View Full Version : Valve amp/preamp with tone controls
Hello,
I’d like to experience valve amplification.
Tone controls required.
Wattage maybe from 10W.
If not amp, then preamp for the beginning.
Initial price about £500.
What would be your suggestions?
List of some options here, no idea what any of them are like though:
https://hotproducts-2020.com/10-best-tube-preamp-with-tone-control/
Lawrence001
28-05-2020, 16:19
No mention of this amp which I owned last year. Sounds very transparent but needs upgraded valves. It has a slight foible that the tone controls are neutral at about 10pm/2pm and the direct switch seems to engage a loudness compensation circuit!!
https://www.ebay.co.uk/itm/263613175482
scotty38
28-05-2020, 17:41
No mention of this amp which I owned last year. Sounds very transparent but needs upgraded valves. It has a slight foible that the tone controls are neutral at about 10pm/2pm and the direct switch seems to engage a loudness compensation circuit!!
https://www.ebay.co.uk/itm/263613175482
I'll take a stab at engaging the tone controls drops the gain to give headroom for "increasing" bass and treble so defeating the circuit gives you the normal gain level back.
Lawrence001
28-05-2020, 20:08
Theres a bit of talk on the forums about the loudness issue (I mean a Fletcher Munson type circuit not just volume level). This thread has a link to some oscilloscope readings, the engineer said he measured bass and treble +7db when engaging the source direct button [emoji23]
https://audiokarma.org/forums/index.php?threads/xiang-sheng-728a-preamp-drawing-attempt-for-a-schematic.832242/
Despite this, with the tone controls switched on and set to flat about 10pm/2pm as in the link in the link) it sounds great [emoji38]
Stick a klark teknik dn360, dn370, in the tape loop or between the pre.power amp. Way better than bass and trebble knobs
Some interesting choices, thank you.
Before I was thinking about Schiit Loki connected between source and preamp, that would give me just one input solution though.
It could work though if connected in the between preamp and power amp though, good idea.
Many frequencies equalisation unit might be too much in the signal path, hm..
Will have a look at the 728A preamp, looks nice.
No mention of this amp which I owned last year. Sounds very transparent but needs upgraded valves. It has a slight foible that the tone controls are neutral at about 10pm/2pm and the direct switch seems to engage a loudness compensation circuit!!
https://www.ebay.co.uk/itm/263613175482
So I decided and ordered one with tone controls and remote control. What tubes are in need of replacement in that preamp and what was your choice for new ones?
Lawrence001
02-06-2020, 13:29
So I decided and ordered one with tone controls and remote control. What tubes are in need of replacement in that preamp and what was your choice for new ones?I didn't know they did a remote version. The valves are 2x12AT7, 2x12AU7 and 1x6Z4 IIRC.
The 6Z4 is a Chinese or Russian rectifier with no Western equivalent l think but it's decent enough anyway so you don't need to worry about that. I went on eBay and ordered some reasonably priced NOS valves for the other types, possibly Philips and something else. Depends how much you want to spend, they're not as pricey generally as 12AX7 fortunately.
Yes, there is the version with remote control too, I like that.
Touching those valves, tried to dig into the world of just the two - ECC81 and ECC82 and quickly became overwhelmed by amount of manufacturers and various specs and model names, then the term NOS created a lot of questions in my mind too. After browsing various reviews and eBay offers I think I will try some, but from different source.
Watford valves is UK company in this business, so probably will buy from them. Better to be assured that the valves are properly tested and matched. I guess that will help with evaluation whether it was worthy to try 😎
Lawrence001
02-06-2020, 21:58
Watford have got some good value NOS ECC81s for £10 and under. For the 82s buy a pair of these
https://www.ebay.co.uk/itm/153832613624
Thank you, added to watch list.
Finally bought the XiangSheng 728A III.
Got it from eBay, seller cybereveryday with feedback over 3000, his name is Honach and is responsive and open. I guess this is later incarnation of original 728A. My requirements were UK 240V, black colour, tone controls and remote control. Although that one wasn’t listed, Honach was able to provide exactly what I wanted. And dispatch it quite quickly. This is just for info about eBay seller from China, as people can be hesitant to buy from unknown sources, so cybereveryday seller is perfectly fine. The preamp came in box with cheaper foam filling, but sufficient to safe transport. The price was $405 which is about £324 plus £32 shipping, in addition customs fee about £16 don’t remember exactly. The remote control is also cheap small with input source selector and volume control. The preamp has digital display showing which input is active, under it two buttons to choose the input from preamp itself. It has bass, middle and treble controls and push button to direct signal. Means nice touch with the extra mid frequency adjustment, unfortunately no balance control. That I didn’t specify anyway, maybe such choice would be available, don’t know.. At the back there are 4 pairs of source inputs and 2 pairs of preamp rca outputs, quite handy.
Running it about week- two weeks, not sure how many hours, wanted to reach first 100 hours for tubes to open, but even now it is transparent sounding preamp, I have to say I am happy with what I hear.
In the present, the chain is - the source Marantz SA8005, WireWorld Equinox 7 interconnects, XiangSheng preamp, silver (tweeter side) and Oehlbach interconnects to Rotel RMB1066 power amp used in biamp mode to KEF Q500 speakers using QED pure copper Q tube (tweeter side) and Ruby speaker cables. It is musical set up, with enough of details, nice soundstage and balanced sound from top to bottom for my small room. Recommended to try this Chinese preamp.
Also I didn’t notice any bass or other boost when tone controls disabled, seems the sound has the same signature and strength with tone controls engaged in 0 position as with direct signal path. Slight difference in clarity is there though, that’s what is expected.
And the last, for now I am happy with it as it is, so no urge to change the valves 😎
Is it this one? https://www.china-hifi-audio.com/en/popup_image/pID/1353?zenid=137e365bad53d0cb091aae453e6bb902
Basically yes, just noticed mine has model number 728III on front panel instead of 728A. More like on hifi exquis web site:
https://hifi-exquis.com/en/tube-pre-amplifier/65-xiangsheng-728a-tube-pre-amplifier.html
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