Re: [Drakelist] D104 and TR7
Note: if the high level input pin is used, the load is 470K + the low level impedance. I use 470K for the series resitor, for a total of around a meg. Jim, Excellent point. If you were going to use the D104 with a modern DSP-based transceiver, I would have suggested gutting the Astatic preamp and replace it with one of the FET buffer circuits shown on my QRZ.com page. I should think that the resistor method would work with just about any rig that will accept a low-Z dymanic mic. Agreed, as long as the series resistor remains within reasonable limits, like your 470K example. SNR of the preamp diminishes with the an increase in series R from the crystal element. I measured this effect a while back when trying to optimize the series R level into the gate of an FET. Above about 500K, it becomes worthwhile to investigate a low-noise FET to unload the crystal element. The higher the series R value, the more important the choice in the noise figure of the first AF stage transistor. For FETs, I like the LSK170. For BJTs, the Toshiba BC550 and BC560 are excellent where input loading Z is not much of a concern. For SSB transmitters using crystal filtering (e.g., 2.4K I.F. filter) , I cannot imagine the need to go above 500K of series R from the D104 element. There's no way the resulting response through a traditional filter is going to increase -- like it does for AM transmission or ESSB-capable transmitters. One can often move the carrier set point to a different point on the crystal filter curve but that comes at the expense of either the upper or lower audio response, depending on the set point shift. And, that can introduce frequency reading errors in transceivers that have no means to compensate. The stock Astatic 2-stage preamp is an engineering disaster IMO. It uses a strange variation of collector feedback bias and has far too much gain available to the operator. For the number of parts involved, it offers poor noise, gain, and response performance. It could definitely benefit from negative feedback that's consistent across the usable audio range. By the way, the input Z of Astatic's 2-stage preamp computes to roughly 450K. So, it's reasonably unloading the element for SSB users. But sonically, it's not up to the task. Paul, W9AC ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
[Drakelist] D104 and TR7
*Thanks Guys for the help, I will install a 470K resistor in the Mic. I appreciated all the feedback but remember I said I was a pretty good Toolmaker/Machinist not a electronics man so a LOT of the reply's was WAY above this Old Country Boy's head. * *Thanks * Woody ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] D104 and TR7
On Thu, 7 Jul 2011 06:51:00 -0400, Paul Christensen wrote: The stock Astatic 2-stage preamp is an engineering disaster IMO. So, I'm not too far off the mark in calling it anabomination? :) Generally speaking, I'm against preamped mics except in the case of rigs that require them (i.e., radios designed to run with a high output electret). I make an exception for my Turner +3, which scored higher than my D-104s in on the air checks with a couple of friends. Basically it's a 7075 with a compressor amp in the base. Looking at the schematic, when I run the non-amped D-104 +470K into the SP-75 speech processor, it sees a 2N5953 JFET preamp with a Meg in the gate circuit. So I don't really need the extra 470K, but I leave it in there in case I wan to use the mic without the SP-75 or with another rig. It works... 73 -Jim -- Ham Radio NU0C Lincoln, Nebraska, U.S.S.A. TR7/RV7/R7A/L7, TR6/RV6, T4XC/R4C/L4B, NCL2000, SB104A, R390A, GT550A/RV550A, HyGain 3750, IBM PS/2 - all vintage, all the time! Give a man a URL, and he will learn for an hour; teach him to Google, and he will learn for a lifetime. HyGain 3750 User's Group - http://groups.yahoo.com/group/HyGain_3750/ http://incolor.inetnebr.com/jshorney http://www.nebraskaghosts.org ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] D104 and TR7
On Wed, 6 Jul 2011 22:34:15 -0700, Richard Knoppow wrote: I am somewhat surprized that the frequency responce is affected enough to be heard through the rather narrow and sharp filters in modern SSB rigs. Depends on the rig and the D-104, to a degree. A non-amped D-104 on a rig with 50K input impedance will tend to sound tinny. The 470K series resistor helps. My friends can note disitinctive differences in sound between the D-104, the 444D, and the 7077. Not so much of a difference between the 254HC, EV, +3, and D-104, but it's there. 73 -Jim -- Ham Radio NU0C Lincoln, Nebraska, U.S.S.A. TR7/RV7/R7A/L7, TR6/RV6, T4XC/R4C/L4B, NCL2000, SB104A, R390A, GT550A/RV550A, HyGain 3750, IBM PS/2 - all vintage, all the time! Give a man a URL, and he will learn for an hour; teach him to Google, and he will learn for a lifetime. HyGain 3750 User's Group - http://groups.yahoo.com/group/HyGain_3750/ http://incolor.inetnebr.com/jshorney http://www.nebraskaghosts.org ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
[Drakelist] D104 and TR7
*Does any one know the mod to make the 104 work well with the TR7, I was told you added a **resistor of some value but they didn't know the value or where to put it. I need to know it at the Mod's for Dummies level, I was a Toolmaker not a electronics man, well just enough to be dangerous and stay alive. * Thanks Woody -- ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] D104 and TR7
Woody, You can add a 100K resistor in the D104's + mic lead. That will help to unload the crystal element from the TR-7's moderately low input Z. Same is true if your D104 uses Astatic's 2-transistor preamp/buffer circuit. The input Z of Astatic's preamp is still too low to take full advantage of an unloaded crystal mic element. On the other hand, the TR-7's SSB transmit filter will strip away much of the full-bodied audio from the D104. So, apart from adding the 100k resistor, I wouldn't change anything else. If you were going to use the D104 with a modern DSP-based transceiver, I would have suggested gutting the Astatic preamp and replace it with one of the FET buffer circuits shown on my QRZ.com page. Paul, W9AC - Original Message - From: Woody To: Drake List Sent: Wednesday, July 06, 2011 9:19 PM Subject: [Drakelist] D104 and TR7 Does any one know the mod to make the 104 work well with the TR7, I was told you added a resistor of some value but they didn't know the value or where to put it. I need to know it at the Mod's for Dummies level, I was a Toolmaker not a electronics man, well just enough to be dangerous and stay alive. Thanks Woody -- -- ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] D104 and TR7
Woody, I've heard of numerous people using the D-104 with the TR-7 as discussed on the Drake nets. Values I've heard range from 470K to 1.3 meg in series with the mic hot lead. If there is a speech pre-amp in the mic, it should not be used. 73, Evan, K9SQG -Original Message- From: Woody ko4...@gmail.com To: Drake List drakelist@zerobeat.net Sent: Wed, Jul 6, 2011 9:19 pm Subject: [Drakelist] D104 and TR7 Does any one know the mod to make the 104 work well with the TR7, I was told you added a resistor of some value but they didn't know the value or where to put it. I need to know it at the Mod's for Dummies level, I was a Toolmaker not a electronics man, well just enough to be dangerous and stay alive. Thanks Woody -- ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] D104 and TR7
Why wouldn't you use the preamp? While there may be better preamp circuits out there, even the preamp in an amplified Astatic stand sounds decent if it's used properly. Turn it all the way down. Set the rig's mic gain at about 10:00, and then SLOWLY advance the gain of the preamp for normal modulation. The biggest problem happens when you just crank it all the way up for that good buddy effect. I've used amp'd d104 and 10D mics on rigs of all kinds (including Drake's of all kinds without getting cr*p for audio. The preamp eliminates the need to be concerned about matching the input Z of the radio and eliminates the effect of the input Z of the radio on the freq response of the mic. Grant/NQ5T Sent from my iPhone On Jul 6, 2011, at 8:47 PM, K9sqg k9...@aol.com wrote: Woody, I've heard of numerous people using the D-104 with the TR-7 as discussed on the Drake nets. Values I've heard range from 470K to 1.3 meg in series with the mic hot lead. If there is a speech pre-amp in the mic, it should not be used. 73, Evan, K9SQG -Original Message- From: Woody ko4...@gmail.com To: Drake List drakelist@zerobeat.net Sent: Wed, Jul 6, 2011 9:19 pm Subject: [Drakelist] D104 and TR7 Does any one know the mod to make the 104 work well with the TR7, I was told you added a resistor of some value but they didn't know the value or where to put it. I need to know it at the Mod's for Dummies level, I was a Toolmaker not a electronics man, well just enough to be dangerous and stay alive. Thanks Woody -- ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] D104 and TR7
That's true. But if one has an amplified stand it will work fine, too. Sent from my iPhone On Jul 6, 2011, at 10:13 PM, K9sqg k9...@aol.com wrote: Grant, There is no real need for the pre-amp circuit when the D-104 is used with the TR-7, more than enough gain exists. Don't have to replace the battery every year or two either. At any rate, it is personal preference. 73, Evan - ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] D104 and TR7
On Wed, 6 Jul 2011 22:26:44 -0500, Grant Youngman wrote: That's true. But if one has an amplified stand it will work fine, too. Better without. It's extra gain that is not needed, and it adds another failure point and a point for feedback and distortion to enter. I've gotten excellent results by removing the amlifier and using the old-timer's trick of the series 470K resistor. The result beats out most of my other mics, although the Turners and the EV are real close. 444 and 7075, not so much, although the 444 gets the a nod for it's natural sound suitable for casual armchair copy QSOing. 73 -Jim -- Ham Radio NU0C Lincoln, Nebraska, U.S.S.A. TR7/RV7/R7A/L7, TR6/RV6, T4XC/R4C/L4B, NCL2000, SB104A, R390A, GT550A/RV550A, HyGain 3750, IBM PS/2 - all vintage, all the time! Give a man a URL, and he will learn for an hour; teach him to Google, and he will learn for a lifetime. HyGain 3750 User's Group - http://groups.yahoo.com/group/HyGain_3750/ http://incolor.inetnebr.com/jshorney http://www.nebraskaghosts.org ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] D104 and TR7
On Wed, 6 Jul 2011 21:23:08 -0500, Grant Youngman wrote: Why wouldn't you use the preamp? Because you don't need it, and it can cause more trouble than it's worth. The preamp eliminates the need to be concerned about matching the input Z of the radio and eliminates the effect of the input Z of the radio on the freq response of the mic. No concern at all with the Drakes, see my previous posts. The cartridge has high output, and the higher the load impedance, the better they tend to sound. I always got exellent reports feeding through a collective total of close to 1 Meg resistive into the TR-7. 73 -Jim -- Ham Radio NU0C Lincoln, Nebraska, U.S.S.A. TR7/RV7/R7A/L7, TR6/RV6, T4XC/R4C/L4B, NCL2000, SB104A, R390A, GT550A/RV550A, HyGain 3750, IBM PS/2 - all vintage, all the time! Give a man a URL, and he will learn for an hour; teach him to Google, and he will learn for a lifetime. HyGain 3750 User's Group - http://groups.yahoo.com/group/HyGain_3750/ http://incolor.inetnebr.com/jshorney http://www.nebraskaghosts.org ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] D104 and TR7
On Wed, 6 Jul 2011 21:33:11 -0400, Paul Christensen wrote: You can add a 100K resistor in the D104's + mic lead. That will help to unload the crystal element from the TR-7's moderately low input Z. Note: if the high level input pin is used, the load is 470K + the low level impedance. I use 470K for the series resitor, for a total of around a meg. If you were going to use the D104 with a modern DSP-based transceiver, I would have suggested gutting the Astatic preamp and replace it with one of the FET buffer circuits shown on my QRZ.com page. I should think that the resistor method would work with just about any rig that will accept a low-Z dymanic mic. 73 -Jim -- Ham Radio NU0C Lincoln, Nebraska, U.S.S.A. TR7/RV7/R7A/L7, TR6/RV6, T4XC/R4C/L4B, NCL2000, SB104A, R390A, GT550A/RV550A, HyGain 3750, IBM PS/2 - all vintage, all the time! Give a man a URL, and he will learn for an hour; teach him to Google, and he will learn for a lifetime. HyGain 3750 User's Group - http://groups.yahoo.com/group/HyGain_3750/ http://incolor.inetnebr.com/jshorney http://www.nebraskaghosts.org ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] D104 and TR7
- Original Message - From: Jim Shorney jshor...@inebraska.com To: drakelist@zerobeat.net Sent: Wednesday, July 06, 2011 9:16 PM Subject: Re: [Drakelist] D104 and TR7 On Wed, 6 Jul 2011 22:26:44 -0500, Grant Youngman wrote: That's true. But if one has an amplified stand it will work fine, too. Better without. It's extra gain that is not needed, and it adds another failure point and a point for feedback and distortion to enter. I've gotten excellent results by removing the amlifier and using the old-timer's trick of the series 470K resistor. The result beats out most of my other mics, although the Turners and the EV are real close. 444 and 7075, not so much, although the 444 gets the a nod for it's natural sound suitable for casual armchair copy QSOing. 73 -Jim FWIW, crystal and ceramic microphones have purely capacitive internal impedance, that is they look like a capacitor. Ideally, they want to look at in infinite impedance. When you put it in parallel with a resistor it forms a high pass filter, that is, the bass will be rolled off. A series resistor will keep the low end up at the expense of some loss of level. The other thing to be careful of is cable capacitance. That will tend to roll off the high frequencies because the impedance of the mic is so high. Probably the ideal input device is a vacuum tube with an open grid or one with grid leak bias. There is probably a solid state equivalent to that. I am somewhat surprized that the frequency responce is affected enough to be heard through the rather narrow and sharp filters in modern SSB rigs. -- Richard Knoppow Los Angeles WB6KBL dickb...@ix.netcom.com ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
