Au contraire, of all the parts I replaced on 'this' vintage iron chest of a boat anchor(Audio Innovations 500 - Serial 50532), the power supply caps were in mint condition and I shall repurpose them or sell them or trade them. I had to make room for a choke to replace that RS Components 47 ohm resistor or I would never have touched these caps. Keeping tradition I replaced them with Kemet ALAs. Kemet bought BHC after all...
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My thoughts on the Audio Innovations Series 500 - Serial number 50532
The designers and builders of this vacuum tube-integrated amplifier were at war with each other. After working on this thing on and off for a year I got to know it very well. 'They' spent too much budget on some things and not enough money in other areas. Things fit perfectly together with German precision and some of it was pushed into the enclosure with a boot from a person's foot. In summary, the AI Series 500 is an oddity, an interesting piece and a special collectible contribution to the component world of audio.
The circuits inside are tried, true and tested. Good old-fashioned vacuum tube audio with a bit of silicon. The build quality was/is excellent but it is too much for the iron chassis. The iron box is outstanding yet it is wired like a clam and you must get it open like shucking an oyster. It is profoundly ridiculous but really neat. Everything I touched on it felt like a paradox as though production costs were fighting design goals. I know that can be true with everything manufactured but I truly got a sense of that Ying & Yang in the AI 500. Listen, the cat is out of the bag when brochures and press material have wonky grammar and spelling mistakes coming out of the UK no less. Outlandish. Did the Queen know? Good Lord! Ha
The silver-traced circuit boards are a wonder to behold. Apply your solder iron and watch the trails vaporize in front of your eyes. I have never seen anything like it in my life. Strike one or two for me and it was a mighty blow. I got over it with my own fashionable PCBs.
This 50532 serial number was released to 120 volt North American mains though the power supply transformer was adapted to 115 volts. Add a 2% line spike and the issue becomes compounded into an actual problem that leads to the eventual demise. You see the B+ will rage too high under such conditions unregulated. One of the main voltage divider resistors in it's power supply was 200 ohms shy of what it was supposed to be. There was 1000 ohm in place where there should have been a 1200 ohm and it was factory installed in the UK. It was not a mod. A production shortage work-around or assembly error?
The cathode resistor scheme was modded, perhaps to augment the hot operating conditions the North American reseller encountered? Or it was a sound mod enhancement? Whatever it was, it was wrong and the schematics are pretty accurate and should be followed. I ended up with a 28.35 volt drop on the cathode resistors, just 0.35 higher than spec. Good times. I am pleased with that.
I pulled the main resistor from the power supply and added a Hammond choke 157R. New power supply caps. New silicon bridge.
The valves driving the EL34 outputs had a weird factory mod/compromise where 22k 2watt resistors were replaced with 1 watt 47k's in parallel. They are the hard-working plate resistors on those valves. Neither solution would be ideal in my estimates so ditching the circuit board I built a new one with Riedon PF2470 resistors and I fitted them with M.2 Hard Drive heat sinks that fit perfectly and cooled those devils down. They are also 22K and not 47k divided by 2. I guess they can handle 5 to 10 watts no problem with the low profile heats sinks I used. There is clearly a minimum of 4 watts of pure heat dissipation going on there. That has got to be the number one problem with the AI 500 in North America for serial numbers close 50532, 3 PCB build with 4, 8, 16 ohm speaker taps. The circuit board was scorched from those resistors even though Audio Innovations knew this and added ceramic stand-offs. Hot, hot, hot.
I'd love to tear the entire amp apart and install a new phono circuit board and a new pre-drive circuit board. That would be so cool and to change some of those parts around to today's fancy caps & resistors. That would be nice and fun but too much work. My heart is not there.
This integrated valve amp sounded strange when it landed in my hands. Not the case anymore. It measures up well on the Quant Asylum QA401 even though I do not have the best valves running on it. Looks like it is spec or a tad better.
While listening in a two-speaker boutique situation, the 25 watts of Class A is a tremendous amount of power. Far more than the average speaker would ever require for critical listening or typical enjoyment. Yet the 500 has enough reserve to turn up with party guests and loud shenanigans.
It sounds wonderful. I wish I had an unlimited budget to buy thermionic valves for this unit. I would love to hear it with top-notch valves. The Tung-Sol EL34s I have coupled to those output transformers produce what seems to be unlimited bass and punch. It kind of reminds me of the JLH 1969 on steroids. It has a big sound and fills the space all around you. Yet the AI 500 has the detail to tickle your ears with the finer elements in the sound stage. This integrated amplifier does not discriminate on source material. It drives furniture moving bass through the floor with heavy electronic EDM and can handle the nasty exercises from Richard D. James no problems. AC/DC and Rolling stones full blast all day no problem. Jazz horns and brushes on snares are fantastic. The vocal abilities of these output transformers have a live performance talent you won't find in every tube amp, no sir. The rumors are true, the metal in this box is a hat trick. Quatro stagioni if you include the iron box!
The designers and builders of this vacuum tube-integrated amplifier were at war with each other. After working on this thing on and off for a year I got to know it very well. 'They' spent too much budget on some things and not enough money in other areas. Things fit perfectly together with German precision and some of it was pushed into the enclosure with a boot from a person's foot. In summary, the AI Series 500 is an oddity, an interesting piece and a special collectible contribution to the component world of audio.
The circuits inside are tried, true and tested. Good old-fashioned vacuum tube audio with a bit of silicon. The build quality was/is excellent but it is too much for the iron chassis. The iron box is outstanding yet it is wired like a clam and you must get it open like shucking an oyster. It is profoundly ridiculous but really neat. Everything I touched on it felt like a paradox as though production costs were fighting design goals. I know that can be true with everything manufactured but I truly got a sense of that Ying & Yang in the AI 500. Listen, the cat is out of the bag when brochures and press material have wonky grammar and spelling mistakes coming out of the UK no less. Outlandish. Did the Queen know? Good Lord! Ha
The silver-traced circuit boards are a wonder to behold. Apply your solder iron and watch the trails vaporize in front of your eyes. I have never seen anything like it in my life. Strike one or two for me and it was a mighty blow. I got over it with my own fashionable PCBs.
This 50532 serial number was released to 120 volt North American mains though the power supply transformer was adapted to 115 volts. Add a 2% line spike and the issue becomes compounded into an actual problem that leads to the eventual demise. You see the B+ will rage too high under such conditions unregulated. One of the main voltage divider resistors in it's power supply was 200 ohms shy of what it was supposed to be. There was 1000 ohm in place where there should have been a 1200 ohm and it was factory installed in the UK. It was not a mod. A production shortage work-around or assembly error?
The cathode resistor scheme was modded, perhaps to augment the hot operating conditions the North American reseller encountered? Or it was a sound mod enhancement? Whatever it was, it was wrong and the schematics are pretty accurate and should be followed. I ended up with a 28.35 volt drop on the cathode resistors, just 0.35 higher than spec. Good times. I am pleased with that.
I pulled the main resistor from the power supply and added a Hammond choke 157R. New power supply caps. New silicon bridge.
The valves driving the EL34 outputs had a weird factory mod/compromise where 22k 2watt resistors were replaced with 1 watt 47k's in parallel. They are the hard-working plate resistors on those valves. Neither solution would be ideal in my estimates so ditching the circuit board I built a new one with Riedon PF2470 resistors and I fitted them with M.2 Hard Drive heat sinks that fit perfectly and cooled those devils down. They are also 22K and not 47k divided by 2. I guess they can handle 5 to 10 watts no problem with the low profile heats sinks I used. There is clearly a minimum of 4 watts of pure heat dissipation going on there. That has got to be the number one problem with the AI 500 in North America for serial numbers close 50532, 3 PCB build with 4, 8, 16 ohm speaker taps. The circuit board was scorched from those resistors even though Audio Innovations knew this and added ceramic stand-offs. Hot, hot, hot.
I'd love to tear the entire amp apart and install a new phono circuit board and a new pre-drive circuit board. That would be so cool and to change some of those parts around to today's fancy caps & resistors. That would be nice and fun but too much work. My heart is not there.
This integrated valve amp sounded strange when it landed in my hands. Not the case anymore. It measures up well on the Quant Asylum QA401 even though I do not have the best valves running on it. Looks like it is spec or a tad better.
While listening in a two-speaker boutique situation, the 25 watts of Class A is a tremendous amount of power. Far more than the average speaker would ever require for critical listening or typical enjoyment. Yet the 500 has enough reserve to turn up with party guests and loud shenanigans.
It sounds wonderful. I wish I had an unlimited budget to buy thermionic valves for this unit. I would love to hear it with top-notch valves. The Tung-Sol EL34s I have coupled to those output transformers produce what seems to be unlimited bass and punch. It kind of reminds me of the JLH 1969 on steroids. It has a big sound and fills the space all around you. Yet the AI 500 has the detail to tickle your ears with the finer elements in the sound stage. This integrated amplifier does not discriminate on source material. It drives furniture moving bass through the floor with heavy electronic EDM and can handle the nasty exercises from Richard D. James no problems. AC/DC and Rolling stones full blast all day no problem. Jazz horns and brushes on snares are fantastic. The vocal abilities of these output transformers have a live performance talent you won't find in every tube amp, no sir. The rumors are true, the metal in this box is a hat trick. Quatro stagioni if you include the iron box!
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I added mains side pie-like-filter resistors to the primary side of the power supply transformer. Something you could only get away with on a small to medium valve project. Low ohmic value and high-watt resistors kept it friendly, only dissipating a few watts of pure heat. They ended up getting their own heat sink to keep them far under spec. This augmentation was a massive correction to the B+ and heaters on the other side of that iron. The output transformers do all the heavy lifting in a setup like this, so I was fortunate that way. You could drop that thing entirely and get a similar power transformer in the chassis. 100% doable at a cost but doable.
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