Essential information translated to french and italian
A new power amplifier have seen the light of day. This is a True Class A transistor output power amplifier, complimentary driven from positive and negative power supply. It has 2 toroidal mains transformers, and a huge capacity bank, 540.000 uF in both positive and negative supply, for a total of 1.08 Farad, and is DC coupled from input to output.
Output power in 8 Ohms are 2 x 25 W plus. All inputs/outputs are on the backside of the amp, with input attenuator potentiometer, with the highest available quality, and matched within 1 % tolerance. The pots can also be used as balance control, as well as sensitivity control.
Mains power is switched on with a key switch, the key can be removed in both operating and off position if wanted. 230 V power on is indicated in the top of my registered logo and trade mark.
The amplifier pilot production series of 6 amps will deliver 30W plus on both channels in 8 Ohms load.
The prototype now has got newly developed sensors mounted on the cooling fins in each side to provide feed back information about the temperature of the fins to the amplifier input module filter supplies, for safe, stable control of the amps output current. This will maintain a temperature of max. 53 degrees Celcius +/- 2 degrees, for a very safe operational point of the triple output transistor pairs conservatively rated class A currents.
The pilot series will of course have the same modifications.
More information, prices and technical data will be available soon including spectral analysis . Weight is 15,2 kg.
Pics of the amp can be seen HERE.
Damping of ringing from Altec horns 811 and 511 (800 Hz and 500 Hz lowest bottom x-over), PART 1 from October 2011 News, will continue here in PART 2 with text and pics. This is a professional approach to a sensible ringing problem from both horns, and a simple cure with written description and photos of the working process. The Altec aluminium casting is too thin related to the areas. I have been using vibration test equipment with extremely light sensors, to find positions and frequency levels of the resonances. Part 2 starts here.
During the last couple of months, there has been an increasing interest for my cleaned / recoated Altec 15/16 inch bass drivers. In this month's NEWS I have added a document with 4 curves, showing what happens with free air resonance frequency and impedance height of the resonance versus the progress of the cleaning.
The red curve in the bottom is the speaker condition when I bought it. The Impedance in free air is 148 Ohm and Fs is 29,32 Hz, totally unacceptable, the surround is stiff, the cone is hard to move. Very poor condition.
As the cleaning progresses, resonance frequency drops further and impedance height is increased. Totally finished cleaning and recoated with my non sticky flexible coating to app. 1 % of normal Altec coating thickness, Fs has dropped to 22.92 Hz, and impedance height ends at 328 Ohm.
The Surround is soft, the cone has a high compliance again. The speaker is reborn like when it left the Altec Factory many years ago (30-40 years). It is also interesting to see (check) that the Alnico magnet has its full power at this age. You can see the documentation curves and pics HERE.
I have developed a new coating material for the bass driver surrounds, a flexible, thin layer yet not sticky, giving a lower Fs than with the original Altec coating, and it won´t run down. The surround is still fully protected in moist environments.
Damping of resonances (ringing) in Altec sectoral horns 511B and 811B. Below is a detailed working process describing needed materials for the job (moulding with beach sand and resin/hardener).
This is the first part of 2, on the moulding of the bowes in the front of the horns, part 2 will tell how to make the more difficult bowes on the backside of the horns, in text and with photo´s. See first part HERE!
There have been some discussions on the Joe Net about the Altec Bass drivers. I have made a couple of documents, released a few of years ago on my homepage, about the deteriorations of the performance of the drivers, due to the aging of the coating of the surrounds, and what happened with these drivers as the years went by.
The shown example is an Altec 416-8B sn. 39880. Fs is 27,27 Hz and the impedance peak is 117 Ohm before restoring, see photo. After restoring Fs is 22,43 Hz and the impedance peak is 213 Ohm. In other words: Fs is reduced by 17,75 %, the impedance peak is 213 Ohm = 84,96 % higher. Both achievements are absolutely in the direction that we want.
The higher Fs impedance means less resistance moving the piston (cone) and bigger fluctuations at the deepest frequencies, at the same current than the uncleaned, and with less distortion .
Result: Deeper bass capability, and with better dynamics in the range up to app. 250 Hz (listening impressions).
Furthermore the cleaned and restored surround is much better looking, giving the speaker a much better and newer appearance. Read more here.
My next 2 projects will be a balanced in/out true differential tube microphone amplifier (with some other stuff), and an Onken 360 litre cabinet with Altec 416-8A or 416-8B drivers. Drivers will be my restored versions and the sound response will be measured in the 20 Hz to 1000 Hz range, against a standard Altec bass driver version (same model) like it is, bought on Ebay in the typical condition they are in when received (in 2011).
The data of the bass drivers here are typical completely changed from their new state (when they left Altec factory). Free air resonance has gone up, the cone is much harder to move, moving mass has increased with 30 50 grams, all because of the stiff surrounds due to the impregnation getting hard over the years. So do not rely on original new Altec data, inserted in the Thiele/Small scheme, resulting data will be wrong.
Spectral data sheets for my monolithic Mike amplifier (dynamic mike, condenser mike, signal is swept from a balanced 100 Ohm source from 20 Hz to 20 KHz) and results are excellent, dynamic range, THD and SNR is in a class of its own. Second and third harmonic are below 100 dB of 1000 Hz fundamental (who can hear second and third harmonics below 100 dB of fundamental, they are at the least 100.000 times smaller than fundamental ?).
At 4 different settings of input level and active gain, you can watch the impressive 4 spectral curves with data below the curves here. The signal out from the amp has passed 3 transformers, one from the analyzer generator to the amp, and 2 transformers in the amp.
Software is SpectraPRO, sound card is Lynx L22.
In the March news I wrote about my Professionel Microphone Amplifier which is in development. The left side (channel 1) is now finished with minor changes. This one is the monolithic channel, with top world class integrated circuits, and regulated low noise power supplies for dynamic mikes, as well as regulated phantom power 48 volt (switchable in/out) for the condenser mikes.
Frequency response is 10 Hz -0,1 dB and 20 KHz -0,4 dB for the input signal passing 2 transformers, with 600 Ohm balanced output transformer loaded with 600 Ohm and balanced input transformer 600 Ohm.
This microphone preamp has been used for all measurements during the testing of my modified Altec A7 VOTT bass cabinet (mine is the road version 828, reinforced) sound frequency response from 20 Hz to 1100 Hz, with remarkable results. See the resulting curves and pictures from the session here.
In December News I wrote about designing a professionel microphone preamplifier. The first part (channel1) has been finished, with a super low noise differential instrumental operational amplifier, with balanced in- and output transformers, 600 Ohm in and out, output loaded with a 600 Ohm resistor. See the pictures and read more about it on the Microphone page.
In the summer of 2010 a new product has seen the light, a line tube amplifier with unbalanced input (or balanced on demand) with an excellent world top class balanced 600 Ohm line transformer out, made in Sweden.
The gain is 5,5 times in/out, the output transformer is loaded with a 600 Ohm resistor, cable load out + 50 m with excellent frequency data.
The distortion is very low with this no negative feed back design, following my new design concept from my mono blocks. Spectral THD data sheets for levels 125 mV rms, 250 mV rms and 500 mV rms can be found on my Altec pages in a couple of days.
The 2 stereo channels will be in one chassis, tube rectification, choke input, reg. power supplies, Russian vacuum tubes and other stuff too.
At the moment I am working on a professional 2 channel microphone amplifer, balanced in, balanced out, for condenser microphones, with phantom power supply. Why is that, you may ask? I need a top class precision low noise amplifier for my new condenser ref. mike (- 1 dB at 9 Hz), to measure the roll off bass response in bass cabinets, and to be able to tune the cabinets for the deepest roll of.
The 2 channels wil be different in designs. Channel 1 will be with the top integrated circuits that the biggest manufacturing companies are using for the moment, to hear how they sound, with the extremely low THD they offer, with a lot of negative feed back. How would you think they sound ?
Channel 2 will be built with mainly tube components (and some other stuff), balanced in and out, to compare the sound and measurements.
The sound on Danish Television on one of the danish programmes is terrible at the moment, with a lot of ssssss sound, a lot of background noises, and irritating pops and noise during transmission, I have never heard such bad sound, I wonder why.
Well, let us see what comes out of this project.
I have upgraded my SpectraPRO software with another option, which makes it possible for me to produce impedance charts with free air resonance frequency and acoustic ohmic impedance of the peak, with great precision, on any speaker. These measurements indicates the level of the compliance for the specific speaker.
Other measurement areas are:
Impedance of the full audio band for a two or three way speaker system.
Impedance charts of passive filters.
Frequency range and level of the sound output of a speaker system.
Frequency range of electronic filters.
Frequency range of amplifiers.
Frequency range and impedance of compression drivers/horn combinations.
and spectral analysis of the complete audio range of the amplifiers.
Per Hasling 04.03. 2010
7 Spectral Analysis sheets for Hasling Head Amp MK3, battery version.