[jaycalgary]

Just curious what type of output transformer do tube amps for headphones use?
I know that tube amps for speakers usually use output transformers with secondary at 4,8 or 16 ohms but the headphones I am looking at are 600 ohms.

I think there might be preamp output transformers that have 600 ohm out. Am I misguided on how this would work? It's pretty ambitious but I am looking to the future of what I would like to try for a set up and it is not very common on here I think.

I am thinking of upgrading to Beyerdynamic T1 in the future and I hear they will be great with tubes. I have a pair of old Cunningham 45 tubes I bought some time ago. Is it as simple as getting a good schematic and substituting the regular speaker type output transformers for one that would be 5k to 600 ohm? I probably should ask this on the "tube diy asylum"

 

[regal]

Quote:

Originally Posted by jaycalgary /img/forum/go_quote.gif Just curious what type of output transformer do tube amps for headphones use? I know that tube amps for speakers usually use output transformers with secondary at 4,8 or 16 ohms but the headphones I am looking at are 600 ohms. I think there might be preamp output transformers that have 600 ohm out. Am I misguided on how this would work? It's pretty ambitious but I am looking to the future of what I would like to try for a set up and it is not very common on here I think. I am thinking of upgrading to Beyerdynamic T1 in the future and I hear they will be great with tubes. I have a pair of old Cunningham 45 tubes I bought some time ago. Is it as simple as getting a good schematic and substituting the regular speaker type output transformers for one that would be 5k to 600 ohm? I probably should ask this on the "tube diy asylum"

pretty much but you have to watch gain, sometimes speaker amps have too much for headphones. You don't want much more than 15x gain after the OPT for headphones. As far as the OPT yes you would want a 5k/600, electra-print is a fine choice for westerners, they will quote about any config, you may want him to put a 32 ohm tap on it as well for low ohm phones.

The other issue is with DHT tubes you need to invest in a good DC filament supply, most folks just buy the tent labs modules as others are reported as being too noisy. A 71A is a good choice for a DHT tube amp because of the low filament current demands allows a less expensive filament supply.

 

[jaycalgary]

Thank for the advice I have been looking up as much as possible and have seen the 71a mentioned but have not found any schematics yet. Sounds like a few people have built this type of headphone amp.

 

[Parafeed]

Quote:

Originally Posted by jaycalgary /img/forum/go_quote.gif I think there might be preamp output transformers that have 600 ohm out.

Yes, you could use something like the Magnequest B7-5K (5K primary / 500R CT secondary) as an output transformer to drive a pair of T1's.

Quote:

Originally Posted by jaycalgary /img/forum/go_quote.gif I am thinking of upgrading to Beyerdynamic T1 in the future and I hear they will be great with tubes. I have a pair of old Cunningham 45 tubes I bought some time ago. Is it as simple as getting a good schematic and substituting the regular speaker type output transformers for one that would be 5k to 600 ohm? I probably should ask this on the "tube diy asylum"

The only thing is with the 45, you might want to bump the turns ratio a little. eg. 4:1. Rp is double that of say a 300B or 2A3. I'd prefer the reflected output impedance to be 100R or less. Without feedback and with a 5K:600R transformer, you're going to be in the 170R ballpark without considering the secondary DCR.