BlackHeart "Little Giant"

[chuck7]

CB, a lot of that stuff is over my head, but it is very interesting.  I'll have to go read a basic tube primer somewhere and then come back and read it again. 

So if I were to order the tubes that Jack recommends, would I have to have them biased before I could install them, or do they generally ship in a usable state?

 

[neilium]

CB, a lot of that stuff is over my head, but it is very interesting.  I'll have to go read a basic tube primer somewhere and then come back and read it again. 

So if I were to order the tubes that Jack recommends, would I have to have them biased before I could install them, or do they generally ship in a usable state?

First off, bias isn't an adjustment made to the tubes, it's an adjustment made to the circuit to compensate for the variances from tube to tube. Assuming everything else is working, you can pull out one power tube and replace it with another working one and everything will work. You adjust the bias to find the "optimal" operating point for the new tube. That part is somewhat subjective.

Think about bias like this: you have a lever that you want to use to turn tiny motions on one end into larger motions on the other. Currently, the lever is lying on the ground. You can lift the lever up, but you can't push it down. It is only doing half of the work you need it to. So, what do you do? You can't move the ground, but you can lift the lever. You get a saw horse and use it as a fulcrum, lifting the lever off the ground. Now your lever swings both up and down. The fulcrum is your bias.

 

[jackthehack]

+1 on neilium's reply; from CB's FAQ:

8. - How does the bias effect tone?

As the bias is set lower the amplifier will operate closer to Class-B.  The tone will be a little "thinner" or less full since the amplifier will not be hitting it's output tubes saturation point quite as easily.  If the amplifier is biased very low, higher volumes will encounter crossover distortion.  Properly biased in a lower range, the overall clean headroom of the amplifier will be greater.

As the bias is adjusted higher, toward Class-A operation, the tone will be "thicker", "fatter" or more full. The overall headroom of the amp will be less, since the signal level at the grid, added to the bias voltage will be closer to the tubes saturation point.  The amplifier will distort easier (musical distortion, not that nasty crossover distortion stuff).

9. - If I set the bias too high or too low, will it hurt the amplifier?

If you set it too low, then no harm can be done. If the bias is set too high, then there is the possibility that the output tubes will not be able to dissipate the extra heat, the plates will start to glow. The tubes will do a major meltdown. There is a possibility of power transformer and or output transformer failure if the failing tubes short.

The default Blackheart BH5H bias is NOT set too high for the Groove Tubes ST-EL84-S Silver series EL84, I've been running mine for a while now with no ill effects to tube/transformers/etc.

The Groove Tubes ST-EL84-S Silver series EL84 tube takes the same default voltage as the stock no-name Chinese EL84, but does not break up as bad at the max volume levels of pentode or triode mode of the amp; it's "cleaner", less distorted than the stock tube at volume, which is the sound I prefer....

 

[dbw]

Think about bias like this: you have a lever that you want to use to turn tiny motions on one end into larger motions on the other. Currently, the lever is lying on the ground. You can lift the lever up, but you can't push it down. It is only doing half of the work you need it to. So, what do you do? You can't move the ground, but you can lift the lever. You get a saw horse and use it as a fulcrum, lifting the lever off the ground. Now your lever swings both up and down. The fulcrum is your bias.

:icon_thumright:

 

[chuck7]

Thanks again to all for the information.  I do think you left one thing out of your leaver metaphor though.  That being the part where if you make the fulcrum tower too tall, the whole damned thing bursts into flames  :hello2:

 

[neilium]

Thanks again to all for the information.  I do think you left one thing out of your leaver metaphor though.  That being the part where if you make the fulcrum tower too tall, the whole damned thing bursts into flames  :hello2:

LO friggin L.

 

[Crappy]

Well I got the new tubes in the mail time to play with them.

Head (A) was Ei EL84 and Sovtek 12AX7WB
Head (B) Stock tubes

Well I though that the stock tubes sounded fine.
After hearing the new tubes the old one sound like 2 tin cans with a string / sounds sharp and bitting. Tubes start to break at 7 on the knob
New tubes warm, full, and clean right up to 9 on the knob.

 

[jackthehack]

Just out of curiousity, where did you find the Ei EL84? I looked all over and couldn't find anything but a 5 pack...

 

[Crappy]

Just out of curiousity, where did you find the Ei EL84? I looked all over and couldn't find anything but a 5 pack...

Picked them up at http://www.dougstubes.com/

 

[Crappy]

I have 2 other tubes that I'm going to try out the Groove Tubes GT 12AX7-C and the GT ECC83S
I was thinking of running the 12AX7WB in one head and the ECC83 in the other to try and get a mix of the 2 sounds I'll just have to see how it sounds and if them mix well together.
Both heads would have the Ei EL84 in them

I know now I can never go back to using the old tubes ccasion14:

 

[chuck7]

well I got my little giant combo in today.  It was sitting there in the living room waiting for me when I got home.  Have to say, I am quite pleased.  The only issue is that even in triode mode, you have to crank it so loud to get it to distort that my wife gets up in a huff.  Any body know where I can pickup a mod for the wife that disables the "bitching about the volume" circuit?

 

[-CB-]

give her the car keys and some cash

tell her to go shopping

 

[jackthehack]

This mod should work, available from any number of local or online outlets:

 

[RLW]

One of my friends has a wife who is one of the bigwigs at M. D. Anderson Hospital in Houston. A couple of weeks ago I was over visiting while she was shopping, she came home and said "I saw this and I know you always wanted one, and it was so cute I just had to buy it for you!" She handed him a brand new Martin D-45.

I keep telling him that he hit the matrimonial Wheel Of Fortune. And I keep asking Lisa if she has a sister.

 

[Shmoopie]

does she have a cute bisexual daughter, whose not afraid to put her back into it, ok, i've said to much.

 

[jackthehack]

"I saw this and I know you always wanted one, and it was so cute I just had to buy it for you!" She handed him a brand new Martin D-45."

Imagine what she bought HERSELF?

 

[RLW]

"I saw this and I know you always wanted one, and it was so cute I just had to buy it for you!" She handed him a brand new Martin D-45."

Imagine what she bought HERSELF?

She can afford it. Trust me.

 

[jackthehack]

Went and checked out my Little Giant with 12AX7WB/GT-EL84S tube mod against a Dr. Z Mini-Z 5 watt head.

Differences: BlackHeart has a little more clean headroom. Mini-Z costs $575 more (accounting for tube mod). Store owner: Not pleased.

 

[Patrick from Davis]

I asked a question to the guys at the Tube Store about Groove Tubes.  Since Groove Tubes relabel tubes made from the major tube manufacturers I was curious what the Silver Series tube line really was.  Apparently it is the "unmatched" tubes that groove tubes sells.  The SS-EL84-S are JJ Tesla tubes, and the SS-EL84-R are Sovtek.  I am not sure about how correct this is, but it does make me a bit happier because I have a JJ EL84 that doesn't have a home.  Yet.
Patrick

 

[jackthehack]

I got a GT-EL84-R duet set for my YellowJacket adapters; there's no real discernable difference between a GT-EL84-R and the SS-EL84-S in the Little Giant head