FAQ Technical


Q: FM 105 and FM 205 power supplies.

Which can be used with the FM 155-MKIIR and FM 223?


A: Only the FM 105 p.s. which is delivered with each FM 155-MKIIR can be used for the FM 155-MKIIR. If other p.s. are connected the unit will be damaged massively.


For the FM 223 a similar looking but different power supply is used, the FM 205 (it cannot be used on the FM 155-MKIIR by accident as it has a different connector).


NEVER EVER try to connect any other type or brand of power supplies. Damage occurred from this is not covered by warranty.



Q: What is the recommended warmup time for FM ACOUSTICS equipment?

A: All of FM ACOUSTICS products use a unique elaborate biasing system that guarantees very fast warm up. Products that need an hour or more warm up time or - worse - need to be left running continuously are simply unacceptable.

The actual warm up time depends on the type of unit and on the time since the last switch on. If the unit has been running a few days ago the warm up time is 5-15 minutes.

If the FM ACOUSTICS unit has not been run for several weeks, it will sound perfect after about 20-30 minutes of warm up.


If the unit was switched off for several months, it is best to run it for an hour or two.
However, no FM ACOUSTICS will ever sound harsh or be unstable on switch on. They sound right immediately from the beginning and will be optimal after the abovementioned times.



Reactivating electronics that have not been switched on for months or years

A little known fact is that electronics (of whatever brand) that have not been switched on for 4-6 months or longer should - before switch on - ideally be preconditioned with a variac. This way they can be "run in" at low voltage, starting at about 1/3rd of the mains voltage (40V on a 100-120V mains or 80V on a 220-240V supply). Every 5 minutes the mains voltage can then be increased by about 10V (or 20V with 220-240V mains).

One reason is because electrolytic capacitors (that are used in many electronics) are electro-chemical components and age over time. When not having been used for a long time they do prefer a gradual rise in voltage. An immediate high voltage can weaken a component that has been "dormant".

So if you have a unit that has not been used for many months or years and uses electrolytic caps (and most electronic do), bring it to a technician that has a variac and ask him to "run in" the unit as described above. You may be compensated for this little effort by a considerable increase in life expectancy and reliability.

The lifetime of electrolytics depends on many variables, such as temperature, voltage rating and voltage applied, ripple current, regular or irregular use, vibration etc. and of course on the quality of the capacitor itself. Typical lifetime can be anywhere from three years for commercial parts to ten or fifteen years for high reliability and military spec parts.
In some FM ACOUSTICS amplifiers that have been in regular professional use for 12-24 hours a day, the electrolytics are still in fine shape after 30 years! This, however, cannot be expected as the standard. The usual lifetime can more or less be compared with the lifetime of a top-quality battery.


Q: When I listen at reasonable levels the output level control of the FM ACOUSTICS preamp is about at the 9 o'clock position. It gets too loud when I turn it up. What can I do about this?

A: If this is the case with all types of sources your audio system has excessive overall gain.
If your power amplifier has gain controls that do not affect sound quality (unfortunately some indeed do degrade the quality of the audio signal) reduce the level on the power amp by lowering its volume control.
If there are no gain controls on the power amp or there is an audible change when turning the amplifier's level control, you could push the -20dB "mute" switch on the FM ACOUSTICS preamplifier. However, there is a danger of accidentally hitting the "mute" switch, instantly increasing the level by 20 db. This can lead to damaged drivers.

The newer FM ACOUSTICS line stages allow fine adjustment of gain. Contact your distributor who cab optiomize the setting for your system. 

If this excessive gain is only apparent with one source, say a CD-SACD player/converter, while it is not so with other sources, the source does not adhere to professional standards and produces excessive output levels.
In other preamplifiers/line stages this can provoke overload of the input stages. All FM ACOUSTICS line inputs have very high overload margin so this is not of concern.


However, the fact remains that there is too much overall gain and "the volume control is in the 'wrong' position".

An optimal gain setting is - if at maximum acceptable volume level - the preamplifier's volume control is close to full level (around the 5 o'clock position) - which will result in a 11 o'clock to 2 o'clock position at more normal volume levels. Such a setting will also help protect against an accidental heavy peak impulse that might destroy the speakers.
Please note that there is N O T less "reserve" when optimizing the gain as indicated above. The moment an amplifier clips it reached its limit whatever the Volume control position of the preamplifier is.


It is NOT a good idea to have excessive overall gain in the system and then run the volume control at low levels (say below 10 o'clock position).

If this excessive gain is only apparent with one source (say the CD/SACD converter) one solution is to reduce the output level of the converter but this may have a negative influence on sound quality (digital volume control circuits). If you encounter such a problem the newer FM ACOUSTICS Preamplifier/Line stages allow special remedies. Contact your distributor with details on your system and settings.

If you use a phono section that has excessive gain you may be able to reduce the gain setting on the phono preamp (as featured in the FM 223, 222 and 122 phono linearizers).

As only few manufacturers of "hifi" equipment adhere to standards, different output level and gain is employed - which is what leads to such effects. In the professional world such problems hardly occur (only with some semi-pro equipment).

Q: Why does FM ACOUSTICS not use detachable mains cables?

A: The main reason is that the cable is an integral part of these products. By fixing it we can assure the quality of reproduction is optimized and no deterioration can occur.
Also, with a detachable mains cable three additional contacts are added in the mains line. These are unnecessary and wherever possible contacts must be avoided as they are a weak link and it is always better to have as few contacts as possible.
This is also the fact with the widely used "Euro" plugs which are not suitable at all for high currents. While their ratings suggest that they can handle high power, practical experience shows that the contacts of these plugs are not optimal and often there is quite a bit of "play" between the plug and the socket. Due to this, the actual area making contact is rather small, clearly too small for high current demands. As the contact is not perfect, micro-arcing makes these contacts loose their initially more or less reasonably smooth surface within a short time. Thereby additional resistance is added into the mains line, certainly not what is wanted in precision audio...
The lower the impedance, the better - the fewer contacts in a product the better it will perform and the better will be reliability.


Q: In your cables, why do you not use silver as conducting material?

A: Just because silver is a bit more costly a raw material does not mean that it gives better performance.
The usual reason quoted for using silver is that silver's conductivity is better. Correct, but the difference to copper is a mere 2%. Therefore, by adding 2% more copper in the cables the improved conductivity attributable to silver is effectively negated. By increasing the pure copper content up to the optimum, performance will surpass that of the best silver cable (incidentally, there is no speaker cable with a satisfactory square section made out of pure silver). Other characteristics (such as shore hardness, oxidation etc.) make silver less desirable than copper.
However, one must be aware that considerable quality differences exist between the different copper cables. It is very important what kind of copper is used, how it is purified, how it is drawn, how the strands are prepared, etc. These differences can be audible.


Q: You have a large range of interconnect cables. Which type of interconnect cables should be used between the various units?

A: For detailed explanations and recommendations see under PRODUCTS - AUDIOPHILE: Interconnect-, Phono- and Speaker cables.
Furthermore, you will find drawings and information in the download section under "Technical Bulletin 31" with precise information for almost all applications.

Technical Bulletin Nr. 31
Selecting the correct interconnect cables
Adobe Acrobat Document 209.7 KB



Q: What preventive maintenance is recommended?

A:In the large power amplifiers its is important to clean the fan filters regularly, a least every 3 months. This can easily be accomplished with a vacuum cleaner. When very dirty, fan filters can be washed and let dry before re-installation. After having been washed a few times, the filter must be replaced with a new one.

In case of the switches on FM ACOUSTICS phono linearizers and line level equipment it is recommended to activate them 10-20 times every 3-6 months. That helps the contacts to perform the self cleaning action and preserves conduction. The same applies for all input and output connectors of any type: just unplug and re-plug them a few times to assure optimal contact. This is especially needed in polluted areas and humid climates. A small effort that can help bring noticeable improvement.