This pre could process signals in excess of 100 MHz and with a Slew rate of 200V/uSec! The printed board proposed it's not capable to meet Rf requisites for this proposed assembly!
Questo pre può processare segnali Rf da 100 e più MHz con SR da 200 V/Usec e più!
Servirebbe un cablaggio per Rf con circuito doppia faccia ed estesi piani di massa! Il circuito stampato proposto , secondo me, non ha i requisiti: Meglio sarebbe rifare un clone anche nel cablaggio!
Questo pre può processare segnali Rf da 100 e più MHz con SR da 200 V/Usec e più!
Servirebbe un cablaggio per Rf con circuito doppia faccia ed estesi piani di massa! Il circuito stampato proposto , secondo me, non ha i requisiti: Meglio sarebbe rifare un clone anche nel cablaggio!
cablaggio tipo radioline anni 70 .....na ficata .
questo stampato e' doppia faccia ma lasciamo perdere.
Scusami, non volevo offenderti, non era mia intenzione, il mio inglese come avrai potuto notare è pessimo ma avevo infilato il mio commento in italiano, succinto perchè siamo in un forum straniero e dovremmo fare capire anche ad altri quello che sta succedendo.
Conosco bene questo progetto e niente mi farebbe più felice di poterlo riprodurre, tanto è vero che mi sono subito impegnato. Mi sono studiato sia il circuito che il tuo circuito stampato e purtroppo questo attuale non è all'altezza della bisogna. Questo non impedisce che si possa studiare una altra opzione. probabilmente la soluzione migliore sarebbe replicare il cablaggio originale, anche così però, resta il fatto che il circuito E' DI FATTO UN AMPLIFICATORE RF e come tale deve essere trattato. Tra l'altro non tutti i U 709 vanno bene ma ci vogliono quelli in ceramica oppure esemplari selezionati per avere capacità di trattare RF. La genialità del progetto (NASA) è quella di usare gli stadi d'ingresso del circuito integrato ma di sostituire lo stadio d'uscita con un altro in grado di trattare segnali a frequenza altissima (si notano capacità di compensazione sul circuito) e valori resistivi custom circuito per circuito per avere ottimizzazione RF). La banda passante è così larga che molte volte, in Italia, grazie alle stazioni FM commerciali il pre funziona anche senza essere acceso in quanto i campi RF delle radio libere sono in grado di fare funzionare il pre anche senza alimentazione. Detto questo, a parte il sarcasmo su cablaggi radioline, cosa intendi fare? Ti prego di farmi sapere, grazie.
saluti cordiali cicero32
Conosco bene questo progetto e niente mi farebbe più felice di poterlo riprodurre, tanto è vero che mi sono subito impegnato. Mi sono studiato sia il circuito che il tuo circuito stampato e purtroppo questo attuale non è all'altezza della bisogna. Questo non impedisce che si possa studiare una altra opzione. probabilmente la soluzione migliore sarebbe replicare il cablaggio originale, anche così però, resta il fatto che il circuito E' DI FATTO UN AMPLIFICATORE RF e come tale deve essere trattato. Tra l'altro non tutti i U 709 vanno bene ma ci vogliono quelli in ceramica oppure esemplari selezionati per avere capacità di trattare RF. La genialità del progetto (NASA) è quella di usare gli stadi d'ingresso del circuito integrato ma di sostituire lo stadio d'uscita con un altro in grado di trattare segnali a frequenza altissima (si notano capacità di compensazione sul circuito) e valori resistivi custom circuito per circuito per avere ottimizzazione RF). La banda passante è così larga che molte volte, in Italia, grazie alle stazioni FM commerciali il pre funziona anche senza essere acceso in quanto i campi RF delle radio libere sono in grado di fare funzionare il pre anche senza alimentazione. Detto questo, a parte il sarcasmo su cablaggi radioline, cosa intendi fare? Ti prego di farmi sapere, grazie.
saluti cordiali cicero32
My friend here says that my pcb not work but he does not explain why ' .
he says that the bandwidth of the agi511 is so large that many times , in Italy , thanks to the pre commercial FM stations also works without being turned on because the RF field of free radios are able to run the pre without power .
AGI Pre- A prayer to Mr Curl.
AGI preamplifier is a preamplifier with a bandpass of more than 100MHz and with an elevated Slew Rate (nearly 200 V/Usec). This is due to project able to process RF signals. It's a real RF preamplifier, very critical to tune and prone to RF oscillations. The lauout it's very critical and in PCB design we should take precautions (low capacity layout, accurate ground design etc.). This is the maximun i can explain with my poor english language. It's a very unusual design and i ask for other technical advice; maybe Mr J. Curl would say a word about this? ciao
AGI preamplifier is a preamplifier with a bandpass of more than 100MHz and with an elevated Slew Rate (nearly 200 V/Usec). This is due to project able to process RF signals. It's a real RF preamplifier, very critical to tune and prone to RF oscillations. The lauout it's very critical and in PCB design we should take precautions (low capacity layout, accurate ground design etc.). This is the maximun i can explain with my poor english language. It's a very unusual design and i ask for other technical advice; maybe Mr J. Curl would say a word about this? ciao
I'm looking this schema and every time i find genius spread everywhere! You have Q2;Q3;Q4 and Q5 forming an ultrawideband amplifier (RF coming from input via C6 and C7).Q1 acting like a shifter and two feedback network; ac feedback (including C12 - 50uF and related distorsions) via an equalisation network (seem an anti RIAA) and a DC feedback via R13 - R14. Please note inductance with R in parallel for lowering Q factor. This beauty is not "usual" preamplifier! It's a masterpiece of engeneering; very "american techno" like Harley or Winchester rifles!
This is a contribute i've found on net.Enjoy!!!
...As to answer the original question, my contribution to this thread would be Audio General, Incorporated or as others may know them "AGI". They only produced one product over a 14 year span and it was their 511 / 511A preamp. Many of the folks that were into audio way back when will remember this preamp as it was written about in most every "underground" audio mag along with glossies like Audio during that time frame. If i remember correctly, J. Peter Moncrieff stated "this is the only product made that has ever challenged the residual noise floor of our test equipment".
I asked David Spiegel why he never came out with matching amplifiers. His response was that building / marketing amplifiers were FAR more costly, especially if done right. He did not have the capital to do that and didn't know how well they would sell if he did market such a product. Given David's very straight-forward designs, no-hype marketing and penchant for using the best parts available at the time, i'm sure that it would have been a great product. None the less, many "great products" were swallowed up by lesser products that had more financial and marketing support due to offering a bevy of "bells and whistles" during those years. After all, people were still using equalizers and tone controls back then. For the record, the 511 didn't come with tone controls, but did offer a specific loop for signal processing should one feel the need.
I can see why David was leery about going forward with an investment of that nature, but i really wish he would have. The little bit that i did read about the prototypes had them slewing at something like 1000 V/uS. Bare in mind that this was in 1978 -79 or so. Then again, the phono section of the 511 slewed at 370 V/uS and had a rise time of .01 uS and this was in 1974 !!! Not only were the circuits phenomenally fast and broad-band for that time period, David incorporated Zobel Networks to minimize transformer ringing / AC noise, star grounding to minimize ground loops, 24 Karat Gold plated Berryllium copper contacts for all signal connectons, Allen Bradley Mil-Spec pots, poly and tantalum caps, metal film resistors, coined silver contacts in the switching, etc... As one can tell, the quality of signal and components used were of utmost importance to David.
To top it off, David gave us all of this for an MSRP of $499. Other competing preamps that used far lower grade circuitry and parts were selling for $800 - $1200 back in the mid to late 1970's. In effect, the AGI and David Spiegel never gained the respect that they should have due to UNDER-pricing his product. As everyone knows, "real" high end audio products have to be phenomenally expensive to be good. If it isn't expensive, it can't be that good. After all, how could it be that a "commoner" could afford the best there is ??? Audio snobbery was alive and well LONG before many of today's "super manufacturers" ever thought about releasing a product. Sean
PS... David Spiegel was responsible for the first blind listening tests performed under controlled conditions. He "invented" the switchbox used for many of these tests. For the record, the only reviewer that i know of that passed this test in front of Spiegel was Edith Lumley. The reason that i know that Lumley was able to do so in front of Spiegel is because David himself told me so. Most other "golden eared" reviewers either didn't show up for the "challenge" that he issued to them or failed miserably once they did show up.
Moncrieff could supposedly identify whether this switchbox ( basically a high grade relay with the associated cabling and connecting jacks in a box ) was in the signal path or not with 100% accuracy. One would not even have to switch components but just placing the switchbox in series with the signal was audible to Moncrieff. Bare in mind that Moncrieff supposedly passed these tests with witnesses, but not in front of Spiegel. Trying to make the switchbox more transparent, Moncrieff and John Curl later came up with a design revision using a higher grade relay, but the initial design and concept was put forth by Spiegel.
As such, Spiegel may be the "Grandfather" of high speed, wide-bandwidth circuitry AND "controlled listening tests" aka "DBT" ( double blind testing)
...As to answer the original question, my contribution to this thread would be Audio General, Incorporated or as others may know them "AGI". They only produced one product over a 14 year span and it was their 511 / 511A preamp. Many of the folks that were into audio way back when will remember this preamp as it was written about in most every "underground" audio mag along with glossies like Audio during that time frame. If i remember correctly, J. Peter Moncrieff stated "this is the only product made that has ever challenged the residual noise floor of our test equipment".
I asked David Spiegel why he never came out with matching amplifiers. His response was that building / marketing amplifiers were FAR more costly, especially if done right. He did not have the capital to do that and didn't know how well they would sell if he did market such a product. Given David's very straight-forward designs, no-hype marketing and penchant for using the best parts available at the time, i'm sure that it would have been a great product. None the less, many "great products" were swallowed up by lesser products that had more financial and marketing support due to offering a bevy of "bells and whistles" during those years. After all, people were still using equalizers and tone controls back then. For the record, the 511 didn't come with tone controls, but did offer a specific loop for signal processing should one feel the need.
I can see why David was leery about going forward with an investment of that nature, but i really wish he would have. The little bit that i did read about the prototypes had them slewing at something like 1000 V/uS. Bare in mind that this was in 1978 -79 or so. Then again, the phono section of the 511 slewed at 370 V/uS and had a rise time of .01 uS and this was in 1974 !!! Not only were the circuits phenomenally fast and broad-band for that time period, David incorporated Zobel Networks to minimize transformer ringing / AC noise, star grounding to minimize ground loops, 24 Karat Gold plated Berryllium copper contacts for all signal connectons, Allen Bradley Mil-Spec pots, poly and tantalum caps, metal film resistors, coined silver contacts in the switching, etc... As one can tell, the quality of signal and components used were of utmost importance to David.
To top it off, David gave us all of this for an MSRP of $499. Other competing preamps that used far lower grade circuitry and parts were selling for $800 - $1200 back in the mid to late 1970's. In effect, the AGI and David Spiegel never gained the respect that they should have due to UNDER-pricing his product. As everyone knows, "real" high end audio products have to be phenomenally expensive to be good. If it isn't expensive, it can't be that good. After all, how could it be that a "commoner" could afford the best there is ??? Audio snobbery was alive and well LONG before many of today's "super manufacturers" ever thought about releasing a product. Sean
PS... David Spiegel was responsible for the first blind listening tests performed under controlled conditions. He "invented" the switchbox used for many of these tests. For the record, the only reviewer that i know of that passed this test in front of Spiegel was Edith Lumley. The reason that i know that Lumley was able to do so in front of Spiegel is because David himself told me so. Most other "golden eared" reviewers either didn't show up for the "challenge" that he issued to them or failed miserably once they did show up.
Moncrieff could supposedly identify whether this switchbox ( basically a high grade relay with the associated cabling and connecting jacks in a box ) was in the signal path or not with 100% accuracy. One would not even have to switch components but just placing the switchbox in series with the signal was audible to Moncrieff. Bare in mind that Moncrieff supposedly passed these tests with witnesses, but not in front of Spiegel. Trying to make the switchbox more transparent, Moncrieff and John Curl later came up with a design revision using a higher grade relay, but the initial design and concept was put forth by Spiegel.
As such, Spiegel may be the "Grandfather" of high speed, wide-bandwidth circuitry AND "controlled listening tests" aka "DBT" ( double blind testing)
AGI 511
I have schematics and very good photos of the 511. There are no uA709 opamps in this unit. Output stage utilizes a LF357 opamp which includes the output coupling cap in the feedback circuit. Phono stage uses a uA733 as the input stage with a output stage constructed with discrete transistors. Just as a historical note the Hegeman Hapi preamp used the same opamp in its phono and line output stages. Infinity used the same device in its Servo Statik 1 active crossover servo feedback bass amplifier.
I have schematics and very good photos of the 511. There are no uA709 opamps in this unit. Output stage utilizes a LF357 opamp which includes the output coupling cap in the feedback circuit. Phono stage uses a uA733 as the input stage with a output stage constructed with discrete transistors. Just as a historical note the Hegeman Hapi preamp used the same opamp in its phono and line output stages. Infinity used the same device in its Servo Statik 1 active crossover servo feedback bass amplifier.
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