Why are there various output power ratings depending on the connection combination of the primary load?
Say, you have a transformer with:
10K / 40W
6K / 100W
3K / 160W
These are just sample numbers, but I am just curious about their ratings. How are these outputs? Comparable to Sowter, etc.?
Thanks!
Blair
Say, you have a transformer with:
10K / 40W
6K / 100W
3K / 160W
These are just sample numbers, but I am just curious about their ratings. How are these outputs? Comparable to Sowter, etc.?
Thanks!
Blair
The transformer hits its Bmax with some voltage of some frequency, say 100 Vrms at 30 HZ. Depending on the reflected load at the primary, this means 4 W/2,5 KOhm (100*100/2500), or 2 W/5KOhm, or 8 W/1,25KOhm.
The reflected load depends on the configuration of the secondary, which in Lundahl's case consists of multiple windings. You can arrange the secondary windings so that it reflects e.g. either 2,5 KOhm with a 8 Ohm load, or 5KOhm.
The same holds true for the case of intended mismatch at the secondary: If you load the 8 Ohm winding of a 5K/8 Ohm transformer with 4 Ohm, you get 2,5KOhm reflected impedance at the primary.
The reflected load depends on the configuration of the secondary, which in Lundahl's case consists of multiple windings. You can arrange the secondary windings so that it reflects e.g. either 2,5 KOhm with a 8 Ohm load, or 5KOhm.
The same holds true for the case of intended mismatch at the secondary: If you load the 8 Ohm winding of a 5K/8 Ohm transformer with 4 Ohm, you get 2,5KOhm reflected impedance at the primary.
Gotcha! Thanks!
I just bought a pair of LL1679s on eBay. Like I need another pair of transformers
http://www.lundahl.se/pdf/1679.pdf
So, this should be good for a quad of KT88s into this transformer wired for 2.6K?
Thanks!
Blair
I just bought a pair of LL1679s on eBay. Like I need another pair of transformers
http://www.lundahl.se/pdf/1679.pdf
So, this should be good for a quad of KT88s into this transformer wired for 2.6K?
Thanks!
Blair
What I would like to know, is how Lundahl can make a 700W OPT at 4.5kg, compared to a Hammond 280W at 10+ kg. Both claim to go down to 30Hz. Did someone compare these two perhaps? I'm very interested in the Lundahl, since it weighs as much as the Hammind 1650T (120W), but with much more flexibility.
You need to compare core cross-section, not overall size.
BTW, I don't think its possible to build 700W audio transformer weighting 4.5 kg with lowest frequency at full power 30 Hz. I assume this is typing error. Either this is 70W transformer either it weights 14.5 kg.
PS. I opened one of the Lundahl data sheets. Looks like you mixed "V" and "W" - 700V (max primary RMS voltage) with output power (in Watts).
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With all do respect, but did you actually read my post and/or the LL1693 datasheet
I'm talking weight here, I don't really care about the size. Size is not the limiting factor for me.
Secondly, no it's not a typing error. Both the site and datasheet clearly state 700W with a primary impedance of 600 ohm (in PP stages). The weight is mentioned multiple times at 4.5 kg.
And third, the 1693's max RMS signal voltage is 530V in PP stages.
So no, no errors and no mixing up values. That's the reason I'm so curious about this OPT. Any real world experiences anyone??
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Weight per volume is the almost the same for all iron based soft magnetic alloys. With C cores, you can get higher flux, and thus smaller core, but with EI core you can assemble thicker stack with larger cross-section area, and have less copper.
With all do respect, but did you actually read my post and/or the LL1693 datasheet
I'm talking weight here, I don't really care about the size. Size is not the limiting factor for me.
This is your original post, it doesn't mention any particular model, and the other person posted feedback on this thread mentioned LL1679.
I did quick simulation with the M4 GOSS core I used for 60W@20Hz / 3.9K output transformer
20Hz / 3.9K, min primary inductance 53H / 62H, power = 60W @ Bmax = 14500G, weight 3.88 kg
20Hz / 600 Ohm, min primary inductance 6.55H / 9.55H, power = 390W @ Bmax = 14500G
I didn't checked other parameters (which are just too many for quick check), but assume if you wire several sections of primary in parallel (for 600 Ohm) instead of serial (for several K), and divide manufacturer's rating by 2 - 3 for 20Hz and lower, meaningful Bmax, you can get practical limit from Lundahl's data sheet.
Also, you can ask Lundahl about your concerns, from the past communication with this company I can say they are helpful and professional.
Hope this helps.
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Gotcha! Thanks!
I just bought a pair of LL1679s on eBay. Like I need another pair of transformers
http://www.lundahl.se/pdf/1679.pdf
So, this should be good for a quad of KT88s into this transformer wired for 2.6K?
Thanks!
Blair
What do you mean with quad? 4 tubes in parallel? impossible.
1) you need about 700 Ohm primary impedance.
2) The standing DC current will be 350mA. The 1679/70mA saturates with 140. Without any AC signal! -> no bass under 200-300 HZ.
3) even if you adjust the gap to accomodate for DC, i doubt strongly that the primary's wire cross sectional area can stand it.
Anyone heard the difference between a silicon steel core and amorphous core output transformer? I tried both single ended and push pull OPT's from Lundahl and I would say amorphous core OPT sounds a lot better that worth for the higher price that I paid. The performance of the amorphous Push Pull is even more outstanding.
Hearing is believing.
Johnny
Hearing is believing.
Johnny
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