Output Impedance

[daringrebe]

Sorry if I am asking the same question that has been asked before, but I searched and really did not find the answer. This is a bit of a noob question. On my Express Clone. I am swapping the output trannie from the one that Ceriatone supplied to a Mercury Magnetics Axiom TW-KF-O. The Ceriatone is connected with the 5.2K impedance. What tonal changes can I expect if I decide to try the 6.6K instead. Thanks guys (and gals if there are any of you out there).

[jimipage]

what output tubes do you intend to use? (I'm guessing 6v6's?)
I built my Express with 6v6's at 6k6ohms. I found that reducing the 150k grid resistor (between stages 2 & 3) to 75k really helped keep the bass frequencies from overpowering the amp. Once I made that adjustment, it became a much better sounding amp.

[daringrebe]

I am using Groove Tubes e34LS or EL34M, I swap between them in my varius amps. Depends on my mood.

[guitarsnguns04]

you could wire in a switch..DPDT and be able to use either or

[Lonely Raven]

MM has a TW OT?

Hahaha, that's actually looks pretty funny typed out, but I bet you all understood me.

For real, they have a TW OT? Which OT is it based off?

[daringrebe]

Yep, and I am only purchasing them because of all of the MM Hype!!!! and the fact that I can send them back if I dont like the way they sound. ted Weber offered the best price on them. Here is a wiring diagram from MM

[daringrebe]

OK that didnt work twice, copy and paste the URL, it will open the diagram for you. Sorry for the double post

[Lonely Raven]

Got it, thanks for that. You said you got it at Ted Weber's page? I'll have to check it out...I need some transformers for a Liverpool I'm working on (someday...when I have both time and money....)

[martins3325]

..I am swapping the output trannie from the one that Ceriatone supplied to a Mercury Magnetics Axiom TW-KF-O.

Thats really interesting..and I dont doubt you..but its odd MM's site nor Webers seems to list that! Obviously they make as you posted the document..did you web order it? I would think that would be interesting news here if they were available..Ive never heard bad things about their transformers...though im not an amp builder just someone who wishes he was and likes to read up a bit.

[daringrebe]

I got the part numbers from Paul at MM, I had emailed them with the specs from teh Toneslut Heyboers, paul emailed me back in less than an hour with those p/n's. I originally thought that I would have to have them made and doubted under those conditions that I would go with MM. My email asked for a price to make the trannies to the Toneslut spec. MM wants $275 for the PT and 250 for the OT, So I shopped around to all the web people that I know sell them. Weber was the best price, now, everyone that I contacted also could not find the p/n's and list prices on MM website, but had to call to verify the price. Weber offerred the best deal.

['67_Plexi]

Sorry if I am asking the same question that has been asked before, but I searched and really did not find the answer. This is a bit of a noob question. On my Express Clone. I am swapping the output trannie from the one that Ceriatone supplied to a Mercury Magnetics Axiom TW-KF-O. The Ceriatone is connected with the 5.2K impedance. What tonal changes can I expect if I decide to try the 6.6K instead. Thanks guys (and gals if there are any of you out there).

I'll try and answer the question directly. If you are using EL34's and all other things are the same going from 5.2k to 6.6k you will lose about 4-5W of output power, but the 3rd and 5th harmonic content is around 20% less, which means the amp sounds less aggressive (or bity to think of a better word). 6.6K is higher than a typical text book value you would use designing using a load line method. 5.2k is closer with a 380V anode voltage.
I've seen some people use a 50W Marshall O/T which is around 3.4K. THey are designed for higher plate voltages and sound wicked harsh with an Express type circuit.
Personally I prefer the 6.6K and find it warmer and more balanced. The slight loss of power is hardly noticeable.

Alan.

[daringrebe]

Hey Alan....THANKS!! That is the type of info that I was looking for...Greatly Appreciated!

['67_Plexi]

Hey Alan....THANKS!! That is the type of info that I was looking for...Greatly Appreciated!

Very welcome.

[UR12]

but the 3rd and 5th harmonic content is around 20% less, which means the amp sounds less aggressive (or bity to think of a better word).
Alan.

Really??? So how exactly did you arrive at the figure of 20% reduction in 3rd and 5th harmonics. Is it measured, calculated.......................was it on one amp or an average of a bunch of them? Which trannys were you testing to get this figure?

I have built Express' with a few different impedances and I have to say IMHO it really depends on the tranny. I have had some that sound better at 5.2, some at 6.6 and some have measured even as high as 7.2k that sounded very sweet. Most tranny's are 20% tolerance so if you take the 5200 it can vary between 4160 and 6340. The 6600 can vary between 5280 and 7920. Even at 10% tolerance the 5200 range would be from 4680 - 5720 and the 6.6k from 5940 - 7260. Based on the tolerance I would say, if you can, try it both ways with the tranny you have (Tonesluts have both windings) and see which one sounds and feels the best to you. If you are going with a tranny that has only one winding then you are stuck with what you have no matter which way you go.

In regards to Mr Weber I thought all his kits came with his own trannys that are manufactured in China.

[daringrebe]

[quote="In regards to Mr Weber I thought all his kits came with his own trannys that are manufactured in China.[/quote]

Hi Dana, True in his kits he uses his own Chinese Trannies, But if you go to his site, he is also a dealer for MM and Heyboer. I have considered his kits, but if I did go with one, I'd personally leave out his trannies. I have not heard the best things about them. A buddy of mine built the Java from his site and ordered the full kit. It took him about 7 weeks of playing it, then he ordered Heyboers and was much happier with the amp.