{"title":"Preamplifiers","description":"\u003cp\u003eThe output from a condenser microphone is a very high-impedance signal and is therefore very sensitive to the capacitive loads of cables. This makes it necessary to introduce a driver with high input impedance and low output impedance. Such a driver is called a preamplifier.\u003c\/p\u003e\n\n\u003cp\u003eThe frequency range of a preamplifier is determined by its electronic circuit and is typically more than 200 kHz at the high end and 1-10 Hz at the lower end. The lower end is determined by the input impedance of the preamplifier and the capacitance of the microphone. High microphone capacitance gives a low cut-off frequency.\u003c\/p\u003e\n\n\u003cp\u003eThe dynamic range of a preamplifier is defined as the range between the highest level that the preamplifier can handle without distortion, and the lowest level it can measure. The highest level is related to the preamplifier’s supply voltage, whereas the lowest level is related to the electrical noise generated by the preamplifier itself.\u003c\/p\u003e\n\n\u003cp\u003eThere are today two different preamplifier principles in the world of acoustics. One is the traditional type for externally-polarized microphones often referred to as the “LEMO” type because of its 7-pin connector and has become an industry standard. It is voltage driven and can handle high voltage signals up to 50Vpeak.\u003c\/p\u003e\n\n\u003cp\u003eThe other principle uses a Constant Current Power (CCP) supply and was introduced around 1996 to the world of high-precision acoustics. Before that, the quality of CCP preamplifiers was not as good as the voltage driven LEMO types, but this is not the case today. A CCP preamplifier uses a Constant Current Power supply, which must be between 2 mA and 20 mA (nominally 4 mA), to produce a constant nominal voltage level of 12 Volt DC (referred to as the bias voltage). The output signal from the microphone superimposes fluctuations around this DC level. The great advantage of CCP preamplifiers is that they use a two-wire system, where the signal is superimposed on the wire through which the current is kept constant.\u003c\/p\u003e\n\n\u003cp\u003eThis means that simple co-axial cables can be used instead of the more complex 7-core cables used with the voltage driven LEMO types. This is traded off by accepting a lower upper limit in dynamic range (due to the lower driving voltage of a constant-current source) which limits the maximum output signal to approximately 8 Vpeak, and the necessity of having to use prepolarized microphones. The range of available prepolarized microphones is still not as wide as for externally-polarized microphones, although GRAS was the first in the world to introduce 1\/4” prepolarized microphones and have also released a 1\/8” prepolarized microphone.\u003c\/p\u003e\n\n\u003cp\u003eGRAS microphone preamplifiers are all small, robust units optimised for acoustical measurements with condenser microphones. They are all compatible with measurement microphones as defined in the international standard IEC 61094 “Measurement Microphones, Part 4: Specifications for working standard microphones”.\u003c\/p\u003e\n\n\u003cp\u003eAll GRAS preamplifiers are built around a small, thick-film precision amplifier with very high input impedance. The casings are made of stainless steel for maximum strength and durability with minimal sensitivity to vibration and microphonics.\u003c\/p\u003e\n\n\u003cp\u003eThey will work within their specifications up to a temperature of 70°C (158°F). Special versions for use at temperatures up to 120°C (248°F) are available on request. The only effect of elevated temperature is a slight increase in inherent noise level. This will change the lower limit of the dynamic range of the microphone\/preamplifier combination, thus limiting the ability to measure very low sound pressure levels.\u003c\/p\u003e\n\n\u003cp\u003eCCP (Constant Current Power) is the same as IEPE (Integrated Electronic Piezo-Electric) and CCLD (Constant Current Line Drive) and is compatible with many other constant current driven products such as Deltatron®, Isotron, etc.\u003c\/p\u003e","products":[{"product_id":"gras-26aa1-4-preamplifier-with-integrated-cable-for-intensity-probes","title":"GRAS 26AA 1\/4\" Preamplifier with Integrated Cable for Intensity Probes","description":"ll GRAS microphone preamplifiers are based on a small ceramic thick-film substrate with a very high input impedance. The ceramic substrate is shielded by a guard ring to minimise the influence of stray capacitance and microphonic interference.","brand":"GRAS","offers":[{"title":"Default Title","offer_id":48310080274765,"sku":"26AA","price":0.0,"currency_code":"DKK","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0755\/9344\/9805\/files\/26AA-k_HiRes-RGB.png?v=1701171870"},{"product_id":"gras-26ab1-4-1-2-universal-preamplifier-with-integrated-connector","title":"GRAS 26AB 1\/4''-1\/2'' Universal Preamplifier with Integrated Connector","description":"ll GRAS microphone preamplifiers are based on a small ceramic thick-film substrate with a very high input impedance. The ceramic substrate is shielded by a guard ring to minimise the influence of stray capacitance and microphonic interference.","brand":"GRAS","offers":[{"title":"Default Title","offer_id":48310080569677,"sku":"26AB","price":0.0,"currency_code":"DKK","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0755\/9344\/9805\/files\/26AB_HiRes-RGB.png?v=1701171879"},{"product_id":"gras-26ac-1-1-4standard-preamplifier-with-integrated-miniconnector","title":"GRAS 26AC-1 1\/4\" Standard Preamplifier with Integrated Miniconnector","description":"ll GRAS microphone preamplifiers are based on a small ceramic thick-film substrate with a very high input impedance. The ceramic substrate is shielded by a guard ring to minimize the influence of stray capacitance and microphonic interference.","brand":"GRAS","offers":[{"title":"Default Title","offer_id":48310081093965,"sku":"26AC-1","price":0.0,"currency_code":"DKK","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0755\/9344\/9805\/files\/26AC-k_HiRes-RGB.png?v=1701171889"},{"product_id":"gras-26ah1-2-syscheck-preamplifier-with-3-m-integrated-cable","title":"GRAS 26AH 1\/2'' SysCheck Preamplifier with 3 m integrated cable","description":"GRAS 26AH has SysCheck for easy remote verification of the measurement chain. It allows you to send a test signal to an RC network in the preamplifier","brand":"GRAS","offers":[{"title":"Default Title","offer_id":48310081749325,"sku":"26AH","price":0.0,"currency_code":"DKK","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0755\/9344\/9805\/files\/26AH-k_HiRes-RGB.png?v=1701171896"},{"product_id":"gras-26ai1-2-preamplifier-with-integrated-connector-low-frequency","title":"GRAS 26AI 1\/2'' Preamplifier with Integrated Connector, Low Frequency","description":"GRAS26AI is a preamplifier designed for low-frequency applications in the laboratory and field and accommodates directly for all IEC 61094 standardized 1\/2\" externally polarized measurement microphones.","brand":"GRAS","offers":[{"title":"Default Title","offer_id":48310082011469,"sku":"26AI","price":0.0,"currency_code":"DKK","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0755\/9344\/9805\/files\/26AI_HiRes-RGB.png?v=1701171904"},{"product_id":"gras-26aj1-2-syscheck-preamplifier-with-integrated-connector","title":"GRAS 26AJ 1\/2'' SysCheck Preamplifier with integrated connector","description":"All GRAS microphone preamplifiers are based on a small ceramic thick-film substrate with a very high input impedance. The ceramic substrate is shielded by a guard ring to minimise the influence of stray capacitance and microphonic interference.","brand":"GRAS","offers":[{"title":"Default Title","offer_id":48310082339149,"sku":"26AJ","price":0.0,"currency_code":"DKK","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0755\/9344\/9805\/files\/26AJ_HiRes-RGB.png?v=1701171914"},{"product_id":"gras-26ak1-2-standard-preamplifier-with-integrated-connector","title":"GRAS 26AK 1\/2'' Standard Preamplifier with Integrated Connector","description":"GRAS 26AK is a preamplifier designed for general purpose in the laboratory and field and accommodates directly all IEC 61094 standardized ½” externally polarized measurement microphones.","brand":"GRAS","offers":[{"title":"Default Title","offer_id":48310082535757,"sku":"26AK","price":0.0,"currency_code":"DKK","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0755\/9344\/9805\/files\/26AK_HiRes-RGB.png?v=1701171921"},{"product_id":"gras-26ak-s1-1-2-preamplifier-with-integrated-connector-low-frequency","title":"GRAS 26AK-S1 1\/2'' Preamplifier with Integrated Connector, Low Frequency","description":"GRAS26AK-S1 is a preamplifier designed for general purpose in the laboratory and field and accommodates directly for all IEC 61094 standardized ½” externally polarized measurement microphones.","brand":"GRAS","offers":[{"title":"Default Title","offer_id":48310082961741,"sku":"26AK-S1","price":0.0,"currency_code":"DKK","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0755\/9344\/9805\/files\/26AK_HiRes-RGB_45cf120d-3015-43bd-aeb4-013de0ee44b4.png?v=1701171931"},{"product_id":"gras-26al1-4-syscheck-preamplifier-with-3-m-integrated-cable","title":"GRAS 26AL 1\/4\" SysCheck Preamplifier with 3 m integrated cable","description":"All GRAS microphone preamplifiers are based on a small ceramic thick-film substrate with a very high input impedance. The ceramic substrate is shielded by a guard ring to minimise the influence of stray capacitance and microphonic interference.","brand":"GRAS","offers":[{"title":"Default Title","offer_id":48310083354957,"sku":"26AL","price":0.0,"currency_code":"DKK","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0755\/9344\/9805\/files\/26AL-k_HiRes-RGB.png?v=1701171942"},{"product_id":"gras-26am1-2-standard-preamplifier-with-3-m-integrated-cable","title":"GRAS 26AM 1\/2'' Standard Preamplifier with 3 m integrated cable","description":"All GRAS microphone preamplifiers are based on a small ceramic thick-film substrate with a very high input impedance. The ceramic substrate is shielded by a guard ring to minimise the influence of stray capacitance and microphonic interference.","brand":"GRAS","offers":[{"title":"Default Title","offer_id":48310083518797,"sku":"26AM","price":0.0,"currency_code":"DKK","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0755\/9344\/9805\/files\/26AM-k_HiRes-RGB.png?v=1701171952"},{"product_id":"gras-26as1-4-standard-preamplifier-with-3-m-integrated-cable-very-short","title":"GRAS 26AS 1\/4\" Standard Preamplifier with 3 m Integrated Cable, Very Short","description":"All GRAS microphone preamplifiers are based on a small ceramic thick-film substrate with a very high input impedance. The ceramic substrate is shielded by a guard ring to minimise the influence of stray capacitance and microphonic interference.","brand":"GRAS","offers":[{"title":"Default Title","offer_id":48310084239693,"sku":"26AS","price":0.0,"currency_code":"DKK","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0755\/9344\/9805\/files\/26AS-k_a_HiRes-RGB.png?v=1701171969"},{"product_id":"gras-26ca-1-2ccp-standard-preamplifier-with-bnc-connector","title":"GRAS 26CA 1\/2'' CCP Standard Preamplifier with BNC Connector","description":"The GRAS 26CA 1\/2'' CCP Standard Preamplifier is a small, robust unit and uses a CCP power supply (ICP ®), e.g. GRAS 12AL. It has a very low inherent noise level, a large dynamic range and a frequency response from below 2 Hz to above 200 kHz.","brand":"GRAS","offers":[{"title":"Default Title","offer_id":48310084403533,"sku":"26CA","price":0.0,"currency_code":"DKK","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0755\/9344\/9805\/files\/26CA_Web.png?v=1701171977"},{"product_id":"gras-26ca-ht1-2-ccp-high-temperature-preamplifier-with-bnc-connector","title":"GRAS 26CA-HT 1\/2'' CCP High Temperature Preamplifier with BNC Connector","description":"The GRAS 1\/2\" Preamplifier 26CA-HT is similar to the GRAS 26CA Standard Preamplifier, but optimzed for use in high-temperature applications up to 120 °C (248 °F).","brand":"GRAS","offers":[{"title":"Default Title","offer_id":48310084665677,"sku":"26CA-HT","price":0.0,"currency_code":"DKK","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0755\/9344\/9805\/files\/26CA_Web_ba765060-60e7-4121-b407-ceeafd6f375c.png?v=1701171985"},{"product_id":"gras-26cb1-4-ccp-standard-preamplifier-with-microdot-connector","title":"GRAS 26CB 1\/4\" CCP Standard Preamplifier with Microdot Connector","description":"Its small ceramic thick-film substrate has a very high input impedance and is shielded by a guardring to minimize the influence of stray capacitance and microphonic interference.The GRAS 26CB is delivered with a built-in TEDS chip and can be programmed as a single unit with a microphone fitted.","brand":"GRAS","offers":[{"title":"Default Title","offer_id":48310084862285,"sku":"26CB","price":0.0,"currency_code":"DKK","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0755\/9344\/9805\/files\/26CB_Web.png?v=1701171993"},{"product_id":"gras-26cb-ht1-4-ccp-standard-preamplifier-with-microdot-connector","title":"GRAS 26CB-HT 1\/4\" CCP Standard Preamplifier with Microdot Connector","description":"Its small ceramic thick-film substrate has a very high input impedance and is shielded by a guardring to minimize the influence of stray capacitance and microphonic interference.The GRAS 26CB is delivered with a built-in TEDS chip and can be programmed as a single unit with a microphone fitted.","brand":"GRAS","offers":[{"title":"Default Title","offer_id":48310085091661,"sku":"26CB-HT","price":0.0,"currency_code":"DKK","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0755\/9344\/9805\/files\/26CB_Web_02e6bb4e-4353-45a8-96de-1ad06f4acfc9.png?v=1701172000"},{"product_id":"gras-26cc-1-4ccp-standard-preamplifier-with-smb-connector","title":"GRAS 26CC 1\/4\" CCP Standard Preamplifier with SMB Connector","description":"The GRAS 26CC 1\/4\" Preamplifier's small ceramic thick-film substrate has a very high input impedance, and is shielded by a guard ring to minimise the influence of stray capacitance and microphonic interference.","brand":"GRAS","offers":[{"title":"Default Title","offer_id":48310085189965,"sku":"26CC","price":0.0,"currency_code":"DKK","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0755\/9344\/9805\/files\/26CC_HiRes-RGB.png?v=1701172008"},{"product_id":"gras-26cf1-2-ccp-preamplifier-with-bnc-connector-gain-and-filters","title":"GRAS 26CF 1\/2'' CCP Preamplifier with BNC Connector, Gain and Filters","description":"The GRAS 26CF can be used with all GRAS prepolarized microphones, namely:\u003cul\u003e \t\u003cli class=\"firstItem\"\u003e1\/2-inch microphones: GRAS 40AE, 40AD and 40AQ\u003c\/li\u003e \t\u003cli class=\"lastItem\"\u003e1\/4-inch microphones: GRAS 40BE and 40BD, using the optional 1\/2-inch to 1\/4-inch adaptor RA0019\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"GRAS","offers":[{"title":"Default Title","offer_id":48310085222733,"sku":"26CF","price":0.0,"currency_code":"DKK","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0755\/9344\/9805\/files\/26CF_HiRes-RGB.png?v=1701172015"},{"product_id":"gras-26cg1-4-ccp-preamplifier-with-microdot-connector-low-frequency","title":"GRAS 26CG 1\/4\" CCP Preamplifier with Microdot Connector, Low Frequency","description":"All GRAS microphone preamplifiers are based on a small ceramic thick-film substrate with a very high input impedance. 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