Welcome to another meeting of Audiolics Anonymous, our support group for the insatiably tweaked. Did we listen to any music this month all the way through? I know that the only exercise you get is rising from your listening chair to change the CDís or LPís after two to three minutes, but, remember, music is made to be listened to all the way through. There are four levels of tweaking equipment:
The kit for discussion today is a single ended triode parafeed transformer output monoblock amp called the Paraglow, by Electronic Tonalities of Poulsboro, Washington, www.bottlehead.com, e-mail firstname.lastname@example.org. owned by Doc Bottlehead, a.k.a., Don Schmalle. Other than the kits, he also puts out a magazine called Valve, and runs a forum on tubes at the www.audioasylum.com. I was given the assignment to build them by Steve Rochlin because he knew I am into tweaking, have built my own horn loudspeakers, and interconnects and speaker wire, and have done some adapting of other peoplesí equipment (and are an all around groovy dude. You da man!!! ---ed). What he didnít know was that the only other kit that I had built, was an integrated tube amplifier from Lafayette Electronics in 1963. That amp was a little push-pull beauty that I built over several days. It looked wonderful, especially when I turned it on and the tubes began glowing a beautiful red for about one minute, after which a great puff of smoke shut it down. I sent the unit back to Lafayette, and got a beautiful letter of condolence from them after they had given the unit a proper burial. It seemed that every solder joint was cold, and at least one of the high voltage connections was incorrect. Since then, I have learned better soldering technique, and at least how to use a volt-ohm meter. I have also been a member of an Internet discussion group run by Joe Roberts, editor of Sound Practices magazine, on tube amplifier design, and have been dying to see if I had learned anything from the group. Read on to see if Steveís trust in my abilities was misplaced.
Doc has designed several kits of varying price, difficulty, and quality, and, interestingly, has given them names such as S.E.X., Foreplay, Afterglow, Big Studs, and Paraglow. Sort of fit with the Tweakerís true interests in life. This kit is his top of the line: a pair of monoblock single ended tube amps, with a circuit consisting of a direct coupled (no caps or transformers at input, between tubes, etc.) with active loaded input/driver stage (half of a 5965 tube with a Camille Cascode Constant Current Source), driving a 2A3 in parallel feed output configuration, with a Permalloy core parafeed output transformer. RCAís are first rate, and the Big Stud speaker connectors are very manly. It was designed by Doc., and John Tucker, and Mike LaFevre designed the parafeed output iron, and John Camille the C4S active load. It consists of 8 pieces of wood for the bases, two chassis tops of anodized aluminum, a pair of 2A3 and 5965 tubes, various resistors, caps, wire, sockets, and connectors, Magnequest transformers and inductors, and the C4S constant current source. All parts are of very high quality, and everything needed was there except for two small bolts and nuts, which I had on hand. The wire supplied was from Jena labs, and was of both excellent sonic quality and very easy to solder. The only glitch was that I was about two feet short of enough, and therefore used some Allen Wright silver foil. Although I was itching to try out parts other than those supplied by the good Doc, I held back as I wanted to se exactly how the supplied kit would sound without tweaks. That was the most difficult part of the construction.
Doc Bottlehead has saved tons of money by basing all of his amp kits on the same chassis, base and a large percentage of the parts, which makes for great economy, and has definitely passed on the savings to the consumer. The Paraglow is their top of the line kit, and therefore takes up most of the space inside the chassis, but there was still enough room for even my large hands to easily solder the connections. One can even start with one of his less expensive kits, and upgrade to the top of the line Paraglow, without having to throw out the amps. A tweakerís dream (Bill is in seventh heaven here folks -- ed).
The circuit is simplicity itself, which I feel is very important in single ended amps, where every part in the circuits can be heard. It is based on 50 year old technology upgraded for the millennium. The power supply uses a Magnaquest power transformer, cap-choke-cap smoothing, and unlike most single ended amps, uses a solid state UF 4007 diodes for a fast recovery, soft start rectifiers. He feels that they have all of the advantages of Hexfreds and tubes, with few of the disadvantages. Weíll see.
The input or driver tube is a 5965, one half of which is used as voltage amplifier and driver tube, the simplest circuit possible. It uses John Camilleís C4S cascode constant current source as an active load instead of the normal resistor load for more stable performance. This is directly coupled (no cap or transformer) to the grid of a 2A3 output tube, operating in parallel feed single ended configuration, ala Loftin-White, into the Magnequest output transformer, which can be configured for either 4 or 8 ohm loads. The 2A3 was originally produced in the 30ís, even before the Western Electric 300B, and can put out up to 3 watts of triode power. This kit was supplied with Chinese tubes, but it can also be used with the new KR or AVVT 2A3ís with the replacement of one resistor, and is said to provide more current and purity of sound, when used with these tubes. Some tube aficionados feel that it lets more of the music through than even the 300B, but at the expense of a lower wattage.
The output of the 2A3 then goes through a Parafeed circuit to a Magnaquest output transformer set for 8 ohms. The parafeed circuit is also a 1930ís invention to keep the DC on the output plate of the tube out of the output transformer without using a cap or transformer directly in the signal path, thus allowing for a much smaller transformer, without air gap, making it much easier to extend the frequency range, due to less windings, higher inductance and the use of high permeability laminations, not to mention the fact that this decreases the weight of the unit. It splits the DC from the AC by using an extra air gapped inductor between the plate and the power supply to allow DC from the power supply to the plate while blocking AC, and a cap after the output transformer to block DC flow to it. When I first looked at the kit transformer at 3x3x2 inches size, compared to my Electraprint single ended outputs which are 4x5x6 inches and weigh about 8 or 9 pounds compared to about 1/2 pound for the Magnaquest, I thought ďthere goes the deep bass.Ē But Doc claims the output transformer has a bandwidth of 2 to 47 kHz +/- 1dB. All of the inductors and transformers have been built by Mike LaFevre of Magnequest, especially for this amp.
The C4S active
load, designed by John Camille, provides a constant current source with 5 Megohm
effective impedance, permitting near theoretical gain performance from the
voltage amplifier stage, with claimed reduced distortion in the driver stage
of several hundred percent, with 40 times less noise than the standard
resistor circuit. Does it work? Read
First, I had three problems with the kit. One, the supplied wire fell short by about two feet. Obviously not a problem for we tweakers, but may be for others. Two, the power cords suck. Iíd suggest that Doc place an IEC connector in the kits as most people building this kit will probably want to experiment with power cords. Third, the inductors and transformers, which are on top of the chassis, have no end bells, and no mention is made in the directions about finishing them prior to mounting. Fourth, the Doc has a great idea about extending the lives of the 5965 tubes by setting up the tubes in mirror image using the opposite half of the tube in each amp. Unhappily, this makes the wiring a little more difficult, so yours truly didnít do this until I read the reasoning which was written into the directions after the procedure. A little reverse in the directions would help those males who prefer to do before reading. Otherwise the kit is a dream to build. Anybody who can read and eat in a restaurant without making a fool out of himself, will be able to construct this kit.
Time for construction- approximately 12 hours for me. A very enjoyable 12 hours, divided into four sections- construction of chassis staining, etc., adding large parts to chassis, ground buss and inductor wiring, and placing diodes, caps, resistors, etc. Finally testing of the circuits with a volt-ohm meter. This last step is very important. Even I found one cold solder joint - not a bad improvement from 30 years ago.
LIMITED. Once you have started the kit, you cannot return it for money, but they will take it back to redo the wiring for a fee. They will also replace any defective components. Also they have a technical hot line at (360) 697-1936, fax at (360) 697-3348, e-mail at email@example.com. I e-mailed them twice, and had replies almost instantly. Better than a phone (the internet rules!!! --ed).
In one word, GLORIOUS!!! I have had many types of amps in my system over the years, and am currently using Electraprint Audio VV-32 monoblocks, which until now were my favorites. But these amps beat them hands down. After only a few hours of break-in, they presented a soundstage from room edge to edge, with at least five feet more of depth than Iíve heard before. Even on digital, I could make out hall sounds never heard before. For instance on Cantate Domino from Proprius, on the tracks with the soprano solo, I could actually feel into the hall, hear doors closing, traffic outside, and the organ bellows chuffing away. On some RCA shaded dogs of the BSO in Symphony Hall in Boston, one could hear the outside traffic noise only on the right side, where it belongs.
The mid range was almost palpable, with voices taking on that three dimensional quality of a living body. Bass down to 50Hz. was tight, controlled and THERE. Measurement showed it to be flat down to at least 10 Hz, but my system uses a subwoofer below 50, so I couldnít listen that low. Highs extended out as far as I could hear. There may have been some second order harmonics present, as these are almost always found with single ended amps, but they did not intrude into the sound at all.
Output was probably only 2 to 3watts, but with my horn system with 108 dB/w/m/ sensitivity, this wasnít a problem. But I would suggest using these amps only with high efficiency speakers. I understand that using the new KR or AVVT 2A3 tubes will add more current, and thus more power, but I will have to wait for some to let you know.
The units are bought factory direct by either calling or going to their web page. Cost- about $1150. As far as Iím concerned a STEAL. Grab a pair before the good Doc. sees a psychiatrist and comes to his senses.
Thatís a great advantage about these units. As you are building them, you can change parts at your leisure. The nice thing about these amps is that the circuit is so simple, that any part change will make a difference in the sound. The only disadvantage, is the lack of space on the chassis, which will make changes a little more difficult than with a bigger unit. The Doc even sent me out a list of suggested changes and additions which I will try in the future.
You can bet your soldering iron I am. So satisfied that I have bought the two units. So, sorry Steve, but you canít have them back. They are mine. But maybe you or anyone else in the New Hampshire area will want to come over for a listen. Iíll be glad to demo them, if they are not being tweaked at the time. Well, thatís two superlatives Iíve given in the past two months, one for this amp, and the other for the Audio Desk CD Lathe. Both well worth the investment for the addicted tweaker.
Thanks to Gary Bronner for his letter about my last article on the CD lathe. He suggested that making a CD-R of a CD has a similar effect. I have heard this also, and would welcome any ideas as to why these tweaks can improve the ďperfect sound foreverĒ CD. Seems we have a lot to learn about digital, and that the tweakers out there are doing all of the work, and not the digital engineers. Keep it up boys.
Well thatís it
for this meeting.
Head Ed. Steve said "Ok, so i went to Bills to personally hear what he is raving about here. Lemme tell you folks, they are possibly better than Bill is stating in his above article. So good in fact a second sample has been ordered from good ol' Dr. Bottlehead which Bill has volunteered to kindly put together for me. These new review samples will, i repeat Bill, will come home with me!!! My feelings are that the Avantgarde Acoustics Uno's will love these amps. Expect a follow-up by me in a few issues. Need we say more here folks?"