Wanted...Help with schematics/service manual or bias current setting.
Despite hours of searching I can find nothing on the web about the Audio Innovations Alto, there's only the odd passing comment even on this site.
I bought one not working and on inspection found previous repair bodging that had damaged a number of pcb tracks and very bad soldering where new transistors had been installed + some wrong equivalents. Anyway cut a long story short - fixed all that re-wiring tracks as necessary, replaced all the caps etc and got it running and sounding OK.
Problem is I can find no information about setting the bias and normal procedures for what I presume is a fairly standard class B design don't seem to be working. There are two trimmers per channel and I would normally expect one to control DC offset and one bias current. The amp runs ok and doesn't get too warm if I leave them as found but that gives output offsets of 200 and 500mv ish. Adjusting the trimmers will get that down to near zero but then the output transistors get very hot, very quickly and Collector current is climbing indicating runaway.
Only unusual design feature I've noticed is 3 (i think) signal diodes arranged in a sandwich between pcb and output transistor heatsink. N.B. Each transistor has separate board mounted sink with bias transistors attached. What's that about?
Can anyone help, does anyone have one of these amps they can take some measurements off. There may yet be something else wrong I haven't located yet.
Thanks.
Despite hours of searching I can find nothing on the web about the Audio Innovations Alto, there's only the odd passing comment even on this site.
I bought one not working and on inspection found previous repair bodging that had damaged a number of pcb tracks and very bad soldering where new transistors had been installed + some wrong equivalents. Anyway cut a long story short - fixed all that re-wiring tracks as necessary, replaced all the caps etc and got it running and sounding OK.
Problem is I can find no information about setting the bias and normal procedures for what I presume is a fairly standard class B design don't seem to be working. There are two trimmers per channel and I would normally expect one to control DC offset and one bias current. The amp runs ok and doesn't get too warm if I leave them as found but that gives output offsets of 200 and 500mv ish. Adjusting the trimmers will get that down to near zero but then the output transistors get very hot, very quickly and Collector current is climbing indicating runaway.
Only unusual design feature I've noticed is 3 (i think) signal diodes arranged in a sandwich between pcb and output transistor heatsink. N.B. Each transistor has separate board mounted sink with bias transistors attached. What's that about?
Can anyone help, does anyone have one of these amps they can take some measurements off. There may yet be something else wrong I haven't located yet.
Thanks.
It is now but it wasn't when the first series of Alto amplifiers (grey ones) were manufactured. The silver version is a re-hashed version under the Audio Partnership regime and is of much poorer quality than the originals, the matching cd/tuner is a right bag of poo. I have repaired a few of these but have never managed to find a schematic unfortunately
Hi,
I also have one of these nice looking but very unreliable amps (now on my 2nd) and it has died on me. Does anyone know of somewhere I can get it fixed please, or at least someone to look to see if it can be/is worth fixing? I've been wondering whether just to give up and get something else but it seems a shame to just dump it if it's something simple that's wrong.
Thanks all.
I also have one of these nice looking but very unreliable amps (now on my 2nd) and it has died on me. Does anyone know of somewhere I can get it fixed please, or at least someone to look to see if it can be/is worth fixing? I've been wondering whether just to give up and get something else but it seems a shame to just dump it if it's something simple that's wrong.
Thanks all.
Don't do it - send it to me!
On that front, the only information I have been able to find is a gramaphone review of July 1994 which states that it is a quasicomplimentary AB design with a DC blocking capacitor.
Oh, I would love to get some dead ones to play with!
THIS is actually a small nice amplifier .. normally a few milliamps will do ....something like 50 ma only problem is that you will need a scope to tune i properly ...if memory serves properly one trimmer is for symmetry while he other is for the bias
still for an amp like that i would change the capacitors to anything bigger may fit in the case ...4700 for that total power supply is barely enough and inside a snap 10.000 mfd could be easily placed while in the output 4700 instead of 2.200 or even more
beyond the damage one way ore another some of these amps had soldering issues and you need to be careful
since also heatsink is small be careful with the bias ...when finished you will see that beyond low power the little crap actually sounds very decent
still for an amp like that i would change the capacitors to anything bigger may fit in the case ...4700 for that total power supply is barely enough and inside a snap 10.000 mfd could be easily placed while in the output 4700 instead of 2.200 or even more
beyond the damage one way ore another some of these amps had soldering issues and you need to be careful
since also heatsink is small be careful with the bias ...when finished you will see that beyond low power the little crap actually sounds very decent
Hi, good stuff here with the diagram!
May someone can give me a hint with my problem. I do have Volt Meter, can solder, but transistor/components knowledge is low/rusty...
I have an Alto amplifier with main board K4043/6 and since sunday an issue...
During normal operation all of a sudden both channels, no sound anymore. powerled still on.
Opened it up, no smell, no visible blown parts, no blown fuses.
But also not the output delay click!!..
Going through the schematics, I do have 60V on the fuses FS1 and FS2.
I do measure 30V at R21-R22-R25-R26. (Alto4picture).
Then the part that confuses me, at both W11 and W18 (or W8 and W5 at Alto5picture) I do not measure anything, that is after the 2 capacitors C8 and C9. Is there supposed to be a DC voltage there (so close to the speaker connections)? Also no DC voltage at R3 - R4.
It all leads to the little delay switch RL1a-RL1b an Omron G2R-2 24VDC that does not do anything... or would the capacitors C8 and C9 still be suspicious? (both both at the same time is weird).
Any experrience or suggestions would be welcome! also on some quick other check points ;-)
I really love the sound of this amplifier, got it connected to 2 JMlab Electra 905. A match from heaven ;-)
)ps, although mine is chrome, it is the same as the black one, not tha later am1 version)
Cheers from holland
May someone can give me a hint with my problem. I do have Volt Meter, can solder, but transistor/components knowledge is low/rusty...
I have an Alto amplifier with main board K4043/6 and since sunday an issue...
During normal operation all of a sudden both channels, no sound anymore. powerled still on.
Opened it up, no smell, no visible blown parts, no blown fuses.
But also not the output delay click!!..
Going through the schematics, I do have 60V on the fuses FS1 and FS2.
I do measure 30V at R21-R22-R25-R26. (Alto4picture).
Then the part that confuses me, at both W11 and W18 (or W8 and W5 at Alto5picture) I do not measure anything, that is after the 2 capacitors C8 and C9. Is there supposed to be a DC voltage there (so close to the speaker connections)? Also no DC voltage at R3 - R4.
It all leads to the little delay switch RL1a-RL1b an Omron G2R-2 24VDC that does not do anything... or would the capacitors C8 and C9 still be suspicious? (both both at the same time is weird).
Any experrience or suggestions would be welcome! also on some quick other check points ;-)
I really love the sound of this amplifier, got it connected to 2 JMlab Electra 905. A match from heaven ;-)
)ps, although mine is chrome, it is the same as the black one, not tha later am1 version)
Cheers from holland
Hi, in the mean time I found this topic http://www.diyaudio.com/forums/solid-state/218715-audio-innovations-alto-amp-noise-one-channel.html
Where Sakis tells allready that ---There has been reports that output relays fail quite often
So that stands a big change, it is now 15 years old. But I do not turn it off and on a lot, maybe 30 times a year max. It's radio sound all day, tv sound all evening and inbetween some cd's ;-)
So it would be a good start just replacing this component?
The othe issue I also have: ---selector switch faulty or dirty
Did at one time disassambles and cleaned, but can not find a replacement. 6 position slide selector swich...
Where Sakis tells allready that ---There has been reports that output relays fail quite often
So that stands a big change, it is now 15 years old. But I do not turn it off and on a lot, maybe 30 times a year max. It's radio sound all day, tv sound all evening and inbetween some cd's ;-)
So it would be a good start just replacing this component?
The othe issue I also have: ---selector switch faulty or dirty
Did at one time disassambles and cleaned, but can not find a replacement. 6 position slide selector swich...
Hi
A little info that may help Alto owners.. I found an Alto and matching cd/ tuner at a local garage sale. it is the chrome version . I assume it is the later version . After removing the cover to do an inspection before powering up i noticed This amp to be totally diffrent to the one that is spoken about in this thread.. It has a sub out connection and the amplifier is a complimentary dual rail design with no output capacitor . it also uses 15000uF per rail. I was disapointed at first as i really wanted to have a listen to a single ended version. The sound of this little wonder as far as my ears can tell matches the original write ups apart from the bass is not lacking in this version.. Will remove cover and take some piccys if anyone is intrested..
regards Mark
Ps this version is also remote control and uses logic to switch inputs and motorised pot for volume control.Did find some info on the web stating it was simler to denon a500 topology but that is a quasi complimentary amplifier
A little info that may help Alto owners.. I found an Alto and matching cd/ tuner at a local garage sale. it is the chrome version . I assume it is the later version . After removing the cover to do an inspection before powering up i noticed This amp to be totally diffrent to the one that is spoken about in this thread.. It has a sub out connection and the amplifier is a complimentary dual rail design with no output capacitor . it also uses 15000uF per rail. I was disapointed at first as i really wanted to have a listen to a single ended version. The sound of this little wonder as far as my ears can tell matches the original write ups apart from the bass is not lacking in this version.. Will remove cover and take some piccys if anyone is intrested..
regards Mark
Ps this version is also remote control and uses logic to switch inputs and motorised pot for volume control.Did find some info on the web stating it was simler to denon a500 topology but that is a quasi complimentary amplifier
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That would be the 2nd generation Detector AM1 and CT1
Text copied from AVforums: Best looking separates ever | AVForums.com - UK Online This never fails to amuse me- AP stopped making Alto's because they were as popular as a fart in a space suit. Four years later, I still get emails about them
Basically they come in two different types
Original- Built by the old Audio Innovations. These are (I think) only in black and run a Class A amp so you can use it as a hotplate as well. (Edit, no, these where made in chrome as well) The CD might have quite a bit in common with the old Arcam Alpha 7 (same mech certainly)- the prototype was an Alpha 7 in an Alto Box
Second batch- Built by us in the Chrome. The key difference is that the CD section had a tuner module (not a shabby one either- its the one from the Creek T43/Cambridge T500) and could be driven by a single remote as the two units were connected with a "canbus" (RJ45) lead with the socket on the back (the old ones don't have this). These units have a fair amount in common with the Cambridge Audio D500/A500 but the heat sink was squashed to fit in and this meant that the amp was more fragile than the standard A500. The display on the CT1 CD player was also frighteningly complicated as it was a sandwich with the CD section on one layer and the tuner on the other. These fail. Lots.
If you really want them, the bay is the best place but shop carefully- remotes and the original short RJ45 leads are now extinct. The stand is unbelievably rare as it never sold and only one batch was made.
HTH
Text copied from AVforums: Best looking separates ever | AVForums.com - UK Online This never fails to amuse me- AP stopped making Alto's because they were as popular as a fart in a space suit. Four years later, I still get emails about them
An externally hosted image should be here but it was not working when we last tested it.
. Basically they come in two different types
Original- Built by the old Audio Innovations. These are (I think) only in black and run a Class A amp so you can use it as a hotplate as well. (Edit, no, these where made in chrome as well) The CD might have quite a bit in common with the old Arcam Alpha 7 (same mech certainly)- the prototype was an Alpha 7 in an Alto Box
An externally hosted image should be here but it was not working when we last tested it.
. These sound nice and have some support from Definitive Audio. They obviously don't look as smart in black and they are rare and not hugely reliable.Second batch- Built by us in the Chrome. The key difference is that the CD section had a tuner module (not a shabby one either- its the one from the Creek T43/Cambridge T500) and could be driven by a single remote as the two units were connected with a "canbus" (RJ45) lead with the socket on the back (the old ones don't have this). These units have a fair amount in common with the Cambridge Audio D500/A500 but the heat sink was squashed to fit in and this meant that the amp was more fragile than the standard A500. The display on the CT1 CD player was also frighteningly complicated as it was a sandwich with the CD section on one layer and the tuner on the other. These fail. Lots.
If you really want them, the bay is the best place but shop carefully- remotes and the original short RJ45 leads are now extinct. The stand is unbelievably rare as it never sold and only one batch was made.
HTH
thanks ultraprime .. I agree with the tuner not being too bad at all.. Im still not conviced about the amplifier being simler to the cambridge a500 the amplifier uses dual rail psu but is quasi complimentary . the later alto is fully complimentary... As for the ealier version being class A i dont think so it was based on a lynsley hood class a design but it is biased A/B .. The heatsinks are very small so deff not class A.. Now got pictures of unternals of the amplifier .. Will have to get a data cable as the bluetooth on my phone is duff
The specs i have found say it does 50W Rms 8 Ohms.. I guess if pushed it would also get a little on the warm side.. I would like to compare aswell.Im glad the only thing i needed to do to this amplifier was to re dress and solder a three core ribbon cable to the led that reside in the volume control knob. any repairs to the amplifier would require totall srip down to gain acces to underside of the PCB. The cd/tuner i aquired along with the amplifier just needed the laser cleaning and a new belt for the draw.. All in all not a bad find
I have an Alto amplifier with main board K4043/6 and since sunday an issue...
During normal operation all of a sudden both channels, no sound anymore. powerled still on.
Just re-solder the whole thing or if u want to be selective, solder the hot areas (near heatsinks and power resistors). Should solve the problem.
Gajanan Phadte
During normal operation all of a sudden both channels, no sound anymore. powerled still on.
Just re-solder the whole thing or if u want to be selective, solder the hot areas (near heatsinks and power resistors). Should solve the problem.
Gajanan Phadte