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6V6 Parafeed with "Robin Hood" iron.

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Here is a design that I whipped up yesterday that uses the new "Robin Hood" output transformers that Mike has blessed us with. I will post the PSU later.
Cheers.
G

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Re: 6V6 Parafeed with "Robin Hood" iron. - eelind 00:19:06 08/28/04 (0)
Hello,
Just a little message to let you know that the 6V6 is on its way. All the components are here, and the chassis will arrive in a few days.Just a big changing in the PSU design.
Eric
Re: 6V6 Parafeed with "Robin Hood" iron. - eelind 02:14:50 06/14/04 (2)
Hello Gavin,
I've been talking about your design with a friend, and he suggested a way to avoid C3-R6-BCP16:
(5687 diectly coupled to the 6V6 grid )AND( B+ for the 6V6 at +475V) AND (Vk at 175V, which gives a value for R3 of 4375Ohm/ 15W)
What do you think of this?
I can e-mail you the modified design.
Eric
- Re: 6V6 Parafeed with "Robin Hood" iron. - G 20:00:41 06/23/04 (1)
  I'm sorry for not checking the forum lately. Please do send the schematic. I'm a little leery of putting 475 volts on the plate of a 6V6 though. Cheers.
  Gavin
  - Re: 6V6 Parafeed with "Robin Hood" iron. - eelind 22:51:05 06/23/04 (0)
    Hi Gavin,
    The work is in progress.I've ordered the parts from Mike, should arrive within 6 weeks. If you want , I can send you the modified design in your e-mail. Just be sure it won't be confused with any spam...And so you can correct it.
    So, We are working on this idea to put 475V as B+ on the 6V6. Should work, and so we can get rid of one cap, one choke , one res and have the 5687 directly connected with the 6V6...Kind of LofftinWhite design.Of course, The cathode resistor of the 6V6 will have to be changed. Fast calculation gave 4,375K/10W . And we put a cap // with te 5687 cathode res.
    Tough part now, if I go this way is the PSU.Gilbert Preyale and I are working on it, but since I m pretty busy, I can't spend too much time on it. I can send you the scanned design in progress, but without values, since they are not calculated yet.
    To give you a hint, we should work with a main transformer giving 2 HV secondaries. One about 600V for the 475V B+, the other for the 175V (or is it 170 ?) goig to the 5687.
    So...It's going a little crazy, but "le ridicule ne tue pas" as we say in France. Picture this:
    Stereo block with separate power block. So far, so good.
    The PSU:
    TRX-HV#1-valve#1-L-C-L-C-----B+
    -HV#2-valve#2-C-L-C-L-C------b+
    Of course, some resistors here and there, (but preferably there :-)), just before we get B+ and b+.
    Is it reasonable ? My answer is NO! absolutely not...
    If we build it, I let you imagine the PSU box...Gonna look like Brasilia. Or some grunge XmasTree...But who cares?
    The fact is that I have in my junk box some chokes comming from ORTF, the former French national broadcasting company. I'm sure Bas Horneman will love this PSU idea...
    cheers.
    Eric
Re: 6V6 Parafeed with "Robin Hood" iron. - G 09:04:08 06/08/04 (8)
I see what you mean now eelind. See what I mean about dumb answers? Here is the correct schematic as it relates to the PSU diagram.
- Re: 6V6 Parafeed with "Robin Hood" iron. - eelind 09:36:33 06/08/04 (7)
  wow,makes sense to me now.
  Why has C2 disappeared on the 5687 cathode?
  If you change your schematics faster than I understand it,
  how could I ever build this amp? ;-)
  - Re: 6V6 Parafeed with "Robin Hood" iron. - G 14:03:27 06/08/04 (6)
    With the high plate load on the 5687 because of the plate loading choke there is no need to bypass the cathode resistor to lower the plate impedance. So I was able to eliminate the distortion causing cap. In my initial iteration of this design I was going to use a standard plate resistor which made the capacitor necessary. Cheers.
    G
    - OK - eelind 22:08:52 06/08/04 (5)
      right !
      Clear, simple, easy...should sing like a nightingale (with big chests)
      Any advice before I order the RobinHood and MQ chokes? ? I have almost all the other parts in my dash.And should get rid off of wife and kids in a few days...so I'll have a little time to continue my love affair with my soldering iron...
      Do you or Mike think that 3,3uF instead of3uF could work ? I have a pair of auricaps from paramours, since I replaced them with Jensen copper .
      Eric
      - Re: OK - G 04:07:15 06/09/04 (0)
        
        In Reply to: OK posted by eelind on June 08, 2004 at 22:08:52:
        
        Also notice that all of the caps I was/am going to use in the amp are metallized film caps (motor run caps). THey are quite large. I was/am going to stick them to the underside of the chassis (a la Zen amp) with high temp silicone. That means the chassis needs to be about 15 inches across for my layout. You might want to just use electrolytics. Up to you of course. I'm fond of the Zen layout so I will leave you with this link. It may help.
        G
        Zen amp tutorial. (Open in New Window)
      - Re: OK - G 03:41:14 06/09/04 (3)
        
        In Reply to: OK posted by eelind on June 08, 2004 at 22:08:52:
        
        What type of chassis do you plan on using? The schematic of the PSU is obviously not for monoblocks. I was going to use a Zen amp layout like this one kind of. I was going to mout all of the chokes underneath the chassis. Whatever yo do make sure to keep the laminations perpidicular to one another and you should be fine. Michael Perrcy has a nice selection of Mill's WWs and Kiwame carbon films. Keep us up to date. Cheers.
        G
        
        Re: OK - eelind 06:25:25 06/09/04 (2)
        
        In Reply to: Re: OK posted by G on June 09, 2004 at 03:41:14:
        
        lots of informations...
        I understood the PSU caps were motor caps, and, alas, I've had little surprise with them when I tried to replace electolytics in some amp ...not the same size, as you say...So this time,I'll take my time and a large sheet of aluminium. And mount the caps verticaly.As I did not do for my End Of Zen, but like I did for the VTV pre I'm building. If only I knew how to stick pictures in this message, I could show you (proud poppa syndrom ;-)
        By the way, It's funny you are talking about building this 6V6ParaFeed in monoblocks. Kept me awaken this night,as I was thinking of redesigning the PSU for MBlocks. With 5U4GT instead of GZ34. Not that I prefer the 5U4GT, but I have a dozen of them and I don't know where to put them.
        Do you think It's possible to go Mblocks 5U4GT ? Want to try to redesign PSU ?
        Eric
        
        Re: OK - G 15:28:32 06/09/04 (1)
        
        In Reply to: Re: OK posted by eelind on June 09, 2004 at 06:25:25:
        
        Hi Eric,
        For monoblocks you would need to change the 75 ohm resistor to 150 ohms and change the 4.7K resistors(or resistor in this case) to 2.5k. If you decide to only use one choke then substitute one with a 270 ohm power resistor and all of the values should stay very close ie +/- 2%. Changing from a 5AR4 to a 5U4G will not make a whit of difference practically speaking. Please post pictures of the build. May your solder flow smoothly :).
        G
        
        Re: OK - eelind 00:26:07 06/10/04 (0)
        
        In Reply to: Re: OK posted by G on June 09, 2004 at 15:28:32:
        
        I already have the Power transformer, and the chokes and the caps It will be stereo block...As soon as I have the answer from Mikey about trx shipment, and as soon as they arrive.
        
        I'll let you know.
        Thanks for this design.
        Eric
Re: 6V6 Parafeed with "Robin Hood" iron. - eelind 08:28:15 06/08/04 (2)
Sorry for my stupid question, since I'm very close to a tube newbie, but what is he difference between B+ and b+ in your PSU design ?
- Re: 6V6 Parafeed with "Robin Hood" iron. - G 08:56:58 06/08/04 (1)
  I've found that while no question, honestly asked, is stupid, some of the answers you will get are:).The B+ represents the 320 volts for the power stage while the b+ represents the lower 170 volts for the gain/driver stage. If you take a look at the PSU diagram you will see what I mean. Cheers.
  G
  - Re: 6V6 Parafeed with "Robin Hood" iron. - eelind 09:31:48 06/08/04 (0)
    Ok, i've looked again, and I understand.
    Thank you very much
    Eric
suggestion.... - Sector-7G 08:13:07 06/08/04 (3)
HEy-Hey!!!,
Since you already have a grid choke for the 6V6, why not go fixed bias? This will get rid of the imperfect cathode resistor-capacitor combo, and give you a bit of free headroom.
Knock B+ down into the high 200's and you'll be able to run almost any of the traditional audio power valves. EL34, 6L6, or the almost-6V6's the 6EY6 and 6EZ5. or rig an adapter up and plug in EL84's...
Anyway, I look forward to hearing from you about how it sounds.
regards,
Douglas
- Re: suggestion.... - G 08:50:54 06/08/04 (2)
  It was suggested that a string of LEDs under the cathode of the 5687 would be the best way to bias it. I have never tried fixed biasing nor using LEDs in that way. It will be a while before I build the design ,as I've just finished a SE EL34 amp and I am saving my pennies for a tube buffered volume control to go with it, but when I do I will certainly try both methods on the breadboard before I finalize it. Thanks for the reply.
  G
  - Re: suggestion.... - Sector-7G 09:12:32 06/08/04 (1)
    Three or four red, 20 mA LED's will do quite well for the 5687. Anyway, have fun with it. If you build it heavier than you need to at first, there is more room to fiddle with things later. IMO a very good practice for evolving DIY projects. It has been cheaper for me in the long run!
    regards,
    Douglas
    - Re: suggestion.... - G 12:19:30 06/08/04 (0)
      Never fear. I am an accomplished "overbuilder" :). Thanks Douglas. Cheers.
OOoooo I like it...lots of iron...!!!! (nt) - Bas Horneman 07:42:33 06/08/04 (0)
.
6V6 Parafeed PSU - G 06:05:57 06/08/04 (4)
Here is the PSU.
- Re: 6V6 Parafeed PSU - Jeff Lessard 12:43:50 06/08/04 (1)
  How about ditching R1 and lowering the uF value of C1 to compensate. I've never been a big fan of voltage dropping resistor before the B+.
  The Duncan power supply simulator (PSUD2) is handy to model PSU.
  - Re: 6V6 Parafeed PSU - G 14:04:54 06/08/04 (0)
    You are welcome to do so.
    G
- Re: 6V6 Parafeed PSU - AnandR 11:41:54 06/08/04 (1)
  Great job! Good clean capacitor input power supply design and very easy to follow. The design is bound to sound good with a clean supply like this one. I do have a preference for damper diodes now. However, I do admit I haven't freely rolled enough GZ34's to get a good handle on how good of a rectifier tube it is. Please post your pictures when you are done.
  
  Good luck and thanks for posting,
  Anand.
  - Re: 6V6 Parafeed PSU - G 12:24:38 06/08/04 (0)
    Thank you very much Anand. I may yet use a pair of 6AU4s instead of a 5AR4. I hear they are the quietest thing going in power supplies. It will be a bit before I build the amp though. I'm saving for a linestage for my newly completed SE EL34 amp.
    G

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