Ricardo,
Regulators turn instable when input voltage drops below a certain limit.
If you haven't used them you can win half to one volt with Schottky diodes.
When I need an akward transformer I peel down a torroid and wind it up to the desired voltage. First note the total windings and the voltage under strain. Make the division and you know what to do
Regulators turn instable when input voltage drops below a certain limit.
If you haven't used them you can win half to one volt with Schottky diodes.
When I need an akward transformer I peel down a torroid and wind it up to the desired voltage. First note the total windings and the voltage under strain. Make the division and you know what to do
I read 220v AC at the mains input.
Maybe the 25v TX is not very well specified.
Thank you Salas for the kind words. I believe I will now try the four wire shunt and report the differences.
Ricardo
Thank you for comments Disco.
Yes, the 4 "grid stoppers" might have shorter tracks, but, as you can see, my goal is to have two exactely mirrored circuit, one for L ch, one for R. I like all the components in the same position and thus I have to place the resistors in the middle of the TO247 and rotate the tracks toward the gates. In this way, even if a bit longer, they all are of the same lengths. I can try to further shorter them by a couple of mm anyway. The pcb is still in the debugging stage.....
R7 is not a big problem for me as I'm gonna use a flat heatsink. It can be replaced by a jumper underneath anyaway. As you probably noticed, I arranged some other pads in series for the trimpot and for some fixed resistors in // if you want to replace it once the right value has been found.
The reason why I designed the mirrored pcbs is that I would like to place the Riaa pcbs aside of each regs in order to reduce the lentgh of the V+ & Gnd cables to 4 , maximum 5 cm.
I'll show you my complete design as soon as it will be ready for etching.....
Yes, the 4 "grid stoppers" might have shorter tracks, but, as you can see, my goal is to have two exactely mirrored circuit, one for L ch, one for R. I like all the components in the same position and thus I have to place the resistors in the middle of the TO247 and rotate the tracks toward the gates. In this way, even if a bit longer, they all are of the same lengths. I can try to further shorter them by a couple of mm anyway. The pcb is still in the debugging stage.....
R7 is not a big problem for me as I'm gonna use a flat heatsink. It can be replaced by a jumper underneath anyaway. As you probably noticed, I arranged some other pads in series for the trimpot and for some fixed resistors in // if you want to replace it once the right value has been found.
The reason why I designed the mirrored pcbs is that I would like to place the Riaa pcbs aside of each regs in order to reduce the lentgh of the V+ & Gnd cables to 4 , maximum 5 cm.
I'll show you my complete design as soon as it will be ready for etching.....
Cool...
After several atempts and using different layouts I now believe the issue might be related with the low raw Vin I am using in the riaa. (Sometimes during the day I read 32Vin for 28Vout)
I will postpone this experiment and wait for Massimo´s report. After that I will get a bigger TX.
In the meantime I did learn a lot.... shortening the gate stopper resistor legs produces audible results in terms of overall cohesion and "musicality".
The pre Q7 shunt version is quite stable and resists all forms of layouts without oscilating but these resistors must be short wired and there must be a shortest wire between both mosfets in the +Vout line.
There is a big improvement in spaciality just by increasing the shunt current. (Care must be taken in choosing the leds otherwise we can gain in noise).
Following Salas words I just produced the 4 wire version and it is working perfectly in the bench. (50Vin for 28.2Vout, R1 (10r) 2.01Vdrop)
Tomorrow I will install it and report the benefits.
Ricardo
After several atempts and using different layouts I now believe the issue might be related with the low raw Vin I am using in the riaa. (Sometimes during the day I read 32Vin for 28Vout)
I will postpone this experiment and wait for Massimo´s report. After that I will get a bigger TX.
In the meantime I did learn a lot.... shortening the gate stopper resistor legs produces audible results in terms of overall cohesion and "musicality".
The pre Q7 shunt version is quite stable and resists all forms of layouts without oscilating but these resistors must be short wired and there must be a shortest wire between both mosfets in the +Vout line.
There is a big improvement in spaciality just by increasing the shunt current. (Care must be taken in choosing the leds otherwise we can gain in noise).
Following Salas words I just produced the 4 wire version and it is working perfectly in the bench. (50Vin for 28.2Vout, R1 (10r) 2.01Vdrop)
Tomorrow I will install it and report the benefits.
Ricardo
12 cm for GND and 9cm for V.
I guess I must get a bigger TX for the DL160 riaa....
The initial one (Benz riaa) produces a much wider soundstage.... In that case I am using 44.6Vin for 28.1Vout produced by a 2 X 15V TX in series.
In the DL160 I am using a 25V TX (resulting in 34V after rectification and smoothing) to produce 28V ...... it is not enough due to the mains fluctuations...
I guess I must get a bigger TX for the DL160 riaa....
The initial one (Benz riaa) produces a much wider soundstage.... In that case I am using 44.6Vin for 28.1Vout produced by a 2 X 15V TX in series.
In the DL160 I am using a 25V TX (resulting in 34V after rectification and smoothing) to produce 28V ...... it is not enough due to the mains fluctuations...
Yup! Thank you for spotting.
I'll try to fix, but it will be difficult do miracles.....
Sorry Salas δεν καταλαβαινω
In the meantime I rotated Q2 and Q7 getting a better arrangement. I've also read what Ricardo and you reported.
If this new layout won't work, the only solution, without etching a double sided board, will be to place the gate resistors under the board with one leg as close as possible to TO247s, directly on the gate pads.
What about a ferrite bead on the other leg? Will it kill the bandwidth?
Ricardo: pls go on, don't wait for me as I still have to gather all the components (and above all the Xfrm: not easy to find a 30+30 VAC smaller than 160 W )
In the meantime I rotated Q2 and Q7 getting a better arrangement. I've also read what Ricardo and you reported.
If this new layout won't work, the only solution, without etching a double sided board, will be to place the gate resistors under the board with one leg as close as possible to TO247s, directly on the gate pads.
What about a ferrite bead on the other leg? Will it kill the bandwidth?
Ricardo: pls go on, don't wait for me as I still have to gather all the components (and above all the Xfrm: not easy to find a 30+30 VAC smaller than 160 W
)
Surely I like the idea of stopper underneath board. Use carbon stoppers. Don't know about a bead, because I never used it. If it proves handy in some builds you are to judge. Better move Q7's emitter very close to that resistor too. Its important. About Q3 I was wondering if it is oriented wrong as Q7. BC550 is CBE as we face its front, from left to right. Just check again, maybe I got it wrong by looking fast. I assume I view your PDF from components side BTW.
Years ago I saw a Counterpoint SA12 (Hybrid tube + mosfet pw amp) where the gate stoppers were mounted P2P on the TO3 legs in that way.
Ok, now I understood. Honestly speaking I didn't pay too much attention to the face orientation of the small TO92s at that stage.
Tomorrow I'll start a new layout and see what can I do with some small 1/4 W (why not a 1/8 W then?) carbon resistors underneath.
Ok, now I understood. Honestly speaking I didn't pay too much attention to the face orientation of the small TO92s at that stage.
Tomorrow I'll start a new layout and see what can I do with some small 1/4 W (why not a 1/8 W then?) carbon resistors underneath.
(and above all the Xfrm: not easy to find a 30+30 VAC smaller than 160 W
I found the following TX:
BLOCK - RK100/30 - TRANSFORMER, 100VA, 2 X 30V BLOCK|RK100/30|TRANSFORMER, 100VA, 2 X 30V | Farnell Portugal
and
BLOCK - RK63/30 - TRANSFORMER, 63VA, 2 X 30V
BLOCK|RK63/30|TRANSFORMER, 63VA, 2 X 30V | Farnell Portugal
I am worried about the secondary current ratings that are specked 510mA and 340mA respectively.
Please advise on those.... The alternative would be to use two 2x15v TX like this one:
MULTICOMP - MCTA080/15 - TRANSFORMER, 80VA, 2 X 15V
MULTICOMP|MCTA080/15|TRANSFORMER, 80VA, 2 X 15V | Farnell Portugal
In this case the secondary current rating is 2,67A
Can not understand the differences in current ratings ?!
Ricardo
Ricardo, since you are building it again, and since there is a 47R base stopper for Q3, I thought you may add an extra cap, say 100uF-470uF/35V from its base to ground, so an RC is also created, it can further filter the Vref noise, and even increase the system stability. Like I tried to edit in the attachment. Of course if it creates any problem either with working order or sonics, you can take it out. I saw some space in the layout there anyway.
Attachments
Thank you Ricardo.
I didn't consider Farnell 'cause in Italy they don't sell to DIYers
(only RS and Distrelec do) and it's a bit more complicate to ask a company to buy something for me, even if I did in the past.
I'll check the items you pointed out, (63 VA looks fine: 2 x 30 V / 2 x 1 A sec. should be)
I didn't consider Farnell 'cause in Italy they don't sell to DIYers
(only RS and Distrelec do) and it's a bit more complicate to ask a company to buy something for me, even if I did in the past.I'll check the items you pointed out, (63 VA looks fine: 2 x 30 V / 2 x 1 A sec. should be)
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Hi Salas
Thank you for the tip.... I can do it easily and will report the sonic impact. (Maybe it can also stabilize the circuit to avoid the whistle when I do the Q7 mod)
Just a question.... I am now using the 4 wire version and see that you connectd the caps minus leg to the Main GND while Q3 emiter leg is connected to sense GND....
Would you please comment on m y doubt about the several TX.... I am now prepared to order it
There is a discrepancy in the tech specs of the Block TX versus the Multicomp regarding the secondary current ratings and I must be shure.
Hi massimo
I had the same issue before regarding Farnell.... and RS does not have 30v TX under 160VA
Now I am buying on Farnell using my wives Company name.
Thank you for the tip.... I can do it easily and will report the sonic impact. (Maybe it can also stabilize the circuit to avoid the whistle when I do the Q7 mod)
Just a question.... I am now using the 4 wire version and see that you connectd the caps minus leg to the Main GND while Q3 emiter leg is connected to sense GND....
Would you please comment on m y doubt about the several TX.... I am now prepared to order it
There is a discrepancy in the tech specs of the Block TX versus the Multicomp regarding the secondary current ratings and I must be shure.
Hi massimo
I had the same issue before regarding Farnell.... and RS does not have 30v TX under 160VA
Now I am buying on Farnell using my wives Company name.
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