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View Poll Results: Do you recommend the KT100 or FU50 version?
KT100 1 16.67%
FU50 5 83.33%
Voters: 6. You may not vote on this poll

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Old 18th February 2012, 09:08 PM   #1
morme is offline morme  United States
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Default Help choosing Sweat Peach FU50 or KT100

First time with inexpensive chinese amps. I ordered a KT100 version of the Sweat Peach amp. Of course it is out of stock and Hilly Audio recommended I get the FU50 version instead. They say they sell many more of the FU50 versions.

http://www.hllyhifi.com/tube-amplifi...amplifier.html
http://www.hllyhifi.com/tube-amplifi...amplifier.html

My intent was to replace (after a while) the tubes with good KT88 tubes. That aside, which of the 2 versions would you folks recommend? I am retired on disability and could not afford to replace my old Dynaco Stereo 70 which, like an idiot, i trashed when an output transformer blew in the late 80's or early 90's and xformers were impossible to find. I replaced it with a Hafler DH220 (another kit)

with tubes, the new Dynaco kits are about $1000 so the $320 shipped Sweet Peach seems like an inexpensive substitute for a Dynaco Stereo 35.

also, can i just drop in replace the KT100 tubes with Shuguang KT88?

Any simple mods? I know to replace the coupling caps. Can i just bypass the input caps completly like i did in my S5 K12G kit? Thanks for taking the time to read this

Last edited by morme; 18th February 2012 at 09:55 PM.
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Old 18th February 2012, 10:08 PM   #2
morme is offline morme  United States
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Default I added a poll, but I no longer see the thread question

I was hoping for help in choosing either a KT100 or FU50 version of the Sweet Peach amp. I think adding the poll may have deleted the original posting.
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Old 19th February 2012, 09:06 AM   #3
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Location: Cambridge, England.
Read these:

Sweet Peach EL34b Amp - Distortion?

Trying to make sense of the Sweet Peach

for background on these amps and how they can be modified.
I'd go for the FU50 without doubt. The FU50 tube is the chinese copy of the GU50 russian tube, which is plentiful, cheap and _extremely_ good quality both audio-wise and construction and power wise.

I'd choose the GU50 over all the KT series for that reason, and in fact have for my latest amp project which is also GU50. My modified Sweet Peach GU50 is in my living room for regular use duty now

GU50s rock, just ask Wavebourn - one of the most experienced tube designers here - they really are fantastic audio tubes.
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Old 19th February 2012, 04:05 PM   #4
morme is offline morme  United States
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I understand that the output transformers are so-so. Any recommendations on good but budget replacements? How about the Dynaco ST-35 xformers?

I just emailed Hlly to send the FU50 model. Can I use a Russian GU 50?

Thanks

Quote:
Originally Posted by Globulator View Post
Read these:

Sweet Peach EL34b Amp - Distortion?

Trying to make sense of the Sweet Peach

for background on these amps and how they can be modified.
I'd go for the FU50 without doubt. The FU50 tube is the chinese copy of the GU50 russian tube, which is plentiful, cheap and _extremely_ good quality both audio-wise and construction and power wise.

I'd choose the GU50 over all the KT series for that reason, and in fact have for my latest amp project which is also GU50. My modified Sweet Peach GU50 is in my living room for regular use duty now

GU50s rock, just ask Wavebourn - one of the most experienced tube designers here - they really are fantastic audio tubes.
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Old 19th February 2012, 05:40 PM   #5
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Quote:
Originally Posted by morme View Post
I understand that the output transformers are so-so. Any recommendations on good but budget replacements? How about the Dynaco ST-35 xformers?

I just emailed Hlly to send the FU50 model. Can I use a Russian GU 50?

Thanks
The russian GU50 tubes just plug straight in, remember to bias them to 50mA for best results. The output transformers on my Peach FU50 are fine, can't criticise them at all, they sound wonderful. My circuit is different to your though.

BTW you cannot use push-pull transformers in an SE design anyway, because the constant DC magnetic field upsets them. SE transformers are gapped to avoid this issue + they are actually bigger for the same power output IME.
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Old 24th April 2012, 08:07 PM   #6
frapa02 is offline frapa02  United Kingdom
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The output transformers definitely compromise the Peach but I would not complain for the price since with feedback the limitations are somewhat compensated for. Please check the comments on the other threads, there is also an update there from a chap XavLNK who thoroughly bench tested the Peach. (see the 'Trying to make sense' thread)

I agree, you get a 'good' sound but bench testing reveals the transformers limited performance at low frequencies and open loop distortion across the board. You will get thicker and louder bass from this but it is not obvious that there is a problem, partly due to the NFB and the positive effect of the changed sound. The transformers in mine have a low primary inductance.

Regarding a suitable budget output transformer upgrade, I don't think there is such a thing, budget and upgrade do not go together! A significant upgrade would require spending upwards of 75 - 100 each (GBP) on a a quality SE transformer. You would need around 3 - 3.5k primary and with a decent bandwidth at the desired output power.

I agree the GU50 is probably the best one to go for but the advantage with the KT88 / KT100 / EL34B is that you can try different valves in there.

Finally, there is no confirmation that we all have the same transformers as we can't see them.
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