JojoD818 said:
every 10V. I'll ask my PSU supplier if this will cost too much more. maybe 340, 355 and 370V (every 15V).
JojoD818 said:
one channel. there willbe one triode and one UL amp on this layout.
navin said:
I don't think there should be any additional cost since the winder only has to tap the winding (at 340) then return and wind and tap again (at 350) then return and wind again...
the pic you posted is already stereo (2 channels) right?
what do you mean by one triode and one UL amp? i'm lost.
JojoD818 said:
there have been 400 posts on this thread! no wonder!
This amp is part of a larger stereo system.
1. An ECC88 based Steve bench Crossover and passive control center
2. 2 power amps each having one triode and one UL. The UL to power a pair of 6" woofers and the triode to power the tweeter.
Next is to find a 4 wire interconnect and socket. Each 6SL7 will recieve the HP and LP from a ECC88. Something had to connect the ECC88 to the 6SL7. right?
So I will be building 2 of these amps.
Hope I am doing this correct. Wiser men feel that I should make both channels of 1 amp UL and both channels of the other amp triode.
However since I am using 1 6SL7 between both channels and there might be some cross talk I feel that I should build a UL and Triode in each amp. I call these amps Stereo Blocks 🙂
BTW the Power tranny is 120mm dia x 100mm high! The standard size they have is 130mm x 67mm. Weight 4.3 Kgs. Cost US $50.
http://www.toroidal.com/a1_main.htm
SY said:
SY.
Got it, so I should wire them in the 220V mains windings instead of the secondary. 🙂
Which one should I use? The 100 ohms or the 350 ohms? If in the primary then I only need 1 piece right?
Thanks!
Hi Navin,
El-Ci-Ar make film caps up to about 2KV and values up to about 0.47uF. But they might have higer values. Mumbai has incredible selection , you need time to search them out.
The most unlikely shops ( just holes in the wall or small shanty like shops ) hold an incredible array of exotic stuff . Even some of the bigger shops don't have such things.
I found Sikorel caps in one such place. Unfortunately the voltages were too low. Then I found some really solid dual 3/4 inch spaced banana plugs - gold plated . Very nice ! No one else had it.
Price 120 bucks each. Suggest you get some before they raise prices. They say it's Neutrik , I don't know but I find them very good. I will never find them at that price any where abroad.
Cheers.
El-Ci-Ar make film caps up to about 2KV and values up to about 0.47uF. But they might have higer values. Mumbai has incredible selection , you need time to search them out.
The most unlikely shops ( just holes in the wall or small shanty like shops ) hold an incredible array of exotic stuff . Even some of the bigger shops don't have such things.
I found Sikorel caps in one such place. Unfortunately the voltages were too low. Then I found some really solid dual 3/4 inch spaced banana plugs - gold plated . Very nice ! No one else had it.
Price 120 bucks each. Suggest you get some before they raise prices. They say it's Neutrik , I don't know but I find them very good. I will never find them at that price any where abroad.
Cheers.
navin said:
JojoD818 said:
Dear wise JoJoD818 do you to feel that a stereo UL amp and a Stereo Triode amp would make more sense than a UL and a Triode channel in each amp?
If I was to build stereo UL and Triode amps then we would have to deal with cross talk and that means adding another 6SL7 and changing the ckt to something like what ray moth is using.
navin said:
I am not one of the wise men, that's why I don't worry too much about crosstalk and also that's why I would build a UL only amp or Triode only amp in one chassis.
So you are not going to use a UL/Triode switch anymore?
JojoD818 said:
JoJoD818 you are very modest.
No I wont need th triode/UL switch. However I am considering a Class A/AB bias becuase I can use Class A on a few days in winter (this morning I was told it hit a low of 15 deg C).
you can wire them in series with the primary winding of your power transformer. SY used 100 ohms, you may start with that one, just make sure the drop in the thermistor is low, 2 to 5volts ac, when things are all working normal, and the amp is playing music!
with 100ohm thermistor your turn on surge is limited to 2.3Amps. for a few millisecs.😀
navin said:
That's what I do too 😀 . Since I live in a tropical country with only two seasons (summer/rainy seasons) my amps are setup to play Class A during those cold rainy days and AB when it's hot. 😎
Tony said:
Thanks Tony, but would this take care of the early presence of HT while the tubes are warming up or should I still take the time thinking of a relay-based slow turn-on circuit?
even if you put them at the secondary ht, you still have a problem of B+ coming in too soon, a delay relay will take care of that.
i thought you wanted to use tube rects, but a thermistor in the primary can help the filaments too.
then you may also use thermistors after the relay. btw, what is the dc primary/secondary resistance of your power transformer, if they are high enough, you may not need those thermistors at all.
i thought you wanted to use tube rects, but a thermistor in the primary can help the filaments too.
then you may also use thermistors after the relay. btw, what is the dc primary/secondary resistance of your power transformer, if they are high enough, you may not need those thermistors at all.
Tony said:
just as I thought, but no problem, I'm sure it can be done... with help. 😀
ah yes, I do love tube rects that's why my other amp has one. I would have built the HF87 with tube rects but the power tranny I have laying around is a little smaller than what I usually use. So to save some power I decided to use ss rects this time. To further alleviate this tranny, I ordered a smaller one with a 6.3V for the input and driver tubes and a 100V winding for the bias. This way my main tranny will just power the 4 el34 and the HT.
I'd still use the thermistors in series with the primary winding to provide some protection for the heaters. But since I use ac for my heaters, what If I use the thermistors in series with the secondary going to the heaters?
Tony said:
Tony,
6SN7 and 6FQ7 are identical, apart from a slightly higher max. plate dissipation rating for 6SN7, should that matter. They have a mu of 20, compared to 60 for 12AT7. The latter have lower a-g capacitance but then higher gain.
With all respect to others I am sceptical regarding a "sonic difference" between equal tubes (microphony apart). Such a lot depends on the circuit etc. I respect hearing experiences, but hearing is subjective. How were the comparisons done - blind, over a time? Let us just say I don't believe in snake oil. For my money it is too vague when I read about "the tubes to use". I said that I did occasionally use the octals for nostalgia's sake. Otherwise I would use miniatures if only for reasons of future availability. None of the mentioned tubes were designed for especially low microphonics, and my choice between the 2 types would be solely with regard to desired gain.
Differences between makes have been reported; that I must accept, to my disappointment. Measured distortion for either type in my experience totally depended on circuit values. (There is also ECC85, ECC88 and others on the table.)
Regards.
Johan,
thanks a lot for your confirmation.😀
jojo,
if you want to use thremistors is series with the filaments, make sure that the voltage drop acrross it is a few millivolts when heaters are all warmed up.
thanks a lot for your confirmation.😀
jojo,
if you want to use thremistors is series with the filaments, make sure that the voltage drop acrross it is a few millivolts when heaters are all warmed up.
JojoD818 said:
JoJoD818, How do you do this? Since we have similar climes i feel safe copying you.
do you have a switch or do you manually set bias voltages if the ambient temp is below 25 deg C? or is it more complex in that the bias is set via a temperature sensor that senses the ambient and sets the bias automatically?
Also my power tranny guy wanted confirmation on the specs of the power tanny. Since he lives 1500km away and I cant send the power tranny back I'd like to double check..
Primary 230VAC
Secondary:
370V AC CT (370-0-370), 1Amp, additional taps at 340V and 355V
6.3V AC 8A CT (for EL34 heaters)
6.3V AC 4A CT (for 6SL7 and 6Sn heaters) to be rectified to DC
70V AC (no need for CT) 0.2A for bias
Are the above specs ok? Will i need additional windings?
Is there a need for a shield between primary and secondary?
navin,
if you are using wayne's psu schematics then you won't need a 370-0370 volts, just a staight 370volts with taps at 340volts, otherwise the rest of the specs are good.
if you are using wayne's psu schematics then you won't need a 370-0370 volts, just a staight 370volts with taps at 340volts, otherwise the rest of the specs are good.
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