Upgrading the OT on a 5E3

SunDevil

Gents,

I'm continuing to play around with a 5E3 clone and next I'd like to try running some 6L6s with an GZ34, but retain the ability to run it for 6v6s and a squashier rectifier

I'm planning to upgrade the cathode resistor and bypass cap to 10W and 50v accordingly

The PT is up to snuff but I have an issue with the OT

I've read that it would be good to run the amp with it's 8k Primary OT a step higher on impedance to compensate for the lower resistance of the 6L6, but I've just found that the OT only has an 8 Ohm tap (frustrating, as i'd be told that it had 4,8 and 16)

I don't have the option to run into a 4 ohm load, so how likely am I to see fireworks if I run the 6L6 / GZ34 combo hard into an 8 Ohms?

This is the current OT:  

http://www.tubeampdoctor.com/en/shop_Output_transformers_Output_Transf_for_Fender/Output_transf_for_FenderTweed_Deluxe_5E3_1582

If I were going to replace the OT (either in advance or after the above fireworks) would I be better off going for a 5e5 OT or is there a smarter way of doing this?

Searching for this stuff, I keep coming to links about the Lazy J 20 being able to run both combinations, so how is Mr Hoff doing this?  ..is it better to build for the 6L6s (as I understand, it's lower risk to the OT if its sees a lower than matched impedance?)

Baz

crunchman

Not sure how Jesse does it, but it sounds a lot better with 6L6/GZ34.

hotpickups

Jesse's OTs are custom built to his spec so you won't get one of them off the shelf Id imagine

SunDevil

Thanks @hotpickups - I'm neither a Lazy J protractor or detractor (let's not start that one up again!) :-)

I'm not trying to make a L20, just trying to understand the mechanics / electronics and understand if I need to replace the OT to run it with 6L6s or whether it'd be within tolerances as is?

If this does require an OT change, then It looks like the Hammond 1760H might be the ticket - 6.6k primary which should be roughly right for 6L6s with the EZ34, but I don't know how that would sit with 6V6s and 5Y3?

ESchap

I did the same mod recently to an Ampeg J20 which is basically the brown Deluxe 6G3 circuit.  It's fixed bias so I was able to just adjust the bias for the 6L6's. Same problem as you though with the OT as it only has an 8ohm tap. I had a 4 ohm speaker and compared it to 8ohm and frankly there was next to no difference, perhaps a little more volume with the 4ohms and a tad "tighter in the bass.  I stuck with 8 ohms.  I much prefer the amp with the 6L6's, makes it a lot more versatile. 

SunDevil

Thanks @ESchap - sounds like it's worth me giving that a try before looking at a new OT then - I'll dig out the rubber boots and the fire extinguisher!

RiftAmps

The Lazy J20 uses the Mojotone 5E3 TX set, OT is 8k - http://www.mojotone.com/amp-parts/Transformers_1/Tweed-Deluxe-Output-Transformer - see pics below.

The TX set in your amp will quite happily run GZ34/6L6s, you just need to upgrade the bias resistor+cap to 270r/10w and 25uf/63v.

SunDevil

Hey thanks @RiftAmps  - much apprecaited!

Ossyrocks

RiftAmps said:

The Lazy J20 uses the Mojotone 5E3 TX set, OT is 8k - http://www.mojotone.com/amp-parts/Transformers_1/Tweed-Deluxe-Output-Transformer - see pics below.

The TX set in your amp will quite happily run GZ34/6L6s, you just need to upgrade the bias resistor+cap to 270r/10w and 25uf/63v.

Lazy J20 = Standard Mojotone "off the shelf" TX set? Really?

Any issues with current draw and filament windings running 6L6's ?

Rob.

RiftAmps

Ossyrocks said:

RiftAmps said:

The Lazy J20 uses the Mojotone 5E3 TX set, OT is 8k - http://www.mojotone.com/amp-parts/Transformers_1/Tweed-Deluxe-Output-Transformer - see pics below.

The TX set in your amp will quite happily run GZ34/6L6s, you just need to upgrade the bias resistor+cap to 270r/10w and 25uf/63v.

Lazy J20 = Standard Mojotone "off the shelf" TX set? Really?

Yup, but he uses them because they produce the tone that he's after, it's irrelevant if they're 'off the shelf' or not. All three J20s that I've had across my bench have used the same TX set.

Ossyrocks said:

Any issues with current draw and filament windings running 6L6's ?

Jesse uses a fan to cool the PT, where I just use a beefier PT, so read into that what you will.

SunDevil said:

Hey thanks @RiftAmps  - much apprecaited!

No problem, you might want to upgrade the 5K1 resistor in the B+ rail to a 4K7 2w job also.

exocet

Mojotone Txs are made by Heyboer - very good transformers that are used by many other amp manufacturers.

http://www.heyboertransformers.com/tubeamps.shtml

Ossyrocks

@RiftAmps Thanks for the info. @exocet I'm sure they are fine transformers.

I suppose I just don't understand where all the money is in them. My favourite amp is a Gartone 5E3, I've just got back home from rehearsal with it in fact. It has an antique Victorian pine cab, paper in oil caps, Celestion Blue, all NOS glass inc. GE power valves, Mercury Magnetics transformers. It sounds stupendous and I bought it directly from Martin Garton for £800 as a customer trade in/upgrade.

I have yet to try a J20 though.........

Rob.

SunDevil

Rob - he's charging £1,750 now for the same - you got a great deal!

Ossyrocks

SunDevil said:

Rob - he's charging £1,750 now for the same - you got a great deal!

£800 Secondhand. 

I'm I'm sure Martin is suffering from the poor exchange rate. He buys ALL his transformers from Mercury. 

He makes a damn fine sounding amp.

Rob

SunDevil

Ossyrocks said:

I'm I'm sure Martin is suffering from the poor exchange rate. He buys ALL his transformers from Mercury. 

..I imagine that's not cheap, but surely we're already on standard Inter-galactic Trade Tariffs with other planets?

(..sorry, couldn't help myself there!)