The eTap2hw DSP code is presently at OCT-Distribution to batch program the FV-1 based daughter boards. The ordenumber already allocated is: SKRM-C8-ETAP2. The pricing is the same as the other SKRM versions presently listed on the OCT-Distribution.com website.

The vendor here in the Netherlands, “Newtone-Winkel “ with a web store, is presently in the process of ordering sufficient motherboards from a factory in Germany. They did get a small order already in to check if the boards are of the required quality and now are starting to order larger batches.

The motherboard with components excluding the SKRM-C8-ETAP2 board is already available through them, although in low quantities, under order number: BPOSFV1 The cost of this motherboard&components kit is 33 Euro excluding shipment cost.

When the ordered pre-programmed OCT boards are received by this Dutch vendor, the complete kits are then ready for shipment. It seems  now that it’s only a couple of  weeks before the ordering fulfillment can be started. As an extra service Newtone will stock also BCD switches. they need to be ordered separately. Obviously, potentiometers, enclosures, connectors etc can be also ordered through them. Eventually it’s foreseen that a complete kit, including enclosure, will be offered.

The list with pre-orders is now forwarded to the vendor for further processing pending availability of both SKRM-C8-ETAP2 and BPOSFV1

The announcement of the availability of complete kits will be reported here including details to order.

Piet

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In most cases the POT1, being a potentiometers, is only used as a switch. Positioning the switch at, or around positions, A – B – C – E – F (see picture below) is switching to a particular head configuration setting. The choise of using the letters ABCEF is based on the same selections made on the Meazzi Echomatics although the ‘D’ is left out as it did not add any value to the patterns.

In 3 other emulations this potentiometer is used for volume control (Echomatic2 head 4), speed control (Roland 301) or tremolo frequency.

When switching with a potentiometer is not fully appreciated it is rather simple to produce a 5 position switch where  a resistor ladder network of 2x 1K and 4x 2K resistors is constructed like:

[GND] 1K (A) 2K (B) 2K (C) 2K (E) 2K (F) 1K [+3.2V]

The picture shows a switch configured as per description above.

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Presently the  daughterboard vendor is tooling-up the special unit and the vendor of the kit is in the process of ordering quantities motherboards and the special OCT pre-programmed daughterboard. Next monday 22/4/2012 I’ll send the pre-orders to Newtone already who will contact them individually.

I’ll take here the opportunity to express a big thank you to the pre-beta tester PeterN and the ‘early adaptors’ PeterN, Roger,Barry,Johan,Lars and Dick  working closely with me getting this in a working fashion. We needed many iterations and refreshing the EEprom’s with improved code before a ‘go’ was finaly given!

Thanks guy’s!!

Piet

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In the graph below the maximum deviation is +2.8Hz/-5.7Hz = 8,5 Hz

When we use the difference between  tone ‘A’ @ 440Hz and tone  ’B’ @ 494 Hz the delta is 54Hz. There is a rule in the music world that 20% of the distance between a note is regarded as ‘out of tune’. In this particular measurement this would be .2 times 54Hz is 10.8 Hz and is ‘proof of the pudding’ that this W&F is below that treshold from about > 700 Herz upwards. As around 1Khz is the recommended center frequency of the guitar characteristic  this would be wel within boundaries .

Obviously the choice of the selected (ultra) low  frequencies to mimic W&F is directly related to the tape/disc speed (mostly 15 IPS) and the diameters of the rollers and capstan including the frequency of the motor. in most cases 3 variables are used to provide for an acceptable W&F. When, as an example the Alesis Q2/A20 family cannot cope with 3 W&F variable the sum/difference of two variable are then chosen where the possibility of phase dependancies is minimized.

Piet

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Most guitar players are not aware of the fact that about 70 tracks of the Shads can be  played using the Echomatic II disc echo and only 10 require the basic Echomatic I disc echo’s ( models ‘J’ and ‘F’). On the Echomatic II unit there is on group of 3 heads controlled by one amplitude controller (potentiometer) and a 4th head also controlled by a potentiometer. The standard amplification difference measured by 100% amplitude is resp. 0dB, 0dB,-2dB and -2dB. Summing this results in 5.135 dB.

To obtain a more emphasized pattern the first head could be lowered -2dB to -3dB so the pattern stand-out more as the first head’s contribution in time is close to the reverb domain (<100mS) this would provide a more ‘dry’ echo pattern that, due to the energy level, could absorb more sustain.

The energy difference with  ’standard amplification’ is -3dB,0dB,-2dB,-2dB resulting in 4.41 dB summed together. The difference is therefore 5.135-4.41 equals -0.725 dB that would be upped resulting in a longer delay.

A good example is foot-tapper making it even  questionable if the first head is part of the set of 3 heads. In most cases the first head should therefore be lowered in amplitude deviating from the ‘standard’ being -0dB.

The Echomatic II classic  emulation in the eTap2hw is kept according the ‘standard’ but the bank with 5 patches is deliberate adjusted down a couple of dB’s so the pattern is more vividly available. when this is not sought after the user can fall back to the Echomatic II classic. The summing of the heads is kept intentionaly  as in the classic ‘resistor’ configuration. No factor adjustments are implemented to guarantee headroom space if -0dB’s are summed.

Piet

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In the table below I’m presenting two ways controlling the dry/wet audio streams. The green area is related to dry being not changed from the input (set to 50% processing amplitude) and wet added later to that audio level. It’s clear here that for each head configuration the dB values are different making the control of the dry/wet ration problematic. however, on the positive side this is also providing a (50%+50%) amplitude making signal/noise ration minimal.

Another approach (blue colored) is to balance dry/wet where the mid-point would become our 0dB value. Obviously when dry is already set to 50% this mid value’s amplitude becomes (50% / 2) making the signal/noise ration worser but the energy out at each setting will be close to equal although the ’0′ point would change per head configuration around 2 dB.

Calculating dB values while designing effects is a daily activity. On my blog is a link with a very nice set of tools that can be used to calculate the impact of dB’s and or the calculation of voltage to dB’s etc.

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The feedback heads timings are based on two semiquavers, a quaver rest,then two (quieter read feedback) semiquavers again on the second beat of each bar. The BPM could be 120 bmp but 134BPM seems to be correct. (source: ‘Total guitar issue 33 1997)

In calculations this would result in: 1 note = 1, quaver = 0.125,semiquaver= 0,0625,demisemiquaver=0,0313 and hemidemisemiquaver= 0,0156

This results in head times@120BPM  500,250,125,62,5 and for the head times@134BPM 445,222,111,56

With an Apache pattern being: one head 111 mS and one head 445 mS with repeats taken from the last head.

This 500@120BPM or 445@134BPM is not part of any Meazzi timing I know so a dedicated patch with above pattern will be added. This approach also leads to the point of a special emu with BPM as the driving factor to create a pattern as was done in the eTAP2 VST module.

A article in ShadFax written by Alan Jackson clearly stated that the ‘F’ version was with variable speed and head amplification not as per spec. In some cases the first head was much less amplitude wise then the second head or the other way around. The thirty head was in most cases not switched-on at all. I’ve checked the BPM requirements and noticed 138bpm the highest in most of the fora. When 120bpm is nominal my take is that using fast/slow speeds the ratio should be 140/100. In the model ‘F’ 2speed this is implemented in 2 different patch modes.

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The first group of Echomatic-I classic  emulations are all with a dry/wet control and the middle potentiometer/switch controlling 5 different configurations. The lettering is obtained from the early Meazzi’s ABCDEF but ‘D’ is taken out as it’s a ‘dummy’ configuration leaving 5 different configurations for each Echomatic-I.

The next group of (2) Echomatic-II Bank preset emulations are with the same user interface as each particular setting is a different patch. The echomatic-II bank 1&2 are created to make switching to a ‘assigned’ patch an easy process while accuracy on there patches stays fixed. In the classic version however, the user can adjust to his own liking.

On the Echomatic-II  classic the story is slighly different, the offering is the Echomatic-II classic where heads are controlled by the first two controls. Here dry/wet is the product, or balance, between the dry signal and the dB values of the heads. The first control takes heads 1&2&3 together while to second control head 4.

The Roland R301 is offered in a mode 5 only and are featured with a vary speed as per Roland spec. This varspeed is controlled by the control in the middle.

To accomodate for the Nivram lovers a reverb with added tremolo that can be set to no tremolo is added to compliment the suite of offerings.

The last emulation is a reverb were the user can decide also to add tremolo and tremolo depth.

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——–

“Engineers and musicians have long debated the question of tube sound versus transistor sound. Previous attempts to measure this difference have always assumed linear operation of the test amplifier. This conventional method of frequency response, distortion, and noise measurement has shown that no significant difference exists. This paper, however, points out that amplifiers are often severely overloaded by signal transients (THD 30%). Under this condition there is a major difference in the harmonic distortion components of the amplified signal, with tubes, transistors, and operational amplifiers separating into distinct groups.

Author: Hamm, Russell O.
Affiliation: Sear Sound Studios, New York, NY
JAES Volume 21 Issue 4 pp. 267-273; May 1973 ”

————-

here the article

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The assembly is based on two main components of with the daughterboard is ready and programmed and just needs to be inserted into a 2×8 header connection. The motherboard is developed by me and manufactured in Germany as a 2 sided PWBA including shielding. All components on this board are sourced to be exact in value’s and fit. There are no clearance issue on the board.

It is highly recommended not to source your own components to avoid fit/function conflicts.

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