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noDAC DHT output stage
noDAC DHT output stage
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Old 3rd March 2019, 11:34 AM   #11
kokoriantz is offline kokoriantz  Lebanon
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Why not isolating transformer 10k/40k (about 40$ a pair on Aliexpress) and cathode follower as 6N1p for example?
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Old 3rd March 2019, 11:36 AM   #12
merlin el mago is offline merlin el mago  Europe
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I want DHT, yes I'm contemplating also a step up 1:2 transformer without DHT output stage, but I'm lost looking for proper step up transformer?

Last edited by merlin el mago; 3rd March 2019 at 11:39 AM.
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Old 3rd March 2019, 11:42 AM   #13
analog_sa is offline analog_sa  Europe
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noDAC DHT output stage
Instead of building some half baked DHT output for this very dubious project, why don't you build a no-compromise DHT preamp which will work with the nodac but also work with any future projects too? It will very likely be transformer coupled and this will also take care of filtering >100kHz.
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Old 3rd March 2019, 11:44 AM   #14
merlin el mago is offline merlin el mago  Europe
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I have one: 26 preamp, but will be great to have the same gain like the Valve Itch phono preamp.

My 26 is choke loaded, I prefer the sound over OPT.
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Old 3rd March 2019, 04:23 PM   #15
Koifarm is offline Koifarm  Netherlands
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The filter has first corner frequency at about 23khz and second at 64khz. The 1k5 resistance i tune the transformer i had behind the filter.
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Old 3rd March 2019, 04:24 PM   #16
Tjj226 is online now Tjj226
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I will offer 3 ideas.

1: If all you have to do is basically double the voltage, I would just use a step up transformer. A step up transformer is going to do a better job than a tube ever could.

2: If you have to use a tube and it has to be a DHT, I would look into the 300b. Theoretically it could be configured to give you 600 ohms for the output impedance which might have some neat applications.

3: If you want a tube, but would be willing to consider an indirectly heated triode, then a 6as7g might be neat *shrug*

Quote:
Originally Posted by merlin el mago View Post
I want DHT, yes I'm contemplating also a step up 1:2 transformer without DHT output stage, but I'm lost looking for proper step up transformer?
I would just shoot sowter an email. If you show them what you are up to, they can recommend you a decent transformer.
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Old 3rd March 2019, 04:49 PM   #17
merlin el mago is offline merlin el mago  Europe
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Quote:
Originally Posted by Koifarm View Post
The filter has first corner frequency at about 23khz and second at 64khz. The 1k5 resistance i tune the transformer i had behind the filter.
I supposed did you used a 4th order low pass filter.

Quote:
Originally Posted by Tjj226 View Post
I will offer 3 ideas.

1: If all you have to do is basically double the voltage, I would just use a step up transformer. A step up transformer is going to do a better job than a tube ever could.

2: If you have to use a tube and it has to be a DHT, I would look into the 300b. Theoretically it could be configured to give you 600 ohms for the output impedance which might have some neat applications.

3: If you want a tube, but would be willing to consider an indirectly heated triode, then a 6as7g might be neat *shrug*
1: Interested what I don't want a custom step up transformer to avoid high prices.

2: 300B is a expensive DHT & I guess I didn't need that gain.

3: Used the 6AS7 as output in a headphone amp but I prefer DHT.

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Originally Posted by Tjj226 View Post
I would just shoot sowter an email. If you show them what you are up to, they can recommend you a decent transformer.
See post 19 mine answer 1

Quote:
Originally Posted by Koifarm View Post
The filter has first corner frequency at about 23khz and second at 64khz. The 1k5 resistance i tune the transformer i had behind the filter.
Could you elaborate why you chosen two corner frequencies and what's the final Fc?
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Old 3rd March 2019, 06:26 PM   #18
analog_sa is offline analog_sa  Europe
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Quote:
Originally Posted by merlin el mago View Post
choke loaded, I prefer the sound over OPT.
Curiously, so did i. At least while being stuck in the Lundahl swamp
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Old 3rd March 2019, 06:29 PM   #19
merlin el mago is offline merlin el mago  Europe
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Yes I use LL1660 as choke as suggested by Andy Evans connecting all the primaries
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Old 3rd March 2019, 06:34 PM   #20
analog_sa is offline analog_sa  Europe
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Curiously this is something else i've tried a long time ago. A proper choke, such as the 1668 slaughters the 1660 in this position. Unlike the transformer used as a choke, the proper choke allows for unmolested square waves too.
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