Analogue revived !

Randall Rash has a new amp.

Randys custom ampThis was a very special custom amp that I built for Mr. Rash. VT-25 (10) driven by a true grounded cathode 6c45p tube. I still miss listening to it, and the sonic impression it made upon my memory is lasting.

Randy has great ears, and knowing that he hears what I hear made me enthusiastic about this build. This amp was made for him after several conversations dating back to Oct of 2007. We listened to some of his equipment together, and talked about what he values most in audio. Realistic imaging is a weakness in all mass produced equipment, even tube amplification. Randys’ equipment (Zanden, Decware and Vaughn Carina) had a huge wide soundstage, but no depth. To our ears it made piano sound like it was the size of a semi-truck but flat and 2 dimensional. It took me a while to figure out how to control image depth and width, and Randys’ new amp does just that. It is the most accurate imaging amp I have heard. I was very happy to provide this equipment to someone who so appreciates it.

A little exurb from a recent email from Randy…


“…I spent 3 hours last night listening to music ….. wow …..  : ) There is no need to tell you how good the system sounds with the amplifier you designed and built because I am absolutely sure that you already know. I could use all of the worn out superlatives that describe an outstanding piece of equipment, but they honestly would not do this amplifier justice.  The best analogy that I can use is to say that I feel sorry for everyone who does not have this amplifier as part of their audio system.  It allows music to flow into the room in a way that I have never experienced before….”

Thank you Randy, that is just the way I felt about your amp. It brings me joy that you have it now.

Here is a recent schematic of the similar 417A RC VT-25 (10, 10Y, 801A) amp. The main difference is that Randy’s amp uses fixed bias, mercury vapor rectification, and the hot russian 6c45p as a driver.

The photo of Randy’s amp is a link to his website…


10 responses

  1. Walter Gammarota

    I like this tube too!
    Is it possible to have the Randall Rash 10y amp schematic?
    Many thanks,

    August 15, 2010 at 5:37 am

    • Hi Walter!
      I have the Type Ten schematic around here somewhere. I will try to dig it up. It is nearly identical to the ‘Luddite 210’ version, but the 6c45p input tube is loaded with a 47K 2W Tantalum film resistor. Bias with a red LED. Fixed bias on the VT-25 finals is mandatory for best imaging. The output transformer is a custom 12K Transcendar, unfortunately Gery @ Transcendar is no longer taking custom orders. Your only hope is to wait until ‘Testedtubes’ on Ebay offers more of the vintage Telefunken OPT. Or perhaps you could have Bud Purvine @ Onetics, or Jack @ Electra-Print Audio wind a pair for you. Let me know of your progress please!

      August 15, 2010 at 6:05 am

  2. Walter Gammarota

    I’ve already built two mono 10y amp.
    I used a 6sn7 as a driver, 10y battery biased (3 x 9v in series), 23 ma and 380v.
    The OT transformers are from Transcendar (10k primry, 12 ohm sec).
    They sound good, but I’d like to try different configurations.
    The next will be using UTC HA 100X as driver. For this I need to find on Ebay two of them, but they are very expensive.
    I look forword to hearing from you.
    Walter from Siena Italia

    August 15, 2010 at 5:34 pm

    • Walter,

      A ‘cheap’ way to get into interstage is to use vintage output transformers back-to-back. The primary of transformer 1 on the plate of the driver tube, the primary of transformer 2 from the final tube’s grid to the neg bias. Then connect the 8ohm secondaries together. You can even use the 8ohm and 4ohm taps for step-up, step-down or 1:1 configuration. Sound is vivid and has great drive.

      Here is an example schematic.

      August 15, 2010 at 10:09 pm

    • Oh ya, I Love battery bias! Parallel batteries for better dynamics 😉 The Cisco SMPS with proper filtration is as good or better for tube finals.

      August 15, 2010 at 10:10 pm

      • Walter Gammarota

        I meant a step up input transformer so the circuit will run only with a tube without any cap or resistor.
        You are a very skilled tube expert, I have many things to learn from you.
        For instance I can’t understand the use of the optocoupler and that of the led in your projects.
        If you can, find out the schematic of Randal amp.
        I look forward to hearing from you.
        Kind regards,

        August 17, 2010 at 4:36 pm

      • Walter,

        The optocouplers have a photoresistor and a LED in one package. Silonex makes then so that they have more closely matched resistance in relation to the LED brightness. They still need to be hand matched for left and right channel balance.

        An optocoupler volume control sounds more ‘real’ than any other type of attenuation. I have rigorously compared optocoulers to potentiometers, integrated circuits, stepped attenuators, and transformer volume controls.

        August 18, 2010 at 5:07 pm

  3. Bob Haythe

    You rascal. You are a hard man to find.
    Email me!

    December 26, 2010 at 12:24 pm

  4. Mark Owens

    Hi there. I love the ingenuity i’m seeing on this site. I too discovered tubes around 1989 and full heartedly believe that the less number of parts the better. I’ve been dreaming about a 10y/vt-25 dual mono- set or push pull, amp for 15 years now.
    What would it take to realize this dream? I have a nice bunch of these tubes. Thanks, Mark

    February 9, 2011 at 12:31 am

  5. zach


    How are you? Very good job on putting this site up. I just stumbled upon your site because I was looking for a 10y schematic,and I think I will build an amp similar to what you made for randall rash.. I would like to know how you implemented the type 83 rectifier’s B+ delay to let the heaters warmup to let the mercury vaporize before applying high voltage.


    June 8, 2013 at 6:26 pm

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