where did go wrong here

[rudutch]

have a 5E3 (mission amp) that I wanted more volume out of...

took a 40w OT for FOUR EL84's and installed it

Primary was fairly straight foreword

1/2 the tubes, 1/2 the impedance, right?

hooked the 16 ohm lead to the 8 ohm jack
" ' 8 ohm lead to the 4 ohm jack
4 ohm unused

it works but the 6V6's got HOT in less than 2 minutes

do I have bass-ackwords impedance-wise??

[Kap'n]

A pair of 6V6's or pair of EL84's typically should have a primarly impedance of around 6.6-8K. A quad should have around 3.3-4K.

An OT is just a turns ratio, it doesn't have set impedences per se.

The example I always use in my head is a Vibrolux Reverb OT. Primary of around 4K, secondary of 4 ohm - about a 1,000:1 ratio. It also makes a reasonable Deluxe Reverb OT. With an 8 ohm load, the primary is around 8K.

Not sure what the turns ratios are on your transformer.

[chuckocaster]

i am no amp tech, but aren't you supposed to use 6L6s when you do that swap? isn't that what neil young's deluxe is?

[rudutch]

pulled it out and put the old one back in
%&^%#%$

[steve25]

Lets take this back to square one. why do you think that installing a 40 watt OT was going to give you more volume?
A output transformer is like a transmission in a car, it can not give you any more horsepower/wattage, the power supply must provide the needed volatge and current to do that.

[ziess]

FWIW, I've been running two old 5881s and a GZ34 in my Mercury magged 5E3 for months now... Doesn't even get much hotter than it did with 6V6GTs.
Sounds better (and louder) though.

[rudutch]

Originally Posted by steve25

Lets take this back to square one. why do you think that installing a 40 watt OT was going to give you more volume?
A output transformer is like a transmission in a car, it can not give you any more horsepower/wattage, the power supply must provide the needed volatge and current to do that.

I installed a deluxe reverb OT in my pro Jr (which had a very small OT) and there is a noticeable difference in both volume and lower freq. response, bigger is better here- but the parameters were very close.

I had this 40W (ha ha) from my Ashdown Peacemaker 40 but I know the primary impedance was off by 1/2.. thought I could fool it though the secondary... I was wrong (again)

my thought was...

taking the example of a blackface
tremolux @ 35W
band master @ 40W
Bassman @ 50W

all are using the same 6L6's but all have different rated outputs
I assume the difference is in the transformers

then again - you know what they say about assuming

[rudutch]

Plan "B" is to get the needed components to use 6L6's in the 5E3,
waiting for Bruce @ mission amps to get me the goods

[phantomman]

Originally Posted by rudutch

I installed a deluxe reverb OT in my pro Jr (which had a very small OT) and there is a noticeable difference in both volume and lower freq. response, bigger is better here- but the parameters were very close.

I had this 40W (ha ha) from my Ashdown Peacemaker 40 but I know the primary impedance was off by 1/2.. thought I could fool it though the secondary... I was wrong (again)

my thought was...

taking the example of a blackface
tremolux @ 35W
band master @ 40W
Bassman @ 50W

all are using the same 6L6's but all have different rated outputs
I assume the difference is in the transformers

then again - you know what they say about assuming

FWIW I think you're on the right track. However, the power supply needs to be considered as a singular entity......that is: rectifier, tranny, and filtering. These components all operate coincidentally and mutually to deliver ripple-free current to the tubes. Merely trading output trannies is not likely to increase the power at the final drive to any significant degree.

[Gris]

Originally Posted by phantomman

FWIW I think you're on the right track. However, the power supply needs to be considered as a singular entity......that is: rectifier, tranny, and filtering. These components all operate coincidentally and mutually to deliver ripple-free current to the tubes. Merely trading output trannies is not likely to increase the power at the final drive to any significant degree.

Well, not exactly. It depends upon what the power supply is to begin with. In a way the OT can be said to act kind of like a governor on an engine. In other words, IF you have a large enough power transformer to begin with then you can both increase and decrease output and headroom by swapping output transformers and even tubes. For example, in a BF Bandmaster the stock output transformer is a relatively small Lux-like affair. You can install a Super Reverb or Bassman OT and increase headroom and volume. However, while you gain extended range and volume you lose compression. So, it may or may not be a good thing sonically.

[phantomman]

Assumes facts not in evidence, Counselor......

Originally Posted by Gris

Well, not exactly. It depends upon what the power supply is to begin with. In a way the OT can be said to act kind of like a governor on an engine. In other words, IF you have a large enough power transformer to begin with then you can both increase and decrease output and headroom by swapping output transformers and even tubes. For example, in a BF Bandmaster the stock output transformer is a relatively small Lux-like affair. You can install a Super Reverb or Bassman OT and increase headroom and volume. However, while you gain extended range and volume you lose compression. So, it may or may not be a good thing sonically.

Fortunes have been won (and lost) on the basis of "IF". And it bears mentioning that any reliance of a hypothetical "reserve" built into a power supply to increase headroom at the amp's output tranny may compromise the integrity of the components that comprise that power supply thus contributing to premature (and possibly catastrophic) failure.

As a practical matter, Leo designed a certain amount of reserve into most of his amp designs. Thus, your contention does have some merit -- but only to the extent that the additional voltage or current draw does not exceed the absolute do-not-exceed spec of the individual components. Leo was, if nothing else, ultra-conservative in his design philosophy. To the benefit of us all.

[Gris]

Yeah, yeah, yeah, absolutely, all true. That was my point, that it all depends upon the PT. The Bandmaster is one amp that is routinely modded for a larger OT for more volume and headroom, though I like them just fine as is (seems to be a minority view for some reason).

[phantomman]

I'm fond of the Bandmaster as well -- I have three now (all stock). The Bassman OT swap is a popular (and prudent) mod for this platform. The SR tranny can also work although consideration must be given to its 2Ω secondary......perfect for driving a 4 x 12 cab.

[Gris]

I was playing my Tele into a stock '66 BFBM into a stock '63 BF/B BM cab last night (w/ pedals) in a studio session and the band leader stopped three times to compliment my tone - and this guy likes it LOUD. Those BFBM cabs are sensational. My '66 Gretsch cab is the same way. There is something about the compression inherent in those separated, foam-lined boxes that makes the notes pop out and bloom. I have said this before - the key to getting the best lead sound out of the BM is to slam it with pedal boosting... ;-)

[phantomman]

I'm down with that!

I've got my '66 Bandmaster mated to a '65 Dual Showman cab......



Smoothest and punchiest tones I've ever gotten out of a Bandmaster. Not quite the compression that a standard small-box 2 x 12 cab delivers but man -- this sucker is impossible to ignore. Very LOUD!

[ziess]

Most contemporary 5E3 PTs will more than likely have enough reserve current capacity to supply some extra tubes with enough juice, unless you're talking about modding an old one (!).

[steve25]

The increase in wattage when stepping up to a bigger OT has a small impact in overall volume, its the bigger sound stage and greater dynamic range/ less compression that gives the impact of more volume.

[cdw2000]

Originally Posted by rudutch

have a 5E3 (mission amp) that I wanted more volume out of...

took a 40w OT for FOUR EL84's and installed it

Primary was fairly straight foreword

1/2 the tubes, 1/2 the impedance, right?

hooked the 16 ohm lead to the 8 ohm jack
" ' 8 ohm lead to the 4 ohm jack
4 ohm unused

it works but the 6V6's got HOT in less than 2 minutes

do I have bass-ackwords impedance-wise??

Going back to the original email, I don't think anyone actually answered this:

1/2 the tubes equals TWICE the impedance. The quad of tubes are wired 2 by 2 in parallel. Removing one tube from a parallel pair equals twice the impedance you need to match to. SO you should have gone the opposite direction on the output side of the OT.

You would need to connect an 8 ohm speaker to the 4 ohm tap to properly match to the 6V6 PP pair. Or 16 ohms (two 8 ohm speakers in series) to the 8 ohm tap.

By connecting the OT as you did, you halved the impedance load to the power tubes when they were looking for twice the load. Therefore you ended up with a 4:1 impedance mismatch.

I know you've ripped it out by now and gone back to square one, but in theory it should have worked had you connected the speaker(s) to the correct tap. Sorry to be late with this info.

That being said, as others have said, it would not have bought you more volume... so probably not worth recreating. Once you connected to the correct tap the transformer turns ratio would have been equivalent to the original transformer so the voltage/current delivered to the speaker would have been the same.

[rudutch]

I had it ass-backwards.

Thanks for the clarification.

It's a mission spec'd OT, larger than I remembered

[yankeerob]

Originally Posted by ziess

FWIW, I've been running two old 5881s and a GZ34 in my Mercury magged 5E3 for months now... Doesn't even get much hotter than it did with 6V6GTs.
Sounds better (and louder) though.

Erm - so you've basically got a tweed Pro now - of sorts - when you say Merc'ed is that PT, OT, what? Coulda saved you a bit of dough if you'da emailed me - we're using Majestic now and they kick serious butt - BTW - the reason we never sorted those other units out for you is that we've been through three different manufacturers until we found these guys... email me dude... there's a lot I can tell you... cause...

Originally Posted by ziess

Most contemporary 5E3 PTs will more than likely have enough reserve current capacity to supply some extra tubes with enough juice, unless you're talking about modding an old one (!).

... is definitely not necessarily true - especially where heater current is concerned... maybe with the likes of Mercury but even then I wouldn't count on it - nobody in the business of building transformers is giving copper away - it's a tough world out there and making a decent buck is getting harder all the time...

Just to add a few more flies into the ointment - other factors - when selecting an OT - are the voltages you're running the output tubes at and the actual tubes you use... this is why some guys will tell you 'this brand works good with this amp' or ' I had good results with those' - that's also why the big manufacturers use a given brand or other - most of the time it's a compromise between price and what's going to give them a reasonably consistent result - I'll tell you for nothing that that's what I'm forced to do and that there's no hard and fast rules to calculating what's going to work best...

However - most amps that you might build will work in a fairly reasonable fashion if you stick to the values commonly published for a given tube type and that you can probably vary the load by as much as maybe 20-30% and get away with it - what it will sound like is the question and how long the OT will last is another... as a loose general rule - the higher the plate voltage the lower the load will likely want to be (the higher the load the more voltage you'll have across it for a given input and of course in output trannies this means heat - so you also have to be sure the power rating is in line with all of this) - this is why I well over-rate the OT's in all of my amps - not stupidly OTT but by at least 20% on smaller amps and 30% or so on bigger ones - this way I know the things can take the possible variations that might occur - and design the power supply so that it will operate in a generous safety zone for everything it's going to want to power - all of these things mean spending more money on the build - but I know they're gonna last and if they don't - I know damned well someone's done something stupid

I'm not trying to say I'm some kind of smartass - 'cause I'm not - I found this all out the hard way - and at some considerable expense - shame is it's not something you can pick up a book and read about because how could anyone be able to tell you what iron to use with what tubes? That a 5K load is gonna sound better with brand X tube than any other value... that you might order some 6K6 and 4K trannies and the dickhead manufacturer might just think f... it - I'll just wind all 4K ones - they'll never notice - never mind all the time you might spend wondering why you're short of output from the damned things... what you can do is stick to published values for a given tube type and then push the envelope a little here and there until you get it sounding the way you want...

That's why while it might be cool to mess around with this stuff - publishing any specific info with this regard is dodgy at best - and I'm not really meaning to pick on anyone with this regard - it's just a long way to the top if you wanna... you know... be a like me and build 'em for a living

[cdw2000]

All good points, Yankeerob.

I'll just add that as far as understanding what O.T. works best with a particular tube, reading the tube data sheets and learning to calculate load lines goes a long way.

The tube load impedance can have a large effect on how the circuit sounds as far as distortions levels, compression, etc.

There are many good sources of info on the web for those that want to read up on this stuff. Two years ago I went from a complete tube novice to building my own custom amp, using only info I collected off the web. Just to be clear, I do have a degree in Electrical Engineering and have been playing around with transistors and audio circuits for many years, so I wan't starting totally from scratch, but I think anyone with an aptitude for this could learn as much as I did just from the free resources on the web.

[rudutch]

I think (great way to start, eyh?) I am getting:

the Tone Volume mod kit that separates the channels
The 6L6 RC mod kit to run those tubes
NOS 5V4G Sylvania

The PT/OT iron stuff bruce supplies should be up for the task,
I also have:
40W OT for 4xEL84 *or* a deluxe reverb OT 22w

time to mess around and see what I can screw up

should be interesting

[yankeerob]

Originally Posted by cdw2000

I'll just add that as far as understanding what O.T. works best with a particular tube, reading the tube data sheets and learning to calculate load lines goes a long way. The tube load impedance can have a large effect on how the circuit sounds as far as distortions levels, compression, etc.

Thank you for broadening my post... calculating load lines is a very good point - this guy writes good stuff on the subject... I tend to heed a mixture of what he writes (which is absolutely correct if you're designing for hi-fi, some of it is a little too 'pure' for guitar amp design IMHO... YRMV...)

Originally Posted by cdw2000

There are many good sources of info on the web for those that want to read up on this stuff. Two years ago I went from a complete tube novice etc................ I think anyone with an aptitude for this could learn as much as I did just from the free resources on the web.

+1 on that - this guy's stuff is an excellent read as well... not to mention a good handful of helpful guys around here - 's all good!

[cdw2000]

Yup, I've used both of those resources.

Also:

http://www.geofex.com/Article_Folder...ndestructively

http://www.radioremembered.org/outimp.htm

http://tone-lizard.com/Mods_and_Odds.htm

http://www.geofex.com/tubeampfaq/taffram.htm

http://www.pmillett.com/technical_books_online.htm

[yankeerob]

Ahhh... even more to read... get stuck in boys (and girls)... you can never get enough info - some you agree with - some you don't - but you have to read it all to decide - nice one CDW!!!!...

[ziess]

Originally Posted by yankeerob

nobody in the business of building transformers is giving copper away - it's a tough world out there and making a decent buck is getting harder all the time...

No, fair point, but all the heater specs I've seen spec sheets I've seen for appropriate 5E3-type PTs are more than suitable for the job.
The Weber 25130 can handle 3A on the 5V, 5A on the 6.3V and 150mA on the HV windings, for instance. Ought to be more than enough.

Who are you using now?

[ziess]

Oh, and it's a Mercury '59 TDOT, the standard 6V6GT OT. Obviously it's running at an impedance mismatch but I like how it sounds and it seems like it can take it.