LonestarBlues Posted August 9, 2003 Share Posted August 9, 2003 Hello. Dr. Lloyd Peppard of Mapletree Audio Design visited our forum back in May. I was interested in his Octal 6A tube preamp and asked if he would build one with upgraded parts. He said yes. Well Dr. Lloyd has started making an SE version. The Octal 6A has 3 circuit topologies-common cathode+cathode follower, SRPP & passive. The common-cathode+ cathode follower uses Riken carbon film resistors & Jensen paper/oil capacitors. The SRPP uses Caddock metal film resistors & Hovland foil/polypropylene capacitors. Power supply & bypass capicitors are all Blackgate electrolytics. The Octal 6A SE preamp is $750 factory assembled/tested. He has a picture of the innards of the new SE preamp on his website. I am very interested in this preamp to go with my Llano Phoenix mosfet/ tube hybrid amp. I also asked Dr. Lloyd about the feasibity of adding tone controls. Dr. Lloyd stated he would be happy to build tone controls into an Octal 6 SE. He said he would use the traditional tone control circuitry (e.g. as in the Mullard design book) located at the input of the preamp followed by the volume control. The only real design issue is providing enough additional gain to make up for the tone control loss 10-12 db. There is at least 20 db gain with the active topologies. Dr. Lloyd wanted to know the input sensitivity of the Phoenix amp to make sure it would be compatible. I emailed Randy White of Llano Design to get that info, I do not know what voltage the input sensitivty is. He also wanted to know the output voltages of my sources and what speakers I was using. The output voltage of my Pioneer Elite PD 65 cd player is 2.0, the output voltage of my Mcintosh MR 77 tuner is 2.5. And the 1983 Cornwalls are 98.5 db efficient with 1 watt. If I buy this preamp I will use the Mcintosh C 38 preamp that I am now using with the Llano amp with my Mcintosh MC 7150 amp. The Mcintosh has been idle since the Llano Phoenix replaced it in mid May. I still have my purist system (no tone controls) Welborne Labs Moondogs & Revellie tube preamp, Mcintosh MCD 7009 cd player, Technics ST 8077 tuner and 1977 Cornwalls. I am listenig to the Moondogs now. I still like tone controls on a preamp and always will. The Octal 6A SE with tone controls would run $950. Dr Lloyd stated he would use high quality passive parts in the tone control section. Well enough of my rambling, I have been knocking back a few Lonestar longneck beer. Regards, Mike Quote Link to comment Share on other sites More sharing options...
NOSValves Posted August 9, 2003 Share Posted August 9, 2003 Lonestar, I also am doing some business with Lloyd at the moment. I really can not go into details to soon in the game. I can say this I think I'm a pretty good judge a character and Lloyd is a man of principals and very trust worthy. A real change of pace in this day and age. At this point all I can say is I wouldn't hesitate to recommend him ! Craig Quote Link to comment Share on other sites More sharing options...
JBryan Posted August 9, 2003 Share Posted August 9, 2003 Interesting preamp ...where's the site? Quote Link to comment Share on other sites More sharing options...
NOSValves Posted August 9, 2003 Share Posted August 9, 2003 www.Hollowstate.netfirms.com Quote Link to comment Share on other sites More sharing options...
JBryan Posted August 9, 2003 Share Posted August 9, 2003 Thanks! Quote Link to comment Share on other sites More sharing options...
hollowstate Posted August 9, 2003 Share Posted August 9, 2003 Just thought I would add a note or two about the Octal 6A SE. I built the prototype as the request of a customer who wanted me to use some "premium" passive components. He was not a technical person and had no specific components in mind so I thought the best route would be to choose parts which were likely to push the sonics in different directions for the two active circuit topologoes of the Octal 6. This makes more sense than trying to predict the effect of replacing stock components in a design with so-called premium parts--you may get an effect, but is it better or just different? So I tried to push the "classic" topology (common-cathode + cathode-follower)further toward a full-bodied, gutsy character by using carbon film resistors and paper/oil caps. There are lots of choices but without much hard experience, I chose Riken 1W resistors and Jensen oil/paper caps (actually, due to a supplier backorder, one set of Jensens and one pair of 1 uF/400 V caps salvaged from a Tektronix scope--probably similar to Sprague Vitamin Q's). For the SRPP topology, I aimed to enhance the detail and analytical capabilities of this circuit by going with metal film resistors (I chose Caddocks) and film and foil caps (I chose Hoveland Musicaps). Again, there are lots of other choices and I have no experience with comparing these kinds of parts. As a skeptical engineer, I was astonished that the differences in the two topologies was no longer subtle. The CF circuit was indeed "fatter" sounding--even the bass sounded more like that you might expect from a SE power amp. The SRPP stage was lighter and more airy. I prefered it to the CF circuit in my casual auditioning--I wanted to get the unit it shipped to the customer as quickly as possible. The bottom line is that the use of permium parts to produce two sonic flavors in a single preamp is a realistic goal and has nothing really to do with higher quality. My feeling is that one might achieve similar results with less costly components of similar construction. I have a bunch of Russian 2uF oil/paper caps and boxes of old Philips 1W carbon film resistors that could be used in the CF circuit and generic metal films (e.g. Beyschlag-Centralab) and Sprague 716 polypropylene/foil caps for the SRPP. If I only had the time to experiment . . . One last note--one of the benefits of the Octal 6 SE is that with the extra cost, I felt inclined to do a "industrial/military" wiring layout with cabled wires, right-angle bends, etc., shown off by a plexiglass bottom plate for the preamp. So if your friends are not impressed by the sound, you can show them the innards! I welcome comments/suggestions. Regards, Lloyd Quote Link to comment Share on other sites More sharing options...
Deang Posted August 9, 2003 Share Posted August 9, 2003 I think it would be interesting to hear the outcome of trying to bring a little more balance to each circuit, and then see if they are brought closer to one another sonically. Say, film and foils/ metal oxides in the cathode follower type, and PIOs/ carbon resistors in the SRPP circuit. It seems you make some very fine products, as they are well received whenever I run across comments about them. Quote Link to comment Share on other sites More sharing options...
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