Genz Streamliner 600/900 tone control primer

Discussion in 'Amps [BG]' started by steve_rolfeca, Oct 3, 2011.


  1. steve_rolfeca

    steve_rolfeca Gold Supporting Member

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    I've been running frequency response plots as part of a tube-swapping experiment.

    In the process, I've discovered some things that might be useful for people who are struggling with the Streamliner's tone controls, especially those who like the overall feel of the amp, but are finding it too fat/dark/old-school/muddy.

    I thought this might be a good starting point for a separate thread about people's tone and gain settings. I'd like this to be mainly about the amp's clean tones, but feel free to chip in about how the settings discussed here work for distorted sounds...
  2. steve_rolfeca

    steve_rolfeca Gold Supporting Member

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    First off, there has some been some debate about whether the SL900 is really equivalent to a "real" old-school tube amp.

    Based on my measurements, one area where the Streamliner is VERY much like the real thing, is in the way the controls respond.

    For starters, the gain control affects the treble response at different positions.

    Secondly, the EQ curves for each frequency band are very wide (low-Q) compared to the semi-parametric active filters that are common on many SS amps.

    Last but not least, they are also quite interactive, even the active mid-control. Because of that interaction, and the built-in voicing of the Bass/Treble part of the tone stack, there are some funny things going on with frequency centers.

    Think Ampeg B-15, 100 watt Marshall, or Fender Showman, and you're getting the idea.
  3. KJung

    KJung Supporting Member

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    Cool. With almost every cab and bass I have, I find this starting point a good one to achieve a relatively even tone with this head that is still way fat, but also articulate:

    Gain.... noon
    Volume.... noon
    Bass..... 11 o'clock
    Mid...... 1 o'clock at 600 hz
    Treble.... 11 o'clock
    Master... to taste

    Depending on the room, these settings might vary by 'one tick on the clock' (i.e., dialing the bass down to 10 o'clock and the mids to 2 o'clock in a very big, open, boomy room, or setting the treble at noon in a small, overly carpeted 'dry sounding' venue.

    Some VERY hot basses would need the ratio of Gain to Volume to be lowered, and some very low output basses could probably use hotter gain and volume controls, but these work pretty well with my Sadowsky, Nordy or Alleva.

    Very clean, nice 'hear the winding on the E string' growl, and a very open, sweet, tubelike top end.

    This assumes a two way cab with tweeter. For a one way cab, treble could be boosted a touch.

    While the Streamliner is big down low, I can't quite figure out those who feel they need to cut the bass a massive amount to get a good, articulate tone. I guess with some basses/cabs/technique, you could get into low end trouble with this amp, but I have not experienced that.
  4. KJung

    KJung Supporting Member

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    Good info. With the Streamliner, I treat every control except the master volume as a 'tone control', and +1, everything interacts in a wonderful way to vary the tone of the amp (although this can get you into trouble if you don't realize that the tone controls work quite differently than the vast majority of modern preamps and all in one bass heads).
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  6. steve_rolfeca

    steve_rolfeca Gold Supporting Member

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    With the gain button out and all the preamp controls roughly at noon, the frequency response of the preamp section shows two broad humps. The response is roughly flat between about 600 and 1KHz, the bass is boosted across a broad plateau between 30 and 100Hz, and the response rises to a gently-rounded plateau between 3 and 20KHz. The peak of the upper hump is at 10K.

    The bass hump is about +9dB relative to 1K, and the treble is about +8dB.

    There has been some discussion about whether the Steamliner is scooped in the mids. It's certainly less scooped than some other brands and models, but 9dB certainly qualifies in my book...
  7. KJung

    KJung Supporting Member

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    If I am interpreting this correctly, then my 'slight cut to the bass, slight boost to the mid mids and slight cut to the treble' goes quite a long way to even out the response of the amp, while still allowing that 'big lows versus mids' type response that seems present in a number of all tube amp executions when run at low 'clean' volume levels.

    I really dig it!
  8. steve_rolfeca

    steve_rolfeca Gold Supporting Member

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    Another thing my testing shows, is that twisting the mid control doesn't cause peaks or troughs at the exact center frequencies you might be expecting.

    For instance, when I tried cutting the bass and treble a bunch and boosting the mids (controls at 9-3-9) in order to get a better idea of what the Mid Freq switch was doing, the resultant humps were centered down at 170Hz (220), and 250Hz (600).

    The 2.5K setting didn't produce a single, broad hump. Instead, it gave a smooth response with the low end and treble trailing off, a small hump at 150Hz, and a broad, shallow peak at about 1.5KHz.
  9. Sharknose79

    Sharknose79 UNPAID greenboy/fEARful endorser Supporting Member

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    Subscribed.
    I have one of these heading my way...should be here by Friday...going to run it thru a fEARful 15/6/1.

    Thanks for the heads-up about the tone controls....
  10. Highfox

    Highfox

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    Same here.
    My 600 should be here tomorrow, I'm pairing it up with the GB Neox212t.
  11. steve_rolfeca

    steve_rolfeca Gold Supporting Member

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    Ken's got a good ear! His setting of 11-1-11 with gain and volume at noon, represents a broad plateau between 35 and 200 Hz, peaking at about +6dB @ 100Hz, flat from about 800 to 1.5K, and then gradually rising to another plateau of about +5dB between 8K and 12K.

    Pretty much typical "make it sound nice" settings for a 5-string when recording...
  12. KJung

    KJung Supporting Member

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    Excellent... fun to see some numbers representing what I'm hearing. Fun thread!
  13. kesslari

    kesslari Supporting Member

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    That's my rig - and it rocks.
    Agreed, this is a great thread. Thanks Steve!
  14. Joe Smithberger

    Joe Smithberger Supporting Member

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    While sounding nice is the goal, with your methodology, is it possible to get even close to flat? What would that look like assuming that the input gain and volume are still at noon (9-1-9)?
  15. steve_rolfeca

    steve_rolfeca Gold Supporting Member

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    Not everybody shares my fascination with hi-fi response. But if you want to mimic a flat-response channel strip with a mid-boost to "fix" a scoop in your cab's response, it takes some tweaking to get the bumps to correspond to the frequencies listed on the amp's front panel, and to avoid dips at other places in the spectrum.

    These settings were the best I could manage (all with the gain at noon, and the volume around 12 o'clock to 1 o'clock):

    NOTE: I know this is confusing, but I find myself mixing clock face and decimal terminology. So a hair past 1 o'clock is 1.1, half way between 1:00 and 2:00 is 2.5, and so on:

    Roughly flat response with a peak of about +8dB at 220: 8.8-3-10 bass/mid/treble. The actual peak was at 170Hz.

    About +6.5dB at 600: 10-4.5-10.5. This was the hardest to nail- the actual peak was still down at 450Hz.

    About +5dB at 2.5K: 10-4-10. There is also a small peak (+3dB) at 100Hz, and a smooth rolloff in the treble, to about -2dB at 20K.
  16. steve_rolfeca

    steve_rolfeca Gold Supporting Member

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    This is why it gets confusing when you look at all the "favourite settings" listed by various guys over on the main Streamliner thread. With all that interactivity, there's more than one way to skin a cat. For example, a big bump or cut in the lower mids, can be more or less wiped out by the setting of the bass control. Bumping the Gain knob to 3 o'clock rolls off some treble, and the treble response varies depending on how hard you're pushing V1 as well, just to further complicate matters.

    I didn't find anything that would pass for "surgically flat", but there are some settings that get pretty close. For example, with the mids at 2.5K, try 9.4-2.1-10 bass/mid/treble, gain button out, Gain at noon and Volume at about 1 o'clock.

    This has a nice low-end extension (only -1.4dB @ 30Hz), broad peaks of about 2dB @ 130Hz and again between 3 and 4KHz, and a smooth rolloff to about -2dB at 20KHz.

    +/- 2dB from 30 to 20,000 Hz would be pretty good for the preamp in any MI amp. Even if it takes some knob-twisting to get there with the Streamliner, IME that level of performance is quite unusual in a bass head, whether we're talking tube, hybrid or SS...
  17. steve_rolfeca

    steve_rolfeca Gold Supporting Member

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    Something that I found noteworthy about the Streamliner as I was compiling all those traces, was the broad shapes I was drawing with the EQ. If you put these tone controls in a console, the marketing guys would be talking about "British EQ" in their advertising copy...

    This is nothing like the narrow cuts and boosts that I'm used to seeing on modern channel strips, or on hybrid bass heads like the SWR's and Eden's that I've been fooling around with for the last decade or two. This also explains why the Streamliner gets kudos for having "musical" EQ- there are none of the sharp-edged cuts or boosts that can make an amp sound nasal, clangy, hissy, etc.

    If I needed sharper, more surgical EQ (if I was into slap or doubled on upright, for example), I would probably think about stuffing an Empress ParaEQ in the effects loop. That's about the only way you're going to get the Streamliner to behave like a Shuttlemax.
  18. Ukiah Bass

    Ukiah Bass Supporting Member

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    Steve, thanks for the thread. Is it possible to capture and post screen shots of your sonic comparison graphs? greenboy did this for his fEARful cabinet designs, which were very useful. Non-technical people (like me) can often process images better than descriptions of numbers.
  19. 5StringPocket

    5StringPocket Supporting Member

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    +1 Graphs which show some of the tone control interactions and how the peaks and valleys shift are very useful when shaping your sound. For most players it's not about "flat" but more about dialing in the sound you're looking for.
  20. 3rdcurve

    3rdcurve Supporting Member

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    Those are my goto settings as well, I rarely stray too far from there.
  21. Darkstrike

    Darkstrike Return Of The King!

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    Good thread, some very interesting stuff.

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