Kingston
Well-known member
I'm not touching the sidechain amp or transformers. the slight distortion they produce can be only a good thing for time constants.
jackies said:A number of people commented in this thread that the PM670 sound somewhat lacked and they wouldn't use it on master bus. Also a number of people said that Edcor transformers produce distortion and harsh highs or something...
So, how come nobody tried it with better transformers? I'm sure there have to be people with piles of Lundahls?
ChuckD said:Input stage uses UTC A15 to Edcors
SC input is UTC A15 to Edcors.
TheGuitarist said:Can i just ask what transformers got replaced? like T1/2/3/4? Just a bit confused with that. Correct me if i'm wrong but it seems like T1 and T3 were replaced yeah?
Or does anyone have suggestions for all of the transformers?
As the booster is fed with +17/-17, it can't go under -17V even with moding it and adding gain. The idea was only to add some current to charge the cap of the TC network, not to change the voltage swing.lewilson said:Yes, I wonder what voltage the sidechain puts out with the booster? Completely stock it is around -13 volts. My 660 clone can put out about 5 times this. and the 6k4p sounds great.
Im not sure the 6k4p will be the best tube for a stock pm
The 10K:600 must be designed for push/pull. 600/10K can be anything, but you have to check if no oscillation appears.TheGuitarist said:Hey would there be any problem using any other 600:10k/ 10k:600 transformer? Is there anything particularly special about the edcors? Thinking of buying some sowters or just anything that would be an upgrade really. Sowter have fairchild transformers, expensive but hey. Any other suggestions welcome. Carhnill maybe?
I just can't seem find any info on why (other than cost) the edcors were used.
lolo-m said:The 10K:600 must be designed for push/pull.
radiance said:Forgive me my ignorance...what is push/pull? And in what way are push/pull transformers wound differently?lolo-m said:The 10K:600 must be designed for push/pull.
lolo-m said:As the booster is fed with +17/-17, it can't go under -17V...
Something is on its way... but not for the PM...jackies said:I guess he refers to the center tap being used in 10k:600 and not being used in 600:10k (I don't have the schematic handy to confirm).
lolo-m said:As the booster is fed with +17/-17, it can't go under -17V...
I guess we need to come up with further boost then? How about high-voltage SCAB for 6k4p?
lolo-m said:radiance said:Forgive me my ignorance...what is push/pull? And in what way are push/pull transformers wound differently?lolo-m said:The 10K:600 must be designed for push/pull.
I'm not expert in transfo too ;D but here is what I know:
The Fairchild topology is entirely push-pull. That means that the plates current is entirely fed through the transformer.
PSU is connected to the center tad of the transformer primary and the polarisation current is always running into/trough the transformer. This means that the transformer must be able to handle the heat due to that current into its windings resistance. This means too that there's a magnetic polarisation into the transformer and is the core is magneticaly saturated by polarisation current you'll have distortion when you add audio current. I'm not really sure about this last point, so if I'm wrong please correct me .
The EDCOR handle both easily due to his 2,5W rating...
lolo-m said:- if 6BC8 was a really great varimu tube, I bet somebody would have made a great comp with it 30 years ago...
Great comp but 10 times cheaper than FC670 . Yes, it could be PM 670take a look at the Universal Audio 175b
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