Bob's Vacuum Tube Audio Projects Page
last update 04/09/02
Little Guitar Amp: (04/04/02)
The schematic for this little guitar amp is shown HERE.
I built this little guitar amp for my brother, Rich, a while back. Originally it was sort of a Fender "Champ" copy with a 12AX7 front end. I recently converted it to use a single EF86 pentode, instead. I like it much better this way. The amp chassis fits into a small maple open-back box with a single 10" speaker. Rich built the box...
I'll add Pictures, someday...
Bass Guitar Amp: (04/02/02)
This is a work in progress. Preliminary schematic is shown HERE.
I've been wanting to put these EL509's to use!!! Figured a nice high-power bass guitar amp would be a perfect application.
I have the amplifier built to the point shown in the schematic, above. Initial testing with tone-stack replaced with a 10:1 voltage divider is very promising.
Still need to decide on the tone stack arrangement. The unit is built as a stand-alone head, and will be used with a Peavey 15" + 2x 10" Bass cabinet.
Yet another Single-Ended 300B Amp: (03/16/02)
The schematic for my latest SE 300B amp is shown HERE.
The power supply is shown HERE.
This was an attempt to get the "magic" sound of my "Darling"
SE 1626 amps but with significantly higher power. In any event, the 1626 does make a nice low-mu, high current driver for the 300B. The choice of paralleled 5965/12AV7 in the input stage was mainly driven by pre-existing 9-pin sockets in the amp chassis. So far, this has worked out well.
Low Power Single-Ended 6SN7 Amp: (3/12/02)
The schematic for the SE 6SN7 amp is shown HERE.
The schematic for the power supply is shown HERE.
I built this little amp for my computer at work. It sounds pretty darn good thru some old speakers from an Emerson tube console. At <1/2 Watt it is STILL too loud for my office.
Hope to have some pictures, soon, as it looks very cute - Like a 1/4 scale version of a 300B amp...
Class A2 SE 812A Amp: (3/6/02)
The schematic for the SE 812A amp is shown HERE.
The schematic for the power supply is shown HERE.
This Amp is a variation on the SE 826 amp, below. It uses positive grid bias derived directly from the cathode follower driver stage. The 6F8-G driver/input tube was chosen because it biases to the required voltage (+14V) for the output stage's bias. (Note that the 6F8-G can be replaced with a 6SN7. I just happen to like the looks of the 6F8-G better...)
UPDATE (6/4/02)
I got the opportunity to show this amp off at the nyNoise 2002 show.
HERE is a direct link to a picture to my SE 812A amp on Steve Rochlin's Enjoy The Music web page.
Push-Pull 6L6 GUITAR Amp: (3/2/02)
The schematic for the guitar amp is shown HERE.
Returning to my roots...:)
I decided to try another guitar amp (actually, I intend to build two identical single 12" combo's - one for me and one for my TWIN brother, Rich). Although I'm sure a Fender Deluxe knock-off would be just fine for what I needed , I wanted to do something a bit different.
So my new amp is based upon an old Silvertone Twin Twelve.
Class A2 SE 826 Amp: (2/28/02)
The schematic for the SE 826 amp is shown HERE.
The schematic for the power supply is shown HERE.
This Amp was an attempt to create a nice Class A2 power amp, similar to the SE 833 amps, described below, but without a 10:1 step-down transformer.
Instead, it uses a choke-loaded cathode follower to drive the output tube. It uses positive grid bias derived directly from the cathode follower driver stage. The 6F8-G driver/input tube was chosen because it biases to the required voltage (+14V) for the output stage's bias. (Note that the 6F8-G can be replaced with a 6SN7. I just happen to like the looks of the 6F8-G better...)
UPDATE (6/4/02)
I got the opportunity to show this amp off at the nyNoise 2002 show.
HERE is a direct link to a picture to my SE 826 amp on Steve Rochlin's Enjoy The Music web page.
Push-Pull 6Y6 Stereo Amp: (1/29/02)
The schematic for the PP 6Y6 amp is shown HERE.
This is a pretty straightforward PP amp design except for the unique positive feedback from the phase-splitter cathode to input stage cathode. 12 Volt input tubes were used because this amp is going to be used in my CAR (with a 250V switching power supply for B+). More info will be added as time permits.
Yet another Single-Ended 2A3 Amp: (10/14/01)
The schematic for my latest SE 2A3 amp is shown HERE.
This amp uses a 6C45pi input tube loaded by a 1:1 Interstage Transformer
(I used the inexpensive model available from Allied Electronics). The 6C45pi is supposedly not rated for more than 200V on the plate, but I have not had any trouble with 300V in this application. You may not wish to follow in my footsteps if you paid a lot for your 6C45pi's...
Class A2 SE SV572-160 Stereo Amp: (1/23/01)
The schematic for the SE SV572-160 amp is shown HERE.
This amp uses a 6BM8 drive stage similar to the big 833A amp below, except it utilizes CATHODE drive. I presently have this amplifier set up so i can adjust the grid bias from about +2V to +30V. There is also a switch that connects the output tube grids to ground (0 Bias) instead of the grid bias supply. This way i can experiment with various output tubes, including 811A, 812A, SV572-10, SV572-30, SV811-10, etc. So far, i think the SV572-160 sounds best in this amp. I think it is because of the cathode drive (also called grounded grid) topology. I think i like the medium mu transmiting tubes, like 812A, 826, SV572-30 in grid drive amplifiers better. But in this amp, the 572-160 can be "dialed in" to a nice sweet-spot that sounds great!
Class A2 SE 833 Stereo Amp: (3/27/01)
The schematic for the SE 833A amp is shown HERE.
The schematic for its power supply is shown HERE.
Full Description to follow shortly.
This amp was featured at the 3rd annual nyNoise
2001 Audio Show. .
Stereo Push Pull 3CX300A1 amplifier. (4/11/00)
The schematic is shown
HERE.
At some point I will add some detail for this amp, but it is loosely
based upon my "Beast"
amplifier,
referenced elsewhere on this page.
This amp was featured at the 2nd annual nyNoise
2000 Audio Show.
Tube Car Stereo Amp (3/27/01)
YES, a tube amp in a CAR!!!
Full web page HERE
This amp was featured at the 3rd annual nyNoise
2001 Audio Show.
Solid State Power Op-Amp Amplifier (10/14/99)
LM675 Amp Schematics, only. This was my minimalist interpretation of the so-called "Gaincard" amplifier. It uses the minimum number of parts I could get away with. All parts are directly soldered to the IC leads for minimal stray inductance. It works and sounds suprisingly good!
Single Ended 5687 Amplifier (6/25/99)
This has become a very popular set of amp designs. They are all based upon
the 1626 Triode output tube and the philosophy to keep things SIMPLE. I
am continually amazed how good these amps sound for what they are. The
name "Darling" came from a good friend's description of my original design.
It looked like a miniature version of "full-sized" SE 300B. The name stuck...
Click HERE
to find out more...
This amp was featured at the1st annual nyNoise
1999 Audio Show.
NEW 3/25/02:
There is even a FAN club for the "Darling" Amplifier. Click
HERE.
DC Coupled Phono Preamp
Schematic,
Only RIAA Preamp based upon the classic RCA
12AX7 design.
Using 6SL7 instead, and DC-coupling of the two stages.
FULL WEB PAGES of OLDER PROJECTS:
Help me choose my next project and see
what Bob's up to...
Email Bob. D. at robert.m.danielak@lmco.com
This page Copyright (C) 2002 Bob. D.