Re: G9 and its frequency response ?? (impedance matching?)
« Reply #280 on: November 06, 2016, 07:28:06 AM »
This shows the Sowter with vintage tube (1963 Mullard CV4003 to be precise, but from my tests pretty much any old make is similar and pretty different from the new JJ)  followed by 5402 with JJ and then 5402 with vintage.  With the worse 5402, the JJ would draw pretty much the same third/low line and with vintage it would be an additional -0.5-7db at 50Hz.     


andow

Re: G9 and its frequency response ?? (impedance matching?)
« Reply #281 on: January 26, 2018, 08:04:30 AM »
I'm also thinking about experimenting with different output transformers as I experience a slight bass roll off from 700Hz with LL5402.
Do you think wiring the LL5402 as 4:1 would flatten this frequency response? (Of course at the expense of gain but that's not a problem for me...)

andow

Re: G9 and its frequency response ?? (impedance matching?)
« Reply #282 on: February 02, 2018, 05:28:45 PM »
I'm also thinking about experimenting with different output transformers as I experience a slight bass roll off from 700Hz with LL5402.
Do you think wiring the LL5402 as 4:1 would flatten this frequency response? (Of course at the expense of gain but that's not a problem for me...)

Bump....

gyraf

Re: G9 and its frequency response ?? (impedance matching?)
« Reply #283 on: February 05, 2018, 06:07:36 AM »
I think you need to do some experimenting on your own.

Read through this thread - it shows that there are more parameters in play than what meets the eye..

Jakob E.
..note to self: don't let Harman run your company..

noulou

Re: G9 and its frequency response ?? (impedance matching?)
« Reply #284 on: February 05, 2018, 06:52:31 AM »
Substituting a 12bh7 as the output tube did wonderful things to my G9.  ;) ;)

audiophreak

Re: G9 and its frequency response ?? (impedance matching?)
« Reply #285 on: February 05, 2018, 08:01:10 AM »
Substituting a 12bh7 as the output tube did wonderful things to my G9.  ;) ;)

 verryyyy Interesting ... I just happen to have a few of those and a couple of G9's  ... would the plate resistor or anything else need to be changed or is it just a strait substitution ?

 Note :   I dont have any low end loss and really like the sound of the G9 ... but I do like messing about and trying stuff too , after all ... this is DIY     ;D


" Music washes away from the soul, the dust of everyday life "   ... in loving memory of my Father.

noulou

Re: G9 and its frequency response ?? (impedance matching?)
« Reply #286 on: February 06, 2018, 04:55:15 AM »
just plug it in. make sure the heater voltage regulator gets enough cooling.

this is with a lundahl output transformer. With the oep the bottom end was fine, but the sound of the oeps is not to my taste at all.

try experimenting with input transformers also.

It was only until i installed some old bbc transformers that the unit came alive for me.
Now its my favourite preamp.  Up until these changes I hardly ever used it.

audiophreak

Re: G9 and its frequency response ?? (impedance matching?)
« Reply #287 on: February 06, 2018, 08:48:05 AM »
just plug it in. make sure the heater voltage regulator gets enough cooling.

Great !!!   

this is with a lundahl output transformer. With the oep the bottom end was fine, but the sound of the oeps is not to my taste at all.

Lundahl is what I have , feel the same on the oeps.

  Thanks so much !!!    :)
" Music washes away from the soul, the dust of everyday life "   ... in loving memory of my Father.

andow

Re: G9 and its frequency response ?? (impedance matching?)
« Reply #288 on: February 06, 2018, 05:08:26 PM »
I think you need to do some experimenting on your own.

Read through this thread - it shows that there are more parameters in play than what meets the eye..

Jakob E.

I read every single post in this thread, but it seems nobody tried the stock Lundahl in 4:1... But yeah, I will.  ;)

Btw: I really love the sound of the G9 and I think it's frequency response is ok as a preamp. But I'd love to use it more on line level signals, maybe even for mastering and of course I'd prefer a flat response for that...

Substituting a 12bh7 as the output tube did wonderful things to my G9.  ;) ;)

Cool, thanks for the suggestion! Are you using a 78S12 for heater voltage regulation? May I ask how big your heatsink is?  :o

noulou

Re: G9 and its frequency response ?? (impedance matching?)
« Reply #289 on: February 07, 2018, 03:11:33 AM »

Cool, thanks for the suggestion! Are you using a 78S12 for heater voltage regulation? May I ask how big your heatsink is?  :o

78s12 yes. I've bolted it to the preamps (steel) case. It's been regulating fine, never shut down.



Nyquist

Re: G9 and its frequency response ?? (impedance matching?)
« Reply #290 on: July 08, 2018, 04:13:30 AM »
Hey there. I finished my G9 recently and I noticed a the roll off of low frequencies as mentioned in this post. While I noticed it straight away the pre does sound very good indeed and is super quiet. Thanks to Jacob for the open release.  :)

My config is standard(apart from PSU being relocated off the main board)  with Lundahl input and output transformers.

After reading through this thread it is my understanding the 6198 tube has  impedance trouble in conjunction with the Lundahl  5402 transformer.

I have a spare 12BH7A in my spares box so I gave it a try. I put it in place of a 6189W in channel 2 output position.

First observation a after 20 min warm up was indeed the frequency roll off was less pronounced. Comparing with channel 1 (still 6189W's throughout) yes channel 2 had more low end, however channel 1 with the 6189W's did sound better overall. The sonic character was much rounder, almost 3D in a way. Channel 2 seemed a bit stale and dull with the 12BH7A in place.

I must admit the 6189w's are NOS JAN tubes and are of high quality. The 12BH7A i used is a cheap Russia recent tube. I have ordered a pair of NOS 1950's RCA 12BH7A just cause. If I don't use them in the G9 they'll go into my LA2A's

I did a quick sweep for reference. The sweep is of the same channel, same settings, same warm up time etc. I'll write another post back here once the vintage tubes show up.



Nyquist

Re: G9 and its frequency response ?? (impedance matching?)
« Reply #291 on: July 19, 2018, 08:12:18 AM »
Hey guys following on from my previous post the NOS 12bh7 tubes arrived and I swapped one in. After burn in I did another comparison between a channel loaded with 6189w's. The new 12bh7 tube made the pre come alive. the channel sound every bit as good as the 6189w channel only, obviously a fuller sound due to the frequency response. I'll spend some time recording the same sources on each channel over the next couple of projects and I'll see what flavor I like the most. 

Note in both configurations the pre's sound great in my opinion it comes down to personal preference.


 

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