Ultra Linear Output Transformers

[bandade]

I am planning a Hot Cat style amp build and am considering using a Dynaco A470 style ultra linear OT from Triode Electronics. I have no experience with ultra linear transformers. Would anyone recommend the the Ultra linear taps on this type of build? Any advice about ultra-linear?

The OT:

http://store.triodestore.com/noname.html

Thanks

[rdjones]

I am planning a Hot Cat style amp build and am considering using a Dynaco A470 style ultra linear OT from Triode Electronics. I have no experience with ultra linear transformers. Would anyone recommend the the Ultra linear taps on this type of build? Any advice about ultra-linear?

The OT:

http://store.triodestore.com/noname.html

Thanks

I can help with UL design.

UL works better for a bass amp than for guitar. It's just very clean.
Better suited to country and jazz than blues and rock.

You have to be very careful about voltages, both plate AND SCREEN !
The screens carry part of the load to the output transformer so some tubes just get abused when there's high screen voltages and current.
Good tubes with durable screens are critical. Consider using screen resistors if there are none, especially if it will be played anywhere near clipping.

Can you provide a link to schematic ?

If you are going to go UL than a Dynaco (or a good copy) is the way to go.
Dynaco transformers were used in a few Sunn amps in the '60s.
UL circuits were also used in many Fenders in the '70s and the Marshall Major for example.

What's your playing style, or other details about how the amp will be played.

rd

[bandade]

Here is the drawing for the transformer if you haven't seen it. http://www.triodeel.com/pdf/a470sdiag.pdf

I am altering the straycat layout drawing that is on Ceriatone by adding a tone control to the clean channel and solely using a 5AR4 in the rectifier rather than a solid state as well.

http://ceriatone.com/images/layoutPic/m ... iatone.jpg

I understand UL more from what you just said and think it would be better to not go ultra linear, I believe the A470 OT can be connected in triode or pentode as rather than solely UL based on the description.

My style of play is mostly 60's and 70's rock, blues, and modern country but i want to make this amp a higher gain than the past 2 i built. The past 2 are an 18 watt marshall style and a dumble style amps.

[rdjones]

Are these single ended outputs ?
The Hot Cat page is rather vague about the circuitry other than saying it's "class A".

Class A is kinda the opposite of ultralinear in a way.
(wasteful, inefficient, distorted)

I don't recommend UL being run class A, either true class A or the buzzword version.

They also mention using EL84s or EL34s.
Either of these "will work" for UL but may not be the best choice.

I'm hoping Andy Le Blanc will weigh in of this thread.
His treatise on screen grid treatment (while not specific to UL) is good general information
and the way the screens are used is what makes UL what it is.

RedDog (not dissin' on HotCats, really)

[bandade]

I wanted to use a Dynaco OT to add a little Wreck to it. I'm not sure how much of a twist it will put on it but i thought it was worth a try. i know Ken Fischer used Dynaco transformers for some of his amps.

Thanks for the insight.

[bandade]

I just got some feedback from Triode and they said that the A470 can be ran as Push-Pull UL or Push Pull. For standard Push Pull operation, you use the Blue/White & Blue wires for the Plate connections, and the Red for the CT power tap.

I will just run it push pull rather than UL

[rdjones]

Here is the drawing for the transformer if you haven't seen it. http://www.triodeel.com/pdf/a470sdiag.pdf

I am altering the straycat layout drawing that is on Ceriatone by adding a tone control to the clean channel and solely using a 5AR4 in the rectifier rather than a solid state as well.

http://ceriatone.com/images/layoutPic/m ... iatone.jpg

I understand UL more from what you just said and think it would be better to not go ultra linear, I believe the A470 OT can be connected in triode or pentode as rather than solely UL based on the description.

My style of play is mostly 60's and 70's rock, blues, and modern country but i want to make this amp a higher gain than the past 2 i built. The past 2 are an 18 watt marshall style and a dumble style amps.

The OT can used normally by just carefully insulating off the screen connections.
What drives the choice of the A470 ?
(Other than the fact that it's one of the classic output designs)

That design is triode strapping the screens for it's low power option.
You could just connect the screens to the UL taps in full power,
(through the switch) keeping the 1K screen resistors in place.
Voltages are real close to the limit for UL connection on EL34 but it would work with the screen resistors.

Also, the supply voltages are close to the ratings on the caps,
considering that the GZ34/5AR4 drops the least of the typical rectos.
If your line voltage runs high like it does here, you will be stressing the supply caps.
Just something to watch for.
Maybe choose a power transformer with 300 or 310 instead of 325
to make the UL work nicely and not push the limit on the EL34 screen voltage.

reddog (chasin' a 'cat)

[M Fowler]

You can also get a Heyboer version of that A-470-S from rjguitar.net as well.

I run those Heyboer OT's in my Rocket builds and I have used the Dynaco A-470-S as well but not in Ultra linear mode.

Mark

[rdjones]

I wanted to use a Dynaco OT to add a little Wreck to it. I'm not sure how much of a twist it will put on it but i thought it was worth a try. i know Ken Fischer used Dynaco transformers for some of his amps.

Thanks for the insight.

Here's a reference to info on Ultralinear operation for those so inclined.

http://oestex.com/tubes/ul.html

I'm curious which amps Ken used the UL tranny in ?
Surely not with the screen taps connected.

rd

[rdjones]

You can also get a Heyboer version of that A-470-S from rjguitar.net as well.

I run those Heyboer OT's in my Rocket builds and I have used the Dynaco A-470-S as well but not in Ultra linear mode.

Mark

I wonder if the A470 is an UL equivalent to our beloved Stancor A3801.
How much does an A470 weigh ? I'd like to compare these closer.

rd

[FUCHSAUDIO]

You can also do a switch to make it UL, Screen supply or triode pretty easily. Don't forget you can also use a screen resistor on the UL leads to limit current. 1-K 5-W all good. Still works as a UL (ac on screens) but with the current limiting of a screen resistor. Those old 6CA7's could handle no screen resistors, the new ones eh, not so much....

[M Fowler]

The Stancor 3801 weights 5.8 pounds and the A-470-S weights 7 pounds.


See page 5 of the Stancor catalog.

[rdjones]

The Stancor 3801 weights 5.8 pounds and the A-470-S weights 7 pounds.

See page 5 of the Stancor catalog.

Thanks.

So the Dyna transformer is heavier even though they are both "rated" at 35watts.

After looking closer, I also see that there's a (probably) more important difference beyond the screen taps.
The primaries are 4300 vs 6600 ohms.

rd

[M Fowler]

Yeah I should have mentioned that fact

Stancor is good for Liverpool or Express.

[FUCHSAUDIO]

Lets not forget that most audiophile iron is over-rated compared to guitar iron. The bandwidth on a guitar amp is limited at the low and high end, and we like saturation and overloading, which studios and audiophiles don't. More iron means less saturation more clean headroom and they wind for more bandwidth to ranges most guitarists can't hear......

That being said, my first dozen hand made ODS-50's had A-470's and 2 X EL-34's in them and they sounded huge....