1073 Preamp.

[b2]

Hi,

I've been working on Nevish preamp (1290,1073) for several month,and I've just finish my first 1073!

After lot's of investigation on this subject....I've build some 1290 who work fine pretty fine.I'm using 3 deck stage on BA189+BA283 with 2n3055 on end.The Input Tx is Sowter 9145 (Take care about the "ringing",see the very goods notes on JLM AUDIO website).The output Tx is 8751 Sowter.

After adjusting the bias on 2n3055,(Equal clipping on sinus wave,very important!)I've done measurements/

20Hz to 40Khz +- 1dBu with little climbing from 22K to 40K.

Square Wave Very nice on all the bandwith.

Gain Deck/By step of 5 or 4.5dBu (12 position,3 Decks)) Gain Max=74dBu.

On my 1073 Eq I've made some Mods/

On the Shelving card BA205,there's two caps 22nf between the 620R and th High Shelving Pots ,I've not using them because they made Probs on my card .

More, the caps of 15nF,between the cursor of this pots (HighShelving)and the 12K resistors can be removed,I've replace it with rotary switch and others caps ,as so you can have others HighShelving Frequencies possibilities not only the 10Khz on the 1073.



On the Presence Card BA211 my inductors are Sowter(T1530 and T1280) so if you take the original schemo, you have only 6 Frequencies (0.36/0.7/1.6/3.2/5.2/7.2/).But thoses can be increase on mine I've got 11 Frequencies this can possible by adjusting the caps (including Xl,Xc and F=1/6.28sqr(L.C).I've calcule the values of each caps but there's was a difference when I've measured eachs frequencies so I decided to adjust eachs caps for eachs Frequencies by measurements with this Sowter Inductor!

250Hz-330nf 2H
290Hz-220nf 2H
300Hz-180nf 2H
340Hz-150nF 2H
410Hz-122nf 2H
520Hz-100nf 2H


520Hz-150nf 1.1H
630Hz-100nf 1.1H
700Hz-80nf 1.1H
720Hz-68nf 1.1H
890Hz-47nf 1.1H
1.1K-33nf 1.1H

1.2K-68nf 0.45H
1.5K-47nf 0.45H
1.8K-33nf 0.45H
2K-22nf 0.45H
2.8K-15nf 0.45H
3.2K-10nf 0.45H

2K45-22nf 0.2H
3K2-12.2nf 0.2H
4K-6.8nf 0.2H
5K1-4.7nf 0.2H
5K6-3.7nf 0.2H
6K8-2.42nf 0.2H
7k6-2.2nf 0.2H
8K6-1.5nf 0.2H
9K8- 1.2nf 0.2H
11K7-750pF 0.2H
15K-360pF 0.2H
19K2-220pF

all at +18dBu of Gain on the Peak.


And I'm using BC109C ,BC107C transistors instead of BC184L.

Well that's all for this night, I hope this will help some.

I will like to thank thoses EXCELENTS websites GYRAF AUDIO,Dan Alexander,John Klett ,JLM audio,Bob Rowlette,.....and many others and all of the DIY community for the very goods work done.


"Le partage de l'information est l'essence meme de la creation".

Best regards.

Merci.

B2.

 

[rascalseven]

Congratulations!

Any pics you can share with the group?

:green:

JC

 

[quadwould]

Yes Congrats!!!


any pics


would love to see your pcbs

 

[neriks]

Howdy,

[quote author="b2"]I've been working on Nevish preamp (1290,1073) for several month,and I've just finish my first 1073![/quote]
Congratulations! :thumb:

I've also just recently finished a 1073! :grin: The 1073 I recently built is however only a prototype since I needed to verify the PCB-design before I proceed with the task of building 10 preamps based on the 1073 circuitry.

[quote author="b2"]And I'm using BC109C ,BC107C transistors instead of BC184L.[/quote]
Interessting! I'm using BC550C since I have tons of them in my lab! :wink:

Regards
Niklas

 

[tony dB]

B2, pictures please! Pron rules!!! :green:

 

[b2]

[quote author="neriks"]Howdy,

[quote author="b2"]I've been working on Nevish preamp (1290,1073) for several month,and I've just finish my first 1073![/quote]
Congratulations! :thumb:

I've also just recently finished a 1073! :grin: The 1073 I recently built is however only a prototype since I needed to verify the PCB-design before I proceed with the task of building 10 preamps based on the 1073 circuitry.

[quote author="b2"]And I'm using BC109C ,BC107C transistors instead of BC184L.[/quote]
Interessting! I'm using BC550C since I have tons of them in my lab! :wink:

Regards
Niklas[/quote]


Hi,

Well,I will send images,pictures when as soon as possible.But for this times I redraw the pcb to (1290preamp+1073Eq board) ,to finish.

Well as I said it's very important to bias the 2n3055 correctly,cause it'works in classA.

And it' important to verified by measurements the frequencies choices about the BA211 (Presence Card )In my case ,Ihave a difference between the calculs and the reality (I've done corrections on caps.

For me it's interesting to use BC109C and BC107C cause I have some,I tried with BC549C But when I check the HFE it was not nice (for the first transistors on BA189)so I prefer using BC190C(the prices it's not the same.For the 3 deck gain stage ,I'm using NSF RW 25 ones (at Radiospares),very good and so easy to build.


so,good luck for your 1073.

and if you need some informations,no probs.

A bientot.

bruno.

 

[b2]

[quote author="neriks"]Howdy,

[quote author="b2"]I've been working on Nevish preamp (1290,1073) for several month,and I've just finish my first 1073![/quote]
Congratulations! :thumb:

I've also just recently finished a 1073! :grin: The 1073 I recently built is however only a prototype since I needed to verify the PCB-design before I proceed with the task of building 10 preamps based on the 1073 circuitry.

[quote author="b2"]And I'm using BC109C ,BC107C transistors instead of BC184L.[/quote]
Interessting! I'm using BC550C since I have tons of them in my lab! :wink:

Regards
Niklas[/quote]


Hi,

Well,I will send images,pictures when as soon as possible.But for this times I redraw the pcb to (1290preamp+1073Eq board) ,to finish.

Well as I said it's very important to bias the 2n3055 correctly,cause it'works in classA.

And it' important to verified by measurements the frequencies choices about the BA211 (Presence Card )In my case ,Ihave a difference between the calculs and the reality (I've done corrections on caps.

For me it's interesting to use BC109C and BC107C cause I have some,I tried with BC549C But when I check the HFE it was not nice (for the first transistors on BA189)so I prefer using BC190C(the prices it's not the same.For the 3 deck gain stage ,I'm using NSF RW 25 ones (at Radiospares),very good and so easy to build.


so,good luck for your 1073.

and if you need some informations,no probs.

A bientot.

bruno.

 

[strombort]

that is very good of you.
you have done a good job for you.