tube rolling with MC 10L
I am new to this thread but have a couple of questions. Appreciate if you folks can share your experience with the MC10L.
I have the new production that comes with the external bias adjust, etc.
Q1. of the 4- 6N1s that sit at the front, which two's are the SDRP pre-amp buffer ?
Q2. I have seen postings that rolling the 6N1 with 6922 gives 'better' sound, wonder if anyone has tried this out - your take on the sound ?
Q3. This is a more interesting question. Looks like the amp can take on KT88 with a re-bias (max -55V with Mc 10L versus max -70 with MC -100B of bias voltage). The KT88 will run have to run 'cooler' on th MC10L. Experience and thoughts on this ?
I am new to this thread but have a couple of questions. Appreciate if you folks can share your experience with the MC10L.
I have the new production that comes with the external bias adjust, etc.
Q1. of the 4- 6N1s that sit at the front, which two's are the SDRP pre-amp buffer ?
Q2. I have seen postings that rolling the 6N1 with 6922 gives 'better' sound, wonder if anyone has tried this out - your take on the sound ?
Q3. This is a more interesting question. Looks like the amp can take on KT88 with a re-bias (max -55V with Mc 10L versus max -70 with MC -100B of bias voltage). The KT88 will run have to run 'cooler' on th MC10L. Experience and thoughts on this ?
[ Q1. of the 4- 6N1s that sit at the front, which two's are the SDRP pre-amp buffer ? ]
They are V1 and V4 as shown by yellow arrows on attached photo.
[ Q2. I have seen postings that rolling the 6N1 with 6922 gives 'better' sound, wonder if anyone has tried this out - your take on the sound ? ]
Generally the 6N1 can replace a 6922 if the extra heater current can be supplied (a 6N1 draws 600mA instead of 300mA for the 6922) but to do the reverse can be risky in some cases as the anode voltage and dissipation is higher for the 6N1.
I have used Svetlana 6N1 Golds with very satisfying results.
[ Q3. This is a more interesting question. Looks like the amp can take on KT88 with a re-bias (max -55V with Mc 10L versus max -70 with MC -100B of bias voltage). The KT88 will run have to run 'cooler' on th MC10L. Experience and thoughts on this ? ]
The amp will only supply the power it was designed to give, fitting larger valves will not mean extra power without applying more stress to the power supply. The mains transformer already runs quite hot and demanding more may cause this component to fail.
If you want a fatter bottle for looks you could try the 6CA7, it has similar characteristics to the EL34 but is chunkier.
You also must consider the fact that the output transformers are optimised (we hope) to match the characteristics of the EL34 or its clones like the 6CA7.
They are V1 and V4 as shown by yellow arrows on attached photo.
[ Q2. I have seen postings that rolling the 6N1 with 6922 gives 'better' sound, wonder if anyone has tried this out - your take on the sound ? ]
Generally the 6N1 can replace a 6922 if the extra heater current can be supplied (a 6N1 draws 600mA instead of 300mA for the 6922) but to do the reverse can be risky in some cases as the anode voltage and dissipation is higher for the 6N1.
I have used Svetlana 6N1 Golds with very satisfying results.
[ Q3. This is a more interesting question. Looks like the amp can take on KT88 with a re-bias (max -55V with Mc 10L versus max -70 with MC -100B of bias voltage). The KT88 will run have to run 'cooler' on th MC10L. Experience and thoughts on this ? ]
The amp will only supply the power it was designed to give, fitting larger valves will not mean extra power without applying more stress to the power supply. The mains transformer already runs quite hot and demanding more may cause this component to fail.
If you want a fatter bottle for looks you could try the 6CA7, it has similar characteristics to the EL34 but is chunkier.
You also must consider the fact that the output transformers are optimised (we hope) to match the characteristics of the EL34 or its clones like the 6CA7.
Attachments
Thanks Les;
The thinking of using the kT88 on the MC-10L is to try out the `sound`of it vs EL34. As mentioned in my previous post, I am a newbie to tube amp. I have been using transistorized amps for years and I bought the yaqin MC-10L some 9 months ago. When I first hooked it up, I was blown away by the sound stage of the MC-10L - never realized that there is such a BIG difference between transistorized vs. tube amp.
I bought the MC-10L `cos of its low price and since, I have been reading into the different types of tubes. their characteristics, etc. and see what tube types that I can `roll`
with the MC-10L to check out the sound. The KT88 is just a thought, more pricey than EL34. Will likely try the 6CA7 per your suggestion at some later date.
Just one more curious Q on the 6922 tube.
Since the 6N1 draws about 600ma of current whereas the 6922 draws about 350, does it not mean that the 6922 will impose less load on the 6.3 PS ?
What puzzles me is, it appears that the 6.3V secondary supply all the heating elements (El34 and 6N1) and the heating elements are all connected in parallel. Does it not mean that when replacing the 6N1 with a 6922, the 6922 will draw less current ?
Tks for the picture attachment.
Al.
The thinking of using the kT88 on the MC-10L is to try out the `sound`of it vs EL34. As mentioned in my previous post, I am a newbie to tube amp. I have been using transistorized amps for years and I bought the yaqin MC-10L some 9 months ago. When I first hooked it up, I was blown away by the sound stage of the MC-10L - never realized that there is such a BIG difference between transistorized vs. tube amp.
I bought the MC-10L `cos of its low price and since, I have been reading into the different types of tubes. their characteristics, etc. and see what tube types that I can `roll`
with the MC-10L to check out the sound. The KT88 is just a thought, more pricey than EL34. Will likely try the 6CA7 per your suggestion at some later date.Just one more curious Q on the 6922 tube.
Since the 6N1 draws about 600ma of current whereas the 6922 draws about 350, does it not mean that the 6922 will impose less load on the 6.3 PS ?
What puzzles me is, it appears that the 6.3V secondary supply all the heating elements (El34 and 6N1) and the heating elements are all connected in parallel. Does it not mean that when replacing the 6N1 with a 6922, the 6922 will draw less current ?
Tks for the picture attachment.
Al.
Hi Al
Yes the 6922 will impose less demand on the heater line but personally I would be very cautious of the other supplies around these preamp valves. Attached is a redraw I made of the left channel with measured voltages. There is 300V Anode voltage on one stage and the cathode sits pretty high too, I never had the courage to try a 6922 in case of flash-over. Scary!
I did find the original Chinese 6N1's very sharp at the high end and they produced a lot of sibilance, putting in the Svetlana Golds was quite noticeable but I suppose it all comes down to ones preference in the end. I did buy a cheaper set of Svetlana 6N1s, they had Black markings. I was never happy with them and finished up putting back the 2 year old Golds. I suppose I shall have to save some pennies up and invest in a new set of those, cannot explain the difference, just more air? sound stage? stereo presence? whatever, they just sound better.
Les
Yes the 6922 will impose less demand on the heater line but personally I would be very cautious of the other supplies around these preamp valves. Attached is a redraw I made of the left channel with measured voltages. There is 300V Anode voltage on one stage and the cathode sits pretty high too, I never had the courage to try a 6922 in case of flash-over. Scary!
I did find the original Chinese 6N1's very sharp at the high end and they produced a lot of sibilance, putting in the Svetlana Golds was quite noticeable but I suppose it all comes down to ones preference in the end. I did buy a cheaper set of Svetlana 6N1s, they had Black markings. I was never happy with them and finished up putting back the 2 year old Golds. I suppose I shall have to save some pennies up and invest in a new set of those, cannot explain the difference, just more air? sound stage? stereo presence? whatever, they just sound better.
Les
Attachments
Tks again Les.
Your circuit is the most detailed and nicely drawn one that I have come across to date - really appreciate it.
I read from a site somewhere some two months back that a fellow has put in the RCA 6922 and it does work, I would not try it until I am very very sure though
I did search the web for the Svetlana 6N1 gold but did not see any. I presume they must be costly? Do you know of any source that are N. America located? I am very reluctant to order from the far east since I heard that there are lots of clone tubes out there? Since I do not have a tester (like the nice one that you've built), very reluctant to put in anything from that far of the world !
Need to tap on your experience again, is there a quick way to 'test' a tube using a digital multimeter to ensure at least nothing is 'shorted' prior to putting them into the amp ? Similar to measuring and comparing the relative resistance of a 3 legged transistor ?
Tks again for helping out.
Al
Your circuit is the most detailed and nicely drawn one that I have come across to date - really appreciate it.
I read from a site somewhere some two months back that a fellow has put in the RCA 6922 and it does work, I would not try it until I am very very sure though
I did search the web for the Svetlana 6N1 gold but did not see any. I presume they must be costly? Do you know of any source that are N. America located? I am very reluctant to order from the far east since I heard that there are lots of clone tubes out there? Since I do not have a tester (like the nice one that you've built), very reluctant to put in anything from that far of the world !
Need to tap on your experience again, is there a quick way to 'test' a tube using a digital multimeter to ensure at least nothing is 'shorted' prior to putting them into the amp ? Similar to measuring and comparing the relative resistance of a 3 legged transistor ?
Tks again for helping out.
Al
Hi Al, it looks like my local supplier has run out of the golds but has these on offer-
http://www.watfordvalves.com/product_detail.asp?id=1479
Not heard them myself so cannot give any guarantees.
More about the problems of a 6N1/6922 change in this thread-
http://www.diyaudio.com/forums/showthread.php?threadid=111210
You could check out the individual electrodes for short circuit using a multimeter but a better check would be with a higher voltage such as a 250V insulation tester.
Looking at the valve base with the gap in the pins at the bottom, the pins go clockwise 1 to 9.
Check out a low reading between pins 4 & 5 to prove the heater has continuity.
Check out insulation between pin 1 to pins 2,3,4,6.7.8 & 9.
Then Pin 2 to pins 3,4,6.7.8 & 9.
Then Pin 3 to pins 4,6.7.8 & 9.
And so on to finish up testing between the last two pins 8 & 9.
I don't normally bother myself, maybe I put too much faith in the valves quality and manufacturers testing, but if I had a dedicated valve tester I probably would give them a more detailed check.
Cheers
Les
http://www.watfordvalves.com/product_detail.asp?id=1479
Not heard them myself so cannot give any guarantees.
More about the problems of a 6N1/6922 change in this thread-
http://www.diyaudio.com/forums/showthread.php?threadid=111210
You could check out the individual electrodes for short circuit using a multimeter but a better check would be with a higher voltage such as a 250V insulation tester.
Looking at the valve base with the gap in the pins at the bottom, the pins go clockwise 1 to 9.
Check out a low reading between pins 4 & 5 to prove the heater has continuity.
Check out insulation between pin 1 to pins 2,3,4,6.7.8 & 9.
Then Pin 2 to pins 3,4,6.7.8 & 9.
Then Pin 3 to pins 4,6.7.8 & 9.
And so on to finish up testing between the last two pins 8 & 9.
I don't normally bother myself, maybe I put too much faith in the valves quality and manufacturers testing, but if I had a dedicated valve tester I probably would give them a more detailed check.
Cheers
Les
Attachments
Thanks Les, for your input.
Just received the Russian 6N1P-EV and have replaced the stock 6J1 of the pre-amp tubes (only the pre-amp) with them. Notice the sound stage changes immediately with the mids (especially vocals) being brought more forward.
I am very happy with the sound of the MC-10L so far.
I did look at the circuit carefully posted by you. Now I do understand what you are saying - the plate voltage design for the 6J1 of this amp will be on the high side of the 6922. Plugging in a 6922 will result in it operating at a plate voltage very close to the spec max or even slightly higher than the spec max.
I do see the logic now -
6J1 replacing a pre-amp circuit designed for 6922 is ok but not the other way - it does not means that 6J1 and 6922 are interchangeable both ways (Some web postings suggested that if 6J1 can replace 6922, therefore 6922 can also replace 6J1, which is not a 'safe' assumption).
Tks again.
Merry X'mas.
Al
Just received the Russian 6N1P-EV and have replaced the stock 6J1 of the pre-amp tubes (only the pre-amp) with them. Notice the sound stage changes immediately with the mids (especially vocals) being brought more forward.
I am very happy with the sound of the MC-10L so far.
I did look at the circuit carefully posted by you. Now I do understand what you are saying - the plate voltage design for the 6J1 of this amp will be on the high side of the 6922. Plugging in a 6922 will result in it operating at a plate voltage very close to the spec max or even slightly higher than the spec max.
I do see the logic now -
6J1 replacing a pre-amp circuit designed for 6922 is ok but not the other way - it does not means that 6J1 and 6922 are interchangeable both ways (Some web postings suggested that if 6J1 can replace 6922, therefore 6922 can also replace 6J1, which is not a 'safe' assumption).
Tks again.
Merry X'mas.
Al
Thanks for an awesome thread on the MC-10L. Got my own when I visited Hong Kong on my last trip. A little overweight on the luggage when travelling home, but it was worth the trouble (especially since Thai Airways did not charge me extra for the 35+ kilos my bag weighted...)
THe overall impression is positive so far: Nice sound stage, that I hope to improve when the stock el34:s and 6n1:s are changed to their Russian counterparts, stunning female vocal mids (Laura Fygi on the "Bewitched" album, recommended!), and very quiet operation, no 50Hz hum coming out. Main tranny gets warm, but hey, for the 2400 HKD I paid, you do not get half of the Bill of Materials to build your own here in Sweden....
Any recommendations on audio caps (the 4 p. of 100 nF between the differential stage and the EL34:s). What should I use instead of the stock ones?
THe overall impression is positive so far: Nice sound stage, that I hope to improve when the stock el34:s and 6n1:s are changed to their Russian counterparts, stunning female vocal mids (Laura Fygi on the "Bewitched" album, recommended!), and very quiet operation, no 50Hz hum coming out. Main tranny gets warm, but hey, for the 2400 HKD I paid, you do not get half of the Bill of Materials to build your own here in Sweden....
Any recommendations on audio caps (the 4 p. of 100 nF between the differential stage and the EL34:s). What should I use instead of the stock ones?
Hi Ariston;
I have not tried upgrading the 100p coupling yet - I would use the ones made by Auricaps - they are pretty $$$ though, and I am not sure if it would make a significant improvement !
I would suggest rolling the tubes first. You may like the result without the capacitor mod.
Do post your experience if you do try out the capacitor mod.
Hope someone with the capacitor mod would respond to this thread javascript:smilie('')
Al
I have not tried upgrading the 100p coupling yet - I would use the ones made by Auricaps - they are pretty $$$ though, and I am not sure if it would make a significant improvement !
I would suggest rolling the tubes first. You may like the result without the capacitor mod.
Do post your experience if you do try out the capacitor mod.
Hope someone with the capacitor mod would respond to this thread javascript:smilie('
')Al
I have been watching with great interest the Yaqin 5881 thread:-
http://www.diyaudio.com/forums/showthread.php?s=&threadid=97618
The circuitry in places is virtually identical and the improvements/mods detailed are very tempting to try. For example, take doing away with the 30k long tailed pair resistor. Would a simple circuit as attached be capable of replacing the resistor with any advantage?
Also it is stated that if this is done the two plate resistors, currently 47k and 51k should both be made 47k?
In fact it had already been suggested to me that one of these resistors, possibly the 51k, should be made variable e.g. 39k with a series 22k preset. This would allow the outputs feeding the EL34's to be equalised.
Noted also is the change of B+ resistor from 5k1 to 12k, that seems a bit of a large jump to me and though it might lower the gain of the pre-amp, would it improve the sound quality?
Finally the feedback components (5k1 with 100pF cap), the cap is indeed a ceramic one in the MC10L, would a mica make any difference here? Would lowering the gain of the amp by changing these components to 1k2 + 500pF be an advantage?
I must say I am tempted to disconnect the OPT wires from the screens of the EL34's and connecting the suggested 47 Ohm resistor between plate and screen to give a triode configuration, just to find out how it sounds.
I realise that I have written more questions than answers, I have so many other projects going at the moment that it may be some time before I try any of these changes for myself, I was just wondering if someone else had seen these mods and tried them already. I hope to attach the pdf of the 2SC3468, interestingly it is available with a high gain suffix F which might be better. The 166 Ohm resistor is just a rough estimate, I would trim this to give the required current which, going by the voltages currently measured, I would reckon on being around 4mA.
I have put some of my circuit redraws on
http://homepage.ntlworld.com/lez/YAQIN MC10/
I will shortly add some more photos showing voltages around the circuit.
Regards
Les
PS For some strange reason I cannot upload the jpeg and pdf even though they are very small in size. I will put them on my homepage too.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=97618
The circuitry in places is virtually identical and the improvements/mods detailed are very tempting to try. For example, take doing away with the 30k long tailed pair resistor. Would a simple circuit as attached be capable of replacing the resistor with any advantage?
Also it is stated that if this is done the two plate resistors, currently 47k and 51k should both be made 47k?
In fact it had already been suggested to me that one of these resistors, possibly the 51k, should be made variable e.g. 39k with a series 22k preset. This would allow the outputs feeding the EL34's to be equalised.
Noted also is the change of B+ resistor from 5k1 to 12k, that seems a bit of a large jump to me and though it might lower the gain of the pre-amp, would it improve the sound quality?
Finally the feedback components (5k1 with 100pF cap), the cap is indeed a ceramic one in the MC10L, would a mica make any difference here? Would lowering the gain of the amp by changing these components to 1k2 + 500pF be an advantage?
I must say I am tempted to disconnect the OPT wires from the screens of the EL34's and connecting the suggested 47 Ohm resistor between plate and screen to give a triode configuration, just to find out how it sounds.
I realise that I have written more questions than answers, I have so many other projects going at the moment that it may be some time before I try any of these changes for myself, I was just wondering if someone else had seen these mods and tried them already. I hope to attach the pdf of the 2SC3468, interestingly it is available with a high gain suffix F which might be better. The 166 Ohm resistor is just a rough estimate, I would trim this to give the required current which, going by the voltages currently measured, I would reckon on being around 4mA.
I have put some of my circuit redraws on
http://homepage.ntlworld.com/lez/YAQIN MC10/
I will shortly add some more photos showing voltages around the circuit.
Regards
Les
PS For some strange reason I cannot upload the jpeg and pdf even though they are very small in size. I will put them on my homepage too.
Well it has been some months of trial but I can now report on my own findings regarding replacement of 6N1's with ECC85's. I fitted ECC85 valves in the front end of each channel and my initial feelings were that the top end was just slightly lifted at the expense of the lower middle range. I did not need this extra top end as the Tannoy speakers here provide enough and I found it difficult to decide if the overall effect was really an improvement or a degradation. Now my ears are pretty shot now as I am over 60 but one day a young friend of mine in his 20's came to listen to the amp. When he entered the room he put his hands to his ears and said "Wow!, There is a high pitched whistle like a cat scarer in your house". It was coming from the left hand channel of the amp so I quickly refitted the 6N1's and everything was fine. I also noticed that the amp was now giving me the fuller sound stage that it of course had before I made the changes. So from my point of view, for what it is worth, I would not recommend spending $$ to fit ECC85's to your Yaqin, just treat it to some Svetlana 6N1 Golds, if you can find them. 
Still plucking up courage to fit multi-turn pre-sets for bias adjustment and constant current circuits in the long tailed pairs
Still plucking up courage to fit multi-turn pre-sets for bias adjustment and constant current circuits in the long tailed pairs
KT88
I bought this amp on e-bay 9 months it took forever to arrive, i payed about $500+ with shipping. I was really happy with the sound. after 3 months the original tubes went up in smoke. it has been sitting on the shelf unused over the winter. I never checked the bias after i received it so that could be the reason why it broke. I finally ordered some new Tung-SolEL34B from tubedepot based on their review, i have had them in the amp for about 2 weeks now but i beleive the amp sounded better before, with the new tubes i run 40mA bias maybe the old tubes was biases higher, and that could be why the amp sounded better, and also why the tubes died young. Either way i had some Penta KT88's and Golden Aero KT88 laying around. The KT88's would not fit in my amp with the top cover on, so i removed the top cover and inserted one tube one tube and turned it on, then i whached the bias current. after inserting all my tubes i found that some tubes, allows me to run a 50mA bias and one other is 70mA for the pentode tubes the golden aero are higher yet. so i paired them up, and on one side i am running 60mA for bias for both tubes and on the other side i was running 70mA for bias for both tubes. I am not comfortable running at that high bias otherwise i would bias the same for both channels. That put's this amp in High Class AB almost class A. The maximum negative bias voltage is -54V it would be nice with another -10/20V at least so you could Run KT88's without worrying. I had this done at 9am this morning and i have to say the KT88's are remarkably better that the EL34 Tung Sol. I am reluctant to put the EL34's back in however after listening to music for 3 hours now( i just could not pull away) i feel that the KT88's life will be very short unless i modify the bias voltage. Is it possible to put an inductor in series with the exsisitng transformer to increase the voltage say10-15volts or should i just get a separate transformer Sec50V 50VA that should be 70V after the rectifier. OR a 3rd option to get a 15Volt 50VA step up transformer after the exsisting one. Any advice in this regard would be apreciated. I bought this amp with the EL34 tubes because from listening to other amps with EL34 tubes i really liked them, now i which i would have just bought their KT88 amp from the get go.
I bought this amp on e-bay 9 months it took forever to arrive, i payed about $500+ with shipping. I was really happy with the sound. after 3 months the original tubes went up in smoke. it has been sitting on the shelf unused over the winter. I never checked the bias after i received it so that could be the reason why it broke. I finally ordered some new Tung-SolEL34B from tubedepot based on their review, i have had them in the amp for about 2 weeks now but i beleive the amp sounded better before, with the new tubes i run 40mA bias maybe the old tubes was biases higher, and that could be why the amp sounded better, and also why the tubes died young. Either way i had some Penta KT88's and Golden Aero KT88 laying around. The KT88's would not fit in my amp with the top cover on, so i removed the top cover and inserted one tube one tube and turned it on, then i whached the bias current. after inserting all my tubes i found that some tubes, allows me to run a 50mA bias and one other is 70mA for the pentode tubes the golden aero are higher yet. so i paired them up, and on one side i am running 60mA for bias for both tubes and on the other side i was running 70mA for bias for both tubes. I am not comfortable running at that high bias otherwise i would bias the same for both channels. That put's this amp in High Class AB almost class A. The maximum negative bias voltage is -54V it would be nice with another -10/20V at least so you could Run KT88's without worrying. I had this done at 9am this morning and i have to say the KT88's are remarkably better that the EL34 Tung Sol. I am reluctant to put the EL34's back in however after listening to music for 3 hours now( i just could not pull away) i feel that the KT88's life will be very short unless i modify the bias voltage. Is it possible to put an inductor in series with the exsisitng transformer to increase the voltage say10-15volts or should i just get a separate transformer Sec50V 50VA that should be 70V after the rectifier. OR a 3rd option to get a 15Volt 50VA step up transformer after the exsisting one. Any advice in this regard would be apreciated. I bought this amp with the EL34 tubes because from listening to other amps with EL34 tubes i really liked them, now i which i would have just bought their KT88 amp from the get go.
Just wading thru' this thread.
The suggested CCS replacement for the 30K tail resistor should give improvements although a better current source would give better improvements again. If fitting the current source in lieu' of the 30K resistor then certainly the anode load resistors should be made equal, that is use 47K for both.
Also the "Ring of Two" current source can be unstable, it usually isn't but it is a good idea to add a 100 Ohm resistor in series with the TR1 base connection just to make sure.
Way up on page 1 it was suggested voltage share resistors should be added across C3 and C4. A 100K 2W resistor across each cap will suit. That is almost essential.
The 127V on the cathodes of V2 worries me a bit from a heater to cathode insulation and leakage point of view. If anyone wants to have a play the following mod may give surprising results. The heater supply will be balanced either by tying a heater winding centre tap to 0V or if the winding has no centre tap then there will (or should) be a pair of 100 Ohm (or maybe 47 Ohm) resistors connected across the heater winding with the centre point connected to 0V. Find this 0V heater reference point.
Generate a +60V - ish supply by using a 330K + 56K from HV to 0V, 56K on the 0V side. Add a 10uF/100V electrolytic across the 56K. remove that heater balance 0V connection and wire it the +60V point instead. That is we are "floating" the heaters on top of the +60V supply (anywhere between +50 and +80 Volts is fine). You maybe surprised at the subtle improvements in sound and may well get a reduction in any hum as well. I have had good results with this mod on a number of amps.
Cheers,
Ian
The suggested CCS replacement for the 30K tail resistor should give improvements although a better current source would give better improvements again. If fitting the current source in lieu' of the 30K resistor then certainly the anode load resistors should be made equal, that is use 47K for both.
Also the "Ring of Two" current source can be unstable, it usually isn't but it is a good idea to add a 100 Ohm resistor in series with the TR1 base connection just to make sure.
Way up on page 1 it was suggested voltage share resistors should be added across C3 and C4. A 100K 2W resistor across each cap will suit. That is almost essential.
The 127V on the cathodes of V2 worries me a bit from a heater to cathode insulation and leakage point of view. If anyone wants to have a play the following mod may give surprising results. The heater supply will be balanced either by tying a heater winding centre tap to 0V or if the winding has no centre tap then there will (or should) be a pair of 100 Ohm (or maybe 47 Ohm) resistors connected across the heater winding with the centre point connected to 0V. Find this 0V heater reference point.
Generate a +60V - ish supply by using a 330K + 56K from HV to 0V, 56K on the 0V side. Add a 10uF/100V electrolytic across the 56K. remove that heater balance 0V connection and wire it the +60V point instead. That is we are "floating" the heaters on top of the +60V supply (anywhere between +50 and +80 Volts is fine). You maybe surprised at the subtle improvements in sound and may well get a reduction in any hum as well. I have had good results with this mod on a number of amps.
Cheers,
Ian
Les (HI-Q).
Have you tried the Triode mod yet?
I'm wondering if this amp will play nice in that configuration?
Edit:Oops!
Didn't notice how old this thread is
I am willing to be a part to help rebirth this thread, since we are could be discussing the new MC 10L with the EL34B and 6H1N tubes.
The reviews has been decent of this newer version.
Please correct me if I am wrong as I am a newby.
Any comments??? Anyone???
Some of that happening here: http://www.diyaudio.com/forums/tubes-valves/173529-looking-tube-amp.html
dave
Yaqin MC-10L input caps
Hello all, got my 10L, very nice indeed, though mine seems to be an earlier one as no caps sticking out of the lid LOL.
Never done much modding on amps before except for changing input caps, big benefits to be had normally. Is there any scope for doing the same to this amp ?
thanks
Hello all, got my 10L, very nice indeed, though mine seems to be an earlier one as no caps sticking out of the lid LOL.
Never done much modding on amps before except for changing input caps, big benefits to be had normally. Is there any scope for doing the same to this amp ?
thanks
Nah! You have a newer version, the older ones had the caps sticking out. You will also have the bias points and adjusters easily available, us folks with the older units have to remove the lid each time. Read the posts and you will find what things are best to try, most improvements can be had by simple tube rolling but if you are of a nervous disposition then stick to replacement EL34's or 6CA7's in the output stages. Some folks have had success using other valve types but due to maximum voltage ratings being exceeded I would not personally recommend it. Likewise many, including myself, have tried different input/inverter valves like ECC85 but I finished up with some sweet sounding 6N1's which I am very happy with. My amp is fast approaching its 4th year now, heavily run every day and yet no major problems so far.