In Reply to: Doc's fiendish reel to reel experiments posted by heideana on November 1, 2006 at 02:05:33:
Not to denigrate Doc B's tubed Seduction NAB tape preamp efforts in any way; but I just did another 1500 mod for a customer that worked out REALLY well.Added a new set of high quality RCA's on the back next to one pair of existing (cheap) paralled line output jacks. Wired a shielded cable from it directly to the output of the tape preamp section in parallel with R197 just before the monitor select switch. When this switch is in the "source" position, the tape preamp output is disconnected from the rest of the circuitry. Also changed C151 to a high quality mylar and C's 159 and 193 to Elna Cerafine's. Tape preamp is a decent simple design. IEC equalization can also be switched in via transistor TR128. (the 1500 doesn't have the switching to enable it however).
Sounds REALLY nice, although the gain is down about 15 dB from the main output jacks - about the same as from a Seduction. Don't have a way to compare them but bet it would be close. So you do need to feed the signal into a preamp with 15dB or more of gain and an input impedance of at least 10K ohms.
"Tweaked" 15ips response is within 2dB from 35 hz to 20kHz (upper limit of my Sound Technology 1500A). 7 1/2 response within 3dB from 35hz to around 18 Khz. NOT shabby! Record sounds VERY good also - with better line input jacks and better caps. Record/playback response tweaked to same as above. Power supply voltages to the electronics are regulated.
Keep your heads clean and your tails out!
Charles King
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Follow Ups
- Suggested Technics 1500 mod - stellavox 06:26:28 11/01/06 (2)
- Re: Suggested Technics 1500 mod - ironbut 16:15:31 11/01/06 (1)
- Re: Suggested Technics 1500 mod - stellavox 03:50:42 11/05/06 (0)