abbey road d enfer said:
jdiamantis said:
abbey road d enfer said:
I really don't know why you attribute the 160VU's characteristics to the 208 RMS converter; have you done comparative assessments to support your theory?
The UAD site attributes, rightly IMO, the characteristics of the 160 mainly to its RMS detector, but that would also be true of other dbx products, like the 160A, which used a previous version of the 2252 chip.
It is true that the Blackmer RMS detector gives the whole family of dbx compressors a characteristic behaviour compared to other arrangements (mainly the progressive attack speed), but the 208 does not behave significantly differently than the actual 2252...
The difference is not so much in the detector, but in the timing cap and release/current resistor used. In the 160vu circuit, the detector uses a 22uf cap with a 909K timing resistor. In the 2252 data apps, the detector cap is 10uf, with a 2.0M timing resistor. While the release time scaling is identical, the difference is in the current injected into the charging transistor in the RMS module/detector vs capacity. With the larger cap and half the current used in the 208 module, attack will be slower than with the values specified in the 2252 data apps. Add to this the "non-linear" capacitor circuit, and everything beyond the 160vu is an entirely different beast.
jD
Please read what I wrote. The 2252 can be made to respond absolutely identically to the 208, which cannot be said of the discrete and monolithic VCA's.
I did read what you wrote. Did you read what I wrote? (actually, I did write in error; the timing resistor injects double the current into the 208, not half. Still, this just affects threshold, not attack time; that is determined by the charge current on the cap via the RMS module, mostly during small changes in current/level). Yes, they can respond identically. However, in my experience the dynamic character of the timing parts contributes highly to the sound of the earlier units.
The discrete VCA's, and other parts add to that character, but the dynamic feel can be reproduced with the 2252 and the 22uf cap and 909kohm resistor combination (it won't be exactly the same, due to the difference in dynamic resistance characteristics of the charging transistors in the 208 vs the 2252, but will be close). Adjustments for threshold vs input signal would have to be re-calculated with the new components to achieve similar results to the new standard parts.
To answer the parts question, on my 160 schematic, the parts in question are R35 and C15.
jD
