Output Transformers..Does size matter??

[Toxophilite]

I have a couple of OTs that could work with my deluxe build. Humourously I had it up and running but it was super quiet
i checked all the usual suspects and then tried alligatoring another OT . Then it worked great!.
I was doing the surgery to remove the one I was originally trying when I noticed my speaker jack was shorting out...
Anyway
I have asked a similar question before but couldn't find my post for it


So I have these two OTs
Both were originally powered by a  pair of EL84 6BQ5


the smaller one with bell caps is 30 -1 and from a Hammond AO-43 originally powering an 8 ohm speaker


The bigger one with no bell caps is 27-1  and from a baldwin organ also powering an 8 ohm speaker


Can I make any assumptions as to their power handling and or frequency handling based upon their differences in physical size


Or is it on;y something I can figure out with extensive testing or through the use of gear that I don't have?

[HotBluePlates]

I have a couple of OTs that could work with my deluxe build. ...
Both were originally powered by a  pair of EL84 6BQ5
...
Can I make any assumptions as to their power handling and or frequency handling based upon their differences in physical size ...

 -  If you pass the same power through both, the one with the smaller core will probably restrict the very top/bottom of the frequency range first.
 -  The smaller core will saturate first.

This is a key element of tweed Fender amps.  Turns out these amps often had OT's with small cores, and would saturate sooner than a "hi-fi replacement OT" of today.  This restricted power passed to the speakers (which were sometimes undersized for the possible power output of the amp), focused frequency response towards the middle, and added a layer of distortion/compression to the amp.

The "hi-fi replacement OT" can make these amps sound "bigger and richer" with wider frequency response, and more dynamics.  Some player will prefer that.  Others will want the "focus, compression and reduced bass when driven" of the small-core OT.

Your two OT's are not radically-different sizes.  Maybe not much difference in performance between them.  Try both & see which you like.  You'll almost certainly need to hear the amp dimed with each to evaluate the difference.

[Blind Lemon]

That's why I lover the smaller tweed amps, smaller OPT and a pushed cathodyne PI. Nasty good.


BL

[shooter]

That's why I lover the smaller tweed amps

YUp

you want more, "headroom", clean, loud, use The HI-FI HBP talks about
you want more grungy, nicely distorted, use a 5F1 OT and bias a 6V6 near meltdown!

The OT is probably my 1st "mod" when I listen to a player describe; "what I want..."

[Toxophilite]

Thanks
I've always been definitely in the loud and clear/clean camp 
Sadly where I'm building the amp (in my apartment) I can't really play at a decent volume
Certainly not 'dimed' So no easy testing with both here
Normally I wouldn't get a deluxe much past 4.5-5 anyway as I want it too be clean


HotBluePLates,
when you said
"Your two OT's are radically-different sizes.  Maybe not much difference in performance between them.  Try both & see which you like.  You'll almost certainly need to hear the amp dimed with each to evaluate the difference."

Did you mean to say 'Your two OT's are NOT radically different sizes?'

[silverfox]

I have a couple of OTs that could work with my deluxe build. ...
Both were originally powered by a  pair of EL84 6BQ5
...
Can I make any assumptions as to their power handling and or frequency handling based upon their differences in physical size ...

 -  If you pass the same power through both, the one with the smaller core will probably restrict the very top/bottom of the frequency range first.
 -  The smaller core will saturate first.

This is a key element of tweed Fender amps.  Turns out these amps often had OT's with small cores, and would saturate sooner than a "hi-fi replacement OT" of today.  This restricted power passed to the speakers (which were sometimes undersized for the possible power output of the amp), focused frequency response towards the middle, and added a layer of distortion/compression to the amp.

The "hi-fi replacement OT" can make these amps sound "bigger and richer" with wider frequency response, and more dynamics.  Some player will prefer that.  Others will want the "focus, compression and reduced bass when driven" of the small-core OT.

Your two OT's are radically-different sizes.  Maybe not much difference in performance between them.  Try both & see which you like.  You'll almost certainly need to hear the amp dimed with each to evaluate the difference.

For those of you on the hunt for "MoJo", this is the essence, the secrete ingredients in the soup. While the technical books of the past could describe it in a dry fashion, the reality is: This OT, that tube and these capacitors in combination with the other components gave birth to a unique combination of harmonics...

Today I perused RCA 15, 1947 and contemplated- I wonder what that amp design would sound like with a Tube Screamer in front of it? Maybe good? Maybe bad! But, that's "MoJo". Can't say for sure but I think that's Calculus.

silverfox.

[Toxophilite]

I want a clear clean amp with a wide frequency range, that doesn't way a million lbs. like my super   and I would actually prefer a simplified 'dry' explanation which is kind of what Hot Blue plates was giving me. I find the 'mojo' to be far too subjective. It means different things to different people.
I was curious though if he had left out a word in his explanation.

[Toxophilite]

Well I wired the bigger (no bell caps) back in
It sounds good (at the pathetically quiet volumes i can play at 12:50 am.... )


I'll take the amp elsewhere and  give it a better work out tomorrow or the next day

[shooter]

I want a clear clean amp with a wide frequency range,

I built a "plexiish" preamp, mated to a pair of EL34s cathode biased, that dumped into a Marshall 100 OT
it's only 25W, but no player believes me, they also can't figure out how they can play fender twin clean and Marshall roar, by just adjusting guitar knobs.
the previous "rev" only got a so-so rating, OT and speaker change and 2thumbs up.  Silverfox's mojo calculus?

[Toxophilite]

I'm not sure what you mean by 'rev'
Sounds like you changed some parameters and got the sound you like! Yay!

I was just hoping to keep the discussion along technical lines rather than venturing into subjective realms
I feel the magic/mojo is in the player, not the gear. Though gear is obviously very fun to play with.
The only quest I'm on is for a small portable amp that can provide totally clean sounds at gigging level. I know and have already found the sound I want long ago. Building amps is really more of a fun sideline to making music
I think engineers use 'dry' language because then they have terms that all understand equally
"Tone' 'mojo' and similar subjective expressions mean different  things to different people.

I have another question.
If I put a Vibrolux OT in this deluxe build( it seems to have the poop to handle 6L6Gcs if I wanted)

if the specs are mostly the same (Hammond Transformer) is it a big deal to run a vibrolux OT with 6V6s provided the amp is biased for the 6V6s?

Thanks

[SoundmasterG]

I'm not sure what you mean by 'rev'

Rev usually means revision.

I have another question.
If I put a Vibrolux OT in this deluxe build( it seems to have the poop to handle 6L6Gcs if I wanted)

if the specs are mostly the same (Hammond Transformer) is it a big deal to run a vibrolux OT with 6V6s provided the amp is biased for the 6V6s?

Thanks

The impedance match is very important also in addition to the bias. An OT meant for 6V6 will usually have 8000 or 10000 ohms primary impedance and an amp meant for 6L6 will usually have 4000 ohms or 6000 ohms. You can make things match up the same if you use the appropriate secondary tap to connect the speaker. For example, if you have an 8000 ohm primary impedance transformer meant for 6V6, and you connect the 4 ohm tap instead of the 8 ohm tap to the speaker, (if the speaker is an 8 ohm speaker) then you end up with half the impedance that the speaker is seeing, which is the same as using a 4000 ohm transformer. So conversely, with your example, using a Vibrolux transformer with 6V6's, you need to connect the speaker to the appropriate tap to get double the impedance. So if your speaker is an 8 ohm, connect it to the 16 ohm tap, and that will be the proper match for that setup. It will likely work fine when mismatched and might give interesting tones, but in some extreme cases, usually when much higher voltage B+ is in the amp, then you can end up with arcing or shorting problems inside the transformer with a large mismatch.


Greg

[Toxophilite]

Thanks very much!


I think though with this one which has 4000 primary impedance  and a secondary of 4ohms as it's runs two 8 ohm speakers in parallel
That one could just plug in the 6V6s and hook up a 8 ohm speaker as all the specs except for the size and wattage seem to be the similar to a deluxe reverbs
(of course they also make a multitap model)
http://www.hammondmfg.com/pdf/EDB1750J.pdf

[HotBluePlates]

HotBluePLates,
when you said
"Your two OT's are radically-different sizes.  Maybe not much difference in performance between them.  Try both & see which you like.  You'll almost certainly need to hear the amp dimed with each to evaluate the difference."

Did you mean to say 'Your two OT's are NOT radically different sizes?'

Yep, distracted typing got me! Edited above.

[shooter]

I was just hoping to keep the discussion along technical lines

I'm a "if you can see it on a scope it's real" guy.  And that's what I did, took a so-so amp, changed OT, minor gain tweaks and wound up with the amp I was shooting for.  and sizemattered, from a 40W OT to a 100W OT

[HotBluePlates]

I want a clear clean amp with a wide frequency range, ...

You may want a large OT.  "Large" means something different at 5w output than at 100w output.

As you attempt to transfer more power from primary to secondary through a transformer, more energy is magnetizing the core.  As B-H curves show (top-right two pictures here), more lines of flux are created until you hit the knee of the B-H curve.  If it reminds you of the knee of a compressor curve (or how a pentode's plate current doesn't increase much as plate voltages rises higher than the "knee" of the curve), that's no accident.

Normal operation would be below the knee of the B-H curve.  Above the knee, you're applying lots more power to the primary, but getting little change of power at the secondary.  That's compression.  Probably also distortion.  And all generated in the OT.

So bigger power through-put requires a bigger core to handle the magnetizing force.

Low frequencies require greater magnetizing force than high frequencies.  Not sure you've seen them, but ships & aircraft have a.c. power at 400Hz rather than 60Hz.  The reason is the transformer cores are much smaller for the same power through-put at the higher frequency (saves weight/space, which matters a lot on a plane or ship).

So the lower you need full power, the bigger your OT core must be.  Hammond offers hi-fi transformers which will manage their full power rating down to 30Hz.  These will be bigger/heavier than Hammond's "guitar replacement OT's" that don't need full power down so low (meaning also "restricted bandwidth").  It's hard to directly compare core sizes among manufacturers (weight would be easiest, but we also often have to guesstimate core area as mounting holes & coil size are given in lieu of all 3 dimensions of the core stack), but you can get a feel for which are bigger/smaller for the same claimed power.

The smaller OT core won't do "as low, as loud, for the same distortion".  You might even notice 50's tweed-style OTs tend to have smaller cores even for the same claimed tubes/output power as a "60's style" OT.

But what you like best is often very much about your preferences and trial & error.

[Toxophilite]

Thanks for the clarification and further information HBP
That helps
And Shooter I understand what you were saying now and appreciate the example
Thanks!

[Tony Bones]

I just want to reiterate the important point made by HotBluesPlate: OT size is mainly a function of the lowest frequency that you want to reproduce. A 20W guitar amp can have a much smaller OT than a 20W hifi amp because it only needs to go down to 80Hz. That's a full two octaves less demanding than the usual spec of 20Hz for hifi. It makes a huge difference (no pun intended.)

If you want clean and clear, try running a lower load. 6V6 or EL84 into 5k can be surprising bold without getting dirty. The same tubes into 10k load will bark and snarl at lower levels.

[Toxophilite]

I understand that Hifi OTs need to handle lower(and higher) frequencies than guitar amps


As to the load,do you mean using a different impedance speaker so I get a different reflected load on the primaries? (excuse my technical ignorance if I'm wrong)
Right now I have an 8 ohm speaker
If I'm totally wrong if you could explain further that would be appreciated

[Tony Bones]

I was speaking in general terms. Like if you had nothing to start with and could pick from anything that's currently available.

In your case, with given OTs and speaker, you can't adjust the the load to the tubes. (Unless there are different speaker taps on one or both of the transformers, but I didn't notice them in the photo.) Compared to 8 ohms, a 4 ohm load on the secondary would present half the load at the load at the primary - what the tubes see.

Think of a transformer as a set of gears with a specific set ratio. When you ride a bike with a lot of different gears you choose one that presents the right load to your feet depending on whether you're riding up hill or down hill. An output transformer is usually just one gear (unless it has taps for different speaker loads - 4,8,16 ohms.) Different tubes work "best" with different loads (gear ratios) so transformers are wound to present different loads to the tubes given a specific load at the output (the speaker.) It's possible that the two transformers you have are wound differently if they were meant for different applications; maybe different tubes or maybe different speaker loads. There must be a web page of YouTube video showing how to measure the winding ratio of output transformers.

As for the bike analogy, it's not perfect, but hopefully it helps you understand a little better what a transformer does.

[Ed_Chambley]

Consideration of plate voltage is necessary if you want to get optimum output.  Optimum meaning the highest wattage with lowest distortion.  For instance,  the 6v6 when used in a Hammond organ tone cabinet you will often find a 10k to 8ohm for the main speaker.  An inductor input will lower the voltage by a factor . 88 to. 9 and the inductor will smooth the ripple to the plate as well as screens.  Viewing the datasheet willl provide your operating conditions. Same tube with increased plate voltage in a 5g9 will have a 8k to whatever the speaker load your turns ratio determines.  Keep pushing up the voltage to blackface voltages and you will have a preferred 6.6k load. With the 3 differring designs,  you will normally get the most clean watts from the inductor input,  but it is very close to the blackface.


No mojo here. Of course the wattage off the ab763 wilbe more,  rewiewing both on a 2 channel scope shows that the hammond will provide more clean watts.


If you review the KT66 data,  and consider it fot your Super you would probably run 4k pp.  The original Jtm 45 used a HiFi Radiospares multitape 6k6 load.  I can only guess as to this being chosen be ause they prefered the sound. 
 

[shooter]

As B-H curves show

as an aside, if you place your head in then out of a large flux field, say north of 1T, you get a "3 beer buzz" the faster you do it.  do it to fast and you will black out!  You learn very fast, to move slowly into and out of large condensed flux lines

[Tony Bones]

Consideration of plate voltage is necessary if you want to get optimum output.  Optimum meaning the highest wattage with lowest distortion. 

The Siren Song of maximum undistorted output has seduced so many away from things that matter more. So many.

[Ed_Chambley]

Consideration of plate voltage is necessary if you want to get optimum output.  Optimum meaning the highest wattage with lowest distortion. 

The Siren Song of maximum undistorted output has seduced so many away from things that matter more. So many.

Sure does. We are building guitar amps. For instance the stock Princeton Reverb ot will saturate fairly easily, but it is no problem if you like it. It is actually a benefit if you like it.
The wattage war is over as stage volumes have decreased and is there really any noticable difference in 50 watt Bassman and a 40 watt Bandmaster playing the same cab?
The op topic of wanting a clean amp with headroom takes this path. For instance, if you prefer firm bass response and a clear clean amp with a wide frequency response you are simply going to need an ot that is heavier with more I and E. Even then the circuit has to be able to deliver a clean clear signal.


So is it really clean we want. The OP likes and considers his Super Reverb clean. I can appreciate that, but later designs added a UL OT and increased clean watts which players do not embrace and referred to as sterile.


But we are writing about the Output Transformer. Ken Fisher selected a 6k load for 2 EL34 in push pull, but the trainwrecks were lower voltage than Marshall who chose 3.4k for the same pair of tubes.


That is why I mentioned the jtm 45. A guitar amp with a HiFi output iron. I have one and will changing the taps change the amp. Sure, but you will have to get it loud to hear much difference. Surly larger iron contributes to cleaner output, but so do transistors.


If you are wanting overtones and increased harmonics max clean is certainly not the object, so therefore lowering headroon by lowering voltages and increasing your turns ratio will help, but that in itself is not everything either. Less dampening and adding another gain stage or even using an old Blackplate preamp tube to increase the second harmonic will change thngs alot.


No magic bullet with your OT, but it does contribute. So the better your load is matched the potential for clean output is incresed. This is very apparent simply by putting larger wattage iron on a Princeton. It will play cleaner at a higher volume, but you will sacrafice the comperssion of the stock unit. A lot of guys find this when using the Allen higher wattage OT. Increasing the first filter cap will tighten bass as well. I guess it has to do with what you want out of your amp.

[sluckey]

The Siren Song of maximum undistorted output has seduced so many away from things that matter more. So many.

Not so much in the guitar amp world. The voicing of the amp has become a major part of the sound.

[Toxophilite]

Yeah I'm not really seduced by more volume volume volume
I want a clean stage sound(and not the half distorted sound that many think constitutes 'clean) at a more reasonable size and weight. My super weighs 85 lbs


I believe Leo Fender and his engineers were trying to design louder cleaner amps for most of the of the 50s 60s and 70s. They weren't trying to design the ultimate distortion machine.


My Super happens to be one of the 70 watt UL 'sterile" models
I like it and have played it live, in the studio etc etc for the past 25 years .
People always tell me how great it sounds and players are surprised that I'm playing one the 'undersirable' models.
I feel the important thing is what you do with your instruments, What you choose to play and the attention you give to getting what you want.
Amp building is fun and beats the hell out of buying a vintage deluxe for $2500 especially when I can make one for $100-150 using donor parts got on the cheap from thrift stores garage sales etc.. Viva recycling!


I really appreciate all the responses and information

[Tony Bones]

The Siren Song of maximum undistorted output has seduced so many away from things that matter more. So many.

Not so much in the guitar amp world. The voicing of the amp has become a major part of the sound.

You'll find nobody that agrees more than me, it just seemed that Ed's post was going down that road.

I'd even argue that the voicing of the amp mattered to Fender and Marshall way back in the 50s and 60s. I do recognize how Fender amps evolved from the very first up through the silverface to produce "more clean power", but at least when Leo was at the helm clean power was no good if it didn't sound good.

[Ed_Chambley]

Yeah I'm not really seduced by more volume volume volume
I want a clean stage sound(and not the half distorted sound that many think constitutes 'clean) at a more reasonable size and weight. My super weighs 85 lbs


I believe Leo Fender and his engineers were trying to design louder cleaner amps for most of the of the 50s 60s and 70s. They weren't trying to design the ultimate distortion machine.


My Super happens to be one of the 70 watt UL 'sterile" models
I like it and have played it live, in the studio etc etc for the past 25 years .
People always tell me how great it sounds and players are surprised that I'm playing one the 'undersirable' models.
I feel the important thing is what you do with your instruments, What you choose to play and the attention you give to getting what you want.
Amp building is fun and beats the hell out of buying a vintage deluxe for $2500 especially when I can make one for $100-150 using donor parts got on the cheap from thrift stores garage sales etc.. Viva recycling!


I really appreciate all the responses and information

I remembered you having the UL Super and I have played one myself and did not understand the sterile comments, just heard them.  I have also heard older players say when the miniature 12Ax7 replaced the Octal preamp, the tone became sterile.  These are things I have heard, not things I believe.


I have a UL design amp, similar to the Route 66 except I used the Iron that SUNN used and KT88's.  Point being is I do not consider it sterile either.  The OT I used is an A470s which is a Dynaco replacement. Transformer specs are: 4300 ohms CT primary with screen taps, 4,8 and 16 ohm secondary. 20 Hz to 20 KHz response at 35W, within 1 db, 30 to 15 KHz at 70 watts.


If you notice, the more watts the less the frequency response.  I am actually running KT120 in it right now and it produces almost 90 watts.  The response is incredible and the bass has no flab.  Clean, you bet.  I do not find UL to be sterile, but I also like a clean amp as well.  This OT is not pushed enough to even come close to saturation.  If you prefer a Tweed tone, you will not like this one unless you are needing some serious firmness.

It gets some interesting harmonics from the EF86 preamp tube which does have a triode pentode switch on it.  In triode mode it simply is clean for days.  Love the amp.  My point is the Output Transformer in this amp probably has the largest affect on tone than any other amp I have simply because the load is matched well and it handles the wattage.  The amp certainly is not for everyone and is not forgiving at all, but if youtruly want to know how you guitar sounds it will let you know.

[Ritchie200]

The wattage war is over as stage volumes have decreased

What?  Since when!!!!


I too like the UL design as in my case it has so many different textures and plays completely different to any other Marshall - or any other amp period.  It is something that you almost need to experience as it is hard to describe. It's certainly more full bodied but it reacts different when you push it.  Kind of a compressed feel like you have an animal caged thats trying to get out, and will scare the crap out of you at the same time.  It has nothing to do with volume although you have to be humping pretty good to get into this territory.  Some people say it has to be just like any Marshall that just starts to get into distortion.  Nope, not even close.  It's more saturated and complete, more musical.  This is also an amp that was used for bass, guitar, and PA with just slight changes in the pre.  Very wide range of response, and did all quite well.  blah, blah, blah, I'll shut up my fanboy self now...

Toxo, thats my technical description.  Do you want my subjective description now?! 

Jim