My take on Eric Johnson's Steel String Singer #005

[martin manning]

IMO this is a better step filter design: https://ampgarage.com/forum/viewtopic.p ... 43#p378843

[rootz]

Guy, Martin,
I already opted for different values in the high filter, more in line with your design Martin. But even then I found the top steps of the high filter too much for my liking. Just harsh, overbearing upper mids that did not sound right. The low filter is ‘standard’ and actually works well.

What did I do to the filter? I went for 0, 68, 100, 150, 220 and 390 pF (6 steps) and loaded the filter section with a 470p silver mica to ground. The result is quite to my liking. Now the high filter can be used ti fit different guitars, or make the amp sound more forward on stage. Works great with my pedal board now too. I use multiple overdrives, one off them being a Wampler Triple Wreck. That pedal sounds monstrous through the SSS. The low end is massive and deep but stays clean and thighs at the same time. All the talk about this ‘feature’ of the SSS is real, admittedly to my surprise.

So yes Guy, start low with the filters and go up in small increments. Might I add that I do not have any pictures or other intel on the high filter values of the real SSS or its clones. Would love to see, but then again, this is tuned to my taste.

[martin manning]

I recommend going all in on the revised filter exactly as I have it shown. Member dreric posted clips of his SSS using that circuit and it functioned very nicely (see in the same thread linked above, especially the second video). You can see in the Bode plot that it is symmetrical, and that both the treble and bass controls have equal steps, which the original (at least as we know it) did not.

[rootz]

I can see why dreric liked your filter design! Haven't tried it yet, but sure looks a lot like mine IF you change the cap to ground after the filter accordingly. Seems like your design works a bit more on the mids too. I wonder how that would sound.

Two Sims added for working of the low and high filter.

Please do note not all pictures of the Steel String Sultans, HPD and SSS for AN that I have, show the cap loading the filter section. You'd normally see that between the reverb return pot 3rd lug and the buss bar. Again, makes me wonder why some amps miss that cap. Different high filter values? 6550 and OPT darker sounding (my Peavey iron is rather dark sounding)? Maybe amps without that cap are just very bright?

Edit: Martin's filter in green, mine in blue.

[Guy77]

Guy, Martin,
I already opted for different values in the high filter, more in line with your design Martin. But even then I found the top steps of the high filter too much for my liking. Just harsh, overbearing upper mids that did not sound right. The low filter is ‘standard’ and actually works well.

What did I do to the filter? I went for 0, 68, 100, 150, 220 and 390 pF (6 steps) and loaded the filter section with a 470p silver mica to ground. The result is quite to my liking. Now the high filter can be used ti fit different guitars, or make the amp sound more forward on stage. Works great with my pedal board now too. I use multiple overdrives, one off them being a Wampler Triple Wreck. That pedal sounds monstrous through the SSS. The low end is massive and deep but stays clean and thighs at the same time. All the talk about this ‘feature’ of the SSS is real, admittedly to my surprise.

So yes Guy, start low with the filters and go up in small increments. Might I add that I do not have any pictures or other intel on the high filter values of the real SSS or its clones. Would love to see, but then again, this is tuned to my taste.

Thanks Rootz. I will try these lower values on my step filters. I also remember chatting with Ryan ( SSS#002) a while back and he also mentioned he wanted a more gradual increase with smaller values in his step filter as well. I am also very partial to things not sounding too bright.

Will post my finding when I finish my SSS this summer.

Cheers

Guy

[martin manning]

Martin's filter in green, mine in blue.

I see you have my values on the bass side, but not on the treble (both schematics), and there is a larger high cut on the lowest treble trace than I would expect. I agree that the cap to ground should be reduced if the reverb input and bypass network is placed at the filter input (unlike SSS #002, for which all the values were selected), say 500p - 1n.

PS Why does the bass side have such a narrow response (spike at ~100Hz)?

[rootz]

This is nice to experiment with, Guy. I guess the final construction is much a sum of the different parts that you select. As I mentioned, I paired the SSS005 pre with my ODS #94 output and the resulting sound I got was much less trebly when compared to the SSS output stage. Might be the CF that is brighter or the 6V6 tubes in the SSS, but I guess also the Peavey OPT in my 94 is more 'vintage' sounding than my new Hammond in the SSS.

Martin, one amp has your filters, the other my current setup. Your low filter offers more range, probably because of the 6n8 cap compared to 10n in my version? I sampled the voltage at the output of the amp, the load. I simulate a realistic load with a reactive network. That's why it looks like a narrow response around 100Hz; it's the resonance peak.

What would you expect for the lowest setting when it comes to the treble cut? The preamp is not especially bright compared to 002 or 004, there is a lot of series resistance before the cap to ground after the filters. And probably most important: the first step has no cap in the high filter. Unlike your design.

[martin manning]

I sampled the voltage at the output of the amp, the load. I simulate a realistic load with a reactive network. That's why it looks like a narrow response around 100Hz; it's the resonance peak.

The resonant peak in the reactive load does have an effect there, but in your plots it seems extreme. Very spiky, and much higher and narrower than I have observed.

What would you expect for the lowest setting when it comes to the treble cut? The preamp is not especially bright compared to 002 or 004, there is a lot of series resistance before the cap to ground after the filters. And probably most important: the first step has no cap in the high filter. Unlike your design.

The green traces, which are said to be my filter, show a large step from the lowest to the next highest treble setting which I do not see. Two of the seven settings on your treble switch are not connected, so you are getting six levels instead of seven.

[rootz]

The big spike in the output around 100Hz is an outcome of the output stage. The output stage is different from 002, 004: more Marshall like values, much lower global nfb. So the stage has got more gain and lower damping factor than most other Dumbles I know of. Maybe with the exception of the Bluesmaster? The load is modelled after one of my EVM12L speakers. Then simplified for use as a load ála the Suhr load box.

Let me make some new plots where the lowest setting on the high filter actually has a cap. Please note that the HPD and Sultan both use a six step filter for both high and low filters. At least the latter does not have a cap on the lowest setting (all pictures of the high filter show only 5 caps). AFAIK none of the 150W variants I have seen in pictures, has a 470p-1n cap loading the filter output.

[martin manning]

Is this the load you are using? Might be hard to tell, but even if I disconnect the NFB in my 002 sim I don't seem to get a peak that is that sharp.

Please note that the HPD and Sultan both use a six step filter for both high and low filters. At least the latter does not have a cap on the lowest setting (all pictures of the high filter show only 5 caps). AFAIK none of the 150W variants I have seen in pictures, has a 470p-1n cap loading the filter output.

I'm not seeking to copy what Dumble or others have done. I was after a more symmetrical, equal-stepped response in the 002 circuit. I used seven positions for a broader range and because seven position switches are easily sourced.

[rootz]

I'm not trying to copy Dumble and others either. They do provide the benchmark in some cases though, in casu as the starting point for further modification to my personal taste. But yeah, I try to get close to an original at first sometimes.

There is more going on than just a different power stage. Less gnfb, different preamp, differing filters, etc. Will include a sim where you can see the preamp output just before the PI entrance. The sim compares the 002 and 005.

[rootz]

Here's a comparison between your filter design and my current setup. This one is more clear than the small pictures I posted before.

Now your filter has a first step cap. To avoid any further confusion: my setup is in my amp as is. I have not used your filter values (yet).

[martin manning]

Here's a comparison between your filter design and my current setup...

Still missing the 4n7 on the seventh treble position though ;^)

[Guy77]

Hi rootz. I noticed something very interesting about your SSS005 build. You used similar voltages on your Phase Inverter and Cathode follower tubes as I used when I built my first Steel String Singer ( without filters) last fall.

I played around with a lot of different voltage settings and these voltages really work well for me on both the Phase Inverter and Cathode Follower tubes.
They seem to hit a sweet spot with the tone I like from these amps.

Guy

[rootz]

Still missing the 4n7 Martin! Which would be about as useful as bacon flavoured toothpaste.

Guy, I'd have to make a new set of comparisons to really hear what the different values mean with respect to character of the amp. What were your observations?