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The Dynaco Tube Audio Forum

Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Tubes4hifi VTA tube amp and preamp kits and all products

    REVIEW - Tubes4hifi SP-8SE tube preamp KIT

    Bob Latino
    Bob Latino

    Posts : 2924
    Join date : 2008-11-26
    Location : Massachusetts

    Preamp - REVIEW - Tubes4hifi SP-8SE tube preamp KIT Empty REVIEW - Tubes4hifi SP-8SE tube preamp KIT

    Post by Bob Latino on Tue Sep 22, 2009 6:07 am

    Roy Mottram, the designer of the VTA driver board and the SP-6, SP-8 preamps, was kind enough to ship me one of his wired and tested SP-8SE (Special Edition) "kit" preamps for evaluation. This preamp is 16 inches wide by 4 1/4 inches high and 12 inches deep and weighs in at a healthy 11 1/2 pounds. The preamp has four high level inputs and one phono level input. It has one tape loop and two outputs on the back. The two outputs are handy if you biamp at times as I sometimes do. The front panel has a left gain and right gain control and a master volume control. The master volume control is a stepped attenuator with 24 levels of volume. The left gain and right gain controls have 12 levels of gain and allow you to alter the gain of each channel independently (and subtly) effectivly giving you a "balance" control. The control on the far right is an on/off/mute control. The lamp under the on/off/mute control changes from green to red when the preamp is in the "mute" mode.

    Internally the preamp is laid out very cleanly with the entire circuit on one board and a number of neat sets of wires going to the preamp's controls. The board uses two 12AU7 tubes (line stage), two 12AX7 tubes (phono stage) and one 12X4 rectifier tube. The striking component though is the large, 4 1/4 inch diameter, 4+ pound torroidal power transformer. Personally, I have never seen this large a power transformer in a preamp KIT before.

    I connected the preamp to my personal 60 WPC ST-120 tube amplifier. The ST-120 was connected to my Tyler Acoustics Linbrook II speakers biwired through home made speaker cables using Canare 4S11 speaker cable. The signal source in this system is a Nakamichi CD player sending the zeros and ones to a Bel Canto DAC2 D/A converter. This preamp is quiet with zero hum and only the tiniest bit of "hiss" when I placed my ears ON THE GRILLECLOTH of the Linbrook II speakers. A foot away from the speakers you could hear nothing! This preamp scores high in the "cleanliness" category.

    Playing various CD selections, I was really impressed with the bottom end response of this preamp which was every bit as good as my BAT VK3i preamp which I normally use on this system. The BAT VK3i uses 4 6DJ8 tubes and with its remote and phono board is a $3000 preamp. The SP-8SE's top end was clean, smooth and "effortless" and its sound character did not seem to be altered when the volume went up. Many kit preamps starve for power when the volume goes up because the power supply was skimped on to keep the price of the kit preamp down. Not so in this case. With the ST-120 amp, I found that the two gain controls worked well at their 12 o'clock (center position). With the two gain controls set there and the master volume at 12 to 1 o'clock, the sound was pretty loud. In all honesty I would have to say that the sound quality was as good as my BAT VK3i at about 1/3 the price of the BAT. The BAT does have a remote and 140 volume steps but if you don't need a remote and can get by with the 24 steps in the SP-8SE you can save yourself a bunch of money.

    I then brought the SP8-SE to my big downstairs system and put it in place of the other BAT preamp that I have - a BAT VK30SE tube preamp which uses four 6H30DR tubes. This is a $6000 tube preamp with it's remote and phono board. The phono board in this preamp, by the way, is the same as the one in the upstairs BAT-VK3i. In the downstairs system I have a Music Hall MMF-7 turntable with a Goldring Eroica H moving coil cartridge with a Geiger II line contact stylus for spinning vinyl. In this system the SP8-SE was running into a Bryston 4B-SST 500 WPC (into 4 ohms) power amp and then biwired to two Magnepan MG 3.6R planar magnetic 4 ohm speakers. I played both CD's and vinyl though this system. The CD's were handled by a Classe CD-1 CD transport into another Bel Canto DAC-2 D to A converter that I have. The SP-8SE acquitted itself very well against this far more expensive BAT preamp. If I had to make a definitive choice for best sound quality I would probably go with the BAT for slightly superior sound staging and a smidge more bass from the BAT. IMHO the SP8-SE aquitted itself very well against a preamp costing more than 6 times what the SP-8SE kit sells for ($800). With respect to cost vs. performance the SP-8SE is really tough to beat.

    The SP-8SE is the finest tube preamp KIT I have personally heard. I have also auditioned in the past the Dynaco PAS-3, Bottlehead Foreplay and Audio Electronic Supply AE-3 tube preamps that were built from kits. Roy also sells the main SP-8SE board and parts kit separately for $209 + $11 shipping. The main board may be installed in your Dynaco PAS-2, PAS-3 or PAT-4 preamp for huge increase in sound quality. For more info on the SP8-SE and other photos and options on this preamp visit the tubes4hifi web page at the link below.

    The Tubes4hifi preamp page


    Preamp - REVIEW - Tubes4hifi SP-8SE tube preamp KIT SP-8SEfront

    Preamp - REVIEW - Tubes4hifi SP-8SE tube preamp KIT SP-8SEinterior

    Preamp - REVIEW - Tubes4hifi SP-8SE tube preamp KIT SP-8SEinteriorrear

    Preamp - REVIEW - Tubes4hifi SP-8SE tube preamp KIT Musicsystem

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    Preamp - REVIEW - Tubes4hifi SP-8SE tube preamp KIT Empty SP8-SE

    Post by breading on Tue Jan 26, 2010 1:57 am


    In your posted review of Roy's SP8-SE Preamp kit dated 9/22/09 you mention that the PCB can be installed in a PAS-3 chassis, however, Roy states on his website that it is not recommended in the PAS 3. What do you think?



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    Preamp - REVIEW - Tubes4hifi SP-8SE tube preamp KIT Empty SP6 or SP8 in a PAS3 chassis

    Post by tubes4hifi on Wed Jan 27, 2010 12:45 am

    trying to put an SP6 or SP8 preamp PCB into a PAS3 is highly NOT recommended,
    and I need to update any reference to that on my website.
    The SP6 circuit was originally designed many years ago to FIT into a PAS3 and use the PAS3 transformer. However, it's a VERY tight fit, and a total WASTE of money.
    You can buy a Dyna PAT4 for around $50 on ebay, and sell your PAS3 on ebay for around $200-250.
    This puts you around $200 ahead on cost, and you don't go thru the frustration of trying to squeeze it all into a space that's really too small, and throwing out almost ALL of the parts in the PAS3 other than the transformer itself.
    That said, I've been debating with myself for 4 years now whether or not to offer the SP6 (or upgraded SP8 version) on 3 separate PCBs that would fit easier into a PAS3.
    So far I've resisted this idea, as I still believe it's a waste of money.
    However, I've been asked this question so many times, that I've decided to go ahead and order PCBs that will be available around mid-February 2010 that will allow you to do this.
    The PCB set and the parts kit will be the same price as the SP8 kit now available, $89 bare PCB or $209 with a parts kit. If that makes sense to the owner of a PAS3 I'd like to hear from them,
    keep in mind I recommend replacing just about every single part in the PAS3, so the finished cost of this project is going to be $400-500 not including the original PAS3.

    Preamp - REVIEW - Tubes4hifi SP-8SE tube preamp KIT Empty SP8 preamp

    Post by gunner on Wed Jan 27, 2010 3:04 pm

    Hello,Another option instead of using a PAT4 chassis is try a SCA80,SCA80Q chassis.There are alot of these units that self-destructed that can be had for under $30 on ebay.I actually bought 2 of them,one working and one not,for less than $50 for the pair.I gutted the non-working unit and built the SP8 in it.I actually originaly built the SP8 in A PAT4 chassis but when I got The SCA80's I decided to restore the PAT4 and start over in The SCA80 chassis.MUCH more room in the 80 chassis,And its top Vented also.PAT4's are starting to be more collectable,and are getting into the $100 range on Ebay, and for what they are aren't that bad.Some Like them.Mine after the rebuild sounds every bit as good if not better than My Carver CT-17.In my opinion I wouldn't Destruct a PAT4 for this project.Use a SCA80Q chassis,as even when working the SC80Q is about worthless,where the PAT4 is not. Peace,G

    Preamp - REVIEW - Tubes4hifi SP-8SE tube preamp KIT Empty Pas 3

    Post by dejected on Wed Mar 24, 2010 4:09 pm

    HI, I have old pas-3 which had tone controls removed for AVA project years ago which was not done. I do not think pre-amp works. It would seem to me to make sense to use it without buying new chassis. Also have Pat-4 which works may as well sell it rather than strip it for project. Is SP-8 that good that I would want to buy new chassis to make it instead of SP-6. What is that differnt other than power tranny? Bubba

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    Join date : 2008-11-30

    Preamp - REVIEW - Tubes4hifi SP-8SE tube preamp KIT Empty SP6 vs SP8

    Post by tubes4hifi on Thu Mar 25, 2010 12:35 am

    the only difference is the SP6 was designed specifically to use the PAS3 PA211 power transformer.
    The SP8 has added filament and hi voltage regulator so it can use a variety of power, best is 250+250 or 275+275v around 50ma needed. 12vac at 2 amps for the filaments.

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