TO20 Transformer

[AllEars]

Hi,

I'm trying to source an output transformer upgrade for my Blues Junior. I can't see one on the Hoffman site and unsure about the Allen Amps TO26... wether it's a similar transformer or not. Can someone tell me where I can buy one?

[Blueboozer]

What kind of upgrade? More impedance choices? More output wattage? Different tone?

[dude]

The Allen OT will work fine, as long as the holes match up with your chassis, check the spacing on Allen Amps

[DummyLoad]

reference for the dimensions of your OEM part.

http://www.hammondmfg.com/pdf/EDB1750F.pdf


the Allen TO26 has 3-1/8" mounting centers, the OEM blues jr. part is 2-13/16" mounting centers - you will need to drill at least one hole with the Allen TO26


--pete

[JB]

That Hammond 1750F is a good drop in replacement.  They make two versions, one stock the other with additonal secondary taps.  It has the spade connectors on so no soldering.  I've put one in my Pro Junior.  The difference is in the bottom end, more of it and tighter.
The primary dc resistance is a little different to the orginal Fender part so you may need to rebias.  However if your Blues Junior is stock then you really should mod it anyway for adjustable bias and set it for something lower than the crazy hot point that Fender run the EL84's at.
 

[AllEars]

That Hammond 1750F is a good drop in replacement.

But is it as good?

Yes I am modding the amp according to Bill M's tried and tested mods, including adjustable bias....that's a no brainer really, might even change the valve sockets so I can swap in 6V6 for another sound.

I hear a better output tranny will give a bit more output, improve overall clarity and better bass which I find on the muddy side right now.

[JB]

That Hammond 1750F is a good drop in replacement.

But is it as good?

Dunno, haven't tried the Allen.  You'd have to ask someone who has tried both, maybe the Hammond is better than the Allen?
I've swapped it in and out a couple of times, with no drilling or soldering it's easy.  Definitely improves the bass.

[AllEars]

I'm trying to source an output transformer upgrade for my Blues Junior. I can't see one on the Hoffman site and unsure about the Allen Amps TO26... wether it's a similar transformer or not. Can someone tell me where I can buy one?

Oh...I didn't mention the transformer I'm looking for is a TO20 made by Heyboer.
Or does anyone know if the TO26 (or Hammond 1750F as JB mentioned) are much different?

[jordan86]

Both Allen OT are great. I don’t think David has any TO20’s in stock though. Quickest way to find out is to call him. TO20 is indeed made by Heyboer for David Allen. It is plenty sufficient and will be an upgrade. No extra drilling. I have one in my Princeton.

Also...It’s still not clear what you are trying to do, so asking for blanket OT suggestions on random models and then wanting helpful feedback on what’s “better” isn’t too effective. I think what you are asking is not about a better transformer but a bigger transformer.

If you just wanting improved tone/power get a 20W Deluxe style OT. They are generally cheaper than a Princeton or BJ replacement. Hammond makes them - 1750H. Mojotone also sells one made by Heyboer.

As a side note...A deluxe sized OT will require you to drill a new hole in the chassis.

[jordan86]

If your blues jr is muddy, I’d doubt it’s the OT to blame. I’d try some fresh power tubes. Or a speaker upgrade.

But yes, and bigger OT will give more power, improved low end, and just help your small amp sound a TAD bit “bigger”.

[acheld]

I have several BJ's, and have modded them all according to BillM and others over the years, as well as building a Hoffman BJ.

To my ear, the TO20 makes no difference compared to stock when playing in a practice environment.   Don't get me wrong, it sounds fine and is not way overpriced like MM.  And David Allen is good to customers.   But better than Hammond?  I don't hear it.

By the way, the Hoffman BJ conversion is the most stable of the BJ's out there -- no surprise there I suppose.

[shooter]

does anyone know if the TO26 (or Hammond 1750F as JB mentioned) are much different?

as a tech, No
It's 90% a musician subjective, spend your time and money deciding speaker differences, you'll be way ahead in the end

[AllEars]

Thanks for the replies, I suspected speaker and was on my list too.

[jordan86]

Nothing wrong with upgrading iron if that’s what you want to do. It will likely improve your low end more than your highs. I’ve read some of the cheap fender iron is actually brighter than say a nice Heyboer/Allen OT. Many report his OT to be an improvement but also that they are warmer than stock.

I’d start with fresh EL84s. Then possibly a speaker if you want more top end.

[AllEars]

I've had 2 BJ's, first one was an older tweed in chipboard cab, I gave it to my Son and he loves it for practice, it was a good little amp from memory, didn't quite cut it for me, was too muddy.

The one I have now is a Custom Shop amp I bought from Fender when I was a dealer. Has the yellow PCB, Fender (Eminence) special design speaker and a solid maple lacquered cab. Looks beautiful, sounds louder than my first, brighter and not as muddy. I attribute the brightness and tightness to the cabinet. I really like it because of it's size, is loud enough to gig with, but I can use some more bottom end and a little more volume. Half way through the Bill M mods right now, still waiting for some parts to arrive, then I'll give it a crank.

I like the sound of the EL84's, (love the sound of an AC30 when cranked, maybe I should build one...nah...too heavy!!)  planning on acquiring (or build from scratch) a Deluxe Reverb for the sound of the 6V6 tubes.
 
I already have a Vibroverb with the Altec Lansing speaker, worth a mint if I were to sell, NEVER!! It has the sweetest sound you've ever heard from an amp!

Tech by trade, I gave up the iron for a music shop and have since lost touch with the tech side of things. Haven't played or been in the business for over 10 years now. Starting over. What you guys have found will help me decide which way to go.

[AllEars]

Nothing wrong with upgrading iron if that’s what you want to do. It will likely improve your low end more than your highs. I’ve read some of the cheap fender iron is actually brighter than say a nice Heyboer/Allen OT. Many report his OT to be an improvement but also that they are warmer than stock.

I’d start with fresh EL84s. Then possibly a speaker if you want more top end.

Cannot get through to Heyboer from Australia, "Safari can't ope page". Have emailed Allen but still waiting to get a response. That was a week ago.

Pre-amp tubes are GT's (original in amp when bought) outputs are EI (Yugoslavia) old stock I used as replacements back then and none of them have had much use so I don't think it would be tubes.

Speaker, yes. Should I go for a Celestion G12M Greenback ??? or the Jensen???
The Eminence Cannabis Rex is getting good raps....

[acheld]

Despite the hype, my personal experience with this amp is that the OT transplant makes no difference to me -- I do not hear it.   Tried several different OTs.

Hammond is reliable and available.  And cost effective.

The speaker absolutely makes a difference.  BJs tend to have fairly bright highs, and not much bass.  I personally love the Cannabis Rex for this platform.  It takes the rough edges off of the high range, and a bit (slightly) more bass.  I've also tried Celestion Blue, Gold, both with good result, but I just like the Rex.

Truth is, it's all in your ears . . .

[AllEars]

So I've just completed Bill M's mods and it certainly is a different beast now!

Did the Twin Stack and Tone Stack mods, addition of a bias pot, 100pf capacitor across R30 and removed C10. I replaced R25 (7.5K) with a 10K pot for presence control but it doesn't do much, reckon it needs to be 25K. The original OT will stay.

Cranking up the volume all the way gives a nice, fat and juicy OD. Bring it back and the master up and it's bright and clean. The tone controls have a much bigger range. Still very bright and anything over 4 is really sharp. Bass is not as muddy; setting the bass control appropriately gives me a reasonable result.

So now I'm considering a speaker upgrade. After reading several reviews it seems that Celestion, Swamp Thang and Texas Heat add another flavour, where the Cannabis Rex not so much, but better overall response...or at least that's the impression I get. I'm leaning towards the Cannabis Rex.

[thetragichero]

yeah i picked up an early 2000s blues junior for peanuts because it needed some repairs. once repaired, i converted the unused triode to a cathode follower prior to the tone stack along with changing the tones stack to twin reverb values (i also changed a 47uf cathode bypass capacitor to a more fender-like 22uf but that was mostly because it was the only electro cap that hadn't been replaced). dynamite little amp. biased it up (had previously been modified to adjustable fixed bias) and ended up flipping it to the other guitarist at church who was in need of an amp
for what it's worth, i've built a ~20w 2x 6v6 build with blues junior iron purchased off reverb and it works just fine.... i'm of the opinion that it's only worthwhile to change transformers when there is something wrong them or trying to get different parameters (like switching from 6v6 to 6l6 and needing a lower primary impedance)