Hi Folks!
I'm seeking advice for the power supply for my stereo bloc built based on David C. Gillespie's mod for Eico's HF-60.
A GZ34 > 20uf > 3H > 20uf > 1K3 > 20uf > 51K > 20uf was configured for a monobloc.
My question is, does it have enough amperage to power a stereo bloc?
Wish to build it like those Western Electric or Altec style..... vintage look!
So, I'll have big oil caps sticking up on deck.
I'm using the potted version of A-431 for a 60 watts build with 6550 or KT88.
Any advce forecoming, will be greatly appreciated.
Thanks for looking.
Zekk
I'm seeking advice for the power supply for my stereo bloc built based on David C. Gillespie's mod for Eico's HF-60.
A GZ34 > 20uf > 3H > 20uf > 1K3 > 20uf > 51K > 20uf was configured for a monobloc.
My question is, does it have enough amperage to power a stereo bloc?
Wish to build it like those Western Electric or Altec style..... vintage look!
So, I'll have big oil caps sticking up on deck.
I'm using the potted version of A-431 for a 60 watts build with 6550 or KT88.
Any advce forecoming, will be greatly appreciated.
Thanks for looking.
Zekk
I think based on experience that you will need two 5AR4 and chokes should have twice the current rating and half the DCR of the items used in mono amp.. (Resistors halved if powering both channels) You can also double the capacitance ahead of the choke and go significantly higher than that on the rest.
Hi everyone, I use to own a pr of 60's..I came across this online.
Can anyone comment on the mod's done to these 60's
especially the part about the "motor run capicitor'
never heard of this before, and adding a choke'..
Thanks Bob.
Introduction
EICO, unlike McIntosh, Marantz, or Fisher, isn't quite spoken with the reverent tones with discussing the best of the vintage amplifiers, but to do so would be a mistake. From their budget units, up to the the flagship model, the HF-60, they represented a serious competitor to Heath and Dynaco, offering good value for the hobbyists of yore. When I had the rare and unexpected chance to buy a pair, I went for it, knowing I would be hearing with one of the best EL34s amplifiers around.
The Amplifiers
So what is an EICO HF-60? It's a monoblock amplifier - requiring two for stereo - featuring 5AR4 tube rectification, the classic Mullard 5-20 circuit with an EF86 and 6SN7 driving EL34 output tubes in Ultralinear, fixed bias, and the legendary Acrosound TO-330 output transformer. There's nothing tricky going on here circuit-wise: current sinks, current sources, regulators, dc filaments, etc are non-existent, but component quality is still quite high with wirewound resistors, good tube sockets, and a really nice hunk of iron. Biasing is through two pots: one to balance between output tubes while the other is raw bias. These came as very basic kits with no circuit boards: the end-user was expected to be experienced enough to do point-to-point wiring.
Another thing to note is the high plate voltage and bias, making the HF-60 run steep Class A. 500VDC on the plates with 65mA means the EL34 output tubes are running 32.5Ws (plate + screen) of dissipation, right on the bleeding edge of their maximum rating. If the lights are off, a faint red glow can be seen on the plates(!) which, according to the manual, is considered normal operation! Back in the day, this was no big deal since you could pop down to the local store to pick up your new set of Mullard EL34s, but now with the high price of quality old-stock tubes, a user of this amplifier may want to dial back a few milliamps.
Note that the HF-60s are not stock. The addition of the 1.5H choke and the large motor run capacitor helps to clean up the power supply. Also the "battery bias" mod where the EF86 is biased via a 1.5V AA battery - and cap coupled - supposedly improved the treble and detail. I have, however, never heard a stock HF-60 so I cannot compare.
Can anyone comment on the mod's done to these 60's
especially the part about the "motor run capicitor'
never heard of this before, and adding a choke'..
Thanks Bob.
Introduction
EICO, unlike McIntosh, Marantz, or Fisher, isn't quite spoken with the reverent tones with discussing the best of the vintage amplifiers, but to do so would be a mistake. From their budget units, up to the the flagship model, the HF-60, they represented a serious competitor to Heath and Dynaco, offering good value for the hobbyists of yore. When I had the rare and unexpected chance to buy a pair, I went for it, knowing I would be hearing with one of the best EL34s amplifiers around.
The Amplifiers
So what is an EICO HF-60? It's a monoblock amplifier - requiring two for stereo - featuring 5AR4 tube rectification, the classic Mullard 5-20 circuit with an EF86 and 6SN7 driving EL34 output tubes in Ultralinear, fixed bias, and the legendary Acrosound TO-330 output transformer. There's nothing tricky going on here circuit-wise: current sinks, current sources, regulators, dc filaments, etc are non-existent, but component quality is still quite high with wirewound resistors, good tube sockets, and a really nice hunk of iron. Biasing is through two pots: one to balance between output tubes while the other is raw bias. These came as very basic kits with no circuit boards: the end-user was expected to be experienced enough to do point-to-point wiring.
Another thing to note is the high plate voltage and bias, making the HF-60 run steep Class A. 500VDC on the plates with 65mA means the EL34 output tubes are running 32.5Ws (plate + screen) of dissipation, right on the bleeding edge of their maximum rating. If the lights are off, a faint red glow can be seen on the plates(!) which, according to the manual, is considered normal operation! Back in the day, this was no big deal since you could pop down to the local store to pick up your new set of Mullard EL34s, but now with the high price of quality old-stock tubes, a user of this amplifier may want to dial back a few milliamps.
Note that the HF-60s are not stock. The addition of the 1.5H choke and the large motor run capacitor helps to clean up the power supply. Also the "battery bias" mod where the EF86 is biased via a 1.5V AA battery - and cap coupled - supposedly improved the treble and detail. I have, however, never heard a stock HF-60 so I cannot compare.
A motor run capacitor is a comparatively rugged polypropylene/oil cap used in electric motors for phase quadrature. They're made to last in hard use, and can withstand surprising short-term overvoltages. Somes folks will use them as the first (input) capacitor in a tube amp B+ supply (including the Marantz 8b), or even for all supply caps.
They're gaining another popularity in *reducing* B+ voltage, often too high with modern AC line voltages on vintage electronics designed for 115 volt supplies and inexpensive replacement tubes. 500 volts on EL34's is seriously too high, for example. A smaller-than-stock value of input capacitance is chosen (for a practical B+ voltage), then a choke is added to keep down ripple.
All good fortune,
Chris
They're gaining another popularity in *reducing* B+ voltage, often too high with modern AC line voltages on vintage electronics designed for 115 volt supplies and inexpensive replacement tubes. 500 volts on EL34's is seriously too high, for example. A smaller-than-stock value of input capacitance is chosen (for a practical B+ voltage), then a choke is added to keep down ripple.
All good fortune,
Chris
The post you quoted - those are my HF-60s - basically done by a previous owner. I just tidied up the wiring and changed the input cap value.
If I remember correctly, After the 5AR4 rectifier, I used two 22uF/350V caps in series (with resistors in parallel to each cap), then to a 1.5H Dynaco choke attached to the side of the chassis (but still internal). The original can cap position was replaced by a 40 or 50uF polypropolene "Suzuki" capacitor. B+ - with modern line voltages - is still a high 495VDC, but that's no problem for original Mullard EL34 XF2 tubes. Shuguang EL34s - surprisingly - could also take the abuse.
The Eico HF-60 certainly was designed with no regard for tube life, but more for max power with a claimed 60Ws. Just a sign of the wattage wars of the late 50s.
If I remember correctly, After the 5AR4 rectifier, I used two 22uF/350V caps in series (with resistors in parallel to each cap), then to a 1.5H Dynaco choke attached to the side of the chassis (but still internal). The original can cap position was replaced by a 40 or 50uF polypropolene "Suzuki" capacitor. B+ - with modern line voltages - is still a high 495VDC, but that's no problem for original Mullard EL34 XF2 tubes. Shuguang EL34s - surprisingly - could also take the abuse.
The Eico HF-60 certainly was designed with no regard for tube life, but more for max power with a claimed 60Ws. Just a sign of the wattage wars of the late 50s.
kstagger..I just ck ur homepage..that's exactly where I found the HF60 article.
this is really ironic!..is there anything else "info" about this amps you might want to pass along' I sold my 60's when I moved to Shanghai for 3 yrs..
I'm thinking very hard about getting another pair, and am always looking for mods "upgrades" especilly to the power supply.
Thanks, for the original and ur reply here.
Bob.
this is really ironic!..is there anything else "info" about this amps you might want to pass along' I sold my 60's when I moved to Shanghai for 3 yrs..
I'm thinking very hard about getting another pair, and am always looking for mods "upgrades" especilly to the power supply.
Thanks, for the original and ur reply here.
Bob.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.