slightly OT -making your tube amp more pedal friendly

[lenwood]

What changes can you make to make your tube amp to make it more acceptable of
different od/distortion pedals?

Or what tube amp preamps are more pedal friendly and why?

Even with the new excellent search I found very little.

Oh and I read the "Tubes for Dummies!" already but want some direction on where to go with those ideas.

Thanks in advance

[brett]

Hi.  I'm certainly no expert, but here's a few ideas anyway.
Personally, I like the classic, single 12AX7 or 12AT7 pre-amp, as on the Marshall 18W.  And preferably not too large a plate resistor in relation to the cathode resistor and bypass cap.  See the Lite II schematic in the downloads section at www.18watt.com for an example. 
If gain is going to be high, and sound levels substantial, you might want to avoid the more microphonic and self-oscillating tubes, such as the LPS and WB versions of the 12AX7.  Although everybody seems to do flips and twists over old tubes, I don't completely agree.  I recently had my daughter swap several 12AX7s in and out of my amp while I played and listened.  On the day, my pick was an ordinary old $15 Ei 12AX7.  Second was a 1960s Mullard.  An old Sovtek out of a 1970s Fender was also quite good.  A Sovtek 12AX7WB, an Ei 12AX7LPS and some other old Mullards 12AX7 were all poor. A Mullard 12AT7 gave an interesting result, I think because it shifted the balance of the distortion from the output section (which it drives less hard than a 12AX7) onto itself.  In any case, it sounded quite good when cranked up a bit more than the 12AX7s.

Oh, yeah.  A lot will depend on whether you have master and volume controls, so you can separate pre from power tube distortion.

Ooops...I think I made you and me more confused than before...
cheers

[JimRayden]

I don't know if it's relevant to this problem but I've noticed the speaker choice is very important. I have a '86 Vermona SS amp at home with a Greenback in it and I don't think an overdrive pedal can sound any better than through my amp. I've tried my own pedals through my amp and through various amps at the store, and I'm merrily sticking with my amp.

But that's just my observation. Can you tell more about what your amp sounds like with pedals, so it would be simpler to troubleshoot. Also, what amp and pedals are they anyway?

---------
Jimbo

[AL]

Clean headroom seems to help a lot. I've yet to hear anything take pedals better than my Quad Reverb. 100 Watts of nothing but clean headroom. I blackfaced to circuitry, which lowered the wattage to around 85, and the cleans are much fuller sounding but it doesn't seem to take pedals as well.

I have several smaller wattage amps (Fenders, Ampegs) but the break up on them is much earlier and all pedals seem to do is add mush. I would assume that a 100 Watt Marshall (older amp NOT the new high gain amps) would have about the same effect although I've no experience with them - 

AL

[lenwood]

I have an amp with 6l6's output but the preamp and phase inverter is changed to
the older marshall plexi preamp like the early super leads except there is one additional gain stage at the beginning.

It becomes consticted sounding with overdrive pedals. I did lower the gain on the second stage by increasing the cathode resistor that seemed to open it up a bit.

I was just wondering the general things about a style of tube preamp that allow using different pedals and most of them sounding good.

For example , the dod/malsteen version OD sounded like crunching glass thru mine. But rangemaster, FET booster, etc all sound good.

DS-1 style , etc distortion sound muffled and too compressed.

Thanks all, and Brett I will look at the lite ii schematic, thanks.

[AL]

In my opinion ALL DS-1's sound muffled and compressed. I hate that pedal - to each his own - some people love it.

My amp is also a 6L6 and I have had the most luck using either a Blue Magic and Nobels ODR-1 - both of these are very transparent overdrives. My back-up is always a Tube Screamer style pedal.
You may have actually helped answer your own question - of the pedals you mentioned the two you liked were boosters.

If you are worried about gain you can try swapping pre-amp tubes. Most 12**7 tubes are interchangeable. The just have different gains with the 12AX7 being the highest. I have used lower gain pre-amps before to get some more headroom so my amps won't break up as early. Here's a link to different gains.

http://www.thetubestore.com/gainfactor.html


AL

[lenwood]

Thanks guys for all the help. Thanks Al I'll look at tube swapping too.

Does anyone else have info about tube amps that sound really good with
different styles of overdrive and distortion pedals without tweaking the pedals to the amp?

[petemoore]

  It's a wierd thing. Depending on the wattage of the amp, what type and how many speakers, ohmage load, how much the input is driven hard and with what...
  What you like about the tone your'e now getting, and what you would like it to do but it doesnt' do..
  I've done copious amounts of building and tweekin' on SB's, and have but one Oa based circuit, the ZW44, but with another output gain stage [to give it the ability to push] and dont use it much.
  A great circuit to start with is a FF. I know you've read about or tried this, these can easily be adjusted for milder to harder distortion.
  FF W/Jfet stratoblaster as output stage sounds really good on my 2w, 22w, 35w and 50w MkII tube amps.
  I have a Rangemaster sounds a great OD tone through the 2w and 22w, otherwise it's basically unusable. I've ceased testing on the 2w, I don't like being connected to the wall plug.
  For just pushing tube amps, the Jfet Stratoblaster is a fave of mine and...someone else...
  For a great 'internal' distorter, BSIAB II seems to do the 'Fuzzy Marshall in a SB thing' as well as anything I've tried through everything.
  HArd to beat a nice Tonebender into tube amp...
  I have a quite large pile of distorter circuits, or rather the boards that have been 'scrapped'...tube amps, guitar pickups, speakers, other devices in the chain...all can be quite picky and subjective when it comes to 'what is doing the clipping'. 
  The 'what isn't it doing' and 'what do you want it to do', descriptive categories may help in choosing SB's and amps mods...
  What changes can you make to make your tube amp to make it more acceptable of different od/distortion pedals? I changed a cap on my MkII's Ch1 input, made all the difference...

[lenwood]

Hey Pete,

A couple of questions;

1, What is an SB?

2. Which cap did you change and what did you change it to?

Thanks man.

[rockindutchboy]

I'm using a Fender twin reverb...its rated at 85 watts....though its probably actually around 100. It's probably the cleanest tube amp anywhere with four 6L6's in the power stage. You can crank it to about 8 before its pre starts distorting...and at that volume you can kiss your ears goodbye.

I use an Electro Harmonix HotTubes pedal for distortion and a Boss CS-3 before it (which I am not exactly too satisfied with) but with this setup, all i have to do is turn the "drive" knob on my HotTubes to dial in a distorion ranging from warm bluesy distortion to hardcore metal, and on any setting the amp will not distort but let all the tone from your pedals come through. The amp is very bright however, and for my pedals I have to turn the highs on the amp down to about 3 to 4.

So an amp that is known to be very clean like the twin reverb with some high wattage will get the job done and will sound great.

[petemoore]

1, What is an SB?
  "Stompbox'
2. Which cap did you change ? The cap is located right on the ch1 volume pot, just inside the front panel...
  and what did you change it to....   .0068uf IIRC...which I probably don't, I tried values near what was in there, just opting for what my ears decided still let some/enough treble through, yet taking the 'Spike in the Forehead high end the amp is known for'...eliminating the nasty "BARK' it would make, or changing that to a nice 'GROWL" instead, when ch1 is used and a harder note would be played.
  Not sure,,,probably it was a Signal path to ground cap at input, which would make it a LP Filter. or...seriesed with Signal path would make it a HP Filter...someone at Ampage just said 'that cap' in more words than that...I swapped it out a few times, decided on a final value that I'm perfectly satisfied and happy with...I have the 'other'cap value in a 'wedge' inside the amp, and taped down too...the 'spare' value I almost decided on.

[petemoore]

  IIUC, most amps have a 68k, right after the input, just before the first tube, and reducing it's value 'mellows' it...never tried it, you should only use this as a basis for investigation, not as gospel.
  I was about to parallel a 100k cap, alligator clipped to the boarded 68k, just to see what the effect would be.
  OF Course you know about the potential voltages, potentially lethal voltages found inside your amp...

[lenwood]

Thanks Pete and rockindutchboy.
This gives me some things to look at.
By taking out the cap on the volume pot that reduced alot of the breakin glass harsh sound now when the preamp is pushed it has more of a 'growl' too. I'll experiment with different values til I get the right amount of
treble.
It sounded real good today and more open sounding with my rangemaster and sd-1 modified super drive and the od 250 style pedal. It seemed to distort less in a good way, of course I like lots of different types of distortion sounds all but the icepick to your temples & spike in your forehead types.

So thanks alot.

[Eb7+9]

What changes can you make to make your tube amp to make it more acceptable of
different od/distortion pedals? Or what tube amp preamps are more pedal friendly and why?

... one idea would be to play with the input headroom of the input gain stage in the amp ... if you grid-bias the front end (see 5C8 Twin schem for example) you'd be driving an input gain stage with a lot less input headroom and more gain than the modern style input circuit ... that should give you a different set of waveshapes ... something to try anyway ...

~jc