Finally in the process of assembing my green v1 board but discovered I didn't order the four caps for C1 and C2 
I've found some 470uf caps in my parts bin - they are Panasonic FC 470uf with two at 50v and the other two at 63v - here:
http://www.mouser.com/Search/m_Prod...uuPgMgX4pS9E0rbK8gqYL7htnU0Ms1t/VSKZGtEGJ0A==
and here:
http://www.mouser.com/Search/m_Prod...=/ha2pyFaduipszj7jDOzNRwotLyjmQ59gXTYh//Tnak=
Apparently they are low esr but not sure of the figure. Are they OK to use and maybe replace with the right caps at a later date? If so, should I mix and match (use one 50v and one 63v per board) or use the same voltage caps per board?
Appreciate any help given.
Thanks
I've found some 470uf caps in my parts bin - they are Panasonic FC 470uf with two at 50v and the other two at 63v - here:
http://www.mouser.com/Search/m_Prod...uuPgMgX4pS9E0rbK8gqYL7htnU0Ms1t/VSKZGtEGJ0A==
and here:
http://www.mouser.com/Search/m_Prod...=/ha2pyFaduipszj7jDOzNRwotLyjmQ59gXTYh//Tnak=
Apparently they are low esr but not sure of the figure. Are they OK to use and maybe replace with the right caps at a later date? If so, should I mix and match (use one 50v and one 63v per board) or use the same voltage caps per board?
Appreciate any help given.
Thanks
Interesting Dario. I have found some sensitivity to passive components in other projects, but not to the level of the FE. Come to think of it, the reason that capacitors may not have been as sensitive in other projects is that the available circuit boards didn't have much room for different caps. When space is tight, your choices are fewer. It is likely that those choices didn't have as much difference.
I love these discussions. I always learn something.
Jac
Went ahead and ordered those vishay 50 ohm 1W 1% resistors... needed two more TO220 heatsink mounting kits, so it wasn't wasting that much on shipping. I have Caddocks for R3, but I couldn't bring myself to do that again.
Project is shaping up nicely- making an integrated amp out of an Aikido 12VAC E88CC, two MyRef boards, a Glass Jar Audio A3 stepped attenuator/balance control, and their 3 input switch. The Aikido and A3 boards are populated, just waiting for transformers to show up from Antek to start testing. I went with an AS-3222 for the MyRef FE boards and an AS-1212 for the Aikido, both with steel covers. Now I have to wait for another mouser order to test the MyRef boards...
Project is shaping up nicely- making an integrated amp out of an Aikido 12VAC E88CC, two MyRef boards, a Glass Jar Audio A3 stepped attenuator/balance control, and their 3 input switch. The Aikido and A3 boards are populated, just waiting for transformers to show up from Antek to start testing. I went with an AS-3222 for the MyRef FE boards and an AS-1212 for the Aikido, both with steel covers. Now I have to wait for another mouser order to test the MyRef boards...
Interesting project. You will have plenty of gain. Many people have used the FE with only a potentiometer to control volume, so you will have gain to spare with the Aikido. Something you might try, if you are feeling experimental, is to listen to the whole system and compare to just the attentuator and FE. In other words, bypass the Aikido. It would be interesting to hear what the Aikido adds to the sound subjectively. Having recently completed a successful tube project, I am always curious about how different components play with the sound we hear.
Jac
this was my plan too. One would need to scale the two feedback resistors up, and the associated feedback cap and compensation cap downwards by the same factor. In fact I had a whole bunch of mods planned, but am just enjoying listening to it as it is.
I'm doing the same as you. It sounds good, why change it. The thing that worried me was that, once the feedback resistors where "scaled up", the feedback current would be reduced. Since part of what makes the current pump work is the impedance of the load in the feedback loop, I worry that the sound quality I like would be scaled down when the feedback resistors were scaled up. Sometimes, it's best to just enjoy the music.
Jac
I didn't order the four caps for C1 and C2
I've found some 470uf caps in my parts bin - they are Panasonic FC 470uf with two at 50v and the other two at 63v
(...)
Apparently they are low esr but not sure of the figure. Are they OK to use and maybe replace with the right caps at a later date? If so, should I mix and match (use one 50v and one 63v per board) or use the same voltage caps per board?
As temporary caps they will work pretty well but not so good soundwise (limited soundstage, somewhat compressed with a hint of harshness).
Both mixing them or mount 63V on one channel and 50V on the other is not a good thing... don't you have 4 identical low ESR caps between 220uF and 680uf?
R101/R201 are the LM317's current setting resistors, in latest versions a 1/10W resistor is indicated... earlier version indicated a Caddock power resistor only for how it 'sounded'...
Owners of earlier boards should refer to the updated BOM for boards up to v1.2:
https://docs.google.com/spreadsheets/d/1FQt1X_sSkawH3p5xfFzCF9SRIuRX70ySS9C9x0R0sRU/edit?usp=sharing
Soundwise those resistors are critical.
Interesting- I wonder if the 12AU7 Aikido would have been a better purchase then. The E88CC version has a gain of 16, the 12AU7 version's gain is just 8. I've played with a couple of tube pre with SS power section amps and really like them. Not as a complicated as a full tube setup, better bass, way less expensive for the power output. Wanted to DIY something similar and chose this setup based on the respective components' reputation in the community.
There's also a tube buffer from Glass Jar Audio... at this point I'm going to wire up another input switch with the volume control on the output. The preamp's output and some RCAs will be on the inputs so I can just switch between the two.
I'm also using powered subs, so the preamp is powering a set of volume controlled RCAs as well as the MyRefs. If I wire those in series, won't that cut the gain in half? (to 8) I don't know what other issues doing that will bring, but it's a thought.
Well, you answered my next question! Guess cutting the gain of the MyRef isn't a great option.
...and order canceled and reordered.
Thanks guys!
I didn't mean to imply that have plenty of gain would be a problem. For the most part, you will just dial down the volume control. I suppose there is some risk with noise being amplified more, but I wouldn't worry about it, just build what you have. Besides, I'm no expert but it seems like the E88CC is a nice tube, from what I've read. I understand it's relatively low input capacitance and low noise.
As for wiring the line level outputs in series, I wouldn't try it. I think you would get involved with interactions between the impedance of the two driven devices. Plus, you would be driving double the length of interconnect cable which would double the cable capacitance. The volume control is a better tool for controlling gain.
As always, there are folks on this forum with far more knowledge than me. I hope they will jump in and correct me, if I made any serious blunders.
Jac
I already asked this question but did not receive an answer yet...
is it possible to use a transformer with dual voltage "combined" like 18v-0-18v (3 wires) ?
It seems to me that i shoud connect it to AC1 - PGND/HSGND - AC2 but i'm not completely sure about it.
I have two torroids 18V-0V-18V both are 250Va and it would be nice to use them for this project.
Sorry for asking again.
is it possible to use a transformer with dual voltage "combined" like 18v-0-18v (3 wires) ?
It seems to me that i shoud connect it to AC1 - PGND/HSGND - AC2 but i'm not completely sure about it.
I have two torroids 18V-0V-18V both are 250Va and it would be nice to use them for this project.
Sorry for asking again.
Audiolex,
do you know the difference between a dual secondary/dual bridge rectifier forming a dual polarity DC supply and a centre tapped secondary/single bridge rectifier forming a dual polarity DC supply?
If you do, then it becomes obvious which diodes to omit and where to connect the centre tapped wires to the PCB.
do you know the difference between a dual secondary/dual bridge rectifier forming a dual polarity DC supply and a centre tapped secondary/single bridge rectifier forming a dual polarity DC supply?
If you do, then it becomes obvious which diodes to omit and where to connect the centre tapped wires to the PCB.
Andrew,
For the single rectifier i have to use the center tap of the transformer as GND and the outer transformer taps are connected to the rectifier creating Positive and Negative
When i look at the PS schematic 1.5 the following parts are not needed: D103/D104 and D203/D204 and C203
To form a single rectifier i have to reconnect D101 to D201 for AC1 and D102 to D202 for AC2 and connect the center tap to PGND/HSGND. Connect C103 to AC1 and AC2. Also connect DR1 to PGND
Could you confirm this?
For the single rectifier i have to use the center tap of the transformer as GND and the outer transformer taps are connected to the rectifier creating Positive and Negative
When i look at the PS schematic 1.5 the following parts are not needed: D103/D104 and D203/D204 and C203
To form a single rectifier i have to reconnect D101 to D201 for AC1 and D102 to D202 for AC2 and connect the center tap to PGND/HSGND. Connect C103 to AC1 and AC2. Also connect DR1 to PGND
Could you confirm this?
After checking again it should be like this (I think..):
D101 with jumper to D202 (AC1)
D102 with jumper to D201 (AC2)
Okay, mouser order received, parts installed. For testing and chassis layout, (and hopefully permanently) I'd like to run both boards off of a single transformer- it's an Antek 22V 300A model. What is the best way to do that? The boards each have four connections AC 1,2 and NAC 1,2- how should I handle the wiring? Would jumpers work connecting AC 1&2? Or should I split each of the AC wires into 2 at the transformer and make all four connections with each board?
Sorry, I missed this post Jac. The impedance of the feedback network won't impact the current pump - the feedback network is in // with the speakers, which will dominate the impedance. However as impedance goes up the effect of parasitic C and L will become more of an issue, so if a significant increase in impedance is wanted, the amp will have to be properly checked for stability and possibly re-compensated.
An easier solution would be to use a sub, so that a high -3db can be tolerated.