Hi all I am sure Frank would not mind me forwarding this message to the pc-audio list. There are perhaps some owners of plextalk units who may find these test as interesting as I did but who are not on the plextalk list.
Andre -----Original Message----- From: ptr1-users-bou...@freelists.org [mailto:ptr1-users-bou...@freelists.org] On Behalf Of Frank Cuta Sent: 12 January 2009 10:06 AM To: ptr1-us...@freelists.org Subject: Testing inputs on the Plextalk Testing the microphone and high level inputs on the Plextalk Recorders Summary: I took some time over the holidays to make some tests with my PTR1, PTR2 and the new PTP1 Pocket. These tests are not extremely professional and certainly not comprehensive. I had a cheap and dirty way of looking at input sensitivity and that is what I concentrated on. Mostly I wanted to put the microphone input of the Plextalk Pocket through its paces but I also wanted to compare its input characteristics with those of the PTR1 and PTR2. Eventually I extended my testing to the high level input as well. I will first discuss what I think I learned -- Farther below I provide the details of my testing process in case you are interested. Note that these tests are limited to the input sensitivity of the microphone preamp in each unit. This is of interest because most distortion issues are related to a mismatch between the microphone and this input sensitivity. In my listening tests I noticed no gross differences in frequency response, out put drive or any of the other important sound characteristic between these 3 models and in any case I do not have the instruments necessary to make such tests. However, the sensitivity of the microphone preamps is another story. They are different in all 3 models. Having a better understanding of these sensitivity characteristics can assist you to match your microphone with your preamp for a given situation and reduce the possibility of you winding up with a distorted recording. you can see from a quick glance at the figures below that the most sensitive microphone preamp is in the PTR1, the least sensitive microphone preamp is in the PTP1 Pocket and the PTR2 is somewhere in between. I want to stress that overall sensitivity is not a good indication of quality nor is it even an indication of functionality. For example the Sennheiser microphone on the list below turned out to be the least sensitive of all microphones tested but cost $1000 a pair and they are worth it. But, on the other hand I would not choose this microphone to go out and try and pick up bird song or other faint nature sounds. You have to think about the sound levels that you typically deal with and then choose how to best pick it up. Knowing your sensitivity characteristics can assist you to optimize your performance. Say you are recording a meeting and have the choice to use either your PTR1 or your Pocket and no external microphone is available. Your best choice would be the PTR1. However if a tiny single point direct plug in microphone is available the Pocket would be the best choice since the single point microphone will provide better pickup but it is not supported on the PTR1. On the other hand if you are using this same single point microphone and singing or playing an instrument directly into it and your choice is to use either a PT Pocket or a PTR2 you would use the pocket because at these levels the microphone input on a PTR2 would be driven into distortion. Always keep functionality in mind. Note that in my tests although the PT Pocket has the lowest input sensitivity it is the only one of the three models that made good recordings using every microphone that I tested. Note also that since the Pocket is the only one of the 3 recorders that permits you to defeat the automatic recording level when using the internal microphone I was able to list its internal microphone on the list with the other microphones that I tested. I made excellent recordings on all 3 units using their high level inputs. I made tests with 4 Sources, the high level outputs from my sony CD player, a Yamaha EMX200 mixer, a $50 pocket sized Archos microphone preamp and a $180 pocket sized Sound professionals microphone preamp. The tests with the 2 battery powered preamps turned out to be more of a test of the preamps than the Plextalks. The Archos gets all of its gain in the sweep of a single pot and is very touchy. The Sound Professionals unit has discernibly less internal noise and is more controllable since it achieves its gain in 3 separate ranges. Both preamps functioned perfectly with all of the professional microphones on my list but when using the very hot single point microphones and my fairly loud test signal it was easy to drive the Plextalks into distortion. I believe these preamps were originally designed more for interfacing professional microphones with high level inputs on portable recorders. Last, I Attempted an ultimate gain arrangement by using a very hot single point microphone to drive the Sound Professionals preamp and feeding the output of the preamp into the microphone input of the PT Pocket. This actually works very well but do not try it unless you are in a very very quiet environment. I attribute the success of this test to the very low noise spec on this fine preamp. With this system I am recording sounds inside and outside of my home that I cannot hear with my normal hearing. Warning do not try this if there is any danger of being interrupted by a ringing telephone or some one talking to you from a few feet away. The result could damage your ear drums. Testing Details: I have a collection of microphones at my disposal of various technologies and with a corresponding wide range of sensitivity values. A microphone's sensitivity spec determines how hot of an output signal you get for a given input level. My goal was to make tests with a selection of these microphones and make lists of the respective manual recording settings that it takes to achieve a "good" level on each model of Plextalk. The assumption is that given the fixed sensitivities of the respective microphones and the constant level of the sound source if I tested each microphone with each Plextalk I will have a basis for comparing their relative input sensitivities. I picked a high quality sound source of a specific level and played the same material over and over on it while I changed machines, microphones and adjusted manual recording levels. The material was a live Robin and Linda Williams concert that I recorded as a wave file off of my Mackie 1640 soundboard. I played back the CD through my studio monitors and set up each pair of microphones 36 inches from the monitors. The sound pressure level meter read 96 dB max at the microphone grilles and was never changed. The microphones were connected directly to the microphone input of each Plextalk with a single unit Y cable which accepts 2 XLR microphone outputs and converts them to a stereo 3.5 mm phone connector -- no noisy adapters. (I believe that the cable is made by Hosa.) For each test I connected a pair of microphones and kept turning down the recording level on the recorder until it said good. The professional microphones ranging in sensitivity from lowest to highest were Sennheiser 441, Electro Voice RE-15, Shure sm58, Shure beta 58, AKG c1000 and Audio Technica ATM31. The first 4 are dynamics and the last 2 are condensers. This was going to be the extent of my testing but at the last I added to single point stereo electret microphones, one from IRTI and one from Sound Professionals. I was surprised to learn that they are actually much hotter than even my most expensive professional microphones. For each test I started with the audible level reading high and kept turning down the manual recording level until it said good. The value recorded in the list below is thus the approximate max recording level that could be set on that recorder for a specific microphone with an input level of 96 dB. . Plextalk Pocket: 441= 15 RE15 = 14 SM58 = 14 Beta SM58 = 13 C1000 = 10 ATM31 = 9 PTP internal = 9 T single point (from SP) = 6 Single point (from IRTI) = 6 Plextalk PTR2: 441 = 13 RE15 = 12 SM58 = 12 Beta SM58 = 11 C1000 = 7 ATM31 = 6 Single point (from IRTI) = 5 (audible overdrive distortion at this SPL) T single point )from SP) = 4 (pronounced overdrive distortion at this SPL) Plextalk PTR1: 441 = 11 Re15 = 11 Sm58 = 11 Beta sm58 = 9 C1000 = 6 Atm31 = 6 (single point electret microphones not supported) I then sat down and listened to the results on studio monitors and several different headphones. --------------------------------------------------------------------------- To leave the list at any time, please write to <ptr1-users-requ...@freelists.org> with unsubscribe ptr1-users in the subject or the body. The list home page is at <http://www.freelists.org/list/ptr1-users/>. No virus found in this incoming message. Checked by AVG. 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