Dedicated to HH Scott Vintage Vacuum Tube (or “Valve”) audio equipment.
*Safety Third! 🙂
Consider this the usual “people safety” disclaimers: High voltage is very dangerous, I’m not liable for you or your gear or anything, this is just advice, etc. There’s lots of information on high voltage safety on the net; find it, read it, understand it, practice it.
*An “in-joke” I won’t explain. Look it up.
There is also the unit’s safety to consider. Many of the key parts are no longer available, so don’t melt or smoke your amp! And be extra careful with the knobs and faceplates!
A few HH Scotts from my collection:
Some of my HH Scott amps and tuners
The 350’s faceplate (lower right) is not bent, just weird lighting!
Community and More Info:
HH Scott Tuners:
This is my rambling, never quite completed, but still fairly useful history of Scott Tuners. It covers several decades of tuners, and contains a lot of practical experience in repairing, restoring, and aligning them. I did a cleanup pass in mid-2020, it’s at version 0.97 now. A downloadable PDF file: hhscott tuner alignment-97
HH Scott Amps:
LK-150 amp: Scott LK-150 Amp (and rebuild notes)
LC-21 preamp: Scott LC-21 Preamp ( and rebuild notes)
A handy guide for HH Scott amplifier output transformers and tube idle currents (i.e. “bias”). Observe some amps can only set the idle current as a pair; they expect plate current matched output tubes. (I often modify these to a per tube bias control, which then allows use of unmatched output tubes.)
Note: these are the factory settings for max power output.
Given the expense and scarcity of good output tubes, I suggest about 10% less idle current to extend output tube life.
| H.H. Scott Model | Power xformer | Idle current in mA per tube/pair | Output Tube type | Output xformer | Rated WPC |
| 200-B/LK-30 | TR 12-12-1 | 17.5 / 35 | 6GW8 | TRA 8-6 | 12 |
| 208 pwr amp | TR 13-3-2 | 35 / 70 | 7591 | TRA 11-2 | 32 / 36 |
| 222(A) | TR-12-7 | 6BQ5 | TRA 7-1 | 15 | |
| 222-B | TR 12-7? | 6BQ5 | TRA 7-1? | 15 | |
| 222-C | TR-12-3-2 | 22 / 44 | 7189/EL-84 | TRA 8-5-1 | 24 |
| 222-D | TR-12-13 | 22/44 | 7189/EL-84 | TRA-8-5-1 | 24 |
| 233 | TR-13-3-4 | 32.5 / 65 | 7591 | TRA 8-5-4 | 28 |
| 272 | TR-30-5 | 55 / 110 | 6CA7/EL-34 | TRA 12-2 | 37 |
| 290 | TR-30-4 | 55/110? | 6CA7/EL-34 | TRA 12-2 | 50 |
| 296 | TR-30-6 | 7581 | TRA 12-2-1 | 50 | |
| 299 (A) | TR-12-3-1 | 27.5 / 55 | 7189/EL-84 | TRA 8-4 | 21 |
| 299-B | TR-12-3-1 | 27.5 / 55 | 7189/EL-84 | TRA 8-5 | 21 |
| *299-C | TR-13-3 | 35 / 70 32.5 / 65 | 7591 | TRA 11-2 TRA-8-5-4 | 31 / 28 |
| 299-D | TR 13-3-2 | 35 / 70 | 7591 | TRA 11-2 | 34 |
| LK-48(A) | TR-12-3-1 | 22/44 | 7189/EL-84 | TRA 8-5-1 | 20 |
| LK-48-B | TR-12-13 | 22/44 | 7189/EL-84 | TRA 8-5-1 | 20 |
| LK-72(A) | TR 13-3 | 35 / 70 | 7591 | TRA 11-2 | 35 |
| LK-72-B | TR 13-3-2 | 35/70 | 7591 | TRA 11-2 | 35 |
| 340 (A) – rcvr | TR-15 | 32.5 / 65 | 7591 | TRA 8-6 | 27 |
| 340-B – rcvr | TR-15-2 | 35 / 70 | 7591 | TRA 8-5-3 | 30 |
| 345 – rcvr | TR-15-2 | 35 / 70 | 7591 | TRA 8-5-3 | 29 |
| 380 – rcvr | TR-15-2 | 35 / 70 | 7591 | TRA 8-5-3 | 32 |
| LK-150 pwr amp | TR-30-4-2 | 60/120 | 6550A/KT-88 | TRA 15-2 | 58 |
* – A significant production run change here. Later 299-C amps actually had 233 circuitry and the smaller TRA-8-5-4 transformers, so bias like a 233.
I wrote a mostly finished “white paper” on the theory and the practical aspects of setting output idle current via a negative bias voltage.
Applicable broadly, but specific to Scotts. bias-notes.pdf
Some Vintage Resources: (Links active as of 2020.06)
Rebuild and Service: NOSValves
Rebuild and Service: Classic Tube Audio
Tube supplier: Doug’s Tubes
Tube Supplier: Radio Electric Supply (RES)
Tube Supplier: The Tube Store
Parts and Tubes: Antique Electronics Supply (AES)
Capacitors and resistors: Just Radios
Last Updated on 2023-11-02 by Daev Roehr