No they will not cause a problem, but it will be nice you will get another one to match a final pair at least aesthetically, if you will decide the phono build is a keeper. To have no worries in the back of your mind of maybe the two channels have a slightly different tone somehow due to unequal core size and copper thickness trafos.
All this talk about transformers is interesting - I managed to get in on the group buy, and I also had to pick up a 300VA transformer today for another amp project. I ended up getting a hands on tour of the factory and watched as they made up custom transformers. It's a real art - I've not really given it a second thought. I think from now on, I will get custom builds for each project so that I get the exact specs I need and I know the quality of the build.
That said, I'm undecided on this project yet what specs, whether an 80VA or 2X 30 or 50VA's. If I hadn't seen all this talk about over-specified transformers, I probably would have just used a dual winding 30VA.
Anyway, keen to see how this thing sings eventually.
That said, I'm undecided on this project yet what specs, whether an 80VA or 2X 30 or 50VA's. If I hadn't seen all this talk about over-specified transformers, I probably would have just used a dual winding 30VA.
Anyway, keen to see how this thing sings eventually.
Hi,
I am a bit lost with the power supply ...
I will work with MM cartridge.
Which DC voltage should expect the board?
34-36V (cf biasing in the Folded Simplistic PC guide)?
Is it also valid for the MM version?
I will use a two shunt regulators after each circuit of the transfo.
In stock I have 3 transfos:
- 300VA toric 2*24V
- 85VA (classic) 2*28V
- 50VA toric 2*18V
Can I use one of those ?
Thank you
I am a bit lost with the power supply ...
I will work with MM cartridge.
Which DC voltage should expect the board?
34-36V (cf biasing in the Folded Simplistic PC guide)?
Is it also valid for the MM version?
I will use a two shunt regulators after each circuit of the transfo.
In stock I have 3 transfos:
- 300VA toric 2*24V
- 85VA (classic) 2*28V
- 50VA toric 2*18V
Can I use one of those ?
Thank you
R2, R3 will surely need to be picked only after you know your input JFETs IDSS.
1% is OK for general resistor positions. R4, R5, R6, R13, R14 can be picked for even better tolerance if able.
Closing in on build start 
Got my bords the other day along with 4ea k369 matched to aprox 10,15
have ordered 3,3ohm for R2,3
Ordered 2 different C4:
-3,3uf Mundorf Zn and 3,3uf Clarety MR
-C3 Jupiter HT (100nf)
-Takman rey 25for riaa
100 ohm Charcroft Z-Foil for R1 and Charcroft Z-Foil for R14
Will not fit the dip switch but use 100ohm fixed input impedance for my AT33EV cart
- Silmic II for the reg
Have some R-cores from Selectronic witch i am pleased with but wrong voltage,
will possibly try some vacuum impregnated toroids from http://www.toroidy.pl
Am gonna run aprx 2 x 300va since i found that crucial im my B3 dac
Hope i haven't missed something?
Will be fun to see how it compares with the AAPP
Per
Got my bords the other day along with 4ea k369 matched to aprox 10,15
have ordered 3,3ohm for R2,3
Ordered 2 different C4:
-3,3uf Mundorf Zn and 3,3uf Clarety MR
-C3 Jupiter HT (100nf)
-Takman rey 25for riaa
100 ohm Charcroft Z-Foil for R1 and Charcroft Z-Foil for R14
Will not fit the dip switch but use 100ohm fixed input impedance for my AT33EV cart
- Silmic II for the reg
Have some R-cores from Selectronic witch i am pleased with but wrong voltage,
will possibly try some vacuum impregnated toroids from http://www.toroidy.pl
Am gonna run aprx 2 x 300va since i found that crucial im my B3 dac
Hope i haven't missed something?
Will be fun to see how it compares with the AAPP
Per
Thanx,
yes i read in a previous post that y mentioned pulling the input all the way up to R1,
Loses some possibility for changing but im a believer of KISS.(ing)
AAPP = Analogue addicts
have built 2 , one with CMF55 and one with Takman carbon,
Sounds sweet but struggle with latchup on the OPA 637
yes i read in a previous post that y mentioned pulling the input all the way up to R1,
Loses some possibility for changing but im a believer of KISS.(ing)
AAPP = Analogue addicts
have built 2 , one with CMF55 and one with Takman carbon,
Sounds sweet but struggle with latchup on the OPA 637
Last edited:
The FSP will be an alternative sound. Open loop, discrete, passive Riaa, minimal junctions count. Its good you have another one with an op-amp and feedback nested Riaa so you can weigh pros & cons and decide what will suit your listening habits best.
The DIP switch and Rx load resistors are always easy to populate in the future in case of need, so no worries in starting fixed since the cart and its best load are given in your situation.
The DIP switch and Rx load resistors are always easy to populate in the future in case of need, so no worries in starting fixed since the cart and its best load are given in your situation.
Hi Salas, Mike, All
I finished my initial build with some parts still to be obtained but it’s my birthday soon so Charcroft 47K r14 to come. Also I’ll be replacing the pig R13 2K2 for something a little nicer but wanted to get some testing done. I’m aware that temperature stability is needed for that part but I was keen to start my build. Please excuse the battle cases which have seen much use over the years but new front and back plates are on order.
I’m new to board etching but the PSU is fairly straight forward so I did it that way. I like to try my hand whenever I can but my work can be a little amateurish but still effective.
My cartridges
Denon DL103R and Lyra Dorian cartridges.
So I’ve set it up 56dB for the Dorian first as it only involves leaving things out and a change of R13.
Later I’ll try the Denon once the Dorian has had a spin.
So just a few words on the Construction guide, boards and Mike’s kit.
Well one word actually
Superb.
The guide really helped and made the build just plain good fun with all of the info needed for working boards. The boards are up to the usual great quality and Mike’s kit is well thought out and super quality also.
Ok a few test results
When testing the raw power supply using 18V transformers I got 58V OP so the good old UK mains transformed 18V into a 20V for no extra cost.
So I trimmed the OP with an RC filter tacked onto the end of the build guide one which gave me a nice 48V and a little extra filtering.
BTW I used 18V 80VA transformers as I had those to hand I also did what I usually do for first builds. Went to my parts box and used what I have. Those caps will change in due course but for now they got the phono working and allowed some testing to get done.
All measurements taken out of the boxes.
Board 1
Rail voltage 33.2 (set to allow 3.6V bias setting).
TP1 to ground 7.77V
Board 2
Rail Voltage 33.4 (set to allow 3.6V bias setting).
TP1 to ground 7.81V
Both boards have the red LED for the string of four and I just bought a few more to get the string of three to required 5.8V
So the circuit seems to be doing what it should.
I have some Charcroft Zfoils 47K and 470R on order (it’s my birthday soon)
The parts box also provided C3 0.1uf Mundorf SIO and 2u2 Supreme and also Charcroft Zfoils for RX1 and 2.
So nearly there.
I’m not going to be listening until I have the rest of the required components as I want to give an opinion based on the boom.
So looking good as expected from the long design period given to this amp.
The circuit itself reminds me more than a little of a tube stage so it will be interesting to hear how it sounds.
I’ll keep you posted.
I finished my initial build with some parts still to be obtained but it’s my birthday soon so Charcroft 47K r14 to come. Also I’ll be replacing the pig R13 2K2 for something a little nicer but wanted to get some testing done. I’m aware that temperature stability is needed for that part but I was keen to start my build. Please excuse the battle cases which have seen much use over the years but new front and back plates are on order.
I’m new to board etching but the PSU is fairly straight forward so I did it that way. I like to try my hand whenever I can but my work can be a little amateurish but still effective.
My cartridges
Denon DL103R and Lyra Dorian cartridges.
So I’ve set it up 56dB for the Dorian first as it only involves leaving things out and a change of R13.
Later I’ll try the Denon once the Dorian has had a spin.
So just a few words on the Construction guide, boards and Mike’s kit.
Well one word actually
Superb.
The guide really helped and made the build just plain good fun with all of the info needed for working boards. The boards are up to the usual great quality and Mike’s kit is well thought out and super quality also.
Ok a few test results
When testing the raw power supply using 18V transformers I got 58V OP so the good old UK mains transformed 18V into a 20V for no extra cost.
So I trimmed the OP with an RC filter tacked onto the end of the build guide one which gave me a nice 48V and a little extra filtering.
BTW I used 18V 80VA transformers as I had those to hand I also did what I usually do for first builds. Went to my parts box and used what I have. Those caps will change in due course but for now they got the phono working and allowed some testing to get done.
All measurements taken out of the boxes.
Board 1
Rail voltage 33.2 (set to allow 3.6V bias setting).
TP1 to ground 7.77V
Board 2
Rail Voltage 33.4 (set to allow 3.6V bias setting).
TP1 to ground 7.81V
Both boards have the red LED for the string of four and I just bought a few more to get the string of three to required 5.8V
So the circuit seems to be doing what it should.
I have some Charcroft Zfoils 47K and 470R on order (it’s my birthday soon)
The parts box also provided C3 0.1uf Mundorf SIO and 2u2 Supreme and also Charcroft Zfoils for RX1 and 2.
So nearly there.
I’m not going to be listening until I have the rest of the required components as I want to give an opinion based on the boom.
So looking good as expected from the long design period given to this amp.
The circuit itself reminds me more than a little of a tube stage so it will be interesting to hear how it sounds.
I’ll keep you posted.
Attachments
thanks Salas
yes a little tweaking of the LEDs still required but still pretty close to the 1% but it could be a little closer.
I'll get back to you on the TP2 to ground readings when I do the hot box measurements.
ATB
Hi Salas,
since I have forgot (?) to order 2 pairs of k369s I will try to make the "folded" with just one pair (maybe Mike has another pair, I will check). Maybe the gain is just enough for my AT OC9.
Since he also provided me with 1.2k Resistors for R13: Can I use them with just one Jfet?
klaus
since I have forgot (?) to order 2 pairs of k369s I will try to make the "folded" with just one pair (maybe Mike has another pair, I will check). Maybe the gain is just enough for my AT OC9.
Since he also provided me with 1.2k Resistors for R13: Can I use them with just one Jfet?
klaus