I've read all that on Jacmusic's site 
. The guy even seems to be just around the corner from me, but I am not willing to pay his prices...
My theoratical knowledge is quite limited, I am more the builder and listener type. But as far as I know the output resistance in penthode mode is much, much higher and as such only suitable for preamplifier use. And believe me, C3G has plenty of gain even in triode mode... even with a "long" ratio for the output transformers they have enough gain... in fact I am planning to build a unity gain buffer used as pre because of that.
. The guy even seems to be just around the corner from me, but I am not willing to pay his prices...My theoratical knowledge is quite limited, I am more the builder and listener type. But as far as I know the output resistance in penthode mode is much, much higher and as such only suitable for preamplifier use. And believe me, C3G has plenty of gain even in triode mode... even with a "long" ratio for the output transformers they have enough gain... in fact I am planning to build a unity gain buffer used as pre because of that.
Hi Staffan,
I was referring to output transformers for headphone amplifiers in general.
Sowther has several dedicated opt's for either SE or Parafeed operation.
For my latest amp (C3G-SE) I am using Lundahl LL1689 at 9:1. I like it very much. Also suitable might be LL1630...
I wonder how a EDCOR - GXSE5-600-15K would do. What do you think?
Staffan
What for do you want them to use... for the original schematic of this thread or a different one?
My own personal and subjective experience is that headphone amplifiers are a bit more forgiving than amplifiers for speaker duty. I have used quite a range of different output transformers for headphone use: from vintage Grundig opt to custom made Reinhoefer opt to the aforementioned Lundahl. I liked all of them better than (big) capacitors in OTL-amplifiers
, and even the Grundig opt sounded quite nice with bass suffering the most in comparison to the more expensive other ones.I have also used simple Hammond transformers for parafeed duty (upon recommendation of Dsavitsk) and had very satisfactory results.
So yes, I think you can get very nice results with inexpensive output transformers... but again, what do you want to use them for.?
And btw... when I think about it: I could let go of the Reinhoefer opt that have multiple taps for numerous combinations and are wound on a M65 core...
just PM me when you are interested...
I had your nice and simple C3g shematic in mind. As this is a DIY community its always nice to find nice, simple and affordable solutions that is DIYable and doesnt dig a big black hole in the wallet. Thats why I looked at Edcors stuff, and that was the closest I found.
Personally I was interested because I have a bunch of C3gs and also a box of old tube radio OPTs. A friend of mine has a similar scrapbox and we once said that maybe we should see if we could find matching pairs. Some are 600 ohms secondary and almost all are SE gapped and my old Sennheiser DT 931 is about there.
Staffan
Cool Staffan!
I have my C3G-SE finished now and will snap a few pictures soon.
Running the C3G at about 145V and 16mA brings out the best of this tube (to my ears), and the new Salas HV boards make dialing in very easy.
When you find a pair of opt that present a similar load to the tubes as the Edcors it could make a nice amplifier!
Oliver
I have my C3G-SE finished now and will snap a few pictures soon.
Running the C3G at about 145V and 16mA brings out the best of this tube (to my ears), and the new Salas HV boards make dialing in very easy.
When you find a pair of opt that present a similar load to the tubes as the Edcors it could make a nice amplifier!
Oliver
Merlin el mago, can you send PCB layout without PSU to my email, please ?
m1007@yandex.ru
With regards,
Mikhail
m1007@yandex.ru
With regards,
Mikhail
Help Needed
I have built a point to point one of these, it sounds superb with no hum at all at full volume, however at about two thirds volume there is an audible hum. I have wired it using a star ground, isolated inputs with every ground connected to the star. It sounds like an earth loop but I have tried everything I can think of but am stumped. Any ideas?
Thanks for looking, any help appreciated.
I have built a point to point one of these, it sounds superb with no hum at all at full volume, however at about two thirds volume there is an audible hum. I have wired it using a star ground, isolated inputs with every ground connected to the star. It sounds like an earth loop but I have tried everything I can think of but am stumped. Any ideas?
Thanks for looking, any help appreciated.
Hi Merlin, Many thanks for replying, I had wired the earth in the style you illustrated. I was however just about to post that (even though I have been trying to fix this for ages) I have just cracked it. The fault was entirely of my doing, I had failed to ground the -ve of the DC heater supply leaving it floating. Grounding this has made it completely hum free at all volumes. What a great sounding design this is, it sounds superb through my vintage Koss Pro 4 headphones. Thanks again, Dave
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.