Looking through my tube stash I see that I have some 1635s. My impression is that they are somewhat like 6N7s but with substantial differences. I did a search here and don't see any discussion of this tube, so I'm curious - does this look useful or not? https://frank.pocnet.net/sheets/049/1/1635.pdf
I think those are useful. Plate curves of 1635 seem to be more pentode-like than 6N7.
Same type of (power)driver circuit than 6N7 is required. Also small positive bias to get linear operation.
Same type of (power)driver circuit than 6N7 is required. Also small positive bias to get linear operation.
I guess you can find such an OT, but with reduced freq. response.
https://edcorusa.com/collections/tube-amplifier-push-pull-output-transformer/primary-impedance_12k-ω
40 to 18K Hz
I generally figure 8K as the max for good freq. response. 10K starts getting shaky. There may well be more expensive OTs around that can do full range, but are they worth it for an unknown tube. A Junk-box/radio OT at high primary Z is likely to be low power rated and reduced freq. response.
Huh, I just looked at my OT list here, and I have one of those 12K Edcor OTs. I think I got it some while back so I could test wimpy tubes like sub-mini's.
https://edcorusa.com/collections/tube-amplifier-push-pull-output-transformer/primary-impedance_12k-ω
40 to 18K Hz
I generally figure 8K as the max for good freq. response. 10K starts getting shaky. There may well be more expensive OTs around that can do full range, but are they worth it for an unknown tube. A Junk-box/radio OT at high primary Z is likely to be low power rated and reduced freq. response.
Huh, I just looked at my OT list here, and I have one of those 12K Edcor OTs. I think I got it some while back so I could test wimpy tubes like sub-mini's.
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Paralleled, they might make nice voltage amplifiers. The 6N7 does, with a gain between a 6SN7 and a 6SL7, just right for some circuits. Don't know what the gain of the 1635 is, though, does anyone?
I was going to say choke load it to drive a bigger DHT but this tube needs some grid current too so you already need a beefy driver to begin with. So not much gained overall.
Well, maybe not as a driver. I was thinking first stage voltage amplifier, negatively biased.
gm around 625 uMho, Ra = mu/gm = 70/625 10^6 = 112000 Ohm.
Going to need a CCS load.
5755 tube is $6.50 on Ebay. Looks similar. mu 70, 1500 gm.
https://frank.pocnet.net/sheets/138/5/5755.pdf
Going to need a CCS load.
5755 tube is $6.50 on Ebay. Looks similar. mu 70, 1500 gm.
https://frank.pocnet.net/sheets/138/5/5755.pdf
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https://sklep.toroidy.pl/en_US/p/TT...kOhm-2xECL86-2xPCL86-Push-pull-or-similar/609
https://www.tme.eu/en/details/ttg-ecl86pp/toroidal-transformers/toroidy/
I've used and enjoyed them, and they are not expensive.
Maybe too much shipping costs for export..
https://www.tme.eu/en/details/ttg-ecl86pp/toroidal-transformers/toroidy/
I've used and enjoyed them, and they are not expensive.
Maybe too much shipping costs for export..
The Toroidy OT specs do look good. They must be using a sectionalized primary winding to keep distributed capacitance down. I can't find any reference to their winding patents. Or just using a toroid winder that can do progressive (chevron) winds.
The other way to get high Z with good bandwidth performance would be a Circlotron OT setup (1/2 the primary turns), but inconvenient B+.
Or a totem pole drive, but that doesn't set well with tubes (floating heater, one floating grid drive).
The other way to get high Z with good bandwidth performance would be a Circlotron OT setup (1/2 the primary turns), but inconvenient B+.
Or a totem pole drive, but that doesn't set well with tubes (floating heater, one floating grid drive).
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