Anyone taste-test the TL070 vs LM308 in the Rat?

[Toney]

Gonna do a rat.
By "do" I mean build, as opposed to.............................never mind
I know this is a hoary old chestnut ( whorey=different ask my ex ),
but I want to know if anyone has actually A/Bed an LM308 with a TL070 compensated for a low slew rate in this circuit.
308s have been bagged before as horrid hissy wastes -of- time (you should meet my sister's stylist)     
  buuuut...... I want to know if there is more to the Rat magic than just the "anemic" slew rate of the 308.
So, anyone given them both a work out?







         Sorry been watching old British sit-coms........"Are you free Mr Humphries"................................."Aim free"

[Phorhas]

I've dropped both NE5534 (thanks for the tip, Jack) and TL071.

To my taste, the TL071 hits the spot. Quiter and sound way better over all.
The NE5534 was apperantly too good - it had more high end and a bitier tone. I recon that's due to the better load handeling charecteristics of the NE5534 over the TL071.

But, as with all things here - try'em both and decide

[Geoff Hunter]

I built a TL070 rat just last weekend to go along with my 3 other rat variants.

I A/B them just now with an old LED rat2 (got a non-led rat2 as well but doesn't sound much different TBH, just slightly less high end.)

I would say it sounds 95% the same*.  Its hard for me to say if its quieter as my soldiering/wiring skills aren't that great.

I can't swap chips and test as i used a different compensation cap (do a search for TL070 and you'll find some values.  I used 150pF for mine), and once i've boxed something up, i'm loathe to open and tweak again!

On other rat builds I found the NE5534? to have a nice tone, but too much treble.  A 741 has not enough treble for me!

I would say give it a try, you do get that RAT sound with a TL070!


* I'm running it through this: http://www.marshallamps.com/product.asp?productCode=MS-2%20and%20MS-4

[MartyMart]

My "Old faithfull" RAT has a 308 ( tried NE5534 .... YUK ! )
It has all of Jacks mods from his "Rat/Muff" E book too,  V- nice !
The one I DIY'd has a TL070 in it right now ( I have 308's around too)
.... seems very similar to me.
I did the "assymetrical" diode mod to both, 1X1N4148 by 2X1N34A ... So only
slight assym !!

..... You gotta LOVE a rat !!
MM.

[smank]

>> I did the "assymetrical" diode mod to both, 1X1N4148 by 2X1N34A ... So only slight assym !!
I use on my RAT the same diodes combination.

Instead of LM308, I use a TL061 op-amp: it's internally compensated, but it as a smaller slew rate compared with the TL071.
I don't like too much the LM308 sound (it's just my taste... or not?). I don't like absolutely the NE5534: it's too modern/HI-FI sound.

I've changed the external capacitor to 150pF instead original 100pF.
In the tone control I've changed the resistor in series with pot to 2,2K.
The partition to obtain Vb is from 2 10K resistors + 47uF cap.
Last mod: I've reduced (!!!) the input resistance to 220K (and consequently increased the input cap to 100nF). In this way there s a small charge of pickups, so the sound it's a little smoother.
In this way my RAT is fantastic: good sound with single coils and humbuckings. Smooth highs and great attack.

[Toney]

Hey, thanks guys- thats perfect.

I'll go with the 070 then.
The  LM308 is too much bother to find anyhow