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Bias Bench
Fiksni i katodni bias, push-pull i single-ended pojačala, uz obračun struje ekranskog grida i pada napona napajanja. Matematika sa tech stranica, urađena umesto tebe.
Visok napon — prvo pročitaj ovo
B+ šina u lampašu drži 400–500 V DC i to te može ubiti. Filter kondenzatori drže taj naboj minutima — ponekad satima — nakon što se pojačalo isključi iz struje. Pre nego što rukama priđeš šasiji: isprazni kondenzatore preko bleeder otpornika, pa multimetrom proveri da je B+ pao na bezbedan nivo. Drži jednu ruku u džepu dok meriš na pojačalu pod naponom. Ako ti bilo šta od ovoga nije poznato, ovo nije posao na kome to treba da učiš.
Setup
Push-pull · Fixed bias · 6L6GC · ×4
Measure DC voltage between the OT center tap and each plate (outer winding end). You'll also need each half's DC winding resistance and the B+ voltage at the center tap.
Datasheet reference
Pd max 30W · Pg2 max 5W✓ sourced
Datasheet typical (fixed bias, PP): 450V / 58mA per tube → 26.1W
RCA RC-30, pp.353–354 (Design-Maximum rating)
Tube count
Measurement grouping
"Shared per side" is the standard method: measure CT-to-plate drop across each OT half. Individual only applies if this amp has dedicated per-tube test points.
Measurements
Power supply sag — optional
B+ isn't a fixed number — it droops as total current draw rises, because the supply (choke, dropping resistor, transformer/rectifier regulation) has its own source impedance. This only matters for "set a target" measurement points below: it corrects the required voltage for the fact that B+ will be lower once the bias is actually brought up to that target than it is right now at the current (measured) draw.
Estimate it from your supply's choke/resistor DC resistance plus rectifier regulation, or from two real B+ readings at two different current draws: Rsource ≈ ΔB+ / ΔI.
2 tubes
2 tubes
Screen grid (Vg2) — optional
Fill this in if screen voltage runs noticeably below B+ (power-scaled/variable-Vg2 designs) or you want screen dissipation checked independently. Leave blank for a plain pentode/tetrode running screen straight off B+ — it's not needed for the plate-dissipation numbers above.
Results
6L6GC · Push-pull · Fixed bias · Quartet (4) · Shared per side (2 points)
Enter B+ and each measurement point's resistance/voltage above — or set a target — to see results.
Bias target threshold
A common conservative target is 60–70% of rated dissipation for tube longevity. 100% is the datasheet's absolute figure, not a safety margin.
Operating point
Amp profiles & history
Saves winding/resistor values and tube setup — not today's voltage readings, so you're prompted for fresh measurements every time you re-bias.
Reading history
No saved readings yet.
Backup
Tube ratings sourced from datasheets where noted; unverified entries are flagged. This tool estimates dissipation from your measurements — it does not replace datasheet judgment or amp-specific service literature. All data stays in this browser; nothing is uploaded.
Odakle ovo dolazi
Metoda iza brojki
Bias Bench koristi metodu merenja otpora izlaznog transformatora — bezbedniju od stavljanja multimetra u seriju sa strujom anode, i odmah iza osciloskopa na dummy load-u. Ceo postupak sa radnog stola, sa matematikom razrađenom korak po korak, opisan je ovde.
Još sa radnog stola
Druga polovina pojačala
Bias određuje kako se ponaša izlazni stepen. Ono što do njega stigne već je oblikovano tonskom kaskadom — a to kolo je tamo gde zapravo živi najveći deo karaktera pojačala. Tone Stack Lab to crta uživo, sa pravim vrednostima komponenti iz 55 pojačala i pedala.
Besplatno, i tako ostaje
Ako ti je ovo uštedelo put do radnog stola, pomozi
Bez naloga, bez paywall-a, bez reklama — i to se ne menja. Jednokratni prilog pokriva vreme na radnom stolu, opremu za merenje i hosting koji omogućavaju besplatne alate poput ovog.