I have been using OTL amplifiers with ESLs for 3 decades. But I am always looking to improve my OTLs and ESLs, so it is ever evolving. Just getting into vinyl in a bigger way than ever before. I never before had more than one tonearm/tt/cartridge combo.
Lenco L75 w/mods mounted in custom slate plinth using PTP3 top plate and Jeremy's Super Bearing (see Lenco Heaven). Tonearm Dynavector DV505. The Lenco is now featured in my basement system, based on Beveridge 2SW speakers. Performance upgraded by the Phoenix drive amplifier in conjunction with the Roadrunner tachometer, controlling platter speed very accurately.
Kenwood L07D
Direct-drive turntable with built-on tonearm, uses coreless, slotless motor, factory plinth brings total wt past 65 lbs. The quietest turntable I ever heard in my life. Seemingly antiquated tonearm sounds fab. I love this thing.
Technics SP-10 mkIII
I found this Mk3 NOS in Florida. I made a slate and wood plinth for it, and Bill Thalmann went through the electronics. Bill also performed the Richard Krebs mod, and JP Jones added his chip made of discrete parts, which is a replacement for the OEM chip, MN6042 (I think). The slate is 2.5-inches thick, and the base is made of solid cherry and baltic birch. Imbedded in the bottom of the wood base is a large threaded brass block. A threaded brass rod traverses the block and contacts the underside of the bearing housing, a la Albert Porter's idea, to drain energy. A 10.5-inch Reed tonearm is mounted on a slate armboard. I also have some aluminum armboards and other tonearms to try. Lately using the Boston Audio Mat2.
Atma-Sphere MP-1
highly tweaked by moi. A wonderful unit to begin with.
Silvaweld SWH550
All-tube phono stage, now discontinued. I use it for MM and MI cartridges and with the MC2000 via the outboard current-driven gain stage. Its output runs thru my 3160 phonolinepreamp linestage section.
Atma-Sphere MA240
Many, many power supply and circuit upgrades since original. Originally used six 6C33C output tubes in circlotron OTL. Now modified to use four type 7241 triodes in output stage. Output tubes are driven by four discrete Super Linear Cathode Followers, a la the late Allen Wright. This facilitates very accurate matching of output tubes for bias current, so no single tube is either hogging current nor not carrying its fair share. Uses solid state cascode constant current sources throughout. Now using type 7199 triodes as input dual differential cascode voltage gain section.
Sound Lab 845PX
modified audio step-up transformer and crossover, to present a high impedance for my OTLs. All resistors and capacitors were removed from the passive crossover in the backplate. The OEM Sound Lab treble toroidal transformer was replaced by a full range EI type transformer with a 1:90 step up ratio. This full range transformer is in parallel with the OEM Sound Lab bass step up transformer. Photo shows old M1s in my listening/living room. Picture the same black monoliths only taller and wider, if you want to envision the 845PX.
Ortofon MC-7500 and MC2000
The MC2000 is my current favorite LOMC cartridge. Neither of my two high gain phono stages (MP1 or 3160) by themselves have enough gain for the 0.05mV output of the MC2000. I run it either through an outboard current-driven phono booster (think head amp or pre-preamp) built for me by Dave Slagle, into the MM section of my Silvaweld phono stage OR into the BMC MCCI ULN Signature current-driven phono stage, and then in either case to the linestage section of the 3160.
I listen to a lot of different vintage phono cartridges. I have a small collection, many of which I have not yet heard. To date my favorites are the Stanton 980LZS, the Grace Ruby, the Acutex LPM320STRIII, and the B&O MMC1 and MC20CL . In many ways I prefer these cartridges to higher end LOMCs that I have heard, but the jury is out and probably always will be out. Best MC types I own are the Orto MC2000, Koetsu Urushi (now at home in the Fidelity Research FR64S on my Victor TT101, to be found in my basement system), and the Dynavector 17D3.
3160 Phonolinepreamplifier Full function preamplifier
Fully balanced, dual mono, solid state preamplifier with two completely discrete high gain phono stages plus linestage. I have been using this unit for a few years along with the MP1. It's by far the best solid state phono stage(s) I have heard in my system, and it rivals any tube unit as well. Built by R&J in Mexico.
Denon DP80 turntable
Found this 100V unit in California. Bill Thalmann replaced the single chip and upgraded all the discrete transistors and then calibrated it. I use an inexpensive 120V to 100V step down at the wall socket. I had a 60-lb slate plinth made and mounted my Triplanar on the slate surface. The Denon replaced the Lenco in my "upstairs" system, when I moved the Lenco to the basement Beveridge system. Using a Boston Audio Mat2 here.
Grateful, I did all the mods but in consultation with two very smart guys who know more than I do - Naz from VA and Allen Wright. It would be an exaggeration to say that AW did anything directly; I learned from his Tube Preamp Cookbook, and at the final decision point he did communicate his opinions to me directly. One reason I modified my MP1 was because it was a very early version and came to me in pretty limp condition. (I bought it used.) I had to rebuild the entire power supply before I could even listen to it. In so doing I incorporated a regulated DC filament circuit that had been designed by Mark Gilmore, who was then associated with Atma-sphere. The HV supply is now regulated by a pair of SuperRegulators from Vacuum State Technology. All rectification is by hexfreds. The LV supply to the circlotron output stage uses low DCR, low Henry inductors in both the pos and neg legs and is filtered by the latest Panasonic TS-ED caps, which are bypassed on the audio chassis by film caps. I raised the current supply to both the phono and linestages. I created CCSs for all active gain stages using ECC99 triodes in cascode topology. The phono input now uses a hybrid cascode constructed from an MAT02 bipolar transistor on the bottom and an ECC99 on top (idea copied from AW's RTP3C preamp). This gives a huge amount of gain, more than enough for my Ortofon that puts out 0.12mV. The output of the phono stage now uses another ECC99, which gives a much lower output impedance compared to the stock 12AT7. There is a resulting sacrifice in phono output stage gain, but I don't feel it because of the huge gain at the front end of the phono. There's lots of expensive parts, teflon caps, bypass caps all over the place, etc. There's more, but my fingers are tired. If you have a specific question, let me know.
Dear Lewn, congratulations for your nice system set-up ! And welcome to the Lenco-in-slate club ! I use mine with a Graham Phantom / Allaerts Finish and I am amazed by the performance compared to all my other TT setups. The next step I have done is stacking a heavy 15 kg. platter ( VPI Superplatter) on top of the Lenco platter and now I can say it is a world class TT ! We are designing a new captive bearing to support and improve the original bearing. I also use ESL 57, great match...I will try with Atmasphere at LH meet... Best, Jean
I have been heavily pre-occupied with set-up of a rig that will allow me to audition all the MM and MI cartridges I bought as a direct result of Raul's thread. It did not seem practical to modify the MP1 preamp in order to suit MMs. That is, I would need to be able to reduce the gain of its phono section such that I could quickly switch back to MCs. This can be done, but when I tried it, the dynamics of the sound were noticeably reduced along with gain. Therefore, I came to the odious conclusion that I needed to have a separate dedicated MM phono stage. I finally selected an Ayre p5xe, which I was able to buy used at a good price. The Lenco in slate with PTP3 top plate (photos soon to be added) will serve as the MM test bed, with a Dynavector DV505 tonearm. I also recently bought a Kenwood L07D turntable. What can I say? I could not resist at the very fair price asked. Now I am really motivated to thin out my turntable "collection". One of the SP10 MkIIs and my Garrard 301 grease-bearing must go, along with my other Lenco in wood plinth. More anon.
Dgob, As I think I told you privately, my preliminary impression is that overall I prefer the Denon/Triplanar/Urushi combo to the SP10/RS-A1/Ortofon combo. Certainly the Ortofon does not blow away the Urushi at all, although one obvious factor is the difference in tonearms, which I will eventually address. Also, I assure you that I favor "accurate" reproduction vs euphonic. My many mods to the MP1 and MA240s have all been in that direction. But I generally believe that any OTL amplifier, when it is happy with its speaker load, is going to be more accurate or certainly not more colored than a transformer-coupled amp. If the speaker load is not right, i.e., if the impedance is too low, then OTLs do fall apart.
My pleasure. I think the Colibri and Ortofon will be startling improvements on the Koetsu. Not heard/owned the others but I know that Raul really rates them. It'll be good to hear your impressions once you'vbe had time to audition them. Have you experimented with phono stages at all? I used to have the MP1 and MA1 combo and found it addictive - if not the most accurate.
Also, I have a SP10 MKII that is being built up using a highly engineered mixed material (birch, acrylic and aluminium) plinth and have avoided slate largely due to high costs charged and uncertainty about its performance. What's your view on it and where did you get you plinths done?
You sure look set to have some fun times ahead with your ever growing quality products.
Thanks, Dgob. I don't know why I listed only my Ortofon cartridge. I would have to say that the cartridge I have been listening to for a few years is the Koetsu Urushi. I recently acquired the Orto and have a couple of hours of listening to it on the RS-A1, whereas I am accustomed to the Urushi on the Triplanar. I just bought a vdH Colibri but have not heard it yet, and thanks to Raul and his thread, I have also acquired two B&O MI cartridges, the MMC1 and MMC20CL, an AKG P8E, an Ortofon MF20L Super (or whatever it's called), and I dug up my old Grado TLZ. Listening to all these guys on all three tt's should give me plenty to do come wintertime. Meantime, one of my Millenium 1s has developed a chronic whistling sound; I will have to trouble-shoot it. It seems to go away during music play.
