Right, I've finally done it! I thought it would be difficult but it was a piece of cake. Downloaded some cunning software that a the very clever fdeck had written, installed it, plugged output of soundcard into input of preamp and output of preamp into input of soundcard. I highly recommend doing this, it's very very enlightening. Let me know if you want to know links to software and more in depth info on how to do it.
The software lets you paste the data into excel so you can then create comparison graphs. It would be great to build up a database of these so you can understand what the 'GK' or 'SWR' sound is and how to EQ another amp for it.
Bear in mind that the scale varies from graph to graph, as does the relative gain.
So here we can see that the default SWR Grand Prix tone (with this particularly NOS 5751 valve) has a broad mid scoop centred at 250Hz and about 8dB deep compared to the bass and treble peaks. Also that boost in the lowest lows explains why SWR amps are incorrectly referred to as being underpowered - they simply put out too much in the region where the cabinet cannot reproduce it. The broad treble boost explains the inherent bright clear tone. I was surprised that it was this far from flat as when I've AB'd between preamp and through FX loop (which I scoped and found was near perfectly flat) with the bass it's sounded very very similar. However when I've played program music through the amp by plugging in an iPOD or CD player it's always sounded somewhat shy in the low mids. This can be pretty well corrected using the semi-parametric EQ to add about 8dB of boost at about 250Hz.
Interesting point here is that the bass and treble EQ seem to be peaking not shelving EQ. I'll try and get round to doing full cut plots.
Here's the big myth destroyer! What you can see on this plot is that the aural enhancer barely does anything to the EQ below 2 o'clock and then by the time it gets to max it is a deep high Q cut at about 250Hz. What you can't see is that as you turn up the aural enhancer it adds gain until about 2 o'clock, in a not insignificant amount. I understand the second half of the dual triode tube in the preamp is used for the aural enhancer so I presume what we're hearing is another load of preamp tube gain, which presumably adds a dash of tube character - it certainly doesn't change the EQ as SWR claim in the lower regions and in the higher regions it's just a simple mid cut (plus a gain boost to compensate).
Alex
The software lets you paste the data into excel so you can then create comparison graphs. It would be great to build up a database of these so you can understand what the 'GK' or 'SWR' sound is and how to EQ another amp for it.
Bear in mind that the scale varies from graph to graph, as does the relative gain.
So here we can see that the default SWR Grand Prix tone (with this particularly NOS 5751 valve) has a broad mid scoop centred at 250Hz and about 8dB deep compared to the bass and treble peaks. Also that boost in the lowest lows explains why SWR amps are incorrectly referred to as being underpowered - they simply put out too much in the region where the cabinet cannot reproduce it. The broad treble boost explains the inherent bright clear tone. I was surprised that it was this far from flat as when I've AB'd between preamp and through FX loop (which I scoped and found was near perfectly flat) with the bass it's sounded very very similar. However when I've played program music through the amp by plugging in an iPOD or CD player it's always sounded somewhat shy in the low mids. This can be pretty well corrected using the semi-parametric EQ to add about 8dB of boost at about 250Hz.
Interesting point here is that the bass and treble EQ seem to be peaking not shelving EQ. I'll try and get round to doing full cut plots.
Here's the big myth destroyer! What you can see on this plot is that the aural enhancer barely does anything to the EQ below 2 o'clock and then by the time it gets to max it is a deep high Q cut at about 250Hz. What you can't see is that as you turn up the aural enhancer it adds gain until about 2 o'clock, in a not insignificant amount. I understand the second half of the dual triode tube in the preamp is used for the aural enhancer so I presume what we're hearing is another load of preamp tube gain, which presumably adds a dash of tube character - it certainly doesn't change the EQ as SWR claim in the lower regions and in the higher regions it's just a simple mid cut (plus a gain boost to compensate).
Alex
