• Classic Valco 6152 circuit
  • Single ended 6V6GT output section
  • 5Y3 tube rectifier
  • Tube driven reverb with Dwell control
  • Tremolo with speed and intensity controls
  • Front panel bright switch
  • Cathode bypass capacitor switch on power tube
  • CTA 6152

    This amp is a custom build I did for a customer. It as based on a Valco made amp from the early 1960's. Around the time this amp was made Valco was the third largest amp manufacturer ( I read that somewhere but can't find the source now). Valco made amps were sold under a number of different brand names, including Supro, National, Wards Airline and Gretsch.

    Here is the schematic : CTA 6152

    It is point to point wired using high quality components including PTFE insulated wire, Sprague 716P capacitors and Carling switches. The tubes (12AX7s and 6V6GT) are the new Tung-Sol reissues except for the 5Y3 rectifier which is a Sovtek. Contrary to popular belief, a tube rectifier in a class A circuit such as this one does not add much tube "sag" ( if any ) because the 6V6GT is always basically drawing the same amount of plate current, unlike a class AB circuit. I say "if any" because there is a slight difference in zero signal and maximum signal screen current draw, but the amount of sag to the power supply is probably inaudible. The 5Y3 does serve the purpose of giving a soft start to the power supply in the original circuit because it doesn't have a standby switch.

    There are allot of controls on the panel for a single ended amp, with the addition of the master volume, intensity control and dwell control, but the added features are nice to have. This amp puts out about 5-7 watts of RMS power, good for practice and recording and even a gig if you miked it. It is pretty clean sounding unless you dime it and use a hot pickup (listen to the JB clip below).

    The dwell control makes the reverb circuit much more flexible. What it does is control the amount of signal entering the reverb pan, which controls the length of the reverberations. The reverb control controls how much of the reverb signal from the pan is mixed in with the dry signal.

    Flipping the switch to add the cathode bypass capacitor to the power tube results in a little higher output and a little more dirt if the preamp and master are turned up. Two of the sound clips below A/B the difference.

    Here is a link to a page I made that documents the building of this amp : Anatomy of an amp build

    If you would like to have an amp custom made for you, please use the "contact" link at the top of this page to send me an e mail.

    Sound clips :

    These clips were recorded with a Jackson solid body. "JB" is short for Seymour Duncan JB which is in the bridge position of this guitar. If a setting is not given for reverb or tremolo, that means they are off for that clip. For all of the reverb clips the preamp is at 11 and the master is at 7. All of the clips have the 6V6GT cathode capacitor engaged except for the one labeled "Dimed no cathode cap". That clip, and the one right after it were recorded with the exact same settings except for the cathode cap : preamp and master at 11. The amp was miked close with a Sure beta 57 and also a condenser mic facing away from the cabinet for room ambience. I was in the mood to noodle when I recorded these clips, if you get bored and want to move on to the next clip then just click on the next one you want to hear.

    Update : Noah, who I made the amp for, recorded some clips and posted them with his review of the amp on The Gear Page. I have added them to the playlist, if you scroll down to the bottom of the list using the arrows on the right of the player you can see them.

    Here is a link to Noah's musical instrument collection. I think he recorded all of the clips with the National except for the one labled "Kustom". In the clip labled "RC" he is using a clean-boost pedal to push the amp into clipping.

    Here is the e-mail Noah sent me after he received the amp :

    Hi Ryan, The amp arrived today, and I couldn't be happier - it's exactly what I was hoping for. It's got all the warmth of the old Valco amps, but with more definition to the notes. Like you said, it's a very clean amp even with the controls dimed, but it takes my overdrive pedal well (as well as a clean boost overdriving the preamp with the master volume turned down). I love how the clean tones still have a hint of grit in them. The bright switch is a neat addition, and I'm amazed at how much extra volume the cathode cap switch gives. With the cap in, it sounds like an amp three times its size! The reverb definitely sounds better than the original, and the dwell control really does help. Thanks again for your time and effort. You can use any of this if you need a testimonial for your website, and I'll be writing up a similarly favorable review on TheGearPage.net. Take it easy, -Noah