Hi, How is the bass response with the Bugle SE 45 , the coupling cap in the original schematic ( 0.067uF @ 5Hz ) or even (0.047uF uF @ 7.2Hz ) suggested looks to small , and the -3dB corner frequency with a 3Hz roll off with a 470K load resistor on the grid of the 45 would suggest a 0.11uF capacitor size ( 0.1uF would be OK ), 0.22uF is not necessary and would likely slow the amp down recharging the cap on heavy dynamic demand in the bass region .
Bugle 45
- Thread starter Tsingtao_1903
- Start date
Sorry, have not touched the 45's in quite a while. Can't recall. I've been playing around with various drivers, horns and amps.
Hi there,
Did anyone measure the input sensitivity for this amp? I built one last year (with some mods from the author's advice) and I'm trying to match a line pre to put between my phono stage and the Bugle. I don't have an oscilloscope to measure the sensitivity properly. Thanks!
By the way, this is my version of it with Gordon's suggested mods; not mono blocks, but I insisted on keeping PSU and signal well separated. Testing a new build
Did anyone measure the input sensitivity for this amp? I built one last year (with some mods from the author's advice) and I'm trying to match a line pre to put between my phono stage and the Bugle. I don't have an oscilloscope to measure the sensitivity properly. Thanks!
By the way, this is my version of it with Gordon's suggested mods; not mono blocks, but I insisted on keeping PSU and signal well separated. Testing a new build
What are the mods Gordon recommended?
Mostly choke and cap configuration on the PS side. The updated schematics are in the post I linked to above (sorry, I'm traveling and I don't have the original to repost here). I never listened to the original design so I can't compare side by side, but I'll take Gordon's advice at face value.
The 100V chokes are Hammond. I had to hack them into a vertical configuration because they were bigger than the original 40V ones, which were running very close to capacity, and wouldn't fit in the chassis. I removed the frame, ordered end bells to size, and insulated them with thermal varnish.
The 100K pot on the signal was my addition—bad idea, because I thought I could drive my phono stage straight without a pre, which is not the case. That's why I'm looking for one right now to match with the Bugle's input sensitivity and the phono output (~500mV).
Also, I didn't have a reply from Heyboer so I used Edcor power and filament transformer, and I got hold of a pair of early-production One Electron UBT-2 OPTs. The schematics are drawn with those tx in mind.
I obviously meant 100/40 mA.
I actually bought two pairs of the power transformers from Heyboer just because. Should anyone ever need a pair, let me know, I'll let them go for what I paid plus shipping.
You do not need a scope to measure input sensitivity. A DVM set to AC volts will measure a 60Hz test tone. Put your meter probes across the speaker jacks and turn up a 60Hz test tone until you see 4V at the speaker posts (2W into 8 ohms), then power down the amp, pull the RCA cables out of the amp and use your DVM to measure the signal voltage going into the amp. That will give you input sensitivity and you can also calculate the gain of the amp from those numbers.
