Those improvements..are they also possible on a 337?
- 5,167 Posts. Joined 9/2011
- Location: The Netherlands
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Are you the owner of Darkvoice? These are GREAT amps, you really deserve a round of applause for making these great sounding amps for us all to enjoy. I Love my 337, with tung sol 5998 and mesh screen valves.
Amazing amps, and outstanding dollar value too.
Yeah..my 337 has ts 5998 and ts as7gt mesh plates also..perfect!!
Your English is very good through translator.
I use google translator when I read your Chinese headphone forums... seems to work very well.
thank you for building excellent amps.
CCS requires an external voltage source, and as you see there is not, the white box is connected the same way as the cathode bias resistor BTW CCS is belong to fixed bias group
My old 337 MOD
337 MOD RMAA
My 339 Reference (Before)
339 Reference RMAA (Before)
339 Reference Frequency Response 2496 (Before)
339 Reference Stereo Crosstalk 2496 (Before)
Resistors, Diodes, RCA Sockets and Circuit were different, the other parts no changed.
THD and IMD, LF339 is less than half as DV337!!
I think the reason is for the circuit, LF339 is more concise than DV337.
If some people don't know what's difference with them, maybe the post is useful.
339 is more potential platform.
339 Reference make me don't want to sleeping, really very good sound.
The "white box" could be called Fixed Bias, all the current version of lf339 is using fixed bias method in the cathode circuit.
I bought my amp before it so my amp was self biased, if I got one definitely I would open it and check it out.
I bias the input stage tubes with resistor, RC bypass, LED and finally with the rechargeable cell. The first two methods are self biased the LED and the rechargeable battery is fixed bias.The advantage of the RC bypass, LED or battery over a resistor is that the stage will have higher gain.
All the method sound better then cathode resistor itself I'm still impressed with the sound LED biased cathodes or RC bypass but none have come close to the difference of putting a battery for cathode bias. Battery bias kept the dramatic improvement in the bass and improve the presentation in the mid and upper range.
BTW, very nice shot I hope, u get the adapters working soon :))) and do some picture, ceramic base and teflon socket it may look cool!
Thanks for the info man, I remember at the time I was upgrading I switch this white box for a 1K resistor and I immediately felt the sound had degraded.
I'm sorry I couldn't help you more about discovering whats Inside, but I couldn't open this box and only found that theres a resistance of exactly 1Kohm between the lugs (if memory serves). No voltage so I presume it's not a battery.
I strongly suggest you try to upgrade you DK339 to fixed bias, the improvement is not that subtle to my ears!
Im waiting for the parts to arrive, hope the ceramic base are well made ^^ , and the Tungsol 6SJ7GT will sing again!
I will try to run measurements with the programs you mentionned, is it hard to do?
My amp was modified a little bit since, I use russian gigantic teflon caps and paper in oïl for the output coupling bypass and the sound is very good. Anyway, anyone with any variants of the 339 will tell you this amp sounds good hehe ^^!
I totally agree! This amp was such fun to upgrade, the base circuit is beautifully sounding to begin with! Thanks for your reference amp that helped us a lot in modding our own amp. Kudos to you and the Boss!
Holy capacitance batman!! (American expression, from an old TV series).
I thought about doing something similar to my 337, I would have had to add an entire bottom chassis (metal enclosure) beneath the amp just to house the coupling capacitors. I would have needed ~250-300mfd at ~400-450V. It just wasn't practical. I could have used low-ESR electrolytic too, electrolytic capacitors are less than half the volume for equal specs. I chose to add an output transformer instead, happy with the result... GREAT sounding amp!!