Ways to improve a "stiff" sounding amp.

ItsaBass

ItsaBass

New member
Hi,

I have an Ampeg Super Rocket, which is basically Ampeg's '90's Twin Reverb competitor. 100W, 2x12, channel switching combo. It actually has more in common with a Marshall than with a Twin, though the "vibe" and the market they were going after were all Twin. These are fairly low production amps (300 pieces made over about 10 years, I believe), and I found this one like mint for not much money. I had always drooled over them when they were out, and they are hard to find locally (to avoid shipping charges), so I picked it up.

There are things I like about it and things I don't. I love the girth and the headroom, in the classic Ampeg style. I don't love that the reverb is very weak compared to most Ampegs. The amp is also is a bit stiff sounding and "clattery." The upper end of the mids, and the highs are kind of "boxy" and cold/sterile. It's not an issue of me not being used to what 100W amps sound like; it's just a cold amp. I got rid of the Sovtek pre-amp tubes and put in two JJs followed by a Tung Sol. It is better. But the reverb is still weak, and the boxiness is still there.

So, I was looking for thoughts on my next step. The power amp tubes are GTs. The speakers are stiff and dry Vintage 30's that really need to be broken in extensively and/or played at max volume to sound halfway decent IMO. My thought is to replace one of the speakers with a warmer, more '60's American sounding speaker that will hopefully slightly dominate, while leaving the one V30 in there to provide tightness. I've mixed looser speakers with V30's before and I liked it. Before dropping the dough on that, though, do you think I ought to do more with tubes first? Should I try different pre-amp tubes or different power tubes?

Speakers I am looking at are the Eminence Legend 1258, Swamp Thang, and RW&B.

Any thoughts on jacking up the weak reverb?

Another thought, possibly down the road is going to two Yellow Jackets. Got anything to say about that?
 
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Re: Ways to improve a "stiff" sounding amp.

V30s in a clean high headroom amp? Kill them with fire!:firing: lol
Texas Heats ftw. - a pair of em, cos a v30 will sound louder than the darker, slower, warmer and less efficient TH. Two TH's will let you turn the amp up another notch and get more fatness - and you can dial in more treb if you want without cutting off your head. Swampies will sound hollow and loud - better for high gain boogie massive crunch, rwb's will kill you with treble at 100w of clean. dont go there unless you want to play country in a stadium.

Make sure it is biased right. tung sol's in the front end, jj's in the back. The tung sols will give you a nice harmonically rich spark in the high end to give it breath and life. The JJ's will give you plenty of piano or bell like headroom. The GT's are probably the original stock tubes from the 90s - keep em as spares. Yellow jackets will neuter it. Let the amp do what it does best.

The 'verb may have an internal problem tho if its really quiet. Perhaps get it looked at if fresh preamp tubes dont fix it.
 
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Re: Ways to improve a "stiff" sounding amp.

I don't really know for sure, but I have heard that the Ampeg Diamond Blue Series of amps are "self biasing."

I will throw the power tubes on my tube tester at some point in the near future and report back. My gut tells me that they are the original power tubes, but that they are barely used. The amp was literally in mint shape when I got it.

Gibson 175's suggestion of Tung-Sol preamp tubes, JJ power tubes, and Texas Heats would run me about $225. I am thinking that unless the power tubes test poorly, the speakers are a better first line of attack.
 
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Ways to improve a "stiff" sounding amp.

If fixed bias, I bet it is biased cold. A mod worth doing if it is indeed fixed
 
Re: Ways to improve a "stiff" sounding amp.

Always struck me as odd:

FIXED bias amps have adjustable bias and generally need to be biased every time you change the output tubes. (Blackface Fenders, Marshalls, etc.)

CATHODE biased amps don't need to have the bias adjusted. (Fender 5E3 Deluxe, Champ, etc.)

Weird world.
 
Re: Ways to improve a "stiff" sounding amp.

Lewguitar said:
Always struck me as odd:

FIXED bias amps have adjustable bias and generally need to be biased every time you change the output tubes. (Blackface Fenders, Marshalls, etc.)

CATHODE biased amps don't need to have the bias adjusted. (Fender 5E3 Deluxe, Champ, etc.)

Weird world.
Click to expand...

...and which one of those is called "self biasing?"
 
Re: Ways to improve a "stiff" sounding amp.

Just trying to figure out what the bias situation on the amp is, since there have been a few questions about that. The owner's manual is of no help to me, with what I know anyhow. I thought cathode biasing was rare these days. Some old Ampegs used it, but I have never heard the term used in reference to newer ones.
 
Re: Ways to improve a "stiff" sounding amp.

FIXED BIAS: It's called fixed because it has a constant bias voltage regardless of current draw.

CATHODE BIAS: Is technically not "fixed" because the bias voltage increases with current draw. I've heard old guys term it as "dynamic bias".

SELF BIAS: Cathode bias is technically self biasing...to an extent...the cathode resistor has to match the characteristics of to tube(s) used. Self biasing amps (Traynor made a lot of them) use a simple solid state network to sample the stage current and adjust it to maintain a constant current.
 
Re: Ways to improve a "stiff" sounding amp.

glassman said:
FIXED BIAS: It's called fixed because it has a constant bias voltage regardless of current draw.

CATHODE BIAS: Is technically not "fixed" because the bias voltage increases with current draw. I've heard old guys term it as "dynamic bias".

SELF BIAS: Cathode bias is technically self biasing...to an extent...the cathode resistor has to match the characteristics of to tube(s) used. Self biasing amps (Traynor made a lot of them) use a simple solid state network to sample the stage current and adjust it to maintain a constant current.
Click to expand...

There ya go. Thanks. Pretty sure this is a self-biasing amp...in which case, bias adjustment is not an option, correct?
 
Re: Ways to improve a "stiff" sounding amp.

ItsaBass said:
Just trying to figure out what the bias situation on the amp is, since there have been a few questions about that. The owner's manual is of no help to me, with what I know anyhow. I thought cathode biasing was rare these days. Some old Ampegs used it, but I have never heard the term used in reference to newer ones.
Click to expand...

You can contact Loud Technologies Inc; they will send you a schematic but you probably will have to sign a disclaimer that states you will not share it with anyone.
 
Re: Ways to improve a "stiff" sounding amp.

ItsaBass said:
There ya go. Thanks. Pretty sure this is a self-biasing amp...in which case, bias adjustment is not an option, correct?
Click to expand...

True. It can be modified though. I've done that mod to quite a few Traynors when the self biasing circuit failed. Any competent tech can do it.
 
Re: Ways to improve a "stiff" sounding amp.

noob question, but i thought turning the bias pot up made things tighter, and you turned it down to warm it up..? assuming the contacts on the bias pot aren't reversed, and we're not talking about some kind of diezel thing with 7 channels and 32 pots.
glad i've left my bias pots alone so far!

i'd check how the amp's currently biased and look at changing at least one of the speakers first, even if it already has a pot to adjust bias fitted; you know you don't like them, and one would expect the speakers to have more bearing on the overall sound than the power tubes.
: ]
 
Re: Ways to improve a "stiff" sounding amp.

FWIW, I just tested the Groove Tubes. All four of them pass all three of the tests my tube tester performs. No shorts, line test shows 97% or higher on all four tubes (one of them pegs the needle), and about the same percentages on the gas tests. I had a feeling that this thing was barely played.
 
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Re: Ways to improve a "stiff" sounding amp.

One thing I did to get MORE stiffness was to up my filtering values in the power amp.
 
Re: Ways to improve a "stiff" sounding amp.

I'm not familiar with the amp, so a few generalizations:

I hate V-30s, so................ YMMV
Is the rectifier tube or solid state ?
Is the reverb 2 or 3 spring ?
What tube drives the reverb ?

The 1st & cheapest thing I'd try is swapping in an ECC81 into the slot that drives the reverb, see if that loosens it up a bit.

3 spring pan will be "spongier" than a 2.

What type of tone are you looking for, American, British or ???? A mix of ceramic & alnico speakers might help.

As for the Yellow Jackets: I've tried them in a number of amps I didn't quite dig at first. With some, they were the perfect fix, but with others...mehh. They're a little pricey to just get to try, but if you can find some used ones, they're cool to have around.

Good luck ! :beerchug:
 
Re: Ways to improve a "stiff" sounding amp.

A thought just crossed my mind, I too am not a V30 guy, but yank em out and spray fabric softener on em, do it a couple times and get em damp ( put a fan on em, they dry pretty quick). That can really warm up a speaker, done it many times over the years....
 
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