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Lundahl transformers.

PostPosted: Sun Nov 09, 2008 12:26 pm
by jammy jamz
has anyone ever ordered these from germany? are they super expensive to have shipped? do you like them, or are they over-hyped?

and, how "hard" is it to modify a unit by replacing a transformer? any tips or warnings would be appreciated.

:?:

PostPosted: Sun Nov 09, 2008 4:30 pm
by Alain Benoit
Lundahl's are good transformers. You dont have to order them from the Fatherland as there are distributors in North America. Not to mention dealers right here in Canada.

You may also want to look at Jensen, Sowter and our own Canadian Hammond.

As far as implementation make sure you have the proper specifications for your application and adhere to all the original circuit parameters including but not limited to pinouts.

PostPosted: Sun Nov 09, 2008 10:13 pm
by jammy jamz
have you ever used them to do a mod on a ribbon mic?

and, do you think its worth it to mod the mic, or save the money to put towards a nice pre?

what would the mod do, make them more sensitive, or quieter, or both?

i was looking at the cascade mics, and they offer the same mics with the lundahls in them, and they are almost 400 dollars more expensive. is it worth that much, do you think?

and

should i be paying you for your expertise in the electrical realm? 8-)

PostPosted: Sun Nov 09, 2008 10:28 pm
by Alain Benoit
jammy jamz wrote:have you ever used them to do a mod on a ribbon mic?


Never had a reason to.

jammy jamz wrote:and, do you think its worth it to mod the mic, or save the money to put towards a nice pre?


Depends if you have a reason to.

jammy jamz wrote:what would the mod do, make them more sensitive, or quieter, or both?


This totally depends on the circuit dynamics avec and sans said transformer replacement.

jammy jamz wrote:i was looking at the cascade mics, and they offer the same mics with the lundahls in them, and they are almost 400 dollars more expensive. is it worth that much, do you think?


I would be hard pressed to spend $400 on a Cascade mic personnally.
I am also wondering which Lundahl mic output transformer would cost $400.

PostPosted: Mon Nov 10, 2008 9:32 am
by jammy jamz
the $400 cascade option was for a stereo set of the vin-jet line. the long (2") single ribbons. so it was actually two mods, with two transformers for the four bones.

i have a set of trion 7000 dual short ribbons, and they are surprisingly nice. i just wanted to try it, because, like mt. everest, its there, and i can.

i thought that mabey you did something like that just out of personal interest.

have you ever modded any of your gear, because you wanted to, or had to?

PostPosted: Mon Nov 10, 2008 9:49 am
by Alain Benoit
I'd venture to say that nearly a third of my gear has been modded in one form or another even if it was as minor as beefing up a power supply.

PostPosted: Mon Nov 10, 2008 12:54 pm
by jammy jamz
cool.

what would you consider to have been your most complicated mod? and can you tell me what unforseen complications, if any, you experienced? i ask that question, because, i know you well enough to know that you would do all the schematic studying you would have had to do. was there any pleasant, or not so pleasant surprises, that research didnt make obvious or available to you?

and

do you mail order your parts, or, can you aquire everything needed from munroe's....

and, if you mail order, whre are you suppliers, or do you do it thru the wonderful world of munroe's again, or is that a trade secret? :shock:

sorry for picking your brain, but, i have an idea of how smart you are. thats not a kiss ass. honest injun.

thanks for the info.

PostPosted: Mon Nov 10, 2008 1:08 pm
by Alain Benoit
One of the most complex mods I've done was to an ART "Tube MP" preamp.
There are hardly no original parts left inside except for four jacks, two pots, three switches and an LED.
It is now a completely different preamp altogether, super fast, super super fast.
This mod was definitely not for the faint of heart, the replacement opamps were so unstable that socketing them would have likely sent them into oscillation due to the added capacitance.
After changing the regulator to a 7812 to reduce the filament starvation the project was finished. Without even double checking my work I reasembled the chassis, plugged it in and it worked perfect. Next step was to burn it in for 24 hours.
When I get a chance I will A/B it with another stock one I have likely using an AT 4051 on an acoustic guitar and a snare.

I photo-document all my work and may post pictures later.

PostPosted: Mon Nov 10, 2008 3:07 pm
by jammy jamz
well, i look forward to the a/b comparison, cuz as chance would have it, i have one of those cute little mp's....and am thinkin of pickin up another offa ebay....cuz, they are cheap, functional, and reliable, so far.

:-D

PostPosted: Tue Nov 11, 2008 2:36 am
by Alain Benoit
Here are a few detailed pictures of the bypass caps added to the Vin of both replacement opamps. These were a tantalum and polyester in parallel.
Image

Image

Image

Image

Image

Image

The last image is of all the removed original components.


Image

PostPosted: Tue Nov 11, 2008 3:03 pm
by jammy jamz
whoa al, thanks for those. i had no idea that the inside of that little box would be so busy.

ribbons and evrything. you've inspired me to go take mine apart right now.

beautiful clean work too. 8-)

PostPosted: Tue Nov 11, 2008 3:13 pm
by jammy jamz
whoa, i was just admiring the pictures,

and whats the deal with the red square, and yellow round one being married together like that.. thats cool.

PostPosted: Tue Nov 11, 2008 3:38 pm
by Alain Benoit
jammy jamz wrote:whoa, i was just admiring the pictures,

and whats the deal with the red square, and yellow round one being married together like that.. thats cool.


Alain benoit wrote:Here are a few detailed pictures of the bypass caps added to the Vin of both replacement opamps. These were a tantalum and polyester in parallel.

PostPosted: Wed Nov 12, 2008 12:58 pm
by jammy jamz
thats neat-o.

i didnt know that you could marry components like that. by making them connect, i assume that the electrical current that is passing through the circut board is being filtered by those two pieces acting as one?

why you would choose to connect the two specific pieces like that?

:?:

PostPosted: Wed Nov 12, 2008 1:01 pm
by jammy jamz
another question

could you ballpark the figure of the cost of all the pieces you needed to perform the "operation"?

PostPosted: Wed Nov 12, 2008 1:36 pm
by Alain Benoit
jammy jamz wrote:thats neat-o.

i didnt know that you could marry components like that. by making them connect, i assume that the electrical current that is passing through the circut board is being filtered by those two pieces acting as one?

why you would choose to connect the two specific pieces like that?

:?:


First you need to kinda understand why a bypass cap is being added in this position.
Capacitors basically by nature block DC and pass AC.
Any transient in the supply voltage is absorbed by the capacitor arrangement and shed to ground potential. Because they block DC no short is created between Vin and ground.
It is a standard practice to have a bypass cap across the supply pins of any sensitive IC or any signal carrying opamp. They are placed as close as possible to the device with pins as short as possible.
The specific arrangement was to take advantage of the different characteristics of each type of capacitor. Dont forget that tanalums are polarized and polarity must be respected.

PostPosted: Wed Nov 12, 2008 1:40 pm
by Alain Benoit
jammy jamz wrote:another question

could you ballpark the figure of the cost of all the pieces you needed to perform the "operation"?


Assuming a fairly off the shelf tube definitely under a hundred. Keeping in mind that it usually makes more sense to order a higher count then neccessary to meet price breaks.

PostPosted: Thu Nov 13, 2008 9:43 am
by jammy jamz
thanks al.

you've given me quite a bit to think about, in those five lines of information. honestly, it kinda blew my mind. i have taken rudementary electronics with this computer course, and understand (somewhat) the properties of electricity as it goes through devices.

one more question.

on a scale of 1 - 10, - 1 being not good, 10 being awesome - how do you rate the ART mp, now that you have modded it. was it worth it? and most interesting (to me at least)

do you still reach for the ART, even though you have that rack of dakings, focusrites, and avalons?

thanks again for taking the time with the photos and info....man, super effing cool.

:-D

PostPosted: Thu Nov 13, 2008 8:49 pm
by Alain Benoit
Have'nt auditioned it yet waiting for opportunity.

It was worth it cause I dont charge myself for labour and even if it did not end up sounding killer I find great satisfaction in pulling off projects of this type.

PostPosted: Thu Nov 13, 2008 9:19 pm
by Alain Benoit
Well a prelim test showed that switching from the stock one to the moded one with matched gains gave this result; from hideously noisy to "Is it on?"

PostPosted: Fri Nov 14, 2008 8:23 am
by macrae11
Any chance of posting some samples?

PostPosted: Fri Nov 14, 2008 8:41 am
by Mathieu Benoit
I'll record some this weekend, maybe with an acoustic and a pair of 4050s or something...

PostPosted: Fri Nov 14, 2008 8:55 am
by Jef
Drumwaiter wrote:I'll record some this weekend, maybe with an acoustic and a pair of 4050s or something...


It would be interesting to hear a 'before & after' comparison.
Do you have another unmodified ART - Tube MP preamp for a
'shoot-out' type of comparison?

PostPosted: Fri Nov 14, 2008 9:11 am
by jammy jamz
i have one that i would donate to the cause.

:-D

if you want me to al, mail me you phone # to

jamz1970@hotmail.com

and, you can keep it for a week or so....to try it on a bunch of different applications.

PostPosted: Fri Nov 14, 2008 9:12 am
by Mathieu Benoit
Jef wrote:
Drumwaiter wrote:I'll record some this weekend, maybe with an acoustic and a pair of 4050s or something...


It would be interesting to hear a 'before & after' comparison.
Do you have another unmodified ART - Tube MP preamp for a
'shoot-out' type of comparison?


Yes, which is why I'd record a pair of 4050s to the same source, one will be the control the other will be the mod.