THD Bi Valve 30

  • Hi guys

    I had the house to myself all day and the neighbours were out too so I made some serious noise ! :evil:

    I rigged my THD Bi Valve 30 up to a Recto 212 Horizontal cab and stuck a SM57 in front of it. The recto is loaded with a pair of Mesa C90s rather than the normal V30s

    For those that don't about the THD Bi Valve (and it's little brother the Uni Valve) they are the real valve amp equivalent of an amp modeller 8o They can be lots of different amps in a single box. It does this by allowing you to use any valves you want without the need to rebias anything

    There are two pre amp tubes and you can run both the same or mix and match. At the moment I am simply running 2 x JJ 12AX7

    There are also 2 power tubes and you can run any power tubes (although EL84 needs an adapter which I don't have). If using 6V6 or 6K6 you need to run in Lo Voltage mode. Everything else can run Hi or Lo voltage options. Again you can run matching tubes or two completely different tubes. Today I ran everything in Hi Voltage Mode only.

    It is a non master volume amp so you only get overdrive by turning up the volume and that little sucker is damn loud!!!! Although it also includes a THD Hot Plate Attenuator to bring it under some sort of control. It also has a noise gate of sorts which uses a simple bulb but works really well. For the purposes of profiling though I turned both of these off to get the pure amp sound.

    There are two input options "More" which is full bore all guns blazing. And "Less" which is a 20db input pad to clean things up a bit.

    I had the amp loaded with a pair of JJ EL34 and started making some profiles, gradually raising the volume until the "Less" input was completely dimed and the power tubes were cooking. Then I switched over to the "More" input turned the volume way down (to around the point that Less left off) and started raising the volume again until I finished off with the amp running on melt down mode. I was going to try everything on 10 but that actually caused the amp to start fizzing and losing volume so rolled the Treble and Bass back a bit to stop that; but the final profile is pretty much everything dimed.

    Once I got to Profile 7 I thought, "wait a minute why not do two more with different valves". So 7a is 2 x EL34. 7b is 1 JJEL34 and 1 JJ 6L6. 7c is 2 x JJ 6L6. Using the KPA to quickly switch between different output valves really highlights just how little difference output valve actually make. There are differences but they are super subtle. To me these three profiles are so similar as to make no difference in a musical context; even in a fully cranked non master volume amp where the power tubes are being slammed which should really highlight the differences and make you notice specific tube character. I wonder if a lot of the time when people say that they prefer EL34 or 6L6 or KT88 etc they are looking through rose tinted glasses because they have never had the chance to flip between them and compare in real time.

    None of the settings were tweaked on the KPA when saving so the profiles are just literally what the mic picked up. There is plenty of scope to tweak the tone controls etc to taste.

    I used a PRS 513 with full Rosewood neck when profiling and tested each sound with Single Coil, Low Output HB and Hi Output HB modes so the profiles should work with most guitars. Being a non master volume amp it is super sensitive to the guitar volume so even the cranked profiles clean up pretty well. Even the three no 7 profiles give a really nice neck single coil clean tone with the guitar volume down around 3

    I loaded them on to Rig Exchange under author Wheresthedug and rig names AD - THD BiValve if anyone is interested in what this little Frankenstein is capable of.

    Have fun.


  • I've uploaded the rest of my BiValve Profiles to Rig Exchange now.

    I made a bunch of profiles at different gain levels to test how reducing the gain parameter on the KPA compared to reducing the gain on that amp itself.

    I had a theory that, as the profiling process captures the input signal from very quiet to super loud, this would mean that a profile has all the information it needs to behave like the amp when reducing gain but it would still need to guess the effect of increasing gain. Therefore, reducing the gain on a profile should sound more authentic than increasing it.

    I decided to test it by profiling my THD BiValve at all volume (its a non-master volume amp) from 1 - 10. I then took a high gain profile and tried reducing the gain to match that of a lower gain profile with the same gain level in the KPA. The lowered gain settings sounded great but not the same as the actual lower gain profiles. You can test it yourself with these profiles if you want.

    Reducing the gain on a profile behaves almost exactly like turning down the guitar volume knob on the amp itself. They are similar in some ways but definitely yield different results.

  • I've found it very much depends on the profile.

    When I run into the power section of my tube amp and shut off the cab, I get varied results as well. Some JTM profiles are amazing this way. Never really clean, but a nice easy bite.

    Thank for the new profiles!