EQ values across (nearly) all Ampeg tube bass models compared

[parker_knoll]

So, being extremely nerdy by nature but also annoyed/confused by the minor differences in EQ between Ampeg models, I went through all the manuals I could find.
I didn't bother with the V5, V6 or V7 yet, sorry, or the V2, V3, or V4.
So these are the stated values - I didn't measure anything.



FINDINGS:

• Lots of minor differences, especially in the treble frequency (4KHz vs 5Khz) and in the Ultra Hi (5kHz vs 8Khz).
• The SVT-VR Ch 1 and 50th Anniversary (Heritage) have _nearly_ the same EQ as the original SVT. The difference is in the amount of top end boost with Ultra Hi, while the SVT-CL has more differences from the original.
• SVT II (non Pro) and SVT III (non Pro) are _not_ the same
• SVT 2 Pro and SVP Pro are _not_ the same as SVT 3/4 Pro
• SVP-CL is pretty unique in its EQ section (shame I missed that one recently on eBay)
• Only the V4BH and the SVT II/P and SVT 2 Pro/SVP offer the very high 10KHz boost
• You can pretty much approximate the EQ of one amp in another, especially those with Graphic EQs as the Graphic EQ values are usually different to the tone section but the knobs will not be in the same positions.

 

[RasJay]

I just got a used PF-50T and have been searching online to see if there any comments about the EQ section. Per the manual, the Bass appears to be unity at noon, however the Mid and Treble are not. The amp sounds great but I find the EQ boost/cut values odd if it is an active EQ.

 

[EastDakota]

I love the amp but it's always bothered me that the 3-Pro has four different EQ adjustments at 5kHz (treble, ultra lo, ultra hi, and a graphic slider) for when you need +30.5dB there. This validates my priors that it was a weird design choice.

 

[parker_knoll]

I love the amp but it's always bothered me that the 3-Pro has four different EQ adjustments at 5kHz (treble, ultra lo, ultra hi, and a graphic slider) for when you need +30.5dB there. This validates my priors that it was a weird design choice.

that's what started my quest! I was using the SVT 4 Pro and found myself pumping 8Khz on the graphic for some 'air' but the graphic also introduces a bit of noise. Then I got a SVT II and a 2 Pro and realised all these EQ sections were quite different. I found it quite hard to get the sound I wanted with the II (non Pro) for example.

One also wonders, why the inconsistency? Why make these minor differences on each very similar amp? I mean, Fender offered basically the same tone circuit on everything (including bass amps) for about 30 years

 

[parker_knoll]

I just got a used PF-50T and have been searching online to see if there any comments about the EQ section. Per the manual, the Bass appears to be unity at noon, however the Mid and Treble are not. The amp sounds great but I find the EQ boost/cut values odd if it is an active EQ.

I mean the amp has a core sound which is not going to be a flat response - so having all the knobs at noon in theory means the EQ is not doing anything but, especially with a tube amp, there will still be a sonic signature, usually involving some mid cut

 

[Jim C]

I mean the amp has a core sound which is not going to be a flat response - so having all the knobs at noon in theory means the EQ is not doing anything but, especially with a tube amp, there will still be a sonic signature, usually involving some mid cut

This has been my exact findings.

 

[EastDakota]

that's what started my quest! I was using the SVT 4 Pro and found myself pumping 8Khz on the graphic for some 'air' but the graphic also introduces a bit of noise. Then I got a SVT II and a 2 Pro and realised all these EQ sections were quite different. I found it quite hard to get the sound I wanted with the II (non Pro) for example.

One also wonders, why the inconsistency? Why make these minor differences on each very similar amp? I mean, Fender offered basically the same tone circuit on everything (including bass amps) for about 30 years

Ahh that's funny, yeah I haven't had another SVT variant and wonder how it would be dialing them into what I want. You can't fully tell from the block diagram in the manual since it has just a giant "TUBES" for all three preamp tubes, but I'm assuming that the different 5kHz adjustments come at different points in the circuit between the individual tube stages.

 

[beans-on-toast]

The published specs don’t take into account component variation and changes due to age. Samples of the same model may not perform exactly alike. It’s usually subtle.