BassBost Circuit?

[Emon]

He said he was going to use it with this amp...

 

[rickcr42]

there is another way though a bit of wrangling (parts/formula) is required and that is the peaking coil or inductor which makes a true boost and is totally passive.All older equalizers and tone controls used the "gyrator" as a boost mechanism which later was replaced by the "artificial gyrator" active stage made from an opamp.

Do a search on "pultec equalizer" for ciruit ideas

 

[tangent]

Quote:

Originally Posted by rickcr42 a true boost and is totally passive

I did some Googling and none of the circuits I found have any way of boosting the signal passively. They are all followed by a tube stage to restore the gain to make up for the losses through the passive stage.

I'm glad this is the case, because otherwise I'd question my understanding of basic physics: you can't get more energy out of a circuit than you put in.

For those who still want to build one (it probably performs a lot better than the two-part piece I alluded to), here are the two most useful links I found. They seem to be the same circuit, just different discussions and such:

http://members.carol.net/~zt.robgrow.../pulteceq.html
http://www.gyraf.dk/gy_pd/pultec/pultec.htm

If you continue Googling, there are others that have built solid-state output stages for the same basic circuit.

 

[rickcr42]

Quote:

I'm glad this is the case, because otherwise I'd question my understanding of basic physics: you can't get more energy out of a circuit than you put in.

well you better start questioning then.An LCR circuit can have true boost and the active stages are there to buffer/restore gain at the output of the filter circuits which are reactive but the actual FUNCTIONAL BOOST is totally passive .Any headphone amp satifies the buffering/gain requirementr by having the filter see a hi Z but even that can be totally passive AND have gain if a 1:4 transformer is used.NO acive devices,gain and impedance matching and all in a single device.

Hundreds of studio equalizer ciruits are totally passive as far as the actual eq bands are concerned and while all passive has losses it still has boost in the selected band in relation to the other non boosted bands

one well known example of the passive Eq is here but it is only the most recent use of passive EQ and many plansd are available.
An opamp "synthersized" gyratror circuit is no more than a SS replacement (read CHEAP rep[lacement not better) for a true inductor based gyrator

I'm glad this is the case, because otherwise I'd question my understanding of basic physics: you can't get more energy out of a circuit than you put in.

 

[rickcr42]

http://www.manleylabs.com/PDF/PRO_Ma...C%20manual.pdf

 

[drewd]

I'm familiar with the Pultec equalizers. You can look at a schematic of one and see that the the amplifier uses RC and RLC circuits as low pass and high pass filters with different corner frequencies. An active gain stage has to follow in order to compensate for the gain loss from the filters, assuming that you want something approaching the same signal level going out as you had coming in. In the Pultec equalizers, the gain is from a tube amplifier.

So, yes, looking solely at the output of the equalizer circuit, some frequencies may be boosted in relation to each other, but the overall signal level is cut in relation to the original input. At some point, there has to be an active circuit - before the equalizer or after it.

Also, perhaps I misunderstood one of your posts, but as far as I know, all gyrators are active - whether it's a tube, transistor or opamp. If a gyrator is a circuit that uses capacitors and an active element to behave like an inductor - an inductor-based gyrator seems redundant.

-Drew

 

[rickcr42]

Quote:

An active gain stage has to follow in order to compensate for the gain loss from the filters, assuming that you want something approaching the same signal level going out as you had coming in. In the Pultec equalizers, the gain is from a tube amplifier.

Wrong answer.If all bands are boosted the output "amp" is used to attenuate,as a negative gain stage and not for additional gain

A Quote:

t some point, there has to be an active circuit - before the equalizer or after it.

not true either.the ideal is to follow the eq sections with a stable impedence but that can be accomplished bu the folloing stage,in this case the headphone amp.

Quote:

Also, perhaps I misunderstood one of your posts, but as far as I know, all gyrators are active - whether it's a tube, transistor or opamp.

wrong again.the opamp used in an active gyratore circuit is a direct replacement for the inductor and that is why any opamp gyrator is called a synthesized gyrator ciruit.The gain of the opamp is used in place of a peaking coil which is a resanant tuned frequency curiut that provides TRUE pssive frequency boosting.

guys,you need to do some research.

Not only have I used passive boost circuits but have them in system right now so i know if I am getting a bass bosst or not.

A bit more (and beleive me when I tell you I have MUCH more info but will not post it due to some of it being copyrighted) :

http://www.sowter.co.uk/acatalog/SOW...FORMERS_6.html

http://www.jims-sae-site.com/cham_gold_mark/gp1e.jpg


http://www.jims-sae-site.com/cham_gold_mark/gp1e.jpg

http://recforums.prosoundweb.com/in...://hfimage.head-fi.org/smilies/cool.gif[/img]

 

[rickcr42]

Obviously there is an error in the above post (long day yesterday

).

the corrected version is :

"The Gyrator curcuit is a synthesized inductor"

That is a cheap replacement for the expensive coils used for LCR EQ networks in the same manner the InAmp is an attempt to reduce the cost of the balancing amp.New is not always better but a lot of times a cost saving measure just like LSI (Large Scale Integration) is smaller and cheaper to implement (like the el cheapo DVD players) but in no way could be considered as good or better than discrete building blocks.that is the reason most first generation CDPs,VCRs,DVDPs where built like a trank and weighed a ton pus were vERY expensive.
One the LSI chips were tooled up the price and weight wnet down,the features increased but the perormance was not bettered and in most cases lessened.