Dallas Arbiter - Tremface

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Re: Dallas Arbiter - Tremface

Postby lolbou » 27 Feb 2010, 23:15

Bernardduur wrote:It measures 99k; can't measure the capacitance.


Desoldered for measuring?
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Re: Dallas Arbiter - Tremface

Postby Bernardduur » 27 Feb 2010, 23:17

lolbou wrote:
Bernardduur wrote:It measures 99k; can't measure the capacitance.


Desoldered for measuring?


Both; no difference
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Re: Dallas Arbiter - Tremface

Postby lolbou » 27 Feb 2010, 23:34

:scratch: Je passe...
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Re: Dallas Arbiter - Tremface

Postby analogguru » 28 Feb 2010, 09:10

Bernardduur wrote:
lolbou wrote:
Bernardduur wrote:It measures 99k; can't measure the capacitance.


Desoldered for measuring?


Both; no difference


Now... Do you have a variable voltage-source up to 40 V ?

Then take a 100k-resistor in series with the mystery component.
Connect one side of this to V+, one to V-.
Turn the voltage to 5V - at the connection should be read approx. the half voltage, 2,5 V.
Now dial the voltage up in 5V steps and measure the voltage.

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Re: Dallas Arbiter - Tremface

Postby Bernardduur » 28 Feb 2010, 12:58

analogguru wrote:
Bernardduur wrote:
lolbou wrote:
Bernardduur wrote:It measures 99k; can't measure the capacitance.


Desoldered for measuring?


Both; no difference


Now... Do you have a variable voltage-source up to 40 V ?

Then take a 100k-resistor in series with the mystery component.
Connect one side of this to V+, one to V-.
Turn the voltage to 5V - at the connection should be read approx. the half voltage, 2,5 V.
Now dial the voltage up in 5V steps and measure the voltage.

analogguru



Wierd thing is that now it measures 3.17M desoldered.......

weird! Maybe I measured it wrong last night.

Now that it is light I notice a color-band signature. It is orange - orange - grey or red - red - grey
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Re: Dallas Arbiter - Tremface

Postby lolbou » 28 Feb 2010, 13:43

VDR have high impedance DC wise... Since the ohmmeter measurement rely on DC current, this value appears more appropriate to me for a VDR.

Can you carry out AG's experiment to check for any linearity (with a 3.3M resistor instead)?

The two orange could give the "3.3", but grey ain't a multiplier AFAIK (should be yellow)... :scratch: :scratch:

Any pic of the device?
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Re: Dallas Arbiter - Tremface

Postby Bernardduur » 28 Feb 2010, 14:57

I can only go to 15V

5V -> 3.27V
10V -> 7.38V
15V -> 10.9V

Pics come later! I added a charge pump to the unit as the owner wants it to be powered by a simple power supply. Now I'm gonna add the input buffer as mentioned on GEOFEX and see what happens.

Image

Link to the project

In the whole GEOFEX project there is no word on changing the R7 (resistor parallel to the FET) to 2M2 (from 220k). What is the effect of this?
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Re: Dallas Arbiter - Tremface

Postby R.G. » 28 Feb 2010, 16:05

Bernardduur wrote:Only weird thing is a 'cap' to ground on the input that has no other bearings then 27V; 10mA

From the marking, maybe it's a varistor, as ag notes. One thing's pretty sure - if it measures over 100K and does not show measurable capacitance, it's not going to affect the sound much. This matches the idea that it's a protective device. You want protective devices NOT to change the sound.

A very simple thing to do to tell what changes it makes to the sound, if any, is to lift one leg of it and install a switch. Now play, and have a friend flip the switch. If you can hear no difference in sound, there's not a huge difference to be made by knowing what that component is.

Bernardduur wrote:In the whole GEOFEX project there is no word on changing the R7 (resistor parallel to the FET) to 2M2 (from 220k). What is the effect of this?

Let's think. The parallel resistor and JFET, in series with the depth pot, form the lower resistance of a voltage divider with the input signal. The top resistance is the series 10K. The JFET can vary in resistance between almost an open circuit, and maybe 1K. The depth pot can vary from 22K to zero.

If the JFET is open circuit, then the divider is effectively made of the 10K series resistor as the top resistor and for a bottom resistor, the 22K pot plus either 220K or 2.2M to ground, both in parallel with a 100K. So the difference is that the signal is divided by 10K and either 220K parallel with 100K, or 2.2M in parallel with 100K. In the first case the signal loss is 1.1db, in the second -.81db. Since it is quite difficult to hear differences of less than 1db, the difference between the two of 0.29db would be almost inaudible.

Another way to look at this is that the minimum depth is reached when the 22K depth pot is 22K. Both 220K and 2.2M are very much larger than the 22K value of the pot, so they should add (or subtract!) subjectively nothing to the sound.

So the effect of changing R7 from 220K to some bigger value is - very nearly no change at all.
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Re: Dallas Arbiter - Tremface

Postby Bernardduur » 28 Feb 2010, 16:10

Tnx!

Adding a switch to the 'cap' and switching results not in an audible difference.

Only downside now is a slight volume loss......
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Re: Dallas Arbiter - Tremface

Postby R.G. » 28 Feb 2010, 17:40

Bernardduur wrote:Tnx!
Adding a switch to the 'cap' and switching results not in an audible difference.

You can do the same thing to see if there's an audible difference with the 220K/2.2M. I would not expect much, but maybe some people with good ears could hear it. It's a good trick.
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Re: Dallas Arbiter - Tremface

Postby Bernardduur » 02 Mar 2010, 00:14

R.G. wrote:
Bernardduur wrote:Tnx!
Adding a switch to the 'cap' and switching results not in an audible difference.

You can do the same thing to see if there's an audible difference with the 220K/2.2M. I would not expect much, but maybe some people with good ears could hear it. It's a good trick.



No difference :D



Must say that this pedal is AWESOME! I haven't heard a tremolo pedal that sounds so great as this. Not very versatile but a huge range and a great depth.

I love it!
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Re: Dallas Arbiter - Tremface

Postby silverface » 02 Mar 2010, 10:49

Bernardduur, I see a few more differences in your and RG's schematics:

R7 (2k2) vs R12 (22k)
R8 (1k5) vs R11 (15k)

Typo's?
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Re: Dallas Arbiter - Tremface

Postby Bernardduur » 02 Mar 2010, 11:39

silverface wrote:Bernardduur, I see a few more differences in your and RG's schematics:

R7 (2k2) vs R12 (22k)
R8 (1k5) vs R11 (15k)

Typo's?


Hmmmmmm, or the band red vs orange is hard to read or they are that. I didn't look that hard at RG's schematic. I'll check it later!
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Re: Dallas Arbiter - Tremface

Postby orpheumlover » 02 Mar 2010, 11:44

Must say that this pedal is AWESOME! I haven't heard a tremolo pedal that sounds so great as this. Not very versatile but a huge range and a great depth.

I love it!


I had problems building mine this past summer but it works great now thanks to the patience, guidance, and asssistance from RG!! In my opinion it sounds very "rubber band-like" with an elastic "boinging" to the tremolo. It's great and as you said, not very versatile but what it does do is have its own "character". The Trem Face and the Colorsound Tremolo are very British sounding, not at all "surf-like". I have a sound clip/video that I did of it that will soon be up and on YouTube. (Gotta do some editting.)

Good luck with your Face!
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Re: Dallas Arbiter - Tremface

Postby R.G. » 02 Mar 2010, 15:23

It might be useful to effects hackers who do not insist on exact part-for-part "originality" to mod the TF further.

The trem-face is a down-only tremolo, meaning it only subtracts from the original signal to make volume variations. There are (obviously) three kinds of tremolo - down-only, up-only, and up/down. Down-only causes the tremolo'ed signal to be apparently less loud than the dry effect sound. Up-only is not all that useful. The good one is up/down.

You could get up-down from the TF by adding a booster that boosted the signal level out of the effect by a similar amount to the amount lost through the effect by using a dual knob for depth and letting the second section increase gain in an amplifier as depth increased. This would compensate for the losses and give a more even loudness level with/without effect.

... some design work is required here :D
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Re: Dallas Arbiter - Tremface

Postby Bernardduur » 02 Mar 2010, 16:24

R.G. wrote:It might be useful to effects hackers who do not insist on exact part-for-part "originality" to mod the TF further.

The trem-face is a down-only tremolo, meaning it only subtracts from the original signal to make volume variations. There are (obviously) three kinds of tremolo - down-only, up-only, and up/down. Down-only causes the tremolo'ed signal to be apparently less loud than the dry effect sound. Up-only is not all that useful. The good one is up/down.

You could get up-down from the TF by adding a booster that boosted the signal level out of the effect by a similar amount to the amount lost through the effect by using a dual knob for depth and letting the second section increase gain in an amplifier as depth increased. This would compensate for the losses and give a more even loudness level with/without effect.

... some design work is required here :D


Hmmmmm, I just really like the tremolo for it's down only character. it sounds so choppy, almost like a vibe unit. Great! Love the huge speed-spread you get on this one; you can get really slow and go super fast. Love that!

Don't know if I would love to have it altered in a way........ but hey, maybe the improved version sounds even better :D
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Re: Dallas Arbiter - Tremface

Postby Xplorer » 26 Sep 2011, 03:42

hello !

well, i couldn't make this trem face to work last year but i decided to take a look again now. But now i remember these things i can't undertand.

does anybody has a synchronised layout and schematic please ?
cause i don't see the links between these. for example, only two transistors on the corrected layout, and three on the schematic. i don't see R5 and R7 on the schematic, i don't know what CX is ........ etc etc. i don't know what to follow in the end.
so i'd be sure to make mistakes.

does anyone has a working trem face clone that could be perhaps shared here please ? i'd love to have mine working ; )
please ! some working layout/schematic connected together ! :hug:
Thanks !
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Re: Dallas Arbiter - Tremface

Postby orpheumlover » 28 Sep 2011, 21:30

Check this out.

Link


This is a good example of the Trem Face pedal. He gets a little carried away with the added Fuzz Face but the Trem Face is very well represented. Mine sounds nothing like this one...it is too "boingy" and elastic band sounding. Guess I will have to tear it open again and check it out. If the fellow who did this is on this board, I salute him. This is almost a true sine wave tremolo, but not quite. I like this effect quite a lot.

Enjoy!
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Re: Dallas Arbiter - Tremface

Postby Xplorer » 28 Sep 2011, 21:44

please Toddy, can you post some pictures of your trem face here ? that would be cool.. i have no clue to do mine properly. do you have a layout of yours ? those at geofex aren't working for me, many questions ... layout and schematic of the original trem at geofex are different, and they both have some parts not explained, not cited. CX ( ???? ) , R5 and R7 not appearing in the schematic, etc etc.
Thanks !
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Re: Dallas Arbiter - Tremface

Postby R.G. » 28 Sep 2011, 22:42

Xplorer wrote:please Toddy, can you post some pictures of your trem face here ? that would be cool.. i have no clue to do mine properly. do you have a layout of yours ? those at geofex aren't working for me, many questions ... layout and schematic of the original trem at geofex are different, and they both have some parts not explained, not cited. CX ( ???? ) , R5 and R7 not appearing in the schematic, etc etc.
Thanks !

Several people have built tremfaces from the geofex articles. What in particular has you confused?

The original schemos and layouts were confused, and the article shows some of the history on how that got corrected. Cx is unknown, and successful clones have been built without it being there at all.

So can you list specifically what you're trying to build from that article and what questions you have about it?
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