Continuing with my learning journey! The orginal op amp was powered using pins 4 & 8 ( had a look at the spec sheet) so would an OPA627 work anyway? I got the idea from this gentleman :
whatishifi: Modifing a ROTEL RC-970BX pre-amp and op-amp comparisons.
I have already put in the larger capacitors.
I have ordered a DIP 8 base from RS and ordered one of these:
2x Dual Single DIP8 to Single DIP8 OP-Amp Opamp Adaptor Gold-Plated Converter | eBay
Do you think it will work? I will of course just try it on one channel before ordering a second OPA627. When I put the OPA627 in there was just a tinny sound coming out on one channel only but that may have been beacuse I disturbed the board while removing the orginal OP amp. The board is so large with very little on it I did not think it would get disturbed!
Incidentally I changed the AN7062 IC (18 pin) on my Technics SUV4x and ended up with an intermitent channnel. This was because I had disturbed the relay solder connections while removing the old IC. All good now with DC at speaker terminals down to 3.5mv per channel.
The learning journey continues........
whatishifi: Modifing a ROTEL RC-970BX pre-amp and op-amp comparisons.
I have already put in the larger capacitors.
I have ordered a DIP 8 base from RS and ordered one of these:
2x Dual Single DIP8 to Single DIP8 OP-Amp Opamp Adaptor Gold-Plated Converter | eBay
Do you think it will work? I will of course just try it on one channel before ordering a second OPA627. When I put the OPA627 in there was just a tinny sound coming out on one channel only but that may have been beacuse I disturbed the board while removing the orginal OP amp. The board is so large with very little on it I did not think it would get disturbed!
Incidentally I changed the AN7062 IC (18 pin) on my Technics SUV4x and ended up with an intermitent channnel. This was because I had disturbed the relay solder connections while removing the old IC. All good now with DC at speaker terminals down to 3.5mv per channel.
The learning journey continues........
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The majority of dual opamps use pins 4 and 8 for the power supply while the majority of singles use pins 4 and 7.
Will the OPA627 work on those adapter boards ? Yes, at a basic level. And it could be very good but as always you should use caution and always back up any changes with some tests.
This shows the sort of thing that can go wrong:
http://www.diyaudio.com/forums/anal...u-have-checked-see-its-stable-havent-you.html
Will the OPA627 work on those adapter boards ? Yes, at a basic level. And it could be very good but as always you should use caution and always back up any changes with some tests.
This shows the sort of thing that can go wrong:
http://www.diyaudio.com/forums/anal...u-have-checked-see-its-stable-havent-you.html
Hi
Thanks for the info. Obviously I do not have a scope and do not know how to use one yet.
As I have the OPA627 now and cannot return it I will have a go anyway with the adaptor board at some point when it arrives from Hong Kong. I am not too worried if the opamp gets fried ( I have a spare original op amp, £2 from RS components) but could it destroy other componenets on the pre amp in your opinion?
I got the unit for free (not working apparantly but it was just loose RCA connections) which is why I am experimenting and wanted to have a tinker with it after reading the blog link about it above.
Thanks for the info. Obviously I do not have a scope and do not know how to use one yet.
As I have the OPA627 now and cannot return it I will have a go anyway with the adaptor board at some point when it arrives from Hong Kong. I am not too worried if the opamp gets fried ( I have a spare original op amp, £2 from RS components) but could it destroy other componenets on the pre amp in your opinion?
I got the unit for free (not working apparantly but it was just loose RCA connections) which is why I am experimenting and wanted to have a tinker with it after reading the blog link about it above.
Opamps are pretty tough in themselves, the only things that will kill them are incorrect supply connections or feeding excess voltages into the inputs.
No conceivable problems should occur that could damage the preamp.
No conceivable problems should occur that could damage the preamp.
Mooly, really appreciate the support and advice. I don't really have much time for my vintage electronics hobby and have to grab a chunck of time here and there at weekends ... family and work, etc so it is all a bit rushed.
Another quick question and apologies for its basic nature but I am assuming you can just slot an op amp into the dip8 base /dual op amp holder without soldering? If so can you / should you solder once it is all working!?
Just repaired the speaker terminals (I think) of the RB 970BX - Power Amp part of the combination and set the bias (very fiddly - walk past it and it goes nuts so went for a best fit). Had to replace the terminals with binding posts as they were broken. It is a bit messy but seems to be working! No doubt I will have to have another go.
DC at speaker terminals is around 40 - 50 mv - always seems to be high on Rotels.
Thanks
Another quick question and apologies for its basic nature but I am assuming you can just slot an op amp into the dip8 base /dual op amp holder without soldering? If so can you / should you solder once it is all working!?
Just repaired the speaker terminals (I think) of the RB 970BX - Power Amp part of the combination and set the bias (very fiddly - walk past it and it goes nuts so went for a best fit). Had to replace the terminals with binding posts as they were broken. It is a bit messy but seems to be working! No doubt I will have to have another go.
DC at speaker terminals is around 40 - 50 mv - always seems to be high on Rotels.
Thanks
The adapters you linked to solder to the main PCB of course, but the IC's you fit are just a push fit into the sockets. Never try and solder an IC into a socket, that's bad practice.
Bias can very variable on a lot of amps... variable here meaning it is prone to thermal drift. Probably the best you can do is follow the procedure in the manual and don't be tempted to set it higher than spec.
50mv might sound a lot but if you calculate the current into 8 ohms that is caused by 50mv, and also calculate the power dissipated into 8 ohms then you will see it is a non issue.
Bias can very variable on a lot of amps... variable here meaning it is prone to thermal drift. Probably the best you can do is follow the procedure in the manual and don't be tempted to set it higher than spec.
50mv might sound a lot but if you calculate the current into 8 ohms that is caused by 50mv, and also calculate the power dissipated into 8 ohms then you will see it is a non issue.
Hi
Minor update. Installed the DIP8 base and had a channel go again on the board but easily fixed with some re soldering. Works well with the a replacement original op amp. Still waiting for the double op amp attachment to try with my single OPA627 to see if it works OK before spending more money on a second one!
Also replaced the broken CD RCA input on the pre amp. Rotel were unhelpful but found a replacement on ebay with the correct fitting although not "gold" plated like the original. I had to remove the back plate to solder the new part in.
Works fine.
Minor update. Installed the DIP8 base and had a channel go again on the board but easily fixed with some re soldering. Works well with the a replacement original op amp. Still waiting for the double op amp attachment to try with my single OPA627 to see if it works OK before spending more money on a second one!
Also replaced the broken CD RCA input on the pre amp. Rotel were unhelpful but found a replacement on ebay with the correct fitting although not "gold" plated like the original. I had to remove the back plate to solder the new part in.
Works fine.
It all sounds like you are getting there. Let's hope your OPA627 experiments come good... it will be interesting to know what you make of them.
Hi
Latest update. Hopefully this is useful for any other newbs trying this!
Received the double DIP 8 op amp adaptor but had to de solder the single DIP 8 adaptor that I had already installed - once again did not realise that you could not just slot it in!
Before I soldered the double adaptor in I wanted to test my single OPA627 to see it it worked on one channel. Seemed to work OK but thought I should remove it before soldering the adaptor in.
While trying to remove the OPA627, I found that it was sticking to the adaptor as it had some residual solder on it from when I removed it previously and ended up bending and breaking one of the pins. Fortunately it was PIN8 which has no connections on the OPA627!
Installed everything and appears to work on the one channel so I have ordered a second OPA627 for the other channel. Hopefully it will all work and not a waste of ££ but had to see it through to the end as I had started it!
Will report back
Latest update. Hopefully this is useful for any other newbs trying this!
Received the double DIP 8 op amp adaptor but had to de solder the single DIP 8 adaptor that I had already installed - once again did not realise that you could not just slot it in!
Before I soldered the double adaptor in I wanted to test my single OPA627 to see it it worked on one channel. Seemed to work OK but thought I should remove it before soldering the adaptor in.
While trying to remove the OPA627, I found that it was sticking to the adaptor as it had some residual solder on it from when I removed it previously and ended up bending and breaking one of the pins. Fortunately it was PIN8 which has no connections on the OPA627!
Installed everything and appears to work on the one channel so I have ordered a second OPA627 for the other channel. Hopefully it will all work and not a waste of ££ but had to see it through to the end as I had started it!
Will report back
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Final update
Fitted an OPA627 onto the other channel. Works well. Initially did not sound amazing but after a few hours of use noticing that it sounds pretty good. I was using my Technics SUV7 before this but I would not say the Rotel sounds any better. All very subjective of course and it depends what day of the week it is!
Worth the £60 in parts? As I got this pre amp / amp combo for free yes but not necessarily if I had already paid for a second hand unit on ebay.
Hope this helps somebody.
Fitted an OPA627 onto the other channel. Works well. Initially did not sound amazing but after a few hours of use noticing that it sounds pretty good. I was using my Technics SUV7 before this but I would not say the Rotel sounds any better. All very subjective of course and it depends what day of the week it is!
Worth the £60 in parts? As I got this pre amp / amp combo for free yes but not necessarily if I had already paid for a second hand unit on ebay.
Hope this helps somebody.
Interesting...
I find you need to listen over an extended period to make real judgements as you r expectations will be sky high having just fitted the parts. If it still seems good in a week, a month or a year from now then the improvement or change could be real and you are liking the result. If you constantly keep wondering, are not sure etc then revert back and do an extended listening test again.
Hopefully your mods are for keeps 🙂
I find you need to listen over an extended period to make real judgements as you r expectations will be sky high having just fitted the parts. If it still seems good in a week, a month or a year from now then the improvement or change could be real and you are liking the result. If you constantly keep wondering, are not sure etc then revert back and do an extended listening test again.
Hopefully your mods are for keeps 🙂
I will not be changing anything again now unless something fails. Actually one thing I have noticed is that the amp appears to get louder earlier on the volume control.
Hmmm...
well that could be imagination or..... this is why its really important to back up any changes with some basic measurements and scope checks. A change of opamp would not alter the gain of the stage.
well that could be imagination or..... this is why its really important to back up any changes with some basic measurements and scope checks. A change of opamp would not alter the gain of the stage.
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