NewYorkDave
Well-known member
All right, now the WE pre has its own thread at last. And now this thread can die a quiet death due to lack of interest :wink:
One-Bottle Preamp
- Thread starter NewYorkDave
- Start date
Help Support GroupDIY Audio Forum:
rafafredd
Well-known member
I don´t think so.
skipwave
Well-known member
I won't let it die. Long live the One-Bottle! :green:
Ok, Dave. You talked me into the U-pad as shown in your schemo.
Here's my box:
Click here for larger image.
Click here for output options (notice the hi-tech labeling system).
Ok, Dave. You talked me into the U-pad as shown in your schemo.
Here's my box:
Click here for larger image.
Click here for output options (notice the hi-tech labeling system).
rafafredd
Well-known member
What am I seeing? A PCB?
NewYorkDave
Well-known member
Lookin' good. I think it's very cool that you put a small image in your post and linked to the larger image. I wish more people would do that!
Do I see a tube rectifier there, and a filter choke? Tell us what we're seeing :wink:
Do I see a tube rectifier there, and a filter choke? Tell us what we're seeing :wink:
kiira
Well-known member
[quote author="NewYorkDave"]Kiira, why not just use the Edcor 10K:600 you bought? It would be perfect. I was under the impression that that's what you had planned to do all along.[/quote]
Oh yeah. :shock: :? Good idea! ::slaps forehead:: I think I had put the idea asid e because it will be hard to fit and it isn't sheilded. Or more likely I just forgot. :razz: My brain doesn't keep me informed on how it comes to decisions it just makes them, mysteriusly.
Kiira
Oh yeah. :shock: :? Good idea! ::slaps forehead:: I think I had put the idea asid e because it will be hard to fit and it isn't sheilded. Or more likely I just forgot. :razz: My brain doesn't keep me informed on how it comes to decisions it just makes them, mysteriusly.
Kiira
skipwave
Well-known member
[quote author="rafafredd"]What am I seeing? A PCB?[/quote]
WYSWYG! :razz: Just kidding.
That's a scavenged PCB from a Dynaco PAM. I was going to just pull the sockets off, but decided it would work for this circuit. I only had to cut two traces, since the PAM used 6V on the heaters and I used 12.
[quote author="NewYorkDave"]Do I see a tube rectifier there, and a filter choke? Tell us what we're seeing[/quote]
Yep, 12X4. It's what I had lying around, and I wanted DC heaters so it pulls my 12.6VAC down to be rectified to a nice 12VDC. It was bought, along with the power transformer, and the filter caps-in-a-can, for a Dyna PAS project that never got started. The heaters are DC, 1n4006 rectifiers, and filtered by the big orange caps.
In the pic the boards weren't on standoffs yet, because I ran out of the short ones. :green:
WYSWYG! :razz: Just kidding.
That's a scavenged PCB from a Dynaco PAM. I was going to just pull the sockets off, but decided it would work for this circuit. I only had to cut two traces, since the PAM used 6V on the heaters and I used 12.
[quote author="NewYorkDave"]Do I see a tube rectifier there, and a filter choke? Tell us what we're seeing[/quote]
Yep, 12X4. It's what I had lying around, and I wanted DC heaters so it pulls my 12.6VAC down to be rectified to a nice 12VDC. It was bought, along with the power transformer, and the filter caps-in-a-can, for a Dyna PAS project that never got started. The heaters are DC, 1n4006 rectifiers, and filtered by the big orange caps.
In the pic the boards weren't on standoffs yet, because I ran out of the short ones. :green:
kiira
Well-known member
[quote author="skipwave"][quote author="rafafredd"]What am I seeing? A PCB?[/quote]
WYSWYG! :razz: Just kidding.
That's a scavenged PCB from a Dynaco PAM. I was going to just pull the sockets off, but decided it would work for this circuit. I only had to cut two traces, since the PAM used 6V on the heaters and I used 12.[/quote]
OMG! I was going to make a smartass comment that it looked like you had put a Dynaco board (from the color) in there by accident! :razz: :razz:
That's gone. Building Dave's pre from leftover PAM parts. :grin:
Kiira
WYSWYG! :razz: Just kidding.
That's a scavenged PCB from a Dynaco PAM. I was going to just pull the sockets off, but decided it would work for this circuit. I only had to cut two traces, since the PAM used 6V on the heaters and I used 12.[/quote]
OMG! I was going to make a smartass comment that it looked like you had put a Dynaco board (from the color) in there by accident! :razz: :razz:
That's gone. Building Dave's pre from leftover PAM parts. :grin:
Kiira
skipwave
Well-known member
[quote author="kiira"] Building Dave's pre from leftover PAM parts. :grin: [/quote]
What can I say? I'm ghetto like that.
My motto is "DIY w/o Buy." That means a lot of scrounging for parts.
What can I say? I'm ghetto like that.
My motto is "DIY w/o Buy." That means a lot of scrounging for parts.
skipwave
Well-known member
[quote author="Brown Note"]How do the values of the input xformer effect the values of the compensation network on the 12AV7 pre? A mathematical solution would really help me out here.[/quote]
Hopefully you are still reading. Check out this thread for great info on testing and determining your Zobel network values:
http://www.groupdiy.com/index.php?topic=1221
Hopefully you are still reading. Check out this thread for great info on testing and determining your Zobel network values:
http://www.groupdiy.com/index.php?topic=1221
skipwave
Well-known member
An update and a question.
I wired up the Triad A69J output TXs and they work nicely. I used these preamps on guitar amp and drum room and was very pleased with the results. No padding was needed, but gain stayed on the lowest setting with ample output level. I didn't have time to compare the tonal differences with and without the output iron, though I used switching jack for bypassing the TXs. Thanks again Dave, this design sounds sweet!
Now the question. I spent some time crunching the numbers to re-calculate the resistor values for the B+ supply. My tranny has a higher voltage secondary than Dave's prototype, 660CT. I calculated a 140V drop across a 10K resistor at 14ma plate current for two AV7s, but it metered about 110V. Based on this, I ended up just omitting R13, and running with:
TX -> 12X4 -> C40uF -> R10k -> C40uF -> B+ to tubes.
The actual voltages applied to the tubes metered almost perfectly to what is shown on the schemo, but would my B+ be cleaner/quieter if I replaced the R10k with 4.7k and added R13 back in at 4.7k?
Let me know if I'm not making any sense. My main concern is that I only have one resistor on the B+ rail before it hits the plate resistors.
I wired up the Triad A69J output TXs and they work nicely. I used these preamps on guitar amp and drum room and was very pleased with the results. No padding was needed, but gain stayed on the lowest setting with ample output level. I didn't have time to compare the tonal differences with and without the output iron, though I used switching jack for bypassing the TXs. Thanks again Dave, this design sounds sweet!
Now the question. I spent some time crunching the numbers to re-calculate the resistor values for the B+ supply. My tranny has a higher voltage secondary than Dave's prototype, 660CT. I calculated a 140V drop across a 10K resistor at 14ma plate current for two AV7s, but it metered about 110V. Based on this, I ended up just omitting R13, and running with:
TX -> 12X4 -> C40uF -> R10k -> C40uF -> B+ to tubes.
The actual voltages applied to the tubes metered almost perfectly to what is shown on the schemo, but would my B+ be cleaner/quieter if I replaced the R10k with 4.7k and added R13 back in at 4.7k?
Let me know if I'm not making any sense. My main concern is that I only have one resistor on the B+ rail before it hits the plate resistors.
NewYorkDave
Well-known member
Skip,
I'm not sure I follow. The two channels are still individually decoupled with 10K and a filter cap, right? The raw B+ from the input filter cap should go through at least two poles of filtering before it gets to the tubes, and the last pole should be separate for each channel.
I'm glad to hear you're getting good results from the circuit. Got any pics or clips of the finished product?
If you want to run the gain higher and keep the output level under control, a 600-ohm pad (fixed or switchable) after the output TX is always a good option.
I'm not sure I follow. The two channels are still individually decoupled with 10K and a filter cap, right? The raw B+ from the input filter cap should go through at least two poles of filtering before it gets to the tubes, and the last pole should be separate for each channel.
I'm glad to hear you're getting good results from the circuit. Got any pics or clips of the finished product?
If you want to run the gain higher and keep the output level under control, a 600-ohm pad (fixed or switchable) after the output TX is always a good option.
skipwave
Well-known member
[quote author="NewYorkDave"]I'm not sure I follow. The two channels are still individually decoupled with 10K and a filter cap, right? The raw B+ from the input filter cap should go through at least two poles of filtering before it gets to the tubes, and the last pole should be separate for each channel. [/quote]
Thanks for the reply Dave. That's what I was concerned about. I need to add an RC pole for each then. The problem I'm facing is that based on the voltage drop that I'm seeing across the 10k resistor, I will have to go with lower resistor values or my plate voltages will be low.
Would it be acceptable to have a 2.2k on the first pole between the 40uF caps, followed by a seperate pole for each channel?
I'll post clips soon and a finished pic.
Thanks for the reply Dave. That's what I was concerned about. I need to add an RC pole for each then. The problem I'm facing is that based on the voltage drop that I'm seeing across the 10k resistor, I will have to go with lower resistor values or my plate voltages will be low.
Would it be acceptable to have a 2.2k on the first pole between the 40uF caps, followed by a seperate pole for each channel?
I'll post clips soon and a finished pic.
NewYorkDave
Well-known member
skipwave
Well-known member
Dave, you are a rock star! :sam: :sam: :sam: :thumb:
I will fix up my power supply tonight. Amazingly I really like the tracks I recorded with it over the weekend. I'm sure it will be even better with an up-to-spec PS.
I will fix up my power supply tonight. Amazingly I really like the tracks I recorded with it over the weekend. I'm sure it will be even better with an up-to-spec PS.
skipwave
Well-known member
I fixed up the PS as shown above. I adjusted the 8.2k down to 6.9k (a 4k7 and 2k2 in series). I think I finally grasp how this works and understand the voltage drop is halved with the current draw, feeding one tube vs. two.
The voltages at the plates are metering about 5V below the design, but my apartment's mains voltage measures 107V, so on a proper 110-120V line these would come up a touch.
The voltages at the plates are metering about 5V below the design, but my apartment's mains voltage measures 107V, so on a proper 110-120V line these would come up a touch.
Kingston
Well-known member
Hi from NYD two-bottle newbie land.
I'm finally making two channels of the two-bottle pre, and when ordering some of the last parts, ran into a bit of trouble. The PSU transformer. As of now I couldn't find a perfect match, but how about something like this to power the two channels:
35VA toroidal 230// 6,3V 2A / 215-0-215V 0,05A
too small?
or
143VA toroidal 230 V // 280-0-55-280V 0,15 A / 6,3 V 7 A / 5V 3A
way too big? or maybe I should keep looking still?
When I ordered some 12AV7's, I was suggested to use the 5965A instead. The tube guy said it is basically an improved design of the 12AV7. Just for kicks, I ordered one for swap-in testing, but what do you guys think about it?
Regarding the stepped unbalanced attenuator, does it go before or after the output transformer? I suspect it goes before the trafo, but just making absolutely sure.
Oh by the way, the two channels won't be identical, I already got jensen transformers for the other channel, and haven't still decided what to use for the other. Would these OEP's be good http://www.farnell.com/datasheets/9126.pdf
1+1:6.45+6.45 for the input, 1+1:2+2 model (turned around) for the output? Gyraf G9 uses these so I thought they have to be pretty ok.
Cheers,
Mike
I'm finally making two channels of the two-bottle pre, and when ordering some of the last parts, ran into a bit of trouble. The PSU transformer. As of now I couldn't find a perfect match, but how about something like this to power the two channels:
35VA toroidal 230// 6,3V 2A / 215-0-215V 0,05A
too small?
or
143VA toroidal 230 V // 280-0-55-280V 0,15 A / 6,3 V 7 A / 5V 3A
way too big? or maybe I should keep looking still?
When I ordered some 12AV7's, I was suggested to use the 5965A instead. The tube guy said it is basically an improved design of the 12AV7. Just for kicks, I ordered one for swap-in testing, but what do you guys think about it?
Regarding the stepped unbalanced attenuator, does it go before or after the output transformer? I suspect it goes before the trafo, but just making absolutely sure.
Oh by the way, the two channels won't be identical, I already got jensen transformers for the other channel, and haven't still decided what to use for the other. Would these OEP's be good http://www.farnell.com/datasheets/9126.pdf
1+1:6.45+6.45 for the input, 1+1:2+2 model (turned around) for the output? Gyraf G9 uses these so I thought they have to be pretty ok.
Cheers,
Mike
> 35VA toroidal 230// 6,3V 2A / 215-0-215V 0,05A
215-0-215 with a silicon rectifier (two 1N1008) will give 300 Volts raw DC. You don't have the large drop down from 400V to "waste" in R-C filtering, you will need to use smaller value resistors and much larger capacitors.
I don't know which of the many variants is in play today. Looking at the first post of this thread, NYD shows a 10K resistor running from a 300V source to a 235V B+ rail. Split the 10K into three 3K3 in series, and put 40uFd to ground at each junction. That should be clean enough. That and your 6V 2A heater winding should be plenty of power for one 2-bottle amp, maybe OK for two channels.
> I was suggested to use the 5965A instead. The tube guy said it is basically an improved design of the 12AV7.
A) Always beware of the friendly salesman who wants to sell you something other than what you asked for. He may be quite right, he may only be well-meaning, or he may be sitting on a crate of 5965 that he needs to unload. True, most triode amps are fairly un-fussy, but NYD thought hard about this one and you would not want to deviate without a full understanding.
B) Discussed and debated (maybe refuted) here.
215-0-215 with a silicon rectifier (two 1N1008) will give 300 Volts raw DC. You don't have the large drop down from 400V to "waste" in R-C filtering, you will need to use smaller value resistors and much larger capacitors.
I don't know which of the many variants is in play today. Looking at the first post of this thread, NYD shows a 10K resistor running from a 300V source to a 235V B+ rail. Split the 10K into three 3K3 in series, and put 40uFd to ground at each junction. That should be clean enough. That and your 6V 2A heater winding should be plenty of power for one 2-bottle amp, maybe OK for two channels.
> I was suggested to use the 5965A instead. The tube guy said it is basically an improved design of the 12AV7.
A) Always beware of the friendly salesman who wants to sell you something other than what you asked for. He may be quite right, he may only be well-meaning, or he may be sitting on a crate of 5965 that he needs to unload. True, most triode amps are fairly un-fussy, but NYD thought hard about this one and you would not want to deviate without a full understanding.
B) Discussed and debated (maybe refuted) here.
Kingston
Well-known member
> [5965A] Discussed and debated (maybe refuted)
Oh dear! This thread is getting a bit long. I remember reading that now that I saw it again. 5965A seems well suited to what I'm after here: slightly different coloration to accompany the "true to design" jensen/12AV7 enabled channel. :wink:
Now if I could only find a better suited PSU transformer. I'd rather not build an underpowered box now that I still have the choice.
Oh dear! This thread is getting a bit long. I remember reading that now that I saw it again. 5965A seems well suited to what I'm after here: slightly different coloration to accompany the "true to design" jensen/12AV7 enabled channel. :wink:
Now if I could only find a better suited PSU transformer. I'd rather not build an underpowered box now that I still have the choice.
NewYorkDave
Well-known member
[Look again]
