Hughes&Kettner RED BOX CLASSIC

[cg]

DOSE ANYONE HAVE THE SCHEMATIC OF Hughes&Kettner RED BOX CLASSIC?I AM A NEW GUY FROM CHINA.THANK U

[alteredsounds]

Wonder y the schem is needed...............

[cg]

JUST BECAUSE I WANT DIY ID BOX WITH A 4*12 SPEAKER SIMULATER.I HAVE TRY SOME MARSHALL SPEAKER SIMULATER BUT I DONOT LIKE THE SOUND.SO I NEED A NEW SCHEMISTIC.CAN ANYONE GIVE ME IT ?

[George Giblet]

Here's some cabinet sims which includes the redbox2:

http://www.herby.kielce.pl/~piter/konstr/cabsims/schem/

Note it uses inductors which makes it inconvenient to build.

There's also some cabinet sims/amp sims at the 'run off groove' site:

http://www.runoffgroove.com/articles.html

For example,

http://www.runoffgroove.com/condor.html

As I recall, the last three filter stages are pretty close to the redbox and some of the other sim circuits (including stuff I've done myself).

(I think there's a name for restricting information based on country of origin......)

[alteredsounds]

Yes there is and that wasnt my intention with my remark but some more initial information wouldnt have aroused my suspicions.

[cg]

THANKS GEORGE.I MADE A MARSHALL JMP1 SIM FEW MONTHS AGO WITH 9V DV(+/-4.5VMADE BY TWO 10K RESISTANCES WHICH IS USUALLY USED IN EFFECT PEDAL)BUT I FOUND THE SOUND A LITTLE DISTORSION EITHER USE GUITAR OR DISTORSION PEDAL THROUGH THE JMP1 SIM .I ALSO FOUND IN http://www.herby.kielce.pl/~piter/konstr/cabsims/schem/     MANY SCHEM NEED AT LEST 24V DC(+/-12V),HOW CAN THESE SCHEM WORK IN 9V DC(+/-4.5V)SITUATION??

[George Giblet]

Look at how the condor biases the opamps with the Vref network (2 Resistors and a Capacitor to Ground).  This is the method 9V effects use.   It will work on most sim circuits.

For your JMP1 try removing C3 and C4, shorting R2.   Parts refer to this schematic:

http://www.herby.kielce.pl/~piter/konstr/cabsims/schem/JMP1-cabsim.GIF

[MetalGuy]

For more highs short R10 and remove C10.



Orange line - stock JMP-1 cabsim
Blue - JMP-1 cabsim with the mod above
Green - 2x12"  Celestion G12L50 sealed cabinet, Shure SM-57, on axis
Yellow - 2x12"  Celestion G12L50 sealed cabinet, Shure SM-57, 45deg off axis /cone edge/

Note it uses inductors which makes it inconvenient to build.

It's not that inconvenient - such inductors are readily available from Mouser, Digikey and others. Here's how it looks:




So far I like Marshall's cabsim found in the Schematics section the most:

http://www.diystompboxes.com/pedals/schems/msim.jpg

If only someone could explain me what / which frequencies/ that weird filter between the first two opamp section does?

[cd]

You're not still using one of those WebTV boxes, are you?  BECAUSE WHEN YOU TYPE IN ALL CAPS IT SOUNDS LIKE YOU'RE YELLING.  NO NEED WE CAN ALL UNDERSTAND WHAT YOU'RE SAYING.

[Gilles C]

I have this model



that they replaced by the Pro.

Gilles

[George Giblet]

> It's not that inconvenient - such inductors
Sure.

There's a larger valued inductor in the redbox pro.  I can't see it on your PCB, did you use one?

>Green - 2x12"  Celestion G12L50 sealed cabinet, Shure SM-57, on axis etc

Did you measure the speaker responses with a tube amplifier connected to the speaker or a test amplifier?

One of the problems with these speaker sims is with a tube amp the speaker and amp interract.  If you want to emulate reality you have to specify what reality is.  There are many possible configurations but supposing we assume the signal is at least processed by a guitar amp  (ie. we aren't doing an amp+speaker sim) then there's these:

1) Amp Line-out -> Speaker Sim -> Recording Desk
2) Amp Speaker-Out with Speaker Connect to Amp -> Speaker Sim -> Recording Desk
3) Amp Speaker-Out with Dummy load Connected to Amp -> Speaker Sim -> Recording Desk
    Here there's also variation of the theme because the Dummy load can be a resistive dummy load or a speaker load simulator.
    If it's a speaker load simulator the speaker sim needs to be more like (2) whereas if it's resistive the speaker sim
    needs to be more like (1).

So there's sort of two basic EQ requirements.   The redbox pro tries to cope with these two cases with the speaker through and line-out options. With the majority of speakers sims it's largely unspecified what the intended configuration is/was - the result is people just say one doesn't sound as good as another.  The Marshall sims tend to align with case (1).

>If only someone could explain me what / which frequencies/ that weird filter between the first two opamp section does?

It's a bass boost/treble boost to simulate the effect of the amp and speaker interraction.

[DuncanM]

Deleted post.

[cg]

FIRST:MARSHLL JMP1 SIM
SECOND:MOD REPLACE R2 WITH 30K
I DON THINK AFTER MODED THIS CIRCUIT CAN WORK WELL AS ORIGIN AND YOU CAN SEE FROM PICTURES.
THANKS GUYS.I DON KNOW ALOT ABOUT ELECTRIC,IF YOU HAVE ANY SUGGESTION,HELP ME!

[MetalGuy]

Thanks for the remarks.

The Redbox MKII posted by Gilles C. looks like the one from H&K Metal Master or Cream Machine.

There's a larger valued inductor in the redbox pro

The Redbox I built is the same from Tubeman which  is almost the same /at least the passive part/ as in RedboxPro MKIV less the inductor you mention and the output transformer. As far as I can see from the schematic that inductor enters in action only in Speaker mode.



My recording setup:

Sound card: Creative Audigy 2 ZS with testing software flattened frequency response.

Cabinet testing setup:
Pink Noise generated by testing software - FX In of 2xEL84 amp - 2x12" Celestion G12L50 sealed cabinet - Shure SM-57 - PC Soundcard Line In - Testing software

Cabsim testing setup:
Pink Noise generated by testing software - Cabsim In - Cabsim Out - PC Soundcard Line In - Testing software

I like the things simple: it's either a guitar amp and cabinet miked going to mixer/recording desk or a guitar preamp/FX and cab/ampsim going to mixer/recording desk. So  it's either going to be a real situation or a real imitation the ideal case being  when the cabsim produces the same or at least the closest sound of the real situation.

It's a bass boost/treble boost to simulate the effect of the amp and speaker interraction.

Can you be more specific exactly which frequencies are boosted/cut and how the filters are organized? 

[George Giblet]

I was just about to post but I found a mistake.  Please bear with me, I can explain most of what you are asking - it's late here!

[George Giblet]

> The Redbox MKII posted by Gilles C. looks like the one from H&K Metal Master or Cream Machine.

Yes.  I noticed that too.

>The Redbox I built is the same from Tubeman which  is almost the same /at least the passive part/ as in RedboxPro MKIV l

I haven't seen the RedBox I before - so that's the schematic (thanks!). I have seen the tubeman though and I actually thought it was an inductorless version of the Redbox Pro - not seeing the Redbox I, I've got the chronology wrong.

The RedBox IV does perform a little differently to the Redbox I and the Redbox II is different again - all in a similar ball park though.

> My recording setup:

Very cool.

Interestingly the Redbox I and Redbox IV do try to emulate the notch at around 8kHz and the peak above that.  These features show-up on your measurements (although your frequencies are a little different).

> Can you be more specific exactly which frequencies are boosted/cut

Here's a plot of the first two stages of the Marshall JMP-1 and JMT sims:

http://www.geocities.com/george_giblet/effects/marshall_sim_boost.png

> and how the filters are organized? 

I'm not sure what you want to know precisely here but the first two stages are as follows:

The JMP-1 provides a bandpass boost at low frequencies, using a gyrator, and a shelving high-boost using an RC circuit  - it's basically a two-band equalizer like that used for graphic Equalizers.  The second stage of the JMP-1 is a 2nd order high-pass filter to emulate the low-frequency roll-off of the speaker.  This is a straight forward filter in that you can see what part is doing what relatively clearly and in isolation.

The JTM filter is harder to understand since it's not a textbook filter.  The filter
is a compounded filter which approximate ideal filters.   The 4.7k+68nF+100nF+100k network forms a well know inverting band-pass filter (Delyannis circuit).  The frequency is around 98Hz and gives the bass peak.  The 47k resistor decouples this network to form an inverting mixer so the HF boost circuit can be added in.  The 33k+3.3nF work in combination with the 47k resistor to form a high frequency boost shelf circuit.  Roughly the band-pass and high-frequency shelf are added together.   The 47nF cap and 27k input resistor give more LF roll-off to simulate the speaker's roll-off - the band-pass filter alone doesn't provide a high enough slope on the LF. The other parts are largely tweaks.  So while the filter looks complicated, which is it, it can be teased appart.

One thing I noticed about your graphs.  If you lifted the gain of the sim curve a few dB so that the low-frequencies matched, the curves would match very well upto about 400Hz.   In addition added boost would then make the sim match the speaker in the high frequency region better (it can't put the notches in of course).  When you do this the match around and above 500Hz get poorer.  This suggests rather than modify the high frequencies it would be wise to increase the starting point of the shelf circuit which comes in around 500Hz-700Hz.  That could be done by decreasing the 3.3nF cap on the JTM circuit to 2.7nF.

[George Giblet]

>SECOND:MOD REPLACE R2 WITH 30K

Which set-up are you using (1), (2), or (3)?

1) Amp Line-out -> Speaker Sim -> Recording Desk
2) Amp Speaker-Out with Speaker Connect to Amp -> Speaker Sim -> Recording Desk
3) Amp Speaker-Out with Dummy load Connected to Amp -> Speaker Sim -> Recording Desk
    Here there's also variation of the theme because the Dummy load can be a resistive dummy load or a speaker load simulator.
    If it's a speaker load simulator the speaker sim needs to be more like (2) whereas if it's resistive the speaker sim
    needs to be more like (1).

Earlier you mentioned the sound was too distorted.  I thought perhaps you were getting too much high frequency boost.  The suggested mod, or your mod, (eg pull caps or decrease R2) will decrease some of the buzz. 

By the way, your simulations don't look quite right although it's hard to tell without measuring cursor point off the simulation display.

[MetalGuy]

The JTM filter is harder to understand since it's not a textbook filter

That's the filter /between the first two opamp stages/ I was talking about. I can calculate the other filters myself but I couldn't "see" the JTM ones.
Thanks for the detailed explanation and for the graphs as well!
A variation of JMP-1 cabsim can be found also in Marshall's 6100 amp.

Would a transistor based gyrator provide the same amount of boost /JMP-1/ as the opamp one?  This way the cabsim can be built around a single TL074.

[Gilles C]

Btw, as I needed a good DI box fast someday to connect my Dobro style guitar to the main console for a few gigs, I decided to buy Behringer Ultra DI box which has a 4 x 12" cabinet sim. It sounded so good that I never used the Red Box again after that...

The sound man was satisfied, no hum and didn't have to use the ground lift switch. People told me the sound was perfect. I was happy...

Too bad I don't have the schematic, but I have the box, so I don't have to build one.

Some may not like the company or their boxes, but I have no peoblem with their stuff.

http://www.behringer.com/GI100/index.cfm?lang=ENG

Gilles

[MetalGuy]

The company doesn't matter as long as I can get from the product what I need.  $35 /which is the cost of this DI box/ is maybe less than the retail price of the parts for a similar DIY project.

Has anyone tried one of these: