Hi kchu
Been away for a break. Congrats you got the amp kicking again. The volume problem could be due to solder residue or bad soldering. You should have warned me you gonna change those opamps, i think theres some changes youll have to make before lm4562 can be used successfully in these positions. Also dont change parts and immediatly dismiss them, let them run in. It takes at least a day or 2 before they will start sounding right. Have you found the problem yet??
Ill make a list of the caps which most contribute to the sound and post here later.
Alex
PS quattor is right you have to check the quiscent current and adjust it to the new parts.
Been away for a break. Congrats you got the amp kicking again. The volume problem could be due to solder residue or bad soldering. You should have warned me you gonna change those opamps, i think theres some changes youll have to make before lm4562 can be used successfully in these positions. Also dont change parts and immediatly dismiss them, let them run in. It takes at least a day or 2 before they will start sounding right. Have you found the problem yet??
Ill make a list of the caps which most contribute to the sound and post here later.
Alex
PS quattor is right you have to check the quiscent current and adjust it to the new parts.
Hi kchu
Been away for a break. Congrats you got the amp kicking again. The volume problem could be due to solder residue or bad soldering. You should have warned me you gonna change those opamps, i think theres some changes youll have to make before lm4562 can be used successfully in these positions. Also dont change parts and immediatly dismiss them, let them run in. It takes at least a day or 2 before they will start sounding right. Have you found the problem yet??
Ill make a list of the caps which most contribute to the sound and post here later.
Alex
PS quattor is right you have to check the quiscent current and adjust it to the
Been away for a break. Congrats you got the amp kicking again. The volume problem could be due to solder residue or bad soldering. You should have warned me you gonna change those opamps, i think theres some changes youll have to make before lm4562 can be used successfully in these positions. Also dont change parts and immediatly dismiss them, let them run in. It takes at least a day or 2 before they will start sounding right. Have you found the problem yet??
Ill make a list of the caps which most contribute to the sound and post here later.
Alex
PS quattor is right you have to check the quiscent current and adjust it to the
Hi Suresh
I saw in another thread you had rb970bx. I still own one of these, very reliable and were very good for their time. Mine are catching dust in my garage as i have other amps now. Anyway the circuitry is very similar to the ra1072 here, the amp is virtually the same, although preamp has been upgraded.
How much electronics knowledge do you have?? Soldering and using multimeter??
I never gave that list of caps as kchu seemed to have his problem solved and never returned here. The caps on the rb970 model i wouldnt touch though, i know they are all black gates and very very good. There are better black gates to be had but only the top of range which are expensive. Even if your amp has some 10, 12 years they will still be good.
What do you want to improve regarding the sound???
Does your particular one use ad827 opamps like the first couple of models released. These were the best sounding ones as later models used opa2134?
Let me see if i have the manual for that model, i know i have the 971, which is virtually identical with only some differences in preamp.
Alex
I saw in another thread you had rb970bx. I still own one of these, very reliable and were very good for their time. Mine are catching dust in my garage as i have other amps now. Anyway the circuitry is very similar to the ra1072 here, the amp is virtually the same, although preamp has been upgraded.
How much electronics knowledge do you have?? Soldering and using multimeter??
I never gave that list of caps as kchu seemed to have his problem solved and never returned here. The caps on the rb970 model i wouldnt touch though, i know they are all black gates and very very good. There are better black gates to be had but only the top of range which are expensive. Even if your amp has some 10, 12 years they will still be good.
What do you want to improve regarding the sound???
Does your particular one use ad827 opamps like the first couple of models released. These were the best sounding ones as later models used opa2134?
Let me see if i have the manual for that model, i know i have the 971, which is virtually identical with only some differences in preamp.
Alex
Dear Alex,
i am an electronics engineer working in R&D department. i know electronics well and i use fluke tools.
my ROTEL uses AD827 op amp. i have the circuit diagram. please provide me your email id to tmr_suresh@yahoo.com. i will send it to you. when i read your thread about rotel you have mentioned some improvements can be made. for input coupling polypropylene caps are better. also from preamp output there is a cap and again there is a cap in power amp input. the purpose is to avoid dc to enter the power amp. so why two electrolytic caps in between pre and power ? instead it can be replaced by one polypropylene . i know this will definetly improve sound . also at what bias current these amps sound good.
even thoug i know electronics i dont have prior experience with rotel. that is why i am requesting your help. your ideas and suggestions are welcome.
regards
i am an electronics engineer working in R&D department. i know electronics well and i use fluke tools.
my ROTEL uses AD827 op amp. i have the circuit diagram. please provide me your email id to tmr_suresh@yahoo.com. i will send it to you. when i read your thread about rotel you have mentioned some improvements can be made. for input coupling polypropylene caps are better. also from preamp output there is a cap and again there is a cap in power amp input. the purpose is to avoid dc to enter the power amp. so why two electrolytic caps in between pre and power ? instead it can be replaced by one polypropylene . i know this will definetly improve sound . also at what bias current these amps sound good.
even thoug i know electronics i dont have prior experience with rotel. that is why i am requesting your help. your ideas and suggestions are welcome.
regards
Ok Suresh in that case you can take it quite far.
Two caps are used because of several reasons and in some cases rotel got it wrong. First both the preamp and the power amp have their idividual offsets, secondly and here they got it wrong, to create a unipolar cap at the same time which has several advantages. On the earlier models they got it wrong as the polarities on the boards are wrong to get a unipolar cap, in the recent models this has been rectified. Personally on my 971 i use one unipolar blackgate NX series, although i did try poliprops. The reason is mostly beacause i wanted to keep the board more or less the same and not have parts somewhere over the board and the nx takes one position and the other just gets a link. Some of the high quality polyprops did sound better to me, i used smaller values than the electrolytics but as you know they pretty big. You can go ahead and experiment with poliprops there are some very good although expensive ones on the market.
My bias is set at 13mv across the output resistors. Several tests and simulations done here on this forum by high end audio engineers have shown that for class AB the optimum value is around 10 to 25. Mine is slightly higher than the factory preset which if i can remember correctly is 8mv. Although this amp is rated at 70w youll notice it will give you more like 90w, the problem is the smallish heatsink. Although factory standard setting shows little sign of crossover distortion, a slightly higher setting gave lower odd order harmonics ableit the heat did increase.
My email is alexmiguel33@hotmail.com
ALEX
Two caps are used because of several reasons and in some cases rotel got it wrong. First both the preamp and the power amp have their idividual offsets, secondly and here they got it wrong, to create a unipolar cap at the same time which has several advantages. On the earlier models they got it wrong as the polarities on the boards are wrong to get a unipolar cap, in the recent models this has been rectified. Personally on my 971 i use one unipolar blackgate NX series, although i did try poliprops. The reason is mostly beacause i wanted to keep the board more or less the same and not have parts somewhere over the board and the nx takes one position and the other just gets a link. Some of the high quality polyprops did sound better to me, i used smaller values than the electrolytics but as you know they pretty big. You can go ahead and experiment with poliprops there are some very good although expensive ones on the market.
My bias is set at 13mv across the output resistors. Several tests and simulations done here on this forum by high end audio engineers have shown that for class AB the optimum value is around 10 to 25. Mine is slightly higher than the factory preset which if i can remember correctly is 8mv. Although this amp is rated at 70w youll notice it will give you more like 90w, the problem is the smallish heatsink. Although factory standard setting shows little sign of crossover distortion, a slightly higher setting gave lower odd order harmonics ableit the heat did increase.
My email is alexmiguel33@hotmail.com
ALEX
Thanks very much guys. 
Couple of spurious Rs in the link though!
www.audio-circuit.dk/Schematics/Rotel-RA1062-int-sm.pdf
Couple of spurious Rs in the link though!
www.audio-circuit.dk/Schematics/Rotel-RA1062-int-sm.pdf
Rotel RA1060 probems
Hi,
I'm using this already open theme to ask and if possibly reslove several questions about my RA-1060.
I bought this amp fairly cheap, but since it has good potential, I would like to get maximum of it.
First opening revealed:
1. All this production run is obviously made using Panasonic FC, since my amp has not any Black Gate at all; the amp was never opened and solderet, it is clear.
The preamp is OPA2604, and for other pourpose (tone controls/headphones) there are two 2134s; in the schematics are listed here AD712.
2. DC offset is (to me) unacceptably high - 70mV and 60mV; often, it is said to be unmatched input transistors; I cannot order easy the original A1610/C2362K. Is there better transistors for this pourpose? Somwhere the Phillips BD139/140 are reccomended, but it seems to be overkill for that pourpose?
3. On first check, bias was some 2,5mV/0R22, too low; I make it stable to some 10-11mV, according to posts here, and althought it sounds a bit better - the older RA-971 blows it up, unmodded
4. How to change the sensitivity of the pot?
It is very difficult to adjust volume at low level, even at "8-9" o'clock, it is too loud...the pot is some Alps, motirized 50k unit, but not Alps Blue or slimilar class;
Any input appreciated
Hi,
I'm using this already open theme to ask and if possibly reslove several questions about my RA-1060.
I bought this amp fairly cheap, but since it has good potential, I would like to get maximum of it.
First opening revealed:
1. All this production run is obviously made using Panasonic FC, since my amp has not any Black Gate at all; the amp was never opened and solderet, it is clear.
The preamp is OPA2604, and for other pourpose (tone controls/headphones) there are two 2134s; in the schematics are listed here AD712.
2. DC offset is (to me) unacceptably high - 70mV and 60mV; often, it is said to be unmatched input transistors; I cannot order easy the original A1610/C2362K. Is there better transistors for this pourpose? Somwhere the Phillips BD139/140 are reccomended, but it seems to be overkill for that pourpose?
3. On first check, bias was some 2,5mV/0R22, too low; I make it stable to some 10-11mV, according to posts here, and althought it sounds a bit better - the older RA-971 blows it up, unmodded
4. How to change the sensitivity of the pot?
It is very difficult to adjust volume at low level, even at "8-9" o'clock, it is too loud...the pot is some Alps, motirized 50k unit, but not Alps Blue or slimilar class;
Any input appreciated
Last edited:
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.