Trident a range pre

[tanov]

Ideas about the output resistance of the mic preamp stage?
I wonder if it is ok to load it with 10 kOhms.

 

[bovox]

Hey, 10kohm -no problem. If you look in the ReVox Tape Machine A77 where the circuit is borrowed from.
Its loaded with 5kohm pot. The interesting part of the Trident and Cadac  amps is that it comes from this Tape Machine.....
When I was in Sweet Silence studios in Copenhagen they where convincing me that most of the sound came
from saturating the input transformer, of the Trident A.
There is what I believe most of the Brit. sound. is coming from.
Cheers Bo

 

[haima]

Wow, it's pretty much exactly the same circuit isn't it! I never realised that! Very interesting.

(attached the schem for the A77)

 

[bovox]

Hey, I used it for my self back in 76 in an 16 channel mixer,thats why it looked so familier.
It cant drive any transformer load. Put a nice transformer ahead and a 1646 after it and you get a nice pre.
But thats not the issue...
Cheers Bo

 

[tanov]

Hum, in this circuit the collector resistor of Q1 is 6.8k instead of 8.2k
The final preamp stage is classic schematic from audio electronics books - a common emitter amplifier with a controlled dynamic load (cascode). The dynamic load also acts as a common collector (emitter follower) amp, so it amplifies the current. In this case 5k load will not be a problem.

 

[user 10827]

up and running! working spot on. now to box her up and some listening tests are in order.

once we are happy with the sound we will be releasing boards, very soon.

best
Pete

 

[dolo72]

If you need to compare it to an original trident I've got a trident b range channel strip I can lend you for testing. I don't live that far from you so PM me if interested. Glad you got the tant's in there I've found they make a big difference.  ;D

 

[user 10827]

Hey Dolo

Great Idea, that would be awesome!

Ill PM you.

Best
Pete

 

[kpearsall]

Best news I've heard all day. Can't wait!

 

[pablobolche]

Great to hear. Intrested in 2 boards. Hope listening tests go smooth.

 

[tanov]

I finished the 2U 19" case and power. 8ch preamps are working well. I measured static transistor voltages and amplification by using sine waves. I can share some values:

Vin=26V (no voltage regulator, just preamp)
Q1Ve=9.9V
Q1Vb=8.61V
Q1Vc=1.13V

Q2Ve=13.1V
Q2Vb=13.7V
Q2Vc=25V

Q3Ve=0.48V
Q3Vb=1.13V
Q3Vc=11.62V

With one voltage regulator to 30V, I measured current consumption of I=9mA per channel.

BTW any ideas on phantom power, padding and high-pass filtering circuits? Because of the high voltage I think the pad can be omitted and a trim pot can be added to match the output level to the ADC.

 

[leadbreath]

hey pete, any news??????

 

[user 10827]

yes !  we are using it right now!!! ha ha sounds superb!

SO, what to do, I need to work out the final details, post all the details of how its made and how it works on our WWW, work out how many to make, how to post them to you, how much it will cost, that sort of thing,

Also I have the MIC PSU box thing kicking off next week, i dont want to do too much at once, need to get it all right and do a proper job...

so we are very very close...

 

[user 10827]

Just a small update -

We sent our pcb design to be made today, there will be 100 boards available.

Ill be posting a new, separate from my GMA ad, a new White Market ad very soon with all the details. Please post in that for interest, not here.

I have to say we have been using it in the studio with, sm58, octiva318, pelusoP12, akg414, Neumann fetU47, and it sounds wonderful, full sound and very clean...I love it...

We will post the recordings from each mic in the WM ad when that comes online in the next few days...

Pete

 

[tanov]

I can provide kits with original BCs in USA and Bulgaria.

 

[user 10827]

Hi tanov, that is great. I'm sure people will take you up on this.

I also forgot to say, (always in a rush!!)

That Bryan over in the WM,  DIY PARTS SUPPLY www.diypartssupply.com will be providing, complete parts kits for Project. Although with respect to the transistors, I have speced 550/560.

Best
Pete

 

[Jim50hertz]

Any sonic advantage in using originals rather than 550/60s?

Nice one Pete, how exciting!

 

[tanov]

The sonic difference will come from overdriving the output transformer. I compared it to my yamaha n-12 mixer and there are very subtle differences in the low end.

Pete,
Did you compare the sound to an original unit?

 

[abechap024]

Any sonic advantage in using originals rather than 550/60s?

Nice one Pete, how exciting!

The sonic difference will come from overdriving the output transformer. I compared it to my yamaha n-12 mixer and there are very subtle differences in the low end.

Pete,
Did you compare the sound to an original unit?

??? I think he is talking about using the spec'ed bc550/60 verses the original transistors. I could be missing something here but that will In no way necessarily change how hard the output transformer is driven. One probable sonic advantage of using the spec'ed 550/60 is they will probably be lower noise, cheep as chicken feathers and you don't need to worry about if the originals have the correct footprint for the PCBs. But compared to your Yamaha I'm not surprise that there is a difference in the low end. Don't you love transformers?

 

[tanov]

My point was that the transformers are the sonic elements here. My schematics are with originals, but not 550s and I did not try with 550 to see if there is a difference. Again the 3daudio drums sound fantastic with this trident, but the recording is distorted. It does not seem to be ADC clipping, but very strange analog distortion. I can post an image of the waveform. Because there is no output transformer in the original, I suppose it can be the final stage with high input from the first one. About the yamaha - it is with superb discrete pres. Only the transformers are missing. Even the noise is 1.5dB less than trident. Btw I saw your dbx160vu schematic and maybe I will do it.

3daudio inc sample with original trident module. The samples are recorded in different sessions, so they are not identical: