New op amp
Mike,
I had noticed the announcement too. Considering how nice the 6172's sound a newer version with lower bias current will be nice. I am going to look into it and get some samples to try. It probably will still require a double cap (+/-) input to balance the offset.
Roger
Mike,
I had noticed the announcement too. Considering how nice the 6172's sound a newer version with lower bias current will be nice. I am going to look into it and get some samples to try. It probably will still require a double cap (+/-) input to balance the offset.
Roger
I recently fitted the T-network capacitors, these are by far the best capacitors I've tried and I have tried quite a few including Evox Rifa,Philips Q and various ones from Elna and Nichicon.
The wiring implementation certainly makes a difference and I'd like to say a big thank you to Chris (ClassD4sure) for all the advice regarding wiring these things up😎
For the op-amps on the UCD isn't there a way to improve the actual regulation on the pcb? somebody suggested on another site to Replace the bias resistor to the 12v Zener by a constant current diode like the J511, has anybody tried something like this?
The wiring implementation certainly makes a difference and I'd like to say a big thank you to Chris (ClassD4sure) for all the advice regarding wiring these things up😎
For the op-amps on the UCD isn't there a way to improve the actual regulation on the pcb? somebody suggested on another site to Replace the bias resistor to the 12v Zener by a constant current diode like the J511, has anybody tried something like this?
On board regulator
Of course the best solution would be an off board separate power supply but things can be done to the existing one as you pointed out. The regulator is very simple and basically a modified cap multiplier. Supplying the zener from a current source is a worthy idea but probably not as much benefit as upgrading the caps around the circuit and possibly figuring some way to implement an lm431 circuit to replace the zener. A higher gain lower noise transistor would also be of benefit. I have not looked into any of this other than the cap issue. Keep us up to date if you do get into it.
Roger
Of course the best solution would be an off board separate power supply but things can be done to the existing one as you pointed out. The regulator is very simple and basically a modified cap multiplier. Supplying the zener from a current source is a worthy idea but probably not as much benefit as upgrading the caps around the circuit and possibly figuring some way to implement an lm431 circuit to replace the zener. A higher gain lower noise transistor would also be of benefit. I have not looked into any of this other than the cap issue. Keep us up to date if you do get into it.
Roger
Re: On board regulator
Thank you Roger.
Only small problem is that I have the UCD180 and all the parts for the op-amp regulation is SMD, there only seems to be a 0.1uf ceramic cap on the output of the transistors.
there seems to be more caps on the UCD400 regulation
sx881663 said:
Thank you Roger.
Only small problem is that I have the UCD180 and all the parts for the op-amp regulation is SMD, there only seems to be a 0.1uf ceramic cap on the output of the transistors.
there seems to be more caps on the UCD400 regulation
Cap question?
The 400's have the same output and use a larger through hole cap on the zener. I think this was a 10uf originally. This cap can be substantially up graded and up sized. I am using a 100uf low ESR type myself. I think the 180 is the same layout but am not sure.
Roger
The 400's have the same output and use a larger through hole cap on the zener. I think this was a 10uf originally. This cap can be substantially up graded and up sized. I am using a 100uf low ESR type myself. I think the 180 is the same layout but am not sure.
Roger
Re: Cap question?
I can't see any electrolytic cap on the UCD180, probably just a small ceramic.
My pair of transformers also have a separate LT secondarys so it may be worth just building some regulation, only thing is the HT are 2 x 0-30 and the LT is centre tapped, would that be worse than having dual secondarys for the LT?
sx881663 said:
I can't see any electrolytic cap on the UCD180, probably just a small ceramic.
My pair of transformers also have a separate LT secondarys so it may be worth just building some regulation, only thing is the HT are 2 x 0-30 and the LT is centre tapped, would that be worse than having dual secondarys for the LT?
Center tap question
T,
I personally much prefer dual secondaries. This is because the ripple currents can be kept out of the common ground connection. You might be able to physically separate the 2 wires for the centertap and make it into dual windings. I have done this on several occasions. It is not unusual for there to be 2 wires for the centertap in the larger toroids. If not just use very short connections and large wires for the common connections. Be careful to not cause additional ground loops.
The whole concept of off board supplies and regulation is a good one as it keeps the switching frequencies out of the opamp circuit.
Roger
T,
I personally much prefer dual secondaries. This is because the ripple currents can be kept out of the common ground connection. You might be able to physically separate the 2 wires for the centertap and make it into dual windings. I have done this on several occasions. It is not unusual for there to be 2 wires for the centertap in the larger toroids. If not just use very short connections and large wires for the common connections. Be careful to not cause additional ground loops.
The whole concept of off board supplies and regulation is a good one as it keeps the switching frequencies out of the opamp circuit.
Roger
Re: Center tap question
Thanks again Roger!
I don't understand why the HT windings are duals and the LT's are centre tapped😕 I've also separated the two ct's in other transformers but the only snag is that these ones are wrapped in that black bandage like stuff and the inside is filled with that epoxy with a small hole drilled in the middle for the bolt, I'll see if its possible to get at it without making too much mess🙂
sx881663 said:
Thanks again Roger!
I don't understand why the HT windings are duals and the LT's are centre tapped😕 I've also separated the two ct's in other transformers but the only snag is that these ones are wrapped in that black bandage like stuff and the inside is filled with that epoxy with a small hole drilled in the middle for the bolt, I'll see if its possible to get at it without making too much mess🙂
Re: On board regulator
...and for all that effort, it's easier just to go with the aux supply. For the cost of current regulator diodes, I'll keep the resistor!
The 180's are just ceramics, both local to the op amp and regulator. The newest 400's change both of those to electrolytics.
sx881663 said:
...and for all that effort, it's easier just to go with the aux supply. For the cost of current regulator diodes, I'll keep the resistor!
The 180's are just ceramics, both local to the op amp and regulator. The newest 400's change both of those to electrolytics.
180/400
Chris,
Thanks for that info. I haven't worked with any 180's or new 400's so didn't know.
Roger
Chris,
Thanks for that info. I haven't worked with any 180's or new 400's so didn't know.
Roger
Re: LM4562
Hi Mike,
It sure sounds like it's worth a try, I'll be going for a few samples too. Have you had the chance to give them a listen yet?
Cheers,
Chris
Portlandmike said:
Hi Mike,
It sure sounds like it's worth a try, I'll be going for a few samples too. Have you had the chance to give them a listen yet?
Cheers,
Chris
Re: New op amp
Hi Roger,
Not sure you'll need the coupling caps.
10nA *100k is 10e-9*1e5 is 1mV. Well within the trim range of the later ucd400's.
Also, if you're already DC coupled from the preamp, its likely going to be less than that.
btw, in studying that LM4562 a but, it looks like the PSSR is more or less symetric when you supply it with +/-15V rather than 12 or 17V supplies. Also, the distortion is steller, but that op amp really wants 5V of headroom from the rails or the distortion isn't so hot.
Thus, given that op amps >100dB PSSR, I think one would be better off raising the rails of the supply to ~+/-15V, a two resistor change, and might end up being actually better than another op amp with aux split supplies, but honestly I haven't looked at AD820 specs in a long time.
Bottom line the results that matter will be in the listening, but I've always been partial to bipolor over fets.
Mike
p.s. Roger, its unclear what the topology of this op amp is, but i think its a new process. NSC has had some cool new technology for low cost wafer trim using memory technology come on board recently, and they might be trimming to match the diffs and such.
The LM6172 is a topology that is basically a current feedback amp with a unity buffer on the inverting input to make it look more or less like voltage feedback. I like the LM6172, but in genral, CFA's have much higher bias current, like 1.2uA on the 6172 vs 10nA on the 4562.
I'm a bit curious and somewhat worried that they used bias current cancelation. When the offset is the same order as the bias current that's usually the case. AND, sometimes bias current cancelation isn't the best audio solution. Specs look very promising though.
I wonder who will get them plugged in first!
sx881663 said:
Hi Roger,
Not sure you'll need the coupling caps.
10nA *100k is 10e-9*1e5 is 1mV. Well within the trim range of the later ucd400's.
Also, if you're already DC coupled from the preamp, its likely going to be less than that.
btw, in studying that LM4562 a but, it looks like the PSSR is more or less symetric when you supply it with +/-15V rather than 12 or 17V supplies. Also, the distortion is steller, but that op amp really wants 5V of headroom from the rails or the distortion isn't so hot.
Thus, given that op amps >100dB PSSR, I think one would be better off raising the rails of the supply to ~+/-15V, a two resistor change, and might end up being actually better than another op amp with aux split supplies, but honestly I haven't looked at AD820 specs in a long time.
Bottom line the results that matter will be in the listening, but I've always been partial to bipolor over fets.
Mike
p.s. Roger, its unclear what the topology of this op amp is, but i think its a new process. NSC has had some cool new technology for low cost wafer trim using memory technology come on board recently, and they might be trimming to match the diffs and such.
The LM6172 is a topology that is basically a current feedback amp with a unity buffer on the inverting input to make it look more or less like voltage feedback. I like the LM6172, but in genral, CFA's have much higher bias current, like 1.2uA on the 6172 vs 10nA on the 4562.
I'm a bit curious and somewhat worried that they used bias current cancelation. When the offset is the same order as the bias current that's usually the case. AND, sometimes bias current cancelation isn't the best audio solution. Specs look very promising though.
I wonder who will get them plugged in first!
Re: Re: LM4562
Hi Chris,
Been a bit swamped with a captal S for the last few months with my paying audio project.
Hate to admit I just today discovered I've been sitting on 20 pcs of these for about 3 months
So I hate to admit it but no, I haven't heard them yet. There is a remote possibility of me doing it this weekend, but I hate to do that swap when I haven't been listening to the amps with the 820's that I'd use for the swap much.
Perhaps I'll use your previous advice and just switch one channel and see if I hear a difference. Unfortunately, I lake a "mono" option on my good system.
I also just got a demo baord for the new LM4702 which looks interesting, but given they are using single package darlingtons with not exactly what I'd call good technique... I'm somewhat disinterested. Might be better off just doing a layout for that.
Mike
classd4sure said:
Hi Chris,
Been a bit swamped with a captal S for the last few months with my paying audio project.
Hate to admit I just today discovered I've been sitting on 20 pcs of these for about 3 months
So I hate to admit it but no, I haven't heard them yet. There is a remote possibility of me doing it this weekend, but I hate to do that swap when I haven't been listening to the amps with the 820's that I'd use for the swap much.
Perhaps I'll use your previous advice and just switch one channel and see if I hear a difference. Unfortunately, I lake a "mono" option on my good system.
I also just got a demo baord for the new LM4702 which looks interesting, but given they are using single package darlingtons with not exactly what I'd call good technique... I'm somewhat disinterested. Might be better off just doing a layout for that.
Mike
proof is in the listening!
Mike,
High bias currents in reality aren’t all that bad. One just needs to equalize the input resistances it sees. When I used the 6172 and went to 2 coupling caps the total amp offset dropped from several volts down to a small few mv. Since the cost of the extra cap exceeded the cost of the opamp it really isn’t too practical but for DIY it’s a perfectly suitable path to better sound. Actually the 6172 and 2 caps are still cheaper than the AD8620 option. Higher bias currents usually mean lower noise and lower internal gain which in turn usually means less overload and slew problems as well. I personally don’t like the hard sterile sound of the 8620 and find it hard to get into the music with it. It isn’t that bad, just enough to be distracting.
Hope you get a chance to try the new chips soon. Looking forward to your report.
Roger
Mike,
High bias currents in reality aren’t all that bad. One just needs to equalize the input resistances it sees. When I used the 6172 and went to 2 coupling caps the total amp offset dropped from several volts down to a small few mv. Since the cost of the extra cap exceeded the cost of the opamp it really isn’t too practical but for DIY it’s a perfectly suitable path to better sound. Actually the 6172 and 2 caps are still cheaper than the AD8620 option. Higher bias currents usually mean lower noise and lower internal gain which in turn usually means less overload and slew problems as well. I personally don’t like the hard sterile sound of the 8620 and find it hard to get into the music with it. It isn’t that bad, just enough to be distracting.
Hope you get a chance to try the new chips soon. Looking forward to your report.
Roger
Opamp stuff.
What is this? Free samples are not free any more, National only allows an order max of 5 pieces and charged me $11.62 shipping and handling. I never had this happen before.
The only reason I did it as they look too good to not try, at least on paper. I was really amazed at some of the graphs they published and wondered how they were making those measurements. Seems as if they are using some of the amps own gain to help the measuring instrument, which was an Audio Precision 2. All in all the LM4562 looks very impressive.
Roger
What is this? Free samples are not free any more, National only allows an order max of 5 pieces and charged me $11.62 shipping and handling. I never had this happen before.
The only reason I did it as they look too good to not try, at least on paper. I was really amazed at some of the graphs they published and wondered how they were making those measurements. Seems as if they are using some of the amps own gain to help the measuring instrument, which was an Audio Precision 2. All in all the LM4562 looks very impressive.
Roger
Is it possible to remove the AD8620 opamp and replace with a socket?
I'm starting to think my initial impression of the UCD as being clean, detailed, but hard on drum attacks could be the AD8620.
My M3 headphone amp has an OPA627 and I really like it's sound.
I'm starting to think my initial impression of the UCD as being clean, detailed, but hard on drum attacks could be the AD8620.
My M3 headphone amp has an OPA627 and I really like it's sound.
You could, but I really wouldn't.
You'll end up ripping off all the solder pads and then you'll really be hurting.
opa627 is available in soic though.
I got a few to try myself. I'll be comparing them with the new ones from national.
You'll end up ripping off all the solder pads and then you'll really be hurting.
opa627 is available in soic though.
I got a few to try myself. I'll be comparing them with the new ones from national.
Hi DaveisDaveis said:
If you are going to do that, then this discrete opamp is worth a look
... Burson audio Discrete Op-amp http://www.bursonaudio.com/Burson_HDAM_Module.htm
Texture, Positioning, Soundstage, Resolution/Detail, Dynamic/Impact
Burson Discrete Op-amp
5 5 4 5 5
Burson Super Op-amp
4 4 5 4 5
AD825
3 3 3 4 4
OPA627
4 3 3 3 3
OPA2604
3 2 2 3 3
NE5532
2 1 1 2 3
hope this helps
KL
Not even SMD, looks like it could be bigger than the module itself. Did you look at the price? Probably would cost as much as the module itself.
Hi Chrisclassd4sure said:
I think thay are about A$80 to A$90 for the dual precision model.
... the 627 is single precision, so, not sure of the price for them.
... they are largish, say, 50mm x 20mm x 7.5mm(LWH) - for the single precision
Interesting through aren't they?
KL
- Status
- Not open for further replies.