what i can try is a single 40uf PP against 40uF lytic (no so expensive try), so i shall see if music is in the cheap way or in the 40uF change !!
😀
😀
PS looks better.
I would try to raplace that orange cap with a SCR MPK if you can get it for few euros. Also I would drop the 2A3 grid resistor to 220K.
Honestly, I don't think your amp is worth big spending. You have too many technical limitations.
Cheers,
45
I would try to raplace that orange cap with a SCR MPK if you can get it for few euros. Also I would drop the 2A3 grid resistor to 220K.
Honestly, I don't think your amp is worth big spending. You have too many technical limitations.
Cheers,
45
Re: I listen to this
Which setting of the jumper do you prefer; CCS or follower?
What difference do you notice in the sound?
Cheers,
Michael
Jaap said:
Which setting of the jumper do you prefer; CCS or follower?
What difference do you notice in the sound?
Cheers,
Michael
I have no jumper
I only use it as a beta-follower.
Manfred Huber used to be around here, perhaps we can ask him. I remember he told me that he liked his transformer coupled amps best.
I only use it as a beta-follower.
Manfred Huber used to be around here, perhaps we can ask him. I remember he told me that he liked his transformer coupled amps best.
The image attached (huber design) is barely readable.
If i had to try srpp (simplest step to do for me), do you think 6sl7 may be used here (i have quite enough in stock, as well as a spare octal base)...whereas I have only one 6sn7.
What will be the value of the two equal Rk1 and Rk2 ?
I have Rk = 2R1 + ra (mu/1), R1 being the load of following stage.
ra 6s7l = 44000 mu=70
r1 is the load of the 2a3 ? i guess 700 ohm bypassed, i have read (somewhere?) it should be around 3.5k unbypassed.
so, in first case both Rk are around 2k, in second case 7.7k
Also read srpp bypass cap could be anything above 1uF.
There are also heater considerations to take in count for heater-cathode voltage (elevated center tap ?)
if you have direct link to some schematics or srpp easy explanation, I would be grateful.
If i had to try srpp (simplest step to do for me), do you think 6sl7 may be used here (i have quite enough in stock, as well as a spare octal base)...whereas I have only one 6sn7.
What will be the value of the two equal Rk1 and Rk2 ?
I have Rk = 2R1 + ra (mu/1), R1 being the load of following stage.
ra 6s7l = 44000 mu=70
r1 is the load of the 2a3 ? i guess 700 ohm bypassed, i have read (somewhere?) it should be around 3.5k unbypassed.
so, in first case both Rk are around 2k, in second case 7.7k
Also read srpp bypass cap could be anything above 1uF.
There are also heater considerations to take in count for heater-cathode voltage (elevated center tap ?)
if you have direct link to some schematics or srpp easy explanation, I would be grateful.
mahleriana said:
There is an SRPP driver stage I have used successfully with both 45 and 2A3 on my site here:
http://www.kta-hifi.net/projects/amp_page/45dht/45_dht.html
The link to the schematic is at the bottom of the page. No cathode bypass caps required, although a B+ of slightly over 300V is required. 6SL7 is operated at 2mA which provides close to the best performance this type is capable of..
Be careful what you read, there is no substitute for practical experience, read less, and experiment more...
I might mention that this is the oldest amplifier of the ones I have designed and built that I still own..
Hi,
When you have both halves of the 6SL7 available for one channel I wouldn't needlessly complicated life and try paralling both for a start and ommit the cathode resistors bypass caps.
If that doesn't work out to your liking a mu-follower should be better than a SRPP.
Personally I have tried a mu-follower driving an un bypassed 2A3 and it's a much cleaner, faster sound than SRPP tout court.
SRPP like to see a well defined low Zin load for best performance and even than....
Most of your observations can be attributed to the sluggishness of the bypass caps.
Ciao, 😉
When you have both halves of the 6SL7 available for one channel I wouldn't needlessly complicated life and try paralling both for a start and ommit the cathode resistors bypass caps.
If that doesn't work out to your liking a mu-follower should be better than a SRPP.
Personally I have tried a mu-follower driving an un bypassed 2A3 and it's a much cleaner, faster sound than SRPP tout court.
SRPP like to see a well defined low Zin load for best performance and even than....
Most of your observations can be attributed to the sluggishness of the bypass caps.
Ciao, 😉
I made a few tests :
speed was definitively a problem of PSU (values of caps)
Putting back some bypass caps did not change speed, just changing impendance/treble issues.
Big values electrolytics were better than small values PP caps (2-10uF, in stock SCR or AudynCap) concerning speed (but of course there is much more detail with PP and treble is cutoff with lytics)
I am now listening to 2200 uF bypass on the (still single) 6SN7 and 100 uF on the 2a3.
Control seems good.
I will try to buy tomorrow (the day before christmas...) a higher value for the 2a3 and see how it works.
speed was definitively a problem of PSU (values of caps)
Putting back some bypass caps did not change speed, just changing impendance/treble issues.
Big values electrolytics were better than small values PP caps (2-10uF, in stock SCR or AudynCap) concerning speed (but of course there is much more detail with PP and treble is cutoff with lytics)
I am now listening to 2200 uF bypass on the (still single) 6SN7 and 100 uF on the 2a3.
Control seems good.
I will try to buy tomorrow (the day before christmas...) a higher value for the 2a3 and see how it works.
mahleriana said:
Hi,
Merry x'mas, here is my 2 cent worth,
If you must have the 6SN7, make a cathode follower driver stage with the other half of the 6SN7 and load it with a CCS cathode load and run it as hot as you could to drive the 2A3 direct-couple. That will improve the speed.
IF you are open for other tubes then
DITDITCH THE 6SN7!!!
you will never get real speed even with more complication...
Get some 6C45pi, pop in a blue LED on the cathode without a bypass cap and use tubelab's cirtcuit topology http://www.tubelab.com/Simple45.htm
you will get what your are looking for... and do not oversize your PSU cap unnecessarily, from my experience, you will get heavier bass with big psu cap but you loose speed! if you must, regulate the PS and you will have the best of both world.
I'd built SPUD with 6C45pi, LED cathode has the best speed, I'd also use it to drive a 12B4, driven by a 12B4. very fast in both cases. Even tried it on 1626, fast and warm... a very rare combination.
I'd experimented with 2A3 with SRPP 6SN7, e88cc cascode, 5842 ground cathode, Aikido as driver, 6C45pi driver. for the best simplicity to performance the 6C45pi takes the lead. 5842 will give you more romantic flavour, 6C45pi can give you SS type of speed with Blue LED, red LED is more tuby.
Aikido is the best..... no color, no MSG😉 😉 , no fake bass boom, correct speed. BUT with added complication as there are more tubes.
Happy new year
Ken
A MOSFET source follower will also work extremely well, better than the 6SN7 cathode follower. The 6SN7 voltage amp should have decent current through it, but I think you hit diminishing returns past 8mA or so if it's CCS-loaded.
I will anyway try the led bias as soon as a shop is opened...
very easy and cheap try to make ! (and perhaps battery bias)
for 6c45pi, the problem is that the whole thing will give near 200mA (my trannie is 200 mA and I have to buy another choke (mine is 150 mA)
I will probably buy a new tranny anyway in near future if i want to try one day a DC design as mine has to low voltage.
Can someone give me a simple explanation of how to get a fixed bias from a tranny bias tap (my hammond has 50v) ?
very easy and cheap try to make ! (and perhaps battery bias)
for 6c45pi, the problem is that the whole thing will give near 200mA (my trannie is 200 mA and I have to buy another choke (mine is 150 mA)
I will probably buy a new tranny anyway in near future if i want to try one day a DC design as mine has to low voltage.
Can someone give me a simple explanation of how to get a fixed bias from a tranny bias tap (my hammond has 50v) ?
In fact i had already tried again a PP cap first for better sound (so 10uF again)
The speed has remained the same, so it has to be the rising capacitance line that explains it
original psu : 10uF - choke - 40uF - resistor - 40uF - B+
now : 10uF - choke - 80uF(40+40) - resistor -100uF - B+
happy christmas to all (it is still 3 pm in france right now)
eric
mahleriana said:
Yes, you can just replace the cathode with the LED and keep others as they are. 6SN7 can take about 500V on the plate so no worries.
Don't worry, your tranny won't melt down instantly, you can try with the existing power trans, or get an isolation transformer to make a new PSU to test things out.Ditch the choke for the time being, replace it with a resistor equal to the DCR of the choke will save u lots of hassle while experimenting.
mahleriana said:
Not a trivia question😉 , google for any fix bias circuit and you will see it.
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