I can understand that, because above that the air becomes very thin. I'm not a transformer mystic, but certain transformers really do require rare components and, above all, knowledge. It's not easy to build such gems, it requires a lot of experience and careful consideration of all the important parameters. The whole thing is a compromise at the highest level, it's a great pity that a lot of expertise and experience has been lost in this area in recent years.They use 1:10 input trafos.
Stop giving away all the good secrets CJ!!!!Original 76 has that 1:30 input wrapped in a ton of mu metal,
A Jensen 1:10 sounds better than the stock 1:30 to me at least. And there is plenty of gain to make up for the ratio.
I told Ollie this and he started to offer his 76 with a 1:10.
It’s difficult to make a good transformer with that high of a ratio, I’m surprised when it works, I believe 1:10 is about all that should be made, not sure why you’d need a bigger ratio outside of phono cartridges or something, but I agree would have expected better too.I think CJ was right when he said that he doesn’t know any good 1:30 transformers of current production.
Cinemag openly tells that they don’t make mic trafos with such a high ratio.
I’m very disappointed with Sowter, frankly. This is not how a professional manufacturer should behave. It clearly shows that they haven’t tested their replacement transformer in real circuit.
Good evening gentlemen,
about a year ago a had a job in Berlin and for a week I was commuting every morning and evening for a bit more than 30 minutes. I cant recall why I started to draw the V76 schematic in spice but a some point I had a well working model of the preamp. I played around with that model to get to know the circuit better. Also I read through the V76 threads here in GDIY and gathered quite a bit knowledge about the preamp. During the past year I could gather two Sowter V76 input transformers and four Lundahl anode chokes on Ebay. Output will be some Edcor iron I have here. From the U23 build I have power transformers and a PSU PCB what could do the job.
So I plan to build a stereo unit with PSU included. PSU is regulated with DC filaments. I needed to extend the PSU and designed a voltage quadrupler 12 -> 48V. I am quite curious if this will work. I designed pcbs along the tips and tricks I found in the other V76 threads. I integrated a DI input, skipped all the filter stages. Added in and output pad.
I will use EF86 or PF86 instead of the EF804. All capacitors in the signal path are film. Front panel comes from Frank. He did an awesome job again. I will drive the VUs from a chines VU buffer. The PCBs offers two positions to hook it up. I ll see what works best.
Today I assembled the front panel. Thanks again @gyraf for the knobs. I still live off of them. I will stuff the PSU PCB the next days and make a documentation of the build here. I hope you people enjoy the thread.
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