Mating 4 6l6gc to the right ot

[Cubed]

Hello, I'm starting to understand the data sheet and I see there's info for effective load resistance for 1 and 2 tubes in a single ended amp and the elr for a push pull amp with 2 tubes.

My question is how do I figure out the elr for 4 6l6gc in a push pull setting?

I would think this would be a good ot for it (from what I read in the description) but I can't get the math right before I pull the trigger

http://www.classictone.net/40-18013.html


Thanks

[Tony Bones]

Use 1/2 the load you would use for a pair of 6L6 under the same operating conditions.

That Classictone OT will work fine assuming you're running the tubes around the same voltages and currents as a BF Twin.

[Cubed]

Thanks for the details!

I will look into the bf twin specs then. I wanted to follow what the data sheet said but I will look further into design and specs as there's much more I can learn.

[Cubed]

It seems I put the carriage in front of the horse.

It seems I the effective load resistance can be adjusted with different voltages and or current.

I'm using this data sheet but how do I figure out what requirements I need to use to get a certain elr?

https://frank.pocnet.net/sheets/127/6/6L6GC.pdf

I do apologize for the dumb questions, seems I'm biting of more then I can handle. 

[Tony Bones]

It seems I put the carriage in front of the horse.

Seems likely. 

It seems I the effective load resistance can be adjusted with different voltages and or current.

There's an entire spectrum of things that will work.

Perhaps you should start by identifying some amps that you might like to emulate, then study those amps a little.

Deciding from the start that you want to use 4x6L6 is a little like deciding you want to find a cookie recipe that uses 1/2 stick of butter... unless you have a lot of experience cooking and have a good reason for choosing that exact amount of butter.

Don't tell me you happen to have four 6L6 tubes and want to figure out how to use them. I happen to have 1/2 stick of butter. So what?

[vampwizzard]

I happen to have 1/2 stick of butter. So what?

What you do with 4 6l6's and a half stick of butter is none of my business.

[Cubed]

Thanks again.

I really want to build a 100 watt amp. I'm just sold on the idea. I leaned about elr and winding ratio on the ot so a lot of things just started to make some sense on the power amp section.

But when diving further I couldn't figure out how they got there with certain a certain ot.

I will check out other amps though.

And no, I didn't have 4 tubes laying around, I like the sound of 6l6gc tubes from experience and wanted to go and "come up" with a design with them while also understanding how I got there.

[tubeswell]

100W with 4 x 6L6s? Sounds like you want a 100W twin reverb, quad reverb, super six reverb, or dual showman reverb or similar. So get a PT, choke and OT for one of those. The iron for those amps from 1973 onwards is identical - see attached schematic. (But do yourself a favour and don't build it with the crappy silverface MV circuit. And most guys 'blackface' the bias circuitry)

[Tony Bones]

Thanks again.

I really want to build a 100 watt amp. I'm just sold on the idea. I leaned about elr and winding ratio on the ot so a lot of things just started to make some sense on the power amp section.

But when diving further I couldn't figure out how they got there with certain a certain ot.

In general, when paralleling tubes cut the load in half. So, if you have a SE amp with one output tube and an 8K load, but you want to run two tubes n parallel, then use 8K/2 = 4K load.

There's a column in the 6L6 data sheet showing 2x6L6 at 450V Plate and 400V screen with a 5.6K load, so 4x6L6 should run at 2.8K. The Fender amps that Tubeswell posted run 4x6L6 at around 450V on both plates an screen with a 2.1K load and it seem to work very well. (That's the Classictone OT you linked to.)

There's a fairly wide range of loads that will work. Changing it will affect the sound, but it's hard to say how without trying it. A this point I wouldn't worry too much about this detail.

[jjasilli]

100W with 4 x 6L6s? Sounds like you want a 100W twin reverb, quad reverb, super six reverb, or dual showman reverb or similar. So get a PT, choke and OT for one of those. The iron for those amps from 1973 onwards is identical - see attached schematic. (But do yourself a favour and don't build it with the crappy silverface MV circuit. And most guys 'blackface' the bias circuitry)

IMHO this is the best advice.  I.e., plagiarize iron selection, and power supply specs, from a known 4X 6L6 amp that you like. 


N.B.: the tube charts show plate loads affected by factors other than voltage:  such as THD; and rather low screen voltages which are not ordinarily used in guitar amps (except for UL).  I.e., in guitar amps idle screen voltage usually equals (or slightly exceeds), plate voltage @ idle.  Hence, guitar amp plate loads will deviate from the tube charts. Knowing the math is good, but not sufficient.  You are condemning yourself to repeat Leo's R&D, usually through years of trial and error.

[PRR]

> I really want to build a 100 watt amp.

Then what jjasilli said. Leo Fender worked it out when Dick Dale was a kid. While his way is not the "only" way, you also want to avoid custom transformers and extended smoke-tests. You buy standard replacement iron for the Fender 80W-100W amps and copy most of the power section from Fender plans.

[st]

I agree more or less. Doing the math and experimenting is half the fun, if you know what your doing.

You now have two options: go with a known working design, or figure it out yourself. Choose the sensible option in view of your experience.

[Cubed]

Thanks for all the info!

I did want to avoid smoking transformers while trying to come up from scratch but what I read in this thread, forum, and from amp builders, it's not a perfect science and I better off as a beginner learning by building a known amp design.


Thanks guys I appreciate taking your time setting me to the right course.