Yes Shoog I realize there are better designs out there, but I was working along the lines of the original post...
So what i've come up with:
-Sounds good!
-DIY not kit based.
-$250-$300 for tubes, transformers, and shipping for transformers. I'm willing to go to about $350 if its really worth it.
-Ignoring costs of resistors, most caps, jacks, wiring, volume attenuator, voltage regulation, chassis. After scouring stocks, begging and trading with friends, abusing samples programs, salvaging old projects, etc these costs will likely be very low.
-New production tubes, I may use NOS, but new production tubes must be available.
-Solid state rectified, though having read up on rectifier tubes I'm confident I can adapt a design intended for tube rectification to SS rectification
-I'm open to SE or PP, though SE seems to cost more.
-Not Monoblocks.
-Not so big that it can't sit ontop of a dresser, or corner of a desk.
-Relatively low power is fine.
-Stable, reliable, decent tube life.
-Potential for modification, experimentation.
-Performance/quality, and cost are the main priorities, although aesthetics are relevant to some extent, all things being relatively equal cool looking tubes get bonus points.
Most single ended designs I've looked at blow my budget, as does anything using 300b's, KT88's, etc. 45's seem to only be available NOS, so they are out too? Most/all NOS tubes blow my budget anyway.
So I am just basing on what I read...
Yes, PP is the way to go if you want more power, but the post just said that low power is fine.
Not kit based, well RH84 isn't.
It has a tube rectifier, but can be SS rectified.
Not a monoblock.
EL84 tubes even though being a smallish tube, do have a pretty long life, are readily available NOS or new production (tubestore.com has JJs for $12/pc and four other EL84s ranging $10 to $20/pc)
There is a potential for modification (or reuse parts in a different amp). There is a modification (I can't find it now though I think it was on the other diy type audio website) where a headphone jack was added to an RH84.
EL84 tubes are not bad looking (okay, not the coolest looking like the 6C33 or 807, but they are not that bad on the eyes).
Way cheaper than the $350 max (and since there is spare parts bin, use it and pick parts from it).
The RH84 will sit on a desk corner nicely (if you build it with a small enough chassis and not a hunk of metal you had left over from a Hammond organ).
The RH84 overall won't blow your budget.
I just think that if someone wants to learn how to read a simple schematic, they can solder tube sockets/wire/components, get a an excellent sounding tube amp on the very cheap, then this is one of the paths to go.
I could probably cobble together a working RH84 with most of the parts from my old Heathkit AA-191 and parts bin (Wow! Am I the only one with far too many resistors and capacitors?!? No wonder my wife gives me THAT look) and I am short a single EL84 tube (I could splurge and go for a matched pair) and a better output transformer (I do have one, but I'd rather go better on the output transformer for sound).
So what i've come up with:
-Sounds good!
-DIY not kit based.
-$250-$300 for tubes, transformers, and shipping for transformers. I'm willing to go to about $350 if its really worth it.
-Ignoring costs of resistors, most caps, jacks, wiring, volume attenuator, voltage regulation, chassis. After scouring stocks, begging and trading with friends, abusing samples programs, salvaging old projects, etc these costs will likely be very low.
-New production tubes, I may use NOS, but new production tubes must be available.
-Solid state rectified, though having read up on rectifier tubes I'm confident I can adapt a design intended for tube rectification to SS rectification
-I'm open to SE or PP, though SE seems to cost more.
-Not Monoblocks.
-Not so big that it can't sit ontop of a dresser, or corner of a desk.
-Relatively low power is fine.
-Stable, reliable, decent tube life.
-Potential for modification, experimentation.
-Performance/quality, and cost are the main priorities, although aesthetics are relevant to some extent, all things being relatively equal cool looking tubes get bonus points.
Most single ended designs I've looked at blow my budget, as does anything using 300b's, KT88's, etc. 45's seem to only be available NOS, so they are out too? Most/all NOS tubes blow my budget anyway.
So I am just basing on what I read...
Yes, PP is the way to go if you want more power, but the post just said that low power is fine.
Not kit based, well RH84 isn't.
It has a tube rectifier, but can be SS rectified.
Not a monoblock.
EL84 tubes even though being a smallish tube, do have a pretty long life, are readily available NOS or new production (tubestore.com has JJs for $12/pc and four other EL84s ranging $10 to $20/pc)
There is a potential for modification (or reuse parts in a different amp). There is a modification (I can't find it now though I think it was on the other diy type audio website) where a headphone jack was added to an RH84.
EL84 tubes are not bad looking (okay, not the coolest looking like the 6C33 or 807, but they are not that bad on the eyes).
Way cheaper than the $350 max (and since there is spare parts bin, use it and pick parts from it).
The RH84 will sit on a desk corner nicely (if you build it with a small enough chassis and not a hunk of metal you had left over from a Hammond organ).
The RH84 overall won't blow your budget.
I just think that if someone wants to learn how to read a simple schematic, they can solder tube sockets/wire/components, get a an excellent sounding tube amp on the very cheap, then this is one of the paths to go.
I could probably cobble together a working RH84 with most of the parts from my old Heathkit AA-191 and parts bin (Wow! Am I the only one with far too many resistors and capacitors?!? No wonder my wife gives me THAT look) and I am short a single EL84 tube (I could splurge and go for a matched pair) and a better output transformer (I do have one, but I'd rather go better on the output transformer for sound).
I still think that the Mighty Midget could be built for less.
The tube used is obscure but plentiful and cheap (cheaper than the equivilant EL84). It would be relatively easy to accumulate a lifetimes stock without breaking the bank.
The board is the only really expensive part - apart from the transformers. I guarantee without a shadow of a doubt that it is a better sounding amp. I would build it on perf board for next to nothing.
Shoog
The tube used is obscure but plentiful and cheap (cheaper than the equivilant EL84). It would be relatively easy to accumulate a lifetimes stock without breaking the bank.
The board is the only really expensive part - apart from the transformers. I guarantee without a shadow of a doubt that it is a better sounding amp. I would build it on perf board for next to nothing.
Shoog
Hi impedence input could be slightly rolled off and might be a bit noisier (think hiss/pop/fizzle).
Any power amp can be made an integrated if you just add an input pot to it - assuming it has an input sensitivity of 2V for full output.
Shoog
Commercial source components, like CDPs, adhere to the IHF "standard" of being able to drive a 10 KOhm I/P impedance. It is very highly unlikely that your opamp based sources will have problems working into a 50 KOhms and some of the tubed DIY items available have a 50 KOhm minimum requirement. So, that's the value I'd settle on. Go as low as you safely can.
Yes, high I/P impedances present an easy load to drive. The fly in the ointment is that high I/P impedances combine with the Miller capacitance of triode I/P stages to form a low pass filter that rolls high freq. info. off. Look again at those older designs. Many of them have a pentode I/P stage. CMiller is tiny in pentodes and the low pass filter problem is not present.
Looking at the original ST35 schematic on page 11 here: http://www.tnt-audio.com/ampli/dynaco_st35_manual.pdf
can someone explain to me the purpose of C6? It's a 18pf cap between the of the high mu cathode of the 7247 and grid 2 of the EL84/ the input of the OPT. Also seen here without cap number http://diyaudioprojects.com/Schematics/images/Dynaco-ST35-Tube-Amp-Schematic.png
can someone explain to me the purpose of C6? It's a 18pf cap between the of the high mu cathode of the 7247 and grid 2 of the EL84/ the input of the OPT. Also seen here without cap number http://diyaudioprojects.com/Schematics/images/Dynaco-ST35-Tube-Amp-Schematic.png
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