Tag Archives: audio

Yamaha NS-10 reborn, Avantone Drop-in Replacement Tweeter

Yamaha NS-10 reborn, Avantone Drop-in Replacement Tweeter

It was long my Yamaha NS-10 monitors had both tweeters dead, I love these speakers so much that I was costantly thinking on fixing them, but didn’t want to spend a fortune. Unfortunately, the blown tweeter is a very common issue with these monitors and as the NS-10 remains an indispensable tool for lots of people, the original tweeters are still in high demand. As the NS-10 speakers are no more in production that is long already, finding parts was getting pretty hard and the originals, reached very high prices. This is the reason that forced me years ago, to buy a pair of Yamaha MSP-5, monitors that I love very much, but that are not “my” NS10s.

Last week, with great surprise I discovered that Avantone Pro, the company of those classic tiny monitors, are selling identical copies of the original NS-10 speakers and at a really attractive price. After reading all I could and watching a few videos, I decided this was the best way to go and wanted to give a try to these replacement tweeters. I bought mine through a big online shop at 122 euros each, really a fraction of what I could have spent for NOS Yamaha NS-10 tweeters.

As promised the replacement is a drop in, there’s no need of adapting anything, the shape of the replacement speaker is identical to the original. All is as simple as soldering the speaker cables to the new tweeters and screw the tweeter back into the monitor.

I’m surprised at looking how identical to the original these tweeters are, all details are exactly the same, only the ring around the tweeter dome, has a slightly lighter grey colour. Is it this the difference that allows Avantone to clone the Yamaha speakers, without copyright infringement repercussions? Sure you understand I’m just kidding, I’m sure if they can freely sell a so exact copy, these details have been cleared already.

Original Yamaha tweeter on the left

After the installation and the promising sound test, I’ve been mixing for several hours, completely forgetting I was doing so on the new tweeters, perfect prove that I was feeling absolutely confortable with their sound!

I’m very happy with this upgrade! :)

DIY AML Fairchild Tube Equalizer and its Magic Eye magic

Before finding this DIY kit on the AML online shop, I didn’t know anything about Fairchild equalizers. I knew this manufacturer was famous for the 670 limiters that I had used many times in different software reissues and that was the same Fairchild factory, building those fat Flying Boxcar planes that used to impress me very much, roaring low over my head while a kid.

Pultecs as rain

As I had no tube EQs in the studio, my initial idea was building a couple of classic Pultec equalizers clones. Sure there is no need to explain more, my typical readers can possibly know more than me about. Searching for the best way to go, I remained surprised to see how many clones or Pultec inspired equalizers exist today in the market, in the DIY or finished product form. Even big manufacturers like Behringer, recently introduced their Pultec, under their Klark Teknik brand, at an insanely cheap price.

Looking on the AML web for info on their Pultec kits, I totally fell in love for their Fairchild 627 reissue, instead. When I crave for new gear, I try to stay tight to my technical side and using logic, considering what is really needed. This brings me most of the time to fix, mod and recycle old gear still in my hands, instead of buying something brand new. OK, after decades soldering and fixing things, I can consider myself a bit a tech too, but I’m mainly a musician, then deeply attracted by fantasy and details that can look futile, but are extremely fascinating to the non-logic (illogic?) part of the mind! That green glowing “Magic Eye” on the front panel was too intriguing and it was calling for my eyes!
I had seen it already, so far in time but still, it was so intensely fixed in my memory! Like coming out from a Sci-Fi movie, the feeling was a mix of curiosity and fear, so green and scary to only possibly being an alien artifact and sure able to promptly take control of my mind! :D

The “Magic Eye”, the VU meter grandfather

Before the 1960s, needle VU meters were extremely expensive, high tech precision tools mainly for scientific equipment, telephone and military use. VUs started becoming a practicable form of measuring an audio signal, only after mass production started in Japan and LEDs made the application on consumer products, very cheap. Electron ray indicator tubes were the way to go, to have a reliable visual representation of the presence and amplitude of an audio signal. First implemented on radios to make it easier tuning to a station, they can be found on vintage tape recorders and televisions too. The magic eye is a miniature cathode ray vacuum tube, the same as the screen of old televisions, plus an amplification stage, like in usual tubes. While the rest of the “screen” (anode) is illuminated by the electrons strikes, a part (electrode) is kept dark until a signal is detected and the flow of electrons is allowed to run in that area too.

Building the AML Fairchild 627 EQ

Once the kit arrived the connection with aircrafts strangely was evident again, this time in the form of a deja vu: The PCBs were cleverly cut in the resin board, in a form it resembled me the plastic aircraft model kits so popular in my youth, where you snap off the part you need from the mainboard, through pre-cut junctions.

AML ez-627 PCBs

My previous DIY builds never started from complete kits, all I usually had were a couple of PCBs and a BOM (Bill Of Material) list. Often, finding the right components to buy and where can become a boring and long process. This time there was nothing to worry about, only buying the valves that weren’t included in the kit. These are pretty common tubes available easily, what I couldn’t find were matched pairs, as I would like to have installed, at the beginning.

AML ez-627 unboxing

The quality of the boards is excellent and all components locations are labeled carefully. Same with the electronics, included in the kit are quality parts from manufacturers like Wima and Vishay. The transformers are Carnhill, the same I installed years ago in my DIY Neve 2254/33609 hybrid compressor (hopefully a good theme for a future post).

Assembling the 627

Arrived at the end of the project, the two Russian 6E5C/6E5S (C is an S in Cyrillic) hadn’t arrived yet, they were lost somewhere in the north of Spain. Calling the post office they told me my “Magic Eyes” had been held by customs (?), I can imagine the officers looking at my alien-ware, guessing what the hell are those for…

Building the tower for the Magic Eye, like somewhere in Mordor…

How does the 627 sound?

Even if the choice of building this processor might having being influenced not only by technically related reasons, I’m very satisfied with the results. All I passed through my units, in a couple of days they are alive, sounds very full and warm. I only tested my new pair on bass and guitars while mixing a new song, yesterday. As frequency action, its higher band goes up to 10kHz, below the 16kHz a Pultec EQP-1A (my initial choice), can work. The 627 is not too useful for brightening the higher part of the spectrum or shimmering, but very nicely working on lower frequencies. Testing it on bass, the tone I obtained was super fat and the action way more dramatic than I expected, in seconds I had a huge synth bass ready. I had to bounce the track to free the unit for processing some guitars, but I forced myself to limit the test to them only, or I would have started passing the whole song track by track, through the 627s! :D

I hope to make a follow up to this post, with the help of my OSO http://www.originalsoundsonly.com squad, with some audio tests, soon.


Most of the information on the Fairchild 627 Equalizer I could find online, comes from this link: http://www.preservationsound.com/?p=8602

The instructions on how to build the AML version of the 627, are online:

DIY Neumann U47 valve microphone, ioaudio MK47

Equinox U47 enclosure

There’s no doubt that the Neumann U47 is one of the most respected valve microphones ever made, been used to record the best vocals in the history of music. For this reason, lots of copies or variants have been built in the last 50 years, up to been recreated recently, even from one of its original manufacturers.
The hardest aspect to reproduce has always been the behaviour of the valve used, the Telefunken VF14, a military radio tube discontinued in the 60s (this caused Neumann to stop the production of this model) and very hard to find, until Telefunken reissued it under the name VF14K, a few years ago.



ioaudio MK-47 kit 01

I’m not a microphone expert, I only had built a pair of AKG C12 “clones” in the past, based on the Apex460 and made a few repairs of old micros, but absolutely wanted “that” sound and a tube microphone sounding different than my pair of DIY C12.
I found this project a few years ago on GroupDIY, while it still was called prodigy-pro.com and I liked the idea of using a pair of 6028 tubes to reproduce the VF14  and wanted to give it a try. Building a PSU and finding a microphone body hasn’t been really a problem, as in the same moment other builders had offers of kits for the ’47.

I remember opening the box, the kit’s more curious parts were the Soviet condenser with Cyrillic markings on it and the specially tailored transformer, reproducing the original Bv.08 trafo.


ioaudio MK-47 kit 02

I don’t remember the MK47 building to be difficult at all, all was explained very well in the MK47 Build Support thread of the groupDIY thread:


and on the instructions included.



ioaudio MK-47 kit 03

ioaudio MK-47 kit 04

Max Kircher’s ioaudio is still building kits for vintage microphones, their actual kit is an upgrade to transform a U87 into a tube U67, something I would like to build, one day for my 87.

Thiersch STW7 Red capsule, front

As capsule I chose the  Thiersch Elektroakustik, a perfect reproduction of the M7 capsule, with the membrane in two different flavors, PVC or PET (mine).







More tricky was building the power source, but I’ve been lucky to find a suitable pcb in Prodigy’s “White Market”.

As body, I used the Equinox Systems copy of the U47 enclosure, very nicely done.



This remains up to today my preferred microphone in the studio, I use it mainly on voice.

The Art of Procrastination, MXR M-113 Digital Delay


The MXR M-113 Digital Delay has been one of the most popular first generation audio delays, as it had a good quality but was more affordable than the previous processors. Introduced in ’76 at around 1000 USD, it was still expensive, but a lot less than the other digital delays available in the market.

MXR was specialized in guitar pedals, this delay was instead offered in a 19″ rack unit and, same as the other effects of the professional rack series, (Flanger/Doubler, Graphic EQ, Pitch Transposer) became very popular and used by famous artists such as David Gilmour, Frank Zappa, Roger Waters, Brian May and Mike Rutherford.


MXR memory module

To contain costs, a modular architecture was chosen. Optional memory boards were inserted in slots, to increase the delay time, but these were pretty expensive, costing almost like a complete unit.

MXR Digital Delay Internal Cards


Digital noise..well not only that! :D

Unfortunately the M-113 Digital Delay, same as its collegues of the same period, is pretty noisy and not only referring to the actual standards. Apart digital noises always present, these processors have a marcated tendency to generate audio hum.

The Model 113, Digital Delay has a maximum bandwidth of 20KHz, but this decreases with longer delays, down to 2.5KHz. The longer the time between repetitions, the tighter the passing frequency band, being reduced through antialiasing filters (HPF and LPF) the more the delay time is increased.


MXR Digital Delay Test Drive

As there are several video examples already of this delay tested on guitar, I thought it could have been a good idea to try it, using some unusual but hopefully interesting sounds.
To record, I used a dbx DI box and the signal sent to a Universal Audio 610 tube preamp, even taking all possible counter-measures, still a bit of hum is audible.

On the examples below, I feeded as sound source, a sweep from the filters in feedback of an old Korg MS-50 synthesizer, some piano chords I had recorded from a real piano and a couple of seconds of an oldschool reggae classic.

MXR Digital Delay, Test-01, (MS-50 Filter Sweep)

01) Dry sound, straight from the MS-50.
02) Delay Range 160ms, Delay Time x2, 50% mix and maximum regen (feedback)
03) Delay Range 160ms, Delay Time 0, 50% mix and maximum regen (feedback)
04) Delay Range 160ms, Delay Time 1/2, 50% mix and maximum regen (feedback)
05) Delay Range 160ms, Delay Time Sweep 01 (moving the Delay Time knob)
06) Delay Range 160ms, Delay Time Sweep 02 (moving the Delay Time knob)

MXR Digital Delay, Test-02 (Piano)

I chose these piano chords I recorded as, having long decays, are ideal to test the effect of short repetitions, when modulated. The effects space from phasing to complete madness. The last one is a strong modulation at the higher band of frequency of the sweep, reminding the effect of a ring modulation.

1) Dry Piano
2) Delay Range 1.3ms, 50% mix
3) Delay Range 10ms, 50% mix
4) Delay Range 160ms, 50% + Mod
5) Max Frequency Mod


MXR Digital Delay, Test-03 (Rhythmic Loop)

On the following examples, let’s try something that really impressed me first time I played with a Powertran  (An article on it, is coming soon). On the MXR the feedback has a faster decay and there’s not the “freeze” function, but the effect it is interesting, too.  Once the delay is at tempo with a rhythmic pattern, having adjusted the decay time knob, all Delay Range buttons create a different version of the pattern, but on different speeds. Being the buttons based on a double time sequence, all these are compatible in tempo. Let’s experiment with a small classic reggae riddim loop:

1) Dry loop
2) Loop effected as sort of Beat Repeater


MXR Digital Delay, Test-04 (MS-50 patch)

Last example, this time using a more complex sound from the MS-50.
1) Dry MS-50 sound
2) MXR MS – 50%MIX, 75% Feedback
3) MXR MS – 50%MIX, 75% Feedback + Mod
4) MXR MS – 50%MIX, 75% Feedback + Fast Mod

Service Manual: https://app.box.com/s/4t78o8xtzd


Echo, Nymphs and the Art of Procrastination

Echo, unlucky nymph

Since ancient times, places destinated to public speech or shows, were chosen in base of their  acoustical characteristics. A powerful voice listened near a sharp rock wall, could impress the public and add a magic ingredient, like if forces of nature were happy to help the venue, amplifying the wanted message.

Nymph Echo on a Roman painting

The Echo was so important, to have a dedicated character in Greek/Roman mythology:

Echo, a mountain nymph, was helping Jupiter in distracting his wife Hera, with interminable discussions, while the god was cheating on her with the other nymphs. Realizing the trick, Hera cursed Echo, removing her ability to speak. The only sounds she could emit, were the endings of words she could hear. As usual in ancient myths, the story ends in a tragedy, with Echo dead but not her beautiful repetitive voice, forced to live forever, but only in the most remote and inaccessible places.

Natural echo or reverb of special rock formations, or the reflecting shape of caverns, were used to create a dramatic effect on human speech, chants (and minds) for ritualistic or entertainment purposes.

The Art of Procrastination

Builders with time could, through architecture, recreate nature’s big spaces and the possibility to impress public with special effects, could  slowly move from remote areas to the cities.  Acoustically shaped amphitheaters and later, closed spaces like theatres and religious buildings were built for this function. Music started being played in dedicated “chambers” or “halls“, with reflecting walls and high ceilings, to obtain long reverberation times and decays.

At the beginning, recording studios used to record the space where musicians were playing, with microphones pointed to ceilings or walls, to capture the returning delayed sound and the signal was mixed to the original.

Later, rooms were dedicated exclusively to reverberation. A sound from the control room was sent to an amplifier in an empty room or chamber, completely empty and with reflective materials. One or more microphones were used to capture the effect, that was mixed to the rest of the sounds in the mixer. To add colour or to obtain special effects, metallic thin plates or springs, were recorded while resonating in the room, too.


At the end of the 50s, technology arrived to a point where the process of reverberation could be standardized and every major studio had a plate reverb like the EMT 140, or a DIY simpler version of it. The effect was obtained through the use of a big reflecting surface, in this case a metal foil put in tension through springs. A speaker inside the unit, puts the plate in resonation and a pickup captures the signal then amplified, through a tube preamp. There was a mechanical damper, to reduce the decay and later two pickups, placed in different places of the box, to obtain a stereo signal.

The effect is warm and beautiful, but unfortunately the technology needed big spaces as the plates were more than 1 meters long and these reverbs were very heavy and expensive.


Spring Reverb

Lee “Scratch” Perry and his Grampian spring reverb (Black Ark Studios)

A low quality delayed signal, could be obtained with the same process, implementing springs in tension, instead of plates. The idea, commercially developed by Laurens Hammond, the organ pioneer, was much less bulky then plates and even portable, to the point to become a standard on electric guitar amplifiers.

Spring reverbs give a particular vintage flavour to guitars, drums and percussive instruments, really great for old Funk or Reggae.

Tape Echoes

With the advance of technology, magnetic surfaces in the form of tapes (Echoplex) or disks/drums (Binson/Meazzi), were used to record and reproduce the delayed signal, on dedicated processors.

Roland RE501, RE-201, RE-150 Tape Echoes (maxproaudio)

The tape loop has been the first form of reproducing a sound with a delay. Two tape recorders where used before dedicated machine were born, one to record and the other for the playback. Delay time increased, the furthest the second recorder was placed from the repro machine.

One of the most popular tape echo units, has been the Roland RE-201 Space Echo, still searched by Dub producers has pretty high values, today.  Its tape was left unrolled in a transparent compartment inside the box. Rising the top and watch the tape moving in an apparently chaotic way, listening to the smooth noise of it, while smelling the characteristic chemicals odour, remains a very unique experience.

Some special effects, obtained using tape echoes, were pretty popular in the 60s and 70s, especially for Sci-Fi and Dub. I recorded a few examples with my RE-201 with the “Intensity” (Feedback) at maximum, conditions under where the Space Echo starts auto-oscillating feeding its own noise. The effects obtained are warm and immediately bring back to the past. The first track, called RE-201 Slam, is obtained instead slapping the unit with force. The shock is captured by the internal spring reverb. The third track is dry at the beginning, while has some additional effects from the second part. Track 2 and 4 are sweeps, moving the “Repeat Rate” knob.


Many virtual tape delay plugins of today, are based on the RE-201 Space Echo, the most popular of the RE series


Bucket-Brigade Device (BBD) or Analog Delays

In the wiki we can read that a bucket brigade or bucket-brigade device (BBD) is a discrete-time analogue delay line and that an analog delay line is a network of electrical components connected in cascade, where each individual element creates a time difference. A series of capacitors created the delay. Summing a big number of those, could create the desired long echo. Analog delays, cannot  reproduce the same sound for long, each repetition has a dirtier sound and this, with the eyes of those times, was seen as something to improve. They are very popular and still produced for guitarists.


Digital Delay Lines

Digital delays, can repeat the same sound, maintaining intact the quality of the original same as a sampler, only when sample rate and bit resolution are high enough.

The first commercial machines had a very low resolution, so samples were noisy and with a limited bandwidth. This is the characteristic that, in my point of view make them attractive and useful still today, when clean sound is no more a priority.

At the beginning, these machines, were only at the range of professional studios or rich producers. Until Electronic & Music Maker Magazine published a series of articles with schematic and instructions for a DIY delay, making affordable and available to a wider public this new technology.


Being a lover of Dub and vintage equipment, I’ve been lucky to own a few of the classic delay devices, bought when prices were extremely affordable, as nobody on those times needed a bulky and noisy delay only, machine.

Vintage delay lines have an other interesting aspect.

Powertran Time Delay switches

Their buttons select always multiples of the original tempo. If the delay is in sync with track tempo, pushing different switches, gives a today, very fashionable Beat Repeater effect, where for a example a loop is faster or slower, but always remaining in sync with the song. Some machines like the Powertran, had a freeze button, so that the sample was repeated without decaying, same as a sampler.

Effects obtained apart  the Echo

A Delay Line, is able to create a series of effects, not stricktly limited to repetitions of samples. Through the modulation of the processed signal and blend it to the original, a series of interesting effects are obtained, too.


When the same signal is combined with its delayed copy, it’s like having passed it through a filter. The Comb Filter resulting from counter phasing if modulated, changing the delay time through a Low frequency oscillator (LFO), becomes the pleasant effect called Phasing.


Same as Phasing, but with longer delay (10ms). Similar to chorus, but a more dramatic effect and with a marked SciFi like, character.


Even more delay and slow modulation, possibly with dry and wet signals on the opposite sides of the stereo field, gives the classic chorus effect that doesn’t need too many words more.


Automatic Double Tracking, was pretty popular in the 80s. Time delay is kept just below the perception of the single repetitions and is used especially on vocals, to give the illusion of doubling, without the need of recording two different voices.


On the next posts, we will test drive, three of the oldschool digital delays still in my hands:
MXR Digital Delay, Powertran Digital Delay Line and the Roland SDE-3000




References and interesting articles:





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