I recently saw a design that uses battery grid bias with an input transformer. I've used battery grid bias before but with an input cap so I'm interested in trying it with a transformer, which eliminates the need for the cap.
The input transformer used was a Lundahl LL1676 2:1. I looked it up and it's pretty expensive - a pair would be $260 plus shipping. I know Lundahl is pretty high end and I'm sure they are worth the price but I'd like to find something cheaper to experiment with. Does anyone know of a cheaper substitute? Something that would work in the circuit that's still fairly decent quality.
I know nothing about input transformers or what specs to look for. I'm wondering if Edcor or Hammond or ??? makes something similar to the Lundahl.
The input transformer used was a Lundahl LL1676 2:1. I looked it up and it's pretty expensive - a pair would be $260 plus shipping. I know Lundahl is pretty high end and I'm sure they are worth the price but I'd like to find something cheaper to experiment with. Does anyone know of a cheaper substitute? Something that would work in the circuit that's still fairly decent quality.
I know nothing about input transformers or what specs to look for. I'm wondering if Edcor or Hammond or ??? makes something similar to the Lundahl.
Edcor does indeed have line level transformers, look at this one for example:
EDCOR - XS1100
and a whole more on "level matchers"
EDCOR - Open Frame Matching Transformers
also mouser has a lot of transformers in their catalogues.
The limitation of a line level transformers is the amount of signal they can pass at low frequency, the LL1676 specifies 22VRMS at 30Hz at 1% (and 0,2% at 50Hz, so you see, lower frequencies have higher distortion). The Edcor XS 1000 says 7.5VRMS, but does not specify a frequency...
There is other considerations as well, such as the impedance of the driving stage as well as the load on the secondary...
can you post the design you saw?
EDCOR - XS1100
and a whole more on "level matchers"
EDCOR - Open Frame Matching Transformers
also mouser has a lot of transformers in their catalogues.
The limitation of a line level transformers is the amount of signal they can pass at low frequency, the LL1676 specifies 22VRMS at 30Hz at 1% (and 0,2% at 50Hz, so you see, lower frequencies have higher distortion). The Edcor XS 1000 says 7.5VRMS, but does not specify a frequency...
There is other considerations as well, such as the impedance of the driving stage as well as the load on the secondary...
can you post the design you saw?
This was used at the input to a preamp. In my case the source would be a CD player or similar line level which, I assume, would be a nominal 2v signal.
Quoting the post from another forum which describes the circuit:
"The battery feeds through an input transformer (LL1676), so no need for a coupling cap. See schematic. The battery is bypassed with a 10nF Multicap - the other cap and resistor shown are an RC network across the transformer secondary to snub any ringing. Made a big difference in clarity versus cap-coupled, which I tried first."
Here's the schematic:
Attachments
With 2Vrms you have a lot of choice 
Edcor used to have 1:1 line level trafos for about 12 -13 USD. Pick a 10k:10k and you are good to go! Added bonus you can also use balanced sources, given that they also put out about the same level of 2Vrms.
It is worth a try, also for galvanic isolation. A cap remains technically superior (less distortion, higher bandwith, generally cheaper).
Edcor used to have 1:1 line level trafos for about 12 -13 USD. Pick a 10k:10k and you are good to go! Added bonus you can also use balanced sources, given that they also put out about the same level of 2Vrms.
It is worth a try, also for galvanic isolation. A cap remains technically superior (less distortion, higher bandwith, generally cheaper).
+1 on Jensen. I've used the JT-11p a few times and they don't sound like much of anything. A slightly lower cost option that does have a bit more color is Cinemag. I've used their output transformers (and MIC input, but never line input, sorry to say) for a summing amp that I wanted to have some color and I was able to get two quite hefty OTs for about 1/2 the Jensen price. Jensen has repaired transformers for me from my parts bin too... I found some old rusty units and they re-encapsulated them for me. Great company.
Edcor is a real budget option. They make decent stuff and they are honest about their specs but it's just too much of a compromise to me for the components that will probably outlive everything else. People do make great gear with Edcor parts. Keep in mind Edcor are often build-to-order with 6-8 week lead times.
Edcor is a real budget option. They make decent stuff and they are honest about their specs but it's just too much of a compromise to me for the components that will probably outlive everything else. People do make great gear with Edcor parts. Keep in mind Edcor are often build-to-order with 6-8 week lead times.
I'm not sure why they used a 2:1 stepdown or if that would be necessary or desirable in my case.
With 2Vrms you have a lot of choice
Edcor used to have 1:1 line level trafos for about 12 -13 USD. Pick a 10k:10k and you are good to go! Added bonus you can also use balanced sources, given that they also put out about the same level of 2Vrms.
Well, I'm assuming it would be 2v since that's what seems to be the "standard", although I've seen some posts claiming 1v output so I guess I'd want it to work with anything within that range.
As I said, I know nothing about input transformers or interstages, I'm only familiar with PTs and OTs. How are suitable impedances determined? Why would a 10k:10k be more appropriate than, say a 600 ohm:600 ohm or some other impedance choice.
In the post I quoted the designer claimed an improvement over a cap, an expensive one at that. I read lots of posts where people try to eliminate caps when possible. I know this may be subjective and dependent on the type of cap and its position within the circuit. Comments?
Mouser has some Hammond parts available for less than $20
Hammond Wire Lead Audio Transformers / Signal Transformers | Mouser
2Vrms ~= to +8dbu... not a ton of signal, most chassis mount units will be big enough. For experimenting anything around 10k:10k should be a good starting point for line level input.
Hammond Wire Lead Audio Transformers / Signal Transformers | Mouser
2Vrms ~= to +8dbu... not a ton of signal, most chassis mount units will be big enough. For experimenting anything around 10k:10k should be a good starting point for line level input.
Lundahl isn't high end in transformers. Lundahl has established a highly automated winding method for transformers and they aren't using the best winding techniques. Its just standard winding with different layers so that they are able to manufacture cheap. Of course they can't be so cheap as the asians as they are not manufacturing there, so what they charge for their trannies is the exact value what they are worth in the market.
Its a good and reputed manufacturer, not more and not less. If you want high end transformers then it comes to different names and winding techniques, that are much more time consuming and expect manual winding with highest precision. And you're in a complete different price league which has an open end. If you want cheaper units, look to asia. James etc. are offering not less than Lundahl but for cheaper prices.
Its a good and reputed manufacturer, not more and not less. If you want high end transformers then it comes to different names and winding techniques, that are much more time consuming and expect manual winding with highest precision. And you're in a complete different price league which has an open end. If you want cheaper units, look to asia. James etc. are offering not less than Lundahl but for cheaper prices.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.