Tape Saturation simulator

[PRHunt]

With some of the chatter going on about getting "vintage" sound, I did a casual search on tape saturation simulation circuits. Of course, no hardware is going to saturate exactly like tape but I found a circuit which purportedly comes close.

It looks easy and cheap to build (perhaps the germanium diodes might take a little bit of locating).

Here is the short and sweet updated 2005 article: Analog tape compression circuit

Basically, the circuit does some pre-emphasis, some soft clipping compression, and then some de-emphasis.

Here is a discussion on Gearslutz with a contribution from Tim Farrant (Buzz Audio) to improve the circuit (eg stabilize modern op-amps) and add balanced in and out. Analog Tape Compression Circuit - Gearslutz.com

I haven't built up such a device but thought I would share because it simply looks interesting and might only cost a few bucks to build. You could used stepped attenuators instead of pots to make it easier to match up a a pair for a stereo buss.

Well, over to you...

Paul

 

[kip4]

Thanks Paul
Intresting basically an op apm distortion then.
1n34s are easily available from Tayda (not affiliated)
I may well build the balanced version one day just for the heck of it and build fun.
Cheers

 

[PRHunt]

Thanks for the tip on diode availability!

I might build it too. In fact, I might use a transformer for balanced outputs - one of the $11 Edcors. Since we are clearly aiming for colour!

 

[drtechno]

yes it is similar to a diode distortion circuit, but in this application the diodes are set up as an audio envelope diode limiter.

the distortion circuit is considered a chopper as all but the junction potential is shunt to the ac grounds. that is why there is there a lot of IHD in most pedals because they try to makeup the gain from the low impedance chopper.

and I hate the plugins that simulate all the trash (imd included) as I want the guitar distorted and not all that random noise/ simulated 60hz hum and buzz.

 

[drtechno]

would anyone like to see a tube version of this?

I'll post it if you wish. otherwise, I won't.

 

[drtechno]

the saturation is one of the pieces of the puzzle. as there are many limiter circuits that will work for that application.
the second piece would be harmonic response. harmonics are lost due to over filtering and poor parts choice (Surface mount Technology) in the ADC. I'll have to make it a point somewhere so those converter people could see that the engineers needs to cut these frequencies manually instead of inserting a filtering network that veils the sound. It is easier to cut instead of boosting back. op amp choices is the last 2-5% that does make a difference sometimes.
DC reference tracking. a tape signal is symmetrical from zero crossing. digital sometimes will offset the signal but since the dc reference is corrupted, the digitally recorded signal now rides off-center but can not be fix by "remove dc offset" function.

so there is more to this for emulating the tape recording in digital.

 

[ecc83]

Been thinking? You can buy an earth isolator on'tweb for about a fiver and it contains two audio 1:1 transformers.
Now these are actually not that bad run at about a volt but it might be interesting to put them in a circuit that drives them harder ?

Dave.

 

[kip4]

I wouldnt mind a look at a tube version. thanks.

 

[drtechno]

I wouldnt mind a look at a tube version. thanks.

no problem this is my preliminary schematics. sorry I haven't draw it into a schematics program. the prototype B+ is 250V

this circuit is probably not new to quote John Brooskie (one of my favorite tube hardware engineers) "Most of the tube circuits were conceived during the first 50 years of last century."

I'm sure some chinese person will copy my design sell it on ebay like all of those half baked designs they steal off of DIY sites...…. go ahead, you'll never bake the cake like I can. so go ahead, and try to use your crappy russian tubes in this design.

to comment to ecc83,

I use a Carnhill output transformers. but I do recommend the use of transformers on the input of ADC's 1:1 and they don't have to be expensive. Black lion uses the Edcor transformers on ADC upgrades ($20ea). I think Burl uses Sowter transformers on there ADC's

 

[oli_x86]

Hi,

I know I'm really late to the party but I'm interested in this tape saturation circuit and was wondering if one of you guys ever build it and tried it?

Thanks!

Oli

 

[ecc83]

Hi,

I know I'm really late to the party but I'm interested in this tape saturation circuit and was wondering if one of you guys ever build it and tried it?

Thanks!

Bit tough to work out but then I wonder why valves? There were some very early EMI valve machines (I guess similar across The Pond?) but the vast majority of recorders were solid state. The mind boggles at the concept of "toobed" 24 tracker!

Dave.