Ok, assuming now that interstage trans has no listening objections,... What might be the problem with a step up interstage?
Any trans gurus here? pls..
Basically that square output you get is from phase shift? At what freq does it starts to become squarish? Any better design you can come up with? Come on, Im gonna make you a famous man!!
p/s- as far as this forum is concern, dont call me colin pls.
Thanks for the compliment. However, Im pretty sure I am not the first to come up with this idea.. (scott is one.. hahaha!)
Nice idea but i think it got a bit off your hands when you decided to implement a transformer...
Have you thought about taking the negative feedback for opamp after the valve stage - a design similar to some opamp driven power amplifiers?
By the way, in my opinion this is one of the freshest threads in here for weeks. Don´t let the people get you down.
Teemu K
Have you thought about taking the negative feedback for opamp after the valve stage - a design similar to some opamp driven power amplifiers?
By the way, in my opinion this is one of the freshest threads in here for weeks. Don´t let the people get you down.
Teemu K
skyraider said:
It looks like the Lundahl LL1674 would be a $100 upgrade to the $7.50 EDCOR interstage as well as being designed as a stepup. The AD815 was designed as ADSL line driver (very low distortion up to over 1MHz and 100 Ohm drive). It handles the 150 Ohm input fine. The output stage (of the overall amp) is open loop BTW.
Any opinions on the Lundahl, anyone?
My $0.02:
I think you are getting a bit fixated on the OPA627 and using a whole high $$$ transformer as the glue is a bit off, IMHO.
Here's another idea (nobody laugh!) how about a power opamp deeply biased into class A driving that tube? I guarantee nobody else on the block will have one.....
I think you are getting a bit fixated on the OPA627 and using a whole high $$$ transformer as the glue is a bit off, IMHO.
Here's another idea (nobody laugh!) how about a power opamp deeply biased into class A driving that tube? I guarantee nobody else on the block will have one.....
Op-Amps and tubes
I been reading this thread and mostly agree that this seems like a more work than alternative solutions or a solution looking for a problem.
I am surprised that no one has mentioned a reasonable use of op-amps in a tube design; that of using them to automatically set and maintain the output tube bias. No this isn't a new idea but it is a good one and the sonic qualities of the op-amp are of little relevance.
I mention this because except for exotic op-amps they are generally regarded as being pretty much polar opposites of what tube sound is all about. I read an article some years back that proposed that what we all like about "tube sound" is actually "transfomer sound" Interesting that Scott now seems to want to mix all possible sonic signatures in his design. Whee.
The problem is that there is sufficient complexity to all this that it will be most dificult to determine if the design has a signature sound or if one of the many interactions was poorly understood and that ends up poluting the end result.
Still if you have the time and money - go for it . remember they told Columbus that pastuerizing milk couldn't possibly work
I been reading this thread and mostly agree that this seems like a more work than alternative solutions or a solution looking for a problem.
I am surprised that no one has mentioned a reasonable use of op-amps in a tube design; that of using them to automatically set and maintain the output tube bias. No this isn't a new idea but it is a good one and the sonic qualities of the op-amp are of little relevance.
I mention this because except for exotic op-amps they are generally regarded as being pretty much polar opposites of what tube sound is all about. I read an article some years back that proposed that what we all like about "tube sound" is actually "transfomer sound" Interesting that Scott now seems to want to mix all possible sonic signatures in his design. Whee.
The problem is that there is sufficient complexity to all this that it will be most dificult to determine if the design has a signature sound or if one of the many interactions was poorly understood and that ends up poluting the end result.
Still if you have the time and money - go for it . remember they told Columbus that pastuerizing milk couldn't possibly work
scott wurcer said:
No thanks, I've got plenty of opamps to try.
If driving tubes with opamp is the task, then there is hardly a better tube than Siemens power tetrode F2a . One could build a pushpull amplifier with those tubes and an opamp even without stepup transformer. The F2a is very rare and pricey but maybe it's worth it. Our member moamps has some for sale on ebay.
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