I am going to build myself a single ended el 84 amp. The Hammond 125-series play from about 100 hz, and they(Hammond) do not recommend these for audio use.
Found these on E-bay and I wonder if they are ok?
Raphaelite 5K 8W AMP output transformer potting style 45 6V6 EL84 single-ended
Found these on E-bay and I wonder if they are ok?
Raphaelite 5K 8W AMP output transformer potting style 45 6V6 EL84 single-ended
Why not try this?
TTG-EL84SE - Tube output UL transformer [5kOhm] EL84 / 6V6 SE - Shop Toroidy.pl
Correct parameters, within EU.
TME sells it:
ttg el84se - Searched phrase | Electronic components. Distributor, online shop – Transfer Multisort Elektronik
TTG-EL84SE - Tube output UL transformer [5kOhm] EL84 / 6V6 SE - Shop Toroidy.pl
Correct parameters, within EU.
TME sells it:
ttg el84se - Searched phrase | Electronic components. Distributor, online shop – Transfer Multisort Elektronik
I'd stay away from series feed Chinese iron. A Sowter SA-02 or Monlith ETU-3/5K would be really solid choices. One-Electron UBT-2 would be a decent budget choice, but shipping costs may be prohibitive.
The toroid from Toroidy looks very promising:
Transformer: speaker; 30VA; Ø115x65mm; 0.01÷55kHz; 150mA
Regards, Gerrit
Transformer: speaker; 30VA; Ø115x65mm; 0.01÷55kHz; 150mA
Regards, Gerrit
No datasheet.
I have a pair.
Measurements (DER EE 5000):
Pri: 14.3H, 159.5R, 169.6pF, Rp:53k
Sec: 22.88mH, 0.28R
Lsp: 7.1mH
Curve (Rg:700R, Rt:8R):
Attachments
Oof, that's rough for a 5K transformer! If that was the 2.5K one, that would be reasonable.
It's odd because the datasheets that are available for the Summit parts show about 40H of primary inductance for the 5K models, which is reasonable.
It's odd because the datasheets that are available for the Summit parts show about 40H of primary inductance for the 5K models, which is reasonable.
Monolith's promise was 20H, and 7Hz..87kHz bandwidth (I bough this from secondhand).
I use it for E55L spud.
I use it for E55L spud.
I have seen the prices for a pair of Monolith, and fir a pair they cost about 600 UKP for me, and that before taxes/vat and postage. That is a little bit over what I want to use for a pair
With low output impedance tube (trioded E55L has 600R) up to 2-3W ETU-3 is not so bad, but yes, it costly.
Any who have experience with the Hammond 125-series? Hammond do not recommend this output transformers for audio? I have talked to people who has used them, and they tell me that it is a prefect match for el 84se. And that they are great down to about 30 hz?
I bought a pair of Hammond 125DSE and the bass i good! Have not checked/measured, but the low frequency are pretty good. I triode wired my el 84 SE and I probably have 1,5w-ish?, but 1,5 watts drive my Klipsch RF 15 pretty good. Fills my livingroom with music. Why are Hammond telling us that this output transformer do not go under 100Hz? Perhaps there are something wrong with my ears?
The following is just a theoretical exercise; I have not yet used or measured any of the 125xSE transformers. Caveat lector!
The 125ESE is the only one with a quoted inductance measurement (about 10 henries). But they are all specified 100Hz or better bass for all impedances 2500, 5000, or 10000 ohms so presumably they all have the same primary inductance. If it is OK for 100Hz at 10Kohms, it must be OK for 5Kohms to 50Hz, or 2.5Kohms to 25Hz.
The small-signal bass response for SETs is 1dB down when the inductive reactance equals twice the tube plate resistance, which is typically 1/2 to 1/4 of the nominal primary impedance; 10 henries is 1500 ohms at 25Hz, so that works out reasonably well.
Pentode-mode amps won't have as much bass extension unless they have feedback, but they usually do have feedback to get decent speaker damping.
In the treble, they are all specified -1dB at 15kHz or better. That's harder to parse, since there are both leakage inductance and winding self-capacitance, and they depend on the size of the transformer. But 1dB down at 15kHz is not enough to be a big problem for anyone outside the really high end.
The 125ESE is the only one with a quoted inductance measurement (about 10 henries). But they are all specified 100Hz or better bass for all impedances 2500, 5000, or 10000 ohms so presumably they all have the same primary inductance. If it is OK for 100Hz at 10Kohms, it must be OK for 5Kohms to 50Hz, or 2.5Kohms to 25Hz.
The small-signal bass response for SETs is 1dB down when the inductive reactance equals twice the tube plate resistance, which is typically 1/2 to 1/4 of the nominal primary impedance; 10 henries is 1500 ohms at 25Hz, so that works out reasonably well.
Pentode-mode amps won't have as much bass extension unless they have feedback, but they usually do have feedback to get decent speaker damping.
In the treble, they are all specified -1dB at 15kHz or better. That's harder to parse, since there are both leakage inductance and winding self-capacitance, and they depend on the size of the transformer. But 1dB down at 15kHz is not enough to be a big problem for anyone outside the really high end.
If you drive a small SE transformer at 20Hz, with 100mW, it may do OK for frequency response.
Now, drive the same transformer with 1 Watt at 20Hz, the frequency response may still seem OK, but in reality, a large portion for that power out will be harmonic distortion (because of the saturation of the laminations).
When it saturates, most of the inductive reactance disappears, Right?
Putting global feedback around that transformer will only make the saturation at low frequencies worse.
Still, if you have such a transformer, use it. See what it does. Only then will you know its limits in the amplifier you design for it.
Now, drive the same transformer with 1 Watt at 20Hz, the frequency response may still seem OK, but in reality, a large portion for that power out will be harmonic distortion (because of the saturation of the laminations).
When it saturates, most of the inductive reactance disappears, Right?
Putting global feedback around that transformer will only make the saturation at low frequencies worse.
Still, if you have such a transformer, use it. See what it does. Only then will you know its limits in the amplifier you design for it.
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I see the Toroidy transformer linked above is rated for 30W. Is there a downside to using a larger transformer like that in 6W application?.
Reason I ask is that I see Japanese H507S and XE-20 OPT recommended for use with 5k Rp tube at Ip 35mA (type 45 for example<3W), and the transformers are rated 7W and 20W respectively, with max air gap 160mA DC.
.. and others will use 3W transformer gapped for 40mA, and the same primary Lpri as the other two examples.
Just wondering if its convenience with the 'universal' builds comes with some penalty?.
Reason I ask is that I see Japanese H507S and XE-20 OPT recommended for use with 5k Rp tube at Ip 35mA (type 45 for example<3W), and the transformers are rated 7W and 20W respectively, with max air gap 160mA DC.
.. and others will use 3W transformer gapped for 40mA, and the same primary Lpri as the other two examples.
Just wondering if its convenience with the 'universal' builds comes with some penalty?.
The power rating doesn't mean a lot unless they also give a frequency to go with it.
The XE-20S is a pretty nice 2.5K transformer, but it's not a particularly nice 5K transformer. At 5K there isn't enough inductance to support good low frequency response and there is a lot of unused copper on the secondary that screws up the high frequency response. Being a Japanese transformer, the trade is happily made to get HF extension well beyond what is necessary, so at least the poor HF response is relative to what's available in the 2.5K configuration. This is all pretty clearly laid out in the datasheet.
The H507S gives 7W/50Hz rating, so I wouldn't be super excited to use it in a 6W amp. The H507S is worse than the XE-20S as a 5K transformer. Again, the datasheet is very telling about how this transformer performs.
For a 45, the downside to the big iron with a big air gap is that you're throwing away the possibility of having more primary inductance to get that 160mA DC current rating. To get the inductance back, you need a lot of copper, and a lot of copper leads to undesirable side effects. The physically larger transformer will also require more labor to properly design/manufacture compared to something a bit smaller (to address those undesirable side effects).
The XE-20S is a pretty nice 2.5K transformer, but it's not a particularly nice 5K transformer. At 5K there isn't enough inductance to support good low frequency response and there is a lot of unused copper on the secondary that screws up the high frequency response. Being a Japanese transformer, the trade is happily made to get HF extension well beyond what is necessary, so at least the poor HF response is relative to what's available in the 2.5K configuration. This is all pretty clearly laid out in the datasheet.
The H507S gives 7W/50Hz rating, so I wouldn't be super excited to use it in a 6W amp. The H507S is worse than the XE-20S as a 5K transformer. Again, the datasheet is very telling about how this transformer performs.
For a 45, the downside to the big iron with a big air gap is that you're throwing away the possibility of having more primary inductance to get that 160mA DC current rating. To get the inductance back, you need a lot of copper, and a lot of copper leads to undesirable side effects. The physically larger transformer will also require more labor to properly design/manufacture compared to something a bit smaller (to address those undesirable side effects).