Since I revamped the old Cary SLM-100 using KT88 (variable bias, input circuit, new powerful transformer for KT120 heaters, Triode switch) and replaced only the output tubes with new KT120 (matched & cyro treated) ...
The posive: more power comes up, output noise very very quiet, no more noise jumps 😀
The negative: Dully sound, this means the airy sound as with the EH KT88 is gone 😡
So the question comes up, before go back to EH KT88 or even better sounding KT88 (Golden Lion went after short test to ^^^^)...
So it is an investment to get the sound back .. . but currently with unknown tubes...
Or there is a little help to get the sound of the KT120 out of the gear...
BTW: Using Magnepan 3.6 speakers with nice sound age
The posive: more power comes up, output noise very very quiet, no more noise jumps 😀
The negative: Dully sound, this means the airy sound as with the EH KT88 is gone 😡
So the question comes up, before go back to EH KT88 or even better sounding KT88 (Golden Lion went after short test to ^^^^)...
So it is an investment to get the sound back .. . but currently with unknown tubes...
Or there is a little help to get the sound of the KT120 out of the gear...
BTW: Using Magnepan 3.6 speakers with nice sound age
It could be the more powerful bass has upset the balance you are hearing after using KT88,s which I like but I take it the frequency response is flat in the amp but obviously not subjectively from the speakers ?
What does it sound like with your new components and the original KT88,s plugged in ?
What does it sound like with your new components and the original KT88,s plugged in ?
Look, it did the revamp in various steps... while it are mono amps with 2 x 4 KT 88 form the early days, so it is more like the latest model 😀 Original input tubes are Silvana as mentioned the 4 x EH KT88 for each mono block
. Input & Driver part
. Input direct connected near the input stage & front (long cable to back gone)
. Standby cable to the front replaced with a relays switch at the stacked power caps
. Bias as 2 x for each dual connected PP KT88, this means 2 x 0.47 uF 630V, so required 4 new power resistor for the cathode
. Anode mode switching
than experimented as PNP with the input tubes
. original 6SN7 Silvana as good
. purchase Golden EH 6SN7, sound was to harsh and not please
. RCA bingo more clear & air sound stage
So with this setup I had a width & deep sound age I liked. Knowing I had to replace one day the KT88 (about 15 years old) as the 4 x 470uF 500V caps.
So one day the KT88 had distorted sound, so had to find new one.
So I ordered the early bird Golden Lyon KT88, but soon after short usage, the cathode resistor smocked and one Lyon had a grid cathode shortage.
So new plan, KT120 with promised more power, but required more heating currents, I ordered 2 special build trani to heat the Kt120.
So I ordered cyro tried 2 x 4 KT120, the promised lower noise was measurable
compared to the old EH KT88 ...
The sound age as in question with the old EH KT88:
The width open recorded sound age as you listen to Muddy Water's Folk Singer (as he really sings from the middle of the speakers) or Classic music where the singing body and the ssshh is coming from the equal position as the singing...
So before I invest in any new xxx buckets, last chance to get may some advice for the KT120...
With tubes it is like PNP like = the yellow on the egg / or waste basket
Hp
Do you understand why I asked you to try the KT88,s with your NEW output transformers ?
You say it sounded sweet with KT88,s BEFORE you changed things but is dull now with the changes , don't you see I am trying to check whether it sounds better or worse with them in it.
Of course the cathode resistor will be a different value but you only need to turn it up a little bit to check if it sounds better or not.
Its a matter of elimination .
You say it sounded sweet with KT88,s BEFORE you changed things but is dull now with the changes , don't you see I am trying to check whether it sounds better or worse with them in it.
Of course the cathode resistor will be a different value but you only need to turn it up a little bit to check if it sounds better or not.
Its a matter of elimination .
Always modify 1 thing at a time, not 2 or more things at a time.
Then check the result of the 1 modification.
Man with 1 Watch knows the time.
Man with 2 Watches is never sure.
Then check the result of the 1 modification.
Man with 1 Watch knows the time.
Man with 2 Watches is never sure.
Well,
may the message went NOT clearly trough ....
1. Revamped the amp to better using the EH KT88, as exchanged with new power trani, in mind for later powerful KT120 exchange ...
2. KT88 they went chrismas
3. So I put in the KT120 in
4. now the stinking fish
5. So, order new KT88 = xxx task
6. Or someone has some golden idea's 😀
Hp
You had a KT88 which started to produce distorted sound, then you fitted new golden lion KT88’s, and one of these failed. Could there be a connection? What operating point do you have?
Run the kt88 at about 45mA... kt120 about 50mA...
The first reissued golden lion's were known of failures.
Only one thing matches, the rising upper sound with the golden EH 6SN7 as could be with the now required EH KT88...
Hp
The first reissued golden lion's were known of failures.
Only one thing matches, the rising upper sound with the golden EH 6SN7 as could be with the now required EH KT88...
Hp
What is the DC plate voltage on the KT88?
What is the DC screen voltage on the KT88?
Beam Power mode, or UL mode?
KT88 with Fixed Adjustable Bias, or Self Bias?
What is the DC resistance from the KT88 g1 to ground?
Is there RC coupling from the driver plate to the KT88 g1?
Any chance that the cap is leaky?
You changed the output transformers from one model to another model.
Could that have disturbed Global Negative Feedback?
I do not have access to the complete schematic, so I ask too many questions.
Just asking.
What is the DC screen voltage on the KT88?
Beam Power mode, or UL mode?
KT88 with Fixed Adjustable Bias, or Self Bias?
What is the DC resistance from the KT88 g1 to ground?
Is there RC coupling from the driver plate to the KT88 g1?
Any chance that the cap is leaky?
You changed the output transformers from one model to another model.
Could that have disturbed Global Negative Feedback?
I do not have access to the complete schematic, so I ask too many questions.
Just asking.
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~Inspect & Repair~ Cary SLM-100 Tube Monoblock Amplifier - YouTube
There is a schematic in the above clip, but it's too blur, and not much data. Maybe OP will fill up the actual value of the components and operating points? So sim can be updated and for KT120 can be done as well.
Cary Audio Design SLM-100 monoblock power amplifier Measurements | Stereophile.com
According to the above measurement output Z is high it's selective on the speaker used.
There is a schematic in the above clip, but it's too blur, and not much data. Maybe OP will fill up the actual value of the components and operating points? So sim can be updated and for KT120 can be done as well.
Cary Audio Design SLM-100 monoblock power amplifier Measurements | Stereophile.com
According to the above measurement output Z is high it's selective on the speaker used.
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Thank you for your given feedback! Your LTSpice is very close to me current implementation. So simulation should show what's going on with KT88, KT90 & KT120. Like the shown freq. response as given from Stereophile.
May we deal with a different output trani brands. How knows!!??
Keep in mind, Cary modified the circuit may times (input & triode mode support..). My origin mono block's had a pot with phase inversion 😱 For me, it was easier to revamp than build all from scratch.
Also thinking that each power tube should have it's own C-R driven from the driver tube. So in case of gate / cathode shortage (as I had it with the Golden Lion), full disaster may not happen.
My power is about 530V... but do not overdrive with high current as 45..50mA
BTW: is your given LTSpice somewhere public.
May we deal with a different output trani brands. How knows!!??
Keep in mind, Cary modified the circuit may times (input & triode mode support..). My origin mono block's had a pot with phase inversion 😱 For me, it was easier to revamp than build all from scratch.
Also thinking that each power tube should have it's own C-R driven from the driver tube. So in case of gate / cathode shortage (as I had it with the Golden Lion), full disaster may not happen.
My power is about 530V... but do not overdrive with high current as 45..50mA
BTW: is your given LTSpice somewhere public.
Here is LTSpice simulation for SLM-100 I share with you all. It would be closer if you also measure the actual data for the OT all the inductances and DCR. Here is an inductance/capacitance meter I bought recently, very handy and precise:
https://shopee.com.my/HANHAN-Induct...ectric-ABS-LCR-LC‑200A-i.269998608.7856276359
Also attached is model for KT120. You can download LTSpice here:
LTspice | Design Center | Analog Devices
https://shopee.com.my/HANHAN-Induct...ectric-ABS-LCR-LC‑200A-i.269998608.7856276359
Also attached is model for KT120. You can download LTSpice here:
LTspice | Design Center | Analog Devices
Attachments
Thank you very much 😎
Did you get the same freq. response figures as show at Stereophile.
And about your output trani data?? Are they measured from a real SLM-100?
Keep in mind on simulations, dual triodes tube has no option on cross talk, so best would be always to use the in parallel 😀 As turner used them to drive the power tubes.
About my still opened KT120 issue :
a) the SLM-100 circuit is now made to use them. But I have seen 4x KT-150 tubes amps..
b) the cryogenically treated killed the sound
c) the buffer driver needs some additional power to drive them
d) read on KT150 v KT120 Tubes | What's Best Audio and Video Forum. The Best High End Audio Forum on the planet!
e) read on KT120 back to 6550 | Audiogon Discussion Forum
hp
No it's not actual slm-100 OT, but it's a 4k Raa, the inductance is that of toroidal output transformer. I believe the actual inductance is lower. For KT88, 6500, EL34 4K OT is for PP and output 75W or so but compared to PPP (100W or more) it's output impedance is almost twice as high (7.8/4.2 Ohms) in same schematic. For KT120 it will need 2K Raa to output more than 100W, but the output Z is also higher if you want more power. The sim result output Z of about 4.2 Ohms is close to 5.5 Ohms of the report, so I believe 4K Raa is about right for KT88, 6550 EL34. You can use the same OT with CF winding to lower again the output Z. Or increase the GNFB. I have built 6p3p PPP only 50W, sound very detail and sharp in pentode mode, although output Z is more 10 Ohms, but if increase NFB, it sounds duller or less detail. I use IT driver so I can not apply too much NFB. Each output tube has separate bias adj and RC coupling.
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A few snapshots, hope it'll help you to tailor your amp esp for KT120 and to verify the model accuracy. I can sim KT150 if you want. I use an older KT120 model in the previous post, this one is more accurate (g1, g2 and anode current) and same the .inc I posted earlier.
