I think this product is a great example on how to make an extremely complex and no doubt very expensive product to fool people with too much money into thinking that it will sound better than the headphone jack on many amplifiers!
From time to time I come across a channel that has a video or two on some piece of weird and obscure equipment, but this channel has 'em in spades LoL. Love it! The trials and tribulations of people that are trying to find the next big thing in circuitry and the people who have to deal with the aftermath LoL...
The trimmer on the input might be to compensate for hf loss due to high input resistance and stray wiring capacitance. Kind of like a scope input attenuator. Nice box that is in. Maybe strip all of it out except the transformer and build a nice all tube preamp and headphone driver in there.
I have a Melos MA 333 Reference (Music Director) and it sounds superb, when it's working correctly, the Pho-tentiometer is a nightmare. If the light isn't completely dead center it throws everything off. I would love to be able to put either a stepped attenuator or a TVC and a normal balance control in it's place.
Hello again, I just picked one of these pre amps for $80. Started going through it. There are 4 Capacitors, 2 on each side of the main board. 12 Uf each, 400 Volts. Made in France. Large round and Black Caps. One of them has a small hole on the side and I can see Grey material. It is NOT leaking and the hole is not deep, it is shallow. My question is: Does this effect the working of that Cap and should I replace it ?? Or is it OK ? I took some photos which I can send to you. Thanks so much.
Thank you for the reply! I am fixing this for a friend who wants to use it as a head phone amp. I don't have the level of knowledge and experience you do though, but your schematics helped locate the issues. I am looking for the volume fuse bulb. I could not locate a Buss MDL 1&1/4 (it was burnt out) so I am using a JKLGF550 fuse bulb. The volume works though it doesn't seem to have much volume when set to Class A. When set to Monitor, volume is loud even though it is set to minimum. I have no operation manual, so I am unsure if I have a problem or you are suppose to use Class A setting with headphones.
I have a chance to buy one of these in the US for $100. It is a high end and expensive item. It needs some repairs. Do you think I should buy it ?? Is it worth it ?
I'm a fan of this old time piece of junk amp. I'm not trying to be sarcastic either, I fully recognize it's an awful design but I actually use my amp every day. Several years ago I did a recap and ripped out the photo-board for a Tortuga Audio LDR control; I think you can even see what I did back in 2016 by quick google search, I wasn't even the first to do it. Sometime in that process I lost the mute function completely and I ended up removing the relays and living without the mute feature. It would be helpful to get it back so I will have to double check what you've shown here! I fully realize I am nowhere near your level of expertise as well, it's going to take me years to catch up on your circuit analysis of the amp.
Ricky Av : persevere. It is worth it. On this circuit (which is a great example of a bad design working well) the mute is simple, and I don’t know how you will re-instate it on yours with the new board, but the quest is half the fun. I did in fact see your conversion when I was looking for info on this beast, so thank you. Every bit of info helps.
You have, as I hoped, really many fantastic videos, this is no. 24 I have enjoyed, out of 24:-) I hope that you please will answer this question: LDR's are wary unliniar as analog volume control, while some variable optocouplers are fare better, but still not the best. Can digital idolators be used as a analog volume control, just by adjusting voltage / current?
Very, very, very well done, extraordinary explanation of what was really obscure. Thanks a lot!
My pleasure
I think this product is a great example on how to make an extremely complex and no doubt very expensive product to fool people with too much money into thinking that it will sound better than the headphone jack on many amplifiers!
From time to time I come across a channel that has a video or two on some piece of weird and obscure equipment, but this channel has 'em in spades LoL. Love it! The trials and tribulations of people that are trying to find the next big thing in circuitry and the people who have to deal with the aftermath LoL...
:)
Overly complicated for no good reason. Enjoyed the video anyway, thanks for the upload.
The trimmer on the input might be to compensate for hf loss due to high input resistance and stray wiring capacitance. Kind of like a scope input attenuator. Nice box that is in. Maybe strip all of it out except the transformer and build a nice all tube preamp and headphone driver in there.
I have a Melos MA 333 Reference (Music Director) and it sounds superb, when it's working correctly, the Pho-tentiometer is a nightmare. If the light isn't completely dead center it throws everything off. I would love to be able to put either a stepped attenuator or a TVC and a normal balance control in it's place.
👍
It's like counting the hoofs and divide by four to know how many cows are there...
Unless one cow has lost a leg ... 😃
Hello again, I just picked one of these pre amps for $80. Started going through it. There are 4 Capacitors, 2 on each side of the main board. 12 Uf each, 400 Volts. Made in France. Large round and Black Caps. One of them has a small hole on the side and I can see Grey material. It is NOT leaking and the hole is not deep, it is shallow. My question is: Does this effect the working of that Cap and should I replace it ?? Or is it OK ? I took some photos which I can send to you. Thanks so much.
Thank you for the great video and schematics! Do you have a source for replacement fuse bulb for the volume control?
You’re welcome. Yes, I have quite a stock of parts collected over the years.
Thank you for the reply! I am fixing this for a friend who wants to use it as a head phone amp. I don't have the level of knowledge and experience you do though, but your schematics helped locate the issues. I am looking for the volume fuse bulb. I could not locate a Buss MDL 1&1/4 (it was burnt out) so I am using a JKLGF550 fuse bulb. The volume works though it doesn't seem to have much volume when set to Class A. When set to Monitor, volume is loud even though it is set to minimum. I have no operation manual, so I am unsure if I have a problem or you are suppose to use Class A setting with headphones.
Hi,
Would you be willing to give me some guidance on how to fix this unit please ? Thanks
I’m afraid that’s not possible. I do this as a hobby and already use all my spare time on the projects that I have under way.
I have a chance to buy one of these in the US for $100. It is a high end and expensive item. It needs some repairs. Do you think I should buy it ?? Is it worth it ?
This item has quite a cult following, so prices are usually quite high. Whether it’s worth it depends on you. I know that it costs a lot more here.
I'm a fan of this old time piece of junk amp. I'm not trying to be sarcastic either, I fully recognize it's an awful design but I actually use my amp every day. Several years ago I did a recap and ripped out the photo-board for a Tortuga Audio LDR control; I think you can even see what I did back in 2016 by quick google search, I wasn't even the first to do it. Sometime in that process I lost the mute function completely and I ended up removing the relays and living without the mute feature. It would be helpful to get it back so I will have to double check what you've shown here! I fully realize I am nowhere near your level of expertise as well, it's going to take me years to catch up on your circuit analysis of the amp.
Ricky Av : persevere. It is worth it. On this circuit (which is a great example of a bad design working well) the mute is simple, and I don’t know how you will re-instate it on yours with the new board, but the quest is half the fun.
I did in fact see your conversion when I was looking for info on this beast, so thank you. Every bit of info helps.
You have, as I hoped, really many fantastic videos, this is no. 24 I have enjoyed, out of 24:-)
I hope that you please will answer this question: LDR's are wary unliniar as analog volume control, while some variable optocouplers are fare better, but still not the best. Can digital idolators be used as a analog volume control, just by adjusting voltage / current?
I haven’t actually tried them, so unfortunately I don’t know. Interesting question which may lead to some investigation in the future.
@@electronicsoldandnew Yes that could be interesting:-)
Also the solder joints on this unit seem to be all poorly done (Cold solder), why ??
Too many people messed around with it.
@@electronicsoldandnew Is it worth buying one of these units used for $100 ? It needs some repairs. Thanks.
Can you fix my Milos sha gold?
Afraid not. I have a series of projects on the go, and far too little time right now.
Boa tarde, tenho 2 pre amplificadores que precisam de ser reparados . Seria possível ceder-me o seu contacto ?
Cumprimentos
Manuela Freitas
O meu Mail : nelaccunha@gmail.com
já respondi por email.