I made a simple to the book line amp of 4562.It sounds very good, from bottom to top
but it can't be used with an attenuator.There is a cracking for every snap and my power amp shuts down.IOt works ok with a pot though. Offset it .3 mv on one channel and 3 mv on the other.
I think there's bipolar transistors as input as fets would give no offset.Thats also why the attenuator makes noice although it's a make befor break
but it can't be used with an attenuator.There is a cracking for every snap and my power amp shuts down.IOt works ok with a pot though. Offset it .3 mv on one channel and 3 mv on the other.
I think there's bipolar transistors as input as fets would give no offset.Thats also why the attenuator makes noice although it's a make befor break
It sounds like your attenuator has a break-before-make switch. No opamp really likes to run with input(s) open, even the JFET and MOSFET input types need some sort of impedance to common. The 4562 is a bipolar input amp, and would like to have a dedicated resistor to ground on the input where the attenuator is connected. This is just a guess at this point, but 100k or so to ground would probably keep the opamp from going totally berserk when the attenuator switches. What you need to do at this point is to calculate the voltage step that occurs when the attenuator wiper is between contacts and the only path to ground is the fixed resistor. Use the bias current specs for the opamp to calculate the voltage step and choose a resistor value accordingly.
SimontY said:
I don't mean to step on anyone's toes or discount their findings, but I have found the OPA627P to sound much better than the LME49710(4562 single package equivalent).
I'm sure it depends on the circuit but IMHO the OPA627P stomps the LM4562.
I find the 4562 thin sounding, lacking bass and not as "present" as the OPA627P. The 627 has twice the output current capacity and equivalent CMRR and PSRR. Not only that, but I can null out any dc offset to zero.
Just my opinion though.
hags said:
I'm sure my preferences are somewhat tied to the overall character of my system. 627bp are still certainly a good op-amp, and my 2nd favourite. I hear plenty of bass from the 4562, but it's much better controlled. Neither is ideal though, but interestingly the one which sounds closer to a discrete equivalent is by far the 4562 (in output stage of Marantz CD63).
I do agree about the thin sound though, that *could* be a problem in some cases.
Simon
I think everyone needs to try a range of op-amps so that they may find one that suits their needs.
In the Marantz CD63 the OPA627 has warmth and sweetness and plenty of extended bass, but misses detail and accuracy.
OPA2134/2 is a lot like 627 but with a less inviting sound.
The LM4562 excells at detail retrieval and accurate bass, but seems to lose some of that warmth and, oftentimes, engagement with the music.
A discrete stage offers all of the formers sweetness, the latters accuracy and detail, and with a bass quality far superior to either. I don't think anyone wanting perfection should look at op-amps. They're just good because they're easy and cheap.
Simon
In the Marantz CD63 the OPA627 has warmth and sweetness and plenty of extended bass, but misses detail and accuracy.
OPA2134/2 is a lot like 627 but with a less inviting sound.
The LM4562 excells at detail retrieval and accurate bass, but seems to lose some of that warmth and, oftentimes, engagement with the music.
A discrete stage offers all of the formers sweetness, the latters accuracy and detail, and with a bass quality far superior to either. I don't think anyone wanting perfection should look at op-amps. They're just good because they're easy and cheap.
Simon
SimontY said:
I think the higher quality op amps get you most of the way there. I think that they are highly dependant upon the circuit they are utilized in.
I have used the LME49710 to replace the seven pin antique op amps in a couple of Kenwood KT-815 tuners. The results have been spectacular. Solid bass, excellent low level detail, clear and pleasent highs.
When I have experimented with them as line drivers they do leave a little to be desired though.
Exact. I think is a matter of balancing or contre-balancing the effects of the several parts of the chain (including cables).
For instance, my two DACs:
1) M-Audio superDAC: AK4393 + OPA627= detailed yet powerfull sound; AK4393 alone is detailed but lacks punch and sounds light in the middle.
I guess AK4393 DAC and the like will put out light sound paired with LM4562, as it is closer to "no opamp".
2) DI16 (one of -ecdesigns-'s Ultimate NOS DACs): TDA1543 + LM4562= detailed but colorful and meaty sound, live-like.
My two pesos ...
M
I agree with Andrew T - a series resistor will not work. I suggested a shunt resisistor to ground, so that there is always a path for bias current. Given the things that can happen (as evidenced by this event), a shunt resistor to ground sounds like a good safety measure whether you're using a switched attenuator or a pot (wipers can lift, too). The 4562 has much lower bias current than earlier comparable opamps, but it's stiil very much there and needs a path to return for the opamp to function properly. I'm using a law-faked pot for volume control, so the safety resistor is already in place.
hags said:
I'll have to try the OPA627. I just built a MC pre-amp with the LME49710 and have been wrestling with my opinion of it. My take is that while extremely good at the more prominent (louder) end of the spectrum it 's missing alot of the subtler details, I keep wanting to turn it up to get it to clearup... I guess this could be contrued as thin, but it sounds actually quite clean and I guess low in distortion otherwise. There is definitely a missing fullness and subtle ambience. The offset null would be nice as I'm not using a servo and one channel has 56mv, the other 110 mv.
Just my two cents. Mike
MikeBettinger said:
Wow, that amount of dc offset seems high. The max dc offset listed for the LME49710 is 0.7mv or 700uv, I do not know the circuit you're using it in but that doesn't sound right.
The dc offset null on the OPA627P is really nice, it enables me to direct couple the circuit and I don't have to use any coupling caps at all.
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