replacing transformer with chip preamp

[ADHD-Oarsmen]

I know there was a thread a few weeks ago referring to this but I wanna dig a little deeper.  So the most expensive part of a preamp (which is what I need to build) is the input transformer.  The good ones go for $50 to $100 and even higher but I don't really have that much money.  I need 8 preamp and the input transformers would take up all my funds that I have at the moment ($300 maybe more in a few weeks)even though i know that they are one of the biggest influences on the sound.

SOOOO... here's my question???

can I put a THAT or TI chip preamp (I think its a THAT 1510/1512 and TI217 that I'm thinking about) in place of the transformer on something like a MILA Tube pre or a API 312 for a little character. All a transformer does essentially is bump up the signal (and balance but I can wind a 1:1 balancing transformer no problem).  Right?

So I see no reason to why this wouldn't work.  Sure it wont give me a huge amount of color but it would still make it sound less sterile than just the chip amp on its own.

prove me wrong as I'm sure a few of you will. 

     

 

[sahib]

Yes this subject has been covered many times before.

But my main concern is your budget. You have $300 for 8 micpres = $37.50 per micpre. How are you going to manage that for say 312?  It is not enough even for GAR 2520 and EA output transformer from Jeff.

 

[ADHD-Oarsmen]

honestly my budget is actually bigger that that.  i would like to keep it somewhere around, oh, i don't know... maybe $60 each.  I have some old power transformers for the high voltage  and need to acquire low voltage ones.  I do a lot of broken electronics work and have a bunch of unused parts laying around and plan to build the 8 over the next 4 months.  If I made a 312 I would definitely be winding my own output because there pretty easy.  Also id be scratch building a 2520.  I like to fiddle with electronics if you haven't noticed. i don't need super high quality.  Just something to amp up the signal and give it character before going in my motu828.   

 

[sahib]

Then it won't be a 312 as what makes it 312 are the transformers and the opamp.

Yes, THAT has got a good application example in the data sheet but making a micamp in front of a micamp is quite a strange plan. You can certainly build the THAT device as the micpre stage and then use the others in line amp configuration. If this is what you want to do.

 

[ADHD-Oarsmen]

i totally realize this is an odd thing, but being normal isn't as fun. im more interested in a tube mic pre anyway because i want a little compression before it goes in the box. ill probably put a switch in between the chip and other stage to add flexibility. 

 

[Andy Peters]

. im more interested in a tube mic pre anyway because i want a little compression before it goes in the box.

Why should there be any compression in a tube stage?

-a

 

[Bill Wilson]

I design custom audio circuits for professional recording equipment; with over 50 yrs. in pro audio, console & recording studio design.

I have a few transformerless mike preamps left from my console building business. They have 4 discrete trasnsistors on the front end & the gain pot is connected between the emitters of the 2 pairs of dual transistors; it uses a 5k reverse taper pot.
The output is single ended but the extra IC can be configured as a balanced output if needed. The max gain of the pre approaches 75 dbv. The distortion is extremely low (somewhere in the 0.01% THD. region). The 6.8k phantom power resistors are on the card but you will have to add the on-off switch, an led & a cap. Likewise switching for polarity would need to be added. No pad is necessary on the front end as the circuit takes full line level of at least +10dbv w the gain turned down all the way.
Can let you have each preamp for $45.00. Will also supply circuit diagram of a good bipolar supply.

The one complication is I need to know by tomorrow if you want some pres. as I am having knee replacement surgery next monday in Gainesville, Fla. I will not be able to work at the bench for 3-4 weeks following surgery.
Bill Wilson