Me? Choke loaded. Mundorf M-cap capacitor. SE opt xformer.It is good to calculate the whole setup - choke + cap + xformer first.
Parafeed Iron
My parafeed amp has a EI-84 OPT, 45mm high, no airgap.
The load choke is EI-96, 55mm high.
The one on the left is the OPT, on the right the load choke.
It uses a 4uF oil cap to block the DC.
My first impressions of these amps: bass!
I still need to do some measurements on bandwidth and THD, but it is very listenable and plenty loud 😎.
For comparison: the OPTs of my PP EL84 amp are also EI-84, but only 30mm high. Those OPTs were rated at 30W nominal, going down to 30Hz (12Hz -3dB low signal). These are datasheet numbers, not my own measurements...
Considering the parafeed OPTs are almost twice as high, I should be able to get very low frequencies at full power.
My parafeed amp has a EI-84 OPT, 45mm high, no airgap.
The load choke is EI-96, 55mm high.
The one on the left is the OPT, on the right the load choke.
It uses a 4uF oil cap to block the DC.
My first impressions of these amps: bass!
I still need to do some measurements on bandwidth and THD, but it is very listenable and plenty loud 😎.
For comparison: the OPTs of my PP EL84 amp are also EI-84, but only 30mm high. Those OPTs were rated at 30W nominal, going down to 30Hz (12Hz -3dB low signal). These are datasheet numbers, not my own measurements...
Considering the parafeed OPTs are almost twice as high, I should be able to get very low frequencies at full power.
Attachments
Remember that the inductance of a parafeed choke and a parafeed OT are in parallel - which is like resistances in parallel. This means that a good deal of the impressive inductance figures are wasted. The capacitive losses in the choke load cannot be ignored either.
Coupled with putting it all through a big cap which has an impact on the sound.
What galls me me overall is the significantly increased price of the OT and Choke combination which starts to make the quality OT option look far more attractive.
Parafeed is not for me.
Shoog
I use a setup as described in my earlier post, #28.
An inherently linear triode will be most linear with a horizontal (or near horizontal) load line. MOSFET gyrator plate load will improve sonics quite noticeably across the board.
Use a choke if you don't have sufficient B+, but otherwise (and when designing from scratch) an active plate load is quite a lot better.
If you have a highish plate resistance in your output tubes, and a little bit lowish primary impedance on your OT, then using a CCS between plate load source and ground with 10mA or so thru it will bring improvements, to the low and high ends particularly.
As per cost, using a small, possibly cheap OT with a russian super high quality cap that costs next to nothing, and maybe $10 to $25 of parts for the plate load (most of it for heat sink), you'll easily be financially better off going parafeed than big OT. Add at most $30 of stuff per channel, halve the OT cost. Still come out ahead in sound quality.
Like I said, most people would be quite surprised with MOSFET load + KBG MN cap + lowly cheap Hammond OT. This might not be the best there is to have in the whole world, but it will be better than just using an OT of twice the price in a regular setup.
An inherently linear triode will be most linear with a horizontal (or near horizontal) load line. MOSFET gyrator plate load will improve sonics quite noticeably across the board.
Use a choke if you don't have sufficient B+, but otherwise (and when designing from scratch) an active plate load is quite a lot better.
If you have a highish plate resistance in your output tubes, and a little bit lowish primary impedance on your OT, then using a CCS between plate load source and ground with 10mA or so thru it will bring improvements, to the low and high ends particularly.
As per cost, using a small, possibly cheap OT with a russian super high quality cap that costs next to nothing, and maybe $10 to $25 of parts for the plate load (most of it for heat sink), you'll easily be financially better off going parafeed than big OT. Add at most $30 of stuff per channel, halve the OT cost. Still come out ahead in sound quality.
Like I said, most people would be quite surprised with MOSFET load + KBG MN cap + lowly cheap Hammond OT. This might not be the best there is to have in the whole world, but it will be better than just using an OT of twice the price in a regular setup.
The problem with this approach is the massive waste of power needed to run the CCS. It will work, but an already inefficient amp will become horribly inefficient.
This becomes a problem when it is on for most of the day.
Shoog
This becomes a problem when it is on for most of the day.
Shoog
ccs kills bass response in most tube circuits.
change the coupling caps to 1uf anything but wima. stay away from the square caps in coupling.
change the coupling caps to 1uf anything but wima. stay away from the square caps in coupling.
A gyrator is not a constant current source, it's a constant voltage source at DC with a very high impedance at AC.
But that said... are you serious DavesNotHere?
Shoog: True, but I'm not in this game for efficiency, but sound quality. Also maybe most people don't really need nearly as much power as they think they do (some do need it). 1W is plenty for the vast majority - provided it's a really good 1W.
I have at the moment regular, not at all sensitive speakers (less than 90dB/V) and a 1W push pull DHT amp with gyrator plate loads (and CCSs at the tail). When I use speakers I don't use even third the volume, and it's so loud it could disturb the other room.
But that said... are you serious DavesNotHere?
Shoog: True, but I'm not in this game for efficiency, but sound quality. Also maybe most people don't really need nearly as much power as they think they do (some do need it). 1W is plenty for the vast majority - provided it's a really good 1W.
I have at the moment regular, not at all sensitive speakers (less than 90dB/V) and a 1W push pull DHT amp with gyrator plate loads (and CCSs at the tail). When I use speakers I don't use even third the volume, and it's so loud it could disturb the other room.
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