BJFE LGW Question ?

[analoghog]

just wondering which IC chip was used at the start of the BJFE LGW and if it has changed along the way?....thanks for your time.

[BJF]

Hi,

The LGW started out with LF 353, and later with a second option of TLC272 but as some extra chips were destroyed, LGW was supplied stock with TLC272.

There were two reasons for the option IC :
Firstly while LF 353 would be prefered for highest headroom, LF 353 also requires maintained voltage preferably not below 8V's and so a an option was sought to work down to lower voltages.

Slight complexity in distortion was also considered desirable and this the TLC 272 would provide.

After about 40 units the Value of the Body pot was changed to give smoother taper.

The MP LGW is made like the last revision of LGW and pe3rhaps the one I was most pleased with.

Thank you for your interest
BJ

[Bobby D]

with the Mp version of the LGW, is it possible to swap out other op amp chips other than the ones mentioned?

i feel like experimenting

[justonwo]

I have the same question, Slim.

[briggs]

with the Mp version of the LGW, is it possible to swap out other op amp chips other than the ones mentioned?

i feel like experimenting

If there is a socket in there go wild, I built up a LGW and tested all sorts of opamps in there. An AD712 was pleasing, as was the previously mentioned LF353.

[BJF]

Hi,

Yes the MP LGW has a socket just like the BJF version before it. MP version comes with the last revision made for LGW and has a TLC272 CMOS chip. Some prefer the LF353 that was originally put into the BJF version and the LF 353 was selected for it's high headroom and the simplicity of the internal structure that also leads to high linearity.
The LF 353 does however become fuzzy at lower voltages while at 9V's or above this is the chip I prefered as it combines several desired features like low noise, low distortion and progressive distortion ( when powersupply is high enough), high overload capability, high linearity in noninvertingmode( LF356 beats most of those requirements but has an unpleasent nonlinearity in the inputdifferentialstage)- the medium drive capability of about200 Ohms without outputstage loading distortion is taken into consideration in the circuit, and reasonably high bandwidth greatly reducing nonlinearities at high frequencies by the negative feedback,, and relatively simple internal construction gives slow onset of distortion.........

Ah but some wanted easier breakup and tolerance to lowervoltage and so the TLC272 was chosen as a substitute so LGW could be driven at lower voltages and distortion also easierly set by powersupply voltage as the TLC272 woprks as the internal bias breaks dpown....

Jaja, that's perhaps enough on LGW for now
Have fun
BJ

[mrpicard]

It is interesting that Donner likes the OPA2134. That would be interesting to try too... Once day I am going to get a few of these chips and put them into a LGW and and then maybe document the differences..

[xtoby44x]

Hi,

Yes the MP LGW has a socket just like the BJF version before it. MP version comes with the last revision made for LGW and has a TLC272 CMOS chip. Some prefer the LF353 that was originally put into the BJF version and the LF 353 was selected for it's high headroom and the simplicity of the internal structure that also leads to high linearity.
The LF 353 does however become fuzzy at lower voltages while at 9V's or above this is the chip I prefered as it combines several desired features like low noise, low distortion and progressive distortion ( when powersupply is high enough), high overload capability, high linearity in noninvertingmode( LF356 beats most of those requirements but has an unpleasent nonlinearity in the inputdifferentialstage)- the medium drive capability of about200 Ohms without outputstage loading distortion is taken into consideration in the circuit, and reasonably high bandwidth greatly reducing nonlinearities at high frequencies by the negative feedback,, and relatively simple internal construction gives slow onset of distortion.........

Ah but some wanted easier breakup and tolerance to lowervoltage and so the TLC272 was chosen as a substitute so LGW could be driven at lower voltages and distortion also easierly set by powersupply voltage as the TLC272 woprks as the internal bias breaks dpown....

Jaja, that's perhaps enough on LGW for now
Have fun
BJ

might be a stupid question but I have been looking into acquiring a LF 353 for my LGW to experiment on my own with and is there a difference in the op amps
LF 353
LF 353N (one I ordered)
and so forth(different Letters) is there a preference BJ had in the beginning or will any 353 fit the spot?

[BJF]

Hi,

LF353N would do nicely
Suffixes denotes special versions or packages. Suffix N means a 8-pin minidip standard package if National Semiconductor- other manufacturer's can have other suffixes for same packages.

8-pin minidip would be implied in the construction- my error I should have addressed that .
Do to varying suffixes plain LF353 would to a technician mean 8-pin minidip by standard.

Here's a part datsheet for LF 353 from National:

http://pdf1.alldatasheet.net/datasheet- ... F353N.html


Further note:
The internal structure of LF 353 is uncritical and actually somewhat crude compared to some other popular dual OP's. Of interest for the circuit is the distortion behaviour in overload condition as somewhat touched upon in above file-that coupled with the lownoise construction at medium impedances........for signal levels greater than peaks of 2V's J-Fet input OP amps show less distortion than comparable bipolar units...this being a consideration in the circuit.
Differences of varying makes of LF353 would be minimal in the circuit due to the construction.

Finding an LF353 (N) should be uncritical as it is a standard dual OP.


Have fun
BJ

[xtoby44x]

Hi,

LF353N would do nicely
Suffixes denotes special versions or packages. Suffix N means a 8-pin minidip standard package if National Semiconductor- other manufacturer's can have other suffixes for same packages.

8-pin minidip would be implied in the construction- my error I should have addressed that .
Do to varying suffixes plain LF353 would to a technician mean 8-pin minidip by standard.

Here's a part datsheet for LF 353 from National:

http://pdf1.alldatasheet.net/datasheet- ... F353N.html


Further note:
The internal structure of LF 353 is uncritical and actually somewhat crude compared to some other popular dual OP's. Of interest for the circuit is the distortion behaviour in overload condition as somewhat touched upon in above file-that coupled with the lownoise construction at medium impedances........for signal levels greater than peaks of 2V's J-Fet input OP amps show less distortion than comparable bipolar units...this being a consideration in the circuit.
Differences of varying makes of LF353 would be minimal in the circuit due to the construction.

Finding an LF353 (N) should be uncritical as it is a standard dual OP.


Have fun
BJ

BJ,

thank you for taking the time to help. I greatly appreciate it.