Hello folks. just wondering if it is OK to use MKP motor run caps of 60 or 80uF in place of the 100uf 375v/400v electrolytic caps. They seem to be a cheap source of large value MKP caps. If safe and OK will it be likely to improve sound quality? Reading from http://www.diyaudio.com/forums/tubes-valves/154415-100uf-motor-run-caps-3.html suggests that here is nothing to be gained sonically..... I am also thinking about converting from SS to Valve rectification and choke PS. I have a 5u4g tube and am fairly sure it's good for the job.??? Any advice before I dive in would be much appreciated. Thanks.
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I would avoid a valve rectifier unless you really, really want an additional glowing tube on the chassis.
Chokes, however, are fantastic, I've never done a high voltage PSU where it wasn't a wonderful benefit.
If you have the room for the MKP caps I can't imagine they will cause any problem.
My $0.02
Chokes, however, are fantastic, I've never done a high voltage PSU where it wasn't a wonderful benefit.
If you have the room for the MKP caps I can't imagine they will cause any problem.
My $0.02
sharkey22,
See post #1262 for the "Jessica" Amp.
I used a Tube rectifier into a choke input power supply with 60uF/900V polyproylene caps.
This was an earlier version of the 6SL7/6V6 BH, the source follower arrangement was different.
This "Jessica" amp has lovely relaxed "loping" pace but lacks a little attack compared to the SS rectifier versions. Great for JJ Cale style Blues, lacks a bit for "head banging" rock.
Cheers,
Ian
See post #1262 for the "Jessica" Amp.
I used a Tube rectifier into a choke input power supply with 60uF/900V polyproylene caps.
This was an earlier version of the 6SL7/6V6 BH, the source follower arrangement was different.
This "Jessica" amp has lovely relaxed "loping" pace but lacks a little attack compared to the SS rectifier versions. Great for JJ Cale style Blues, lacks a bit for "head banging" rock.
Cheers,
Ian
Thanks Ian. Mine will have SS and Choke. Ecc83 and NOS Russian 6p14p valves I am using your original ecc803s/el84 schematic. I am definitely looking for something with a bit of punch. What are your recommendations re feedback? I presume I could put a 20k pot in the f/b line and adjust to taste? Would it be easy enough to alter the schematic for el34/6sn7gt tubes as I have both.
Regards Ian.
Regards Ian.
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That's what I did on my build (original version with ECC803 and EL84, slightly different power supply).
IIRC, I used a 47k stereo pot wired as adjustable resistor in series with a 5 or 10k resistor (not entirely sure here, too lazy to open the amp now).
I have to say that there is actually a sweet spot in the feedback setting, so that I rarely change it. Sometimes I do (because the pot is there) as a sanity check but I usually end up at the same settings again at the end.
If I would build another one (and I definitely will at some point - great amp), I would use the pot only during construction with the intended speakers and then replace it for the final assembly by resistors of the same value.
Best,
Martin
OK - that chassis I have for the next build has a Tango Output Tranny with an Raa of 8K and 25 watt Rating.
It will be a 6SL7 + KT66.
The KT88 Output and 6BR7 pentode diffamp front end will have to wait for the one after that. I suggested 6BR7 because I already have them on my shelf,but EF86 or The ones Rogon suggests would work too.
I have been, and continue to be, swapped with repair/restoration work for other people so little design work is getting done.
Sporc - On the ECL86 version I rectified the heater winding to generate the -ve rail for the Diffamp Tail CCS. That worked without any troubles.
Cheers,
Ian
It will be a 6SL7 + KT66.
The KT88 Output and 6BR7 pentode diffamp front end will have to wait for the one after that. I suggested 6BR7 because I already have them on my shelf,but EF86 or The ones Rogon suggests would work too.
I have been, and continue to be, swapped with repair/restoration work for other people so little design work is getting done.
Sporc - On the ECL86 version I rectified the heater winding to generate the -ve rail for the Diffamp Tail CCS. That worked without any troubles.
Cheers,
Ian
@Sporc - No worries Refer Post #24 here:
http://www.diyaudio.com/forums/tubes-valves/53969-hey-planet_10-others-3.html
This was where the whole Baby Huey thing came from, that is, from a design from Yves M. That Amp is now with one of my sisters as her everyday HiFi Amp driving some Polk Audio Speakers and using a restored vintage Marantz Preamp.
Others - I just checked the prices for KT66 and have decided that build with the Tango Iron will be a 6SL7/6V6 repeat.
I have started pencil and paper design for a "Bruiser" Huey. Checking cost vs. performance trade offs for various options:
pair of KT88 (60W)
pair of EL34 (40 or 80W)
quad of EL84 or even 6 or 8 EL84s (20 , 30 or 40W respectively).
Looked at KT120 and KT150 prices and decided to not go there either.
I have pairs of Hammond Output Trannies in 4k3 Raa and 6K8 Raa in 60 watt rating so that will lead design a bit, I also have a pair of Hammond 1650T Raa 2K with 120W rating, maybe a quad of EL34 or KT88 - Don't hold your breath. I have 2 Git. Amps to finish first.
Cheers,
Ian
http://www.diyaudio.com/forums/tubes-valves/53969-hey-planet_10-others-3.html
This was where the whole Baby Huey thing came from, that is, from a design from Yves M. That Amp is now with one of my sisters as her everyday HiFi Amp driving some Polk Audio Speakers and using a restored vintage Marantz Preamp.
Others - I just checked the prices for KT66 and have decided that build with the Tango Iron will be a 6SL7/6V6 repeat.
I have started pencil and paper design for a "Bruiser" Huey. Checking cost vs. performance trade offs for various options:
pair of KT88 (60W)
pair of EL34 (40 or 80W)
quad of EL84 or even 6 or 8 EL84s (20 , 30 or 40W respectively).
Looked at KT120 and KT150 prices and decided to not go there either.
I have pairs of Hammond Output Trannies in 4k3 Raa and 6K8 Raa in 60 watt rating so that will lead design a bit, I also have a pair of Hammond 1650T Raa 2K with 120W rating, maybe a quad of EL34 or KT88 - Don't hold your breath. I have 2 Git. Amps to finish first.
Cheers,
Ian
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Hi Ian. I am looking forward to EL34/6sn7 version. I have a question re. power supply caps. When you advise connecting the negative side of the 100uF and poly caps directly to the output tube cathode circuit at 0v, do you literally mean solder the 100uF/poly caps directly (physically) to the emitters of the bc547's of the bias blocks? If so why is it so important not to have any distance ? Thanks. Ian.
Only the film caps need to be close. And they would be connected either to the emitter or the negativ terminals of the cathode bypass caps (probably easier).
The idea behind it: Wires are (low value) resistors, too. If you are aiming for low impedance of your power supply and therefore bypass the electrolytic caps with film caps (lower ESR), it does not make sense to add wire resistance to the low ESR of the film caps. Therefore, the film caps should be as close to the load as possible (between B+ tap of output transformer and negativ terminal of cathode bypass cap).
Since the electrolyticcaps have higher ESR anyway (actually also not that high for modern caps designed for switch-mode PS), resistance of a bit of wire does not matter that much.
Does that make sense?
Best,
Martin
PS: I assume the EL34 version would be a EL34/6SL7 version
The idea behind it: Wires are (low value) resistors, too. If you are aiming for low impedance of your power supply and therefore bypass the electrolytic caps with film caps (lower ESR), it does not make sense to add wire resistance to the low ESR of the film caps. Therefore, the film caps should be as close to the load as possible (between B+ tap of output transformer and negativ terminal of cathode bypass cap).
Since the electrolyticcaps have higher ESR anyway (actually also not that high for modern caps designed for switch-mode PS), resistance of a bit of wire does not matter that much.
Does that make sense?
Best,
Martin
PS: I assume the EL34 version would be a EL34/6SL7 version
Hi All, I'm next one who 'commited' Baby Huey EL84. I choose version with balanced input and no feedback. Tubes are 6n2p-ev as driver and 6p14p-ev as output. I also took driver ccs power supply from 12v lead acid battery. It plays for about 20 hours for now, so k75-10 coupled caps are no burned in yet, but I have to admit the sound is brilliant. It sounds very triodish but with more power. I've rebuild existing ecc83/el84pp so all irons and caps remains. The overall cost of this was really cheap and the effect is astonishing. Thank You Gingertube, You make my old amp really sing