Eico ST-40, Redo/Modo
- Thread starter Kegger
- Start date
So how's everybody's output on this? Mine seems to be pretty low as I have to crank it past noon to get any sort of listenable level on the AR 10pis.I know it will do better on the A7s, but my 5 wpc EL84 amp gets louder faster.
I'm gong to roll in another amp today and take this one back to the bench as it looks like I need to address some hum in the straight amp connection Keg hooked up from the Tape in's to pin 7 of the 12AT7s too.
EDIT: I'm guessing those green numbers in the boxes are voltages, but the Ux numbering is throwing me off as Keg also has the tubes marked as U also. Am I right in my assumption??
I'm gong to roll in another amp today and take this one back to the bench as it looks like I need to address some hum in the straight amp connection Keg hooked up from the Tape in's to pin 7 of the 12AT7s too.
EDIT: I'm guessing those green numbers in the boxes are voltages, but the Ux numbering is throwing me off as Keg also has the tubes marked as U also. Am I right in my assumption??
Dandy
Addicted Member
Remember this is modded for triode operation.
The output is lower on the direct input from the Tape In to the grid of the 12AT7. I tried input from my tape deck via a 50k pot and had to turn that pot past 12. But, the output on the MM phono inputs of mine is fine for normal listening levels at 9.
Yes, the figures in green are voltages, though your screenshot is too small to read clearly. Compare them with mine reported in post #42 above.
The output is lower on the direct input from the Tape In to the grid of the 12AT7. I tried input from my tape deck via a 50k pot and had to turn that pot past 12. But, the output on the MM phono inputs of mine is fine for normal listening levels at 9.
Yes, the figures in green are voltages, though your screenshot is too small to read clearly. Compare them with mine reported in post #42 above.
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Dandy
Addicted Member
On another topic related to this rebuild, after I rebuilt the PECs with discrete components, I find that the amp is bass-heavy when using the phono inputs. This may be related to the omission of the connection I mention in post #62, so I may try this on my ST40.
The issue is that there is a 1K resistor to wire 5 of the PEC in the HF81 schematic, as seen in the snip below. Should this also be used with the ST40?
On further reflection, I think not!
The issue is that there is a 1K resistor to wire 5 of the PEC in the HF81 schematic, as seen in the snip below. Should this also be used with the ST40?
On further reflection, I think not!
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I have to get some longer wires for MM Phono operation, but my line level inputs into the MX inputs is low too and also needs to run up to 12 to 2 for normal volumes. I'll do some more testing tomorrow, but I'm basically just vetting this thing so I can move it for his Mom. The iron obviously seems good, so that's a huge relief!
Dandy
Addicted Member
Wondering about the phono stage, I remembered the Eico ST84 preamp mods here: http://tronola.com/html/st84_mods.html. The phono stage on this preamp is the same as in the ST40. I've just done them on my amp with good results.
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