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OPT for EL34. Will it work on future SE?

anatech

Administrator
Paid Member
2004-06-06 8:31 pm
Georgetown, On
Hi Joca,
Not really. SE output transformers have an air gap to prevent core saturation. P - P transformers are designed for a balanced current in each half that cancels to leave a very low amount of net current in the primary. The core therefore doesn't saturate. These transformers do not have as wide an air gap and may easily saturate with unbalanced currents.

Will it make noise? Yes. Will it work properly? Not a chance.

-Chris
 
i can use the same opt's for the SE. Is this possible?

Yes, it will work fine. I have used the same pair of Edcors in an SSE, a TSE, and several other SE amps, before they wound up in a 307A based TSE.

Choose an impedance and power rating that works with both tubes that you intend to use. If you are going to use EL34's in the SSE, and 300B's in the TSE, a 3.6K or 4K ohm OPT will work, but I still prefer 5K. If you intend to use 45's in the TSE you must use a 5K OPT. 45's really don't like much below 5K, while 2A3's and 300B's will work with anything over 3K.
 
Hi tubelab.com,
What about core saturation?

-Chris

OP needs to get an OPT that can handle sufficient current for both amps.

The reasonably priced 5K 10 watt Transcendar works well for both TSE and SSE - I know this from personal experience. The 3K 10 watt works well on the SSE, but probably would not be a good choice for a combo amp if one wanted to use 45's, otherwise, it would also work fine in both amps.

Win W5JAG
 

anatech

Administrator
Paid Member
2004-06-06 8:31 pm
Georgetown, On
Hi spendorite,
The most common used transformers big enough for EL34's will be push-pull designs. Without a larger air gap, the unbalanced current flow in the primaries will have him working nearer to saturation on peaks. SE transformers do have larger air gaps to allow them to work in an SE design.

Go look in catalogs. Most SE designs will use various tubes, but the 6L6 type is more common than the EL34 types. An EL34 is a true pentode (should be) and wouldn't tend to be used as a triode with the lower plate dissipation and higher heater current. The 6L6GC family has a higher wattage plate (30 W vs 25 W) and has much lower heater current. It just doesn't make sense to use an EL34 for SE compared to some of the TV sweep tubes or the 6L6GC family.

So, going by what you are most likely going to see, the transformer will be p-p.

Now if Joca specifically bought transformers for SE design with EL34 tubes, that is an entirely different story. Then you only have the primary impedance to worry about.

-Chris
 

Joca

Member
2014-10-04 9:21 pm
Aveiro
Hi spendorite,
The most common used transformers big enough for EL34's will be push-pull designs. Without a larger air gap, the unbalanced current flow in the primaries will have him working nearer to saturation on peaks. SE transformers do have larger air gaps to allow them to work in an SE design.

Go look in catalogs. Most SE designs will use various tubes, but the 6L6 type is more common than the EL34 types. An EL34 is a true pentode (should be) and wouldn't tend to be used as a triode with the lower plate dissipation and higher heater current. The 6L6GC family has a higher wattage plate (30 W vs 25 W) and has much lower heater current. It just doesn't make sense to use an EL34 for SE compared to some of the TV sweep tubes or the 6L6GC family.

So, going by what you are most likely going to see, the transformer will be p-p.

Now if Joca specifically bought transformers for SE design with EL34 tubes, that is an entirely different story. Then you only have the primary impedance to worry about.

-Chris

I intend to build the Tubelab SSE with the EL34's because they are mentioned in the building process/options. I didn't know this, aparently, may be a "bad" choice compared to other tubes arround to be used in this SSE design. Please, advise. I am still in the preliminary phase of the building process. Thank you.
 
anatech

This forum is dedicated to Tubelab amplifiers, of which there are currently three, the SSE, the TSE and the SPP. The SPP is the only push pull amp and it is specifically designed for EL84's, 6BQ5's or 6CW5's (9 pin sockets).

The only amp that works with the EL34 is the SSE, which can also use the 6L6GC, KT88, 6550, 6V6 and other pin compatible tubes. The EL34 does work quite well as a triode in the SSE, although with slightly less power than a 6L6GC or KT88. Being a true pentode, the EL34 does have a different sound than the 6L6GC which many people, including myself prefer.

The TSE (refered to by the OP as the SE) uses DHT's like the 45, 2A3 or the 300B. Both amps are in the same power range, and both can be set up with small power transformers and operated in the 30 mA range (45 or triode 6V6) or larger power transformers and operated around 70 mA (300B or EL34, 6L6GC or KT88) so it is perfectly acceptable to use the same OPT in each design, given a similar sized output tube choice.
 
I intend to build the Tubelab SSE with the EL34's because they are mentioned in the building process/options. I didn't know this, aparently, may be a "bad" choice compared to other tubes arround to be used in this SSE design. Please, advise. I am still in the preliminary phase of the building process. Thank you.

As Tubelab states above, post #10, and as you you will find in the documentation on
the SSE, EL34 tubes will work very well in this amplifier.
Just make sure you select suitable power xfrmr and opt's.
Many builders including myself have used EL34 in the SSE with fine results.
 
I am looking at the edcor CXSE 25-8-5K, the transcendar 15w 8ohm 5K. These are at the same price range. However, i'm not sure about the power transformer to use now and in the future TSE. Maybe the edcor xpwr059? What do you think? One last word from you, thank you all

I have used the Edcor CXSE 25-8-5K opt's with the Edcor XPWR035 power xfrmr in my SSE for
KT88/6550, 6L6, EL34 with excellent results.

The Transcendars mentioned by W5JAG in post #7 may also be considered.

The XPWR035 5V tap is rated for 2 amps so tube rectifiers like 5U4 which are 3 amps cannot be used.

I haven't built a TSE so cannot offer any suggestions regarding this.