SSE with Zu Omens

[kaos2088]

I'm interested in building a Tubelab SSE to power my Zu Omens. Bought them with the goal of building a tube amp for it and I keep hearing great things about the SSE.

I really want to gear the amp to the Omens and about the only decisions I've made thus far is that I need to include a choke and auxiliary cap and am planning on running in triode mode. I am still unsure what I should use for tubes. I was just going to hunt around on eBay for something that looked interesting.

As I start to put together a parts list my first question is if the Omen's 12Ω impedance is going to cause any issues. I had been looking at the Transcendar TT-312-OT OPT, but it is meant for an 8Ω impedance. Should I be looking specifically for a 12Ω OPT?

This is will be my first build so any suggestions for parts/ways to gear the SSE to my Omens would be appreciated.

[cotdt]

Why not the TSE? It's only slightly more expensive, and you can use tubes like 45 or 300B.

12 ohm impedance is the perfect load for most tube amps. Most 8 ohm speakers are actually 5-6 ohms and sounds better on the 4 ohm transformer tap. 12 ohm should be awesome on the 8 ohm tap.

[kaos2088]

Really only went with SSE cause it was a simpler design and easier to build. As I research this more, those don't seem like good reasons, the TSE doesn't seem too much harder to build. The Omens are 97dB so they should be able to handle those tubes fine.... Thinking I should build the TSE now..

[spendorite]

Originally Posted by kaos2088

I'm interested in building a Tubelab SSE to power my Zu Omens. Bought them with the goal of building a tube amp for it and I keep hearing great things about the SSE.


As I start to put together a parts list my first question is if the Omen's 12Ω impedance is going to cause any issues. I had been looking at the Transcendar TT-312-OT OPT, but it is meant for an 8Ω impedance. Should I be looking specifically for a 12Ω OPT?

This is will be my first build so any suggestions for parts/ways to gear the SSE to my Omens would be appreciated.

It depends on how efficient your Zu Omens are and how loud you like to
listen to music, also room size will be a factor.
If the Omens efficiency is over 92db you'll be okay especially in ultra
linear mode with KT88 tubes.
If the efficiency is in the upper eighties (88-90 db) you'll still be okay
in a small to midsize room when using KT88 in ultra linear mode.

Below 88db efficiency the rule of diminishing returns kicks in especially
when using the amp in triode mode.

[spendorite]

Originally Posted by kaos2088

Really only went with SSE cause it was a simpler design and easier to build. As I research this more, those don't seem like good reasons, the TSE doesn't seem too much harder to build. The Omens are 97dB so they should be able to handle those tubes fine.... Thinking I should build the TSE now..

Well, with your speakers rated at 97db you will have no problems at all
regardless of which amp you choose.

[rknize]

The SSE is more flexible, as it uses "standard" tubes that are still in production. The TSE is a superior design, but is more complex and uses more expensive and hard-to-find NOS tubes. It also puts out less power than an SSE potentially can, especially if you go with 45s.

I'd use an 8 ohm secondary with those speakers, though you can expect less power from the amplifier with that load unless you compensate with the primary.

[boywonder]

Kaos2088: The output transformer reflects the speaker load back to the output tubes.

For example, with a 5K/8 ohm transformer with 8 ohm speakers the tubes see 5Kohm impedance. If you connect a 4 ohm speaker to these 8 ohm taps, the tubes will see 2.5Kohm load with this 5Kohm primary. So if you connected 16 ohm speakers to these taps the tubes would see 10K load and so on.

In your case, depending on what tubes you want to run, you can select an appropriate output transformer primary impedance to be happy with a 12 ohm load, like 2.5K-3.5K/8R or so depending on what output tubes you want to use. Some output transformers have multiple primary taps for added flexibility like the James 6123 for example.

Look at the "Tubes and transformers" page on the Tubelab website for either amp to get an idea of power out, distortion, etc for different tubes, primary impedances and B+ voltages.

As Russ K already mentioned, a higher impedance load in general has the effect of reducing output power and distortion slightly. And a lower impedance load will provide more power out and more distortion. This is shown in Tubelab's tables.

If your speakers are 97db sensitivity then you need a mouse-fart worth of power, and a Tubelab SE with 45's would probably rock the house, or any Tubelab SSE config.

[kaos2088]

Thanks for the info everyone. I went ahead and ordered a TSE board and am going to go with the 300B design. I've been debating between the 45 and 300B, but in the end I want to be certain I will have enough power... even if I'm not using such an efficient speaker.

For the OPT, I am now looking at the Electra Print "Albert Pagan" design as recommended in the Tubes and Transformers page. I sent an email to electra print to get the specs and price as I really don't know anything about it at the moment.

For the power transformer, I'm not finding many recommendations except for the Hammond 272JX. This seems to be below the recommended 640~650V, but according to what I'm reading, it will work. Is there another power transformer I should consider for the project?

The other part that is confusing me at the moment is the High Voltage Mosfet Toshiba 2SK3563. Its out of stock and I found this statement "The 2SK2700 mosfet has gone extinct due to ROHS laws. Toshiba decided to discontinue the part rather than make an unleaded version. I have found two suitable substitutes, the Fairchild FQP1N50 and the Supertex DN2540N5." Just want to confirm that the 2SK3563 is the same thing as the 2SK2700 and can be substituted by the Sopertex as that is the only one I can find.

[rknize]

Apparently, he has forgotten what the "Albert Pagan" design is. Hopefully he knows the Tubelab SE well enough by know to be able to make what you want. If not you'll need to feed him the exact specs that you need. I think TM3KB is a generic design of his that you can use.

For the power transformer, you can consider the XPWR131 which was designed for use with the TSE:



There are several threads on here about the FETs for the TSE. I'm not up to speed on this, as it is a constantly-moving target. I would search this forum for recommendations. For example:

Mosfets for Tubelab SE?

[amandarae]

Originally Posted by kaos2088

Thanks for the info everyone. I went ahead and ordered a TSE board and am going to go with the 300B design. I've been debating between the 45 and 300B, but in the end I want to be certain I will have enough power... even if I'm not using such an efficient speaker.

For the OPT, I am now looking at the Electra Print "Albert Pagan" design as recommended in the Tubes and Transformers page. I sent an email to electra print to get the specs and price as I really don't know anything about it at the moment.

For the power transformer, I'm not finding many recommendations except for the Hammond 272JX. This seems to be below the recommended 640~650V, but according to what I'm reading, it will work. Is there another power transformer I should consider for the project?

I* use Angela Instruments Power trafo in my 300B TSE. I know of two other people who built their TSE with the exact power transformer.

http://angela.com/angelauniversalpowertransformer.aspx

With one 5V of the taps not being employed(5V@ 1.5A), it barely get warm to the touch even after hours of being use in my amp.

*Not affiliated to the vendor whatsoever!


Abe