RE: [AMRadio] 32V-2 speech amp question
I drilled many a hole in the past, and even took rigs apart to use for parts, back when people were giving them away ($50.00 for a 32v3, $200.00 for a 30k1, $10.00 for a dx100, etc. But no more, I build my own and do not ruin vintage stuff now. Restoring something is a good idea for those who want to play with the old stuff I guess. Brett > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of John E. > Coleman (ARS WA5BXO) > Sent: Monday, January 23, 2006 4:57 PM > To: 'Discussion of AM Radio' > Subject: RE: [AMRadio] 32V-2 speech amp question > > Well I didn't intend to open a bucket of worms here and > I certainly > do not want to stop anyone that wants to experiment from > doing so. Building > a rig that has really good HIFI is a real challenge and doing > it with out > phase shifts in the audio is a point of mine. Building the > rig to produce > very low frequencies but not using those frequencies is about > the only way > you can prevent phase shifts in the lower frequency > components. Because as > you approach a roll off there is a phase shift that occurs at > the knee of > the curve. This phase shift at the low frequency end will > alter the shape > of a complex wave that is non sinusoidal and has natural even > harmonics > (natural asymmetry). So for this reason I lean toward > building the rig for > extended low frequency response but not necessarily producing them in > transmission. Beside that, I think experimentation is good > for the brain. > I don't much care for have a piece of equipment to maintain > as antique. > They are all for my learning experience. And I may drill a > hole in the > front panel of anything. HIHI > I only wanted to point out what I have found to be true > in operating > it and receiving others. There is a time and place for all. > > John, WA5BXO > > > > > > > __ > AMRadio mailing list > Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:AMRadio@mailman.qth.net > AMfone Website: http://www.amfone.net > AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb >
RE: [AMRadio] 32V-2 speech amp question
BTW I would support a RM where all amateur radio licensees should have to build there on equipment. That should open up a bucket of worms!! John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of John E. Coleman (ARS WA5BXO) Sent: Monday, January 23, 2006 3:57 PM To: 'Discussion of AM Radio' Subject: RE: [AMRadio] 32V-2 speech amp question Well I didn't intend to open a bucket of worms here and I certainly do not want to stop anyone that wants to experiment from doing so. Building a rig that has really good HIFI is a real challenge and doing it with out phase shifts in the audio is a point of mine. Building the rig to produce very low frequencies but not using those frequencies is about the only way you can prevent phase shifts in the lower frequency components. Because as you approach a roll off there is a phase shift that occurs at the knee of the curve. This phase shift at the low frequency end will alter the shape of a complex wave that is non sinusoidal and has natural even harmonics (natural asymmetry). So for this reason I lean toward building the rig for extended low frequency response but not necessarily producing them in transmission. Beside that, I think experimentation is good for the brain. I don't much care for have a piece of equipment to maintain as antique. They are all for my learning experience. And I may drill a hole in the front panel of anything. HIHI I only wanted to point out what I have found to be true in operating it and receiving others. There is a time and place for all. John, WA5BXO __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net AMfone Website: http://www.amfone.net AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb
RE: [AMRadio] 32V-2 speech amp question
Well I didn't intend to open a bucket of worms here and I certainly do not want to stop anyone that wants to experiment from doing so. Building a rig that has really good HIFI is a real challenge and doing it with out phase shifts in the audio is a point of mine. Building the rig to produce very low frequencies but not using those frequencies is about the only way you can prevent phase shifts in the lower frequency components. Because as you approach a roll off there is a phase shift that occurs at the knee of the curve. This phase shift at the low frequency end will alter the shape of a complex wave that is non sinusoidal and has natural even harmonics (natural asymmetry). So for this reason I lean toward building the rig for extended low frequency response but not necessarily producing them in transmission. Beside that, I think experimentation is good for the brain. I don't much care for have a piece of equipment to maintain as antique. They are all for my learning experience. And I may drill a hole in the front panel of anything. HIHI I only wanted to point out what I have found to be true in operating it and receiving others. There is a time and place for all. John, WA5BXO
RE: [AMRadio] 32V-2 speech amp question
> This seems counterproductive to me. Why expend time and money on a > transmitter that can pass down to 10 cycles up to 15 Kc and > then restrict > it? Why not build one that will go down to 200 and up to 8. > Frequencies > below 200 Cy do not contribute to the information transmitted > and rob from > frequencies that do. There's a general rule that for best perceived or most natural voice quality, the low frequency cutoff times the high frequency cutoff (in cps) should be about 500,000. Obviously, both the transmit and receive end have an impact on this. If we assume a wide bandwidth receiver with good (flat) response, then a transmitter with a 5000 kc high end cutoff should have about a 100 cps low end. Or a transmitter that can handle 10 kcps on the high end should go down to 50 cps on the low end. Let's say it does that. Let's say my R390 is limiting high frequencies to 2 Kc because I am center tuned at 4 kc bandwidth because of nearby SSB. The perception I'll have of this beautiful transmit signal will be that it is all bass -- no articulation, and really hard to understand (confirmed by a lot of listening to weak "east coast sound" signals from 20V's or whatever). Even a 4 Kc high end transmitted with 50 Hz low end could sound bassy (depending on whether I'm an "accouncer" voice or a squeaker, no matter how the receive bandwidth is set. I usually run with about 150 Hz low freq cutoff, but then I'm a squeaker, and going much below that won't help :-) So I have to agree with you. If the guy on the 20V is "full quieting", and you can run your receive bandwidth wide open, then enjoy what there is to hear. Most of the time, it's just too much bandwidth (which doesn't mean we ought to be prohibited from doing that if conditions are right AND it can be done without causing undue interference). Grant/NQ5T
RE: [AMRadio] 32V-2 speech amp question
Because, if it does go down to say 50 cycles, and up to 15,000, it will be much cleaner and flatter running 100 to 5000 cycles. And when conditions are good, you might want to run it almost hifi, a good clean hifi signal is very nice to listen to. I cant say I spend much time and money in doing good sounding audio, its more like time and money having fun with ham radio. You want to talk cheap with communications audio, all you need is a cell phone really. Brett N2DTS > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Jim Wilhite > Sent: Monday, January 23, 2006 3:02 PM > To: Discussion of AM Radio > Subject: Re: [AMRadio] 32V-2 speech amp question > > > - Original Message - > From: "Brett gazdzinski" <[EMAIL PROTECTED]> > To: "'Discussion of AM Radio'" > Sent: Monday, January 23, 2006 10:53 AM > Subject: RE: [AMRadio] 32V-2 speech amp question > > > >I agree its pointless to run hifi at 100 watts, but making the rig > > able to run hifi, and then restricting it is a good way to go. > > > This seems counterproductive to me. Why expend time and money on a > transmitter that can pass down to 10 cycles up to 15 Kc and > then restrict > it? Why not build one that will go down to 200 and up to 8. > Frequencies > below 200 Cy do not contribute to the information transmitted > and rob from > frequencies that do. With some SSB groups that like to crowd the AM > operator, those low and high frequencies are filtered anyway. > > > As far as bandwidth goes, I hear much more problems from people over > > modulating > > than from people running hifi audio. That may cause some ssb guys to > > complain > > about AM. On 40 meters last weekend, I heard 4 stations in > the short time > > I > > was listening (Sunday morning) and 3 were over modding and > quite wide. > > The scope showed they were closing down the carrier quite > well, and were > > 15 > > kc wide. > > > > > > I assume most AM guys on 40 have no way to monitor their > modulation and > > just turn it up to what the book says, then a little more. > > Or they set it up on the scope, and when they operate, they > get excited > > and talk louder or something. > > > > I feel if you are going to operate AM, you need to be able to > > see and hear your modulation. The ssb guys do not have > problems as much as > > they have ALC built into their rigs. > > > > Brett > > N2DTS > > > > > This is a particularly bad problem near where I live. Not > everyone does it, > but a significant few do and they cause problems for all in > this area. The > bad thing is they don't really know how to set the modulation > on a scope. > Some of them monitor their audio signal off air and think > they can do it by > ear. It is one thing to have a wide signal and totally > another to have one > because of overmodulation. > > 73 Jim > W5JO > > > __ > AMRadio mailing list > Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:AMRadio@mailman.qth.net > AMfone Website: http://www.amfone.net > AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb >
Re: [AMRadio] 32V-2 speech amp question
- Original Message - From: "Brett gazdzinski" <[EMAIL PROTECTED]> To: "'Discussion of AM Radio'" Sent: Monday, January 23, 2006 10:53 AM Subject: RE: [AMRadio] 32V-2 speech amp question I agree its pointless to run hifi at 100 watts, but making the rig able to run hifi, and then restricting it is a good way to go. This seems counterproductive to me. Why expend time and money on a transmitter that can pass down to 10 cycles up to 15 Kc and then restrict it? Why not build one that will go down to 200 and up to 8. Frequencies below 200 Cy do not contribute to the information transmitted and rob from frequencies that do. With some SSB groups that like to crowd the AM operator, those low and high frequencies are filtered anyway. As far as bandwidth goes, I hear much more problems from people over modulating than from people running hifi audio. That may cause some ssb guys to complain about AM. On 40 meters last weekend, I heard 4 stations in the short time I was listening (Sunday morning) and 3 were over modding and quite wide. The scope showed they were closing down the carrier quite well, and were 15 kc wide. I assume most AM guys on 40 have no way to monitor their modulation and just turn it up to what the book says, then a little more. Or they set it up on the scope, and when they operate, they get excited and talk louder or something. I feel if you are going to operate AM, you need to be able to see and hear your modulation. The ssb guys do not have problems as much as they have ALC built into their rigs. Brett N2DTS This is a particularly bad problem near where I live. Not everyone does it, but a significant few do and they cause problems for all in this area. The bad thing is they don't really know how to set the modulation on a scope. Some of them monitor their audio signal off air and think they can do it by ear. It is one thing to have a wide signal and totally another to have one because of overmodulation. 73 Jim W5JO
RE: [AMRadio] 32V-2 speech amp question
> Well, I've been flying airplanes since 1968 and have given up > trying to explain ANYTHING to the FAA . You have a point there :-) Grant/NQ5T
Re: [AMRadio] 32V-2 speech amp question
Grant Youngman wrote: "... Using AM as a pure, clinical communications mode is illogical. Explain that to the FAA :-)" Well, I've been flying airplanes since 1968 and have given up trying to explain ANYTHING to the FAA . Actually, I think the agency's continued use of AM proves my point :-) . 73, Craig W3CRR
RE: [AMRadio] 32V-2 speech amp question
> ... Using AM as a pure, clinical communications mode is illogical. Explain that to the FAA :-) Grant/NQ5T
RE: [AMRadio] 32V-2 speech amp question
Hi John, I think this "hi-fi" thing gets carried a little far with a lot of people. I agree with you that most sound "not so good" with narrow receiver filters. Like you say unless it is a pretty much local qso you can't use wide bandwidth on the receiver. There is a lot of energy in the low frequencies. They do little for intelligibility. But if they are present they take away modulation power from the more usable frequencies in the audio bandwidth. The low frequencies will over modulate the transmitter before the mid range frequencies will so that limits the amount of energy that you can apply to the more useful mid-range. 73 Gary K4FMX > -Original Message- > From: [EMAIL PROTECTED] [mailto:amradio- > [EMAIL PROTECTED] On Behalf Of John E. Coleman (ARS WA5BXO) > Sent: Monday, January 23, 2006 11:19 AM > To: 'Discussion of AM Radio' > Subject: RE: [AMRadio] 32V-2 speech amp question > > The 32V driver is certainly adequate for the specifications of the > rig. I might add that the specifications in fidelity are fine for me. I > think it and the 75A4 receiver could do better on THD. However, I think > Craig was looking for more fidelity. This might be a good time for me to > inject the Woos of HiFI. HIFI is OK for use on ground wave without > selective fading and of course when the spectrum is void of other QSOs. > The > problem that I have is the QRM/QRN that accompanies cross country QSOs > when > the band is open for that type of propagation. I narrow up the RCVR to > get > a better signal to noise ratio and that's when I begin understand the > problems of having bass without treble. I'm talking bass below 100 CPS. > It > sounds great when with a wide band pass and assuming the XMTR is passing > treble out to 15KHZ. But when you narrow down to 6-8 KHZ you need to roll > the lows of starting at 200HZ and eliminate them below 75HZ. I don't like > 60 CPS hum so I switch to a small very desk top speaker or cheap head > phones > to eliminate the bass. The XTMR would do better in this case not > transmitting the low bass but instead putting the energy into low > distortion > limited band width audio. > > This takes me to the new RMs that or in place. I can see all the sides as > having made good points. And I just don't know what to do. I feel that > the > FCC is going to get annoyed at the whole thing and wash there hands of it > and I don't know where that will leave us. > > John, WA5BXO > > > > -Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Brett gazdzinski > Sent: Sunday, January 22, 2006 7:04 PM > To: 'Discussion of AM Radio' > Subject: RE: [AMRadio] 32V-2 speech amp question > > Keep in mind, the input impedance is very high, 1 meg at the mike > input stock radio. No transformer on the mike input in the 32v series. > I thought the driver transformer was adequate, its very large for a driver > transformer, the > DX100 has a postage stamp, the 32v had a fist sized driver transformer. > > I use a pair of KT88 tubes as modulators and don't use the driver > transformer > (gave it away a long time ago). If you run the high impedance mike preamp > in > the > rig and want some hifi, you have to run the mike preamp tube off DC. > I just did 1/2 wave (1 diode) and an electrolytic cap. The size of the cap > sets > the voltage the filament runs at. > The DC does not need to be pure, even rough DC will eliminate hum. > > Neg feedback, regulated voltage on the mod tube screens, large coupling > caps > will get you a long way to a good sounding 32V. > Brett > N2DTS > > > > > -Original Message- > > From: [EMAIL PROTECTED] > > [mailto:[EMAIL PROTECTED] On Behalf Of John > > Coleman ARS WA5BXO > > Sent: Sunday, January 22, 2006 11:03 AM > > To: 'Discussion of AM Radio' > > Subject: RE: [AMRadio] 32V-2 speech amp question > > > > I have not driven it externally before Craig but have some > > experience with the circuitry and the driver XFMR is a weak > > link in the > > circuit the XFMR barely has enough iron and coupling > > coefficiency in it > > to pass the low frequencies that the rig is designed for. As a matter > > of fact if the cathode resistor of the driver stage drops in > > resistance, > > as they or known to do with heat, the driver plate current > > will quickly > > saturate the driver XFMR causing the bass frequencies to look like a > > trapezoid instead of sine wave. If you were going to go with and > > outboard amplifier I would include a better driver XFMR as part of the &
Re: [AMRadio] 32V-2 speech amp question
John Coleman wrote, in part: "This might be a good time for me to inject the Woes of HiFI. HIFI is OK for use on ground wave without selective fading and of course when the spectrum is void of other QSOs. The problem that I have is the QRM/QRN that accompanies cross country QSOs when the band is open for that type of propagation" I connot deny that John makes some very good points. What I'm seeking, however, is a transmitter that is CAPABLE of high fidelity audio transmission when conditions are appropriate. The audio bandwidth can be controlled at the input end by processing -- from sophisticated, multi-layer schemes to simple microphone selection (an Astatic D-104 instead of a Neumann U 87, for instance) and thus tailor the transmission for the current propagation and adjacent traffic. But, when the band's quiet and we've got an "armchair" QSO going -- which is not all that unusual -- I like to transmit (and listen to) mellow, rich, high fidelity audio. I strive for true, high-end "broadcast quality" audio on AM for two reasons. One is -- admittedly -- vanity. I'm an old broadcaster --need I say more? The other reason for my quest for hi-fi is to justify -- or rationalize -- the use of amplitude modulation. After all,, the digital modes and even SSB and CW are far more "robust" than AM and are vastly superior in the efficient and reliable exchange of data. Using AM as a pure, clinical communications mode is illogical. Most of us, I suspect, employ our AM gear solely for sentimental reasons. Some of us are taking a "busman's holiday" during our operating hours. Others are reliving nostalgia-sweetened memories of their early days in amateur radio. Still others are celebrating the romance of old technology. I'm doing all three and, in the end, that's why my largest single fiscal investment in ham gear (ever!) has been in my 32V-2 and R-388 combo. I could sell these beautifully crafted, lovingly restored (by Howard Mills) items and "upgrade" to a Ten Tec Orion, if I wished. Logically, that's what I should do. Somehow, though, it just wouldn't be the same. 73, Craig W3CRR
RE: [AMRadio] 32V-2 speech amp question
I agree its pointless to run hifi at 100 watts, but making the rig able to run hifi, and then restricting it is a good way to go. That is why I use the d104 with the 32v, a nice mid range punch, with a bit of some lows in there to stop it from sounding like a cheap phone. I hear plenty of weak signals on 40 meters, guys running 50 to 100 watts and full fidelity, at least the bass, and they are hard to copy over the stock sound of most rigs. I always thought the 75A4 sucked on AM, as most Collins receivers do, poor detectors, poor audio amps, poor filter choices. The Collins design R390/a was good if noisy, but that was the only one I ever found to sound good on AM. As far as bandwidth goes, I hear much more problems from people over modulating than from people running hifi audio. That may cause some ssb guys to complain about AM. On 40 meters last weekend, I heard 4 stations in the short time I was listening (Sunday morning) and 3 were over modding and quite wide. The scope showed they were closing down the carrier quite well, and were 15 kc wide. I assume most AM guys on 40 have no way to monitor their modulation and just turn it up to what the book says, then a little more. Or they set it up on the scope, and when they operate, they get excited and talk louder or something. I feel if you are going to operate AM, you need to be able to see and hear your modulation. The ssb guys do not have problems as much as they have ALC built into their rigs. Brett N2DTS > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of John E. > Coleman (ARS WA5BXO) > Sent: Monday, January 23, 2006 11:19 AM > To: 'Discussion of AM Radio' > Subject: RE: [AMRadio] 32V-2 speech amp question > > The 32V driver is certainly adequate for the > specifications of the > rig. I might add that the specifications in fidelity are > fine for me. I > think it and the 75A4 receiver could do better on THD. > However, I think > Craig was looking for more fidelity. This might be a good > time for me to > inject the Woos of HiFI. HIFI is OK for use on ground wave without > selective fading and of course when the spectrum is void of > other QSOs. The > problem that I have is the QRM/QRN that accompanies cross > country QSOs when > the band is open for that type of propagation. I narrow up > the RCVR to get > a better signal to noise ratio and that's when I begin understand the > problems of having bass without treble. I'm talking bass > below 100 CPS. It > sounds great when with a wide band pass and assuming the XMTR > is passing > treble out to 15KHZ. But when you narrow down to 6-8 KHZ you > need to roll > the lows of starting at 200HZ and eliminate them below 75HZ. > I don't like > 60 CPS hum so I switch to a small very desk top speaker or > cheap head phones > to eliminate the bass. The XTMR would do better in this case not > transmitting the low bass but instead putting the energy into > low distortion > limited band width audio. > > This takes me to the new RMs that or in place. I can see all > the sides as > having made good points. And I just don't know what to do. > I feel that the > FCC is going to get annoyed at the whole thing and wash there > hands of it > and I don't know where that will leave us. > > John, WA5BXO > > > > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Brett gazdzinski > Sent: Sunday, January 22, 2006 7:04 PM > To: 'Discussion of AM Radio' > Subject: RE: [AMRadio] 32V-2 speech amp question > > Keep in mind, the input impedance is very high, 1 meg at the mike > input stock radio. No transformer on the mike input in the 32v series. > I thought the driver transformer was adequate, its very large > for a driver > transformer, the > DX100 has a postage stamp, the 32v had a fist sized driver > transformer. > > I use a pair of KT88 tubes as modulators and don't use the driver > transformer > (gave it away a long time ago). If you run the high impedance > mike preamp in > the > rig and want some hifi, you have to run the mike preamp tube off DC. > I just did 1/2 wave (1 diode) and an electrolytic cap. The > size of the cap > sets > the voltage the filament runs at. > The DC does not need to be pure, even rough DC will eliminate hum. > > Neg feedback, regulated voltage on the mod tube screens, > large coupling caps > will get you a long way to a good sounding 32V. > Brett > N2DTS > > > > > -Original Message- > > From: [EMAIL PROTECTED] > > [mailto:[EMAIL PROTECTED] On Behalf Of John > > Coleman ARS WA5BXO > &g
RE: [AMRadio] 32V-2 speech amp question
The 32V driver is certainly adequate for the specifications of the rig. I might add that the specifications in fidelity are fine for me. I think it and the 75A4 receiver could do better on THD. However, I think Craig was looking for more fidelity. This might be a good time for me to inject the Woos of HiFI. HIFI is OK for use on ground wave without selective fading and of course when the spectrum is void of other QSOs. The problem that I have is the QRM/QRN that accompanies cross country QSOs when the band is open for that type of propagation. I narrow up the RCVR to get a better signal to noise ratio and that's when I begin understand the problems of having bass without treble. I'm talking bass below 100 CPS. It sounds great when with a wide band pass and assuming the XMTR is passing treble out to 15KHZ. But when you narrow down to 6-8 KHZ you need to roll the lows of starting at 200HZ and eliminate them below 75HZ. I don't like 60 CPS hum so I switch to a small very desk top speaker or cheap head phones to eliminate the bass. The XTMR would do better in this case not transmitting the low bass but instead putting the energy into low distortion limited band width audio. This takes me to the new RMs that or in place. I can see all the sides as having made good points. And I just don't know what to do. I feel that the FCC is going to get annoyed at the whole thing and wash there hands of it and I don't know where that will leave us. John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Brett gazdzinski Sent: Sunday, January 22, 2006 7:04 PM To: 'Discussion of AM Radio' Subject: RE: [AMRadio] 32V-2 speech amp question Keep in mind, the input impedance is very high, 1 meg at the mike input stock radio. No transformer on the mike input in the 32v series. I thought the driver transformer was adequate, its very large for a driver transformer, the DX100 has a postage stamp, the 32v had a fist sized driver transformer. I use a pair of KT88 tubes as modulators and don't use the driver transformer (gave it away a long time ago). If you run the high impedance mike preamp in the rig and want some hifi, you have to run the mike preamp tube off DC. I just did 1/2 wave (1 diode) and an electrolytic cap. The size of the cap sets the voltage the filament runs at. The DC does not need to be pure, even rough DC will eliminate hum. Neg feedback, regulated voltage on the mod tube screens, large coupling caps will get you a long way to a good sounding 32V. Brett N2DTS > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of John > Coleman ARS WA5BXO > Sent: Sunday, January 22, 2006 11:03 AM > To: 'Discussion of AM Radio' > Subject: RE: [AMRadio] 32V-2 speech amp question > > I have not driven it externally before Craig but have some > experience with the circuitry and the driver XFMR is a weak > link in the > circuit the XFMR barely has enough iron and coupling > coefficiency in it > to pass the low frequencies that the rig is designed for. As a matter > of fact if the cathode resistor of the driver stage drops in > resistance, > as they or known to do with heat, the driver plate current > will quickly > saturate the driver XFMR causing the bass frequencies to look like a > trapezoid instead of sine wave. If you were going to go with and > outboard amplifier I would include a better driver XFMR as part of the > external circuit and go to the grids directly. > > John > Coleman > > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Craig Roberts > Sent: Saturday, January 21, 2006 10:19 PM > To: Discussion of AM Radio > Subject: [AMRadio] 32V-2 speech amp question > > Has anyone tried driving the mod input transformer of the > 32V-2 (or V-3) > > directly with an outboard mic preamp? If so, what were the results, > please? > > Many thanks and 73, > > Craig > W3CRR > __ > AMRadio mailing list > Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:AMRadio@mailman.qth.net > AMfone Website: http://www.amfone.net > AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb > > > > __ > AMRadio mailing list > Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:AMRadio@mailman.qth.net > AMfone Website: http://www.amfone.net > AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb > __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net AMfone Website: http://www.amfone.net AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb
RE: [AMRadio] 32V-2 speech amp question
Keep in mind, the input impedance is very high, 1 meg at the mike input stock radio. No transformer on the mike input in the 32v series. I thought the driver transformer was adequate, its very large for a driver transformer, the DX100 has a postage stamp, the 32v had a fist sized driver transformer. I use a pair of KT88 tubes as modulators and don't use the driver transformer (gave it away a long time ago). If you run the high impedance mike preamp in the rig and want some hifi, you have to run the mike preamp tube off DC. I just did 1/2 wave (1 diode) and an electrolytic cap. The size of the cap sets the voltage the filament runs at. The DC does not need to be pure, even rough DC will eliminate hum. Neg feedback, regulated voltage on the mod tube screens, large coupling caps will get you a long way to a good sounding 32V. Brett N2DTS > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of John > Coleman ARS WA5BXO > Sent: Sunday, January 22, 2006 11:03 AM > To: 'Discussion of AM Radio' > Subject: RE: [AMRadio] 32V-2 speech amp question > > I have not driven it externally before Craig but have some > experience with the circuitry and the driver XFMR is a weak > link in the > circuit the XFMR barely has enough iron and coupling > coefficiency in it > to pass the low frequencies that the rig is designed for. As a matter > of fact if the cathode resistor of the driver stage drops in > resistance, > as they or known to do with heat, the driver plate current > will quickly > saturate the driver XFMR causing the bass frequencies to look like a > trapezoid instead of sine wave. If you were going to go with and > outboard amplifier I would include a better driver XFMR as part of the > external circuit and go to the grids directly. > > John > Coleman > > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Craig Roberts > Sent: Saturday, January 21, 2006 10:19 PM > To: Discussion of AM Radio > Subject: [AMRadio] 32V-2 speech amp question > > Has anyone tried driving the mod input transformer of the > 32V-2 (or V-3) > > directly with an outboard mic preamp? If so, what were the results, > please? > > Many thanks and 73, > > Craig > W3CRR > __ > AMRadio mailing list > Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:AMRadio@mailman.qth.net > AMfone Website: http://www.amfone.net > AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb > > > > __ > AMRadio mailing list > Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:AMRadio@mailman.qth.net > AMfone Website: http://www.amfone.net > AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb >
RE: [AMRadio] 32V-2 speech amp question
I have not driven it externally before Craig but have some experience with the circuitry and the driver XFMR is a weak link in the circuit the XFMR barely has enough iron and coupling coefficiency in it to pass the low frequencies that the rig is designed for. As a matter of fact if the cathode resistor of the driver stage drops in resistance, as they or known to do with heat, the driver plate current will quickly saturate the driver XFMR causing the bass frequencies to look like a trapezoid instead of sine wave. If you were going to go with and outboard amplifier I would include a better driver XFMR as part of the external circuit and go to the grids directly. John Coleman -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Craig Roberts Sent: Saturday, January 21, 2006 10:19 PM To: Discussion of AM Radio Subject: [AMRadio] 32V-2 speech amp question Has anyone tried driving the mod input transformer of the 32V-2 (or V-3) directly with an outboard mic preamp? If so, what were the results, please? Many thanks and 73, Craig W3CRR __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net AMfone Website: http://www.amfone.net AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb
