Any opinions on taking an existing vintage -- Dynaco ST35 vs Scott 299 as a starting point for restoration?
Plenty of ideas, as always.
First, you determine, if the old rusty piece gets your excited to work on and have?
Each time I see one on e-B I justify it as No Go. If I find one for $200 or less in terms of the chassis is still shiny otherwise. ..
But they all sell for at least $400. .. being a raw deal. Those for $200 or less usually come as a piece of garbage.
Second, that design of such the old piece turned it into a lame idea anyways. The 40-50 yrs old PCB will prone to leakage with 50% chances, if not someone has already "tried to fix it". Do you need a such?
An acceptable one aka "above just good condition" will cost you at least $800, khe-m, then what's the point of "restoring" it?
Third, with spending $300-400 you could just go to their web site and order a brand new shiny chassis and the trafos, and do the rest by yourself. I would cover that ugly square cut with a copper plate - would look superb, and do point-to-point underneath.
but,
then WTH they are not producing the blank chassis with just the cuts for output tubes and around? Those huge holes on front surface look double-lame in 2017.
I would buy two of blanks, maybe three, right away, as that would really suit my DIY-er needs. But they seem stuck to it forever so again No Go to me. ..
First, you determine, if the old rusty piece gets your excited to work on and have?
Each time I see one on e-B I justify it as No Go. If I find one for $200 or less in terms of the chassis is still shiny otherwise. ..
But they all sell for at least $400. .. being a raw deal. Those for $200 or less usually come as a piece of garbage.
Second, that design of such the old piece turned it into a lame idea anyways. The 40-50 yrs old PCB will prone to leakage with 50% chances, if not someone has already "tried to fix it". Do you need a such?
An acceptable one aka "above just good condition" will cost you at least $800, khe-m, then what's the point of "restoring" it?
Third, with spending $300-400 you could just go to their web site and order a brand new shiny chassis and the trafos, and do the rest by yourself. I would cover that ugly square cut with a copper plate - would look superb, and do point-to-point underneath.
but,
then WTH they are not producing the blank chassis with just the cuts for output tubes and around? Those huge holes on front surface look double-lame in 2017.
I would buy two of blanks, maybe three, right away, as that would really suit my DIY-er needs. But they seem stuck to it forever so again No Go to me. ..
It's a matter of personal taste and preferences. I'd prefer the Dynaco because the Scott has a rather complex frontend with filters and stuff. Not my piece of cake. And I think the Dynaco looks better.
But why restore an old amp instead of building a new one? There have been some advances during the past few decades. Those newfangled sand devices are useful to get the best out of the tubes. New iron can be very good, too.
I purchased some original Dynaco ST-35 Z565 transformers, to get the ball rolling.
So my options are:
Baby Huey
Broskie EL-84
Triode Electronics
Dynakit ST35
Red Light District
Tubelab SPP
any designs to add to the list of EL84 pp with Z565 transformers?
So my options are:
Baby Huey
Broskie EL-84
Triode Electronics
Dynakit ST35
Red Light District
Tubelab SPP
any designs to add to the list of EL84 pp with Z565 transformers?
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The Dyna Z565, original or "clone", is a price performance champion. 
The Z565 is the "Gold Standard" in O/P "iron" for "El Cheapo" builders. It's more than good enough to warrant construction with triode/UL mode switches. The only thing that must change in an "El Cheapo" built with EL84, instead of 6V6 family, "finals" is the O/P tube R/C bias network. Contact Jim McShane for the appropriate values and some parts.
The Z565 is the "Gold Standard" in O/P "iron" for "El Cheapo" builders. It's more than good enough to warrant construction with triode/UL mode switches. The only thing that must change in an "El Cheapo" built with EL84, instead of 6V6 family, "finals" is the O/P tube R/C bias network. Contact Jim McShane for the appropriate values and some parts.
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The Dyna Z565, original or "clone", is a price performance champion.
The Z565 is the "Gold Standard" in O/P "iron" for "El Cheapo" builders. It's more than good enough to warrant construction with triode/UL mode switches. The only thing that must change in an "El Cheapo" built with EL84, instead of 6V6 family, "finals" is the O/P tube R/C bias network. Contact Jim McShane for the appropriate values and some parts.
I am new to tubes but I try to learn as much as possible.
How does that phase splitter work?
Will it work without the feedback loop from the OT?
The only way the input signal can change level at the grid on 2nd 1/2 input tube is via the OT?
The Valve Wizard -Long Tail Pair
The Valve Wizard
Have you noticed that the cathodes of tube halves are connected together ?
This is the way how the signal from 1st halve goes to 2nd halve.
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I see......what confuses me in the "El Cheapo" is that we have a ground connection between the 100k input resistor and the 1k resistor to the grid of the other input. But I will have to think more about that......
Assume there is not any feedback used, since it may confuse.
Without nfb the grid of 2nd halve is connected (via 1k) to ground, as it should.
And the signal goes from cathode of 1st halve to cathode of 2nd halve, forming a signal voltage between the grid and cathode of 2nd halve.
Without nfb the grid of 2nd halve is connected (via 1k) to ground, as it should.
And the signal goes from cathode of 1st halve to cathode of 2nd halve, forming a signal voltage between the grid and cathode of 2nd halve.
Thank you for the explanation.....it is via the cathodes it happens.....
Then I learned a bit more today.
Then I learned a bit more today.
That circuit is also called differential amplifier. Here is some more info:
Differential Amplifier
and here
Atma-Sphere music systems, inc.
Differential Amplifier
and here
Atma-Sphere music systems, inc.
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