Hi folks!
Since I bought Altec Voice of Theatre A5 speakers, I’m trying to materealize my idea and change my 300b amp to something even more low power.
Would love to try 205d. Any ideas what circuit and OPT I should try / use?
What about recreating Yamamoto 205d amplifier?
Also, any impresions on how 205d sound vs 300b, and in general low powered amps sound is more than welcome
Since I bought Altec Voice of Theatre A5 speakers, I’m trying to materealize my idea and change my 300b amp to something even more low power.
Would love to try 205d. Any ideas what circuit and OPT I should try / use?
What about recreating Yamamoto 205d amplifier?
Also, any impresions on how 205d sound vs 300b, and in general low powered amps sound is more than welcome
The WE datasheet for the 205D (the old one) has a table of operating points. How much power are you aiming for?
If a damping factor around 2 is acceptable, the datasheet gives some operating points that will get you over 1W. You'll need to find (or have made) some small 8K-10K series feed OTs.
Question:
Does your next amplifier have to use a DHT output tube?
2A3, 6A3, 6B4G, are currently produced.
45 that are currently produced, are not really 45 tubes. some are close to a real 45, but they are expensive.
I have three 45 tubes if I decide to build a 45 amp again.
There are a few IDT (Indirect Heated Triode tubes).
Some are Vertical Output tubes for TV.
But I believe that NOS is all that is available.
I have a couple of amplifiers that I designed that use 6CK4 IDT.
That is why I purchased 6 or 8 the first time, and 6 the second time.
Does your next amplifier have to use a DHT output tube?
2A3, 6A3, 6B4G, are currently produced.
45 that are currently produced, are not really 45 tubes. some are close to a real 45, but they are expensive.
I have three 45 tubes if I decide to build a 45 amp again.
There are a few IDT (Indirect Heated Triode tubes).
Some are Vertical Output tubes for TV.
But I believe that NOS is all that is available.
I have a couple of amplifiers that I designed that use 6CK4 IDT.
That is why I purchased 6 or 8 the first time, and 6 the second time.
They are making new 205D tubes overseas.
2pcs Psvane WE205D(WE205D L) Vacuum Tubes Matched Pair Western Electric 205D Replica Version|vacuum tube|tube vacuumwestern electric tube - AliExpress
2pcs Psvane WE205D(WE205D L) Vacuum Tubes Matched Pair Western Electric 205D Replica Version|vacuum tube|tube vacuumwestern electric tube - AliExpress
Will wonders never cease?
Purchase 3 or more for stereo, 2 or more for mono; in case one is destroyed during power up testing . . .
You will have a $pare.
As to outstanding good looks, I think the best are some RF Transmitting tubes that are Directly Heated, with Thoriated Wolfram filaments
(Wolfram = Tungsten, but Wolfram sounds better).
Purchase 3 or more for stereo, 2 or more for mono; in case one is destroyed during power up testing . . .
You will have a $pare.
As to outstanding good looks, I think the best are some RF Transmitting tubes that are Directly Heated, with Thoriated Wolfram filaments
(Wolfram = Tungsten, but Wolfram sounds better).
Last edited:
Wow!
A 205D is a very expen$ive rectifier!
Other than for the look of a 205D used as a rectifier, I would $pend my money somewhere other than for 205D rectifier$.
And that choke from the B+ to the output transformer center tap . . .
Is it for filtering ripple?
Is it to act as a low pass filter to the music?
Is it for the field coil of the loudspeaker?
A 205D is a very expen$ive rectifier!
Other than for the look of a 205D used as a rectifier, I would $pend my money somewhere other than for 205D rectifier$.
And that choke from the B+ to the output transformer center tap . . .
Is it for filtering ripple?
Is it to act as a low pass filter to the music?
Is it for the field coil of the loudspeaker?
Last edited:
Its the second retard coil. WE did the same with their 43A amp.
Any 205D amp couldn't be a low budget amp project.
Some years ago I ran Telefunken (globe) TFK RE604 SET tubes. Very nice sounding tubes. Think this amp had 3W output. A friend of mine ran TFK AD1 monoblock amps. May had 4W output.
Every tube has its own sound characteristic. So I can truly understand, if one loves the sound of low output triodes, its just one has to decide which one.
Unfortunately, they become harder to source. But since the asians do copies as well, no problem today.
Any 205D amp couldn't be a low budget amp project.
Some years ago I ran Telefunken (globe) TFK RE604 SET tubes. Very nice sounding tubes. Think this amp had 3W output. A friend of mine ran TFK AD1 monoblock amps. May had 4W output.
Every tube has its own sound characteristic. So I can truly understand, if one loves the sound of low output triodes, its just one has to decide which one.
Unfortunately, they become harder to source. But since the asians do copies as well, no problem today.
Last edited:
A second retard coil deserves a 3rd filter capacitor, Right?
Cap missing from the schematic?
Or perhaps they used a Choke input filter, that would put the first cap last.
That would be easy on those expensive triodes.
Cap missing from the schematic?
Or perhaps they used a Choke input filter, that would put the first cap last.
That would be easy on those expensive triodes.
Last edited:
Second choke as CCS to output transformer
Others consider that the choke ahead of the output transformer (L2 in the 1936 schematic for the 42A attached) acts as a “constant current” induction to improve linearity and reduce distortion (see: 100 Amplifiers – Part 1 , 1916 – 45 | Lilienthal Engineering.)
Others consider that the choke ahead of the output transformer (L2 in the 1936 schematic for the 42A attached) acts as a “constant current” induction to improve linearity and reduce distortion (see: 100 Amplifiers – Part 1 , 1916 – 45 | Lilienthal Engineering.)
Attachments
OK.
But I believe that doing it that way will:
The constant current source that drives the output transformer's center tap, is going to restrict the output to Class A.
It will also limit the damping factor of the amplifier that does not use negative feedback around that output transformer.
But I believe that doing it that way will:
The constant current source that drives the output transformer's center tap, is going to restrict the output to Class A.
It will also limit the damping factor of the amplifier that does not use negative feedback around that output transformer.
I wonder if the people advocating 205's have ever bought one? Had one show up broken? Using a few as a rectifier tells me you haven't. Nothing ruins your day like an expensive ebay tube showing up broken. These aren't tough tubes. Something to be aware of.
Good.
No.
It has only common-mode effect. Not longitudinal (differential) effect..
Also, "damping factor" would be moot in the period and market that amp was designed.