Does anyone know much about AGI preamps?

I have had an AGI 511 pre-amp for some time and I love its supreme build quality and transparent nature. I just can't find any info on the darned thing. I know the company went out of business in the 80's, but there is not a shred of evidence of their existence on the web. I can't find any specs on the thing. I have only seen two others go for sale ever; they seem pretty rare. If anyone knows where I can get some info, or knows anything about the preamp, it would be appreciated. Thanks.
What would you like to know ? While not an expert on the unit, I own a half dozen of these units in various forms. I also have quite a bit of the factory literature and have spoken to the designer / builder on several occasions. My Brother also runs a 511A in his main system and so does my Father.

Part of the reason that you don't see a lot of these units for sale is that quite a few people don't want to part with them. Even if they are not using them anymore, they know that you can't really replace them without spending quite a bit of money. If they did some mods to them, they would still be using them as their main preamps. Kind of amazing that a piece of SS gear that was designed in 1974 can still hold it's own, isn't it ??? Sean
Well, just the basic facts, I think. I have seen one or two web pages where people mentioned modifications to it. What would the improvements be, exactly? I was mainly wondering what the basic specs were. Like S/N ratio (it almost seems to me to be passive, so would this even apply?), the stereo channel separation (dB), distortion (%), and also the relative quality of the pots/wiring/electrical components. I know nothing about this unit and it intrigues me because it sounds so good and appears to be built so well. It would be cool to know what flavors of equipment with which it performs best. I have it hooked up to a Myryad CD player and a McIntosh MC-2205 and it sounds preeeetty good. Thanks very much, Jason.
Hello Jason & Sean
The AGI 511 and AGI 511A was surely a great preamp from the hands of a man named Dave Spiegel. I use to truly admire the dedication this guy had to produce the best sound possible. I live about 10 miles from the old production facility in Willow Grove, PA. This thing had the best circuit board that a 1976 product could have. It was built right with one goal in mind; Flawless sound. While the stock unit was smooth sounding for a SS preamp and reasonably free of any distortion, the problem was in the 3D illusion department. Now, I am sure, that the basic sound of this unit was good enough to, when modified,with better parts, overcome the slight ambience reduction. Can you imagine though, a Spectral type of build quality for $400.00!!! Thats all this puppy cost. The chassis was top grade stainless steel. This was the time when being an audiophile was really great. Alas I dont know what became of Dave, but the guy was an engineer that was mighty capable. Wish he would reappear on the scene.....Frank
Frank, I agree that it was a WAY overdesigned / underpriced unit in its' day. I've talked to David a few times in the last two years or so. I have his current phone / address and he's probably not too far from you. He currently designs and markets safety / monitoring equipment for Nuclear Power plants. From what he told me, he basically has the market cornered in several surrounding States and is working his way towards me in Illinois. He is still quite interested in audio and repairs his units. From what i gather, i think that he still dabbles in audio on a personal level as he mentioned doing some swapping for Madrigal gear, etc... I just wish (REALLY, REALLY wish) that he would have put an amp into production back then.

As to the lack of dimensionality, i hear where you're coming from but also tend to disagree. I've found that the unit SEEMS to be somewhat "2D" but not really. Most of the time, this is a limitation of the amplifier being used. The preamp will give you whatever is there. On good recordings, there is a definite sense of ambience, depth and spaciousness. On a specific Loreena McKennit disc, it is quite astounding when using a good DAC with this pre and a "reasonable" power amp. Quite honestly though, i have very FEW recordings that offer this type of depth, space or ambience. When it is present though, this preamp lets it through in spades.

I have compared these preamps to several others WAY above their price point and they have always held their own, actually stomping quite a few units along the way. So long as they are properly matched with amps, cables, etc... they truly are wonderful. As a case in point, I temporarily replaced my Fathers tube preamp ( while i repaired his ) with one of my AGI's. When i told my Mother that their preamp was ready to go and i would be bringing it back soon, she told me "keep it. That one sounds like junk compared to this one." My Dad simply said that the AGI was much cleaner, clearer and offered far better detail with better bass resolution. He never mentioned any loss of spacial characteristics or ambience during this time even though the system had been dialed in with the other preamp in mind. He later prompted me to find him an AGI to replace his "highly reviewed" tubed preamp once i brought his back. Once he was able to do direct comparisons, the differences were even more obvious. Keep in mind that his preamp was not a "bargain basement" model, as it used an external power supply, wonder caps, wonder solder, teflon wiring, was loaded with gain matched tubes from Roger Mojeski, etc...

In a direct comparison to my Marsh in three different systems, the Marsh sounds slower, somewhat murky, lacks pace, the bass is less distinct and the treble is slightly splashier. While this description makes the Marsh sound like a piece of junk, it is not by any means. It is just "different".

In terms of "mods" or "upgrades", most of the pots on these units are about shot or going the way of the wind. Channel balance and volume tracking on these controls are no longer up to spec even though they were pretty much the best that you could buy at the time. These can be replaced with other current design potentiometers. I'm even thinking of putting in a remote control volume in one unit.

The BIGGEST improvement that one can make to these units is to remove the entire sub-board that holds all of the RCA's to the back panel. You can chassis mount much higher grade RCA's and hard wire them to the board using higher quality wire. You have then removed the standard RCA's ( which cost WAY less than $0.20 apiece wholesale ), the circuit traces on the rear board, the ribbon cable that consisted of low grade tinned wire and two molded plastic connectors. The slight amount of brightness or hardness that these units might tend to exhibit is removed and you end up with a much smoother, fuller and more dimensional product that has greatly improved midrange lucidity. Bass has more impact and offers better extension also. You retain all of the clarity, speed and detail and simply add more "warmth" and "musicality" to what was already one of the most revealing preamps ever made.

You can also do some simple upgrades to the power supply rectifiers, increase filter capacitance, etc... This too can help quite a bit, as most of the caps are beginning to dry out or have lost a large percentage of their rated value. The power cord was also pretty cheap, as it even said something to the effect of being manufactured for a toaster : ) David put the money into the parts that he thought were the most important. Other than the power cord, RCA's and internal ribbon cable ( which were all industry standard back then ), i can think of nothing that he skimped on in terms of build quality.

Jason, can you direct me to the websites that make mention of modding these units ? I'd like to compare notes with others that have done this and see what we can come up with. Sean
Wow, I bought this unit on a strong recommendation for $220, and now after reading your descriptions I feel like I've gotten away scott-free with the Great Train Robbery. Now I know the explanation for the sound that I hear from it. My hat goes off to Dave. Good job.

These are the web sites that I found that only briefly mention the AGI 511a and modification, but there is no detailed explanation to it.

Thanks for the tips about the modifications. I know a local electronics wizard here in Austin that I will ask to look into these changes. As you mentioned interconnects, I am using some extremely dull-sounding Acoustic research cables and have been researching replacements. I initially considered Nordost Blue Heavens, but then I found a DIY recipe on the web for teflon-coated silver wire interconnects, and I'm going to give them a shot first. The URL is below. Check it out. It's a much more coherent plan than most others I've seen on the internet.

Thanks very much, guys. Happy Listening to you.
Jay, i've seen Bruce's reviews before and emailed him quite a while ago. From what i can gather, his AGI is NOT highly modified. It simply has some common upgrades done to it. If i remember correctly, i think that he had all of the RCA's replaced with "audiophile approved" pieces and installed a new power cord. As i mentioned, getting rid of the ribbon cable and RCA sub-board is of PRIME importance if you really want to hear the unit sing. This is NOT easy though and is quite time consuming in terms of documenting where each wire goes, etc... I've made my own charts and even i get confused by them sometimes !!! : )

As to the Acoustic Research cables, i had a friend ( Hi Lou !!! ) send me some to burn in on my Mobie. He found them to be unlistenable so i volunteered to see if burning them would help at all. I did listen to them when i first got them and agree with him that they are not the best. They are still on the burner as we speak.

While i have not used the cables that you listed, i am quite familiar with Chris' work and designs. He's a great guy and goes way out of his way to help people out. Like most of us without "trust funds", he strives to do the most with the least.

In stock form, the AGI works quite well with Jon Risch's Belden 89248 / 89259 twisted pair design. These cables are excellent for the money and sound very smooth, transparent and detailed while still retaining good body and warmth to them. Like anything else though, whether you like these is up to system synergy and personal taste. I use a combination of these and a couple different types of Magnan ( slightly leaner sounding with excellent high frequency detail ) cables in my computer room system. Sean
Jay, i also forgot to ask if you are taking advantage of the phono section in this preamp ??? If not, i would HIGHLY suggest investing in a GOOD yet basic TT and giving it a try. You might be AMAZED at how good vinyl sounds via a well set-up system that doesn't have to cost a fortune. Sean
Sean, yes, I have used two of my TT's with the AGI so far. A Technics SL-D2 and a Pioneer PL series (either a 550, 560, or 570, I can't exactly remember which I've got back there rtight now). I do very much like the way vinyl sounds on it, but I have spent more time putting together a DIY record vacuum than listening to vinyl lately. After I've cleaned a few records I'll give it a critical listen. Are there some better TT's you could recommend? I love auditioning and looking at new stuff. I've considered looking into the Thorens TD-124. Someone here in Austin who owns a hi-fi shop talks about them like they have all been touched by King Midas. Thanks very much, Jason.
Without getting into more expensive TT's, the one that comes the most highly recommended for the cash seems to be the Well Tempered system. Since i don't have first hand experience with this piece, i'm simply repeating what i've been told by people that i trust ( hardcore vinylphiles ). Other than that, you could probably step into a reasonably priced Thorens, AR, Rega for not that much and notice an appreciable difference. Just make sure that the arm is properly set up and the cartridge is a good choice for the design / mass of the arm.

Be careful here, as i've had "reputable shops" sell and install cartridges that WERE NOT compatible with the arm that was on the table. I simply followed their suggestion and left it up to them to install it. Prior to use, i read the cartridge manufacturers recommendations for proper set-up. What i found was that the cartridge that they had recommended and installed would never work properly in that arm. Needless to say, i had to return it. They were pissed to say the least, but they took it back with a $50 "labor fee". If you think that they were "pissed", they should have tried to see my point of view. After all, it was THEIR fault. They made the suggestion, they sold me the wrong component, they installed it. All i did was listen to the "self appointed" expert and "get taken" while forking over the cash. Never again...

Do you know what phono stage you have in your AGI ??? David made three different versions with various amounts of gain. If you can look inside, i can walk you through telling which one you have. You really do need to know this in order to select a cartridge with the proper output level.

You might also want to see if the previous owner had added resistors / capacitors in order to fine tune the loading characteristics for a specific cartridge. If so, you can take them out. It might help the combo that you currently have to sound even better. Sean
Sure, I'm game to to try looking at the phono stage. If you'd like to email me, it's