Stagefright13
Well-known member
Dummy me just noticed 1108 boards are in stock in the Mnats White market. I'll take 2 when ya get back Mnats!
John
John
[BUILD] 1108 DIY project and PCB layout
- Thread starter mnats
- Start date
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dmp
Well-known member
Very interested in this - especially info on the inductor values.
After using this preamp in my rack I can report that I really like it. Low noise, nearly flat frequency response (measured a little bump ~.5dB at ~14 kHz).
It is a lower gain preamp, so keep that in mind - measured 40 dB gain.
Again, my build info - since I've gotten some email questions:
- I used a UTC O-2 input transformer, terminated with 100k, no zobel
- EA 5002 output transformer from Hairball Audio
- I skipped the LDR because it is just being used as a input voltage divider with R2. I replace both components with a pot (1meg audio). I have found this to be fine.
edanderson
Well-known member
Praqtice said:this is great... so inspiring.
i've been thinking these are perfect for send/receive amps in a homebrew cooper time cube. would need 4 of them. then maybe another 2 just for mics/line.
pre and post emphasis 509 eq's in time cube 1109 amps seem to work on the same feedback loop idea as in 1108/508, am i right?
sam
yes but no. the 1109 is class AB and has more output drive capability than the 1108 which is class A. the 1108 will make a very nice fixed gain mic amp, and yes it could be added onto to make an eq. but i would not count on it to drive a speaker, even a very small one. it could work, but just because the number is one off, doesn't mean they are that similar.
of course, with the available rev F output transformers, you could build an 1109, just noone has made a PCB yet.
ed
Stagefright13
Well-known member
Researching this now for a build. Anyone know what the original input transformer was? Or at least the ratio? And what the original gain across the entire amp was. 40 db? Good enough for me with condensers.
Just don't wanna overload the input with hot mics. Old UA stuff does that. JBL Pro site has no schematic. Just the 1109. Back then mics didn't have the output they do now. I'm sure I could pad it down tho. But using the original IN tranny or at least the correct ratio would be cool. The original sounds nice and would like to emulate that as diy. Not afraid to experiment!!! Just need a small amount more info.
Anyone have an original? dissonantstring said his friend was selling the originals. Got any pics?
John
Just don't wanna overload the input with hot mics. Old UA stuff does that. JBL Pro site has no schematic. Just the 1109. Back then mics didn't have the output they do now. I'm sure I could pad it down tho. But using the original IN tranny or at least the correct ratio would be cool. The original sounds nice and would like to emulate that as diy. Not afraid to experiment!!! Just need a small amount more info.
Anyone have an original? dissonantstring said his friend was selling the originals. Got any pics?
John
Stagefright13
Well-known member
Thanks Gevermil! Here is the pdf: stagefrightrecords.com/1108.pdf
And here is a pic: http://recforums.prosoundweb.com/index.php/fa/4356/0/
And another: http://www.uaudio.com/webzine/2004/march/graphics/1108_module.jpg
Seems it has up to 50 db gain. Can't wait.
What is UA using for the input tranny on the 2108? Is it the same as I have heard they use on the 2-610?
John
And here is a pic: http://recforums.prosoundweb.com/index.php/fa/4356/0/
And another: http://www.uaudio.com/webzine/2004/march/graphics/1108_module.jpg
Seems it has up to 50 db gain. Can't wait.
What is UA using for the input tranny on the 2108? Is it the same as I have heard they use on the 2-610?
John
mjk
Well-known member
Very cool! The first part of that file is identical to the Studio Electronics bulletin SE-08 I have. As soon as I get my scanner going I'll scan the 508 sheets; no inductor values anywhere I can find though
I do have a pair of 1108 and a 508 I will open up and photograph, take part numbers, etc.
I'm planning on racking these and would sure like to come across a second 508 with a decent frontplate.
I do remember about 1/2 the inside volume was transformers! A UTC input transformer and some huge output iron would be true to form for that time period. You can drive headphones from these with a suitable matching transformer.
Cheers,
Michael
I do have a pair of 1108 and a 508 I will open up and photograph, take part numbers, etc.
I'm planning on racking these and would sure like to come across a second 508 with a decent frontplate.
I do remember about 1/2 the inside volume was transformers! A UTC input transformer and some huge output iron would be true to form for that time period. You can drive headphones from these with a suitable matching transformer.
Cheers,
Michael
mjk
Well-known member
Here they are. The 1108 transformers are probably BPMC as on the 1109 shown. The can looks like a UTC can sort of...
Still no inductor values...
Cheers!
508 Schematic-large file 500KB:
http://www.electrolyre.com/webpics/508-schematic.jpg
508 PCB and assembly dwg large file 500KB:
http://www.electrolyre.com/webpics/508-PCB.jpg
pic of 508 module bottom side PCB:
http://www.electrolyre.com/webpics/508-botPCB.jpg
pic of 508 module top side PCB:
http://www.electrolyre.com/webpics/508-topPCB.jpg
pic of 1108 module bottom side PCB:
http://www.electrolyre.com/webpics/1108-BotInside.jpg
pic of 1108 module top side PCB: (The "TRW" style card edge connectors for these are still being made!)
http://www.electrolyre.com/webpics/1108-TopInside.jpg
another 1108 schematic with different part values:
http://www.electrolyre.com/webpics/1108-altschem.jpg
pic of an 1109:
http://www.electrolyre.com/webpics/1109-TopPCB.jpg
Still no inductor values...
Cheers!
508 Schematic-large file 500KB:
http://www.electrolyre.com/webpics/508-schematic.jpg
508 PCB and assembly dwg large file 500KB:
http://www.electrolyre.com/webpics/508-PCB.jpg
pic of 508 module bottom side PCB:
http://www.electrolyre.com/webpics/508-botPCB.jpg
pic of 508 module top side PCB:
http://www.electrolyre.com/webpics/508-topPCB.jpg
pic of 1108 module bottom side PCB:
http://www.electrolyre.com/webpics/1108-BotInside.jpg
pic of 1108 module top side PCB: (The "TRW" style card edge connectors for these are still being made!)
http://www.electrolyre.com/webpics/1108-TopInside.jpg
another 1108 schematic with different part values:
http://www.electrolyre.com/webpics/1108-altschem.jpg
pic of an 1109:
http://www.electrolyre.com/webpics/1109-TopPCB.jpg
Stagefright13
Well-known member
Awesome info and pics! Thanks MJK!
Here's a thread from here with some info on the in transformer: http://www.groupdiy.com/index.php?action=printpage;topic=32729.0
Interesting post here:
OK, here's "some" info regarding the input transformer for the 1108, 1008 and 1016. Enough to get you close anyway.
Spec calls for:
Primary Z of 600, 150 and 37.5 ohms.
Primary being Bifilar wound.
Secondary Z of 65K +/- 2K although the Peerless version measured 70K - shock!!!!
Core may be EI-375 HYMU .014 3/8" stk or equiv.
Various manufacturers used and the internal part numbers:
Microtran: Micro W5127
Also Microtran M1-A
Peerless: 4786
UTC: 6448
EE (Electro Engineering Works): EE4786-E14650
I have windings DCR of the UTC, the Peerless and the EE but not the Microtrans. Not much between them but the Peerless measures higher on all windings.
A UTC 0-1 was also considered and tested but not used.
I have an 0-2 UTC I was gonna use for a tube pre. I think I will try that first as DMP has done. With my limited knowledge it looks like it is in the ballpark. Wish I knew more about transformers. Gonna have to do more studying.
John
Here's a thread from here with some info on the in transformer: http://www.groupdiy.com/index.php?action=printpage;topic=32729.0
Interesting post here:
OK, here's "some" info regarding the input transformer for the 1108, 1008 and 1016. Enough to get you close anyway.
Spec calls for:
Primary Z of 600, 150 and 37.5 ohms.
Primary being Bifilar wound.
Secondary Z of 65K +/- 2K although the Peerless version measured 70K - shock!!!!
Core may be EI-375 HYMU .014 3/8" stk or equiv.
Various manufacturers used and the internal part numbers:
Microtran: Micro W5127
Also Microtran M1-A
Peerless: 4786
UTC: 6448
EE (Electro Engineering Works): EE4786-E14650
I have windings DCR of the UTC, the Peerless and the EE but not the Microtrans. Not much between them but the Peerless measures higher on all windings.
A UTC 0-1 was also considered and tested but not used.
I have an 0-2 UTC I was gonna use for a tube pre. I think I will try that first as DMP has done. With my limited knowledge it looks like it is in the ballpark. Wish I knew more about transformers. Gonna have to do more studying.
John
tomas1808
Well-known member
Hi. What power supply do you recommend for this preamp?
Newbie here
EDIT: Is the mnats "FS900+" PS good for this?
Newbie here
EDIT: Is the mnats "FS900+" PS good for this?
tomas1808
Well-known member
hello?
tomas1808 said:
tomas1808 said:hello?
This forum has been around for quite a while now and there are few, if any, questions that haven't been answered before. Try doing a search before posting a question and you might get a quicker result. I found a few relevant posts on this topic by punching in a few key words.
tomas1808
Well-known member
Yes. For some reason I thought all posts about the 1108 were in this thread.
After searching I found all the information I needed! Thanks.
BTW I will be ordering a 1108 PCB soon.
After searching I found all the information I needed! Thanks.
BTW I will be ordering a 1108 PCB soon.
tomas1808
Well-known member
Another question:
What would be a suitable input transformer apart from the CMMI-7C? (too damn expensive, especially If I add custom taxes, ends up costing about 160 dollars a piece :-X)
What would be a good alternative?
Thanks!
(Searched without useful results)
What would be a suitable input transformer apart from the CMMI-7C? (too damn expensive, especially If I add custom taxes, ends up costing about 160 dollars a piece :-X)
What would be a good alternative?
Thanks!
(Searched without useful results)
Echo North
Well-known member
Hi,
Around the first of the year (4-5 weeks) I'll have some input transformers in stock for the Peter Purpose LA3A. This input would actually work well in the 1108.
They are not cheap but will be better than the current options.
Thanks,
Mike
Around the first of the year (4-5 weeks) I'll have some input transformers in stock for the Peter Purpose LA3A. This input would actually work well in the 1108.
They are not cheap but will be better than the current options.
Thanks,
Mike
tomas1808
Well-known member
Great, I will check it up!
I will also order a EA-5002 output transformer when they are back in stock
Thanks for the info!
I think this project lacks some good build reports, pics, tranny selection, layout.
Anyone?
I will also order a EA-5002 output transformer when they are back in stock
Thanks for the info!
I think this project lacks some good build reports, pics, tranny selection, layout.
Anyone?
Stagefright13
Well-known member
I found 300 ohm pots here but 1/8 shafts. Clarostats tho.
http://www.surplussales.com/Potentiometers/PBM-Shafted/PBM-Shafted-2.html
John
The original input transformer is huge. What is that? I saw them several times.
http://www.surplussales.com/Potentiometers/PBM-Shafted/PBM-Shafted-2.html
John
The original input transformer is huge. What is that? I saw them several times.
dmp
Well-known member
tomas1808
Well-known member
Thanks for the diagram and for the audio samples, dmp
Now, super newbie question:
What is the practical difference between the Input level pot, the pad, and the gain switch? Dont they all serve the same purpose? Does any of these controls the output volume?
Thanks!
Now, super newbie question:
What is the practical difference between the Input level pot, the pad, and the gain switch? Dont they all serve the same purpose? Does any of these controls the output volume?
Thanks!
Stagefright13
Well-known member
I'll post a BOM as soon as the boards arrive. I wanna make sure it all works well. And as far as my friend with the 1108 said I may want to add an output pad. Not a T pad but a 2 position fixed resistor pad. And I am using the vactrols etc.
And the input transformer is a huge question. I only have 1 02. Which is slated for my other project. So not sure what I will eventually use on this.
I got the vactrols from www.mammothelectronics.com and the 300 ohm pot From my above post. Everything else is on Mouser. Except the .0047 Wima film cap which they are always out of stock on. But I have a bunch of those already. I bought a bunch when they actually had some lol...
Anything that controls the input level will affect the output gain Tomas! LOL
John
And the input transformer is a huge question. I only have 1 02. Which is slated for my other project. So not sure what I will eventually use on this.
I got the vactrols from www.mammothelectronics.com and the 300 ohm pot From my above post. Everything else is on Mouser. Except the .0047 Wima film cap which they are always out of stock on. But I have a bunch of those already. I bought a bunch when they actually had some lol...
Anything that controls the input level will affect the output gain Tomas! LOL
John
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