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In Reply to: RE: Yes, with DHTs hum can be an issue posted by Tre' on February 16, 2025 at 20:39:48
Finally got the preamp on the CRO. With the 300K/100K config, through the DIY shieldless cable (175pF), the upper 3db point was 19khZ into 100K. But, taking the 68K/22K suggestion lead to a much better upper 3db;- 37khZ. Not only that but the preamp was even quieter. One channel reading 0.0mV! Plaid all afternoon and throughly enjoyed it.Gain though is only 3db but these are power tubes so what do you expect? It will deliver 4Vpp into 100K. My DIY SE UL EL34 amp has plenty of gain so no concern. Not only that the two are a perfect synergy. Love the sound of this 6N7 preamp and love the metal tubes.
| retro-thermionic |
Edits: 02/26/25
"With the 300K/100K config, through the DIY shieldless cable (175pF), the upper 3db point was 19khZ into 100K. But, taking the 68K/22K suggestion lead to a much better upper 3db;- 37khZ. Not only that but the preamp was even quieter. One channel reading 0.0mV! Plaid all afternoon and throughly enjoyed it.
Gain though is only 3db but these are power tubes so what do you expect? It will deliver 4Vpp into 100K. My DIY SE UL EL34 amp has plenty of gain so no concern. Not only that the two are a perfect synergy. Love the sound of this 6N7 preamp and love the metal tubes."
6N7? Metal tubes? Huh?? Isn't this thread about a 01A preamp?
Looks like I got my threads mixed. But I've had the same problem over four different preamps based on the 01a, 71a, 6N7 and 12AX7 preamps. Forgive the mixup but the result (good result) hopefully will be the same.
| retro-thermionic |
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