Success (Alas, Temporary)
OK, hooked things up, and it actually played music. Only listened for a minute or so, then put it back on the bench. I was waving my soldering iron around and heard ZIP and something fried. Dumb!!! I will look at it tomorrow.
Anyway made some measurements across resistors, as shown below. Some differences between channels in a couple places, even though most of the JFETS were pretty well matched, except the LED part and the output buffer.
Do they seem reasonable?
OK, hooked things up, and it actually played music. Only listened for a minute or so, then put it back on the bench. I was waving my soldering iron around and heard ZIP and something fried. Dumb!!! I will look at it tomorrow.
Anyway made some measurements across resistors, as shown below. Some differences between channels in a couple places, even though most of the JFETS were pretty well matched, except the LED part and the output buffer.
Do they seem reasonable?
Attachments
Very reasonable except what you note for current through R10 must be what goes through R6 also more or less. R6 currents are as expected. What happened, some crock slipped?
I think my iron touched the Vin alligator clip supplying power to the RIAA board and shorted something. Hard lesson.
When I get it working again I will re-check the currents. I know R10 should equal R6 - I will have to check it again.
When I get it working again I will re-check the currents. I know R10 should equal R6 - I will have to check it again.
Salas, I am trying some WIMA FKP4 caps. Do you have any experience with them?
It may have been a poor choice, but I will give them a chance. I have read they need 100 hours to break in.
It may have been a poor choice, but I will give them a chance. I have read they need 100 hours to break in.
HOORAY!
I went back and reconnected things, and everything lights up and looks OK.
Darn lucky!
Re-checked some voltage drops:
R2 (below Q1) - 2.3 mA
R9 (above Q5) - 6.7 mA
R7 (below Q5) - 7.3 mA
R10 (above Q2) - 4.2 mA
R6 (below Q2) - 4.0 mA
R12 (above Q6) - 7.2 mA
Look OK Salas?
Thanks!
Doug
I went back and reconnected things, and everything lights up and looks OK.
Darn lucky!
Re-checked some voltage drops:
R2 (below Q1) - 2.3 mA
R9 (above Q5) - 6.7 mA
R7 (below Q5) - 7.3 mA
R10 (above Q2) - 4.2 mA
R6 (below Q2) - 4.0 mA
R12 (above Q6) - 7.2 mA
Look OK Salas?
Thanks!
Doug
The iron tip is normally grounded...
FKP4...good industrial quality. Nothing extra special.
Your last values table makes sense.
FKP4...good industrial quality. Nothing extra special.
Your last values table makes sense.
Hi Doug
What are those yellow caps you are using in the riaa filter ? I must say they really look good !
What are those yellow caps you are using in the riaa filter ? I must say they really look good !
Thanks Salas,
RC, they are some "vintage" RelCaps.
I think I will get some more. I just wanted to get something working before ordering a bunch of "audiophile" parts. Right now I have a Multicap and a WIMA for coupling. I will see which I like better. I have some russian k40's, but they are .47 uF. The output caps are Angela tin foil.
Also, fortunately I had some Rikens left over for resistors.
Thanks for your encouragement and help.
I will keep you posted on things as they burn in.
Doug
RC, they are some "vintage" RelCaps.
I think I will get some more. I just wanted to get something working before ordering a bunch of "audiophile" parts. Right now I have a Multicap and a WIMA for coupling. I will see which I like better. I have some russian k40's, but they are .47 uF. The output caps are Angela tin foil.
Also, fortunately I had some Rikens left over for resistors.
Thanks for your encouragement and help.
I will keep you posted on things as they burn in.
Doug
Hi Salas
Still on the parts hunt !
Don't want to use any 'Unauthorised Parts'...
...but...
I found some 'nice' high-stability 1.6megs today.
Should be OK in the 1meg positions ?
Yes ?
Cheers
Si.
P.S. cap-pickers...
...what USSR silver-mica's do people like around here ?
I read the larger ones in the 'metal-cans' are good for bigger values, like 47nF & 15.5nF...
...anyone tried them ?
Still on the parts hunt !
Don't want to use any 'Unauthorised Parts'...
...but...
I found some 'nice' high-stability 1.6megs today.
Should be OK in the 1meg positions ?
Yes ?
Cheers
Si.
P.S. cap-pickers...
...what USSR silver-mica's do people like around here ?
I read the larger ones in the 'metal-cans' are good for bigger values, like 47nF & 15.5nF...
...anyone tried them ?
From my "junk" drawer. I think I bought them when I started to build a FVP preamp (Allen Wright.) I still have a pair of the small 10 nF caps if you want them. No more of the bigger ones, which I think were 3.3 nF.
I haven't really listened to it yet Salas. I just plugged it in to see if it worked. I need to re-check it after my boo-boo, but wasn't planning on listening to it until it has burned in some more. It did not sound very good after one minute of playing. 🙂
Thinking about capacitor options now. You use the Russian siver mica for RIAA, right? What about the 0.1 coupling cap?
I have an AR "The Turntable" with a new base and with Marc Morin's mass loading (using Linn springs and then adding weight (about 1.5 kg !) to the sub-chassis to get all three springs equally compressed.) Really settles the suspension down. Looks fugly though. 🙂
Currently have a Grado gold in Linn Basik LVX. Want to try a DIY tonearm. Got some nice spruce, since I build violins as another hobby. Marc also suggest getting a Grado MCZ stylus, which he says makes a HUGE improvement. It costs about $175 I think.
Thinking about capacitor options now. You use the Russian siver mica for RIAA, right? What about the 0.1 coupling cap?
I have an AR "The Turntable" with a new base and with Marc Morin's mass loading (using Linn springs and then adding weight (about 1.5 kg !) to the sub-chassis to get all three springs equally compressed.) Really settles the suspension down. Looks fugly though. 🙂
Currently have a Grado gold in Linn Basik LVX. Want to try a DIY tonearm. Got some nice spruce, since I build violins as another hobby. Marc also suggest getting a Grado MCZ stylus, which he says makes a HUGE improvement. It costs about $175 I think.
I would go for Russian Teflon coupling and FT-1 Russian bypass on the Angelas (SCR Tin FOIL OEM).
I would also test with 100K trimmer wired as rheostat for R1 so to vary the input load value until it sounds best with a given MM cart and then measure the arrived at value and change to a Dale brown fixed resistor.
Hi Salas
I get confused by all the Russian caps. Are the FT-3 or K72P what you recommend for coupling?
I get confused by all the Russian caps. Are the FT-3 or K72P what you recommend for coupling?