Valve Line Out for Spring reverb

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Seabstudio

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Jul 6, 2012
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33
Hi everyone !
I search a advice about a good tube line driver . I already build a good spring reverb but i have difficulty with this last stage .The driver stage for spring  is good and drive hard the springs ( I hear them rattle often :)) With a lighbulb 150mA I can see the filament get red on certain source , so that part of circuity work fine

My soundcraft serie 600 ( desk from mid 80's ) have 10K input. After recovery reverb stage on the reverb, I try Gyraf SRPP with 12AU7 and transformer 2:1 ...i need to push hard my line input on mixing desk , maybe more than 3/4 , it s not normal . IF I change secondary wiring on 2:1 transformer and use the two 150ohms winding in parallele instead of serie , the gain goes up but sound change a lot ( more "harsh", less warm and react strange on bass ) , I try ECC88 , it s little more gain , no big difference

Because I m motivated :)  I try a LA2A stage with 12BH7 and Carnill 15K:600 ....same problem,  it s very low level too ( but sound really good )
I don t know if it s the impedance mismatch / 600ohms things , and that my question too .
Do you recommend a specific line out circuit to match my "modern " mixing desk with 10K input instead of old 600ohms matched impedance.

Any helps greatly appreciated :)
Thanks in advance Seb
Sorry for my english

 
 

Tubetec

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Joined
Nov 18, 2015
Messages
3,288
Depends to some degree on the tank recovery transducer impedence , just as a test try an active DI box(1 meg or more input z)  with a very short patch cable . By keeping input z high and cable very short you'll get a bit more sparkle from the spring , see how it sounds to your ears .
If you like it consider a low noise cathode follower input with many meg ohms input z , mount the tube on the tank itself ,then feed your driver stage 12bh7 and transformer from that .
If you (low)load the output transducer of the tank its sounds 'sucky' , try the highest impedence output transducer you can find ie 10k into many megs of a cathode follower  , you have tons of drive ,now tons of level on pick up too
 

Seabstudio

Active member
Joined
Jul 6, 2012
Messages
33
Tubetec said:
Depends to some degree on the tank recovery transducer impedence , just as a test try an active DI box(1 meg or more input z)  with a very short patch cable . By keeping input z high and cable very short you'll get a bit more sparkle from the spring , see how it sounds to your ears .
If you like it consider a low noise cathode follower input with many meg ohms input z , mount the tube on the tank itself ,then feed your driver stage 12bh7 and transformer from that .
If you (low)load the output transducer of the tank its sounds 'sucky' , try the highest impedence output transducer you can find ie 10k into many megs of a cathode follower  , you have tons of drive ,now tons of level on pick up too

Many thanks for the reply
We already talk about spring reverb , lightbulb etc :) Precious info and knowledge appreciated !
Not sure to understand the part of cathode follower , where is it in circuit ?
 

Seabstudio

Active member
Joined
Jul 6, 2012
Messages
33
ruffrecords said:
You could try my Twin Line Amp design. This has up to 40dB gain (set by one resistor) and can easily drive +20dBu into a 600 ohm load via a 2:1 transformer. Check out the TwinLineAmp folder on the DIY page of my web site:

https://www.customtubeconsoles.com/diy

Cheers

Ian

Oh ! your Gdrive is awesome share .
Yes I will take a look for that design and test it
But I need to put the circuit after the recovery stage of my string reverb ?( It s alaready  a parallele 12AX7 with 220K plate and red led for cathode bias ) , then atone control ( same as 6G15 unit ) and a 250K pot before the SRPP stage
 

Tubetec

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Nov 18, 2015
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3,288
The cathode follower would be the first stage on the recovery side of the tank , youd still need to add gain and balancing afterwards.
 

Seabstudio

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Joined
Jul 6, 2012
Messages
33
Tubetec said:
The cathode follower would be the first stage on the recovery side of the tank , youd still need to add gain and balancing afterwards.

Like attached ?
So I put the gain after it ? For exemple I can use a 12DW7 to create a good recovery gain ?
Not sure to understand  :-\
Thanks
 

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