Chip phono preamp

[Paul Ebert]

I'm looking for inexpensive, but good, DIY moving coil phono preamp. I'm familiar with the phono clone, but it seems that the OP27 is obsolete. Are there other designs or is it possible to update the phono clone to current opamps - perhaps the LM4562 since I have a few?

Thanks!

[AndrewT]

is the 627 a near equivalent to the 27?

The thread surely gives modern opamp substitutions.

[Paul Ebert]

Do you mean the phono clone & vsps 'help desk' thread? I noticed that after posting here.

I'll probably do so, but I'm quite intimidated by a 100+ page thread. I'll probably read it backwards.

Thanks for the reply. I'll check out the 627.

[Juergen Knoop]

Hi,
OP27 from Analog Devices and OPA27 from TI are still active.
Regards
Jürgen

[peranders]

OPA637 is slightly better in a high gain application such as a phono amp.

[peranders]

Originally posted by AndrewT
is the 627 a near equivalent to the 27?

The thread surely gives modern opamp substitutions.

If you compare datasheets, these devices are quite different.

[nelsonvandal]

LM4562 is low-noise, and in spite of having bipolar inputs has low bias current. It sounds qite good with a very clean treble and nice bass. Compared to FET-input opamps, it's a bit cold or sterile and give the impression of having a recessed mid. I don't know what gain there is in this RIAA stage, but DC-offset could be a bit higher than with OPA627. Since there's no volume control in front of the RIAA stage, bias current can be balanced. I can't see why you shouldn't try LM4562 since you already have them, and since OPA627 is very expensive and hard to get and soon there will be OPA827 available.

[Paul Ebert]

I've found a few vendors that indicate stock of the OPA627, but they average around $38. Yeah, that's too expensive for me.

How about the OPA227? Would that work?

Oh, and when do they expect to have the 827 available?

Thanks.

[Nordic]

opa 227 is a diffirent beast alltogether... pretty hard to stabalise and will sound thin and uninvolveing if all is not 100%...

give those 827's a chance...

[nelsonvandal]

Originally posted by Paul Ebert
Oh, and when do they expect to have the 827 available?

I don't know, but some claim they've already got samples.

Give LM4562 a shot. If you want a warmer tonality - use OPA2134 (cheap, easy to find) for one stage and LM4562 for the other. Toghethter they'll give a warmer than neutral tonality (at least they do in my headphone amp). LM4562 can be a bit cranky, but just use decoupling caps in close proximity and have a good shield and ground. LM4562 is very prone to pick up radio interference.

The most neutral match for LM4562 I've found is LMH6654, but that amp has very high bias currents and the max voltage supply is +/- 6.