Voltage Control Lags With TMax

Hello,
Is there a quick fix for the slow response of voltage controlled devices when using the TMax?
I thought that I saw a post from KKissenger about this problem somewhere on Theremin World, but, alas Theremin World has no search engine in MozFireFox.
UH-OH!!
Thanks,
Dave

To get the lag out of your Pitch CV try the following:

1) Remove C24, and
2) Replace C21 (10uf) with a 5uf electrolytic capacitor

K. K.,
Thanks for all the mod info. I switched the Capacitors as you suggested, and it works great!
I have also put a 10Kohm resistor across your suggested resistor point at the the pitch oscillator, and the PAIA suggested mod point as well. Both mods can be switched in and out with micro-mini STSP's from the front panel. These mods give one quite alot of tonal choices. The PAiA mod does not limit the pitch range,(at least on my TMax), The KKissinger mod limits playability to about three octaves or four octaves, (at least on my TMax).
{A Side Note: Any Kit Theremin is dependent on the case that it has been installed in, and the environment that it is played in. I play my TMax on my coffee table in my living room. My playability range is greatly limited by the proximity of organic substrate.}
But, I can enjoy the designed TMax tone and range whenever I want with a flip of a switch or two and then nulling again.
Good Luck!
teslatheremin

Congratulations on your great idea to switch the coupling in and out of the circuit. You really are getting the best of both worlds.

Would be very interested to hear audio samples (or your performances) that demonstrate the different mods.

-- Kevin

teslatheremin:

is there anywhere (links or another thread) that elaborates on these mods that you made? KK's CV mod was easy enough to follow, but I would prefer to do as you did and allow a switch to enable higher tonal/pitch range if possible. Didn't quite understand what you did from this description though... did you actually replace the capacitors as suggested? What are the "PAIA suggested mod points" you are referencing?

I am building a TMax w/ MIDI Fader and would like to avoid this CV lag if at all possible.

"K. K.,
Thanks for all the mod info. That one works great!
I have also put a 10Kohm resistor across both your suggested resistor points at the the pitch oscillator, and the PAIA suggested mod points. Both mods can be switched in and out with micro-mini STSP's from the front panel. These mods give one quite alot of tonal choices. Both mods limit the pitch range,(at least on my TMax), to about four octaves. But, I can enjoy the design TMax tone adn range whenever I want with a flip of a switch or two and then nulling again.
teslatheremin"

guru20,
Hello, and thanks for your interest. Many mods are available for the T-Max, and I think that I have inserted most of them in my T-Max. But, others come before me to whom I must pay tribute: Kevin Kissinger and PAiA's 'Excellent' Scott.

Kevin Kissinger is extremely well versed on the available modifications to the T-Max. He has a great mod post devoted to the T-Max somewhere in ThereminWorld. I will look for it and link it here.
http://www.thereminworld.com/forum.asp?cmd=p&T=169&F=10

PAiA has an excellent mod page for the T-Max available in the PAiA website. (As does the excellent PAiA service representative, Scott. Fire off a letter to Scott, he aims to please.)
The crux of the coupling mods has to do with soldering one end of a 10K resistor at a certain point on the parts side of the board, soldering a wire to the free end of the resistor, soldering the end of that wire to the middle lug of a SPDT micro-mini switchthat has been installed into the frony panel of the PAiA printed front panel. Then, solder another wire to one of the outside lugs of the micro-mini switch and solder that wire's free end to the appropriate point on the parts side of the circuit board.
Kevin Kissinger's circuit board points are R6 and R11 on the side of the resistors closest to the tuning lugs,(inductors). PAiA's circuit board points are R4 and R9 on the side of the resistors closest to the tuning lugs,(inductors).
K.Kissinger's coupling circuit board source points and PAiA's coupling circuit board source points are not the same, hence many more tonal options-- albeit, with some range resrictions as a trade-off. I have one switch to utilize Kevin's suggestion and another to use PAiA's. I can use them both at the same time, or choose neither, and let the original milky smooth T-Max timbre speak out.
PAiA, also has a mod to boost the Sqare wave timbre. One may use the SPDT switch idea to switch in and out of the T-Max design timbre to the mod as well. Kevin also has thoughts on this.
Also, I have some thoughts on the implementation and positioning of the Midi-Fader board, but will save that for another session.
The T-Max is a great kit! Good Luck, guru20!
teslatheremin

Thanks for the quick and informative response! I had seen some of the mods on the PAiA site (one was for a more "original RCA" type sound)... though it seems like the site was updated from a year or two ago, and contains much less information than it used to.

Although I would love to have the choice for a variety of tones, I will likely do as little modding as possible to make sure I don't kill it or do something regrettable -- though I do plan on using it as a controller, so wanted to try to do that. And if I do mod it, I definitely want to maintain the ability for the "original" unaltered sound, which is why I asked. The Square-boosting could be very nice, as well (is this the RCA tone? the RCA wave doesn't sound super square to me -- much more sine -- but I could be wrong)

I am quite a novice at all of this (have some experience with MIDI and synths and such, but not with building my own electronics, though I did get a degree in Comp. Sci. and worked a small bit with breadboard circuitry, but I am no electronic engineer for sure)

guru20,
The PAiA coupling mod is the closest to the RCA sound that you will probably get out of the T-Max.
I have a Midi-Fader board installed on my T-Max.
It took alot of futzing to get it to work as a tradition Pitch/Volume Theremin controller--- which is what I personally wanted.
If you want my thoughts on that, you can shout at me when you get to that part of your project.
I have asked a few times here at ThereminWorld if anyone Midi-fied a T-Max, and got no response.
teslatheremin

This is guru20 (different account because I lost my old email) -- thanks for taking the time to answer some of my questions. I'm getting ready to start soldering together the Tmax today, coming online first to get some ideas about mods so I can keep those in mind as I go. It sounds like you have really built a quite dynamic Tmax. Sounds awesome.

and kkissinger has 557 posts?? Holy crap. I think I will just search the forum for "kkssinger" and fill my brain with knowledge until it bursts.

teslatheremin:

I have a Midi-Fader board installed on my T-Max.
It took alot of futzing to get it to work as a tradition Pitch/Volume Theremin controller--- which is what I personally wanted.


Yes, this is exactly what I'm looking to do. Could you share what you did? It does seem a bit cryptic for how to get it to work as a CV-MIDI converter, though the PAiA website specifically says it can be done (just not how)

Would you recommend switching from Velocity Gate to Volume Gate as outlined on the PAiA site?
http://www.paia.com/ProdArticles/therefaq.htm#drift

I think I am going to do what you had done and have some SPDT switches for mixing and matching mods. I'm thinking: one for the velocity/volume gate; one for the 10k resistor for coupling the pitch and getting a more saw-wave RCA tone; and then one of the kkissinger ones he had mentioned.

I also plan on removing the .005 disc as suggested by PAiA for more dramatic square timbre (if I change the timbre, I really want it to change noticeably, not tiny amounts)
Finally, I will probably do the kkissinger mod mentioned about for getting out the pitch lag (which will be important if I use the MIDI fader)

So... looks like 3 switches, a couple additional resistors, two removed capacitors, and one capacitor replacement are in order. And please, if you get a chance, post anything you can about sending CV-MIDI control changes through TMax...


thanks!