Hi.
I am starting a build for Sunn Model T clone.
I want the preamp and the poweramp to be as similar as possible.
So:
Preamp 3x12AX7
PA: 4x6550 Ultralinear
The first step as always, the transformers.
Yesterday I thought that I will give up on this one, as its damn expensive to get the original OT and PT.
But I don't really need the mercury transformers (I am also in EU) if there is another way.
So I am looking at Marshall Major 200W schematic at the moment.
To me it looks like I could use its Ultralinear transformer.
Here is the Major
http://elektrotanya.com/PREVIEWS/63.../marshall_major_1967u_lead_200w_sch.pdf_1.png
Here is the Sunn Model T Super (second gen)
http://music-electronics-forum.com/attachments/25674d1381533140-sunn-model-t-2nd-gen_ed.gif
Here is the Sunn Model T (the first gen)
http://www.prowessamplifiers.com/schematics/post/sunn_model_t.pdf
TAD has the Major OT in stock for 170€ and this is not bad price at all.
What do you think about this OT?
Output transf. for Marshall Major 200 W Ultralinear - Output Transf.
It has all the needed outputs. It uses different tubes, but 6550 and KT88 should be very similar as far as the transformer requirements go.
Still looking for the PT.
I am starting a build for Sunn Model T clone.
I want the preamp and the poweramp to be as similar as possible.
So:
Preamp 3x12AX7
PA: 4x6550 Ultralinear
The first step as always, the transformers.
Yesterday I thought that I will give up on this one, as its damn expensive to get the original OT and PT.
But I don't really need the mercury transformers (I am also in EU) if there is another way.
So I am looking at Marshall Major 200W schematic at the moment.
To me it looks like I could use its Ultralinear transformer.
Here is the Major
http://elektrotanya.com/PREVIEWS/63.../marshall_major_1967u_lead_200w_sch.pdf_1.png
Here is the Sunn Model T Super (second gen)
http://music-electronics-forum.com/attachments/25674d1381533140-sunn-model-t-2nd-gen_ed.gif
Here is the Sunn Model T (the first gen)
http://www.prowessamplifiers.com/schematics/post/sunn_model_t.pdf
TAD has the Major OT in stock for 170€ and this is not bad price at all.
What do you think about this OT?
Output transf. for Marshall Major 200 W Ultralinear - Output Transf.
It has all the needed outputs. It uses different tubes, but 6550 and KT88 should be very similar as far as the transformer requirements go.
Still looking for the PT.
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The reason Marshall have the sound they have is due to the bias setting. The transformer you have chosen, I think will be as good as any. Could you not have one made for less cost at a transformer winding company nearer your home? The specification is good and can be readily manufactured. Just a thought.
Dynaco- The way to go?
My understanding is: The Sunn amps used Dynaco transformers. In fact, as far as I know Dynaco built the amps for Sunn at first.. Tubedepot, I think that's the name, sells Dynaco kits.
Could be wrong but that is what I recall from my studies. I also simply built the Non UL PP circuit and very pleased with the outcome.
Regards,
Ccat.
My understanding is: The Sunn amps used Dynaco transformers. In fact, as far as I know Dynaco built the amps for Sunn at first.. Tubedepot, I think that's the name, sells Dynaco kits.
Could be wrong but that is what I recall from my studies. I also simply built the Non UL PP circuit and very pleased with the outcome.
Regards,
Ccat.
Thanks guys!
I will now scratch that Major transformer plan!
I will build the Model T, like it was on the old schematic.
Too many colnes out there that only has the name but not the guts.
I will gather some information about the Mark VI and Dynaco.
Here is the link for MercuryMagnetics transformer page
Mercury Magnetics - Sunn amp transformers
I will now scratch that Major transformer plan!
I will build the Model T, like it was on the old schematic.
Too many colnes out there that only has the name but not the guts.
I will gather some information about the Mark VI and Dynaco.
Here is the link for MercuryMagnetics transformer page
Mercury Magnetics - Sunn amp transformers
Sunn actually started out by making well designed and efficient speaker cabinets, not amps.
Since hardly any Sunn designer at the time knew how to design and amp the solution for making an amp product was simple: They bought Dynakit Mark III and Mark IV power amps and PAS-1 / PAM-1 preamps in bulk and mounted them to selfmade cabinets. Naturally, when all internal electronics were built from Dynaco's products the transformers were from Dynaco too. ;-)
Later on they modified these designs a little bit to suit instrument amplification better. Dynakits were eventually ditched when Sunn started making their own chassis from sheet metal. A bit later they went straight to ordering transformers from the same supplier that Dynaco used. So they no longer needed Dynakits to make a product.
Model T appeared almost ten years later than any of this. By the time Sundholmn brothers had already sold the company to Hartzell Corp.
Be aware that there are at least three different model T's: The very first one, revision A, is practically a Fender 5F6 preamp married to a 150W ultralinear power amp. Revision C, known as Model T Super, is almost identical looking unit, except for a variable mid-range switch (a feature adopted from Model A's). However, internally it's almost nothing like the original design and has "James"-style tone control instead of that Fender circuit and quite different "gain staging". Rev A is preferred by guitarists, Rev C by bassists. Guitarist didn't really love rev C. By the way, schematic in the very first post is for Model T Super, not for the Model T revision A. Fender's reissue is a totally different and very modern design and I don't even know why they named it Model T. It's not even vaguely similar to originals.
Schematic for revision A model T:
http://elektrotanya.com/PREVIEWS/63463243/23432455/sunn/sunn_model-t.pdf_1.png
I have no idea about what kind of an amp revision B was.
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Thanks teemuk!
That new Fender reissue is not worth the name.
But good points on the Super vs the first gen.
I actually posted the second Gen Super schematic in the first post.
Here is the First Gen. Obvious differences in the Preamp section.
Great input!
http://www.prowessamplifiers.com/schematics/post/sunn_model_t.pdf
That new Fender reissue is not worth the name.
But good points on the Super vs the first gen.
I actually posted the second Gen Super schematic in the first post.
Here is the First Gen. Obvious differences in the Preamp section.
Great input!
http://www.prowessamplifiers.com/schematics/post/sunn_model_t.pdf
Got some numbers from the forums.
So it looks like from Hammond, I could use
PT: http://www.hammondmfg.com/pdf/EDB290FEX.pdf
OT: http://www.hammondmfg.com/pdf/EDB1650TA.pdf
But the OT can only handle 120W from the spec and PT is a bit low on HV voltages?
Also the heater current looks low (5.5A).
6550 says it heats 1.6A. 4x1.6 is 6.4A + 3x 12AXT 900mA = 7.3A.
So its not the best, as its low on everyhting. But its cheap.
But I will probably skip this path.
So it looks like from Hammond, I could use
PT: http://www.hammondmfg.com/pdf/EDB290FEX.pdf
OT: http://www.hammondmfg.com/pdf/EDB1650TA.pdf
But the OT can only handle 120W from the spec and PT is a bit low on HV voltages?
Also the heater current looks low (5.5A).
6550 says it heats 1.6A. 4x1.6 is 6.4A + 3x 12AXT 900mA = 7.3A.
So its not the best, as its low on everyhting. But its cheap.
But I will probably skip this path.
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Hi Guys
The Hammond 1650TA OT is rated at full audio bandwidth as 120W. For a guitar or bass you can use it as a 200W part.
The matching PT is the 278CX (378CX for 240V).
This pair of transformers will produce 160Wrms with any set of large-bottle tubes wired as tetrode/pentode. For UL, you can use KT-88 or 6550 PROVIDED the screen-stops are at the recommended value of 1k-5W per tube. Screen-stops should always be correct values and should always be intact for all operating modes.
TUT3 shows this output stage as the Custom Special built by Traynor.
It is important to realise that the range of operation for most of the common tubes widely overlap as does the range of useful primary impedances, so the notion that "you should have Zaa for tube-A" is bunk.
MM is generally a waste of money.
Have fun
The Hammond 1650TA OT is rated at full audio bandwidth as 120W. For a guitar or bass you can use it as a 200W part.
The matching PT is the 278CX (378CX for 240V).
This pair of transformers will produce 160Wrms with any set of large-bottle tubes wired as tetrode/pentode. For UL, you can use KT-88 or 6550 PROVIDED the screen-stops are at the recommended value of 1k-5W per tube. Screen-stops should always be correct values and should always be intact for all operating modes.
TUT3 shows this output stage as the Custom Special built by Traynor.
It is important to realise that the range of operation for most of the common tubes widely overlap as does the range of useful primary impedances, so the notion that "you should have Zaa for tube-A" is bunk.
MM is generally a waste of money.
Have fun
Hi Guys
"The reason Marshall have the sound they have is due to the bias setting."
That statement is incorrect, but... it is entirely true if you change Marshall to Mesa. Bias an amp real cold and you have the glorious Mesa sound: lifeless, no sustain, but able to use the cheapest tubes.
Marshalls sound how they do because of poor wiring and grounding schemes - tonnes of intermodulation distortion to make even a clean tone kind of edgey. Dump the CF for a warmer tone and to to have tone controls that DO something.
Fender has the iconic clean sound for both guitar and bass. Their wiring methods were not great either, but they used better OTs than Marshall (who began using surplus OTs/PTs just to get going),m and the 6L6GCs have a more neutral sound. Fender generally did things quite well, since Leo had service experience and access to good quality parts.
The Major is not to be compared with other Marshalls as its circuit is quite different. The PA feedback loop wraps around the EQ and there is only one stage outside this loop. Where the CF in a standard preamp already impedes what the EQ might do, this enclosed EQ has even less effect - the hope was to have more effect. I built a "baby Major" in the '80s and heard it for myself. My curiosity about the circuit was satisfied although the result was opposite to what I expected.
When you build your amp, put the preamp on its own card so it can be easily changed.
Also be sure to include individual bias pots and meter jacks for the output tubes so you can use any tube type and mix them, too.
Have fun
"The reason Marshall have the sound they have is due to the bias setting."
That statement is incorrect, but... it is entirely true if you change Marshall to Mesa. Bias an amp real cold and you have the glorious Mesa sound: lifeless, no sustain, but able to use the cheapest tubes.
Marshalls sound how they do because of poor wiring and grounding schemes - tonnes of intermodulation distortion to make even a clean tone kind of edgey. Dump the CF for a warmer tone and to to have tone controls that DO something.
Fender has the iconic clean sound for both guitar and bass. Their wiring methods were not great either, but they used better OTs than Marshall (who began using surplus OTs/PTs just to get going),m and the 6L6GCs have a more neutral sound. Fender generally did things quite well, since Leo had service experience and access to good quality parts.
The Major is not to be compared with other Marshalls as its circuit is quite different. The PA feedback loop wraps around the EQ and there is only one stage outside this loop. Where the CF in a standard preamp already impedes what the EQ might do, this enclosed EQ has even less effect - the hope was to have more effect. I built a "baby Major" in the '80s and heard it for myself. My curiosity about the circuit was satisfied although the result was opposite to what I expected.
When you build your amp, put the preamp on its own card so it can be easily changed.
Also be sure to include individual bias pots and meter jacks for the output tubes so you can use any tube type and mix them, too.
Have fun
No Cathode Follower?
So are you saying- "remove the cathode follower and go from there"? Would the builder need to add another gain stage to drive the tone stack or is the existing gain stage sufficient to drive the tone stack after the CF is removed?
I ask as I just built an JTM-45 and it uses the CF so I wonder if removing that stage would enhance tone of the amp?
colorcat.
So are you saying- "remove the cathode follower and go from there"? Would the builder need to add another gain stage to drive the tone stack or is the existing gain stage sufficient to drive the tone stack after the CF is removed?
I ask as I just built an JTM-45 and it uses the CF so I wonder if removing that stage would enhance tone of the amp?
colorcat.
Hi Guys
Yes, just bypass the cathode follower. The preceding stage will drive the EQ. TUT6 explains in detail why the CF is there and why it is such a tone killer in the places it is used. The only good place to use one is to drive a line out, or to buffer a pentode plate for maximum gain from the pentode.
Have fun
Yes, just bypass the cathode follower. The preceding stage will drive the EQ. TUT6 explains in detail why the CF is there and why it is such a tone killer in the places it is used. The only good place to use one is to drive a line out, or to buffer a pentode plate for maximum gain from the pentode.
Have fun
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