[EugeneK]

Hi,

I'm thinking of attempting to build a dual mono ladyday.
LD MK2 SET Dual Mono Amp | Diy HiFi Supply

This will be used to power a AKG K340 I have currently and hopefully a K1000 soon. DIY Hifi supply says that a few of these have been built to power K1000s through the speaker post binding method, but don't know if they've been used for other headphones.

I'm wondering if anyone else has used this amp for headphones which are easier to drive?

Thanks.

Eugene

 

[FallenAngel]

Looks serious, and expensive. Never heard of this kit, though I've heard nice things (or more correctly "audiophile talk") of the 300B.

More info would be appreciated from the regular tube gurus.

 

[Ferrari]

Well designed 300B transformer coupled amp can be very good. Unfortunately the output transformer of this amp is designed for speakers loads (4Ω-8Ω-16Ω). Therefore, the problem when using the amp to drive AKG K340/400Ω (IICR) or K1000/120Ω is the relative huge impedance mismatched. You will get “sound” out of your headphones however (but don’t ask what kind of sound...).

 

[EugeneK]

Quote:

Originally Posted by Ferrari /img/forum/go_quote.gif Well designed 300B transformer coupled amp can be very good. Unfortunately the output transformer of this amp is designed for speakers loads (4Ω-8Ω-16Ω). Therefore, the problem when using the amp to drive AKG K340/400Ω (IICR) or K1000/120Ω is the relative huge impedance mismatched. You will get “sound” out of your headphones however (but don’t ask what kind of sound...).

From what I've read on these forums, impedance matching is not important for headphones, just as long as the headphone's impedance exceeds or matches the source's impedance. (Source impedance > Headphone impedance = bad, everything else = ok)

Impedance matching is an issue for speakers, where you need a lot of power to be transfered, so the impedance match has to be good. It is not such a factor for headphones where you actually want the headphone's impedance to exceed the source's for better damping.

I got this from reading posts #3 and #4 of http://www.head-fi.org/forums/f4/hea...pedance-17238/

 

[dsavitsk]

Quote:

Originally Posted by Ferrari /img/forum/go_quote.gif Well designed 300B transformer coupled amp can be very good. Unfortunately the output transformer of this amp is designed for speakers loads (4Ω-8Ω-16Ω). Therefore, the problem when using the amp to drive AKG K340/400Ω (IICR) or K1000/120Ω is the relative huge impedance mismatched. You will get “sound” out of your headphones however (but don’t ask what kind of sound...).

All the mismatch means is that the inductance of the OPT rather than the reflected impedance will set the low frequency cut off. Otherwise, it should be fine.

You might want to try putting an 8R resistor in parallel with the phones (also try a 120R resistor in series -- some people like this (see the DNA amp)). Also, I wouldn't buy this solely as a headphone amp -- if you need a speaker amp, then this is a very nice kit and may double fine for phones. However, it may also have more hum than phones like -- an issue with 300b amps.

 

[Uncle Erik]

Quote:

Originally Posted by Ferrari /img/forum/go_quote.gif Well designed 300B transformer coupled amp can be very good. Unfortunately the output transformer of this amp is designed for speakers loads (4Ω-8Ω-16Ω). Therefore, the problem when using the amp to drive AKG K340/400Ω (IICR) or K1000/120Ω is the relative huge impedance mismatched. You will get “sound” out of your headphones however (but don’t ask what kind of sound...).

The K-1000 was designed to run from speaker taps; this should work fine.

However, as dsavitsk mentioned, you can get a bit of hum from a 300B amp. I've become much more fond of the 2A3 as a DHT for headphones.

What preamp would you plan to use with this?

 

[audiowize]

A 300B headphone amp is a killer idea, and I have tried mine on cans quite a bit. While mine work quite nicely, they have a DC supply for the 300B's to keep the noise down, and the LD does not. Also, the output impedance isn't really an issue with most transformer coupled preamps, even if the load impedance is lower than the source. This messes with the reflected impedance, but in a single ended amplifier the effect is often not audible (unless you really push it).

If you wanted to go this route, look for a 300B amp with a DC supply for the filaments and common mode chokes as filters. There are plenty of schematics out there, and the Bottlehead Paramount kit fits this bill. I will be picking up a pair of K-1000's this week to try on my own set of Paramounts.

 

[EugeneK]

Quote:

Originally Posted by audiowize /img/forum/go_quote.gif A 300B headphone amp is a killer idea, and I have tried mine on cans quite a bit. While mine work quite nicely, they have a DC supply for the 300B's to keep the noise down, and the LD does not. Also, the output impedance isn't really an issue with most transformer coupled preamps, even if the load impedance is lower than the source. This messes with the reflected impedance, but in a single ended amplifier the effect is often not audible (unless you really push it). If you wanted to go this route, look for a 300B amp with a DC supply for the filaments and common mode chokes as filters. There are plenty of schematics out there, and the Bottlehead Paramount kit fits this bill. I will be picking up a pair of K-1000's this week to try on my own set of Paramounts.

Seems like DIY hifi has one of those too: LUX SET Amplifier | Diy HiFi Supply

Correct me if i'm wrong.

 

[bcherry]

Quote:

Originally Posted by audiowize /img/forum/go_quote.gif A 300B headphone amp is a killer idea, and I have tried mine on cans quite a bit. While mine work quite nicely, they have a DC supply for the 300B's to keep the noise down, and the LD does not. ... If you wanted to go this route, look for a 300B amp with a DC supply for the filaments and common mode chokes as filters. There are plenty of schematics out there, and the Bottlehead Paramount kit fits this bill. I will be picking up a pair of K-1000's this week to try on my own set of Paramounts.

Paul (Audiowize) should disclose his association with Bottlehead, which he often promotes in this manner with disinformation about other products. He posts also under the Caucasian Blackplate moniker in AudioAsylum.
He was called out here at DIYaudio: post #79

DC supply on the LD: yes it does. And the LD series is one of the quietest 300b amps around.

Brian
DIY Hifi Supply

 

[audiowize]

Quote:

Originally Posted by EugeneK /img/forum/go_quote.gif Seems like DIY hifi has one of those too: LUX SET Amplifier | Diy HiFi Supply Correct me if i'm wrong.

Yes, if you add this module
DIYHIFS Filament Heaters (Pair) | Diy HiFi Supply you will hit the target noise specs. You can also inquire about Tentlabs DC modules although these seem to be very hit or miss. You want to look for under .500mv of hum on any directly heated amp you buy. Also, the available silk transformers have a 22 ohm tap that might be handy.

Also note that you can get more than enough power and probably better noise performance from a 2A3 amp than a 300B amp, and you need so little gain that you can really sit back and use just about any driver tube you want (think 12B4 to 2A3 or something along those lines) as a dedicated headphone amp.

If I had this as a primary task, I would look for a product that resembled this: Product Review