Topping D90LE - "Valve" and "Transistor" effects measurements

[restorer-john]

To add a basically but not utterly irrelevant aside, if I may:

Long, long ago, there was a flurry of "sub-bass synthesizer" products (all analog, AFAIK) that did the same thing, but in the other direction (i.e., added some signal at half the fundamental frequency).

View attachment 214612source: https://worldradiohistory.com/Archive-All-Audio/Archive-High-Fidelity/70s/High-Fidelity-1978-09.pdf

This one may have just been a tone control, though, for all I know.

View attachment 214613
source: https://www.radioshackcatalogs.com/flipbook/1983_radioshack_catalog.html?fb3d-page=92

N.B. Note that I didn't say these products worked well.

The Realistic Bass enhancer is a great little product. The only real issue with it is residual noise. It's basically a parametric EQ with a very good subsonic filter, so good for both vinyl and small speakers.

It was an add-on sold with Minimus 7 and other small speakers for years.

I've got one here and ran some FR plots on it a while back if anyone is interested in seeing what it does.

 

[mhardy6647]

I've got one here and ran some FR plots on it a while back if anyone is interested in seeing what it does.

Well... I mean... I would be
Not sure anyone else'd care, though... but if you feel like starting a little thread sometime, I'll read it!

 

[restorer-john]

Well... I mean... I would be
Not sure anyone else'd care, though... but if you feel like starting a little thread sometime, I'll read it!

Here you go. A few combinations with equal 'db' and 'freq' increments to show the parametric effect.

Bypass (purple) vs in circuit (yellow), no boost. Vertical scale in Volts. Notice the inbuilt low filter- brilliant for small speakers and possible vinyl sources.

 

[mhardy6647]

Reminds me of a plot of Qtc vs. frequency response!
Which I actually mean as a positive statement.
Thanks for sharing those traces!

source: https://www.diyaudio.com/community/threads/increase-bass-in-closed-box.317182/

 

[fpitas]

Reminds me of a plot of Qtc vs. frequency response!
Which I actually mean as a positive statement.
Thanks for sharing those traces!

View attachment 261725
source: https://www.diyaudio.com/community/threads/increase-bass-in-closed-box.317182/

The valve simulating DACs need variable output impedance!

 

[mhardy6647]

The valve simulating DACs need variable output impedance!

... or at least fairly high output impedance.

 

[fpitas]

... or at least fairly high output impedance.

If it's tweakable, people will spend happy hours introducing more or less boominess. Who am I to criticize?

 

[NormB]

I always thought it would be a cool product idea for someone to release a custom distortion generator. Ideally digital in and out so it could be placed in-line before your DAC but analog could also work.

Something that lets you dial in specific 2nd, 3rd, 4th, 5th, etc order distortion just to play with how it effects sound.

Well, there‘s this:

Gramophone Dreams #26: Nelson Pass & Harmonic Distortion

Every time I fly to California, my brain gets stuck on the lyrics of that Arlo Guthrie song: "Coming into Los Angeles / bringing in a couple of keys . . ." Even landing in San Francisco, I'm always smiling, because I've never been busted in California.

www.stereophile.com

 

[fpitas]

Well, there‘s this:

Gramophone Dreams #26: Nelson Pass & Harmonic Distortion

Every time I fly to California, my brain gets stuck on the lyrics of that Arlo Guthrie song: "Coming into Los Angeles / bringing in a couple of keys . . ." Even landing in San Francisco, I'm always smiling, because I've never been busted in California.

www.stereophile.com

https://www.firstwatt.com/pdf/art_h2_v1.pdf