Hi,
Can anyone please advise on which Lundhal SE OPT to use for an EL84 project, possibly the RH84 amplifier - revision 2 should it be the 50ma 35H or 100ma 17H
The specs are -
Tube amplifier output transformer LL1663 5k : 8 ohms
The LL1663 is a four-sectioned dual coil C-core tube amplifier output transformer for 5 k: 8 ohms impedance ratio available in PP and SE versions.
The coil is wound using our high internal isolation technique with isolation foil between each copper layer. The core is an audio C-core of our own production.
Turns ratio 12+12 : 1 or (4+8)+(4+8) : 1
Weight: 1.35 kg
Static resistance of each primary: 102 Ohm
Static resistance of secondary: 0.4 Ohm
Isolation between windings / between windings and core: 4 kV / 2 kV
Max DC current through any primary winding: 160mA
(approx.)
LL1663/PP. Max primary signal 450V R.M.S. @ 30 Hz Max primary signal 40W (8 Ohm spkr)
LL1663/50mA Primary inductance 35H Max primary signal200V R.M.S. @ 30 Hz. Max primary signal. 8W (8 Ohm spkr)
LL1663/100mA Primary inductance. 17H. Max primary signal 200V R.M.S. @ 30 Hz. Max primary signal. 8W (8 Ohm spkr)
They are available here
Lundahl Tube amplifier output transformer, LL1663-100mA - Fidelity Components Shop
You can download the sheet here https://jacmusic.com/lundahl/datasheets/1663.pdf
I am in the UK so need 240v or 230v mains transformer
There is also a mains transformer here LL2758
LL2758 ⋆ Lundahl Transformers
Thanks for your help
Can anyone please advise on which Lundhal SE OPT to use for an EL84 project, possibly the RH84 amplifier - revision 2 should it be the 50ma 35H or 100ma 17H
The specs are -
Tube amplifier output transformer LL1663 5k : 8 ohms
The LL1663 is a four-sectioned dual coil C-core tube amplifier output transformer for 5 k: 8 ohms impedance ratio available in PP and SE versions.
The coil is wound using our high internal isolation technique with isolation foil between each copper layer. The core is an audio C-core of our own production.
Turns ratio 12+12 : 1 or (4+8)+(4+8) : 1
Weight: 1.35 kg
Static resistance of each primary: 102 Ohm
Static resistance of secondary: 0.4 Ohm
Isolation between windings / between windings and core: 4 kV / 2 kV
Max DC current through any primary winding: 160mA
(approx.)
LL1663/PP. Max primary signal 450V R.M.S. @ 30 Hz Max primary signal 40W (8 Ohm spkr)
LL1663/50mA Primary inductance 35H Max primary signal200V R.M.S. @ 30 Hz. Max primary signal. 8W (8 Ohm spkr)
LL1663/100mA Primary inductance. 17H. Max primary signal 200V R.M.S. @ 30 Hz. Max primary signal. 8W (8 Ohm spkr)
They are available here
Lundahl Tube amplifier output transformer, LL1663-100mA - Fidelity Components Shop
You can download the sheet here https://jacmusic.com/lundahl/datasheets/1663.pdf
I am in the UK so need 240v or 230v mains transformer
There is also a mains transformer here LL2758
LL2758 ⋆ Lundahl Transformers
Thanks for your help
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Don't forget the LL1682. I have a pair and I like them quite a lot. For example they suit a 300b better than the LL1664. I haven't tried the LL1663.
Have no idea what's ER84 Rev.2, but if it's a single output tube SE amp, it'll run at 30-40mA, so 50mA version is plenty enough (and more inductance never hurts).
Sorry, I have just corrected the post I mistyped and it should be RH84 amplifier - revision 2
RH Amplifiers: RH84 amplifier - revision 2
Thanks
RH Amplifiers: RH84 amplifier - revision 2
Thanks
That depends on your end goal of how you plan to use the transformer. 100mA SE has wider air gap. It handle more DC current at the expense of some output bandwidth. If you plan to uses it with an EL84, the 50mA version will be enough and should yield better bandwidth performance. However, let say you want to re-use the transformer for a later on project with an EL34 or KT88 then you might consider the 100mA version. Or if you plan to reuse it for an Ultra Linear output configuration, then something like LL1682 might work.
The 1663 is only an 8 watt single ended transformer, and it's cheap enough that he can buy something else if need be. If anything, I would probably ask lundahl to make the gap smaller and try to squeeze a little more inductance out of it.
At 40Hz:
100mA version
17 Henrys is only 4,272 Ohms inductive reactance.
The primary 5k is in parallel with 4,272 Ohms.
OK bandwidth for a very quiet lead guitar amp and only 1 EL84,
and maybe even OK for a (very quiet) bass amp . . . only if you Parallel 2 EL84 tubes
At 25 Hz:
50mA version
35 Henrys is 5,498 Ohms inductive reactance.
The primary 5k is in parallel with 5,498 Ohms.
OK for a Hi Fi amp.
(25 Hz is probably better than your Loudspeakers).
A single EL84 driving a 5k primary, for a Hi Fi . . .
I "vote" for the 50mA version transformer (smaller Air Gap, than the 100mA version).
RH84 rev 2 amp is 46.3 mA, Perfect.
Just remember, the transformer will saturate at 25Hz and full output power. It is low cost and too small.
The 50mA version might be OK for a low cost amp with a 45 output tube (I got some used 45 tubes that are OK;
New Old Stock are too Expen$ive for a low cost amp).
100mA version
17 Henrys is only 4,272 Ohms inductive reactance.
The primary 5k is in parallel with 4,272 Ohms.
OK bandwidth for a very quiet lead guitar amp and only 1 EL84,
and maybe even OK for a (very quiet) bass amp . . . only if you Parallel 2 EL84 tubes
At 25 Hz:
50mA version
35 Henrys is 5,498 Ohms inductive reactance.
The primary 5k is in parallel with 5,498 Ohms.
OK for a Hi Fi amp.
(25 Hz is probably better than your Loudspeakers).
A single EL84 driving a 5k primary, for a Hi Fi . . .
I "vote" for the 50mA version transformer (smaller Air Gap, than the 100mA version).
RH84 rev 2 amp is 46.3 mA, Perfect.
Just remember, the transformer will saturate at 25Hz and full output power. It is low cost and too small.
The 50mA version might be OK for a low cost amp with a 45 output tube (I got some used 45 tubes that are OK;
New Old Stock are too Expen$ive for a low cost amp).
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FWIW I considered the LL1663 and LL1682 for the RH84 r2 and ended up with the LL1663 (50mA versions)
I still haven't built the amp, should be a few weeks from now.
They can both work great with the RH84, I think you should choose based on intended speakers.
I will be using it with some Fostex fullrangers which are nominal 8 ohms so went with the 1663.
For power transformer, there are tons of options from Edcor or Hammond.
It depends on whether you will go with tube or SS rectification, if tube there is also a difference between 5AR4 and 5U4G due to different voltage drop. If SS, you can probably use a 250V (or 500VCT) and you don't need the 5V tap.
AC heaters or DC heaters (plan for 2X current rating if going DC)
I still haven't built the amp, should be a few weeks from now.
They can both work great with the RH84, I think you should choose based on intended speakers.
I will be using it with some Fostex fullrangers which are nominal 8 ohms so went with the 1663.
For power transformer, there are tons of options from Edcor or Hammond.
It depends on whether you will go with tube or SS rectification, if tube there is also a difference between 5AR4 and 5U4G due to different voltage drop. If SS, you can probably use a 250V (or 500VCT) and you don't need the 5V tap.
AC heaters or DC heaters (plan for 2X current rating if going DC)
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I haven't tried the LL1663. I like the LL1682/50 a lot. I guess you thought the LL1663 would be a good match, but it could have gone either way. Let us know the results. I haven't tried an EL84 with the LL1682 yet, but I have used a 300b which sounded great. I intend to try some other tubes as well, like an EL33. The EL33 is a very nice sounding tube and I have several. A bit off the beaten track but not rare.
I also got LL 1663 to upgrade my EL84SE amplifier but I have to wait a bit before I can do that. A new chassis must be manufactured before it is time to move the components. I have heard LL 1663 together with EL34 (I think long time ago) and I liked what I heard then there was no return, the OPTs I use today are Edcor 5K 8 and they work great but lack in the bottom and top which LL does not. It will be exciting when it is ready, good luck and a good continuation of the new year.