did you calculate gain ?
anyway - I like big xconductance tube in that position .....
WOT preamp and battery charger
anyway - I like big xconductance tube in that position .....
WOT preamp and battery charger
HI,
I built a transformer coupled pre that was originally going to use 6j5Gs but sticker shock got me to wire it for ½ 6sn7. I still used two tubes but set it up so that the two channels used opposite triode sections. That actually worked out pretty well as I was able to get some good tube matches by swapping channels.
I built a transformer coupled pre that was originally going to use 6j5Gs but sticker shock got me to wire it for ½ 6sn7. I still used two tubes but set it up so that the two channels used opposite triode sections. That actually worked out pretty well as I was able to get some good tube matches by swapping channels.
I used a couple of types of vintage transformers, originally some rcas that were built by utc. They were very nice in the midrange but were limited on the bottom end, I switched them pretty quickly for utc ha133s which were much better in that regard.
My long term commercial reference is an ARC LS2, compared to that the sound was warm and full bodied but not in a bloated way. More musical is probably a good way to describe the difference. Vocals in particular had an uncanny realism compared to my reference, more of a “they are here” than a “you are there” presentation if that makes any sense
I listened to it until my marginal filament supply died and rather than rebuild it I am using the output transformers for a version using the 26. I’ve set that up so that if I can’t get the 26s quiet I can switch back to 6sn7s using the unregulated supplies and call it a day. I’m hoping that the 26s give me more of the more I got with transformer coupling but I really enjoyed the 6sn7s and if I need to switch back I’m ready to call it day in my preamp search.
What about the LTP 6H6Π circuit frustrated you so thoroughly? Just curious, I'm currently listening to a linestage with 6S4Π-EB as LTP and loaded with 20k:600 output TX's and find it quite nice.
cheers,
Douglas
Nothing wrong with the 6H6's. It's just that the LTP has IMHO an achilleas heal, namely the very high impedance point at the cathodes. High impedance - read very picky, unpredictable and sensitive. I found the current source dominating the sound, to the extend that I was solely listening to its effects. I tried bjt, mosfet plain and cascode and never was pleased enough...It's good to hear you have got good results out of it, but it is not my cup of tea...
Agree, don´t load with anything more than the following amp. The squarewaves won´t be as good as with loading but it will sound great.
revintage,
the cathodes junction is supposed to be a very high impedance node, or the CMR and output balance suffers and the raison d'etre of the LTP ceases to exist.
Analog_sa,
How is the tranny best loaded to tame its resonances? If it sounds horrible by a seamingly half-sensible loading, it seems to me a can of worms has been opened! What would you suggest?
Cheers
Last edited:
-----the cathodes junction is supposed to be a very high impedance node, or the CMR and output balance suffers and the raison d'etre of the LTP ceases to exist.
That is not entirely complete. Each cathode sees a parallel combination of the CCS and the other cathode. The CCS is very large compared to this value so it is not so high afterall.
cheers,
Douglas
That is not entirely complete. Each cathode sees a parallel combination of the CCS and the other cathode. The CCS is very large compared to this value so it is not so high afterall.
cheers,
Douglas
Tough question hollow_man. Having played with both 10 and 18mA 1660 i don't think i really like them. Quite recently i tried the 18mA (4.5:1) again in a line stage, this time with a 6H30 and ended up prefering the sound of a choke loaded, cap coupled stage. Interestingly, using a proper Lundahl plate choke produced absolutely no ringing and bandwidth of almost 100kHz while using the 1660 connected as a choke rang as hell. Loading the secondary certainly helped with the ringing but the bandwidth was much lower.
I think i agree with Mr Davenport's experiments - it's better to parafeed a nice transformer than to eliminate caps but use an ugly one. Anyone interested in two pairs 1660 cheap?
I think i agree with Mr Davenport's experiments - it's better to parafeed a nice transformer than to eliminate caps but use an ugly one. Anyone interested in two pairs 1660 cheap?
Anyone interested in two pairs 1660 cheap?
No way...too many stories of ringing 1660's for me( both locally and on line ). Now if the price could compete with an interesting rock I could always use another paperweight.
cheers,
Douglas
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.