yeah i know what version you have. Made by same company. My 6,3V measures 6,29 vs 6,27v. 230 i have not measured directly of though.
Are you not using yours?
I wouldn't be overly concerned about the heating of the transformer, I have plenty of transformers which heat up just as much. However, as I said before if it is poor quality and at the point of overload it will be more magnetically noisy which is an issue. Your choke will clean up a lot of the crud generated by a transformer on the edge getting into your supply voltage.
Spend sometime finding an arrangement of compenents which is quietest and tidy up your wiring. I like top mounted components as it certainly gives more case space, but your power transformer would then need a good screening can on top - otherwise it will make the build look rubbish. As you have discovered this is not an easy thing to find.
If I were you - I would try to keep everything inside the case and use the hunt for a quiet build as a learning experience, you will understand a huge amount more at the end by getting it right. Undoubtedly this will be the first of many projects and you will thank yourself for the time spent learning the basics.
Shoog
Spend sometime finding an arrangement of compenents which is quietest and tidy up your wiring. I like top mounted components as it certainly gives more case space, but your power transformer would then need a good screening can on top - otherwise it will make the build look rubbish. As you have discovered this is not an easy thing to find.
If I were you - I would try to keep everything inside the case and use the hunt for a quiet build as a learning experience, you will understand a huge amount more at the end by getting it right. Undoubtedly this will be the first of many projects and you will thank yourself for the time spent learning the basics.
Shoog
It had been stashed in a box waiting for me to finish other projects, but this thread got me curious enough to retrieve it.
I'm surprised at how decent it sounds directly into headphones, even in its stock form. I'll have to hook it up to a scope later and play around.
So I guess I am going to be using it now 🙂
Check these guys out I have ordered many Antek xformers and they are very good quality.
I also really like Edcor but they take forever to ship. Antek usually has pretty good in stock items.
I also really like Edcor but they take forever to ship. Antek usually has pretty good in stock items.
Hehe well done. If you build the MKIIIIIII i have now 😀 please scope it and share here. Maybe there is more to improve? I certainly think sound is stellar right now. Compared to original, it's night n day in my ears.
Try also the Russian tubes if you don't already have some nos tubes. They are a BIG improvement from the chinese.
If you need cheap, good filmcaps check it-tronics from Germany. I bought all mine there, Arcotronics MKP R75/R76
5X MKP Kondensator Radial 10uF 250VDC RM37 5 RoHS R75IW5100AA30J | eBay
They do a lot in this preamp...
That one is not with centertap right?
I've seen this brand before ... looks good.
Let's see
One for transformer and one for choke. Smallest i could find in "metal" not aluminium. What do you think? I think thy would fit on top of chassie next to each other too. But pretty expensive.
1 DIY Black 85 85 100mm Vintage Triod Metal Transformer Protect Cover Enclosure | eBay
Or this
http://www.ebay.com/itm/N7-Black-Rough-Surface-Metal-Transformer-Case-Cover-88Lx102Wx70H-/221300026202?pt=Vintage_Electronics_R2&hash=item3386826b5a
Last edited:
Maybe you connected the 0.7A secondary, instead of 1.7A, for heaters and that is the cause of the large voltage drop(?)
BTW, you can also change only the core by decent quality GOSS.
A new trafo don't guarantee low heating.
Transformer heating is only one side of the problem, poor quality core saturates and inrush current affects heaters supply, unless you use regulated DC, or a separated trafo for heaters. IMHO.
I do have a stash of Russian 6N3Ps and GE 5670s to try, and a couple of different 6X4s if I swap a few pins around.
Anyway definitely going to scope at least some of the modifications you made. Though I think mine might be destined to become a headphone amp now, so it may diverge at some point.
Thanks for the recommendations on the film caps!
List of changes so far plus other things (for anybody interested)
1. Input caps removed. -Big improvement especially in bass.
2. Grid-stopper instead of input cap =330ohm/2W Kiwame
3. Tubes Russian 6n3p-eb (matched par/sections) Rectifier russian 6x4-R
4. Output caps replaced with Audyn Cap PLUS 1,5uF bypassed with 6.8nF ERO kp1830. These are good but i wanna try RIKE S-CAP 2,2uF 🙂
5. All 4 pcs of 10K resistors before caps (older versions have 100k) removed and 4 pcs 1M (i'm gonna try 100K too) as leakresistor on input output.
6. Cathode resistors adjusted to 330ohm (Kiwame here too) (4pcs) to give about 5mA of currentdraw per tube.
7. AC on heaters, mostly because i had low voltage (4,4V something with this transformer)
8. Voltage divider. AC tied to 2x330ohm to ground via 300K/100K from B+ (see pic earlier in this thread) Helpt with almost all hum.
9. Choke: 10H /270ohm Triad CX7
10. 2pcs 47uF BC/Vishay serie 059 caps in PSU (some 68uF BC serie KO151 are on the way to try a higher value in PSU3) + 8x10uF Arcotronics MKP R75 250V.
11. Fused inlet filter "Bulgin" from a UK seller with MKP caps inside (NOS). Little expensive maybe (16e) but worth it.
12. Pot is Alps RK27 /50K - Maybe 100K is even better. Gain is high... 9 o'clock volume is high...
13. Signalcables are Neotech OCC and Furutech u2.1 (great improvement)
14. Rca connectors: CMC 816 - very high quality.
15. External powercable is ÖLFLEX 110CY. - Nice cable for price compared to High-End *snakes* 😉
1. Input caps removed. -Big improvement especially in bass.
2. Grid-stopper instead of input cap =330ohm/2W Kiwame
3. Tubes Russian 6n3p-eb (matched par/sections) Rectifier russian 6x4-R
4. Output caps replaced with Audyn Cap PLUS 1,5uF bypassed with 6.8nF ERO kp1830. These are good but i wanna try RIKE S-CAP 2,2uF 🙂
5. All 4 pcs of 10K resistors before caps (older versions have 100k) removed and 4 pcs 1M (i'm gonna try 100K too) as leakresistor on input output.
6. Cathode resistors adjusted to 330ohm (Kiwame here too) (4pcs) to give about 5mA of currentdraw per tube.
7. AC on heaters, mostly because i had low voltage (4,4V something with this transformer)
8. Voltage divider. AC tied to 2x330ohm to ground via 300K/100K from B+ (see pic earlier in this thread) Helpt with almost all hum.
9. Choke: 10H /270ohm Triad CX7
10. 2pcs 47uF BC/Vishay serie 059 caps in PSU (some 68uF BC serie KO151 are on the way to try a higher value in PSU3) + 8x10uF Arcotronics MKP R75 250V.
11. Fused inlet filter "Bulgin" from a UK seller with MKP caps inside (NOS). Little expensive maybe (16e) but worth it.
12. Pot is Alps RK27 /50K - Maybe 100K is even better. Gain is high... 9 o'clock volume is high...
13. Signalcables are Neotech OCC and Furutech u2.1 (great improvement)
14. Rca connectors: CMC 816 - very high quality.
15. External powercable is ÖLFLEX 110CY. - Nice cable for price compared to High-End *snakes* 😉
Hi,
I think the max. value of the cap prior to the filter choke is 10 microF.
No bleeder resistor drawn in the PSU drawing.
Also, there's little point in putting a 2wR as a gridstopper, 1/4W is ample already. 100R should do the trick.
There should also be one at top tube of the stack.
Re the pot, 100K to even 1M should work. The higher values will cause a mild roll off of the top frequencies.
I find almost all pots to add a "plastic" kind of tone to the sound. Stepped attenuators are far more transparent.
You could also try to lower the output resistor to 100K.
Just as a test, you may want to try to decouple the lower tube's cathode R with say a 47 micro F MKP cap, this should improve PSRR and may well shed the last bit of hum (I hope).
Ciao, 😉
I think the max. value of the cap prior to the filter choke is 10 microF.
No bleeder resistor drawn in the PSU drawing.
Also, there's little point in putting a 2wR as a gridstopper, 1/4W is ample already. 100R should do the trick.
There should also be one at top tube of the stack.
Re the pot, 100K to even 1M should work. The higher values will cause a mild roll off of the top frequencies.
I find almost all pots to add a "plastic" kind of tone to the sound. Stepped attenuators are far more transparent.
You could also try to lower the output resistor to 100K.
Just as a test, you may want to try to decouple the lower tube's cathode R with say a 47 micro F MKP cap, this should improve PSRR and may well shed the last bit of hum (I hope).
Ciao, 😉
Last edited:
Thanks for your input... i was worried this was wrong, first time i draw a schematic. But i was thinking, if i did something wrong guys here would probably say something =)
-Yes see that the i forgot the bleeder.
-I only had 2W in stock.. or hificollective only have 2w/5w kiwames.
-oopsss... hmmm i see On top of the stack. When i took away the input caps i soldered one per side where the cap once was... didn't think the tubes are actually two tubes in one. Have to fix that asap. Hope it doesn't hurt anything.
-Pots, yes i really want to have an stepped too. I heard how much a pot adds to overall sound (or take away) in my yaqin amp when i converted it to only amp from being a integrated from beginning so i totally agree.
- Lower output res to 100K? You mean the "last one" after the cap? Not the other one too?
-Ok cap, 47uf film. It doesn't need to be a high voltage one then cos i only read around 1.5V something here. I have 2 pcs 100uf MKT. Out of stock on 47 film.
Will try to fix up this schematic sometime 😡
I tried my best but still
EDIT: ohh about first filmcaps that are 40uf now.. yes Carl mentioned early in the thread that people usually put something like 1-10uF here.
To make rectifier life longer or?
Last edited:
Hi,
Yes, the one behind the output cap.
Fair enough....I usually don't put any anyway.😛
Re: the decoupling cap: even a low voltage tantalum would do for testing purposes.
Ciao, 😉
Yes, the one behind the output cap.
Fair enough....I usually don't put any anyway.😛
Re: the decoupling cap: even a low voltage tantalum would do for testing purposes.
Ciao, 😉
I have only 47 elco or 100 mkt =)
Is it possible to calculate the correct value here or? or 47uF is "correct"?
- Status
- Not open for further replies.