Symetrix se400 dual parametric equalizer schematic

[nevetslab]

So would the TL072 be an improvement over the LF353?

Or which ones do you recommend that can outperform these models in terms of quality and really make a beneficial difference?

I have tried to research, but it is very difficult to find information about Symetrix or users sharing his modifications and upgrades.... acutually I feel lucky to find you!

I've attached data sheets for the LF353, TL072-TL074 series, TLE207x series JFET Op Amps. There should be chatter on some forums about these parts. Linear Technology also has some very decent parts as substitution/upgrades over the LF 353.

LF353.pdf
TL071-074.pdf
TLE207x Series JFET Op Amps.pdf
LT1113 Dual LN JFET.pdf

[Nordlead26]

I've attached data sheets for the LF353, TL072-TL074 series, TLE207x series JFET Op Amps. There should be chatter on some forums about these parts. Linear Technology also has some very decent parts as substitution/upgrades over the LF 353.

[ATTACH]n934347[/ATTACH]
[ATTACH]n934348[/ATTACH]
[ATTACH]n934349[/ATTACH]
[ATTACH]n934350[/ATTACH]

Thank you for your response,

I found this other brand los: MUSES02

https://www.njr.com/MUSES/series/MUSES02.html

They seem to have good reviews. Any experience with them?

I wanted to ask you something important, the Opamps in Symetrix, do they come soldered or in plugged?

[nevetslab]

I wanted to ask you something important, the Opamps in Symetrix, do they come soldered or in plugged?

I can't speak for all of them, but in the SE400 I have they were all socketed. I'll have to look at my photos on other Symetrix products to see if those were the same.

[nevetslab]

I was thinking of replacing the potentiometers with detent potentiometers, could you help me to verify how many Ohms they are, or what specs they should have to be 100% compatible with this unit? I will take these parts to a specialized technician, however I would like to know such details to buy the pieces

are this ones compatible?

https://www.mouser.mx/ProductDetail/...pB8X1YQw%3D%3D

Thank you!

Sorry for the long delay on the questions posed here. I just got thru with restoring the Vox Beatle Super Reverb, and now having to pack up my 'temporary shop' at CenterStaging's Rental Inventory warehouse to move back to the smaller shop space I've been in since 2009.

On the Alps RK16 Pot series, the best fit mechanically is a 7mm bushing/12mm Single-D shaft PCB terminals. The lead spacing and distance from the mounting surface is the same as is used on the Symetrix pots....same 5mm pitch between terminals, and on the dual gang pot,5mm pitch between the front and rear decks, same bushing/shaft details. Now as to the location of the flatted shaft relative to CCW or CW position, it is the same as shown (they list the flat as 60 deg to the left from 12 o'clock at full CCW position. So, identical there. The difference between what Symetrix used and the Alps RK16 series pots is the overall combined length of the threaded bushing and single-D shaft. These pots Symetrix used is 18mm. Alps offers either 15mm (5mm bushing, 7mm shaft) or 20mm (7mm bushing, 12mm shaft). If you have the option, choose 20mm overall. Then you have full compatibility with the push-on knobs Symetrix selected.

[Prometheus]

Hi nevetslab,
Impressive schematic diagram you produced for your SE-400!
Attached is some documentation I found that might be helpful.

I have modified the circuitry in several SE-400s to meet specific studio requirements - the modular circuit boards lend themselves to easy modification.
The TL072 and LF353 were very similar - LF353 was National Semiconductor's cheaper answer to TI's TL072, albeit a little different but still amongst the first opamps with JFET input stage and the advantages that brings when minimizing circuit loading. The TL072 was pretty unique back in the 1980's with a 30-V supply range, BW of up to 3-MHz, a decent slew rate of up to 13-V/µs, and JFET-input stage with a 200 pA or less input current ability. These are useful for filter networks to avoid unwanted circuit loading and the opamp's characteristics loading your circuit and changing the wanted operating behavior.

While the TL072CP and the LF353CN are still available from TI, the "modern day" equivalent to the TL072CP could be considered the TLE2072A Dual, 38-V, 10-MHz, 40-V/μs slew rate, 2-mV offset voltage and importantly a JFET-input op amp. If you want go off and try something else, there are a couple of things to keep in mind with opamps for filter circuits - input currents, slew rate and Gain BW, output current swing ability and finally open loop gain characteristics.
Do keep in mind that the TL072 had an annoying 128 ohm resistor in series with the output stage that can play havoc with your circuit design if you chose to use low value resistors around the circuit e.g. 1k range and large capacitors > 50nF. This resistance is still there with the TLE2072 but I think it is around 80 ohms. It should not be a problem with SE400.

[mwp9]

I’ve had an se400 for a little over a year and want to do these mods. I’m glad this site came back online so I could see the data. I’m good with a soldering iron, but bad at reading a schematic. Would anyone have a list of parts to purchase/replace?