Thanks batteryman, that makes so much more sense to me now.
I disconnected the Rnf / Lnf from the board to diagnose, and now I've got a much cleaner, but also weaker signal. I will check if I mixed up resistors somewhere.
I disconnected the Rnf / Lnf from the board to diagnose, and now I've got a much cleaner, but also weaker signal. I will check if I mixed up resistors somewhere.
I'm thinking about getting a cheap valve amp to play around with, what would you recommend in this price range? Any specific amp/seller, based in Europe?
I have not played around with tube amps, but built and modified a number of solid state amps, so looking to learn something about valve amps with a cheap project, measure, and maybe listen if I like the sound of it..
I have not played around with tube amps, but built and modified a number of solid state amps, so looking to learn something about valve amps with a cheap project, measure, and maybe listen if I like the sound of it..
If you only need 8-10watts, this SE amp is the one I bought off ebay:-
https://www.ebay.co.uk/itm/275902195982
Measure it with REW or similar and then read about the mods on my thread in the link. (post #93)
https://www.ebay.co.uk/itm/275902195982
Measure it with REW or similar and then read about the mods on my thread in the link. (post #93)
"this SE amp is the one I bought off ebay:-"
UK, no shipping to European countries!The amplifier described in this thread is available here, shipped from Germany --->
https://www.ebay.de/itm/274138590648
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I built the PP amp in this thread 3 yrs ago. It was a good starting point to enter the tube amp field.
The amp in thread below has good specs- 20-28k, but @ what dB is unknown. IMO price is reasonable-
https://www.aliexpress.us/item/3256802532801472.html
Post #242 builder is happy with the results, otherwise I would not mention for consideration.
https://www.diyaudio.com/community/...e-i-build-maybe-during-if-i-do.394962/page-13
Jim
Thank you for the replies! The amp in this thread seems to be the cheapest to buy and available in Europe, but maybe there is a lot to be spent to get it performing well? Seems a lot is wrong with the original design.
Maybe getting a used amp locally would be a better alternative?
I have too many projects, it might be left sitting in a box and never finished too 🙂 I need to think about it a bit, too easy to press the 'buy' button!
Maybe getting a used amp locally would be a better alternative?
I have too many projects, it might be left sitting in a box and never finished too 🙂 I need to think about it a bit, too easy to press the 'buy' button!
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Burning amp !!
If you want the simple and inexpensive "tubes" sound, find yourself a Marantz 1030 (transistors inside) otherwise, a Harman Kardon A300 (6v6/7408 inside) still the most user-friendly amp I own
In Germany this amplifier is available again with a big discount, which makes the offer almost irresistible (it is also available for shipping to Sweden but with slightly different conditions) 😉
I have to ask DOUKMALL directly about an advertising commission 😆
"and the voltages are a bit scary too.."
a 100K 2w discharge resistors across the 330µf in the power supply circuit works wonders, at least when the power plug is disconnected 😉
https://www.digikey.de/en/resources...version-calculator-capacitor-safety-discharge
And I would definitely install series resistors in the heating system. This protects the tubes and limits the load on the power transformer !
https://www.diyaudio.com/community/threads/problems-with-chinese-pp-kit.353111/page-5#post-7473748
"and the voltages are a bit scary too.."
a 100K 2w discharge resistors across the 330µf in the power supply circuit works wonders, at least when the power plug is disconnected 😉
https://www.digikey.de/en/resources...version-calculator-capacitor-safety-discharge
And I would definitely install series resistors in the heating system. This protects the tubes and limits the load on the power transformer !
https://www.diyaudio.com/community/threads/problems-with-chinese-pp-kit.353111/page-5#post-7473748
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I illustrated the PCB changes a bit, added 1k gridstopper resistors and changed the NFB circuit
Has anybody made a LTspice sim of this amp? I think that would be useful for simulating mods etc.
DC voltages look close in simulation, the input pentode voltages are a bit off, I use a 6U8 (ECF82), not sure how close is to the Chinese 6F2, and for the 6P1 I use a 6P1P-EV model found here in the Spice models' thread. I also used an 8K:8 OPT, not sure which one is required.
