifically non-oversampling, yet are capable of it with additional hardware (the OPUS from twistedpairaudio.com), and sport the most modern converters with truly extreme specs. Because it's DIY, you can find out for yourself.

www.diyaudio.com

Salt reveals resonance patterns in 2d-material

http://www.youtube.com/watch?v=Uu6Ox5LrhJg

Transmission Line Loudspeakers

Such as from IMF and Fried.

Yes.

Multi-channel "Surround Sound" amps

are a perfect way to use your stereo signal and still have two amps for two subwoofers. You may have to use your CD player's headphone out into the amps inputs, but there it is.

BASS!