Very cool, Thanks Tim and others for all of the info and your suggestions.
I currently have the amp hooked to my main rig to listen to it again and it definitely sounds average and muddy, the imaging is ok and soundstage is pretty wide but no front to back depth and it really needs more speed & attack, separation of instruments & definition especially bass but I'm comparing it to a very good amp. I've come to the conclusion with the help of this board that this amp can be quite good and has very good bones but it needs bit of tweaking to really get the most out of it. I believe this should be done by me or someone else otherwise this amp is just going to live a mediocre unfulfilling life in Purgatory.
I would like to thank Timpert, Xoc1 and zeonrider for your help.
The changes and suggestions is definitely over my head design wise but with a bit of reading and learning it will start making more sense and I'm up for a good challenge. I'll need to learn and identify everything on the board and which ones are Q3,4,5. I definetly do not want to redesign the board but I'm quite comfortable leg bending new ones to make it fit onto the existing board. Would more detailed photo's help? I hope you don't mind but I will still need any tips and suggestions from this board that you can offer.
I do have a friend who lives close by that builds a lot of his own electronics but is not really an audiophile. With his help the two of us may be able to pull this off.
With the MJE350 & MJE340 are there different manufacturers that are better quality than others for this duty? I don't mind spending a little on the parts if it will help sound quality. I found some Cardas soldering wire and flux I had in the garage. Is there anything else that could use some tweaking or upgrading?
How about the capacitors? Some of you have mentioned them.
Another question I have is why are there so many conductors lead to the binding posts?
I currently have the amp hooked to my main rig to listen to it again and it definitely sounds average and muddy, the imaging is ok and soundstage is pretty wide but no front to back depth and it really needs more speed & attack, separation of instruments & definition especially bass but I'm comparing it to a very good amp. I've come to the conclusion with the help of this board that this amp can be quite good and has very good bones but it needs bit of tweaking to really get the most out of it. I believe this should be done by me or someone else otherwise this amp is just going to live a mediocre unfulfilling life in Purgatory.
I would like to thank Timpert, Xoc1 and zeonrider for your help.
The changes and suggestions is definitely over my head design wise but with a bit of reading and learning it will start making more sense and I'm up for a good challenge. I'll need to learn and identify everything on the board and which ones are Q3,4,5. I definetly do not want to redesign the board but I'm quite comfortable leg bending new ones to make it fit onto the existing board. Would more detailed photo's help? I hope you don't mind but I will still need any tips and suggestions from this board that you can offer.
I do have a friend who lives close by that builds a lot of his own electronics but is not really an audiophile. With his help the two of us may be able to pull this off.
With the MJE350 & MJE340 are there different manufacturers that are better quality than others for this duty? I don't mind spending a little on the parts if it will help sound quality. I found some Cardas soldering wire and flux I had in the garage. Is there anything else that could use some tweaking or upgrading?
How about the capacitors? Some of you have mentioned them.
Another question I have is why are there so many conductors lead to the binding posts?
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Many a good amp has fallen to "tweaking".
Sell it to someone who will appreciate it and buy something to practice "tweaking". If big improvements are possible with a "mediocre" amp, imagine what can be accomplished with a "poor" one.
This is a nice, powerful and well made amp, a shame to mess with it. If you make even a small error the very expensive output devices will be lost. As John suggests, I would experiment on something simpler and cheaper to repair if you make a mistake. Maybe once you have some proper skills you can then return to this amp.
Many a good amp has fallen to "tweaking".
Sell it to someone who will appreciate it and buy something to practice "tweaking". If big improvements are possible with a "mediocre" amp, imagine what can be accomplished with a "poor" one.
Your right and thank you for the suggestions but I currently consider this one as a poor one in it's present state (good expensive parts and well made but with mediocre sound) and that seems like a pretty good and justifiable reason to try to make it better than leaving it in it's present purgatory state. I couldn't sell this amp in good faith to a end user.
Like I mentioned earlier, I am willing to trade it to someone who wants to work on it in exchange for a good sounding DIY amp until then I'm going to try to fix it and in doing so learn.
I currently have time on my hands and I'm actually very anal and would not change anything until I fully understand my actions, document what I'm changing and would double check any changes I make.
Don't laugh but I do manage a large electrical engineering firm and design large scale systems for concert halls and cultural institutions so I'm not completely daft but just haven't worked at a electronics/transistor level instead it's more like 5000kw systems.
I'm just asking for help on how to make this particular amp better.
Again, thanks for the ones who are helping.
Mr_macgee:
I've successfully upgraded an amp without really knowing what was going on circuit-wise, so it can be done.
Acurus amp mods thread
I've successfully upgraded an amp without really knowing what was going on circuit-wise, so it can be done.
Acurus amp mods thread
Just a suggestion , try to simulate it with LT spice. Any changes you make to the voltage stage ,(different devices or currents) will absolutely change the open loop gain and will require that you "recompensate" the amp.
It looks like this VAS is MPSA42/92 - high gain group , running at 2-3ma (that would depend on rail voltages). 2sa1381/2sc3503's(best) or mje340/350 (w/small heatsinks) could replace those and then you would have to change R9/10 (on the VAS -to get 10ma), R4 (this would rebalance the differential) ,bias trimmer would need to be 200R , you might even have to add degeneration to Q1/2 and change the HF lead compensation cap (C6). All this you would have to determine with a good LT session and the correct device models.
The "flaw" in this amp is it's lousy PSRR with no current sources and a single supply.
OS
Yup, a lot can be done to make this amp really good. My suggestions are only a start, I think that the compensation will be OK as it is, but I can't tell fur sure because I don't know the schematic of this particular amp. But Rond Elliott's P101 still seems like a very good starting point for a complete re-do of the amp, IMHO the best option. Like Mr Mcgee said, the amp has good bones but the current circuit just doesn't get the best out of them.
Thanks Tosh.
I'll need to take in what everyone has written and try to make sense out of it all and decide how best to proceed.
Hi Roar,
Thanks for the info. Now that you said it; I do remember the builder mentioning Muse 100 quite a bit.
While working on your Muse, what did you end up changing during improvements? After your changes, what did you think of the overall sound?
Cheers
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