NewYorkDave Mila Dual Tube Preamp Help Thread

[skal1]

? for those how have built this pre .


whats the lowest voltage i can use for c6 POLY FILM AXIAL, and can someone point me in the direction of these floating heater circuit.


cheers

skal1

 

[Rybow]

I am getting together all of the parts for this build, and I have a quick transformer question. I am looking at both the jensen transformers outlined in the BOM on the first page, and the Cinemag options discussed throughout the thread. I was hoping to get some pros and cons of both as I am not sure the Jensens would be worth the additional cost. The only thing I really know about Jensens is that the other audio guys I know always go "ooooooo, Jensen" when I mention it. I have only used OEP and Cinemags transformers so far in my DIY life.

Another quick Q. I am planning on building this into a 1U rack enclosure with a 12" depth. Would this be enough space to mount the power supply and transformer without introducing hum? I am going to be using the Hammond 269AX for power. I was planning on doing a separate power supply, but if I can fit it all in one case, that would be better.

Thanks

 

[lassoharp]

I am getting together all of the parts for this build, and I have a quick transformer question. I am looking at both the jensen transformers outlined in the BOM on the first page, and the Cinemag options discussed throughout the thread. I was hoping to get some pros and cons of both as I am not sure the Jensens would be worth the additional cost. The only thing I really know about Jensens is that the other audio guys I know always go "ooooooo, Jensen" when I mention it. I have only used OEP and Cinemags transformers so far in my DIY life.

Another quick Q. I am planning on building this into a 1U rack enclosure with a 12" depth. Would this be enough space to mount the power supply and transformer without introducing hum? I am going to be using the Hammond 269AX for power. I was planning on doing a separate power supply, but if I can fit it all in one case, that would be better.

Thanks

A 269AX in a 1 RU case?  It doesn't look like that's possible. The skinny side is 2.19in and center hole to center hole is 1.75in. It looks like it will hang off the back of a 2RU ok.

Probably have to go with a toroid for in-the-case.

Didn't like the Cinemags or just wanting to try something new?

Ever consider the Sowters or Lundahls?  Seems to be many around here who go "ooooo" for those.

They're all very good quality.  I've never heard anyone say the Jensen is clearly on a different level than any of the above as a grid transformer.

Jensen sells transformers and they also sell science.
.

 

[Rybow]

A 269AX in a 1 RU case?   It doesn't look like that's possible. The skinny side is 2.19in and center hole to center hole is 1.75in. It looks like it will hang off the back of a 2RU ok.

Probably have to go with a toroid for in-the-case.

Didn't like the Cinemags or just wanting to try something new?

Ever consider the Sowters or Lundahls?  Seems to be many around here who go "ooooo" for those.

They're all very good quality.  I've never heard anyone say the Jensen is clearly on a different level than any of the above as a grid transformer.

Jensen sells transformers and they also sell science.
.

Your right! For some reason I got all mixed up about how big a 1RU is. I seem to be having one of those days where my brain has totally turned off.   So its 2RU or 1RU with an external power supply.

I really like cinemags, but I do want to try some different transformers. One thing I want to get a grip on is the sound of different transformers. See what kind of different flavours are out there. The nice thing about the Jensens is that I can get them directly through Radial, which is a short bus ride away from where I live. I can actually get Lundahls locally as well, so maybe I'll check that option out. I am guessing the LL1935 would be good on the input? Not too sure about which one would work well on the output.

Thanks for the help! I can't wait to start this pre!

EDIT: So for the output transformer, it is not going to make a big difference what I use? Say if I slapped a fancy pants Lundahl or Jensen on the input, I could easily just use a cinemag on the output with no detriment.

 

[lassoharp]

Edcors are a popular choice for an OT.  Gobs of people on the forum have used them including NYDave on his builds.

Only catch is you'll have to wait 4 to 6 weeks but you can't beat the price.

 

[Rybow]

Thanks for all the info lassoharp. Much appreciated!

 

[poctop]

Thanks For everything
Dan

 

[poctop]

Yeps

 

[tchgtr]

Dan,
    Wow! Very nice build. I'm slowly assembling parts for something similar (but probably not nearly as well done), so please tell about your build. Edcors?
Green w/envy.
JW

 

[poctop]

Nop, input Cinemag CMMI-10C with a select switch for center tap 1/20 or 1/15 output cinemag CM9589L,
Currently comapring to UA 610,  Results looks promising,
will Ya Posted!

Dan

 

[pacemaker]

Hi Guys,
NewYorkDave,
i don't know if you're here,
But would you accept some PCB to be etched for this forum ?
Or do you prefer this project to stay for P2P ?
i'm not skilled enough to realise this project P2P,
but i would like to build a pair and Lukas can etch PCBs with schematics,
I hope you'll read this and i hope you will accept
that we etch some PCBs for the P2P neewbies like me ,
best regards,
francois

 

[Rybow]

Wow Dan! That is a beautiful build! I like your idea of using angle brackets for the tube sockets. Genius! Love the front panel too. I should get around to this one. Soon. Soon.

Just wondering about your VU meters. Can you just hook those directly to the input or output? Or do you need some type of buffer circuit in there.

 

[poctop]

For the Vu Meter i dont even know if something is required ( if So please the Real Guy Comments
For know i translated the concept of the 1176 so i connected directly to the output seems to work fine,

Since i am totally improvising I remove shorted
C7 of the circuit to see the impact on the feedback loop and the results were astonishing a nicer bass response and a perfectly swetened high end,  the only drawback for now is that whenever i use the range switch the meter goes wack a bit
but the sound is very much improve to my hear, probably all depend on my output Iron, 

if someones know about the Meter question let us know,
Cheers , 
Dan

 

[Rybow]

Alrighty. So I did some research, and the only requirement I see with strapping a VU meter across the outputs is a resistor (usually 3.6k) in series with the meter.  Just read an interesting article on the JLM site about it all. A buffer circuit can reduce the THD introduced by the meter, or convert a cheap DC meter into a VU meter. Good to know! I had always wondered about hooking up VU meters in circuits.

 

[poctop]

I'm on it ,

http://jlmaudio.com/AT51%20DIY%20VU.pdf

Nice piece of info,

Dan

 

[kante1603]

Just wondering about your VU meters. Can you just hook those directly to the input or output? Or do you need some type of buffer circuit in there.

Hi Insomniaclown,

I can highly recommend the JLM stuff too!
Done these a couple of times now and never had any issues in getting signals influenced by putting them across the outputs.
Also they are not expensive,very easy to build and the pcb is so small that you can hook them up direct to the back of nearly any meter you want.
There is a good build thread on Joe´s site and he himself is very helpfull!
The thread also covers things like how to set up the pcb when e.g. whether a meter has "on-board-rectification" or not.
Can be supplied by any voltage from 9 to 30 VDC and needs only about 10mAs current.

So simply use these and you´ll be fine!

Best regards,

Udo

 

[Rybow]

Thanks Udo for the info! Much appreciated. Its always great to hear about first hand experiences with stuff like this. I am certainly going to try it out on my next project. If I ever get the first one done that is. Thanks again!

Ryan

 

[kante1603]

You´re welcome Ryan
Udo.

 

[Matthew Jacobs]

Since i am totally improvising I remove shorted
C7 of the circuit to see the impact on the feedback loop and the results were astonishing a nicer bass response and a perfectly swetened high end,  the only drawback for now is that whenever i use the range switch the meter goes wack a bit
but the sound is very much improve to my hear, probably all depend on my output Iron, 

I was thinking of something similar and putting it on a switch on the front panel.

Anyway, can you be a little more specific, I don't really understand, did you remove C7 or did you short it?

 

[poctop]

Finally,  After Analazing All this with cold head,  i decided to stick,  with the original circuit,  but there is some room to experimentation with the Flavor of the Cap C7 and C6,  now i am in to check what kind of output my meter is supposed to read compare to the real output and findout if i should put that 3.6K upthere and if there is any THD differen ce between the two, 

Cheers,

Dan