One-Bottle Preamp
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kenrinc
Well-known member
I have the original schem on this but it doesn't show the OT. Was there an addendum for the 4:1 output tranny?
Ken-
Ken-
skipwave
Well-known member
[quote author="kenrinc"]I have the original schem on this but it doesn't show the OT. Was there an addendum for the 4:1 output tranny?
Ken-[/quote]
There's no change to the circuit, simply wire the output transformer as usual.
As shown on the No Feedback variant:
http://www.groupdiy.com/index.php?topic=16727
Ken-[/quote]
There's no change to the circuit, simply wire the output transformer as usual.
As shown on the No Feedback variant:
http://www.groupdiy.com/index.php?topic=16727
skipwave
Well-known member
[quote author="rotation"]Thanks Dave!
Here in Slovenia we can get only OEP transformers for cheap, nothing else. Do you know which one would be good for this preamp?[/quote]
OEP Data
a262a3c for input. If you want to be crafty, add a switch to change the secondaries from series to parallel. That will change the turns ratio between 1:6 and 1:12. Remember to change the load resistor to be appropriate for each ratio.
For output, I think you can wire the a262a2c as 4:1, but that model is really intended for lower impedance. Check with forum member "tonydB." I think he is distributing Edcor iron in the EU. People are reporting great results using the XSM10k:600.
PS: I'm just trying to lend Dave a hand fielding questions. I'm not an authority by any stretch of the imagination. :green:
Here in Slovenia we can get only OEP transformers for cheap, nothing else. Do you know which one would be good for this preamp?[/quote]
OEP Data
a262a3c for input. If you want to be crafty, add a switch to change the secondaries from series to parallel. That will change the turns ratio between 1:6 and 1:12. Remember to change the load resistor to be appropriate for each ratio.
For output, I think you can wire the a262a2c as 4:1, but that model is really intended for lower impedance. Check with forum member "tonydB." I think he is distributing Edcor iron in the EU. People are reporting great results using the XSM10k:600.
PS: I'm just trying to lend Dave a hand fielding questions. I'm not an authority by any stretch of the imagination. :green:
skipwave
Well-known member
[quote author="rotation"]Thanks!
Would you explain what would different ratios give me?[/quote]
Many things. Higher ratio means higher secondary impedance, more passive gain, and a change in the frequency response thus a different "tone." The impedance we can take higher, because the tube grid is very high impedance.
[quote author="rotation"]And why Dave used pot for di? Imepdance matching or it's volume control?
Miha[/quote]
Not a pot. That's how he draws a 1/4" jack. Use a switching jack, so that the input transformer secondary is disconnected when your instrument plug is inserted. That's the arrow pointing up to the jack in Dave's drawing.
Would you explain what would different ratios give me?[/quote]
Many things. Higher ratio means higher secondary impedance, more passive gain, and a change in the frequency response thus a different "tone." The impedance we can take higher, because the tube grid is very high impedance.
[quote author="rotation"]And why Dave used pot for di? Imepdance matching or it's volume control?
Miha[/quote]
Not a pot. That's how he draws a 1/4" jack. Use a switching jack, so that the input transformer secondary is disconnected when your instrument plug is inserted. That's the arrow pointing up to the jack in Dave's drawing.
Kingston
Well-known member
[quote author="skipwave"][quote author="kenrinc"]I have the original schem on this but it doesn't show the OT. Was there an addendum for the 4:1 output tranny?
Ken-[/quote]
There's no change to the circuit, simply wire the output transformer as usual.
As shown on the No Feedback variant:
http://www.groupdiy.com/index.php?topic=16727[/quote]
one might also want to experiment with eliminating the 220k tiedown resistor when using an output transformer. It's a small tweak but at least with the OEP a262a2c the sound was improved noticeably. I seem to remember there was discussion earlier on the thread that you only need the 220k tiedown for center tapped trafos (and for unbalanced use obviously).
Oh and by the way, I had to wire the a262a2c as 2:1 as a temporary solution (far from optimal). They can't handle the two bottle output as 4:1, and even for the one bottle they might only barely hold up.
I'm getting edcor for any future projects like this.
putting a switch on the input trafo to use it as 1:6 or 1:12 (parallel vs. serial) is an excellent tip by the way. I'm gonna do that for the no-feedback version I'm building at some point. I'm also very curious on how the cheap OEP input trafo sound will hold up against the jensens I have on the two bottles.
Ken-[/quote]
There's no change to the circuit, simply wire the output transformer as usual.
As shown on the No Feedback variant:
http://www.groupdiy.com/index.php?topic=16727[/quote]
one might also want to experiment with eliminating the 220k tiedown resistor when using an output transformer. It's a small tweak but at least with the OEP a262a2c the sound was improved noticeably. I seem to remember there was discussion earlier on the thread that you only need the 220k tiedown for center tapped trafos (and for unbalanced use obviously).
Oh and by the way, I had to wire the a262a2c as 2:1 as a temporary solution (far from optimal). They can't handle the two bottle output as 4:1, and even for the one bottle they might only barely hold up.
I'm getting edcor for any future projects like this.
putting a switch on the input trafo to use it as 1:6 or 1:12 (parallel vs. serial) is an excellent tip by the way. I'm gonna do that for the no-feedback version I'm building at some point. I'm also very curious on how the cheap OEP input trafo sound will hold up against the jensens I have on the two bottles.
skipwave
Well-known member
Thanks for chiming in Kingston. I thought it sounded dodgy to parallel those secondaries on the OEP.
And thanks for reminding me to try my output transformers without the 220k resistors.
And thanks for reminding me to try my output transformers without the 220k resistors.
kenrinc
Well-known member
Doh! I mean input... jeesh. I'm looking for a lower cost input tranny. 600:10K a possibility? Edcor has some options but no specific mic amp units.
Ken-
Ken-
NewYorkDave
Well-known member
You don't need the tiedown resistor with the transformer-coupled output. Think about it: the DC resistance of the xfmr primary is a couple hundred ohms at most. So, in that case, the resistor is serving no useful purpose.
It's ok now, i found layout from Nadege. Do you suggest two bottle if preamp is needed for dynamic and condenser microphones and tr. balanced input and output? I already have components for one bottle.
Miha
p.s.: id R8 330K or 330R?
Miha
p.s.: id R8 330K or 330R?
Hello here are my layout for the one bottle project:
http://www.twin-x.com/groupdiy/displayimage.php?album=lastup&cat=0&pos=0&uid=31
http://www.twin-x.com/groupdiy/displayimage.php?album=lastup&cat=0&pos=2&uid=31
Could you please check if it seems ok for you?
Thanks a lot
:wink:
http://www.twin-x.com/groupdiy/displayimage.php?album=lastup&cat=0&pos=0&uid=31
http://www.twin-x.com/groupdiy/displayimage.php?album=lastup&cat=0&pos=2&uid=31
Could you please check if it seems ok for you?
Thanks a lot
:wink:
enthalpystudios
Well-known member
check page one of this thread... also, any 1:10 mic input transformer will work fine.... simply adjust the zobel network on the seconday (the first two parts on the right side of the transformer, on the schematic) according to your transformer manufacturers datasheet.
[quote author="rotation"] Do you suggest two bottle if preamp is needed for dynamic and condenser microphones and tr. balanced input and output? [/quote]
The one-bottle actually has plenty of gain for dynamics unless you're recording somebody whispering or some such. It should have more than enough for condensors, & works well with ribbons in many circumstances. The input is transformer balanced, but the out is not. Unbalanced out is often not much of an issue. If you're running straight into A/D converters, I can't see it being an issue at all.
The one-bottle actually has plenty of gain for dynamics unless you're recording somebody whispering or some such. It should have more than enough for condensors, & works well with ribbons in many circumstances. The input is transformer balanced, but the out is not. Unbalanced out is often not much of an issue. If you're running straight into A/D converters, I can't see it being an issue at all.
skipwave
Well-known member
Yep, although 56dB of gain doesn't sound like a whole lot, I've rarely needed more.
With an SM57, you will have to use the pad on loud amps. With higher output ribbons like the Shinybox 46, you won't need the pad but you won't need the gain full up. With the Beyer M160 you will need all that gain, and, for acoustic strings, more.
I actually had a loud drummer in not long ago, and with oktava MC012 overheads I couldn't stop him from clipping the ADC. With 10dB pads on the mics and the 20dB pads on the OneBottle, the output (unbalanced plate out) was too hot for the converters. I could have just used the output transformers to step down the signal voltage, but the high frequencies sound airy-er from the unbalanced output. Damn he was pounding the snot out of those drums. :shock:
With an SM57, you will have to use the pad on loud amps. With higher output ribbons like the Shinybox 46, you won't need the pad but you won't need the gain full up. With the Beyer M160 you will need all that gain, and, for acoustic strings, more.
I actually had a loud drummer in not long ago, and with oktava MC012 overheads I couldn't stop him from clipping the ADC. With 10dB pads on the mics and the 20dB pads on the OneBottle, the output (unbalanced plate out) was too hot for the converters. I could have just used the output transformers to step down the signal voltage, but the high frequencies sound airy-er from the unbalanced output. Damn he was pounding the snot out of those drums. :shock:
[quote author="rotation"]Who has schematic for One Bottle pre?
I need something simple with easy to get transformers.
I already searched, but there are schems for particular transformers only...
Miha[/quote]
Big sorry guys, i made a mistake. I'm asking for PSU schematic for One Bottle. I would like to use simple to get transformers, because here in Slovenia we always have problems paying to other countrys. Would something like Gyraf's 220-12 and 12-220 work for this including fantom. Any scheme around?
I need something simple with easy to get transformers.
I already searched, but there are schems for particular transformers only...
Miha[/quote]
Big sorry guys, i made a mistake. I'm asking for PSU schematic for One Bottle. I would like to use simple to get transformers, because here in Slovenia we always have problems paying to other countrys. Would something like Gyraf's 220-12 and 12-220 work for this including fantom. Any scheme around?
