Just to add - in reply to the phono input question from 861147, it is not worth relying on as it is a very basic op-amp one. You would be better to use an external dedicated pre-amp. It would probably serve just to be able to listen to your vinyl to start you off. Usual practice is to bypass the pre-amp and create another line input.
The Peach sounds pretty good though, despite the limitation of the output transformers but you will really need some mods done to get it to perform.
The Peach sounds pretty good though, despite the limitation of the output transformers but you will really need some mods done to get it to perform.
Noob question. I've done some of the mods in this thread (caps changed, small caps removed, changed tubes to 6n6P, 6n1p, GU50) succesfully and without electrocuting myself.
Now I would like to adjust the bias for the GU50s. I know where and how to meassure. What I don't understand is the procedure: to adjust and to meassure, the amp has to be on. But how should I put a load on the output, my loudspeakers are far away from my workbench. Would attaching 6ohm resistors to the output contacts do?
I hope someone can explain the procedure ...
Now I would like to adjust the bias for the GU50s. I know where and how to meassure. What I don't understand is the procedure: to adjust and to meassure, the amp has to be on. But how should I put a load on the output, my loudspeakers are far away from my workbench. Would attaching 6ohm resistors to the output contacts do?
I hope someone can explain the procedure ...
Hello Alphy,
Yes, it does.
That's the way I measure the amp performances.
Note that the load is only required at power on, to make sure that the transients in the transformer will not result in an over voltage condition on the tube.
So it can be of little wattage (as long as you do not play any signal with the amp).
Make sure that the pot is set to minimum (no signal).
If you do not exceed 85mA, it should be fine.
Enjoy.
Yes, it does.
That's the way I measure the amp performances.
Note that the load is only required at power on, to make sure that the transients in the transformer will not result in an over voltage condition on the tube.
So it can be of little wattage (as long as you do not play any signal with the amp).
Make sure that the pot is set to minimum (no signal).
If you do not exceed 85mA, it should be fine.
Enjoy.
I'd recommend aiming for 50mA for the GU50s, they work well there and it balanced power and transformer saturation, and the heat given off by the mains transformer.
To bias turn the volume to minimum, keep speakers disconnected, be very careful of voltages and make sure you measure the right bits on the right scale!
You need to be across the cathode resistor (10ohm) and get about 0.50V there.
Do each in turn and then repeat to verify.
To bias turn the volume to minimum, keep speakers disconnected, be very careful of voltages and make sure you measure the right bits on the right scale!
You need to be across the cathode resistor (10ohm) and get about 0.50V there.
Do each in turn and then repeat to verify.
Thanks Globulator! I haven't found the time yet to do this. Funny you should mention the heat of the MT. At the moment it keeps very very cool, as do the OPTs. The GU50's get very hot (without the plate glowing, however). Could this "cool running" mean bias is way to low at the moment (and output power)?
How often should one have a look at the bias anyway?
How often should one have a look at the bias anyway?
Hey guys, thanks to all the contributors to this thread, it has been very helpful document. But I'm shocked that in 23 pages the matter of the DAC has not received further attention.
I am about to pull the trigger on this purchase, but I can't be the only one whose primary audio source is a computer, which is why I am drawn to the Peach. It seems to do everything, DAC>tube amp>headphone amp>speaker amp. I'm hoping to use it as my complete audio control tower, handling input almost exclusively from PC and output to headphone and bookshelves.
Could someone please be kind enough to give a review of the quality of the DAC, or explain why it is of poor quality, and give an indication if the Peach is suited to my proposed setup.
Thanks in advance.
I am about to pull the trigger on this purchase, but I can't be the only one whose primary audio source is a computer, which is why I am drawn to the Peach. It seems to do everything, DAC>tube amp>headphone amp>speaker amp. I'm hoping to use it as my complete audio control tower, handling input almost exclusively from PC and output to headphone and bookshelves.
Could someone please be kind enough to give a review of the quality of the DAC, or explain why it is of poor quality, and give an indication if the Peach is suited to my proposed setup.
Thanks in advance.
Wonderful thread
Hi Guys,
Firstly a big thanx to Globulator and all the other posters who have contributed to this wonderful thread. I have had my Sweet peach a couple of years now and the socket problem has been getting slowly worse. to the point now where it is in my workshop for a serious overhaul. I have emailed the vendor for a schematic (which I have on an old PC somewhere) and will be carrying out the Mods that have been Proposed/Carried out. I must say that I have been playing my amp for a couple of years now with a lenco GL75 front end into a pair of Wharfedale E70's and everyone who has heard it said what a great sound for such a cheap amp. I cannot wait to get the benefits you guys have got from your tweaks. Once again Thanx a lot
Peter
P.S Merry Christmas
Hi Guys,
Firstly a big thanx to Globulator and all the other posters who have contributed to this wonderful thread. I have had my Sweet peach a couple of years now and the socket problem has been getting slowly worse. to the point now where it is in my workshop for a serious overhaul. I have emailed the vendor for a schematic (which I have on an old PC somewhere) and will be carrying out the Mods that have been Proposed/Carried out. I must say that I have been playing my amp for a couple of years now with a lenco GL75 front end into a pair of Wharfedale E70's and everyone who has heard it said what a great sound for such a cheap amp. I cannot wait to get the benefits you guys have got from your tweaks. Once again Thanx a lot
Peter
P.S Merry Christmas
problem with sweet peach
It's been a while since the last post here, so I hope somebody will read this. I have bought a Sweet peach FU50 last year but now have a problem with it.
The left channel does not amplify properly, but only produces a very soft sound (and a faint crackling in the speaker). However, on occassion it does start off at the normal level (ie equal to the right channel), only to fall back after a couple of minutes.
I have ruled out the speakers, input and the tubes (that is, the FU50s and 6n1's but not the 6n3) as the cause of this problem. I have also had a peak inside and did not see any obvious problems, but I do not have the proper tools to check/measure components.
Any ideas what the cause of this problem is and how to solve it?
btw I did not do any modifications on the amp.
Thanks
Jan
It's been a while since the last post here, so I hope somebody will read this. I have bought a Sweet peach FU50 last year but now have a problem with it.
The left channel does not amplify properly, but only produces a very soft sound (and a faint crackling in the speaker). However, on occassion it does start off at the normal level (ie equal to the right channel), only to fall back after a couple of minutes.
I have ruled out the speakers, input and the tubes (that is, the FU50s and 6n1's but not the 6n3) as the cause of this problem. I have also had a peak inside and did not see any obvious problems, but I do not have the proper tools to check/measure components.
Any ideas what the cause of this problem is and how to solve it?
btw I did not do any modifications on the amp.
Thanks
Jan
New peach arrived
Hi guys,
This is my first post on this board, but I've been reading along a lot here (and elsewhere) in the last few weeks, and thanks to all the great contributors here..!
I've been getting back into audio gear (and listening) again in the last months after what has almost been a hiatus in the last few years, also bought some chinese value gear to substitute my broken old stuff.
Just yesterday, a sparkling new FU-50 peach - black of course - has arrived at my desk, which I'm planning to feed from my also Xiang Sheng made DAC 01A, and running into some 4 ohm / 83 dB speakers, which is plenty loud enough for me now since there are 2 little kids around the house.
First impression is quite nice, even though a few things are bugging me a little. There's some hum, the volume pot knob is grinding a little against the front plate, and the right OPT got a knock during shipping and is now leaning a little towards the power tranny... Also, the stepped actuation of the volume pot is a pita at low playback volumes. But all in all, still nice stuff for the price i paid, and good potential for modding.
My mods will be described in following posts, some pics should be enough for now.
Cheers,
gOLDENbEER
Hi guys,
This is my first post on this board, but I've been reading along a lot here (and elsewhere) in the last few weeks, and thanks to all the great contributors here..!
I've been getting back into audio gear (and listening) again in the last months after what has almost been a hiatus in the last few years, also bought some chinese value gear to substitute my broken old stuff.
Just yesterday, a sparkling new FU-50 peach - black of course - has arrived at my desk, which I'm planning to feed from my also Xiang Sheng made DAC 01A, and running into some 4 ohm / 83 dB speakers, which is plenty loud enough for me now since there are 2 little kids around the house.
First impression is quite nice, even though a few things are bugging me a little. There's some hum, the volume pot knob is grinding a little against the front plate, and the right OPT got a knock during shipping and is now leaning a little towards the power tranny... Also, the stepped actuation of the volume pot is a pita at low playback volumes. But all in all, still nice stuff for the price i paid, and good potential for modding.
My mods will be described in following posts, some pics should be enough for now.
Cheers,
gOLDENbEER
Attachments
Ok, I started off with the essential changes which are
I am planning my next tweaks, and my approach will be KISS and not to mess with the topology for the time being if not required. Mods I was thinking about include
Last resort
- short wire the electrolytics on the volume selector input board - I did not pull them out yet due to bad accessibility. I guess it makes no difference in sound anyways.
- remove and short the small input caps on the center pre-stages board
- replace the 4 WIMAs with russian PIO K40Y-9 as coupling caps
- re-bias FU-50s for 60 ma.
I am planning my next tweaks, and my approach will be KISS and not to mess with the topology for the time being if not required. Mods I was thinking about include
- Remove cathode resistor bypass caps on 6n1 and 6n3 tubes. Thsi should clean the sound further by killing 4 electrolytics from the signal path and further linearize sound by some local degradation around the tubes. It should also reduce gain at each stage by a few dB.
- Try and remove global nfb completely. If it kills the performance, re-establish as under #3.
- Alternatively to #2, kill electrolytics from global nfb path. Do they serve any purpose anyways? Possibly further reduce nfb by increasing feedback resistors.
Last resort
4. Re-wire feedback path to include FU-50 power stage only. Any suggestions from the experts towards that?
Once again, thx for all the contributors here, will try to post some pictures from the innards later.
Some pics, first is the bridged input caps on the volume selector pcb, the others show the innards with the k40y-9 PIOs in place..
Sound is clean and nice, control of my 4 ohm Visaton Alto II's is decent at room level even with low electronic bass (Saafi Brothers
).
Sound is clean and nice, control of my 4 ohm Visaton Alto II's is decent at room level even with low electronic bass (Saafi Brothers
).Attachments
The Sweet Peach FU50 is still around, but I haven't heard much about it recently. Is this still considered a good single ended amp? I'm looking for a higher powered single-ended amp but cannot afford 300bs or 845s...this amp looked promising. I'm not a very experienced modder...is the stock sweet peach the best iteration of this tube design or is there perhaps something better?
I rather liked it TBH. Long time since I modded it though .
I'd go for it, lovely and easy to mod, and if you re-wire it as I did into a tightly coupled low impedance output tube + driver then you get lots of power and a great sound.
Even without that - with simple mods it sounds very good. The GU50 is a fantastic tube too.
My main final mod was to remove the OPT (Output Transformer) from the feedback path and instead drive it from a low impedance as per Thorsten Loesch's recommendations.
Many people love feeding back a frequency limited, phase shifted signal but just driving the OPT properly in the first place creates a much cleaner sound in my experience and this little SE amp allows these mods with ease, a PP amp has many more obstacles - twice as many components for one.
.I'd go for it, lovely and easy to mod, and if you re-wire it as I did into a tightly coupled low impedance output tube + driver then you get lots of power and a great sound.
Even without that - with simple mods it sounds very good. The GU50 is a fantastic tube too.
My main final mod was to remove the OPT (Output Transformer) from the feedback path and instead drive it from a low impedance as per Thorsten Loesch's recommendations.
Many people love feeding back a frequency limited, phase shifted signal but just driving the OPT properly in the first place creates a much cleaner sound in my experience and this little SE amp allows these mods with ease, a PP amp has many more obstacles - twice as many components for one.
Thanks for that feedback Globulator!
Do you still own and use the amp? It's been a long time since, have you perhaps something even better? I'm looking for something great that is available bone stock...since I have only soldered twice in my life
I realize this is a DIY audio forum, but most of the info regarding the FU50 amp is in this forum.
The only other option would be to buy a modded used one
Do you still own and use the amp? It's been a long time since, have you perhaps something even better? I'm looking for something great that is available bone stock...since I have only soldered twice in my life
I realize this is a DIY audio forum, but most of the info regarding the FU50 amp is in this forum.
The only other option would be to buy a modded used one
I still have it yes, and it will be back in use once the building work has finished. You can do some fairly minor mods to it to make it sound much better out of the box. The main things being the coupling capacitors.
Read the safety notes in this forum before starting.
Then practice a bit of soldering, it's fun and with the internet easy to learn.
If you want a ready modded solution look at Icon Audio etc - they sell pre-modded stuff.
Read the safety notes in this forum before starting.
Then practice a bit of soldering, it's fun and with the internet easy to learn.
If you want a ready modded solution look at Icon Audio etc - they sell pre-modded stuff.
It does need a lot of mods although not difficult ones to start sounding OK. However the stock output transformers are really budget as can be expected at this price. They will not pass low frequencies at more than a watt or so. So, seriously if you can, try to buy something which comes with better transformers. Otherwise there are some upgrade options available to suit any budget.
Hi Guys,
This is my first post on this forum. Got inspired on the FU50 after reading up on all the material. I bought one from China in disassembled condition (was hand carried by good friends in phases. Now I have put this all together and it is burning in. I face one issue - the volume is slightly more towards the right channel. Checked with swapping inputs, swapping the 6N3 tubes, Swapping the FU50 tubes, also through headphones - in all cases it seem that the right is slightly more than the left.
I dunno if this is due to bias shift in one channel or something with the volume pot. Please help.
How do I check the bias ? - on what points on the board please? Kindly explain...... and how do I adjust it ?
This is my first post on this forum. Got inspired on the FU50 after reading up on all the material. I bought one from China in disassembled condition (was hand carried by good friends in phases
. Now I have put this all together and it is burning in. I face one issue - the volume is slightly more towards the right channel. Checked with swapping inputs, swapping the 6N3 tubes, Swapping the FU50 tubes, also through headphones - in all cases it seem that the right is slightly more than the left. I dunno if this is due to bias shift in one channel or something with the volume pot. Please help.
How do I check the bias ? - on what points on the board please? Kindly explain...... and how do I adjust it ?
So now I realized I should haven't read through earlier posts for the Biasing issue. Have checked it and slightly adjusted it. However the problem remains.
Now I noticed that I was using the 4 Ohm setting since my speakers were 6 Ohm. On a hunch I switched them to 8 Ohms and..surprise the balance is perfect! I have applied a couple of drops of switch cleaning oil to the slider switch in the hope that this is a switch issue....however it has not helped....Issue still remains (left channel weaker) . Please help !
Now I noticed that I was using the 4 Ohm setting since my speakers were 6 Ohm. On a hunch I switched them to 8 Ohms and..surprise the balance is perfect! I have applied a couple of drops of switch cleaning oil to the slider switch in the hope that this is a switch issue....however it has not helped....Issue still remains (left channel weaker) . Please help !
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