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Re: Slow Blow pre?
« Reply #280 on: April 17, 2016, 04:15:11 PM »
I figured they would both work! I just can't help but toy with designs.

Ha! Choke makes no difference. It's probably not that cheap either.


Re: Slow Blow pre?
« Reply #281 on: September 13, 2019, 02:32:02 PM »
I have never built a mic preamp,  but have built a guitar tube amplifier and several transistor Projects.  I first thought about building the gyraf G9 preamp. Then I found this thread about the slow blow mic preamp. I have read all the replies in this thread but I still have some questions.

The suggested slow blow preamp 5687 srpp output stage has no output transformer.  Schematic below
https://www.qsl.net/sv3eao/preamp.jpg

According to this article http://www.valvewizard.co.uk/SRPP_Blencowe.pdf by Merlin Blencow. The Srpp stage likes a certain load impedance to perform optimal.
Will the slow blow preamp work with both 600R inputs as well as 10k line inputs?

Will a e182cc give the same performance as a 5687 in this configuration? e182cc has slightly higher mu and transconductance, rp is almost equal.

I have a couple of ecc33 tubes and 12sn7gt so it would be interesting to use these for the first stage/stages. 

moamps

Re: Slow Blow pre?
« Reply #282 on: September 15, 2019, 05:05:17 AM »
Welcome to GDIY!
....The suggested slow blow preamp 5687 srpp output stage has no output transformer.  Schematic below
https://www.qsl.net/sv3eao/preamp.jpg
According to this article http://www.valvewizard.co.uk/SRPP_Blencowe.pdf by Merlin Blencow. The Srpp stage likes a certain load impedance to perform optimal.
Will the slow blow preamp work with both 600R inputs as well as 10k line inputs?
Yes, IMO. But if you are in doubt, you can design it for 600 ohms according  to MB article and use the switch with dummy 600 ohm resistor load on the output which will be engaged when the load is 10k or so.
Quote
Will a e182cc give the same performance as a 5687 in this configuration? e182cc has slightly higher mu and transconductance, rp is almost equal.
Yes.


 

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