What's the difference in tone?

[big bob]

Hi guys, I hope everyone is having as nice a week as I am. I have a question. I'm considering my next amp build and I was wondering what the difference, if any , in tone that "how an amp is biased" makes.

Here is what I'm looking at, I would like to make a 5e3 circuit with transformers that can push 2 x 6l6s. I have found two plans that I like, very simple, two volume one tone. 1is fixed bias.

2 is cathode biased. How does this aspect affect the tone.

 

1 https://taweber.powweb.com/store/5e3p_layout.jpg

2. http://site.triodestore.com/5E3DeluxeLayout40-18017120V.pdf

 

Any thoughts.

 

[DetroitBlues]

Wish I knew enough to help you... Hotter tubes usually means a better sweet spot. Two volumes sounds like a good preamp gain stage..

[Bonefish]

I did a bit of reading on this as the Line 6 DT25 will run in both modes. The Fixed Bias has a reputation for a tighter bottom end (Marshall and Fender) while the Cathode bias tends to have more of a chimy Vox type feel. A great introductory article is here: http://www.classictubeamps.com/BiasSupply.html.

[big bob]

I did a bit of reading on this as the Line 6 DT25 will run in both modes. The Fixed Bias has a reputation for a tighter bottom end (Marshall and Fender) while the Cathode bias tends to have more of a chimy Vox type feel. A great introductory article is here: http://www.classictubeamps.com/BiasSupply.html.

 

Thanks for the link, that's kinda what I thought.. I do like the chime of the champinstein with a 6l6.

[mad dog]

Fixed bias generally does tighten the bass, also adds a bit of power. Beyond that, hard to generalize. A lot depends on the circuit. I have an amp (Sewell Wampus Cat) with switchable bias, much prefer the fixed mode. But on my tweed tremolux type (Victoria Trem de la Trem), I love how that amp works in cathode bias.

 

MD

[212Mavguy]

I glanced at both layouts. #1 does not appear to be as close to original circuit as #2. Note 12ax7 V1 vs 12ay7 in second. The Triode Electronics company I know is not a low end of market type of outfit, they are very competent and seem to know about what they sell, FWIW.

 

As far as the bias thang goes, in a fixed bias circuit the bias pot setting to a certain extent IS a global tone control. Colder tends to brighter among other things.

 

There is something in that original circuit you want in your build's tones. So the type of bias scheme used in the original circuit is what I'd be inclined to in order to retain as much of the original feel.

 

Since it's possible to get decent new production 6l6's as well as 6v6's within decent factory matching, even cryo'ed, I'd go the cathode bias route, get some resistors a step or two above and below the schematic setting. That cathode bias power tube resistor will get very hot, won't hurt to double the wattage rating.

 

In tube rectified amps, since different rec tube types put out slightly different voltages, you can get some tonal and response changes with rec tube selection if the socket allows various rectifiers within the same pinout, for octals the copper cap thang is not the only way to go. Watch the heater rating for the rec tube when subbing out in octal socket types. My fave by far for 5y3 is Bendix 6106 or other milspec 5y3wgt with a "W" in the suffix. 6106's take a full minute to warm up, don't start to conduct until about the 45 second mark.

 

Most old cathode biased amps I have experienced run the output tubes pretty darn hot, like close to 100% plate dissipation, with even a tad of color or redstriping on the plates. The amp you are building will probably sound better with that cathode resistor at a value taking the tubes closer to 75% and not much higher in most Push Pull designs, IMHO. The tubes will last quite a bit less run hotter. Tube coolers do work.

[big bob]

I glanced at both layouts. #1 does not appear to be as close to original circuit as #2. Note 12ax7 V1 vs 12ay7 in second. The Triode Electronics company I know is not a low end of market type of outfit, they are very competent and seem to know about what they sell, FWIW.

 

As far as the bias thang goes, in a fixed bias circuit the bias pot setting to a certain extent IS a global tone control. Colder tends to brighter among other things.

 

There is something in that original circuit you want in your build's tones. So the type of bias scheme used in the original circuit is what I'd be inclined to in order to retain as much of the original feel.

 

Since it's possible to get decent new production 6l6's as well as 6v6's within decent factory matching, even cryo'ed, I'd go the cathode bias route, get some resistors a step or two above and below the schematic setting. That cathode bias power tube resistor will get very hot, won't hurt to double the wattage rating.

 

In tube rectified amps, since different rec tube types put out slightly different voltages, you can get some tonal and response changes with rec tube selection if the socket allows various rectifiers within the same pinout, for octals the copper cap thang is not the only way to go. Watch the heater rating for the rec tube when subbing out in octal socket types. My fave by far for 5y3 is Bendix 6106 or other milspec 5y3wgt with a "W" in the suffix. 6106's take a full minute to warm up, don't start to conduct until about the 45 second mark.

 

Most old cathode biased amps I have experienced run the output tubes pretty darn hot, like close to 100% plate dissipation, with even a tad of color or redstriping on the plates. The amp you are building will probably sound better with that cathode resistor at a value taking the tubes closer to 75% and not much higher in most Push Pull designs, IMHO. The tubes will last quite a bit less run hotter. Tube coolers do work.

 

I will probably source the parts myself rather than go with a kit. I do like the triode layout.

The thing I'm looking for is this. I really like the champ circuit with a 6l6 the tone is huge and deep and chimy. But my little champ gets fuzzy past about 6 and 6 is just not loud enough for the band. My sound city on the other hand is just to loud. So I would like to build a circuit similar to the champ but with 25-30 watts output. 6l6 of course.

[212Mavguy]

For an interesting alternative, check out Angela Instruments for their super single ended 6v6 schematic, it's more what you are looking for, a higher powered single ended using two power tubes in parallell, two rectifier tubes in parallell.. This circuit has more power potential than a Champ and can be easily tweaked to tonal taste. They also have a lot of the parts you'll need.